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Previous Article | Table of Contents | Next Article 
Blood, Vol. 94 No. 11 (December 1), 1999:
pp. 3800-3805
Regulation of c-Jun-NH2 Terminal Kinase and Extracellular-Signal
Regulated Kinase in Human Platelets
By
Franck Bugaud,
Florence Nadal-Wollbold,
Sylviane Lévy-Toledano,
Jean-Philippe Rosa, and
Marijke Bryckaert
From U348 INSERM, IFR Circulation Lariboisière, Hôpital
Lariboisière, Paris, France.
 |
ABSTRACT |
Platelets are an interesting model for studying the relationship
betwen adhesion and mitogen-activated protein (MAP) kinase activation.
We have recently shown that in platelets, ERK2 was activated by
thrombin and downregulated by IIb 3
integrin engagement. Here we focused our attention on the c-Jun
NH2-terminal kinases (JNKs) and their activation in conditions of
platelet aggregation. We found that JNK1 was present in human platelets
and was activated after thrombin induction. JNK1 phosphorylation was
detected with low concentrations of thrombin (0.02 U/mL) and after 1 minute of thrombin-induced platelet aggregation. JNK1 activation was increased (fivefold) when fibrinogen binding to
IIb 3 integrin was inhibited by the
Arg-Gly-Asp-Ser (RGDS) peptide or
(Fab')2 fragments of a monoclonal antibody specific
for IIb 3, demonstrating that, like ERK2,
IIb 3 integrin engagement negatively
regulates JNK1 activation. Comparison of JNK1 activation by thrombin in stirred and unstirred platelets in the presence of RGDS peptide showed
a positive regulation by stirring itself, independently of
IIb 3 integrin engagement, which was
confirmed in a thrombasthenic patient lacking platelet
IIb 3. The same positive regulation by
stirring was found for ERK2. These results suggest that MAP kinases
(JNK1 and ERK2) are activated positively by thrombin and stirring. In
conclusion, we found that JNK1 is present in platelets and can be
activated after thrombin induction. Moreover, this is the first report
showing that two different MAP kinases (ERK2 and JNK1) are regulated
negatively by IIb 3 engagement and
positively by mechanical forces in platelets.
© 1999 by The American Society of Hematology.
 |
INTRODUCTION |
MITOGEN-ACTIVATED protein kinases (MAP
kinases) are a family of serine-threonine kinases1
activated by many stimuli, including growth factors and hormones, in
proliferative cells.2 This family consists of three
subgroups. The extracellular signal-regulated kinases (ERKs) are
involved in proliferation, adhesion, and cell progression.3,4 The p38MAP kinase and the c-Jun
amino-terminal kinases (JNKs) or stress-activated protein kinases
(SAPKs), which include the 46-kD JNK1 and 55-kD JNK2 isoforms, seem to
be involved in apoptosis.5,6 Activation of MAP kinases
requires dual phosphorylation at threonine and tyrosine
residues.7 Moreover, different kinases activate ERKs, JNKs,
and p38MAP kinase. ERKs, JNKs, and p38MAP kinase are phosphorylated by
MAP kinase/ERK kinase (MEK)1/2, MEK4, and MEK3/6,
respectively.8-10 The JNKs cascade is activated by various
stresses11 (UV irradiation, heat shock, x-ray irradiation,
osmotic shock), inflammatory cytokines12 (tumor necrosis
factor [TNF]- and interleukin-1), and weakly by
growth factors. Components of the JNK pathways are dependent on MAP
kinase kinase (MKKs), a serine/threonine kinase, p21-activated kinase
(PAK), and Ras-like guanosine triphosphate
(GTP)-binding proteins cdc42 and Rac.13-15
Platelets are nonproliferative cells and are a good model for studying
the signal transduction of MAP kinases and new functions. In platelets,
two MAP kinases, ERK and p38MAP kinase, have been identified.16,17 The ERK cascade is activated by thrombin, or collagen, and seems to involve MEK1/2 and protein kinase C (PKC).18,19 Recently, we found that
IIb 3 downregulates the ERK2 activation
induced by thrombin if engaged in fibrinogen-mediated platelet
aggregation.20 This was the first report of an integrin downregulating ERK2 activation during cell adhesion. p38MAP kinase is
activated by thrombin and seems to be involved in the phosphorylation of PLA2.21 The last subgroup of MAP kinases,
JNKs, has not been identified in platelets.
We determined the conditions of JNK activation during thrombin-induced
platelet aggregation. We also assessed the involvement of
IIb 3 integrin engagement in JNK
activation and compared it with that in ERK activation. We found that
JNK1 was (1) present and activated after thrombin induction; (2)
regulated negatively by IIb 3 engagement;
and (3) regulated positively by stirring, like ERK2 activation. This is
the first report showing that JNK1 is present and active in platelets
and has a similar regulation to ERK2. To our knowledge, this is also
the first report suggesting a direct mechanical induction of MAP
kinases in platelets.
 |
MATERIALS AND METHODS |
Reagents.
Bovine thrombin, synthetic peptides Arg-Gly-Asp-Ser
(RGDS), Arg-Gly-Glu-Ser (RGES), leupeptin, and aprotinin were purchased from Sigma (St Louis, MO). Protein-G PLUS-Agarose and the rabbit polyclonal antibody directed against JNK1 (C-17) were purchased from
Santa Cruz Biotechnology (Santa Cruz, CA), and rabbit polyclonal antibody directed against the phosphorylated forms of JNKs and ERKs was
obtained from Promega (Madison, WI). Donkey antirabbit horseradish peroxidase-conjugated IgG was obtained from Jackson Immuno
Research (West Grove, PA) and [ -32P]adenosine
triphosphate (ATP; 167 tera becquerel
[Tbq]/mmol) was obtained from ICN (Irvine, CA).
Electrophoresis reagents were obtained from Bio-Rad (Richmond, CA) and
Euromedex (Souffelweyersheim, France), and chemical products were
obtained from Merck (Darmstadt, Germany) and Prolabo (Paris, France).
Nitrocellulose sheets were purchased from Schleicher & Schuell (Dassel,
Germany). (Fab')2 fragments of the mouse monoclonal
IgG AP-2 specific for IIb 3 were an
extremely generous gift from Dr T.J. Kunicki (Scripps Clinic, La Jolla,
CA).22
Normal donors and patient.
Normal donors were not treated with any drug during the 2 weeks before
blood donation given with informed consent. A patient with Glanzmann's
thrombasthenia is characterized by absence of platelet aggregation and
fibrinogen binding, as previously described.23
Platelet preparation and aggregation.
Venous blood was obtained from healthy donors with their informed
consent. Platelets were isolated and washed by differential centrifugation in citrate buffer, pH 6, containing
10 4 mmol/L PGE1, 140 mmol/L NaCl, 5 mmol/L KCl, 12 mmol/L trisodium citrate, 10 mmol/L glucose, and 12.5 mmol/L sucrose, and then in the same buffer but without
PGE1. The platelet pellet was resuspended in 10 mmol/L
HEPES pH 7.4, 140 mmol/L NaCl, 3 mmol/L KCl, 0.5 mmol/L
MgCl2, 5 mmol/L NaHCO3, and 10 mmol/L glucose.
Cell concentration was adjusted to 5 × 108/mL. Platelets (0.4 mL) were
preincubated, without stirring, at 37°C for various times, with
various agonists. Platelet aggregation was then initiated by adding
bovine thrombin with or without constant stirring (1,200 rpm) in an
aggregometer cuvette (Chronolog dual beam aggregometer). Aggregation
was measured and is expressed as a percentage change in the
transmission of light, with the blank sample (buffer without platelets)
defined as 100%.
Immunoblotting.
Samples were subjected to immunoblotting as described
previously.24 Briefly, platelet aggregation was stopped by
addition of 40 µL of denaturing buffer (10% [wt/vol] sodium
dodecyl sulfate [SDS], 100 mmol/L NaCl, 50 mmol/L
Tris, 50 mmol/L NaF, 5 mmol/L EDTA, 40 mmol/L -glycerophosphate, 200 mmol/L sodium orthovanadate, 5 µg/mL leupeptin, 10 µg/mL aprotinin,
pH 7.4), and the samples were heated at 95°C for 5 minutes.
Proteins were separated by SDS-polyacrylamide gel electrophoresis
(SDS-PAGE), in a 12% polyacrylamide gel. Proteins were transferred to
nitrocellulose filters by semidry transfer (Enprotech, Natick, MA).
Filters were then incubated for 1 hour at room temperature with the
polyclonal primary antibody anti-JNK1-P (1:5,000) or anti-JNKs
(1:2,000) or anti-ERK2-P (1:20,000) or anti-ERKs (1:20,000). The
membranes were washed five times with Tris saline buffer without milk
and were then incubated with horseradish peroxidase-conjugated goat
antirabbit IgG (1:20,000) for 45 minutes at room temperature.
Immunoreactive bands were detected by chemiluminescence using the
Amersham ECL enhanced chemiluminescence system (Amersham, Arlington
Heights, IL).
Immunoprecipitation.
Platelet lysates were diluted in 50 mmol/L HEPES pH 7.4, 150 mmol/L
NaCl, 10% (vol/vol) glycerol, 1% (vol/vol) Triton X-100 (Sigma), 1.5 mmol/L MgCl2, 10 µg/mL of
leupeptin, 0.5 mmol/L sodium vanadate, and 2 mmol/L
EGTA, and were incubated overnight at 4°C with
anti-JNK1 antibody (2 µg/sample). They were then incubated with
protein-G PLUS agarose (40 µL, vol/vol) for 1 hour ar 4°C. Immune
complexes were collected by centrifugation. The sample was then
resuspended in 20 µL of kinase buffer (20 mmol/L HEPES, pH 7.4, 10 mmol/L MgCl2, 10 mmol/L p-nitrophenyl phosphate, 1 mmol/L
dithiothreitol) containing GST-Jun (2 µg), 50 µmol/L unlabeled ATP,
and 5 µCi of [ -32P]ATP per sample.24
After 10 minutes at 37°C, samples were subjected to SDS-PAGE, and
the gel was stained with Coomassie Blue (Sigma), dried, and autoradiographed.
 |
RESULTS AND DISCUSSION |
Thrombin induces JNK1 activation during platelet aggregation.
We first determined the conditions for thrombin-induced JNK1 activation
by incubating platelets with various concentrations of thrombin (0 to 1 U/mL) for 2 minutes under stirring conditions (Fig 1A). Phosphorylation was investigated
by Western blotting using an antibody that recognized phosphorylated
JNK1 and JNK2 (JNK1-P and JNK2-P). In resting platelets and after
induction with thrombin (0.01 U/mL), no phosphorylated JNK1 and/or JNK2 were found. JNK1-P was detected only after treatment with 0.02 U/mL
thrombin, reaching a maximum intensity at 0.2 U/mL. Moreover, we used
an antibody that recognized phosphorylated and nonphosphorylated JNKs
as internal control to ensure equal JNKs loading. We assessed JNK1
kinase activity in the same thrombin conditions, after JNK1 immunoprecipitation, by in vitro phosphorylation of GST-cJUN (see Materials and Methods). No GST-cJUN phosphorylation was observed in
resting platelets. In contrast, a significant increase in JNK1 activity
was detectable with 0.01 U/mL thrombin and reached a maximum at 0.05 U/mL thrombin. The fact that JNK1 activity appears at lower
concentrations of thrombin (0.01 U/mL) relative to its state of
phosphorylation is probably a result of the difference in the
sensitivity of the methods used, and/or in the antibodies used for
phosphorylation and kinase activity. Thus, JNK1 activation occurred
during thrombin-induced platelet aggregation. No JNK2 activation was
detected in the same conditions.

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| Fig 1.
Effect of thrombin on JNK1 activation. Platelets were
incubated at 37°C with various concentrations of thrombin for 2 minutes (A) or in the presence or absence of thrombin (1 U/mL) for
various times (B) as described in Materials and Methods. The reaction
was stopped by addition of lysis buffer containing SDS for Western
blotting and Triton X-100 for immunoprecipitation. JNK phosphorylation
and total JNKs were analyzed by Western blotting using a polyclonal
antibody recognizing JNK1-P and JNK2-P and a polyclonal antibody
recognizing total JNKs, respectively. For JNK activity, phosphorylated
GST-cJun was followed after immunoprecipitation of JNK1, with
[32P] ATP. These autoradiographs shown are typical of at
least three experiments. (A) Dose-dependent effect of thrombin on JNK
activation. Washed platelets were stimulated by incubation with various
concentrations of thrombin (0 to 1 U/mL) for 2 minutes with stirring.
(B) Time course of thrombin-mediated JNK activation. Washed platelets
were stimulated by incubation with 1 U/mL thrombin with stirring.
|
|
We used phosphorylation and kinase assays to investigate the time
course of JNK1 activation upon treatment with 1 U/mL thrombin under
stirring conditions (Fig 1B). In resting platelets, no JNK1 phosphorylation or activity was detected. In contrast, JNK1
phosphorylation and activity that was detected after 30 seconds or 1 minute, depending on the experiment, reached a maximum between 120 and
180 seconds. In these conditions of JNK1 phosphorylation, immunoblots
were probed with an antibody recognizing phosphorylated and
nonphosphorylated JNKs and confirmed equal levels of total JNKs in the
different platelet lysates. JNK1 was activated during platelet
aggregation, raising questions about the respective involvement of
IIb 3 integrin engagement or thrombin activation.
JNK1 activation is dependent on thrombin stimulation and is
upregulated by inhibition of
IIb 3
engagement.
We investigated thrombin-induced JNK1 activation in conditions of
inhibition of fibrinogen binding to integrin
IIb 3, and consequently, inhibition of
aggregation. The involvement of IIb 3 in
JNK1 activation was assessed using the RGDS peptide, a competitive inhibitor of fibrinogen binding to IIb 3.
In resting platelets, preincubation with RGDS alone, in the absence of
thrombin, did not activate JNK1 (Fig 2A and
B). In thrombin-activated platelets, however, preincubation with RGDS
for 30 seconds (0.5 and 1 mmol/L), which completely inhibited platelet
aggregation, did not prevent, but rather enhanced JNK1 phosphorylation
and activity after 2 minutes of thrombin activation (Fig 2A).
Quantification by densitometry demonstrated 471.2% ± 91.0% more
JNK1 phosphorylation in the presence of 1 mmol/L RGDS. A control RGES
peptide, which did not block platelet aggregation, did not
significantly affect (179.8% ± 37.0%) the thrombin-induced
phosphorylation of JNK1. We confirmed these results, by blocking
fibrinogen binding using (Fab')2 fragments of the
anti- IIb 3 monoclonal antibody AP-2
preincubated for 5 minutes before thrombin addition. Thrombin-induced
JNK1 phosphorylation and activity were increased dose-dependently by
addition of AP-2 (Fab')2, reaching a plateau at 10 µg/mL (Fig 2B). At this concentration (10 µg/mL), the values
obtained were similar to those for inhibition by RGDS: 409.6% ± 53.3% JNK1 phosphorylation and 644.2% ± 111.0% JNK1 activity.
Thus, the results of both experiments (RGDS and [Fab']2 fragments) suggest that activation of the
JNK1 pathway (1) occurs during thrombin aggregation independently of
IIb 3 engagement, and moreover, (2) is
downregulated by fibrinogen binding to
IIb 3. This negative control of JNK1
activation is possibly because of the presence and/or activation of
phosphatases in the same compartment of JNK1 in conditions of platelet
aggregation. Different phosphatases are associated with cytoskeleton
upon thrombin stimulation. PP2A, a serine/threonine phosphatase, which
can dephosphorylate MAP kinases in proliferative cells, is present in
the platelet cytoskeleton after thrombin induction.25
Moreover, tyrosine phosphatases like SHP1 are also present in the
cytoskeleton after IIb 3
engagement.26 The other possibility is that the kinases involved in the activation of JNK1 are partitioned in
different compartments after thrombin induction in the presence
or absence of IIb 3
engagement.

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| Fig 2.
Effect of inhibition of
IIb 3 engagement on thrombin-induced JNK1
activation. Washed platelets were preincubated at 37°C for 30 seconds in the presence or absence of peptides RGDS and RGES (0.5 mmol/L and 1 mmol/L) (A) or with various concentrations of the
(Fab')2 fragment of the
anti- IIb 3 monoclonal antibody AP-2 (0 to
20 µg/mL) for 5 minutes (B). They were then incubated with 0.2 U/mL
with stirring for 2 minutes. JNK1 phosphorylation was studied by
Western blotting and JNK1 activity by phosphorylation of GST-cJun, as
described in Fig 1. Autoradiographs were scanned with a laser
densitometer. For each experiment, the ratio of JNK1-P or GST-cJun was
normalized to that of platelets treated with thrombin alone and is
expressed as a relative intensity. Results are the means ± SEM for
four experiments.
|
|
Positive and negative regulation of thrombin-induced JNK1 activation:
Comparison with ERK2 activation.
We have previously shown that IIb 3
engagement negatively regulates ERK2 activation.20 So, we
compared thrombin-induced JNK and ERK activation in a patient with
Glanzmann's thrombasthenia, a disease that is characterized by a
quantitative defect in platelet IIb 3. In
these conditions, JNK1 activation in stirred platelets was higher in
the patient than in the control (Fig 3).
The level of upregulation in the patient and control with RGDS was
similar, strongly suggesting that this upregulation was caused by the
absence of IIb 3 engagement rather than by
any effect of RGDS itself. To ensure that the differences in the levels
of JNK-P between control and a patient with Glanzmann's thrombasthenia
are not caused by differences in JNK protein levels, immunoblots were probed with an antibody directed against phosphorylated and
nonphosphorylated JNKs. In these conditions, no difference in JNK
protein levels was observed. Finally, we also demonstrated ERK2
overactivation, as previously described.20

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| Fig 3.
Comparison of JNK1 and ERK2 activation in a Glanzmann's
thrombasthenia patient and control. Washed platelets from control in
the presence or absence of RGDS peptide and patient were stimulated
with 0.2 U/mL of thrombin under stirring conditions at the indicated
times. Then platelet lysates were solubilized and analyzed for ERK2 and
JNK1 activation.
|
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Thus, JNK1 maximal activation is obtained during thrombin activation of
platelets in conditions in which IIb 3,
and thus, aggregation are blocked (RGDS and monoclonal
anti- IIb 3) or absent (thrombasthenia).
However, all conditions implied that platelets were stirred. To test
whether stirring per se might affect JNK1 activation, we compared
thrombin-induced JNK1 activation in the absence or presence of stirring
with or without the RGDS peptide. In stirred platelets, in the presence
of the RGDS peptide, JNK1 was overactivated (566% ± 29% v
100% in the absence of RGDS) 2 minutes after the addition of thrombin
(Fig 4A). Interestingly, the absence of
stirring, whether in the presence or absence of RGDS, led only to a
partial overactivation (278% ± 69%) of JNK1. This is a strong
indication that stirring per se, or a factor depending on it, may
represent up to 50% of the JNK1 upregulation. The fact that stirring
yields maximal JNK1 activation in the presence versus the absence of
RGDS suggests that the remaining 50% upregulation is caused by the
blocking of IIb 3 engagement, per se. To
test whether positive regulation of JNK1 by stirring was specific of this MAP kinase, we next studied ERK2 activation by Western blotting using an anti-ERK-P antibody, in the same conditions of JNK1 activation (Fig 4A). We showed, as previously described,20 that ERK2
was overactivated in stirred platelets with the RGDS peptide. This ERK2
overactivation that reached 584% ± 21% after 2 minutes of thrombin induction (0.2 U/mL) was greater than that reported in a
previous study,20 probably because of the high sensitivity of the anti-ERK-P antibody used in our system. Stirred (584% ± 21%) and unstirred (365% ± 70%) platelets compared in the
presence of RGDS after 2 minutes of thrombin induction suggested that
ERK2 activation was also partly regulated by a factor dependent on stirring, but this positive regulation may be weaker for ERK2 (219%)
than for JNK1 (288%). Thus, (1) ERK2 and JNK1 activation induced by
thrombin were both negatively regulated by
IIb 3 engagement in aggregation itself,
and (2) stirring, per se, or a factor dependent on stirring is
involved, as a positive regulator in JNK1 activation and to a lesser
extent in ERK2 activation.

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| Fig 4.
Regulation of JNK1 and ERK2 activation. (A) JNK1
and ERK2 activation in stirred and unstirred platelets in the presence
or absence of RGDS peptide. Washed platelets were preincubated with or
without RGDS peptide (1 mmol/L) for 30 seconds and stimulated with
thrombin (0.2 U/mL) for various times, in the presence or absence of
stirring (+ stirring and + RGDS, ; + stirring and RGDS,
; stirring and + RGDS, ; stirring and RGDS, ).
The JNK1 phosphorylation (JNK1) and ERK2 phosphorylation (ERK2) of the
lysates were then assessed. Autoluminographs were scanned with a laser
densitometer. For each experiment, the ratio of phosphorylated JNK1 and
ERK2 was normalized to that of stirred platelets treated with thrombin
alone (2 minutes) expressed as a relative intensity. Results are the
means ± SEM for four experiments. (B) Effect of stirring on
thrombin-induced JNK1 and ERK2 activation in a thrombasthenic patient.
Stirred and unstirred platelets from Glanzmann's thrombasthenia
patient were stimulated with thrombin (0.2 U/mL) for various times. The
JNK1 phosphorylation and ERK2 phosphorylation and total JNKs and ERKs
of the lysates were investigated.
|
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To confirm the positive regulatory effect of stirring on MAP kinases,
we compared ERK2 and JNK1 activation in stirred and unstirred platelets
from a thrombasthenic patient lacking platelet IIb 3 (Fig 4B). In the conditions of
identical levels of total JNKs proteins loaded, the
activation of JNK1 and ERK2 in stirred platelets was higher than that
in unstirred platelets, confirming that stirring was a positive
regulator of JNK1 and ERK2 activation. We also confirmed that positive
regulation by stirring was stronger for JNK1 than for ERK2 as judged by
a lower stirred and unstirred ratio (x3) for ERK2 and x5 for JNK1 (Fig
4B). Altogether, our data suggest that JNK1 and ERK2, though to a
lesser extent, are activated by thrombin activation and stirring, and
downregulated by IIb 3 integrin
engagement. It is tempting to correlate these results with data showing
that the fluid shearing of endothelial cells increases the activation
of JNK much more than that of ERK.27 We investigated the
involvement of stirring itself or of a factor released from platelets
dependent on stirring in the positive regulation by quantifying
serotonin release in condition of stirred and
unstirred platelets in the presence or absence of the RGDS peptide. No
differences in serotonin release depending on the conditions used were
found (results not shown). The thromboxane analogue, U46619, activated
ERK2 and JNK1 (results not shown). We therefore tested the effect of
thrombin-induced thromboxane A2 formation as a secondary activator of
MAP kinase. In our conditions, flurbiprofen, which blocks
cyclooxygenase 1, had no effect on thrombin-induced JNK1 and ERK2
activation, suggesting that thromboxane A2 formation was not involved
(results not shown). Thus, though our data cannot totally exclude the
role of secreted factors, they are consistent with stirring itself
being involved, in the upregulation of JNK1 and ERK2 activation.
The role of MAP kinases in platelet physiology is unclear. However,
recent work28 has suggested that the Ras-initiated MAP kinase pathway suppresses integrin activation. Although these conclusions stem from work in Chinese hamster ovary cell line, a model
system may be very different from platelets. It is
tempting to speculate that in the physiopathologic conditions of shear stress and of platelet activation, MAP kinases (JNK1 and ERK2) may
serve as a suppressor of IIb 3 activation
and may act as a negative regulator of platelet activation. The partial
downregulation of JNK1 and ERK2 would thus be part of a feedback loop
of integrin engagement on MAP kinases activation.
We found that JNK1 and ERK2 were similarly regulated, but it is not
clear whether both activation pathways involved a common determinant in
platelets, and at which level of the signal transduction pathway the
MAP kinases were affected by the engagement of
IIb 3 integrin. It is well-known that Ras
cascade activation is involved in the activation of ERKs, but the role
of Ras in JNKs activation has only been recently
shown.27,29,30 Thus, thrombin-induced JNK and ERK
activation may involve a common pathway, and their negative regulation
may occur upstream of the JNKs and ERKs. In conclusion, this is the
first report showing (1) that JNK1 is present and can be activated in
platelets, and (2) that mechanical forces induce ERK1 and JNK2
activation in platelets.
 |
ACKNOWLEDGMENT |
The authors thank Dr T.J. Kunicki for generously donating
(Fab')2 fragments from the mouse monoclonal IgG AP-2
antibody specific for IIb 3. The authors
also thank E. Savariau and R. Nancel for graphic work.
 |
FOOTNOTES |
Submitted March 10, 1999; accepted July 2, 1999.
Supported by Institut National de la Recherche Médicale and by
grants from Ligue Nationale contre le Cancer (Comité de Paris), Fondation de France, and Association Pour la Recherche Contre le Cancer
(A.R.C.) (No 9697).
The publication costs of this
article were defrayed in part by
page charge payment. This article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. section
1734 solely to indicate this fact.
Address reprint requests to Marijke Bryckaert,
PhD, U348 INSERM, IFR Circulation Lariboisière,
Hôpital Lariboisière, 41 Bvd de la Chapelle, 75475 Paris
Cedex 10, France; e-mail:
marijke.bryckaert{at}inserm.lrb.ap-hop-paris.fr.
 |
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