U.S. patent application number 10/763286 was filed with the patent office on 2006-01-19 for synthetic or natural peptides binding protein phosphatase 2a, identification method and uses.
This patent application is currently assigned to INSTITUT PASTEUR. Invention is credited to Xavier Cayla, Alphonse Garcia, Gordon Langsley, Angelita Rebollo.
Application Number | 20060014930 10/763286 |
Document ID | / |
Family ID | 8866042 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060014930 |
Kind Code |
A1 |
Garcia; Alphonse ; et
al. |
January 19, 2006 |
Synthetic or natural peptides binding protein phosphatase 2A,
identification method and uses
Abstract
The present invention relates to novel synthetic or natural
peptides for use in treating viral or parasitic infections or in
the treatment of tumors. The peptides of the present invention are
less than 30 amino acids in size, preferably less than 20 amino
acids, in particular 15 to 20 amino acids, and in vitro the
peptides specifically bind a type 2A protein phosphatase holoenzyme
or one of its subunits. The invention also relates to a method for
identifying said peptides, and to their uses.
Inventors: |
Garcia; Alphonse;
(Montrouge, FR) ; Cayla; Xavier; (Rochecorbon,
FR) ; Rebollo; Angelita; (Madrid, ES) ;
Langsley; Gordon; (Paris, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
INSTITUT PASTEUR
Paris
FR
Institut National de la Recherche Agronomique
Paris Cedex
FR
CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Madrid
ES
Centre National De La Recherche Scient.
Paris Cedex
FR
|
Family ID: |
8866042 |
Appl. No.: |
10/763286 |
Filed: |
January 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/FR02/02705 |
Jul 26, 2002 |
|
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10763286 |
Jan 26, 2004 |
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Current U.S.
Class: |
530/326 ;
530/327; 530/328 |
Current CPC
Class: |
A61P 43/00 20180101;
A61P 35/00 20180101; A61P 33/00 20180101; A61P 31/18 20180101; C12N
2740/16322 20130101; A61P 31/12 20180101; Y02A 50/412 20180101;
A61K 38/00 20130101; Y02A 50/467 20180101; A61P 33/06 20180101;
A61P 33/02 20180101; Y02A 50/30 20180101; A61K 39/00 20130101; C07K
14/005 20130101; Y02A 50/41 20180101 |
Class at
Publication: |
530/326 ;
530/327; 530/328 |
International
Class: |
A61K 38/10 20060101
A61K038/10; C07K 7/08 20060101 C07K007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 2001 |
FR |
01/10139 |
Claims
1. A peptide less than 30 amino acids in size, preferably less than
20 amino acids, characterized in that in vitro, it specifically
binds a type 2A protein phosphatase holoenzyme or one of its
subunits.
2. A peptide according to claim 1, characterized in that it is a
fragment of a viral, parasitic or cellular protein, said protein
binding a type 2A protein phosphatase in vitro, or a sequence that
is distinguished from the preceding protein fragment by
substitution or deletion of amino acids, said distinct sequence
nevertheless conserving the properties of binding to the type 2A
protein phosphatase or one of its subunits.
3. A peptide according to claim 2, characterized in that said
viral, parasitic or cellular protein is selected from one of the
following proteins: the t antigen of SV40 or polyoma, the middle t
antigen of polyoma, the type B (B, B', B'') subunit of PP2A, CXCR2
(chemokine receptor), CK2.alpha., CaMIV, p70S6-kinase, Pak1/Pak3,
Tap42/alpha 4, PTPA, Set/I1/I2-PP2A, E4orf4, tau, CD28 or Vpr.
4. A peptide according to claim 3, characterized in that it is a
fragment of the CD28 protein selected from one of the following
peptide sequences: a) PRRPGPTRKHY (SEQ ID No: 132); or b) a
sequence distinguished from the sequence envisaged in a) by
substitution or deletion of amino acids, said sequence nevertheless
conserving the properties of binding to type 2A protein phosphatase
or one of its subunits.
5. A peptide according to claim 3, characterized in that said
viral, parasitic or cellular protein is the Vpr protein of the HIV
virus.
6. A peptide according to claim 5, characterized in that said Vpr
protein is derived from the HIV-1 or HIV-2 virus.
7. A peptide according to claim 6, characterized in that it is
selected from one of the following peptide sequences: a)
RRRRRRRSRGRRRRTY (SEQ ID No: 140); or b) a sequence distinguished
from the sequence envisaged in a) by substitution or deletion of
amino acids, said sequence nevertheless conserving the properties
of binding to type 2A protein phosphatase or one of its
subunits.
8. A peptide according to claim 6, characterized in that it is
included in one of the following sequences: a) VEALIRILQQLLFIHFRI
(SEQ ID No: 1); b) RHSRIGIIQQRRTRNG (SEQ ID No: 2); or a sequence
that is distinguished from SEQ ID No: 1 or SEQ ID No: 2 by
substitution or deletion of amino acids, said distinct sequence
nevertheless conserving the properties of binding to type 2A
protein phosphatase or one of its subunits.
9. A peptide according to claim 8, characterized in that it is the
sequence RHSRIGVTRQRRARNG (SEQ ID No: 139).
10. A peptide according to claim 8, characterized in that it
consists of the sequence RHSRIG (SEQ ID No: 135).
11. A peptide according to any one of claims 1 to 10, characterized
in that its administration induces apoptosis of tumor cells.
12. A peptide according to claim 3, characterized in that said
viral, parasitic or cellular protein is the CK2.alpha. protein.
13. A peptide according to claim 12, characterized in that said
CK2.alpha. protein is derived from the Theileria parva
parasite.
14. A peptide according to claim 12 or claim 13, characterized in
that its administration reduces parasitic development.
15. A peptide according to any one of claims 12 to 14,
characterized in that it is included in one of the following
sequences: a) RKIGRGKFSEVFEG (SEQ ID No: 3); b)
TVTKDCVIKILKFPVKKKKIKREIKILQNL (SEQ ID No: 4); c) KILRLIDWGLAEFYHP
(SEQ ID No: 5); or d) a homologous sequence of SEQ ID No: 3, SEQ ID
No: 4 or SEQ ID No: 5 derived from P falciparum or leishmania; or a
sequence deriving from the sequences mentioned above by
substitution or deletion of amino acids, said distinct sequence
nevertheless conserving the properties of binding to type 2A
protein phosphatase or one of its subunits, and in particular the
sequence TVTKDKCVIKILKPVKKKKIIKILQNL.
16. A peptide according to claim 15, characterized in that it is
the peptide RQKRLI (SEQ ID No: 141).
17. A peptide according to one of claims 1 to 16, characterized in
that it competitively inhibits interaction of the native protein
from which it is derived with a PP2A holoenzyme or one of its
subunits.
18. A peptide according one of claims 1 to 17, characterized in
that it is coupled to a vector that is capable of transferring said
peptide to a eukaryotic cell.
19. A polypeptide, characterized in that it is constituted by a
repeat of a peptide according to any one of claims 1 to 13.
20. A polypeptide according to claim 19, characterized in that it
is selected from one of the following sequences: a) (RHSRIG).sub.2
(SEQ ID No: 136); b) (RHSRIG).sub.3 (SEQ ID No: 137); or c)
(RQKRLI).sub.3 (SEQ ID No: 134).
21. A polynucleotide characterized in that its sequence consists of
the sequence encoding a peptide according to any one of claims 1 to
20.
22. A polynucleotide, characterized in that its sequence is
selected from one of the following sequences: SEQ ID No: 26, 27,
28, 29 or 30.
23. A polynucleotide, characterized in that it consists of a
multimer of polynucleotide according to claim 21 or claim 22.
24. A cellular expression vector, characterized in that it
comprises a polynucleotide according to one of claims 21 to 23 and
regulatory sequences allowing expression of a peptide according to
any one of claims 1 to 20 in a host cell.
25. A purified polyclonal or monoclonal antibody, characterized in
that it is capable of specifically binding anyone of the peptides
according to one of claims 1 to 20.
26. A pharmaceutical composition comprising a peptide according to
one of claims 1 to 20, in combination with a pharmaceutically
acceptable vehicle.
27. A pharmaceutical composition comprising an element selected
from a polypeptide according to one of claims 21 to 23, an
expression vector according to claim 24 or an antibody according to
claim 25.
28. A peptide, characterized in that it is selected from one of the
following sequences: SEQ ID No: 137; SEQ ID No: 139; SEQ ID No:
140.
29. A peptide, characterized in that it has sequence SEQ ID No:
20.
30. Use of a peptide or polypeptide as defined in any one of claims
1 to 20, 28 or 29, in preparing a drug for treating a viral or
parasitic infection.
31. Use of a peptide or polypeptide as defined in any one of claims
5 to 10, 28 or 29, in preparing a drug that can inhibit infection
by HIV.
32. Use of a peptide as defined in one of claims 5 to 20 or 28, in
preparing a drug that may induce apoptosis of target cells, and in
particular tumor cells.
33. Use of a peptide as defined in any one of claims 12 to 16, in
preparing a drug that can inhibit parasitic infection.
34. Use of a peptide as defined in any one of claims 12 to 16, in
preparing a drug for use in treating malaria.
35. Use of a polynucleotide according to one of claims 21 to 23 or
an antibody according to claim 25, in the in vitro diagnosis of
parasitic or viral diseases.
36. A method for identifying a peptide the sequence of which is
derived from a viral, parasitic or cellular protein, said peptide
specifically binding a type 2A protein phosphatase holoenzyme or
one of its subunits, said method comprising the steps consisting
of: a) depositing, in the form of spots on a support, peptides the
sequence of which is derived from a viral, parasitic or cellular
protein, each spot corresponding to the deposit of a peptide with a
defined sequence; b) bringing the solid support into contact with a
solution containing the protein phosphatase 2A holoenzyme or one of
its subunits under conditions that allow the peptides present on
the support to bind the holoenzyme or one of its subunits; and c)
identifying on the solid support the peptide to which the protein
phosphatase 2A or one of its subunits is bound.
37. A method according to claim 36, characterized in that the size
of the peptides deposited in the form of a spot is less than 20
amino acids, preferably less than 15 amino acids.
38. A method according to any one of claims 36 or 39, characterized
in that the peptides are deposited on a cellulose membrane.
39. A method according to any one of claims 36 to 40, characterized
in that the series of deposited peptide sequences covers the
complete sequence of the viral, parasitic or cellular protein from
which those sequences are derived.
40. A method for preparing a peptide as defined in any one of
claims 1 to 20, 28 or 29, comprising transforming a host cell using
a cellular expression vector as defined in claim 24, followed by
culturing the transformed host cell and recovering the peptide in
the culture medium.
Description
[0001] The invention relates to novel synthetic or natural
peptides, in particular for use in treating viral or parasitic
infections or in the treatment of tumors, said peptides being less
than 30 amino acids in size, preferably less than 20 amino acids,
in particular 15 to 20 amino acids, and characterized in that in
vitro, they specifically bind a type 2A protein phosphatase
holoenzyme or one of its subunits. The invention also relates to a
method for identifying said peptides, and to their uses.
[0002] Given the role of the peptides of the invention in
modulating the activity of cellular protein phosphatase 2A, it is
important in the introduction to recall the current knowledge
regarding protein phosphatase 2As, their physiological role and
their interactions with certain cellular, viral or parasitic
proteins.
[0003] Cell physiology is partially controlled by modulating
protein phosphorylation. The phosphorylation state of cell proteins
depends on the antagonist action of protein kinases which
phosphorylates them and protein phosphatases which dephosphorylate
them.
[0004] Protein phosphatases are divided into two principal groups:
tyrosine phosphatases and serine/threonine phosphatases.
Serine/threonine phosphatases are classified into two categories
which depend on the specificicity of their substrate and their
sensitivity to certain inhibitors, namely type 1 phosphatases (PP1)
and type 2 phosphatases (PP2). Type 2 phosphatases are themselves
divided into different classes, including phosphatase 2A (PP2A),
phosphatase 2B or calcineurine the activity of which is regulated
by calcium, and phosphatase 2C (PP2C) the activity of which is
regulated by magnesium.
[0005] It is now known that type 2A phosphatases are highly
conserved during evolution and are potentially involved in
regulating many biological processes. PP2A enzymes have been
clearly involved in regulating transcription, control of the cell
cycle or viral transformation. Further, PP2As are targeted by
different viral or parasitic proteins, suggesting a role for PP2As
in, host-pathogen interactions.
[0006] PP2As are oligomeric complexes (holoenzymes) each comprising
a catalytic subunit (C) and one or two regulating subunits (A) and
(B). The structure of subunit (A) consists of 15 imperfect repeats
of a conserved amino acid sequence of 38 to 40 amino acids, certain
of which interact with subunits (B) and (C). Subunits (A) and (C),
conserved during evolution, constitute the base structure of the
enzyme and are expressed constitutively. In contrast, subunits (B)
constitute a family of regulating proteins not connected via a
common structure and expressed differentially (Cohen P. The
structure and regulation of protein phosphatases. Annu Rev Biochem
1989; 58: 453-508). Protein phosphatase 2As exist in vivo in two
classes with different forms: a dimeric form (AC) and a trimeric
form (ABC). Subunits (B) regulate phosphatase activity and
specificity towards the substrate. The existence of multiple forms
of PP2A is correlated with the distinct and varied functions of
PP2A in vivo.
[0007] Recently, different proteins synthesized by pathogens, in
particular viral and parasitic proteins, have been implicated in
modulating certain specific activities of protein phosphatase
2A.
[0008] Different strategies involving PP2A have been adopted by
viruses to facilitate their replication and survival in a host
cell. As an example, parainfluenza virus incorporates the protein
PKC.zeta., a protein of cellular origin under the control of PP2A,
into its viral particle. This can perturb the phosphoylation of
host proteins and facilitate its own replication (De B P, Gupta S,
Barnejee A K. Cellular protein kinase C .zeta. regulates human
parainfluenza virus type 3 replication. Proc. Natl Acad Sci USA
1995; 92: 5204-8).
[0009] Several DNA viruses with transforming power, such as papovae
or adenoviruses, as well as certain retroviruses such as the type-1
human immunodeficiency virus (HIV-1), code for proteins which
interact directly with certain host PP2As. All of those viruses
comprise proteins which, although structurally different, interact
with certain holoenzymes and modify phosphatase activity.
[0010] In particular, it has been shown that the E4orf4 protein of
adenoviruses binds to a heterotrimeric PP2A and more precisely to a
regulating subunit (B), which causes a reduction in the
transcription of JunB in the infected cell. That effect could play
an important role during viral infection by regulating the
apoptotic response of infected cells. Interestingly, it has also
been shown that the interaction of E4orf4 with PP2A induces
apoptosis in transformed cells in a p53-independent manner
(Shtrichman R et al, Adenovirus type 5 E4 open reading frame 4
protein induces apoptosis in transformed cells. J Virol 1998; 72:
2975-82).
[0011] Tumor-generating viruses of the Papovae family, including
SV40 and polyoma virus, induce cell transformation. It has been
shown that PP2A interacts with the "small T" antigen of SV40 or
polyoma and with the transforming "middle T" protein of polyoma.
Those interactions of viral proteins with PP2A have been clearly
involved in viral transformation. Finally, transcriptional
regulation, a process normally carried out in the cell by different
factors specifically fixing to promoter regulating sequences,
probably represents the most important mechanism involved in the
control of viral expression by PP2A. It has been demonstrated that
PP2A is a negative regulator for numerous transcription factors
involved in particular in the processes of cell growth and
proliferation, including AP1/SRE, NF-.kappa.B, Sp1 and CREB
(Waszinski, B E, Wheat W H, Jaspers S, Peruski L F, J R Lickteig R
L, Johnson G L, and Klemm D J, Nuclear protein phosphatase 2A
dephosphorylates protein kinase A-phosphorylated CREB and regulates
CREB transcriptional stimulation. Mol Cell Biol 1993 13, 2822-34).
Viral regulation of those transcription factors would permit
modulation of viral transcription.
[0012] The viral protein of HIV-1, Vpr, interacts in vitro with
PP2A and stimulates the catalytic activity of PP2A (Tung L et al,
Direct activation of protein phosphatase 2A0 by HIV-1 encoded
protein complex Ncp7: vpr. FEBS Lett 1997; 401: 197-201). Vpr can
induce the G2 stoppage of infected cells by inhibiting the
activation of the p34cdc2-cycline B complex. Further, Vpr interacts
with the transcription factor Sp1 and is a weak trans-activator for
transcription of Sp1 dependent HIV-1. Thus, the Vpr protein of
HIV-1, which is incorporated into the virion, should be involved in
vivo in the initiation of viral transcription, a step that is
clearly essential for regulating the expression of the Tat
transcription factor (a major regulator of transcription encoded by
the HIV-1 virus).
[0013] In contrast to the well established role of protein kinases
in parasitic infections, it is only during the past three years
that serine/threonine phosphatases have begun to be recognized as
being important potential regulators in the field of
parasitology.
[0014] Initially, two serine/threonine phosphatases, Pp.beta. and
PfPP, were identified in Plasmodium falciparum. The presence of
type 1 and type 2A phosphatase activity in the parasite has been
demonstrated by enzymological studies. Finally, parasitic enzymes
PP2A and PP2B were purified.
[0015] Serine/threonine phosphatases have recently been studied in
Theileria parva, another protozoan close to P. falciparum, a cattle
parasite. Monocyte and leukocyte host cells infected by the
parasite are transformed, resulting in leukemia in the animal.
Purified parasites of cells infected with Theileria express a
protein kinase CK2.alpha.. Now, the subunit CK2.alpha. should
interact with PP2A to positively modulate its activity (Heriche H,
et al, Regulation of protein phosphatase 2A by direct interaction
with casein kinase 2.alpha.. Science 1997; 276-952-5). Further,
modulation of PP2A via expression of the CK2.alpha. subunit could
be the basis of blockage of two signal routes in the parasitised
cell, that of MAP-kinases (Chaussepied M et al. Theileria
transformation of bovine leukocytes: a parasite model for the study
of lymphoproliferation. Res Immunol 1996; 147: 127-38) and that of
protein kinase B (Akt) (M Baumgartner, M Chaussepied, M F Moreau, A
Garcia, G Langsley. Constitutive PI3-K activity is essential for
proliferation, but not survival, of Theileria parva--transformed B
cells. Cellular Microbiol (2000) 2, 329-339).
[0016] The absence of common motifs to the series of proteins
interacting with PP2A prevents the informatical identification of
peptide motifs directly involved in binding those proteins with
PP2A.
[0017] Given the major role of protein phosphatase 2As in
virus-host interactions or parasite-host interactions as summarized
above, the importance of identifying the binding sites of viral or
parasitic proteins with PP2A holoenzymes or one of their subunits
can be understood, so that novel therapeutic targets for those
viral or parasitic pathogens can be identified.
[0018] In particular, the identification of peptides interacting
with PP2A should allow novel drugs to be developed that can block,
by competitive inhibition, the cell mechanisms induced by viral or
parasitic proteins via their interaction with PP2A and in
particular mechanisms of infection, pathogen proliferation and cell
transformation.
[0019] The invention pertains to means for identifying peptides of
reduced size, binding a PP2A holoenzyme or one of its subunits. In
contrast to native proteins or polypeptide domains of large size,
reduced size peptides have the advantage of being readily
synthesized, either chemically or in cell systems, in high yields
and cheaply. The peptides of the invention are also more stable and
more readily transferred into the cytoplasm or into the nucleus of
cells using appropriate vectors, with a view to therapeutic
use.
[0020] The invention derives from the demonstration that it is
possible to identify peptides with a size of less than 30 amino
acids, and in particular peptides less than 20 amino acids in size,
interacting with a PP2A holoenzyme or one of its subunits.
[0021] In particular, the inventors have shown that using a "SPOT
synthesis" technique as described by Frank and Overwing (Methods in
Molecular Biology, 1996, vol 66: 149-169, Epitope Mapping Protocols
edited by: G E Morris Humana Press Inc, Totowa N.J.) allows binding
sites for proteins interacting with a PP2A holoenzyme or one of its
subunits to be identified.
[0022] As an example, the inventors have identified peptides less
than 20 amino acids in size interacting in vitro with purified PP2A
holoenzyme or one of its subunits, said peptides being derived from
the Vpr protein of HIV-1 or the CK2.alpha. protein of the T parva
parasite. Antagonists derived from these peptides and selected
because they inhibit the interaction of viral or parasititc
proteins with a particular PP2A holoenzyme could then constitute
novel anti-tumoural, antiviral or antiparasitic agents.
[0023] The invention concerns a method for identifying a peptide
the sequence of which is derived from a viral, parasitic or
cellular protein, said peptide specifically binding a type, 2A
protein phosphatase holoenzyme or one of its subunits, said method
comprising the steps consisting of: [0024] a) depositing, in the
form of spots onto a support, peptides the sequence of which is
derived from a viral, parasitic or cellular protein, each spot
corresponding to the deposit of a peptide with a defined sequence;
[0025] b) bringing the solid support into contact with a solution
containing the protein phosphatase 2A holoenzyme or on of its
subunits under conditions that allow the peptides present on the
support to bind the holoenzyme or one of its subunits; and [0026]
c) identifying on the solid support the peptide to which the
protein phosphatase 2A or one of its subunits is bound.
[0027] In step a), different peptides are deposited on a solid
support in defined positions ("spot"), each position corresponding
to a specific peptide sequence and the series then forming a
two-dimensional array of peptides. Different methods for preparing
such arrays have recently been described (for a review, see Figeys
and Pinto, 2001, Electrophoresis 22: 208-216; Walter et al, 2000,
Curr Opin Microbiol 3: 298-302). The series of these methods
generally include covalently fixing the peptides on a support, in
particular using chemical linkers. As an example, the skilled
person could refer to the "SPOT synthesis" technique consisting of
directly synthesizing peptides comprising up to 20 residues on a
cellulose membrane (Frank and Overwing, Methods in Molecular
Biology, 1996, vol 66: 149-169, Epitope Mapping Protocols, edited
by: G E Morris, Humana Press Inc, Totowa N.J.).
[0028] In general, any method can be used provided that it can
produce an array of peptides deposited on a solid support that can
be used to detect specific interactions between the deposited
peptides and particular compounds.
[0029] Highly preferably, the series of deposited peptide sequences
covers the complete sequence of the viral, parasitic or cellular
protein from which those sequences are derived. Thus, the process
can test, in a single step, the complete sequence of a given
protein, this being "sectioned" into a finite number of peptides
with generally overlapping sequences.
[0030] In a preferred implementation, the peptides deposited in the
form of a spot are less than 20 amino acids in size, and more
preferably are less than 15 amino acids in size.
[0031] In another particular implementation, the peptides are
deposited on a cellulose membrane.
[0032] The array obtained is brought into contact in step b) with a
type 2A protein phosphatase holoenzyme or one of its subunits.
[0033] The term "type 2A protein phosphatase holoenzyme" means any
purified dimeric (AC) or heterotrimeric (ABC) complex of a cellular
or reconstituted extract after purifying two subunits (A) and (C)
of a type 2A protein phosphatase and if necessary a subunit (B).
The type 2A protein phosphatases are preferably derived from
mammals.
[0034] The supports are incubated, for example, in a buffer
solution comprising purified protein phosphatase or one of its
purified subunits. A suitable buffer solution is TBS (TRIS BORATE)
containing 5% of skimmed Regilait (milk) and 3% of BSA.
[0035] The peptide onto which the type 2A protein phosphatase
holoenzyrne is bound is generally identified by direct or indirect
labeling of the protein phosphatase and identifying the spots to
which the labeled protein has bound. Binding of PP2A or one of its
subunits to one of the peptide spots can then be revealed, in
particular using antiserums, using techniques that are
conventionally used for Western Blot or solid phase ELISA test,
after incubating the support containing the peptide array with an
antibody directed against subunits (A) or (B) or (C) or a mixture
of antibodies directed against subunits (A), (B) or (C) of
PP2A.
[0036] The method of the invention can be applied to identifying
peptides, in particular for use in treating certain viral or
parasitic infections, measuring less than 30 amino acids in size or
even less than 20 amino acids, said peptides being capable of
binding a type 2A protein phosphatase holoenzyme or one of its
subunits in vitro.
[0037] Further, by using general knowledge in the peptide synthesis
field, the skilled person can produce peptides derived from
fragments of peptides identified by the method of the invention
having the advantageous properties described above.
[0038] As a result, the invention provides a natural or synthetic
peptide measuring less than 30 amino acids, preferably less than 20
amino acids, characterized in that in vitro, it specifically binds
a type 2A protein phosphatase holoenzyme or one of its subunits
(A), (B) or (C). The term "specifically binds" means that the
peptide is capable of competitively inhibiting binding of a protein
of viral or parasitic origin with PP2As.
[0039] In a preferred implementation of the invention, the peptide
of the invention is characterized in that it is a fragment of a
viral, parasitic or cellular protein, said protein binding in vitro
a type 2A protein phosphatase or one of its subunits, or a sequence
that is distinguished from the preceding protein fragment by
substitution or deletion of amino acids, said distinct sequence
nevertheless conserving the properties of binding to the type 2A
protein phosphatase or one of its subunits. Preferably, the number
of amino acids substituted or deleted from the distinct sequence
compared with the initial sequence does not exceed 20%, more
preferably 10% of the amino acids number constituting the initial
sequence. Preferably, only amino acids the deletion of which does
not affect the in vitro binding properties of the peptide to PP2A
are substituted or deleted.
[0040] In particular, one distinct sequence is a peptide sequence
increasing the binding affinity to type 2A protein phosphatase or
one of its subunits compared with the sequence from which it is
derived. A further distinct sequence as defined above is a peptide
sequence homologous with an initially identified peptide sequence.
The term "homologous peptide" as used in the present invention
means a sequence derived from a protein of species other than the
initially identified peptide sequence, and for which the primary
sequence can be aligned with the peptide sequence initially
identified using a conventional optimum alignment program such as
the BESTFIT program (Wisconsin Genetics Software Package, Genetics
Computer Group, GCG). In particular, a sequence A will be
considered to be homologous with a sequence B if said sequences A
and B have at least 50% identity, preferably 75% identity after
aligning the sequences using an optimum alignment program such as
the BESTFIT program. Preferably again, two sequences are also
considered to be homologous if the sequences are quasi-identical,
with the exception of a few residues that can represent 10% to 20%
variability over the whole sequence. Further, amino acids with the
same chemical function (such as Arg and Lys) are considered to be
equivalent. The peptides to be analyzed for their binding with a
PP2A or one of its subunits are generally selected from fragments
of viral, parasitic or cellular proteins, which proteins have been
shown to interact in vivo or in vitro with a type 2A protein
phosphatase.
[0041] In particular, such viral parasitic or cellular proteins are
selected from one of the following proteins: the t antigen of SV40
or polyoma, the middle t antigen of polyoma, the type B (B, B',
B'') subunit of PP2A, CK2.alpha., CaMIV, p70S6-kinase, Pak1/Pak3,
Tap42/alpha 4, PTPA, Set/I1/I2-PP2A, E4orf4, tau, Vpr or CD28,
CCXR2 (chemokine receptor).
[0042] A preferred peptide of the invention is a fragment of the
CD28 protein, and in particular peptides constituted by the
sequences PRRPGPTRKHY (SEQ ID No: 132) and (PRRPGPTRK).sub.2 (SEQ
ID No: 133), respectively corresponding to the peptides termed FD2
and FD3 the intracellular penetration capacity and effects on cell
viability of which are described below in the experimental section.
The present invention also pertains to peptide sequences that are
distinguished from the preceding protein by substitution or
deletion of amino acids, said distinct sequences nevertheless
conserving the properties of binding to type 2A protein phosphatase
or one of its subunits.
[0043] A particularly preferred peptide of the invention is a
fragment of the Vpr protein of the HIV virus, in particular a
fragment of the Vpr protein of the HIV-1 or HIV-2 virus, or a
sequence that is distinguished from the preceding protein fragment
by substitution or deletion of amino acids, said distinct sequence
nevertheless conserving the properties of binding to type 2A
protein phosphatase or one of its subunits. The invention does not
encompass the peptide, a fragment of the Vpr protein having the
following sequence: LFIHFRIGCQHSRIGITRRRRVRDGSSRP* disclosed in the
EMBL database, accession number P89821. In contrast, using said
peptide in the context of the applications described below falls
within the scope of the present invention.
[0044] Special examples of peptides derived from a protein which
interacts with type 2A protein phosphatase derived from protamine
that can be cited are the peptide with sequence RRRRRRRSRGRRRRTY
(SEQ ID No: 140, termed FD8) or a sequence that is distinguished
from SEQ ID No: 140 by substitution or deletion of amino acids,
said distinct sequence nevertheless conserving the properties of
binding to type 2A protein phosphatase or one of its subunits.
[0045] Preferably again, a peptide of the invention is
characterized in that it is included in one of the following
sequences: [0046] a) VEALIRILQQLLFIHFRI (SEQ ID No: 1); [0047] b)
RHSRIGIIQQRRTRNG (SEQ ID No: 2); or [0048] c) a sequence that is
distinguished from SEQ ID No: 1 or SEQ ID No: 2 by substitution or
deletion of amino acids, said distinct sequence nevertheless
conserving the properties of binding to type 2A protein phosphatase
or one of its subunits.
[0049] A particularly preferred peptide of the invention is a
fragment of the peptide SEQ ID No: 2, said fragment consisting of
or comprising the peptide with sequence RHSRIG (SEQ ID No: 135),
termed FD9, the capacity for intracellular penetration and the
effect on cell viability of which are described below in the
experimental section.
[0050] The invention also concerns a compound with a polypeptide
framework containing a peptide of the invention as defined above,
said compound having a molecular weight in the range 10 to 150
Kdaltons and having the capacity to bind protein phosphatase
2A.
[0051] The invention also concerns a polypeptide, characterized in
that it is constituted by a repeat of a peptide of the
invention.
[0052] Particular examples of such polypeptides are the peptide
RHSRIG polymers, and in particular the dimer (RHSRIG).sub.2 (SEQ ID
No: 136) or the trimer (RHSRIG).sub.3 (SEQ ID No: 137),
respectively termed FD10 and FD11, the capacity for intracellular
penetration and the effect on cell viability of which are described
below in the experimental section.
[0053] Peptides with sequences that are distinguished from SEQ ID
No: 1 or SEQ ID No: 2 by substitution or deletion of amino acids
and falling within the scope of the invention that can in
particular be cited peptides the sequence of which is included in
one of the sequences for the Vpr protein of different variants of
type HIV-1, HIV-2 and SIV, corresponding to homologous sequences in
variants of SEQ ID No: 1 or SEQ ID No: 2.
[0054] The following sequences can be cited: VEALIRILQQLL (SEQ ID
No: 6), ALIRILQQLLFI (SEQ ID No: 7), IRILQQLLFIHF (SEQ ID No: 8),
ILQQLLFIHFR (SEQ ID No: 9), RHSRIGIIQQRR (SEQ ID No: 10),
SRIGIIQQRRTR (SEQ ID No: 11) and IGIIQQRRTRNG (SEQ ID No: 12)
corresponding to dodecapeptides identified as binding the subunit A
of PP2A.
[0055] A particular sequence of the invention that is distinguished
from SEQ ID No: 2 by deletion or substitution of amino acids is the
sequence RHSRIGVTRQRRARNG (SEQ ID No: 139), also termed FD13 in the
experimental section described below.
[0056] A preferred peptide of the invention is a peptide selected
from sequences SEQ ID No: 1 and SEQ ID No: 2 and is characterized
in that its administration induces apoptosis of tumour cells.
[0057] One method for selecting peptides that can induce tumour
cell apoptosis can be implemented, for example, using the MTT
viability test described in the experimental section.
[0058] A further preferred implementation of the invention provides
a peptide characterized in that it derives from a fragment of the
CK2.alpha. protein. In particular, the natural or synthetic peptide
is characterized in that it derives from a fragment of the
CK2.alpha. protein of the Theileria parva parasite.
[0059] More preferably, a peptide of the invention is characterized
in that it is included in one of the following sequences: [0060] a)
RKIGRGKFSEVFEG (SEQ ID No: 3); [0061] b)
TVTKDCVIKILKPVKKKKIKREIKILQNL (SEQ ID No: 4); [0062] c)
KILRLIDWGLAEFYHP (SEQ ID No: 5); [0063] d) a homologous sequence of
SEQ ID No: 3, SEQ ID No: 4 or SEQ ID No: 5 derived from P
falciparum or Leishmania; or [0064] e) a sequence deriving from the
sequences mentioned above by substitution or deletion of amino
acids, said distinct sequence nevertheless conserving the
properties of binding to protein phosphatase 2A or one of its
subunits, and in particular the sequence
TVTKDKCVIKILKPVKKKKIKEIKILQNL (SEQ ID No: 142).
[0065] Among peptides that are distinguished from sequences SEQ ID
No: 3, 4 or 5 that can be cited are sequences from site 1
(RKIGRGKFSEVFEG) (SEQ ID No: 3), in particular the peptide with the
sequence RKIGRGKFSEVF and the peptide with sequence IGRGKFSEVFEG or
sequences from site 2 (TVTKDKCVIKILKPVKKKKIKRIKILQNL) (SEQ ID No:
4), in particular the following peptides: TABLE-US-00001
TVTKDKCVIKIL; (SEQ ID No: 13) TKDKCVIKLLKP; (SEQ ID No: 14)
DKCVIKILKPVK; (SEQ ID No: 15) CVIKILKPVKKK; (SEQ ID No: 16)
IKILKPVKKKKI; (SEQ ID No: 17) ILKPVKKKKIKR; (SEQ ID No: 18)
KPVKKKKIKREI; (SEQ ID No: 19) VKKKKIKREIKI; (SEQ ID No: 20)
KKKIKREIKILQ; (SEQ ID No: 21) KIKREIKILQNL; (SEQ ID No: 22)
[0066] and finally sequences from site 3 KILRLIDWGLAEFTHP (SEQ ID
No: 5) or the peptide with sequence KILRLIDWGLAE (SEQ ID No: 23),
the peptide with sequence LRLIDWGLAEFY (SEQ ID No: 24), or the
peptide with sequence LIDWGLAEFYHP (SEQ ID No: 25).
[0067] One example of a peptide of the invention comprising a
sequence homologous to T parva from site 3 of the CK2.alpha.
protein in P falciparum is the peptide RQKRLI (SEQ ID No: 141). The
invention also encompasses polymers of the peptide RQKRLI and in
particular the trimer (RQKRLI).sub.3 (SEQ ID No: 134), termed FD7
in the experimental section.
[0068] Preferably, the invention pertains to a peptide derived from
the CK2.alpha. protein of the parasite Theileria parva,
characterized in that its administration reduces parasitic
development.
[0069] A further embodiment of the peptides of the invention is
characterized in that the peptides are derived from the tau
protein. The tau sequence has a motif corresponding to the binding
site for the E4orf4 adenovirus protein. In the case of Alzheimer's
disease, the tau protein is regulated by protein phosphatase 2A.
Such peptides should thus be useful in treating Alzheimer's
disease.
[0070] The peptides identified by the method of the invention are
particularly useful in treating certain tumours and certain viral
or parasitic infections. The skilled person can select, using
binding competition tests, novel peptides derived from the
sequences identified using the method of the invention, said
peptides competitively inhibiting binding of the native protein
from which it derives with a holoenzyme PP2A or one of its
subunits.
[0071] Thus, the invention also concerns a natural or synthetic
peptide as defined above, characterized in that it competitively
inhibits interaction of the native protein from which it derives
with a PP2A holoenzyme or one of its subunits.
[0072] In order to be effective in vivo in treating certain tumours
or certain viral or parasitic infections, the peptides of the
invention can be coupled to a vector that is capable of
transferring said peptide into a eukaryotic cell. However, it is
possible, as will be discussed below, for the peptides of the
invention to themselves have the capacity to penetrate into cells,
meaning that the addition of a vector is not required.
[0073] Naturally, the invention pertains to means that can
synthesise the peptides of the invention. In particular, the
invention pertains to a polynucleotide characterized in that its
sequence consists of the sequence coding for a peptide of the
invention. Preferred polynucleotides are polynucleotides the
sequence of which is selected from one of the following sequences:
TABLE-US-00002 SEQ IDs No: 26
(5'GTGGAAGCCTTAATAAGAATTCTGCAACAACTGCTGTTTATTCATTT CAGAATT); No: 27
(5'CGACATAGCAGAATAGGCATTATTCAACAGAGGAGAACAAGAAATGG A); No: 28
(5'AGGAAGATCGGAAGAGGGAAGTTCAGTGAAGTTTTTGAGGGA); No: 29
(5'ACAGTAACGAAGGATAAATGCGTAATAAAAATCCTAAAGCCTGTAAA
GAAGAAGAAAATCAAGAGAGAGATTAAGATTCTACAGAACCTA); or No: 30
(5'AAAATACTAAGGCTAATTGACTGGGGATTAGCTGAGTTTTACCAC CCA)
, respectively coding peptides NOs: 1-5.
[0074] The invention also concerns polynucleotides with sequences
complementary to one of sequences SEQ ID No: 26-30 and sequences
hybridizing under stringent conditions to said polynucleotides.
[0075] The term "stringent conditions" means conditions that allow
specific hybridization of two single strand DNA sequences at about
65.degree. C., for example in a solution of 6.times.SSC; 0.5% SDS,
5.times. Denhardt's, solution and 100 .mu.g of non specific carrier
DNA or any other solution with an equivalent ionic strength and
after washing at 65.degree. C., for example in a solution of at
most 0.2.times.SSC and 0.1% SDS or any other solution with an
equivalent ionic strength. The parameters defining the stringency
conditions depend on the temperature at which 50% of the paired
strands separate (Tm). For sequences comprising more than 30 bases,
Tm is defined by the relationship: Tm=81.5+0.41 (% G+C)+16.6
log(concentration of cations)-0.63(% formamide)-(600/number of
bases). For sequences less than 30 bases long, Tm is defined by the
relationship: Tm=4 (G+C)+2(A+T). The stringency conditions have
also been defined using protocols described by Sambrook et al, 2001
(Molecular cloning: a laboratory manual, 3.sup.rd edition, Cold
Spring Harbor, Laboratory Press, Cold Spring Harbour, N.Y.).
[0076] It may be advantageous to synthesize a polypeptide
comprising a repeat of the peptide motifs identified by the process
of the invention. As a result, the invention pertains to a
polynucleotide characterized in that it consists of a multimer of a
polynucleotide coding for a peptide of the invention. The invention
also pertains to a polypeptide characterized in that it is
constituted by a repeat of a peptide of the invention.
[0077] The invention also pertains to a cell expression vector,
characterized in that it comprises a polynucleotide as defined
above and regulatory sequences allowing expression of a peptide of
the invention in a host cell.
[0078] The invention also pertains to a method for preparing a
peptide as defined in the invention, comprising transforming a host
cell using a cellular expression vector as defined above, followed
by culturing the transformed host cell, and recovering the peptide
in the culture medium.
[0079] The invention further pertains to an antiserum or
immunoserum or a purified polyclonal antibody or a monoclonal
antibody, characterized in that said antibody or said antiserum or
immunoserum is capable of specifically binding a peptide in
accordance with the invention.
[0080] Antibodies specifically directed against the peptides
identified by the process of the invention are obtained, for
example, by immunizing an animal after injecting a peptide of the
invention, and recovering the antibodies produced. A monoclonal
antibody can be obtained using techniques that are known to the
skilled person, such as the hybridoma method describd by Kohler and
Milstein (1975).
[0081] The antibodies obtained, specifically directed against
targets for protein phosphatase 2A, are of particular application
in immunotherapy. As an example, they can act as antagonists for
viral or parasitic proteins directed against protein phosphatase 2A
to block viral or parasitic development.
[0082] Similarly, polynucleotides encoding the peptides of the
invention can be directly transferred to the nucleus of target
cells, if necessary using suitable vectors, to allow in vivo
expression of the corresponding peptides, said peptides being
susceptible of blocking by competitive inhibition a specific
interaction between the protein phosphatase 2A and the viral or
parasitic protein from which they derive.
[0083] The invention thus pertains to a pharmaceutical composition
comprising one of the elements selected from a polynucleotide of
the invention or an antibody of the invention.
[0084] The invention also concerns a pharmaceutical composition
comprising one of the peptides of the invention in combination with
a pharmaceutically acceptable vehicle.
[0085] The invention further concerns the use of a peptide of the
invention as defined above in preparing a drug for use in treating
a viral or parasitic infection.
[0086] Preferably, the invention concerns the use of a peptide the
sequence of which derives from a fragment of the Vpr protein as
defined above, in preparing a drug that can inhibit an HIV
infection.
[0087] The peptides of the invention can advantageously be selected
so as to stimulate the induction of apoptosis linked to activation
of cellular protein phosphatase 2A. Thus, the invention also
concerns the use of a peptide of the invention as defined above in
preparing a drug that can induce apoptosis of target cells and in
particular tumour cells.
[0088] In a further preferred aspect, the invention concerns the
use of a peptide the sequence of which derives from a fragment of
the CK2.alpha. protein in preparing a drug that can inhibit
parasitic infection. More particularly, the invention concerns the
use of a peptide in preparing a drug for use in treating
malaria.
[0089] The viral or parasitic infection results in specific
expression of proteins comprising sequences of peptides of the
invention. The sequences encoding the peptides of the invention can
thus be used as a probe to detect, in a specific manner from RNA
extracted from a biological sample from a patient, a specific viral
infection or parasitic infection.
[0090] Similarly, an antibody of the invention can be used to
specifically recognize peptide sequences contained in viral or
parasitic proteins expressed during infection.
[0091] Thus, the invention concerns the use of a polynucleotide of
the invention or an antibody of the invention in the in vitro
diagnosis of parasitic or viral diseases.
[0092] The invention also pertains to the selection and use of a
peptide binding protein phosphatase 2A, and capable of penetrating
into cells.
[0093] An example of such a peptide is illustrated by the peptide
FD6 (SEQ ID No: 20) derived from the CK2.alpha. protein of T parva.
It has been shown in the present invention that the presence of
that peptide in the cell does not affect the viability of
cultivated or maintained mammal cells alive.
[0094] The experimental section below illustrates an application of
the method for identifying the peptides of the invention to
identifying peptides from the Vpr protein of HIV-1 and of the
CK2.alpha. protein from the Theileria parva parasite. The invention
also pertains to the selection and use of a peptide binding protein
phosphatase 2A and possibly capable of penetrating into a cell,
said peptide enabling targeting of and contact with intracellular
protein phosphatase 2A of a molecule capable of regulating the
activity of protein phosphatase 2A.
DESCRIPTION OF FIGURES
[0095] FIG. 1: Screening of a membrane containing peptides covering
the sequence for Vpr of HIV-1 with the structural subunit A of PP2A
(A) and the holoenzyme PP2A1 (B).
[0096] Covering the sequence of four peptides 54-57 defines the
sequence of site 2 TABLE-US-00003 VEALIRILQQLLFIHFRI (SEQ ID No: 1)
Peptide 54: VEALLRILQQLL Peptide 55: ALIRILQQLLFI Peptide 56:
IRILQQLLFIHF Peptide 57: ILQQLLFIHFRI
[0097] Covering the sequence of three peptides 64 to 66 defines the
sequence of site 1 TABLE-US-00004 RHSRIGIIQQRRTRNG (SEQ ID No: 2)
Peptide 64: RHSRIGIIQQRR Peptide 65: SRIGIIQQRRTR Peptide 66:
IGIIQQRRTRNG
[0098] FIG. 2: Screening of a membrane containing peptides covering
the sequence for CK2.alpha. of Theileria with (A) the structural
subunit A of PP2A and (B) the holoenzyme PP2A1.
[0099] Covering the sequence of two peptides defines the sequence
of site 1 TABLE-US-00005 RKIGRGKFSEVFEG (SEQ ID No: 3) Peptide 66:
RKIGRGKFSEVF Peptide 67: IGRGKFSEVFEG
[0100] Covering the sequence of ten peptides 74-83 defines the
sequence of site 2 TABLE-US-00006 TVTKDKCVIKILKPVKKKIKREIKILQNL.
(SEQ ID No: 4) Peptide 74: TVTKDKCVIKIL Peptide 75: TKDKCVIKILKP
Peptide 76: DKCVIKILKPVK Peptide 77: CVIKILKPVKKK Peptide 78:
IKILKPVKKKKI Peptide 79: ILKPVKKKKIKR Peptide 80: KPVKKKKIKREI
Peptide 81: VKKKKIKREIKI Peptide 82: KKKIKREIKILQ Peptide 83:
KIKREIKILQNL
[0101] Covering the sequence of three peptides defines the sequence
of site 3 TABLE-US-00007 KILRLIDWGLAEFTHP (SEQ ID No: 5) Peptide
129: KILRLIDWGLAE Peptide 130: LRLIDWGLAEFY Peptide 131:
LIDWGLAEFYHP
[0102] FIG. 3: FIG. 3 is a histogram representing the intracellular
penetration values obtained using a cell penetration test for the
peptides cited in Table 3.
[0103] FIG. 4: FIG. 4 illustrates the effects of different peptides
on the viability of Hela cells evaluated using a MTT viability
test.
[0104] The viability of Hela cells (expressed as a percentage with
respect to the initial population) was tested in the presence of
increasing concentrations of peptides FD8 (4A), FD13/FD14 (4B) and
FD11/FD12 (4C).
EXPERIMENTAL SECTION
A. MATERIALS AND METHODS
A.1. Purified PP2A Proteins
[0105] Trimeric PP2A1 protein was purified to homogeneity from pig
brain.
[0106] A recombinant structural subunit of PP2A was expressed in E
coli and purified using the protocol described by Cohen et al
(Cohen P, Alemany S, Hemmings B A, Resink T J, Stralfors P, Tung H
Y. Protein phosphatase-1 and protein phosphatase 2A from rabbit
skeletal muscle. Methods Enzymol 1988 159, 390-408), or that
described by Bosch et al (Bosch M, Cayla X, Van Hoof C, Hemmings B
A, Ozon R, Merlevede W, Goris J. the PR55 and PR65 subunits of
protein phosphatase 2A from Xenopus laevis. Molecular cloning and
developmental regulation of expression. Eur J Biochem 1995, 230,
1037-45).
A.2. Method for Identifying HIV Vpr Binding Sites and Theileria
parva (T parva) CK2.alpha. Binding Sites with PP2A
[0107] Binding peptides derived from CK2.alpha. proteins (encoded
by T parva protozoa) or Vpr protein (encoded by the HIV-1 virus)
with PP2A were identified using the "spot peptides" technique
described above (Frank and Overwing, 1996, Meth Mol Biol 66,
149-169).
[0108] The method consisted of synthesizing dodecapeptides, in situ
on a cellulose membrane, at defined positions wherein the series of
the sequence covered the whole sequence of the protein of interest
(Vpr or CK2.alpha.). The peptides of two consecutive spots on the
membrane overlap with an overlapped by two amino acids.
[0109] Sixty-eight (68) dodecapeptides covering the whole sequence
of the Vpr protein of HIV-1 and two hundred and five (205)
dodecapeptides covering the sequence for the CK2.alpha. protein of
Theileria were synthesized and covalently bound to cellulose
membranes.
[0110] Each prepared membrane was first saturated for 1 hour at
ambient temperature with TBS containing 5% skimmed Regilait (milk)
and 3% BSA then incubated overnight in the same buffer in the
presence of 4 .mu.g/ml of purified protein (subunit A of PP2A or
holoenzyme PP2A1). The specific interaction of each purified
protein (respectively the structural subunit A or the trimeric
holoenzyme PP2A1) with a peptide sequence was revealed, as in
Western blot, after incubating the membrane with an antibody
directed against the structural protein A (FIGS. 1A and 2A) and
with a mixture of antibodies recognizing the proteins A, B and C of
PP2A (FIGS. 1B and 2B).
[0111] The membranes were washed 5 times for 15 minutes with a
conventional TBST buffer (TBS+TWEEN) used for incubation then
incubated a further 1 hour at ambient temperature with a second
antibody (coupled with peroxidase). Finally, the membranes were
washed 5 times for 15 minutes with the TBST buffer and
revealed.
A.3. Cell Penetration Test
[0112] 1-Cells
[0113] We analyzed the Hela line, which is derived from a human
cervical carcinoma.
[0114] 2-Quantitative Determinations of Internalized Peptides
[0115] Lysis Buffer
[0116] 0.1 M Tris buffer, pH 8 containing 0.5% NP40.
[0117] OPD Buffer
[0118] 25.7 ml of 0.2 M dibasic sodium phosphate+24.3 ml of 0.1 M
citric acid+50 ml distilled water; adjust to pH 5.0.
[0119] Biotinylated-Avidine Peptide Complexes
[0120] 4 moles of peptides were incubated with 1 mole of
avidine-peroxidase. 20 minutes at ambient temperature.
[0121] Analysis of Intracellular Penetration of Various Peptides
into Hela Cell
[0122] Hela cells (10.sup.4 in 100 1) were seeded into 96-well
plates (flat bases) with complete DMEM medium in the presence of
2.5% penicillin/ampicillin and 10% foetal calf serum. After
incubating overnight at 37.degree. C., in a CO.sub.2 oven (5%),
different dilutions of complexes (biotinylated-avidine peroxidase
peptides) were added. After incubating for 4 hours the supernatant
was aspirated and the cells were washed 3 times with PBS,
trypsinated and taken up for counting in PBS. After counting, the
cells were taken up in 300 .mu.l of lysis buffer.
[0123] Measurement of Peroxidase Activity
[0124] 50 .mu.l of OPD buffer was incubated in a 96 well ELISA
plate with 50 .mu.l of lysis buffer or 50 .mu.l of cell lysate (in
general, different successive dilutions were carried out (to 1/2)).
In order to reveal, 50 .mu.l of OPD solution was added (in the
dark). The reaction (about 10 min) was stopped with 100 .mu.l of 1N
HCl.
[0125] Analysis of Results
[0126] The peroxidase activity was determined by reading at 490 nm
in the ELISA reader (reference filter at 620 nm) and the quantity
of peroxidase in the lysates was calculated from the calibration
curve then extrapolated to the same number of cells (10.sup.3 or
10.sup.4): Peptide molecules=(6*10.sup.23/MW of peptide)*ng of
PO*10.sup.-9. A.4. Cell Viability Test
[0127] Hela cells (10.sup.4 for 100 .mu.l) were seeded into 96-well
plates (flat bases) with complete DMEM medium containing 2.5%
penicillin/ampicillin and 10% foetal calf serum. After incubating
overnight at 37.degree. C. in a CO.sub.2 oven (5%), the cells were
cultivated in the presence of different peptide concentrations.
After incubating for 72 h, the medium containing the peptides was
aspirated and the MTT at 0.5 mg/ml (diluted in DMEM alone) was
added in an amount of 100 per well. Incubation was carried out in
the dark at 37.degree. C. for 30 minutes then the MTT was aspirated
off and 50 .mu.l of DMSO was added to all wells. It was necessary
to wait ten minutes for complete lysis of the cells and to agitate
the lysate wells to homogenize dissolution of the reaction product
in the wells. The plates were then read at 570 nm with a 690 nm
reference filter.
B. RESULTS AND DISCUSSION
B.1. Identification of Peptide sequences Containing Binding Sites
for Proteins Coded by Two Pathogenic Agents (HIV-1 and T parva)
with PP2A (PP2A1 and Subunit A)
[0128] The results obtained after incubating membranes containing
peptides covering the sequences for Vpr of HIV-1 and CK2.alpha. of
T parva with purified trimeric PP2A holoenzyme allowed five
sequences of Vpr and CK2.alpha. peptides to be determined that were
capable of specifically binding PP2A and are shown in the table
below: TABLE-US-00008 TABLE 1 Peptide sequences containing binding
sites for HIV-1 Vpr and CK2.alpha. with PP2As subunit A PP2A1 HIV-1
Vpr site 1 RHSRIGIIQQRRTRNG RHSRIGIIQQRRTRNG site 2
VEALIRILQQLLFIHFRI T parva site 1 RKIGRGKFSEVFEG CK2.alpha. site 2
TVTKDKCVIKILKPVKKK KIKREIKILQNL site 3 KILRLIDWGLAEFYHP
KILRLIDWGLAEFYHP
[0129] More precisely, two peptide sequences containing a binding
site for the Vpr of HIV-1 with the protein PP2A1 (FIG. 1B; "site
1") and with the subunit A (FIG. 1A, "site 1" and "site 2") were
identified. Three peptide sequences containing a binding site for
CK2.alpha. of T parva with the protein PP2A1 (FIG. 2B, "site 3")
and with the structural subunit A were also identified (FIG. 2A,
"site 1", "site 2" and "site 3").
B.2. Importance of Using HIV-1 VPr Peptides Which Bind PP2A
[0130] The exogenic expression or expression due to proviral
infection of the Vpr of HIV-1 induces apoptosis in Hela cells, T
lymphoid lines and primary lymphocytes (Stewart et al, 1997 J Virol
71: 5579-9). The use of Vpr mutants initially allowed this effect
to be correlated with stopping cells in phase G2 of the cell cycle.
More recently, it has been shown that Vpr can also induce apoptosis
independently of stopping at G2 (Nishizawa et al, 2000, Virology
27, 16-26).
[0131] It has been reported that activation of PP2A after
interaction with the E4orf4 adenoviral protein induces apoptosis in
transformed cells (Shtrichman R et al, 2000, Oncogene 19,
3757-3765). Analogously, expression of Vpr also induces apoptosis
in transformed cells (Stewart et al, 1999, PNAS, 96,
12039-12043).
[0132] Further, an analysis of Vpr mutants known in the art
indicates that the peptides identified by the process of the
invention and specifically binding the PP2A protein contain
sequences which correlate with those required for the pro-apoptotic
effect of Vpr.
[0133] Thus, fragments of viral proteins, Vpr and E4orf4, which
interact with PP2A and are identified by the process of the
invention, could be useful in inducing apoptosis of tumor
cells.
[0134] The identified peptides are also naturally used in
inhibiting infection by HIV or other related viruses and
retroviruses.
B.3. Importance of Using T parva CK2.alpha. Sequences That Bind
PP2A
[0135] The use of okadaic acid and the small t antigen of SV40 has
demonstrated that PP2A controls cell proliferation via a novel
cascade of phosphorylations involving PI3-kinase, PKC.zeta.
(identified as a MAP-kinase-kinase-kinase or MEKK), the MEK protein
and the two MAP kinases ERK-1 and ERk-2, and transcription factors
NF-.kappa.B and Sp1 (Sontag E, Sontag J M, Garcia A (1997), EMBO J,
16, 5662-5671; Ayllon V, Martinez A, C, Garcia A, Cayla X and
Rebollo A (2000), EMBO J 19, 1-10, A Garcia, S Cereghini, E Sontag
(2000), J Biol Chem 275, 9385-9389). Further, the role of PP2A in
regulating the cascade of MAP kinases has also been suggested by
studies by Chambaz's team (Heriche et al, (1997), Science, 276,
952-955) which have shown that overexpression of the cellular
CK2.alpha. subunit activates PP2A which dephosphorylates the MEK
protein.
[0136] Studies by Ole-Moi et al (Embo J, 1993, 12, 1621-1631) have
shown that transformation by Theileria induces hyperphosphorylation
of host proteins. This effect is partially due to constitutive
activation of cellular CK2 which should itself depend on the action
of a CK2.alpha. type subunit coded by the parasite and secreted
into the cytosol of the transformed cell.
[0137] As indicated below, a comparison of the sequences identified
by the process of the invention corresponding to the three binding
sites with PP2A allows the presence of a motif of the type:
K-I-G/L-R/K, which is partially repeated in site 2, to be
identified. TABLE-US-00009 ##STR1##
[0138] It is interesting to note that the binding site for the ATP
of CK2.alpha. partially covers site 1 and site 2, which suggests
inhibition of kinase activity after interaction of CK2.alpha. with
the subunit A. Further, as will be seen from Table 2 below, the
three sequences containing the binding sites for CK2.alpha. of T
parva with PP2A are conserved among a number of species including
P. Falciparum and Leishmania parasites. TABLE-US-00010 TABLE 2
Comparison of various sequences of CK2.alpha. with peptides from T.
parva containing binding sites with PP2A (the sequences of P.
falciparum are deduced from an EST; the others are from the
"Swissprot" gene bank). Only residues that differ from the T. parva
sequence are indicated. ##STR2## ##STR3## ##STR4##
[0139] A careful analysis of the interactions suggests that the
CK2.alpha. from these different species should interact with PP2A;
as an example peptide 131 from T parva CK2.alpha. described in FIG.
2 and in which the first four amino acids of site 3 are deleted is
capable of binding PP2A. This suggests that the CK2.alpha. of
Leishmania, P falciparum, which differ in their 3 first amino
acids, should bind PP2A. This is consistent with the fact that the
KILRLI motif has a duplicaton of K/R-II/L-I/L which, in a basic
context, could be a binding site for PP2A.
[0140] The presence inside the cell of these peptides,
corresponding to the in vivo binding sites of proteins with PP2A,
could thus interfere with the development of those parasites.
B. 4. Biological Effects of Peptide Compounds of the Invention on
Cells
[0141] The various peptides listed in Table 3 were synthesized in
the biotinylated form, purified by HPLC (Neosystem) and their
effect on intracellular penetration and cell viability was analyzed
in Hela cells. A study of the series of peptides shown in Table 1
has allowed six peptides to be determined which have the
possibility of penetrating into the Hela cell (FIG. 3). [0142] FD6:
a 12AA peptide derived from a site for interaction of the A subunit
of PP2A with the T parva CK2.alpha. protein; [0143] FD7: a 18AA
peptide corresponding to three repeats of a 6AA hexa motif; this
sequence, derived from P falciparum CK2.alpha., is homologous with
the T parva sequence that binds PP2A; [0144] FD8: a peptide derived
from protamine (a known PP2A activator); [0145] FD11: a 18AA
peptide corresponding to three repeats of a 6AA hexa motif derived
from the sequence for FD14; [0146] FD14: FD14, which reproduces the
binding site which we have characterized from HIV-1 Vpr with PP2A;
[0147] FD13: This peptide corresponds to a HIV-1 Vpr sequence which
is homologous with the FD14 peptide sequence, which represents a
binding site with PP2A with another HIV-1 Vpr.
[0148] Further, viability studies carried out on the series of
peptides shown in Table 1 allowed three peptides to be identified
which inhibit the viability of Hela cells: [0149] FD8: affects the
viability of Hela cells (FIG. 4A); [0150] FD14: clearly affects the
viability of Hela cells (FIG. 4B);
[0151] FD12: a 18AA peptide the sequence of which derives from that
of the FD11 peptide (R is mutated into A). This peptide, which is
homologous with the glucosamine transferase protein of Chlamydia
muridarum, affects the viability of the Hela cell (FIG. 4C). This
biological effect could be due to an interaction with the plasma
membrane. TABLE-US-00011 TABLE 3 Peptides mimicking binding sites
for target proteins with PP2As Original peptide peptide proteins
codes sequences SEQ ID No: CD28 FD2 -PRRPGPTRKHY SEQ ID No: 132 FD3
-(PRRPGPTRK)2 SEQ ID No: 133 CK2.alpha. FD6 -VKKKKIKREIKI SEQ ID
No: 20 T parva CK2a P. FD7 -(RQKRLI)3 SEQ ID No: 134 Falciparum (T
parva analogue) Vpr (HIV-1) FD9 -RHSRIG SEQ ID No 135 FD10
-(RHSRIG)2 SEQ ID No: 136 FD11 -(RHSRIG)3 SEQ ID No: 137 FD12*
-(AHSRLG)3 SEQ ID No: 138 (FD11 mutation, R...A) FD13
RHSRIGVTRQRRARNG SEQ ID No: 139 (ED 14 analogue) FD14
RHSRIGIIQQRRTRNG SEQ ID No: 2 Protamine FD8 RRRRRRRRSRGRR SEQ ID
No: 140 RRTY
DISCUSSION
[0152] Are peptides from certain proteins which interact with PP2As
a novel anti-tumoral approach?
[0153] Our study has allowed to identify two penetrating peptides
(FD8/FD14) derived from two proteins, Vpr and protamine, known to
interact with PP2As. These peptides, which have in common sequences
rich in arginine and lysine, could thus penetrate into the cell
using a general internalization mechanism. Such a mechanism, which
is common in internalizing peptides having arginine-rich sequences,
has recently been proposed (Tomoki Suzuki et al, 2002, Possible
existence of common interlization mechanisms among arginine-rich
peptides, JBC 277, 2437-2443). In general, the presence of
sequences that are rich in arginine or lysine characterize proteins
binding PP2As, which suggests that other penetrating peptides could
be identified in the PP2A family.
[0154] Vpr, a protein coded by the HIV-1 virus, is involved in
maintaining a high viral charge and in establishing pathogenesis
linked to HIV. The expression of Vpr, exogenic or due to proviral
HIV-1 infection, induces apoptosis in Hela cells, in T lymphoid
lines, in primary lymphocytes and in transformed cells (Stewart et
al, J Virol 1997, 71, 5579-9; Stewart et al 1999, PNAS, 96,
12039-12043). Further, it has been reported that the interaction of
PP2A with a further viral protein, adenovirus E4orf4 (Marcellus et
al, J Virol 2000, 74, 7869-7877) can induce apoptosis in tumor
cells. In total, these results suggest the hypothesis that
activation of certain PP2As would be a novel means of inducing
tumor apoptosis. In this regard, our results shown in FIG. 4B
suggest that the F14 peptide derived from HIV-1 Vpr could represent
an anti-tumoral biopeptide. The absence of the biological effect of
peptide FD13 (the sequence for which differs by four AA compared
with FD14--see Table 2) suggests that the structure of FD14 is
critical in regulating Hela viability. As a result, the production
of chemical molecules mimicking the structure of the FD14 peptide
could thus allow novel anti-tumoral substances to be generated.
Sequence CWU 1
1
44 1 18 PRT virus HIV 1 Val Glu Ala Leu Ile Arg Ile Leu Gln Gln Leu
Leu Phe Ile His Phe 1 5 10 15 Arg Ile 2 16 PRT virus HIV 2 Arg His
Ser Arg Ile Gly Ile Ile Gln Gln Arg Arg Thr Arg Asn Gly 1 5 10 15 3
14 PRT Theileria parva 3 Arg Lys Ile Gly Arg Gly Lys Phe Ser Glu
Val Phe Glu Gly 1 5 10 4 29 PRT Theileria parva 4 Thr Val Thr Lys
Asp Cys Val Ile Lys Ile Leu Lys Pro Val Lys Lys 1 5 10 15 Lys Lys
Ile Lys Arg Glu Ile Lys Ile Leu Gln Asn Leu 20 25 5 16 PRT
Theileria parva 5 Lys Ile Leu Arg Leu Ile Asp Trp Gly Leu Ala Glu
Phe Tyr His Pro 1 5 10 15 6 12 PRT virus HIV 6 Val Glu Ala Leu Ile
Arg Ile Leu Gln Gln Leu Leu 1 5 10 7 12 PRT virus HIV 7 Ala Leu Ile
Arg Ile Leu Gln Gln Leu Leu Phe Ile 1 5 10 8 12 PRT virus HIV 8 Ile
Arg Ile Leu Gln Gln Leu Leu Phe Ile His Phe 1 5 10 9 12 PRT virus
HIV 9 Ile Leu Gln Gln Leu Leu Phe Ile His Phe Arg Ile 1 5 10 10 12
PRT virus HIV 10 Arg His Ser Arg Ile Gly Ile Ile Gln Gln Arg Arg 1
5 10 11 12 PRT virus HIV 11 Ser Arg Ile Gly Ile Ile Gln Gln Arg Arg
Thr Arg 1 5 10 12 12 PRT virus HIV 12 Ile Gly Ile Ile Gln Gln Arg
Arg Thr Arg Asn Gly 1 5 10 13 12 PRT Theileria parva 13 Thr Val Thr
Lys Asp Lys Cys Val Ile Lys Ile Leu 1 5 10 14 12 PRT Theileria
parva 14 Thr Lys Asp Lys Cys Val Ile Lys Ile Leu Lys Pro 1 5 10 15
12 PRT Theileria parva 15 Asp Lys Cys Val Ile Lys Ile Leu Lys Pro
Val Lys 1 5 10 16 12 PRT Theileria parva 16 Cys Val Ile Lys Ile Leu
Lys Pro Val Lys Lys Lys 1 5 10 17 12 PRT Theileria parva 17 Ile Lys
Ile Leu Lys Pro Val Lys Lys Lys Lys Ile 1 5 10 18 12 PRT Theileria
parva 18 Ile Leu Lys Pro Val Lys Lys Lys Lys Ile Lys Arg 1 5 10 19
12 PRT Theileria parva 19 Lys Pro Val Lys Lys Lys Lys Ile Lys Arg
Glu Ile 1 5 10 20 12 PRT Theileria parva 20 Val Lys Lys Lys Lys Ile
Lys Arg Glu Ile Lys Ile 1 5 10 21 12 PRT Theileria parva 21 Lys Lys
Lys Ile Lys Arg Glu Ile Lys Ile Leu Gln 1 5 10 22 12 PRT Theileria
parva 22 Lys Ile Lys Arg Glu Ile Lys Ile Leu Gln Asn Leu 1 5 10 23
12 PRT Theileria parva 23 Lys Ile Leu Arg Leu Ile Asp Trp Gly Leu
Ala Glu 1 5 10 24 12 PRT Theileria parva 24 Leu Arg Leu Ile Asp Trp
Gly Leu Ala Glu Phe Tyr 1 5 10 25 12 PRT Theileria parva 25 Leu Ile
Asp Trp Gly Leu Ala Glu Phe Tyr His Pro 1 5 10 26 54 DNA virus HIV
26 gtggaagcct taataagaat tctgcaacaa ctgctgttta ttcatttcag aatt 54
27 48 DNA virus HIV 27 cgacatagca gaataggcat tattcaacag aggagaacaa
gaaatgga 48 28 42 DNA Theileria parva 28 aggaagatcg gaagagggaa
gttcagtgaa gtttttgagg ga 42 29 90 DNA Theileria parva 29 acagtaacga
aggataaatg cgtaataaaa atcctaaagc ctgtaaagaa gaagaaaatc 60
aagagagaga ttaagattct acagaaccta 90 30 48 DNA Theileria parva 30
aaaatactaa ggctaattga ctggggatta gctgagtttt accaccca 48 31 12 PRT
Theileria parva 31 Arg Lys Ile Gly Arg Gly Lys Phe Ser Glu Val Phe
1 5 10 32 12 PRT Theileria parva 32 Ile Gly Arg Gly Lys Phe Ser Glu
Val Phe Glu Gly 1 5 10 33 11 PRT Theileria parva 33 Pro Arg Arg Pro
Gly Pro Thr Arg Lys His Tyr 1 5 10 34 18 PRT Theileria parva 34 Pro
Arg Arg Pro Gly Pro Thr Arg Lys Pro Arg Arg Pro Gly Pro Thr 1 5 10
15 Arg Lys 35 18 PRT Theileria parva 35 Arg Gln Lys Arg Leu Ile Arg
Gln Lys Arg Leu Ile Arg Gln Lys Arg 1 5 10 15 Leu Ile 36 6 PRT
Theileria parva 36 Arg His Ser Arg Ile Gly 1 5 37 12 PRT Theileria
parva 37 Arg His Ser Arg Ile Gly Arg His Ser Arg Ile Gly 1 5 10 38
18 PRT Theileria parva 38 Arg His Ser Arg Ile Gly Arg His Ser Arg
Ile Gly Arg His Ser Arg 1 5 10 15 Ile Gly 39 18 PRT Theileria parva
39 Ala His Ser Arg Ile Gly Ala His Ser Arg Ile Gly Ala His Ser Arg
1 5 10 15 Ile Gly 40 16 PRT Theileria parva 40 Arg His Ser Arg Ile
Gly Val Thr Arg Gln Arg Arg Ala Arg Asn Gly 1 5 10 15 41 16 PRT
Theileria parva 41 Arg Arg Arg Arg Arg Arg Arg Ser Arg Gly Arg Arg
Arg Arg Thr Tyr 1 5 10 15 42 6 PRT Theileria parva 42 Arg Gln Lys
Arg Leu Ile 1 5 43 30 PRT Theileria parva 43 Thr Val Thr Lys Asp
Lys Cys Val Ile Lys Ile Leu Lys Pro Val Lys 1 5 10 15 Lys Lys Lys
Ile Lys Arg Glu Ile Lys Ile Leu Gln Asn Leu 20 25 30 44 29 PRT
Theileria parva 44 Leu Phe Ile His Phe Arg Ile Gly Cys Gln His Ser
Arg Ile Gly Ile 1 5 10 15 Thr Arg Arg Arg Arg Val Arg Asp Gly Ser
Ser Arg Pro 20 25
* * * * *