U.S. patent application number 13/060196 was filed with the patent office on 2011-12-22 for tau protease compositions and methods.
This patent application is currently assigned to Oligomerix Inc.. Invention is credited to Eliot J. Davidowitz, James G. Moe.
Application Number | 20110312059 13/060196 |
Document ID | / |
Family ID | 41707606 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110312059 |
Kind Code |
A1 |
Moe; James G. ; et
al. |
December 22, 2011 |
TAU PROTEASE COMPOSITIONS AND METHODS
Abstract
Tau protein has a causative role in Alzheimer's disease and
multiple other neurodegenerative disorders exhibiting tau
histopathology collectively termed tauopathies. The primary
function of tau protein is to facilitate assembly and maintenance
of microtubules in neuronal axons. In the disease process tau
protein becomes modified, loses its affinity to microtubules and
accumulates in the cell body where it forms aggregates. The large
neurofibrillary tangles formed from tau protein assembled into
filaments were thought to be the pathological structure of tau.
However, more recent work indicates that smaller, soluble
oligomeric forms of tau are best associated with neuron loss and
memory impairment. A novel and unexpected protease activity has
been discovered to be associated with tau in oligomeric but not
monomeric structures. Methods have been developed to form and
purify tau protease and to assay its activity. Tau protease
activity constitutes a totally novel mechanism for tau-mediated
neurodegenerative disease by causing tau loss of function, as it
cleaves itself, and gain of toxic function as it can cleave other
proteins and facilitate cell death through apoptotic and/or
senescence pathways. Tau protease presents a novel and unique
target for the development of therapeutics that may be achieved by
several strategies including by inhibiting the tau oligomer
enzymatic activity.
Inventors: |
Moe; James G.; (Stanford,
CT) ; Davidowitz; Eliot J.; (West Hempstead,
NY) |
Assignee: |
Oligomerix Inc.
New York
NY
|
Family ID: |
41707606 |
Appl. No.: |
13/060196 |
Filed: |
August 20, 2009 |
PCT Filed: |
August 20, 2009 |
PCT NO: |
PCT/US09/04796 |
371 Date: |
September 9, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61189679 |
Aug 20, 2008 |
|
|
|
Current U.S.
Class: |
435/226 ;
530/300; 530/350 |
Current CPC
Class: |
C07K 14/47 20130101;
C12N 9/6421 20130101; A61K 38/1709 20130101 |
Class at
Publication: |
435/226 ;
530/350; 530/300 |
International
Class: |
C12N 9/64 20060101
C12N009/64; C07K 2/00 20060101 C07K002/00; C07K 19/00 20060101
C07K019/00 |
Claims
1. A tau protease associated with AD.
2. (canceled)
3. A protease inhibitor that inhibits or blocks tau protease
activity.
4. A protease inhibitor of claim 3, wherein the protease inhibitor
is a cysteine protease inhibitor.
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. A composition comprising tau oligomer having a staggered
alignment comprising one or two free thiol moieties from a cysteine
amino acid of the tau oligomer, wherein the tau oligomer comprises
3R or 4R isoforms of tau monomer.
13. (canceled)
14. A composition comprising tau protease, wherein the tau oligomer
protease is a cysteine protease.
15. A composition according to claim 14, wherein the cysteine
protease is adapted for screening drug compounds that enhance or
inhibit the tau oligomer proteolytic activity, wherein the tau
monomeric unit comprises SEQ ID NO. 1-6. or derivatives.
16. A composition according to claim 15, wherein the cysteine
protease is inhibited by a cysteine protease inhibitor that blocks
or prevents its activity and is useful in treating tauopathies or
Alzheimer's disease.
17. A composition according to claim 15, wherein the tau oligomer
protease cleaves tau oligomer to form tau cleavage products and the
tau cleavage products function as biomarkers for tauopathies or
Alzheimer's disease.
18. A composition according to claim 17, wherein the cysteine
protease comprises 4R tau oligomer, 4R and 3R tau oligomer or a
combination thereof.
19. A composition comprising extracellular tau oligomer protease,
wherein the extracellular tau oligomer protease is a target for
immunotherapy.
20. (canceled)
21. (canceled)
22. A cleavage product of tau protein, wherein the cleavage product
is formed from tau protease and the cleavage product comprises
fragments of tau oligomer, and the tau oligomer is in at least one
conformation comprising tau dimer, tau trimer, tau tetramer, tau
pentamer, tau hexamer, tau septamer, tau octamer, tau nonamer, tau
decamer, tau unadecamer, tau dodecamer, 3R tau, 4R tau, or mixtures
of 3R tau and 4R tau or a combination thereof.
23. (canceled)
24. (canceled)
25. (canceled)
26. (canceled)
27. (canceled)
28. (canceled)
29. (canceled)
30. (canceled)
31. (canceled)
32. (canceled)
33. (canceled)
Description
[0001] This application claims the benefit of the filing date of
U.S. Provisional Application No. 61/189,679, filed Aug. 20, 2008,
entitled "Methods And Composition Comprising Tau Oligomers." The
entire disclosure is hereby incorporated by reference into the
present disclosure.
BACKGROUND
[0002] Alzheimer's disease (AD) is the most common cause of
dementia in the elderly that affects an estimated 15 million people
worldwide and 40% of the population above 85 years. The disease is
characterized by progressive loss of memory, speech and movement
with a total incapacitation of the patient and eventually death. AD
takes a terrible toll on those with the disease as well as their
families, friends and caregivers.
[0003] The symptoms of AD manifest slowly and the first symptom may
only be mild forgetfulness. In this stage, individuals may forget
recent events, activities, the names of familiar people or things
and may not be able to solve simple math problems. As the disease
progresses into moderate stages of AD, symptoms are more easily
noticed and become serious enough to cause people with AD or their
family members to seek medical help. Moderate-stage symptoms of AD
include forgetting how to do simple tasks such as grooming, and
problems develop with speaking, understanding, reading, or writing.
Severe stage AD patients may become anxious or aggressive, may
wander away from home and ultimately need total care.
[0004] No cure is currently available for AD. Today, medication
therapy focuses on controlling the symptoms of AD and its various
stages. For example, mild to moderate AD can involve treatment with
cholinesterase inhibitors such as Cognex.RTM. (tacrine),
Aricept.RTM. (donepezil), Exelon.RTM. (rivastigmine), or
Razadyne.RTM. (galantamine). Whereas moderate to severe AD can be
treated with Namenda.RTM. (memantine). These medications may help
delay or prevent AD symptoms from becoming worse for a limited
period of time. So early AD treatment is warranted. However, there
is no clear evidence that these medications have any effect on the
underlying progression of the disease.
[0005] There is a large and rapidly growing unmet need for disease
modifying drugs for Alzheimer's disease (AD). The classical
hallmarks of AD are inter-neuronal plaques consisting of
precipitates or aggregates of amyloid beta protein (A.beta.), and
intra-neuronal neurofibrillary tangles (NFTs) of tau protein. Tau
protein promotes microtubule assembly and stability and is critical
for the function of axons, whereas the normal function of A.beta.
is not fully understood. The amyloid cascade hypothesis has been
widely accepted as the pathological pathway of AD. It holds that
the generation of A.beta. and accumulation of A.beta. aggregates in
the brain initiate the disease process. It is supported by genetic
evidence that mutations leading to increased accumulation of
A.beta. aggregates leads to familial AD. However, there are a
number of weaknesses in the A.beta. cascade hypothesis in that it
does not address the importance of other pathways that can cause
neurodegeneration (Seabrook et al. 2007). The accumulation and
distribution of NFTs in the brains of AD patients is highly
correlated with disease progression and can be used to stage AD by
post-mortem brain histopathology, whereas there is poor correlation
between AD and the accumulation of neuritic plaques composed of
beta amyloid. This has been used to challenge the amyloid
hypothesis (Josephs et al. 2008). Lackluster results for A.beta.
directed therapeutics in late stage clinical trials has increased
interest in exploring alternative targets for drug discovery such
as tau (Iqbal et al. 2009).
[0006] While extensive research in the past decade has identified
possible biomarkers for AD, there is still an urgent need for
composition and methods that are specifically useful in diagnosing,
stratifying, or monitoring the progression or regression of AD. New
compositions and methods are also needed that serve as drug targets
for the identification of new medication therapies to treat AD and
to monitor different medications therapeutic effect when used to
treat AD, as well as compositions that are useful as
immunotherapeutic agents.
SUMMARY
[0007] The present application provides methods and compositions
comprising tau protease. These tau proteases, in some embodiments,
can be a cysteine protease, which can cleave tau resulting in tau
fragments or peptide fragments that can be used in diagnostic and
prognostic assays, allowing AD to be diagnosed earlier (while the
patient is alive) and more accurately than was previously possible.
These tau fragments can better help the clinician stratify, or
monitor the progression or regression of AD, than currently
available assays. In addition, tau proteases identified according
to the composition and methods disclosed can serve as drug targets
for the identification of new therapeutic agents for the treatment
of AD or other tauopathies and allow monitoring of different
medication therapies benefit when used to treat AD or other
tauopathies. In some embodiments, these tau oligomers, fragments or
tau proteases can be used as immunotherapeutic agents to stimulate
the immune system.
[0008] In some embodiments, the tau itself acquires proteolytic
activity (autoproteolytic activity) that leads to its own
fragmentation. This activity accounts for the tau protease
activities. The structure of the autoproteolytic dimer and trimer
of tau comprises 4R tau with one or two free thiols indicates that
it is a cysteine protease. In context of the disease process, tau
self-association leads to formation of autoproteolytic oligomers
that cause loss of tau function through fragmentation of the
protein and at the same time facilitate aggregation of the cleaved
microtubule binding domain into toxic structures.
[0009] In some embodiments, the tau protease is an enzyme for drug
discovery and to reduce, prevent or reverse Alzheimer's disease.
Blocking this tau protease enzymatic function may halt or reverse
AD. In some embodiments, the substrates or breakdown products for
the tau protease (i.e. the 17 kDa fragment) can be used as
biomarkers for disease progression because they are directly
proportional to the tau protease enzymatic activity.
[0010] In one embodiment, there is a tau protease associated with
AD.
[0011] In another embodiment, there is a tau protease, wherein the
tau protease is a cysteine protease.
[0012] In another embodiment, there is a protease inhibitor that
inhibits or blocks tau protease activity.
[0013] In some embodiments, a method is provided for screening an
agent for modulation or disruption of purified tau dimer, tau
trimer, tau tetramer, tau pentamer, tau hexamer or a combination
thereof, the method comprising: a) contacting a sample containing
tau dimer, tau trimer, tau tetramer, tau pentamer, tau hexamer or a
combination thereof with an agent suspected of being capable of
modulating tau oligomer formation or disrupting tau oligomers; and
b) detecting the amount of tau dimer, tau trimer, tau tetramer, tau
pentamer, tau hexamer or a combination thereof, wherein a decrease
in tau dimer, tau trimer, tau tetramer, tau pentamer, tau hexamer
or a combination thereof indicates that the agent modulates tau
oligomer formation or disrupts tau oligomer.
[0014] In some embodiments, a reagent composition is provided used
to perform high resolution NMR, X-ray crystallography, generating
antibodies to specific oligomer sizes, or for immunotherapy.
[0015] Additional features and advantages of various embodiments
will be set forth in part in the description that follows, and in
part will be apparent from the description, or may be learned by
practice of various embodiments. The objectives and other
advantages of various embodiments will be realized and attained by
means of the elements and combinations particularly pointed out in
the description and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In part, other aspects, features, benefits and advantages of
the embodiments will be apparent with regard to the following
description, appended claims and accompanying drawings where:
[0017] FIG. 1 illustrates the six tau protein isoforms that result
from alternate splicing with the N-terminal inserts in the acidic
domain (E2 and E3), the repeat domains of the microtubule binding
region (R1, R2, R3 and R4) and the tau pseudo repeat (R')
indicated. Note that there are three tau protein isoforms with
three repeats (tau352, tau381 and tau410 only contain repeats R1,
R3 and R4) and three tau protein isoforms with four repeats
(tau383, tau412 and tau441) in the microtubule binding domain (R1,
R2, R3 and R4).
[0018] FIG. 2 illustrates tau441 structural features including the
projection domain (N-terminal), the proline rich region, and
assembly domain (C-terminal). Also indicated is the beta-sheet
forming regions (PHF6* and PHF6) and the two cysteines (Cys291 in
R2 and Cys322 in R3). All 4R tau protein isoforms contain four
repeat regions as shown (R1, R2, R3 and R4), whereas 3R tau protein
isoforms only contain three repeat regions (R1, R3 and R4).
[0019] FIG. 3 illustrates microtubule binding domain structural
features through the repeat and pseudo repeat regions. The amino
acid charge is indicated above the amino acid abbreviation. The
beta-sheet forming regions and cysteines are highlighted in bold.
Potential proline or glycine mediated bending regions are
underlined. The microtubule binding regions are defined as follows:
R1=Q244 to K274; R2=V275 to S305; R3=V306 to Q336; R4=V337 to N368;
and R'=K369 to S400. In 3R tau isoforms, R2 is absent.
[0020] FIG. 4 illustrates intrinsic differences in tau isoform
oligomerization that provides the basis for the disulfide mediated
tau oligomer model. 3R tau can only form dimers and has a single
cysteine (Cys322); whereas 4R tau forms n+1 oligomers without
termination and has two cysteines (Cys291 and Cys322). Oxidative
conditions caused rapid oligomer formation due to oxidation of free
thiols in monomeric tau.
[0021] FIG. 5 illustrates the tau oligomers formed using various
ratios of 3R to 4R tau protein isoforms during reaction. The
accumulation of higher order aggregates indicates that the dimer is
reactive consistent with the formation of only a single disulfide
in the initial 4R/4R structure. Incorporation of 3R tau limits
oligomer extension. Higher order oligomers formed with increased
levels of 4R tau. The table shows the calculated and apparent
molecular weight for the 3R/3R 4R/4R and 3R and 4R tau oligomers
formed.
[0022] FIG. 6 illustrates that tau oligomers can be purified in
stable form as shown for a mixture of tau412 oligomers that was
purified. To prepare specific tau oligomers at high purification
Tau412 oligomer enriched preparations (lane 2) were
size-fractionated to isolate monomer (lane 3), dimer (lane 4),
trimer (lane 5) and tetramer (lane 6) and stabilized in buffer.
[0023] FIG. 7 illustrates two potential cut sites in the tau
monomer for cutting at the N-terminal at position Gly 164, and
cutting at the C-terminal at position Gly302. The model contains
the active site residues important for either a R2 or R3 protease
(Cys291, and Cys322 or His299 or His329/330) together with the
target amino acid which makes up the catalytic triad of the tau
oligomer cysteine protease, as well as important residues that may
stabilize the substrate and or facilitate its interaction with the
thiol group including Lys163, Lys298, and in the case of C-terminal
cleavage, His299.
[0024] FIG. 8 illustrates a PAGE analysis of the purified, inactive
tau monomer, the purified tau dimer protease, and the purified tau
trimer protease showing the cleavage products that result in a 28
kDa and a 14 kDa fragment.
[0025] FIG. 9 illustrates analysis of the C-terminal fragment for
expected MW and charge for tau412 and tau441 which shows that the
tau oligomer protease results in a 17 kDa fragment for cleavage of
the tau441 consistent with the fragment size consistently observed
in Alzheimer's disease as a tau breakdown product.
[0026] FIG. 10 illustrates the comparison of the tau oligomer
protease with other known cysteine proteases that indicates that it
is a papain-like cysteine endoprotease (CAT B-like).
[0027] FIG. 11 illustrates schematic of the tau oligomer protease
dimer showing the two active site regions and the catalytic triad
(grey triangle) for the R2 active site and the R3 active site.
[0028] FIG. 12 illustrates a proposed mechanism for the tau
oligomer cysteine protease.
[0029] FIG. 13 illustrates the model of a disulfide mediated
structure for a 3R/3R tau dimer showing alignment of the peptides
in parallel to form a beta sheet structure.
[0030] FIG. 14 illustrates the model of a disulfide mediated
structure for a 4R/4R tau dimer showing alignment of the peptides
in parallel to form a beta sheet. The formation of an
intermolecular disulfide linkage traps the tau proteins into an
aggregation template that contains two reactive free thiol
groups.
[0031] FIG. 15 illustrates the model of a disulfide mediated
structure for a 4R/4R/3R tau trimer showing alignment of the
peptides in parallel to form a beta sheet. The reaction of 3R tau
protein to the 4R/4R tau dimer eliminates occurs via additional
formation of a disulfide linkage. This results in the case of the
4R/4R/3R tau trimer with a single remaining reactive free thiol
group. At this time, there is no way to predict whether the
disulfide is between 3R R3 and 4R R2 or 4R R3. The trimer is shown
with the disulfide linkage to 4R R3 strictly for illustrative
purposes.
[0032] FIG. 16 illustrates the model of a disulfide mediated
structure for a 3R/4R/4R/3R tau tetramer, showing alignment of the
peptides in parallel to form an additional beta sheet structure.
The 3R/4R/4R/3R tau tetramer contains no reactive free thiol groups
and cannot propagate disulfide mediated tau oligomers.
[0033] FIG. 17 illustrates that disulfide-linked tau oligomers are
present in the cerebrospinal fluid (CSF) of AD patients
illustrating the biological relevance of extracellular tau cysteine
protease and highlight its importance in Alzheimer's disease. It
should be noted that the 17 kDa tau breakdown fragment observed is
consistent with the fragment produced from tau441 from the tau
oligomer protease autocatalytic activity. It should be further
noted that the extracellular location of tau oligomer protease puts
the enzyme in a position to cleave APP and may tie tau and A-beta
pathologies together.
[0034] FIG. 18 illustrates that tau in CSF is "reactive" in that it
contains reactive thiols and forms higher order aggregates if
accelerated by temperature elevation as shown in the left panel.
The panel on the right shows the higher order aggregates that are
stable to reducing conditions, SDS, and heat potentially due to
interaction with the 28 kDa polyanionic N-terminal fragment of tau
after it is cleaved.
[0035] It is to be understood that the figures are not drawn to
scale. Further, the relation between objects in a figure may not be
to scale, and may in fact have a reverse relationship as to size.
The figures are intended to bring understanding and clarity to the
structure of each object shown, and thus, some features may be
exaggerated in order to illustrate a specific feature of a
structure.
DETAILED DESCRIPTION
[0036] For the purposes of this specification and appended claims,
unless otherwise indicated, all numbers expressing quantities of
ingredients, percentages or proportions of materials, reaction
conditions, and other numerical values used in the specification
and claims, are to be understood as being modified in all instances
by the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that may vary depending upon
the desired properties sought to be obtained by the present
invention. At the very least, and not as an attempt to limit the
application of the doctrine of equivalents to the scope of the
claims, each numerical parameter should at least be construed in
light of the number of reported significant digits and by applying
ordinary rounding techniques.
[0037] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contains certain errors necessarily resulting from the
standard deviation found in their respective testing measurements.
Moreover, all ranges disclosed herein are to be understood to
encompass any and all subranges subsumed therein. For example, a
range of "1 to 10" includes any and all subranges between (and
including) the minimum value of 1 and the maximum value of 10, that
is, any and all subranges having a minimum value of equal to or
greater than 1 and a maximum value of equal to or less than 10,
e.g., 5.5 to 10.
[0038] It is noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the," include
plural referents unless expressly and unequivocally limited to one
referent. Thus, for example, reference to "tau protein" includes
one, two, three or more tau proteins.
[0039] Reference will now be made in detail to certain embodiments
of the invention, examples of which are illustrated in the
accompanying drawings. While the invention will be described in
conjunction with the illustrated embodiments, it will be understood
that they are not intended to limit the invention to those
embodiments. On the contrary, the invention is intended to cover
all alternatives, modifications, and equivalents, which may be
included within the invention as defined by the appended
claims.
[0040] The references, mentioned in the specification, are
incorporated herein by reference for all that they disclose.
[0041] The headings below are not meant to limit the disclosure in
any way; embodiments under any one heading may be used in
conjunction with embodiments under any other heading.
[0042] In various embodiments, the activity and composition of tau
protease is provided and methods for its production, and its use
for the development of therapeutics and biomarkers for Alzheimer's
disease and other tauopathies.
[0043] The present disclosure includes methods and compositions
comprising substantially purified and stabilized tau oligomer or a
fragment or a peptide derivative thereof. These tau oligomers and
compositions are useful for the identification of biomarkers
associated with Alzheimer's disease (AD) or tauopathies. Biomarkers
identified according to the methods and compositions disclosed can
be used in diagnosing, stratifying, or monitoring the progression
or regression of AD or tauopathies. The biomarkers may be used as
drug targets to develop new drugs and monitor different medication
therapies to treat AD or tauopathies.
DEFINITIONS
[0044] Tauopathies are a class of neurodegenerative diseases
resulting from the pathological aggregation of tau protein in
so-called neurofibrillary tangles (NFT) in the brain. Some examples
of tauopathies include, but are not limited to, frontotemporal
dementia, Alzheimer's disease, progressive supranuclear palsy,
corticobasal degeneration, frontotemporal lobar degeneration, also
known as Pick's disease, or the like.
[0045] "Alzheimer's patient", "AD patient", and all refer to an
individual who has been diagnosed with AD (for example, by MMSE
score or post mortem by autopsy or has been given a probable
diagnosis of Alzheimer's disease (AD). AD includes individuals with
a probable diagnosis of mild AD, moderate AD, or severe AD. Non-AD
patient refers to a "normal" individual or sample from a "normal"
individual who has or would be assessed by a physician as not
having AD or mild cognitive impairment (MCI). In various
embodiments, a non-AD patient may have a Mini-Mental State
Examination (MMSE) (referenced in Folstein et al., J. Psychiatr.
Res 1975; 12:1289-198) score or would achieve a MMSE score in the
range of 27 or above or assessed by another mental examination
method. On average people with Alzheimer's disease who do not
receive treatment lose 2 to 4 points each year on the MMSE. An
"individual" is a mammal, more preferably a human. Mammals include,
but are not limited to, humans, primates, farm animals, sport
animals, rodents and pets.
[0046] An "individual with mild AD" or "mild AD" is an individual
who has been diagnosed with AD (for example, post mortem by
autopsy) or has been given a diagnosis of probable AD. In various
embodiments, this individual has either been assessed with the
Mini-Mental State Examination (MMSE) (referenced in Folstein et
al., J. Psychiatr. Res 1975; 12:1289-198) and scored 20-26 or would
achieve a score of 20-26 upon MMSE testing or assessed by another
mental examination method.
[0047] An "individual with moderate AD" or "moderate AD" is an
individual who has been diagnosed with AD (for example, post mortem
by autopsy) or has been given a diagnosis of probable AD. In
various embodiments, this individual has either been assessed with
the MMSE and scored 10-19 or would achieve a score of 10-19 upon
MMSE testing or assessed by another mental examination method.
[0048] An "individual with severe AD" or "severe AD" is an
individual who has been diagnosed with AD (for example, post mortem
by autopsy) or has been given a diagnosis of probable AD. In
various embodiments, this individual has either been assessed with
the MMSE and scored below 10 or would achieve a score of below 10
upon MMSE testing or assessed by another mental examination
method.
[0049] As used herein, methods for "aiding diagnosis" refer to
methods that assist in making a clinical determination regarding
the presence, or nature, of the AD or MCI or tauopathy, and may or
may not be conclusive with respect to the definitive diagnosis.
Accordingly, for example, a method of aiding diagnosis of AD or
tauopathy can comprise measuring the amount of one or more AD or
tauopathy biomarkers in a biological sample from an individual.
[0050] The term "stratifying" refers to sorting individuals into
different classes or strata based on the features of AD or
tauopathy. For example, stratifying a population of individuals
with Alzheimer's disease involves assigning the individuals on the
basis of the severity of the disease (e.g., mild, moderate, severe,
etc.).
[0051] As used herein, the term "treatment" refers to the
alleviation, amelioration, and/or stabilization of symptoms, as
well as delay in progression of symptoms of a particular disorder.
For example, "treatment" of AD includes any one or more of:
elimination of one or more symptoms of AD, reduction of one or more
symptoms of AD, stabilization of the symptoms of AD (e.g., failure
to progress to more advanced stages of AD), and delay in
progression (e.g., worsening) of one or more symptoms of AD, and
regression (e.g., reverting back to the earlier stage of AD).
[0052] As used herein, the term "predicting" refers to making a
finding that an individual has a significantly enhanced probability
of developing AD or tauopathy. The term "prognosis" includes the
likely outcome or course of AD or tauopathy.
[0053] In various embodiments of the present application, we
disclose novel purified and stabilized tau oligomer or a fragment
or a peptide derivative thereof. Tau protein exists in 6 isoforms
of 352-441 amino acid residues in the adult brain. The term "tau
protein" refers to any protein of the tau protein family including,
but not limited to, native tau protein monomer, precursor tau
proteins, tau peptides, tau intermediates, metabolites, tau
derivatives that can be antigenic, or antigenic or non-antigenic
fragments thereof. Fragments include less than entire tau protein
provided the fragment is antigenic and will cause antibodies or
antibody binding fragments to react with the tau fragment.
[0054] Non-reactive tau oligomer includes one composed of 3R tau
(i.e. 3r/3R tau dimer or 3R/4R/3R tau trimer), or one in which
further oxidation has rendered the sulfonic derivative, or one
where truncation has occurred removing the cysteine thiol.
[0055] The tau protein family in addition is characterized by the
presence of a characteristic N-terminal segment which is shared by
all members of the family, sequences of approximately 50 amino
acids inserted in the N-terminal segment, which are developmentally
regulated in the brain, a characteristic tandem repeat region
consisting of 3 or 4 tandem repeats of 31-32 amino acids, and a
C-terminal tail. In various embodiments, tau protein has the
following amino acid sequence shown SEQ ID NOS. 1-6. Embodiments of
tau protein may have an amino acid sequence that is 70%, 71%, 72%,
73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%,
86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or
99% identical or substantially identical to the sequence given in
SEQ ID NOS: 1-6.
[0056] As applied to any of the disclosed tau protein, peptides,
the term "substantially identical" means that two peptide or
protein sequences, when optimally aligned, such as by the programs
GAP or BESTFIT using default gap weights, share at least 70 percent
sequence identity, such as at least 90 percent sequence identity,
or at least 95 percent sequence identity, or at least 99 percent
sequence identity. Residue positions, which are not identical, in
various embodiments, differ by conservative amino acid
substitutions. Conservative amino acid substitutions refer to the
interchangeability of residues having similar side chains. For
example, a group of amino acids having aliphatic side chains is
glycine, alanine, valine, leucine, and isoleucine; a group of amino
acids having aliphatic-hydroxyl side chains is serine and
threonine; a group of amino acids having amide-containing side
chains is asparagine and glutamine; a group of amino acids having
aromatic side chains is phenylalanine, tyrosine, and tryptophan; a
group of amino acids having basic side chains is lysine, arginine,
and histidine; and a group of amino acids having sulfur-containing
side chains is cysteine and methionine. In various embodiments,
conservative amino acids substitution groups are:
valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine,
alanine-valine, glutamic-aspartic, and asparagine-glutamine.
[0057] In some embodiments, tau protein is provided. The six tau
protein isoforms can be expressed by alternated splicing of the
primary transcript of the MAPT gene on chromosome 17q21. Tau
isoforms can be expressed in the central nervous system (FIG. 1);
SEQ ID NO. 1-6. The convention used for amino acid numbering is
based on the longest of the six tau isoforms containing 441 amino
acids. R1 includes the first microtubule-binding repeat:
244qtapvpmpdlknvkskigstenlkhqpgggk274 (FIGS. 2 and 3). R2 includes
the second microtubule-binding repeat:
275gggkvqiinkkldlsnvqskcgskdnikhvpgggs305 (FIGS. 2 and 3). R3
includes the third microtubule-binding repeat: 306
pgggsvqivykpvdlskvtskcgslgnihhkpgggq336 (FIGS. 2 and 3). R4
includes the fourth microtubule-binding repeat:
337vevksekldfkdrvqskigsldnithvpgggn368 (FIGS. 2 and 3). R' includes
the pseudo microtubule-binding repeat:
369kkiethkltfrenakaktdhgaeivykspvvs400 (FIGS. 2 and 3).
[0058] 3R tau includes tau isoforms 3R/0N, 3R/1N, 3R/2N, containing
410, 381 or 352 amino acids, lacking the second microtubule-binding
repeat (R2) due to alternate splicing of exon 10, and containing 0,
1 or 2 N-terminal inserts due to alternate splicing of exons 2 or 3
(FIGS. 1 and 2). 3R tau also includes fragments or peptides of tau
including the 3R microtubule binding domain.
[0059] 4R tau includes tau isoforms 4R/0N, 4R/1N, 4R/2N containing
441, 412 or 383 amino acids containing all microtubule-binding
repeats including R2, and containing 0, 1 or 2 N-terminal inserts
due to alternate splicing of exons 2 or 3 (FIG. 1). 4R tau also
includes fragments or peptides of tau including the 4R microtubule
binding domain.
[0060] PHF6* includes hexapeptide motif 275vqiink280, which
exhibits propensity to form bet-sheet structure.
[0061] PHF6 includes hexapeptide motif 306vqivyk311, which exhibits
propensity to form bet-sheet structure.
[0062] Tau monomer includes any individual 3R or 4R tau.
[0063] Tau oligomer includes an aggregate of tau protein subunits.
The minimal size of a tau oligomer is two subunits, and the maximal
size of a tau oligomer referred to in this application is 12 tau
subunits. These tau oligomers are tau dimer, tau trimer, tau
tetramer, tau pentamer, tau hexamer, tau septamer, tau octamer, tau
nonamer, tau decamer, tau unadecamer, tau dodecamer. In some
embodiments, the subunits may be composed of any 3R or 4R tau.
[0064] The tau oligomer can be substantially purified and/or
isolated (FIG. 6). In some embodiments, tau protein can be purified
by cation exchange using SP Sepharose, heat denaturation in Laemmli
sample buffer 5 min at 95.degree. C., and fraction collection from
continuous SDS-PAGE. Tau oligomers can be formed by incubation of
tau subunits in buffer (50 mM Tris pH 7.4) at 37.degree. C. The
size range of the oligomers may be controlled by modulation of tau
concentration, length of incubation, buffer composition, and/or
choice of tau isoforms, fragment or peptide and/or mixtures
thereof.
[0065] The tau oligomer subunits may or may not be linked by
disulfide bonds. In some embodiments, the tau oligomer can be
stabilized by disulfide bonds and is stable for at least two months
in a non-reductive environment.
[0066] In some embodiments, the tau subunits interact in a specific
orientation such that: during 3R tau-3R tau intermolecular
association the hexapeptide motif PHF6 in R3 of one 3R subunit
aligns with the hexapeptide motif PHF6 in R3 of the other 3R tau
subunit in the same amino to carboxyl orientation such that they
may form cross beta strand structure; such that cysteine322 in R3
in one 3R tau subunit and cysteine322 in R3 in the other 3R tau
subunit are aligned enabling disulfide bond formation; such that
there are no free thiol groups and hexapeptide motifs in each of
the 3R tau subunits precluding similar associations with additional
4R or 3R tau subunits (FIG. 13). During 4R tau-4R tau
intermolecular association the hexapeptide motif PHF6* in R2 of one
tau subunit aligns with the hexapeptide motif PHF6 in R3 of the
other 4R tau subunit in the same amino to carboxyl orientation such
that they may form cross beta strand structure; such that
cysteine291 in R2 and cysteine322 in R3 are aligned enabling
disulfide bond formation; such that there are a free thiol group
and hexapeptide motif in each of the 4R tau subunits enabling
similar associations with additional 4R or 3R tau subunits
facilitating oligomer extension from either end (FIG. 14). During
4R tau-3R tau intermolecular association the hexapeptide motif
PHF6* in R2 of the 4R tau subunit aligns with the hexapeptide motif
PHF6 in R3 of the 3R tau subunit in the same amino to carboxyl
orientation such that they may form cross beta strand structure;
such that cysteine291 in R2 of 4R tau and cysteine322 in R3 of 3R
tau are aligned enabling disulfide bond formation; such that there
is unidirectional oligomer extension from the 4R tau end of the
oligomer containing one free thiol group and one hexapeptide motif
and termination of oligomer extension from the 3R end with no free
hexapeptide motifs or thiols (FIG. 15); such that addition of 3R
tau to both ends of an oligomer terminates oligomer extension
through this mechanism (FIG. 16). In some embodiments, the cross
beta sheet structures in the oligomer may stack in antiparallel
orientation. In some embodiments, oligomer size may be controlled
by modulation of the ratio of 3R to 4R tau concentrations (FIGS. 4
and 5).
[0067] In various embodiments, tau monomeric units (tau proteins
(e.g., SEQ ID NOS: 1-6), peptides, or fragments thereof) may
oligomerize and form tau oligomers, which are soluble in bodily
fluids (e.g., CSF, blood, urine, cytoplasmic fluid, etc.). It has
been found by Applicants that extracellular soluble tau monomeric
units and/or tau oligomers increase in AD or tauopathies.
[0068] Tau oligomerization includes multimerizing two or more tau
proteins, tau peptides, tau intermediates, tau metabolites, tau
derivatives that can be antigenic, tau antigenic fragments, or
tau-tau complexes. The multimer can contain any desired number of
tau peptide/protein complexes and thus can form any multimer, such
as but not limited to, a dimer, a trimer, a tetramer, a pentamer, a
hexamer, octamer, decamer, dodecamer, or the like. However, in
order to be soluble in bodily fluids (e.g., CSF, blood, urine,
etc.) the multimer cannot be too long as it may become insoluble in
bodily fluids. By "insoluble" is meant that the tau oligomer will
precipitate out of the bodily fluid. In various embodiments, tau
oligomer that comprises 50 tau monomer units is too long and may be
insoluble in bodily fluids. In other embodiments, tau oligomer that
comprises 100 tau monomer units is too long and may be insoluble in
bodily fluids. By "soluble" is meant that the tau oligomer will
dissolve in the bodily fluid. For example, soluble tau may be
extracellular and appear in the CSF. By associated is meant
covalent or non-covalent, hydrophobic or hydrophilic interactions,
H bonding, or van der Waals attachment.
[0069] Tau proteins, peptides, or fragments thereof may undergo
truncation at one or more sites (e.g., carboxy and/or amino
truncations). For example, tau proteins may have 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 amino acid truncation at
the N and/or C terminus. Truncation typically occurs by enzymes,
which cleave at the carboxy or amino terminus. Such enzymes,
include, but are not limited to caspases that comprise cysteine
proteases.
[0070] "Tau protease" includes an enzyme that can cleave, digest,
or degrade tau oligomer (e.g., tau dimmer, trimer, tetramer, etc.)
into the lower order structure or even monomeric units to fragments
thereof. In some embodiments, the tau itself can act as a protease
and cleave itself when it is in the oligomeric form. This type of
activity is referred to, in some embodiments, as autoproteolytic
activity.
[0071] In some embodiments, a tau protease is an oligomer of tau
composed of at least one 4R tau and additional 3R and 4R tau
molecules. The minimal structure of a tau protease is 4R tau-4R tau
dimer or 4R tau-3R tau dimer. Tau dimer and tau trimer have
proteolytic activity as evidenced by the fragmentation of tau in
these preparations during incubation, whereas reduction of tau
oligomer to tau monomer inhibited tau fragmentation during
incubation. Additionally, tau monomer preparations do not exhibit
proteolytic activity (FIG. 8). Tau protease can be formed and
purified and/or isolated following the methods for isolating tau
oligomers.
[0072] In one embodiment, tau protease is an endopeptidase and
member of the class of cysteine proteases that have a common
catalytic mechanism involving a nucleophilic cysteine thiol in a
catalytic triad (FIGS. 7 and 11). In one embodiment the tau
oligomer protease is a papain-like cysteine protease (CAT B-like
endoprotease) based on analysis of its active site and sequence
similarities to tau (FIG. 10).
[0073] In some embodiments, tau-tau interaction enables formation
of a cleft that contains the active site, which contains the
catalytic triad. Tau oligomers with two terminal 4R tau subunits
can form two active sites, whereas a terminal 3R tau subunit
precludes activity at that end of the oligomer. The availability of
cysteine thiols is enabled by the interaction of R2 of 4R tau with
R3 of 3R or 4R tau such that there is at least one free thiol
available in one or both of the 4R tau subunits from cysteine291 in
R2 and/or cysteine322 in R3. Additional structures of tau dimers,
not included in the tau oligomer definitions above, enabling thiol
availability are interaction of tau subunits by alignment of R3 of
one subunit with R3 of the other subunit such that cysteines at
position 322 in each of the subunits form a disulfide bond, and
such that there are free thiols from cysteines at position 291 in
each subunit in R2 or by alignment of R2 of one subunit with R2 of
the other subunit such that cysteines at position 291 in each of
the subunits form a disulfide bond, and such that there are free
thiols from cysteines at position 322 in each subunit in R3. The
histidine residues in the tau protease active site required for
deprotonation of the thiol/s are histidine299 in R2 and
histidine239 or histidine330 in R3. In one embodiment, derived from
analysis of tau proteolytic fragments (FIG. 8), the carbonyl carbon
of glycine at position 302, and possibly glycine303 or glycine304
is the substrate of the nucleophilic attack by the deprotonated
cysteine's anionic sulfur. In another embodiment glycine164 is the
carbonyl carbon of glycine at position 164 is the substrate of the
nucleophilic attack by the deprotonated cysteine's anionic
sulfur.
[0074] In one embodiment, during nucleophilic attack a 28 kDa
fragment of the substrate is released with an amine terminus, the
histidine residue in the protease is restored to its deprotonated
form, and a thioester intermediate linking the new carboxy-terminus
of the substrate to the cysteine thiol is formed. The thioester
bond is subsequently hydrolyzed to generate a carboxylic acid
moiety on the remaining substrate 14 kDa fragment, while
regenerating the free enzyme thiol group.
[0075] In some embodiments, proteases can cleave tau. These
proteases include, for example, cellular proteases, such as for
examples, caspase, cathepsin B, CAT B-like endoprotease, or other
cysteine proteases. These proteases can be added by exogenous
administration to an animal or can be produced endogenously in vivo
by the animal.
[0076] "Cleaved tau protein" or "cleaved tau products" includes for
example, tau proteins that may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
45, 46, 47, 48, 49, or 50 amino acids cleaved from the N and/or C
terminus of tau. These can be also referred to as tau fragments and
result from a separate protease or when tau cleaves itself.
[0077] Any protease inhibitors may be used to prevent or reduce tau
cleavage. Some examples of protease inhibitors include AEBSF
(4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride), which is
a serine protease inhibitor that inhibits trypsin, chymotrypsin,
plasmin, kallikrein, thrombin; or E-64
(N--[N-(L-3-transcarboxyirane-2-carbonyl)-L-Leucyl]-agmatine),
which is an irreversible and highly selective cysteine protease
inhibitor; or N-ethylmaleimide, which is a cysteine protease
inhibitor like calpain; or phenylene dimaleimide, which is a
cysteine protease inhibitor or a combinations thereof. Some
additional cysteine protease inhibitors that can prevent tau
cleavage, include, CA074Me, amelimide, or combination thereof.
These cysteine proteases can prevent or inhibit tau cleavage and
allow the oligomer to remain intact or prevent or inhibit tau
protein from acting as a protease itself.
[0078] Cysteine protease inhibitors include aldehydes,
semicabazones, methyl ketones, trifluoromethyl ketones, alpha keto
acids, alpha esters, alpha keto amides, and diketones, nitriles,
halomethyl ketones, diazomethanes, acyloxymethylketones,
methysulfonium salts, epoxysuccinyl derivatives, unsaturated
derivatives, disulfides, azapeptides, azobenzenes,
o-acylhydroxamates, lysosomotropic bases, calmodulin antagonists,
aziridines, thiiranes, or the like as discussed by Otto et al. in
Chem Reviews 1997, 97, 133-171. This entire disclosure is herein
incorporated by reference into the present disclosure.
[0079] An "isolated" tau oligomer or tau peptide derivative, or tau
fragment, as used herein, means a naturally-occurring tau oligomer
or peptide or fragment that has been separated or substantially
separated from the cellular components (e.g., CSF, brain cells,
other peptides, etc.) that naturally accompany it by purification,
recombinant synthesis, or chemical synthesis, and also encompasses
non-naturally-occurring recombinantly or chemically synthesized
oligomers or peptides or fragments that have been purified or
substantially purified from cellular components, biological
materials, chemical precursors, or other chemicals. In vitro
methods of making tau oligomer are described in U.S. application
Ser. No. 11/704,079, filed Feb. 8, 2007 and U.S. Publication No.
20070218491, which is hereby incorporated by reference into the
present disclosure.
[0080] "Purified" as used herein includes that the protein, peptide
derivative or fragment thereof is free not only of other proteins,
but also of other materials used in the isolation and
identification of the protein, such as, for example, sodium dodecyl
sulfate and other detergents as well as the support material. The
protein is at least 90% free, preferably at least 95% free and,
more preferably, at least 98% or 99% free of such materials.
[0081] Tau oligomer can be cleaved into a fragment and be in a
peptide form. "Peptide" comprises a string of at least three amino
acids linked together by peptide bonds. Peptide may refer to an
individual peptide or a collection of peptides. Inventive peptides
may contain only natural amino acids, although non-natural amino
acids (i.e., compounds that do not occur in nature but that can be
incorporated into a polypeptide chain; see, for example,
http://www.cco.caltech.edu/.about.dadgrp/Unnatstruct.gif, which
displays structures of non-natural amino acids that have been
successfully incorporated into functional ion channels) and/or
amino acid analogs as are known in the art may alternatively be
employed. Also, one or more of the amino acids in an inventive
peptide may be modified, for example, by the addition of a chemical
entity such as a carbohydrate group, a phosphate group, a farnesyl
group, an isofarnesyl group, a fatty acid group, a linker for
conjugation, functionalization, or other modification, etc. These
modifications may include cyclization of the peptide, the
incorporation of D-amino acids, etc. None of the modifications
should substantially interfere with the desired biological activity
of the peptide.
[0082] "Peptide derivatives" includes derivatives (chemically
functionalized protein molecules obtained starting with the
disclosed protein sequences) or mimetics (three-dimensionally
similar chemicals) of the native tau oligomer, as well as proteins
sequence variants (such as mutants), genetic alleles, fusions
proteins of tau or combinations thereof.
[0083] A "free cysteine amino acid" refers to a cysteine amino acid
residue which has a thiol functional group (--SH), and is not
paired as an intramolecular or intermolecular disulfide bridge.
Accordingly, the free cysteine amino acid can be antigenic for
generation of antibodies to it.
[0084] A "free thiol moiety" refers to the amino acid (e.g.,
cysteine) which has a thiol functional group (--SH), and is not
paired as an intramolecular or intermolecular disulfide bridge.
[0085] "Tau-A.beta. complex" includes interactions, aggregates,
and/or coupling between tau, tau intermediates, metabolites, tau
derivatives, or antigenic fragments of tau and .beta.-amyloid
protein (A.beta.1-42), A.beta.1-42 intermediates, A.beta.1-42
metabolites, A.beta.1-42 derivatives, or antigenic fragments of
A.beta.1-42. A.beta.1-42 comprises 42 amino acids (SEQ ID NO: 7).
In various embodiments, tau-A.beta. complex comprises at least tau
and .beta.-amyloid protein (A.beta.1-42) or tau and A.beta.1-40
protein. In various embodiments, tau-A.beta. complex comprises at
least tau and .beta.-amyloid protein (A.beta.1-42) or tau and
A.beta.1-40 protein and tau and A.beta.1-42 or A.beta.1-40
molecules, such as, for example, amyloid oligomer, other amyloid
protein, tau-oligomer-A.beta.1-42 or tau and A.beta.1-40
protein.
[0086] "Amyloid" refers to amyloidogenic proteins, peptides, or
fragments thereof which can be soluble (e.g., monomeric or
oligomeric) see, e.g., Lambert et al., Proc. Natl. Acad. Sci.
U.S.A. 95, 6448-6453 (1998)). .beta.-amyloid protein (A.beta.) may
comprise 39-43 amino acids. Typically, the A.beta.1-42 peptide is
produced by sequential proteolytic cleavage of the amyloid
precursor protein (APP) by the enzyme(s) beta and gamma secretases.
The length of the A.beta. peptide appears to dramatically alter its
biochemical/biophysical properties. Specifically, the additional
two amino acids at the C-terminus of A.beta.1-42 are very
hydrophobic, presumably increasing the propensity of A.beta.1-42 to
aggregate. For example, Jarrett et al. demonstrated that
A.beta.1-42 aggregates vary rapidly in vitro as compared to
A.beta.1-40, suggesting that the longer forms of A.beta. may be the
important pathological proteins that are involved in the initial
seeding of the neuritic plaques in Alzheimer's disease (Jarrett et
al., Biochemistry 32, 4693-4697 (1993); Jarrett et al., Ann. NY
Acad. Sci. 695, 144-148, (1993)).
[0087] As used herein, the term ".beta.-amyloid" or "A.beta." or
"amyloid beta" refer to amyloid beta proteins or peptides, amyloid
beta precursor proteins or peptides, intermediates, and
modifications and immunologic fragments thereof, unless otherwise
specifically indicated. In particular, "A.beta." refers to any
peptide produced by proteolytic processing of the APP gene product
or peptides that are associated with amyloid pathologies, including
A.beta.1-39, A.beta.1-40, A.beta.1-41, A.beta.1-42, and
A.beta.1-43. Embodiments of A.beta.1-42 may have an amino acid
sequence that is 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%,
80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%,
93%, 94%, 95%, 96%, 97%, 98% or 99% identical or substantially
identical to the sequence given in SEQ ID NO: 7.
[0088] In some embodiments, the "aggregation core", contains all of
the important structural elements for the tau dimer binding
interface between the two tau monomers and will be used to isolate
tau oligomer specific antibodies that recognize this structural
epitope.
[0089] The tau oligomer or a cleaved tau fragment or a peptide
thereof can be used as a biomarker. A "biomarker" includes,
protein(s), peptide(s), protein-protein complexes or aggregates,
protein-peptide complexes or aggregates, peptide-peptide complexes
or aggregates, immunogenic fragments, or metabolite(s) (e.g.,
glycated, truncated, phosphorylated peptide, protein, complex,
aggregates) whose presence, absence, or, level of expression is a
measure of the progression or regression of tauopathy, AD or of the
likelihood of developing tauopathy, or AD. A biomarker may comprise
a single protein, peptide, protein-protein complex, protein-peptide
complex, peptide-peptide complex or metabolite, or it may comprise
a plurality of proteins, peptides, complexes, immunogenic fragments
and/or metabolites whose presence, absence, or levels of expression
collectively provide a measure of the progression or regression of
tauopathy, AD or of the likelihood of developing a tauopathy or
AD.
[0090] The tau oligomer or a fragment or a peptide thereof can be
used as an epitope or antigen to generate antibodies thereto. The
term "epitope" or "antigenic determinant" refers to a site on an
antigen to which B and/or T cells respond or a site on a molecule
against which an antibody will be produced and/or to which an
antibody will bind. For example, an epitope can be recognized by an
antibody defining the epitope. A "linear epitope" is an epitope
where an amino acid primary sequence comprises the epitope
recognized. A linear epitope typically includes at least 3, and
more usually, at least 5, for example, about 8 to about 10 amino
acids in a unique sequence. A "conformational epitope", in contrast
to a linear epitope, is an epitope wherein the primary sequence of
the amino acids comprising the epitope is not the sole defining
component of the epitope recognized (e.g., an epitope wherein the
primary sequence of amino acids is not necessarily recognized by
the antibody defining the epitope). Typically a conformational
epitope comprises an increased number of amino acids relative to a
linear epitope. With regard to recognition of conformational
epitopes, the antibody recognizes a 3-dimensional structure of the
peptide or protein or fragment thereof. For example, when a protein
molecule folds to form a three dimensional structure, certain amino
acids and/or the polypeptide backbone forming the conformational
epitope become juxtaposed enabling the antibody to recognize the
epitope. Methods of determining conformation of epitopes include
but are not limited to, for example, x-ray crystallography
2-dimensional nuclear magnetic resonance spectroscopy and
site-directed spin labeling and electron paramagnetic resonance
spectroscopy.
[0091] The term "antibody" is used to include intact antibodies and
binding fragments thereof, including but not limited to, for
example, full-length antibodies (e.g., an IgG antibody) or only an
antigen binding portion (e.g., a Fab, F(ab').sub.2 or scFv
fragment). The fragment can also be generated by phage display
technology known in the art.
[0092] Typically, fragments compete with the intact antibody from
which they were derived for specific binding to an antigen.
Optionally, antibodies or binding fragments thereof, can be
chemically conjugated to, or expressed as, fusion proteins with
other proteins. The term "antibody fragment" refers to a portion of
a full-length antibody, generally the antigen binding or variable
region. Examples of antibody fragments include Fab, Fab',
F(ab').sub.2 and Fv fragments. In various embodiments, papain
digestion of antibodies produces two identical antigen binding
fragments, called the Fab fragment, each with a single antigen
binding site, and a residual "Fc" fragment, so-called for its
ability to crystallize readily. In various embodiments, pepsin
treatment yields an F(ab').sub.2 fragment that has two antigen
binding fragments which are capable of cross-linking antigen, and a
residual other fragment (which is termed pFc'). As used herein,
"functional fragment" with respect to antibodies, refers to Fv,
F(ab) and F(ab').sub.2 fragments.
[0093] An "Fv" fragment is the minimum antibody fragment, which
contains a complete antigen recognition and binding site. This
region consists of a dimer of one heavy and one light chain
variable domain in a tight, non-covalent association
(V.sub.H-V.sub.L dimer). It is in this configuration that the three
complementarity determining regions (CDRs) of each variable domain
interact to define an antigen binding site on the surface of the
V.sub.H-V.sub.L dimer. Collectively, the six CDRs confer antigen
binding specificity to the antibody. However, even a single
variable domain (or half of an Fv comprising only three CDRs
specific for an antigen) has the ability to recognize and bind
antigen, although at a lower affinity than the entire binding site.
The Fab fragment (also designated as F(ab)) also contains the
constant domain of the light chain and the first constant domain
(CH1) of the heavy chain. Fab' fragments differ from Fab fragments
by the addition of a few residues at the carboxyl terminus of the
heavy chain CH1 domain including one or more cysteines from the
antibody hinge region. Fab'-SH is the designation herein for Fab'
in which the cysteine residue(s) of the constant domains have a
free thiol group. F(ab') fragments are produced by cleavage of the
disulfide bond at the hinge-cysteines of the F(ab').sub.2 pepsin
digestion product. Additional chemical couplings of antibody
fragments are known to those of ordinary skill in the art.
[0094] The term "monoclonal antibody" as used herein refers to an
antibody obtained from a population of substantially homogeneous
antibodies, e.g., the individual antibodies comprising the
population are identical except for possible naturally occurring
mutations that may be present in minor amounts. Monoclonal
antibodies are highly specific, being directed against a single
antigenic site. Furthermore, in contrast to conventional
(polyclonal) antibody preparations, which typically include
different antibodies, directed against different determinants
(epitopes), each monoclonal antibody is directed against a single
determinant on the antigen. In addition to their specificity, the
monoclonal antibodies are advantageous in that they are synthesized
by the hybridoma culture, uncontaminated by other immunoglobulins.
The modifier "monoclonal" indicates the character of the antibody
as being obtained from a substantially homogeneous population of
antibodies, and is not to be construed as requiring production of
the antibody by any particular method. For example, the monoclonal
antibodies to be used in accordance with the present invention may
be made by the hybridoma method first described by Kohler and
Milstein, Nature 256, 495 (1975), or may be made by recombinant
methods, e.g., as described in U.S. Pat. No. 4,816,567. "Polyclonal
antibodies" include different antibodies directed against different
determinants (epitopes).
[0095] "Specific binding" or "binding specifically" between two
entities, may include a binding affinity of at least 10.sup.6,
10.sup.7, 10.sup.8, 10.sup.9M.sup.-1, or 10.sup.10 M.sup.-1.
Affinities greater than 10.sup.8 M.sup.-1 are preferred for
specific binding. Antibodies to tau are described in U.S. patent
application Ser. No. 12/069,399, filed Feb. 8, 2008 and published
as US-2008-0220449. The entire disclosure is hereby incorporated by
reference into the present disclosure.
[0096] The tau oligomer or a fragment or a peptide thereof can be
used as an immunotherapeutic agent. The term "immunotherapeutic
agent" is intended to mean an agent that stimulates anti-tau
oligomer immunity. Agents that stimulate anti-tau oligomer activity
are preferably those that directly or indirectly stimulate T-cells
and/or NK cells to stop the oligomerization of tau to achieve a
prophylactic and/or therapeutic goal. The tau oligomer or a
fragment or a peptide derivative thereof can be used to make
antibodies for passive immunotherapies or the tau oligomer or a
fragment or a peptide derivative thereof can be used for active
immunity, such as for example, in a vaccine composition when
administered to the mammal.
[0097] The tau oligomer or a fragment or a peptide derivative
thereof can be used with adjuvants and administered to the animal.
Any adjuvant may be used in accordance with the present invention.
A large number of adjuvant compounds is known; a useful compendium
of many such compounds is prepared by the National Institutes of
Health and can be found on the world wide web
(http:/www.niaid.nih.gov/daids/vaccine/pdf/compendium.pdf,
incorporated herein by reference; see also Allison Dev. Biol.
Stand. 92:3-11, 1998; Unkeless et al. Annu. Rev. Immunol.
6:251-281, 1998; and Phillips et al. Vaccine 10:151-158, 1992, each
of which is incorporated herein by reference). Hundreds of
different adjuvants are known in the art and could be employed in
the practice of the present invention.
[0098] The tau oligomer or a fragment or a peptide derivative
thereof can be administered to the animal in a pharmaceutical
composition. Those of ordinary skill in the art will appreciate
that pharmaceutical composition can be administered to individuals
via any of a variety of routes, protocols, and dosing regimens.
Known routes of administration include, for example, intravenous
(IV), intraperitoneal (IP), intragastric (IG), subcutaneous (SQ),
intramuscular (IM), oral (PO), rectal (PR), intrathecal, vaginal,
intranasal, transdermal, intradermal, subcutaneous, intrathecal,
epidural, or the like.
[0099] The tau oligomer or a fragment or a peptide derivative
thereof can be part of a pharmaceutical composition designed for
administration to the mammal. Pharmaceutical compositions for use
in accordance with the present application may include a
pharmaceutically acceptable excipient or carrier. As used herein,
the term "pharmaceutically acceptable carrier" means a non-toxic,
inert solid, semi-solid or liquid filler, diluent, encapsulating
material or formulation auxiliary of any type. Some examples of
materials which can serve as pharmaceutically acceptable carriers
are sugars such as lactose, glucose, and sucrose; starches such as
corn starch and potato starch; cellulose and its derivatives such
as sodium carboxymethyl cellulose, ethyl cellulose, and cellulose
acetate; powdered tragacanth; malt; gelatin; talc; excipients such
as cocoa butter and suppository waxes; oils such as peanut oil,
cottonseed oil; safflower oil; sesame oil; olive oil; corn oil and
soybean oil; glycols such as propylene glycol; esters such as ethyl
oleate and ethyl laurate; agar; buffering agents such as magnesium
hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water;
isotonic saline; Ringer's solution; ethyl alcohol, and phosphate
buffer solutions, as well as other non-toxic compatible lubricants
such as sodium lauryl sulfate and magnesium stearate, as well as
coloring agents, releasing agents, coating agents, sweetening,
flavoring and perfuming agents, preservatives and antioxidants can
also be present in the composition, according to the judgment of
the formulator. The pharmaceutical compositions of this invention
can be administered to humans and/or to animals, orally, rectally,
parenterally, intracistemally, intravaginally, intranasally,
intraperitoneally, topically (as by powders, creams, ointments, or
drops), bucally, or as an oral or nasal spray.
[0100] Any dose can be administered to an animal. Dosages can vary
depending on the relative potency of individual compositions, and
can generally be estimated based on data obtained from in vitro and
in vivo animal models. Typically, the dosage may be from about 0.01
micrograms to about 100 g per kg of body weight, and may be given
once or more daily, weekly, or even less often. Following
successful administration, it may be desirable to have the subject
undergo additional booster administrations to maintain a suitable
level of the anti-tau oligomer, tau fragment, or tau-peptide
activity. For example, an additional dosage can be administered 6,
12, 24, 36, 48, 60 or more months after an initial dosage. In some
cases, additional dosages can be administered every 6, 12, 18, 24,
30, 36, 42, 48, 54, 60 or more months after an initial dosage.
Additional dosages also can be administered as needed.
[0101] The term "animal", as used herein, refers to humans as well
as non-human animals, including, for example, mammals, birds,
reptiles, amphibians, and fish. Preferably, the non-human animal is
a mammal (e.g., a rodent, a mouse, a rat, a rabbit, a monkey, a
dog, a cat, a primate, or a pig). An animal may be a transgenic
animal.
[0102] The tau oligomer or a fragment or a peptide derivative
thereof can be used a drug target in drug discovery. In various
embodiments, methods of screening for candidate agents for the
treatment of AD or tauopathies are provided by assaying prospective
candidate agents for activity in modulating tau oligomer or a
fragment or a peptide derivative of tau oligomer. The screening
methods may utilize tau oligomer or a fragment or a peptide
derivative of tau oligomer described herein as "drug targets."
Prospective agents are tested for activity in modulating a drug
target in an assay system. As will be understood by those of skill
in the art, the mode of testing for modulation activity will depend
on the biomarker and the form of the drug target used (e.g.,
complete protein or peptide fragment).
[0103] When the tau oligomer or a fragment or a peptide derivative
of tau oligomer itself is the drug target, prospective agents are
tested for activity in modulating levels or activity of the
protein/peptide itself (e.g., soluble tau oligomer). Modulation of
levels of tau oligomer or a fragment or a peptide derivative of tau
oligomer can be accomplished by, for example, increasing or
reducing half-life of the biomarker protein or drug candidate
concentration. Modulation of activity of tau oligomer or a fragment
or a peptide derivative of tau oligomer can also be accomplished by
increasing or reducing the availability of the tau oligomer or a
fragment or a peptide derivative of tau oligomer to bind to its
receptor(s) or ligand(s). In various embodiments, a method of
screening an agent for modulation or disruption of tau oligomer or
a fragment or a peptide derivative of tau oligomer is provided, the
method comprising: a) contacting a sample containing tau oligomer
or a fragment or a peptide derivative of tau oligomer with an agent
suspected of being capable of modulating tau oligomer formation or
disrupting tau oligomers; and b) detecting the amount of tau
oligomer or a fragment or a peptide derivative of tau oligomer in
the sample, wherein a decrease in soluble tau oligomer indicates
that the agent modulates tau oligomer formation or disrupts tau
oligomer. In various embodiments, the mechanism that the agent
disrupts tau oligomer formation is by inhibiting tau-tau
binding.
[0104] The screening assay can also be used to determine effective
doses of agents to optimize disruption or modulation of tau
oligomer. For example, the method of screening compounds may
involve comparing the sample being analyzed to a sample that does
not contain the agent or less agent to determine if the agent
modulates or inhibits tau oligomer. "Disruption" of tau oligomer
includes the interruption of tau oligomer formation.
[0105] Prospective agents for use in the screening methods may be
chemical compounds and/or complexes of any sort, including both
organic and inorganic molecules (and complexes thereof). As will be
understood in the art, organic molecules are most commonly screened
for AD biomarker modulatory activity. In some situations, the
prospective agents for testing will include the target AD biomarker
(e.g., soluble tau oligomer).
[0106] Suitable agents for screening include, but are not limited
to, antioxidants (vitamin E and vitamin C), anti-inflammatory
agents (e.g., curcumin, demethoxycurcumin, bisdemethoxycurcumin,
and/or morin), antibiotics, chelation agents, cliouinol, ergoloids,
estrogen, herbal agents (e.g., ginko biloba, huperzine A, melissa
officinalis (lemon balm), etc.), statins, vitamin B, or proteases,
protease inhibitors, cysteine proteases, combinations thereof or
derivatives thereof. Derivatives include analogs of the above
agents that are pharmacologically active.
[0107] It has been found the new observation that tau protein has
protease activity and that tau protease is an endopeptidase. It has
further been found that tau protease is a cysteine protease. In
some embodiments, it has been found that the tau protease is a
cysteine protease with similarities to papain. In some embodiments,
the composition of tau protease has been discovered. It has also
been found: the mechanism for tau protease activity; that tau
protease requires tau oligomer formation for activity; tau oligomer
formation enables formation of a cleft for the active site; tau
oligomer formation is necessary for protease activity; 4R tau
subunits enable greater possibilities for the formation of
oligomers with free thiols than 3R tau subunits; methods to
modulate tau protease activity by modulating the 3R and 4R tau
subunit composition; the toxicity associated with the relative
overexpression of 4R tau to 3R in multiple neurodegenerative
diseases is caused by the increased formation of tau proteases; a
specific alignment of tau subunits such that there are free thiols
available for the catalytic triad; catalytic triads are composed of
a.) Cysteine 291 or Cysteine322, b.) Histidine 299 or Histidine329
or Histidine330, and c.) Glycine164 or 302, 303 or 304; the tau
protease can cleave itself; the tau protease can cleave other tau
proteins; tau protease cleavage of tau facilitates its aggregation;
the tau protease dependent cleavage of tau causes loss of tau
function; tau protease formation enables gain of toxic function by
cleaving tau and proteins other than tau; tau protease cleaves
intracellular proteins facilitating apoptosis and/or senescence of
neurons and/or other cell types; tau protease cleaves extracellular
proteins such as receptors or neurotansmitters; tau protease
cleaves membrane proteins; tau protease facilitates apoptosis by
activating proteins in apoptosis such as caspases; tau protease
cleaves amyloid precursor protein (APP) facilitating production of
beta amyloid; methods to form tau protease structures; methods to
purify and/or isolate tau proteases; tau protease activity is a
target for small molecule drug discovery for AD and other
tauopathies; tau protease is a target for immunotherapy; protein
fragments generated by tau protease are biomarkers for AD and other
neurodegenerative diseases; and/or the tau proteolytic fragment
with apparent molecular weight of .about.17 kDa is a biomarker for
disease.
Tau Protein Structure and Function
[0108] Tau is encoded by the MAPT gene located on the long (q) arm
of chromosome 17 at position 21.1. Alternative splicing of the
second and third exons in the N-terminal portion of tau and the
tenth exon yields a total of six protein isoforms. Tau is an
intrinsically unstructured protein due to its very low hydrophobic
content and has been characterized to have a projection domain, a
basic proline-rich region, and an assembly domain. The domain in
the carboxyl-terminal portion of the protein critical for tau
self-association into oligomers and fibrils, the assembly domain,
contains either three or four repeats (3R or 4R) of a conserved
tubulin-binding motif depending on alternative splicing of exon 10
encoding the second repeat (Lee et al. 1989). Hexapeptide motifs
PHF6* and PHF6 in the second and third repeats, respectively, have
propensity to form .beta.-sheet structures which are involved in
tau interaction with tubulin to form MTs and tau self-interaction
to form pathological aggregates such as paired helical filaments
(PHF) (von Bergen et al. 2000; Amos 2004). Tau 4R isoforms have
greater microtubule stabilizing ability than 3R isoforms. Only the
shortest 3R tau isoform is expressed during fetal development where
there are dynamic changes in the cytoskeleton, whereas adult brain
normally has a ratio of about 1:1 for 3R to 4R isoforms. Expression
of 4R/2N in the hippocampus of tau knockin/knockout mice suppresses
proliferation and promotes neuronal differentiation (Sennvik et al.
2007). Hyperphosphorylation of tau, particularly in the assembly
domain, decreases the affinity of tau to MTs to regulate MT
dynamics and axonal transport (Konzack et al. 2007; Dubey et al.
2008). Additional regions in the basic proline-rich domain and the
pseudo-repeat also stabilize MTs by interacting with its negatively
charged surface (Mukrasch et al. 2007). The projection domain
facilitates interaction with the plasma membrane (Brandt et al.
1995; Maas et al. 2000). Interaction of tau with membranes is also
thought to facilitate tau aggregation (Chirita et al. 2003). For
recent reviews of tau structure and function see (Wang and Liu
2008; Ballatore et al. 2007).
Tau in Neurodegenerative Diseases
[0109] Genetic evidence has shown that abnormal forms of tau are
sufficient for neurodegeneration causing memory loss and other
neurological deficits in multiple frontotemporal dementia and
sporadic tauopathies (for a recent review of the role of tau in
neurodegeneration see Gendron and Petrucelli 2009; Iqbal et al.
2009). The 32 different mutations found in the study of over 100
families can be grouped into categories influencing splicing of the
primary transcript and causing changes in amino acid sequence of
tau. Most missense mutations are located in the assembly domain and
generally reduce the affinity of tau to MTs. Several of these
mutations promote aggregation of tau in vitro and in vivo such as
P301L and P301S. Mutations in the stem-loop structure at the border
of exon 10 and the following intron alter splicing causing
aberrations in the ratio of 4R to 3R isoforms demonstrating that
maintenance of the proper ratio of tau isoforms is necessary to
prevent neurodegeneration and dementia. Sporadic tauopathies such
as progressive supranuclear palsy, corticobasal degeneration,
Pick's disease and argyrophilic grain disease are characterized by
pathology with tau filaments composed predominantly of 4R isoforms
and are linked to MAPT mutations (Goedert and Jakes 2005).
[0110] Recent reports also indicate aberrant splicing of tau
transcripts in AD demonstrating a common defect with AD and
Parkinson disease. Increases in the ratio of 4R to 3R tau mRNAs
were found in individual human cholinergic basal forebrain neurons
in nucleus basalis and CA1 hippocampal neurons in AD (Ginsberg et
al. 2006). Aberrant alternative splicing in sporadic AD was also
shown using polymerase colony, a single-molecule-based technology.
A trans mechanism involving the reduction of splicing factor
htra2-beta-1 in AD was linked to the increase in four-repeat tau
isoforms (Conrad et al 2007). Further genetic support for a
causative role for tau in AD comes from the observation that tau
haplotypes driving higher levels of tau expression increase AD risk
(Myers et al. 2005) and from the report of linkage of tau
haplotypes with increased CSF tau in people with A.beta. deposition
accelerated AD progression (Kauwe et al. 2008). Similarly,
increased expression of 4R tau and linkage to MAPT haplotypes has
been reported for Parkinson disease (Tobin et al. 2008), the second
most common form of neurodegenerative disease following AD. A
recent study of tau in primary cultures of human cortical neurons
indicated that the 4R tau isoforms are principally involved in tau
oligomerization (Deshpande et al. 2008). There are also multiple
post-translational modifications to tau protein in AD and other
tauopathies that cause both loss of function and gain of toxicity
(Mazanetz et al., 2007).
[0111] In some embodiments, the tau proteins have the following
isoforms:
TABLE-US-00001 Spliced Residues exons Nomenclature 352 -- 3R/0N 381
3 3R/1N 410 2, 3 3R/2N 383 10 4R/0N 412 3, 10 4R/1N 441 2, 3, 10
4R/2N
[0112] Recent advances in research in AD have highlighted the
importance of tau in pathogenesis (Marx, 2007) and its use as a
target for the development of disease modifying therapeutics.
Evidence from mouse models indicates that tau reduction reverses
disease phenotypes (Santacruz et al. 2005; Oddo et al. 2006; Asuni
et al. 2007) and that tau is necessary for the development of
cognitive deficits in AD models caused by over-expression of
A.beta. (Roberson et al. 2007).
[0113] The pathological structures of tau most closely associated
with AD progression are tau oligomers in mouse models that also
accumulate in human neurodegenerative diseases collectively termed
"tauopathies" (Berger et al. 2007; Maeda et al. 2006; Sahara et al.
2007, 2008). NFTs have been implicated in mediating
neurodegeneration in AD and tauopathies as it correlates well with
cognitive deficits and neuron loss (Arriagada et al., 1992; Bancher
1993; Guillozet et al., 2003; Iqbal et al. 2009). However, the
study of animal models of tauopathy has shown that memory
impairment and neuron loss is dissociated from accumulation of NFT
(Brunden et al. 2008; Rocher et al. 2009). Strong support for this
contention came from the analysis of transgenic mice rTg4510 that
express tau P301L in the forebrain under control of a
tetracycline-regulated promoter. These mice developed memory
impairment, neuron loss and NFT when the construct was expressed.
However, suppression of expression caused improvement in memory and
reduction in neuron loss even as NFTs continued to accumulate
clearly demonstrating that pretangle tau species were responsible
for the neurodegenerative phenotype (Santacruz et al. 2005).
Additionally, there was regional dissociation of neuron loss and
NFT pathology in this model (Spires et al. 2006) and in another
mouse model expressing all six human isoforms (Andorfer et al.
2003) showing that tangles are not acutely neurotoxic.
[0114] Incongruence between tangle formation, neurodegeneration and
behavioral deficits were found in other mouse models of tauopathy
and AD. Transgenic mice expressing a human mutant tau P301S
construct prone to aggregation developed hippocampal synapse loss
and dysfunction, as well as, microglial activation months before
the accumulation of filamentous tau inclusions (Yoshiyama et al.
2007). Similarly, a transgenic mouse model expressing human tau
protein with two mutations found in FTDP-17 (P301S and G272V)
exhibited axonopathy before tangle formation (Leroy et al. 2007).
The triple transgenic AD mouse model accumulating both tau and
A.beta. pathology was used to study the effects of immuno-reduction
of tau and A.beta.. Antibodies against both proteins were needed to
improve learning and memory behavior in these mice. Soluble tau,
but not NFT, was reduced by the treatment again showing the
dissociation between the neurodegenerative phenotype and insoluble
tau aggregates (Oddo et al. 2006).
Role of Tau Cleavage in Neurodegenerative Diseases
[0115] Cleavage of tau plays a role in the oligomerization and
formation of a pathological tau species in AD (Gamblin et al. 2003;
Rissman et al. 2004). Although a number of cellular proteases can
cleave tau it is unclear which proteases are facilitating disease
progression. Tau can be cleaved by caspase-3 at Asp421 and results
in a highly fibrillogenic tau isoform aggregates better than
full-length tau and facilitates aggregate formation of full length
tau (Gamblin et al. 2003; Rissman et al. 2004). Immunological
studies indicate that tau truncated at Asp421 co-localize with
fibrillar tau pathologies in AD patient brains (Gamblin et al.
2003; Rissman et al. 2004). Asp-421-cleaved tau is toxic to
cultured neurons (Fasulo et al. 2005; Chung et al. 2001;
Matthews-Roberson et al. 2008) by causing mitochondrial dysfunction
(Quintanilla et al. 2009). However, in a recent publication (Zhang
et al. 2009), there was a lack of activated caspase-3 in truncated
tau-positive neurons in tauP301L single transgenic and
APP/PS1/tauP301L triple transgenic mouse models. Caspase-3 levels
in the brain dramatically decreased early in development and
remained consistently low in adulthood. Hyperphosphorylation of tau
was also found to inhibit caspase-3 cleavage of tau in vivo. Thus,
these animal studies indicate that the results from cell-free and
cell-based assays (Gamblin et al. 2003; Rissman et al. 2004) do not
reflect in vivo conditions and lead to the conclusion that an
unidentified, caspase-3 independent pathway is responsible for tau
truncation at Asp421 (Zhang et al. 2009). In another study of the
appearance of phosphorylated and truncated tau in the brain and
spinal cord of mice transgenic for mutant human P301S tau protein
it was found that the late appearance and low abundance of tau
truncated at Asp421 made it unlikely that truncation at this site
was necessary for tau aggregation (Delobel et al. 2008). Using an
inducible cell model expressing the microtubule binding domain of
tau with the .DELTA.K280 mutation, an unidentified cytosolic
protease activity was identified that cleaves tau towards the
N-terminus of the microtubule binding repeat domain. Subsequent
targeting of the cleaved product to the lysosome led to cathepsin L
truncation of tau at the carboxyl terminus creating fragments
highly prone to aggregation and subsequent degradation by
macroautophagy (Wang et al. 2009).
[0116] Here we show the highly novel mechanism in neurodegenerative
diseases that upon self-association tau acquires proteolytic
activity that leads to its own fragmentation. This activity
accounts for the unknown tau protease activities described above.
The structure of the autoproteolytic dimer and trimer composed of
4R tau with one or two free thiols indicates that it is a cysteine
protease. In context of the disease process, tau self-association
leads to formation of autoproteolytic oligomers that cause loss of
tau function through fragmentation of the protein and at the same
time facilitate aggregation of the cleaved microtubule binding
domain into toxic structures. The proteolytic activity of oligomers
formed from 4R tau helps explain the toxicity of 4R tau
overexpression common in neurodegenerative diseases. Other proteins
may also be targeted by this activity augmenting its toxic gain of
function both in the intra- and extra-cellular environments. This
proteolytic activity is a novel target that is amenable to small
molecule drug discovery, and the autoproteolytic fragments are
direct biomarkers for disease progression as there level indicates
activity of this pathological tau protease.
[0117] Having now generally described the invention, the same may
be more readily understood through the following reference to the
following examples, which are provided by way of illustration and
are not intended to limit the present invention unless
specified.
EXAMPLES
Example 1
[0118] Purified preparations of tau352 or tau441 were incubated at
37.degree. C. in neutral buffer with a very low concentration of
hydrogen peroxide to create an oxidizing environment that would not
lead to protein degradation. Non-reducing sample buffer was used to
prepare samples for SDS-PAGE using a 4-20% gradient gel (BioRad) to
resolve purified tau monomer, dimer, trimer and tetramer. Silver
staining was performed with the Silver Express kit (Invitrogen)
shown in FIG. 4.
Example 2
[0119] Purified preparations of tau352 and tau441 were incubated at
a 1:1 ratio or 1:4 ratio of tau352:tau441 at 37.degree. C. in pH
neutral buffer for 45 min. or 2 days. Non-reducing sample buffer
was used to prepare samples for SDS-PAGE using a 4-20% gradient gel
(BioRad) to resolve purified tau monomer, dimer, trimer and
tetramer. Silver staining was performed with the Silver Express kit
(Invitrogen) Shown in FIG. 5.
Example 3
[0120] Purified Tau412 monomer, dimer and trimer were incubated in
50 mM Tris-HCl pH 7.4 overnight at 37.degree. C. Preparations were
buffer exchanged into artificial CSF buffer (in mM: 124.0 NaCl, 4.4
KCl, 1.0 Na2HPO4, 25.0 NaHCO3, 2.0 CaCl2, 2.0 MgSO4, and 10.0
glucose) using PD10 columns (GE Lifesciences) and the first five
fractions (10 .mu.l) were analyzed by SDS-PAGE (4-20% gradient gel)
and stained with Coumassie blue shown in FIG. 8.
Example 4
[0121] Five post-mortem CSF specimens (10 .mu.l each) from
individuals with advanced AD were analyzed by SDS PAGE using a
4-20% gradient gel (BioRad). Specimens were provided by New York
Brain Bank, Taub Center, Columbia University Medical Center.
Samples were prepared with standard Laemmli buffer (sample buffer
containing reductant) or sample buffer without reductant. Proteins
were transferred to a nitrocellulose membrane and immunoblot was
performed with mAb HT7 recognizing all tau isoforms and
independently of tau phosphorylation (shown in FIG. 17).
Example 5
[0122] Five post-mortem CSF specimens (15 .mu.g each) from
individuals with advanced AD were analyzed by SDS PAGE using a
4-20% gradient gel (BioRad). Samples were prepared with standard
sample buffer containing reductant or sample buffer without
reductant. Specimens were provided by New York Brain Bank, Taub
Center, Columbia University Medical Center. The samples with
reductant were heated 5 min at 95.degree. C. before loading on gel.
Proteins were transferred to a nitrocellulose membrane and
immunoblot was performed with mAb HT7 recognizing all tau isoforms
and independently of tau phosphorylation (shown in FIG. 18).
Example 6
[0123] This example illustrates the amino acid positions where tau
oligomer cuts itself.
Tau Oligomer Protease Fragment Analysis for Tau412 and Tau441 (Note
that the Sequence Number Used are for Tau441 for the Cut Sites)
[0124] Tau412 Cut at Glycine164 N-terminal fragment
Fragment 1
MW=13,989.9
[0125] Estimated pI=4.62 Estimated charge at pH 7.40=-13.9
TABLE-US-00002 MAEPRQEFEVMEDHAGTYGLGDRKDQGGYTMHQDQEGDTDAGLKESPPQT
PTEDGSEEPGSETSDAKSTPTAEAEEAGIGDTPSLEDEAAGHVTQARMVS
KSKDGTGSDDKKAKGADGKTKIATPRGAAPPGQKG
[0126] Tau412 Cut at Glycine164 C-terminal fragment
Fragment 2
MW=28,978.8
Estimated PI=9.98
[0127] Estimated charge at pH 7.40=20.5
TABLE-US-00003 QANATRIPAKTPPAPKTPPSSGEPPKSGDRSGYSSPGSPGTPGSRSRTPS
LPTPPTREPKKVAVVRTPPKSPSSAKSRLQTAPVPMPDLKNVKSKIGSTE
NLKHQPGGGKVQIINKKLDLSNVQSKCGSKDNIKHVPGGGSVQIVYKPVD
LSKVTSKCGSLGNIHHKPGGGQVEVKSEKLDFKDRVQSKIGSLDNITHVP
GGGNKKIETHKLTFRENAKAKTDHGAEIVYKSPVVSGDTSPRHLSNVSST
GSIDMVDSPQLATLADEVSASLAKQGL
[0128] Tau 412 Cut at Glycine302 N-terminal fragment
Fragment 3
MW=28,323.2
Estimated PI=8.73
[0129] Estimated charge at pH 7.40=3.2
TABLE-US-00004 MAEPRQEFEVMEDHAGTYGLGDRKDQGGYTMHQDQEGDTDAGLKESPPQT
PTEDGSEEPGSETSDAKSTPTAEAEEAGIGDTPSLEDEAAGHVTQARMVS
KSKDGTGSDDKKAKGADGKTKIATPRGAAPPGQKGQANATRIPAKTPPAP
KTPPSSGEPPKSGDRSGYSSPGSPGTPGSRSRTPSLPTPPTREPKKVAVV
RTPPKSPSSAKSRLQTAPVPMPDLKNVKSKIGSTENLKHQPGGGKVQIIN
KKLDLSNVQSKCGSKDNIKHVPG
[0130] Tau 412 Cut at Glycine302-C-terminal fragment
Fragment 4
MW=14,645.5
Estimated PI=8.95
[0131] Estimated charge at pH 7.40=3.4
TABLE-US-00005 GGSVQIVYKPVDLSKVTSKCGSLGNIHHKPGGGQVEVKSEKLDFKDRVQS
KIGSLDNITHVPGGGNKKIETHKLTFRENAKAKTDHGAEIVYKSPVVSGD
TSPRHLSNVSSTGSIDMVDSPQLATLADEVSASLAKQGL
[0132] Tau441 Cut at Glycine164 N-terminal fragment
Fragment 5
MW=16,889.0
[0133] Estimated pI=4.56 Estimated charge at pH 7.40=-17.8
TABLE-US-00006 MAEPRQEFEVMEDHAGTYGLGDRKDQGGYTMHQDQEGDTDAGLKESPLQT
PTEDGSEEPGSETSDAKSTPTAEDVTAPLVDEGAPGKQAAAQPHTEIPEG
TTAEEAGIGDTPSLEDEAAGHVTQARMVSKSKDGTGSDDKKAKGADGKTK
IATPRGAAPPGQKG
[0134] Tau441 Cut at Glycine302 C-terminal fragment
Fragment 6
MW=28,978.8
Estimated PI=9.98
[0135] Estimated charge at pH 7.40=20.5
TABLE-US-00007 QANATRIPAKTPPAPKTPPSSGEPPKSGDRSGYSSPGSPGTPGSRSRTPS
LPTPPTREPKKVAVVRTPPKSPSSAKSRLQTAPVPMPDLKNVKSKIGSTE
NLKHQPGGGKVQIINKKLDLSNVQSKCGSKDNIKHVPGGGSVQIVYKPVD
LSKVTSKCGSLGNIHHKPGGGQVEVKSEKLDFKDRVQSKIGSLDNITHVP
GGGNKKIETHKLTFRENAKAKTDHGAEIVYKSPVVSGDTSPRHLSNVSST
GSIDMVDSPQLATLADEVSASLAKQGL
[0136] Tau441 Cut at Glycine302 N-terminal fragment
Fragment 7
MW=31,222.3
[0137] Estimated pI=7.14 Estimated charge at pH 7.40=-0.6
TABLE-US-00008 MAEPRQEFEVMEDHAGTYGLGDRKDQGGYTMHQDQEGDTDAGLKESPLQT
PTEDGSEEPGSETSDAKSTPTAEDVTAPLVDEGAPGKQAAAQPHTEIPEG
TTAEEAGIGDTPSLEDEAAGHVTQARMVSKSKDGTGSDDKKAKGADGKTK
IATPRGAAPPGQKGQANATRIPAKTPPAPKTPPSSGEPPKSGDRSGYSSP
GSPGTPGSRSRTPSLPTPPTREPKKVAVVRTPPKSPSSAKSRLQTAPVPM
PDLKNVKSKIGSTENLKHQPGGGKVQIINKKLDLSNVQSKCGSKDNIKHV PG
[0138] Tau441 Cut at Glycine302 C-terminal fragment
Fragment 8
MW=14,645.5
Estimated PI=8.95
[0139] Estimated charge at pH 7.40=3.4
TABLE-US-00009 GGSVQIVYKPVDLSKVTSKCGSLGNIHHKPGGGQVEVKSEKLDFKDRVQS
KIGSLDNITHVPGGGNKKIETHKLTFRENAKAKTDHGAEIVYKSPVVSGD
TSPRHLSNVSSTGSIDMVDSPQLATLADEVSASLAKQGL
[0140] The references disclosed below are hereby incorporated by
reference into the present disclosure for all that they
disclose.
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[0216] It will be apparent to those skilled in the art that various
modifications and variations can be made to various embodiments
described herein without departing from the spirit or scope of the
teachings herein. Thus, it is intended that various embodiments
cover other modifications and variations of various embodiments
within the scope of the present teachings.
Sequence CWU 1
1
71352PRTHomo sapiens 1Met Ala Glu Pro Arg Gln Glu Phe Glu Val Met
Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys Asp Gln
Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr Asp Ala
Gly Leu Lys Ala Glu Glu Ala 35 40 45Gly Ile Gly Asp Thr Pro Ser Leu
Glu Asp Glu Ala Ala Gly His Val 50 55 60Thr Gln Ala Arg Met Val Ser
Lys Ser Lys Asp Gly Thr Gly Ser Asp65 70 75 80Asp Lys Lys Ala Lys
Gly Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro 85 90 95Arg Gly Ala Ala
Pro Pro Gly Gln Lys Gly Gln Ala Asn Ala Thr Arg 100 105 110Ile Pro
Ala Lys Thr Pro Pro Ala Pro Lys Thr Pro Pro Ser Ser Gly 115 120
125Glu Pro Pro Lys Ser Gly Asp Arg Ser Gly Tyr Ser Ser Pro Gly Ser
130 135 140Pro Gly Thr Pro Gly Ser Arg Ser Arg Thr Pro Ser Leu Pro
Thr Pro145 150 155 160Pro Thr Arg Glu Pro Lys Lys Val Ala Val Val
Arg Thr Pro Pro Lys 165 170 175Ser Pro Ser Ser Ala Lys Ser Arg Leu
Gln Thr Ala Pro Val Pro Met 180 185 190Pro Asp Leu Lys Asn Val Lys
Ser Lys Ile Gly Ser Thr Glu Asn Leu 195 200 205Lys His Gln Pro Gly
Gly Gly Lys Val Gln Ile Val Tyr Lys Pro Val 210 215 220Asp Leu Ser
Lys Val Thr Ser Lys Cys Gly Ser Leu Gly Asn Ile His225 230 235
240His Lys Pro Gly Gly Gly Gln Val Glu Val Lys Ser Glu Lys Leu Asp
245 250 255Phe Lys Asp Arg Val Gln Ser Lys Ile Gly Ser Leu Asp Asn
Ile Thr 260 265 270His Val Pro Gly Gly Gly Asn Lys Lys Ile Glu Thr
His Lys Leu Thr 275 280 285Phe Arg Glu Asn Ala Lys Ala Lys Thr Asp
His Gly Ala Glu Ile Val 290 295 300Tyr Lys Ser Pro Val Val Ser Gly
Asp Thr Ser Pro Arg His Leu Ser305 310 315 320Asn Val Ser Ser Thr
Gly Ser Ile Asp Met Val Asp Ser Pro Gln Leu 325 330 335Ala Thr Leu
Ala Asp Glu Val Ser Ala Ser Leu Ala Lys Gln Gly Leu 340 345
3502381PRTHomo sapiens 2Met Ala Glu Pro Arg Gln Glu Phe Glu Val Met
Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys Asp Gln
Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr Asp Ala
Gly Leu Lys Glu Ser Pro Leu 35 40 45Gln Thr Pro Thr Glu Asp Gly Ser
Glu Glu Pro Gly Ser Glu Thr Ser 50 55 60Asp Ala Lys Ser Thr Pro Thr
Ala Glu Ala Glu Glu Ala Gly Ile Gly65 70 75 80Asp Thr Pro Ser Leu
Glu Asp Glu Ala Ala Gly His Val Thr Gln Ala 85 90 95Arg Met Val Ser
Lys Ser Lys Asp Gly Thr Gly Ser Asp Asp Lys Lys 100 105 110Ala Lys
Gly Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro Arg Gly Ala 115 120
125Ala Pro Pro Gly Gln Lys Gly Gln Ala Asn Ala Thr Arg Ile Pro Ala
130 135 140Lys Thr Pro Pro Ala Pro Lys Thr Pro Pro Ser Ser Gly Glu
Pro Pro145 150 155 160Lys Ser Gly Asp Arg Ser Gly Tyr Ser Ser Pro
Gly Ser Pro Gly Thr 165 170 175Pro Gly Ser Arg Ser Arg Thr Pro Ser
Leu Pro Thr Pro Pro Thr Arg 180 185 190Glu Pro Lys Lys Val Ala Val
Val Arg Thr Pro Pro Lys Ser Pro Ser 195 200 205Ser Ala Lys Ser Arg
Leu Gln Thr Ala Pro Val Pro Met Pro Asp Leu 210 215 220Lys Asn Val
Lys Ser Lys Ile Gly Ser Thr Glu Asn Leu Lys His Gln225 230 235
240Pro Gly Gly Gly Lys Val Gln Ile Val Tyr Lys Pro Val Asp Leu Ser
245 250 255Lys Val Thr Ser Lys Cys Gly Ser Leu Gly Asn Ile His His
Lys Pro 260 265 270Gly Gly Gly Gln Val Glu Val Lys Ser Glu Lys Leu
Asp Phe Lys Asp 275 280 285Arg Val Gln Ser Lys Ile Gly Ser Leu Asp
Asn Ile Thr His Val Pro 290 295 300Gly Gly Gly Asn Lys Lys Ile Glu
Thr His Lys Leu Thr Phe Arg Glu305 310 315 320Asn Ala Lys Ala Lys
Thr Asp His Gly Ala Glu Ile Val Tyr Lys Ser 325 330 335Pro Val Val
Ser Gly Asp Thr Ser Pro Arg His Leu Ser Asn Val Ser 340 345 350Ser
Thr Gly Ser Ile Asp Met Val Asp Ser Pro Gln Leu Ala Thr Leu 355 360
365Ala Asp Glu Val Ser Ala Ser Leu Ala Lys Gln Gly Leu 370 375
3803383PRTHomo sapiens 3Met Ala Glu Pro Arg Gln Glu Phe Glu Val Met
Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys Asp Gln
Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr Asp Ala
Gly Leu Lys Ala Glu Glu Ala 35 40 45Gly Ile Gly Asp Thr Pro Ser Leu
Glu Asp Glu Ala Ala Gly His Val 50 55 60Thr Gln Ala Arg Met Val Ser
Lys Ser Lys Asp Gly Thr Gly Ser Asp65 70 75 80Asp Lys Lys Ala Lys
Gly Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro 85 90 95Arg Gly Ala Ala
Pro Pro Gly Gln Lys Gly Gln Ala Asn Ala Thr Arg 100 105 110Ile Pro
Ala Lys Thr Pro Pro Ala Pro Lys Thr Pro Pro Ser Ser Gly 115 120
125Glu Pro Pro Lys Ser Gly Asp Arg Ser Gly Tyr Ser Ser Pro Gly Ser
130 135 140Pro Gly Thr Pro Gly Ser Arg Ser Arg Thr Pro Ser Leu Pro
Thr Pro145 150 155 160Pro Thr Arg Glu Pro Lys Lys Val Ala Val Val
Arg Thr Pro Pro Lys 165 170 175Ser Pro Ser Ser Ala Lys Ser Arg Leu
Gln Thr Ala Pro Val Pro Met 180 185 190Pro Asp Leu Lys Asn Val Lys
Ser Lys Ile Gly Ser Thr Glu Asn Leu 195 200 205Lys His Gln Pro Gly
Gly Gly Lys Val Gln Ile Ile Asn Lys Lys Leu 210 215 220Asp Leu Ser
Asn Val Gln Ser Lys Cys Gly Ser Lys Asp Asn Ile Lys225 230 235
240His Val Pro Gly Gly Gly Ser Val Gln Ile Val Tyr Lys Pro Val Asp
245 250 255Leu Ser Lys Val Thr Ser Lys Cys Gly Ser Leu Gly Asn Ile
His His 260 265 270Lys Pro Gly Gly Gly Gln Val Glu Val Lys Ser Glu
Lys Leu Asp Phe 275 280 285Lys Asp Arg Val Gln Ser Lys Ile Gly Ser
Leu Asp Asn Ile Thr His 290 295 300Val Pro Gly Gly Gly Asn Lys Lys
Ile Glu Thr His Lys Leu Thr Phe305 310 315 320Arg Glu Asn Ala Lys
Ala Lys Thr Asp His Gly Ala Glu Ile Val Tyr 325 330 335Lys Ser Pro
Val Val Ser Gly Asp Thr Ser Pro Arg His Leu Ser Asn 340 345 350Val
Ser Ser Thr Gly Ser Ile Asp Met Val Asp Ser Pro Gln Leu Ala 355 360
365Thr Leu Ala Asp Glu Val Ser Ala Ser Leu Ala Lys Gln Gly Leu 370
375 3804410PRTHomo sapiens 4Met Ala Glu Pro Arg Gln Glu Phe Glu Val
Met Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys Asp
Gln Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr Asp
Ala Gly Leu Lys Glu Ser Pro Pro 35 40 45Gln Thr Pro Thr Glu Asp Gly
Ser Glu Glu Pro Gly Ser Glu Thr Ser 50 55 60Asp Ala Lys Ser Thr Pro
Thr Ala Glu Glu Ala Gly Ile Gly Asp Thr65 70 75 80Pro Ser Leu Glu
Asp Glu Ala Ala Gly His Val Thr Gln Ala Arg Met 85 90 95Val Ser Lys
Ser Lys Asp Gly Thr Gly Ser Asp Asp Lys Lys Ala Lys 100 105 110Gly
Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro Arg Gly Ala Ala Pro 115 120
125Pro Gly Gln Lys Gly Gln Ala Asn Ala Thr Arg Ile Pro Ala Lys Thr
130 135 140Pro Pro Ala Pro Lys Thr Pro Pro Ser Ser Gly Glu Pro Pro
Lys Ser145 150 155 160Gly Asp Arg Ser Gly Tyr Ser Ser Pro Gly Ser
Pro Gly Thr Pro Gly 165 170 175Ser Arg Ser Arg Thr Pro Ser Leu Pro
Thr Pro Pro Thr Arg Glu Pro 180 185 190Lys Lys Val Ala Val Val Arg
Thr Pro Pro Lys Ser Pro Ser Ser Ala 195 200 205Lys Ser Arg Leu Gln
Thr Ala Pro Val Pro Met Pro Asp Leu Lys Asn 210 215 220Val Lys Ser
Lys Ile Gly Ser Thr Glu Asn Leu Lys His Gln Pro Gly225 230 235
240Gly Gly Lys Val Gln Ile Ile Asn Lys Lys Leu Asp Leu Ser Asn Val
245 250 255Gln Ser Lys Cys Gly Ser Lys Asp Asn Ile Lys His Val Pro
Gly Gly 260 265 270Gly Ser Val Gln Ile Val Tyr Lys Pro Val Asp Leu
Ser Lys Val Thr 275 280 285Ser Lys Cys Gly Ser Leu Gly Asn Ile His
His Lys Pro Gly Gly Gly 290 295 300Gln Val Glu Val Lys Ser Glu Lys
Leu Asp Phe Lys Asp Arg Val Gln305 310 315 320Ser Lys Ile Gly Ser
Leu Asp Asn Ile Thr His Val Pro Gly Gly Gly 325 330 335Asn Lys Lys
Ile Glu Thr His Lys Leu Thr Phe Arg Glu Asn Ala Lys 340 345 350Ala
Lys Thr Asp His Gly Ala Glu Ile Val Tyr Lys Ser Pro Val Val 355 360
365Ser Gly Asp Thr Ser Pro Arg His Leu Ser Asn Val Ser Ser Thr Gly
370 375 380Ser Ile Asp Met Val Asp Ser Pro Gln Leu Ala Thr Leu Ala
Asp Glu385 390 395 400Val Ser Ala Ser Leu Ala Lys Gln Gly Leu 405
4105412PRTHomo sapiens 5Met Ala Glu Pro Arg Gln Glu Phe Glu Val Met
Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys Asp Gln
Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr Asp Ala
Gly Leu Lys Glu Ser Pro Pro 35 40 45Gln Thr Pro Thr Glu Asp Gly Ser
Glu Glu Pro Gly Ser Glu Thr Ser 50 55 60Asp Ala Lys Ser Thr Pro Thr
Ala Glu Ala Glu Glu Ala Gly Ile Gly65 70 75 80Asp Thr Pro Ser Leu
Glu Asp Glu Ala Ala Gly His Val Thr Gln Ala 85 90 95Arg Met Val Ser
Lys Ser Lys Asp Gly Thr Gly Ser Asp Asp Lys Lys 100 105 110Ala Lys
Gly Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro Arg Gly Ala 115 120
125Ala Pro Pro Gly Gln Lys Gly Gln Ala Asn Ala Thr Arg Ile Pro Ala
130 135 140Lys Thr Pro Pro Ala Pro Lys Thr Pro Pro Ser Ser Gly Glu
Pro Pro145 150 155 160Lys Ser Gly Asp Arg Ser Gly Tyr Ser Ser Pro
Gly Ser Pro Gly Thr 165 170 175Pro Gly Ser Arg Ser Arg Thr Pro Ser
Leu Pro Thr Pro Pro Thr Arg 180 185 190Glu Pro Lys Lys Val Ala Val
Val Arg Thr Pro Pro Lys Ser Pro Ser 195 200 205Ser Ala Lys Ser Arg
Leu Gln Thr Ala Pro Val Pro Met Pro Asp Leu 210 215 220Lys Asn Val
Lys Ser Lys Ile Gly Ser Thr Glu Asn Leu Lys His Gln225 230 235
240Pro Gly Gly Gly Lys Val Gln Ile Ile Asn Lys Lys Leu Asp Leu Ser
245 250 255Asn Val Gln Ser Lys Cys Gly Ser Lys Asp Asn Ile Lys His
Val Pro 260 265 270Gly Gly Gly Ser Val Gln Ile Val Tyr Lys Pro Val
Asp Leu Ser Lys 275 280 285Val Thr Ser Lys Cys Gly Ser Leu Gly Asn
Ile His His Lys Pro Gly 290 295 300Gly Gly Gln Val Glu Val Lys Ser
Glu Lys Leu Asp Phe Lys Asp Arg305 310 315 320Val Gln Ser Lys Ile
Gly Ser Leu Asp Asn Ile Thr His Val Pro Gly 325 330 335Gly Gly Asn
Lys Lys Ile Glu Thr His Lys Leu Thr Phe Arg Glu Asn 340 345 350Ala
Lys Ala Lys Thr Asp His Gly Ala Glu Ile Val Tyr Lys Ser Pro 355 360
365Val Val Ser Gly Asp Thr Ser Pro Arg His Leu Ser Asn Val Ser Ser
370 375 380Thr Gly Ser Ile Asp Met Val Asp Ser Pro Gln Leu Ala Thr
Leu Ala385 390 395 400Asp Glu Val Ser Ala Ser Leu Ala Lys Gln Gly
Leu 405 4106441PRTHomo sapiens 6Met Ala Glu Pro Arg Gln Glu Phe Glu
Val Met Glu Asp His Ala Gly1 5 10 15Thr Tyr Gly Leu Gly Asp Arg Lys
Asp Gln Gly Gly Tyr Thr Met His 20 25 30Gln Asp Gln Glu Gly Asp Thr
Asp Ala Gly Leu Lys Glu Ser Pro Leu 35 40 45Gln Thr Pro Thr Glu Asp
Gly Ser Glu Glu Pro Gly Ser Glu Thr Ser 50 55 60Asp Ala Lys Ser Thr
Pro Thr Ala Glu Asp Val Thr Ala Pro Leu Val65 70 75 80Asp Glu Gly
Ala Pro Gly Lys Gln Ala Ala Ala Gln Pro His Thr Glu 85 90 95Ile Pro
Glu Gly Thr Thr Ala Glu Glu Ala Gly Ile Gly Asp Thr Pro 100 105
110Ser Leu Glu Asp Glu Ala Ala Gly His Val Thr Gln Ala Arg Met Val
115 120 125Ser Lys Ser Lys Asp Gly Thr Gly Ser Asp Asp Lys Lys Ala
Lys Gly 130 135 140Ala Asp Gly Lys Thr Lys Ile Ala Thr Pro Arg Gly
Ala Ala Pro Pro145 150 155 160Gly Gln Lys Gly Gln Ala Asn Ala Thr
Arg Ile Pro Ala Lys Thr Pro 165 170 175Pro Ala Pro Lys Thr Pro Pro
Ser Ser Gly Glu Pro Pro Lys Ser Gly 180 185 190Asp Arg Ser Gly Tyr
Ser Ser Pro Gly Ser Pro Gly Thr Pro Gly Ser 195 200 205Arg Ser Arg
Thr Pro Ser Leu Pro Thr Pro Pro Thr Arg Glu Pro Lys 210 215 220Lys
Val Ala Val Val Arg Thr Pro Pro Lys Ser Pro Ser Ser Ala Lys225 230
235 240Ser Arg Leu Gln Thr Ala Pro Val Pro Met Pro Asp Leu Lys Asn
Val 245 250 255Lys Ser Lys Ile Gly Ser Thr Glu Asn Leu Lys His Gln
Pro Gly Gly 260 265 270Gly Lys Val Gln Ile Ile Asn Lys Lys Leu Asp
Leu Ser Asn Val Gln 275 280 285Ser Lys Cys Gly Ser Lys Asp Asn Ile
Lys His Val Pro Gly Gly Gly 290 295 300Ser Val Gln Ile Val Tyr Lys
Pro Val Asp Leu Ser Lys Val Thr Ser305 310 315 320Lys Cys Gly Ser
Leu Gly Asn Ile His His Lys Pro Gly Gly Gly Gln 325 330 335Val Glu
Val Lys Ser Glu Lys Leu Asp Phe Lys Asp Arg Val Gln Ser 340 345
350Lys Ile Gly Ser Leu Asp Asn Ile Thr His Val Pro Gly Gly Gly Asn
355 360 365Lys Lys Ile Glu Thr His Lys Leu Thr Phe Arg Glu Asn Ala
Lys Ala 370 375 380Lys Thr Asp His Gly Ala Glu Ile Val Tyr Lys Ser
Pro Val Val Ser385 390 395 400Gly Asp Thr Ser Pro Arg His Leu Ser
Asn Val Ser Ser Thr Gly Ser 405 410 415Ile Asp Met Val Asp Ser Pro
Gln Leu Ala Thr Leu Ala Asp Glu Val 420 425 430Ser Ala Ser Leu Ala
Lys Gln Gly Leu 435 440742PRTHomo sapiens 7Asp Ala Glu Phe Arg His
Asp Ser Gly Tyr Glu Val His His Gln Lys1 5 10 15Leu Val Phe Phe Ala
Glu Asp Val Gly Ser Asn Lys Gly Ala Ile Ile 20 25 30Gly Leu Met Val
Gly Gly Val Val Ile Ala 35 40
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References