From the Department of Medical Biochemistry,
Institute of Basic Medical Sciences, and the § Department of
Pharmacology, School of Pharmacy, University of Oslo, Box 1112, Blindern, N-0317 Oslo, Norway and the ¶ Institute of Molecular
Genetics AS CR, Vídenská 1083, 142 20 Prague 4, Czech
Republic
Received for publication, February 17, 2003, and in revised form, March 25, 2003
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ABSTRACT |
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Raft-associated Csk controls signaling through
the T cell receptor (TCR) and was mainly anchored to Cbp/PAG
(phosphoprotein associated with glycosphingolipid-enriched membrane
domains). Treatment of cells with the cAMP-elevating agent
prostaglandin E2 (PGE2) augmented the
level of Cbp/PAG phosphorylation with a concomitant increase in amounts
of Csk bound to Cbp/PAG. While TCR-triggering resulted in transient
dissociation of Csk from Cbp/PAG/rafts allowing TCR-induced tyrosine
phosphorylation to occur, pretreatment with PGE2 reduced
Csk dissociation upon TCR triggering. This correlated with lowered
TCR-induced phosphorylation of CD3 Upon triggering of the T cell receptor (TCR)1
activation of Lck leads to
phosphorylation of the immunoreceptor tyrosine-based activation motifs
of the CD3 complex (1). The physiologically relevant pool of Lck most
probably partitions into lipid rafts (2). In resting T cells this pool
of Lck is kept in an inactive state due to phosphorylation of
Tyr505 by Csk, which is recruited to rafts via
binding of its SH2 domain to phosphorylated Tyr317 in the
transmembrane adaptor molecule Cbp/PAG (2-4). Upon TCR triggering, Csk
transiently dissociates from rafts, allowing Lck to become activated
(4, 5). Thus, tonic repression of Lck activity in rafts by Csk seems to
set the threshold for TCR signaling and appears necessary to avoid
unregulated TCR signaling and activation. This model is supported by
several observations: (i) modest overexpression (2.5-3.2-fold) or
membrane targeting of Csk inhibit TCR-induced tyrosine phosphorylation
and IL-2 production (6), (ii) studies on inducible csk
knock-outs revealed up-regulated Lck/Fyn activities (7), (iii)
displacement of endogenous Csk from lipid rafts has stimulatory effects
on Cyclic AMP (cAMP) inhibits TCR-induced T cell activation and thereby
exerts important immunoregulatory functions (8). Based on studies with
selective agonists, activation of protein kinase A (PKA) type I is
necessary and sufficient for mediating these effects of cAMP (9). We
recently found that PKA through phosphorylation of Ser364
in Csk induces a 2-4-fold activation of Csk in T cell lipid rafts (10), making Csk the most upstream PKA target reported so far (reviewed
in Ref. 11). However, the question of how PKA can regulate Csk if the
latter dissociates from rafts upon TCR triggering remained to be
addressed. Here, we report that prostaglandin E2 (PGE2) and cAMP induce increased targeting of Csk to rafts,
where Csk is further activated by PKA-mediated phosphorylation. This dual effect on Csk localization and activity by cAMP inhibits signaling
through the TCR.
T Cell Purification and Transfection--
Human peripheral blood
T cells were purified by negative selection as described previously
(12), transfected in accordance with the manufacturer's instructions
by using the Amaxa nucleofector and kit (catalog number VPA-1002);
transfection efficiencies of more than 80% were achieved. Jurkat TAg
cells were transfected as described previously (5).
Reagents and Antibodies--
PGE2 and protein kinase
A inhibitor peptide (catalog number P-6062) were purchased from Sigma,
n-octyl- Constructs--
The different Csk constructs have been described
elsewhere (5). An N-terminally HA-tagged chimeric LAT36-protein kinase A inhibitor (PKI) construct in pEF-HA-Bos vector consisted of the 36 N-terminal amino acids of human LAT (this includes the extracellular and transmembrane domains and the membrane proximal part
of the intracellular portion including cysteine residues important for
lipid raft localization) fused to PKI. Another LAT-PKI chimer consisted
of the N-terminal 39 amino acids of rat LAT fused to PKI (called
LAT39-PKI), where the tyrosine residue in the cytoplasmic region of LAT
had been mutated to phenylalanine by site-directed mutagenesis
(QuikChange, Stratagene, La Jolla, CA).
Stimulation of Cells, Purification of Lipid Rafts,
Immunoprecipitations, and Kinase Assays--
T cells were stimulated
or not with PGE2 (100 µM for 1.5 min if not
stated otherwise); thereafter, anti-CD3 IL-2 Promoter Activity and T Cell Proliferation Assay--
These
assays were conducted as described previously (5, 12).
Csk Interaction with Cbp/PAG Increases following cAMP
Treatment--
PGE2 (2 µM) elicited a rapid
and robust cAMP response in T cells (Fig.
1A), whereas maximal cAMP
responses were observed at 15-50-fold higher concentrations of
PGE2 (30-100 µM) (data not shown).
Interestingly, the total amount of Csk present in lipid rafts of
resting T cells increased upon PGE2 stimulation
(densitometric scanning analysis: 2.7-fold increase ± 0.5, average ± S.E., n = 3), whereas neither the level
of raft-associated Cbp/PAG nor the total amount of Csk present in whole
cell lysates were changed (Fig. 1B). In T cells Cbp/PAG is
exclusively present in lipid rafts (data not shown), and
immunodepletion of Cbp/PAG from isolated rafts removed the majority of
raft-associated Csk (Fig. 1C), indicating that Cbp/PAG is
the main protein recruiting Csk to rafts in T cells. PGE2
stimulation of resting T cells resulted in an increase in Cbp/PAG
tyrosine phosphorylation status, and more importantly, a concomitant
increase (densitometric scanning analysis: 2.2-fold ± 0.3, average ± S.E., n = 7) in the amounts of Csk that
co-immunoprecipitated with Cbp/PAG (Figs. 1D and
2B). Similar findings were also obtained with forskolin (not
shown). Altogether, this points toward a role for cAMP in modulating
the total amount of Csk in lipid rafts of resting T cells.
Inhibition of TCR-induced Signaling by cAMP Is Dependent on
Raft-associated Csk--
We next tested whether elevated amounts of
Csk in rafts induced by cAMP could repress signaling through the TCR.
Incubation of T cells with PGE2 prior to TCR triggering
inhibited TCR-induced tyrosine phosphorylation of Engagement of Csk SH2 Domain and PKA-mediated Phosphorylation of
Csk-S364 Both Activate Csk but via Separate Mechanisms--
Previous
findings have demonstrated that engagement of the Csk SH2 domain by
binding to phosphorylated Cbp/PAG leads to a 2-4-fold increase in Csk
kinase activity (13). A similar induction of Csk activity is caused by
PKA-mediated phosphorylation of Csk in rafts (10). Since cAMP elevates
the total amount of raft-associated Csk via increased interaction
between Csk and Cbp/PAG, we next tested the impact of the concerted
action of Cbp/PAG-binding and PKA-mediated phosphorylation on Csk
kinase activity. As reported earlier (13), co-incubation of purified
Csk with a 10-mer peptide corresponding to phosphorylated
Tyr317 in Cbp/PAG (called Tyr(P)317
peptide) resulted in an ~3-fold induction of Csk kinase activity compared with the effect of a corresponding de-phospho peptide (called
Tyr317 peptide) (Fig.
3A). As expected,
co-incubation of the Tyr317 peptide with Csk and PKA
catalytic subunit (C The Inhibitory Effect of cAMP on TCR-induced NFAT-AP-1 Activation
Is Dependent on Raft-associated Csk--
Multiple molecular
targets for cAMP/PKA have been defined in the signaling cascades
downstream of the TCR (reviewed in Ref. 11). To test the physiological
relevance of raft-associated Csk as a PKA target, we studied downstream
signaling events in T cells. As expected, PGE2 inhibited
TCR-induced T cell proliferation in a
concentration-dependent manner, while the additional
presence of the cAMP-antagonist Rp-8-bromo-cAMP right-shifted the curve (Fig. 4A), implicating that
the observed effects of PGE2 are mediated by cAMP. We next
performed transfection studies with plasmids encoding either
kinase-deficient Csk-SH3-SH2 (or Csk-SH3-SH2-W47A, which also has a
defect SH3 domain) or LAT-PKI chimeras consisting of the N-terminal
part of LAT (including the lipid raft targeting domain) fused to PKI.
The Csk mutants have the ability to displace endogenous Csk from lipid
rafts, while the LAT-PKI chimeras showed membrane localization in
immunofluoresence studies (not shown), distributed mainly to the
particulate fraction (Fig. 4B, upper panel) and
also partitioned into lipid raft fractions (Fig. 4B, lower panel). Thus, the LAT-PKI chimeras potentially could
inhibit membrane-bound PKA activity. PGE2 pretreatment
inhibited TCR-induced NFAT-AP-1 activation in Jurkat TAg cells ~40%
(Fig. 4C), while expression of kinase-deficient Csk-SH3-SH2
or the different LAT-PKI chimeras abolished these inhibitory effects of
PGE2 (Fig. 4C). Forskolin induced a stronger and
more sustained cAMP response compared with PGE2 (not shown)
and yielded up to 65% inhibition of TCR-induced NFAT-AP-1 activation
when control transfected cells were pretreated with forskolin (Fig.
4D). In contrast, cells transfected with either
kinase-deficient Csk or LAT-PKI were almost insensitive to the
inhibitory effects of forskolin (20 and 17% inhibition, respectively,
Fig. 4D). Altogether, this indicates that both
raft-associated Csk and membrane-bound PKA are essential for the
inhibitory effects of PGE2/cAMP on TCR-induced downstream
signaling events such as NFAT-AP-1 activation.
The effects of cAMP/PKA on raft-associated Csk described in this paper,
including both spatial and enzymatic regulation of Csk, result in
repression of signaling through the TCR, and hence T cell activation.
However, how cAMP induces increased phosphotyrosine levels in Cbp/PAG,
and thereby facilitates Csk binding, is still an enigma and suggests
the involvement of additional targets regulated by cAMP. This can
encompass both protein-tyrosine kinases and protein-tyrosine
phosphatases. Src family kinases are reported to phosphorylate Cbp/PAG
(3, 4), but at least in T cells the activity of Lck is lowered upon
cAMP-stimulation, most probably due to activation of Csk (10).
Nevertheless, a recent report points toward an essential role for Fyn
in the phosphorylation of Cbp/PAG in T cells (14). In vitro
studies have revealed that Csk also can phosphorylate Cbp/PAG, but only
when Cbp/PAG has a certain phosphotyrosine content beforehand (13). The
protein-tyrosine phosphatases responsible for regulation of Cbp/PAG
phosphorylation status are currently being unraveled, and a recent
report implicated CD45 in dephosphorylation of Cbp/PAG upon TCR
triggering (15). However, further studies appear necessary to identify
the targets whereby cAMP regulates tyrosine phosphorylation of
Cbp/PAG.
In conclusion, we report that the cAMP/PKA signal pathway through dual
mechanisms of increased anchoring and direct
phosphorylation-dependent activation regulates Csk, thereby
inhibiting signaling through the TCR. This involves cAMP-driven
recruitment of Csk to rafts where PKA-mediated phosphorylation of Csk
results in elevated levels of raft-associated Csk phosphotransferase activity.
-chain and linker for
activation of T cells. Moreover, competition of endogenous Csk from
lipid rafts abolished PGE2-mediated inhibition of
TCR-induced
-chain phosphorylation and activation of the
nuclear factor of activated T cells (NFAT) activator protein 1 (AP-1).
Finally, raft-associated Csk already activated via Cbp/PAG binding,
gained additional increase in phosphotransferase activity upon protein
kinase A-mediated phosphorylation of Csk. We propose that cAMP
regulates Csk via both spatial and enzymatic mechanisms, thereby
inhibiting signaling through the TCR.
INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
-chain phosphorylation and IL-2 promoter activation both in
resting T cells and after TCR triggering (5). Thus, control of Csk
activity in rafts seems to be of major importance to prevent aberrant
TCR signaling.
EXPERIMENTAL PROCEDURES
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
-D-glucoside from United States
Biochemical, and forskolin from Calbiochem. Phospho- and
dephospho-Tyr317-PAG peptides (from Eurogentec) are 10-mer
peptides corresponding to the sequence surrounding Tyr317
in Cbp/PAG and have been described earlier (13). All antibodies were
as described previously (5, 10). A standard cAMP assay (kit from
PerkinElmer Life Sciences, catalog number SP004) was performed
in accordance with the manufacturer's instructions. The program Scion
Image from Scion Corp. was used for densitometric scanning analysis.
monoclonal antibody OKT-3 (5 µg/ml) was added and 2 min later CD3 was cross-ligated by
addition of F(ab')2 fragments (20 µg/ml), and incubations
were continued. Cells were disrupted in lysis buffer (50 mM
HEPES, pH 7.4, 100 mM NaCl, 5 mM EDTA, 1.0%
Triton X-100 with 2 mM sodium orthovanadate, 1 mm
phenylmethylsulfonyl fluoride, 10 mm sodium pyrophosphate, and
50 mm sodium fluoride) containing
n-octyl-
-D-glucoside (50 mM) and
subjected to immunoprecipitation, as described previously (10). Lipid
raft fractions were isolated as before from cell lysates (with 1%
Triton X-100) by sucrose-gradient centrifugation (5). In the presence
of ATP (1 mM) and MgCl2 (15 mM)
lipid raft fractions were stimulated with or without forskolin (100 µM, 10 min) or PGE2 (100 µM, 2 min) at 30 °C; thereafter, reactions were stopped by addition of
lysis buffer containing n-octyl-
-D-glucoside, and subsequently Csk immunoprecipitation and Csk kinase assay with
poly(Glu,Tyr) as substrate were performed as described previously (10).
Equal amounts of immunoprecipitated Csk or co-immunoprecipitated Cbp/PAG present in each kinase reaction were verified by
immunoblotting. Cloning, expression, and purification of human Csk,
Csk-S364C, and PKA C
have been reported previously (10).
RESULTS AND DISCUSSION
TOP
ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS AND DISCUSSION
REFERENCES
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Fig. 1.
Cyclic AMP increases interaction between Csk
and Cbp/PAG. A, T cells were incubated with
PGE2 (2 µM) for the indicated times and
levels of cAMP were measured. B, normal T cells were
incubated with or without PGE2 (100 µM) for
1.5 min. After lysis of cells and sucrose-gradient fractionation, the
lipid raft containing fractions were mixed and immunoblotted with the
indicated antibodies (middle and lower panels).
The numbers below the middle panel (Csk blot) are
results from densitometric scanning analysis. Bars represent
results from several experiments (average ± S.E.). Whole cell
lysates were also assessed with respect to Csk content (upper
panel). C, purified lipid raft samples from normal T
cells were subjected to three consecutive rounds of immunoprecipitation
with either anti-Cbp/PAG antibody or non-immune mouse serum
(NMS), and samples were then immunoblotted for Cbp/PAG and
Csk. The immunoprecipitates were immunoblotted for Cbp/PAG and
co-precipitated Csk. D, primary T cells were stimulated with
or without PGE2 as in B. After disruption of
cells in lysis buffer (with
n-octyl- -D-glucoside), Cbp/PAG
immunoprecipitates were analyzed with the indicated antibodies
as described in the legend for B.
-chain (Fig.
2, A and B), LAT
(Fig. 2B), and Slp-76 (not shown). While TCR triggering
resulted in transient dephosphorylation of Cbp/PAG and dissociation of
Csk from Cbp/PAG (and thereby rafts), preincubation of PGE2
prior to TCR stimulation increased the amount of Csk
co-immunoprecipitating with Cbp/PAG both in the resting state and the
first minutes after TCR-triggering (Fig. 2C). We next
transfected primary T cells with either empty vector or a plasmid
encoding kinase-deficient Csk-SH3-SH2, which has intact and functional
SH3 and SH2 domains but lacks the kinase domain. Overexpression of this
latter construct has previously been shown to displace endogenous Csk
from lipid rafts (5). While T cells transfected with empty vector
revealed normal TCR-induced
-chain phosphorylation (and tyrosine
phosphorylation of LAT and Slp-76, not shown) that was inhibited by
PGE2 preincubation, transfection of kinase-deficient
Csk-SH3-SH2 abolished the inhibitory effects of PGE2 (Fig.
2D). Similar findings were obtained with Jurkat TAg cells
(not shown). Altogether, this indicates that the inhibitory effects of
PGE2/cAMP on TCR signaling are dependent on the presence of
Csk in rafts and/or the ability of recruiting additional amounts of Csk
to rafts.
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Fig. 2.
PGE2-mediated regulation of
raft-associated Csk represses TCR-induced tyrosine
phosphorylation. A, normal T cells were incubated with
or without PGE2 for 1.5 min, then OKT-3 was added and
samples at time 0 withdrawn and disrupted in lysis buffer containing
n-octyl- -D-glucoside. 2 min later
F(ab')2 fragments were added to allow TCR cross-linking,
and samples withdrawn at the indicated periods of time (called
anti-CD3). Lysates were immunoblotted with the indicated antibodies.
B, data from four experiments as in A were analyzed with
respect to total phosphotyrosine content in CD3
(p21 and p23) and
LAT and normalized for the amount of p16 (CD3
). The inhibition in
TCR-induced tyrosine phosphorylation caused by PGE2
pretreatment is given. C, same as described in the legend
for A, but after disruption of cells, Cbp/PAG
immunoprecipitates were analyzed with the indicated antibodies.
D, primary T cells were transfected with either empty vector
or a plasmid encoding kinase-deficient HA-tagged Csk-SH3-SH2, and the
following day an experiment as described in the legend for A
was conducted. The numbers on top of the 4G10
blots are results from densitometric scanning analysis (ratio between
total
-chain phosphorylation and p16 of
; values are relative to
the ratio for unstimulated cells). The two 4G10 blots are derived from
different gels and should therefore only be compared qualitatively.
Expression of the HA-tagged Csk construct is also shown.
) resulted in a Csk kinase activity that was
4-fold higher than when PKI was added to the reaction mixture (Fig.
3B). Interestingly, co-incubation of C
with Csk, which is
activated through engagement of its SH2 domain with
Tyr(P)317 peptide, revealed an additional increase in Csk
activity compared with a similar reaction mixture where PKI was also
present (Fig. 3B). In addition, Csk-S364C, which is mutated
in the PKA phosphorylation site, could no longer be activated by PKA
but was still activated through engagement of its SH2 domain with
Tyr(P)317 peptide (Fig. 3B). Altogether this
indicates that with recombinant proteins in vitro,
activation of Csk by engagement of the Csk SH2 domain and by
PKA-mediated phosphorylation together induces a higher level of
activation of Csk (6-fold) than each mechanism contributes separately.
We next tested whether raft-associated Csk, which is bound to
phosphorylated Cbp/PAG, could gain additional increase in kinase
activity by PKA-mediated phosphorylation. We have previously shown that
PKA C and RI subunits are present in lipid rafts from T cells (10).
Furthermore, both forskolin (Fig. 3C) and PGE2
(not shown) induced cAMP production when purified lipid rafts from
Jurkat T cells were reconstituted with Mg-ATP. This means that all
components necessary for ligand-induced, PKA-mediated phosphorylation
of Csk are present in rafts. When purified lipid rafts from resting T
cells were reconstituted with Mg-ATP, stimulation with either
PGE2 or forskolin increased the activity of
immunoprecipitated Csk compared with control (Fig. 3D).
Since the amounts of co-immunoprecipitated Cbp/PAG were equal in all
the Csk immunoprecipitations assessed (Fig. 3D), the
observed differences in Csk kinase activity were most probably due to
PKA-mediated phosphorylation of Csk induced by the cAMP-elevating
agents. Altogether, this indicates that Csk already activated via
binding to Cbp/PAG in rafts can achieve an additional increase in
kinase activity upon PKA-mediated phosphorylation. This also means that
the specific phosphotransferase activity of PKA-phosphorylated,
Cbp/PAG-bound Csk is 6-8-fold higher than that of cytosolic,
unphosphorylated Csk.
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Fig. 3.
Csk activated by engagement of its SH2 domain
can be further activated by PKA-mediated phosphorylation.
A, the phosphotransferase activity of recombinant Csk-wt (1 ng/µl) toward the synthetic polyamino acid poly(Glu,Tyr) was measured
in the presence of either phospho-Tyr317-PAG peptide
(PY317) or dephospho-Tyr317-PAG peptide
(Y317) (10 µg/ml). B, the phosphotransferase
activity of recombinant Csk-wt or Csk-S364C was assessed as described
in the legend for A in the presence of PKA C subunit (1 ng
of active C/µl) with or without PKI (200 µg/ml) and
Tyr317/Tyr(P)317 PAG peptides (10 µg/ml).
C, isolated lipid raft fractions from Jurkat T cells were
reconstituted with Mg-ATP and stimulated with or without forskolin (100 µM, 3 min) at 30 °C, then cAMP levels were measured.
D, isolated lipid raft fractions from normal T cells were
mixed and reconstituted with Mg-ATP and stimulated with or without
forskolin or PGE2. Thereafter reactions were stopped by
addition of ice-cold lysis buffer (with
n-octyl- -D-glucoside), and phosphotransferase
activity of immunoprecipitated Csk was assessed as described in the
legend for A. Equal amounts of immunoprecipitated Csk or
co-immunoprecipitated Cbp/PAG present in each kinase reaction were
verified by immunoblotting, and one typical blot is shown. Data
represent the average (mean ± S.D.) of six independent
reactions
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Fig. 4.
Lipid raft-associated Csk is essential for
the inhibitory effect of cAMP on TCR-induced NFAT-AP-1 activation.
A, the effects of different PGE2 concentrations
on TCR-induced proliferation of purified T cells were assessed as
[3H]thymidine incorporation with or without preincubation
of the cAMP-antagonist Rp-8-bromo-cAMP (30 min, 1000 µM).
B, Jurkat TAg cells were transfected with a plasmid encoding
HA-tagged LAT-PKI. The next day the amounts of HA-tagged LAT-PKI
present in soluble (S) and particulate (P)
fractions were assessed (upper panel). In addition,
sucrose-gradient fractionation of transfected cells was also performed
(lower panel). The LAT and Csk blots serve as controls.
C, Jurkat TAg cells were co-transfected with
NFAT-AP1-luciferase reporter construct and plasmids encoding either
different Csk constructs or LAT-PKI chimeras. The following day, cells
were incubated with OKT-3 with or without PGE2 pretreatment
(different concentrations) or with PMA/ionomycin (25 ng/ml and 5 µM, respectively). After 6 h of incubation,
luciferase activity was assessed. Expression control is also shown.
D, same as described in the legend for C, but
prior to OKT-3 stimulation cells were pretreated or not with forskolin
(100 µM, 10 min).
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ACKNOWLEDGEMENTS |
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We are grateful for the technical assistance of G. Opsahl and G. Tjørhom.
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FOOTNOTES |
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* This work was supported by The Norwegian Cancer Society, The Program for Advanced Studies in Medicine, The Norwegian Research Council, Anders Jahre's Foundation, Novo Nordisk Research Foundation, and the Center of Molecular and Cellular Immunology (LN00A026) (to V. H.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
To whom correspondence should be addressed: Dept. of Medical
Biochemistry, Inst. of Basic Medical Sciences, University of Oslo,
P. O. Box 1112, N-0317 Oslo, Norway. Tel.: 47-22851454; Fax:
47-22851497; E-mail: kjetil.tasken@basalmed.uio.no.
Published, JBC Papers in Press, March 28, 2003, DOI 10.1074/jbc.C300077200
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ABBREVIATIONS |
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The abbreviations used are: TCR, T cell antigen receptor; PGE2, prostaglandin E2; PKA, protein kinase A; PKI, protein kinase inhibitor; Csk, C-terminal Src kinase; Cbp, Csk-binding protein; PAG, phosphoprotein associated with glycosphingolipid-enriched membrane domains; wt, wild type; HA, hemagglutinin epitope; IL, interleukin; SH, Src homology; LAT, linker for activation of T cells; NFAT, nuclear factor of activated T cells; AP-1, activator protein 1.
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REFERENCES |
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---|
1. | Werlen, G., and Palmer, E. (2002) Curr. Opin. Immunol. 14, 299-305[CrossRef][Medline] [Order article via Infotrieve] |
2. |
Hermiston, M. L.,
Xu, Z.,
Majeti, R.,
and Weiss, A.
(2002)
J. Clin. Invest.
109,
9-14 |
3. | Kawabuchi, M., Satomi, Y., Takao, T., Shimonishi, Y., Nada, S., Nagai, K., Tarakhovsky, A., and Okada, M. (2000) Nature 404, 999-1003[CrossRef][Medline] [Order article via Infotrieve] |
4. |
Brdicka, T.,
Pavlistova, D.,
Leo, A.,
Bruyns, E.,
Korinek, V.,
Angelisova, P.,
Scherer, J.,
Shevchenko, A.,
Hilgert, I.,
Cerny, J.,
Drbal, K.,
Kuramitsu, Y.,
Kornacker, B.,
Horejsi, V.,
and Schraven, B.
(2000)
J. Exp. Med.
191,
1591-1604 |
5. |
Torgersen, K. M.,
Vang, T.,
Abrahamsen, H.,
Yaqub, S.,
Horejsi, V.,
Schraven, B.,
Rolstad, B.,
Mustelin, T.,
and Tasken, K.
(2001)
J. Biol. Chem.
276,
29313-29318 |
6. | Chow, L. M., Fournel, M., Davidson, D., and Veillette, A. (1993) Nature 365, 156-160[CrossRef][Medline] [Order article via Infotrieve] |
7. | Schmedt, C., Saijo, K., Niidome, T., Kuhn, R., Aizawa, S., and Tarakhovsky, A. (1998) Nature 394, 901-904[CrossRef][Medline] [Order article via Infotrieve] |
8. | Kammer, G. M. (1988) Immunol. Today 9, 222-229[CrossRef][Medline] [Order article via Infotrieve] |
9. |
Skålhegg, B. S.,
Landmark, B. F.,
Døskeland, S. O.,
Hansson, V.,
Lea, T.,
and Jahnsen, T.
(1992)
J. Biol. Chem.
267,
15707-15714 |
10. |
Vang, T.,
Torgersen, K. M.,
Sundvold, V.,
Saxena, M.,
Levy, F. O.,
Skålhegg, B. S.,
Hansson, V.,
Mustelin, T.,
and Tasken, K.
(2001)
J. Exp. Med.
193,
497-507 |
11. | Torgersen, K. M., Vang, T., Abrahamsen, H., Yaqub, S., and Taskén, K. (2002) Cell. Signal. 14, 1-9[CrossRef][Medline] [Order article via Infotrieve] |
12. |
Aandahl, E. M.,
Aukrust, P.,
Skålhegg, B. S.,
Muller, F.,
Frøland, S. S.,
Hansson, V.,
and Taskén, K.
(1998)
FASEB J.
12,
855-862 |
13. |
Takeuchi, S.,
Takayama, Y.,
Ogawa, A.,
Tamura, K.,
and Okada, M.
(2000)
J. Biol. Chem.
275,
29183-29186 |
14. |
Yasuda, K.,
Nagafuku, M.,
Shima, T.,
Okada, M.,
Yagi, T.,
Yamada, T.,
Minaki, Y.,
Kato, A.,
Tani-Ichi, S.,
Hamaoka, T.,
and Kosugi, A.
(2002)
J. Immunol.
169,
2813-2817 |
15. |
Davidson, D.,
Bakinowski, M.,
Thomas, M. L.,
Horejsi, V.,
and Veillette, A.
(2003)
Mol. Cell. Biol.
23,
2017-2028 |