TY - JOUR
T1 - Regulation of postaggregation events induced by protease-activated receptor 1 ligation in human platelets
T2 - Evidence of differential signaling pathways
AU - Ramars, Amanchy S S
AU - Mukhopadhyay, Saikat
AU - Dash, Debabrata
N1 - Funding Information:
This work was supported in part by grants received by D. Dash from the Council of Scientific and Industrial Research (CSIR), Indian Council of Medical Research (ICMR), and the Department of Biotechnology (DBT), Government of India. The donation from Alexander von Humboldt-Stiftung, Germany, is gratefully acknowledged. We thank Dr. Michael Berndt, Dr. Peter Presek, Dr. James Powers, and Dr. Hans Ochs for their generous gift of antibodies and reagents.
PY - 2002/2/15
Y1 - 2002/2/15
N2 - In a physiological milieu platelets continue to be exposed to agonists long after clot formation. We studied the regulation of postaggregation events consequent on protease-activated receptor (PAR) 1 ligation with either thrombin or the thrombin receptor-activating peptide (TRAP). Stimulation with TRAP (20 μM) but not with thrombin (1 U/ml) for 15 min evoked platelet disaggregation by about 30% and downregulation of high-affinity fibrinogen binding sites on integrin αIIbβ3 to nearly prestimulation levels. Concurrently, only TRAP disorganized the actin-based cytoskeleton, with decrease in the cytoskeletal content of focal contact-associated proteins like integrin αIIbβ3, Src, and focal adhesion kinase (FAK). While protein tyrosine kinases were activated during the initial period of platelet aggregation with either agonist, stimulation of protein tyrosine phosphatases determined the successive phase of reduced phosphotyrosine content. SHP-1, an abundant protein tyrosine phosphatase in the platelets, was tyrosine phosphorylated on challenge of PAR-1 and coprecipitated with two unidentified tyrosine phosphorylated proteins of 140 and 60 kDa; in addition, SHP-1 tyrosine phosphorylation (which is associated with enhanced phosphatase activity) was sustained until 15 min. Activity of calpain was upregulated following incubation with thrombin and not with TRAP. Collectively, these data suggest that signaling pathways elicited by PAR-1 agonists thrombin and TRAP are markedly different, which could have important implications on late platelet responses.
AB - In a physiological milieu platelets continue to be exposed to agonists long after clot formation. We studied the regulation of postaggregation events consequent on protease-activated receptor (PAR) 1 ligation with either thrombin or the thrombin receptor-activating peptide (TRAP). Stimulation with TRAP (20 μM) but not with thrombin (1 U/ml) for 15 min evoked platelet disaggregation by about 30% and downregulation of high-affinity fibrinogen binding sites on integrin αIIbβ3 to nearly prestimulation levels. Concurrently, only TRAP disorganized the actin-based cytoskeleton, with decrease in the cytoskeletal content of focal contact-associated proteins like integrin αIIbβ3, Src, and focal adhesion kinase (FAK). While protein tyrosine kinases were activated during the initial period of platelet aggregation with either agonist, stimulation of protein tyrosine phosphatases determined the successive phase of reduced phosphotyrosine content. SHP-1, an abundant protein tyrosine phosphatase in the platelets, was tyrosine phosphorylated on challenge of PAR-1 and coprecipitated with two unidentified tyrosine phosphorylated proteins of 140 and 60 kDa; in addition, SHP-1 tyrosine phosphorylation (which is associated with enhanced phosphatase activity) was sustained until 15 min. Activity of calpain was upregulated following incubation with thrombin and not with TRAP. Collectively, these data suggest that signaling pathways elicited by PAR-1 agonists thrombin and TRAP are markedly different, which could have important implications on late platelet responses.
KW - Calpain
KW - Cytoskeleton
KW - Integrin αβ
KW - Platelet
KW - Protease-activated receptor 1
KW - Protein tyrosine kinases
KW - Protein tyrosine phosphatases
KW - Thrombin
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U2 - 10.1006/abbi.2001.2724
DO - 10.1006/abbi.2001.2724
M3 - Article
C2 - 11831857
AN - SCOPUS:0037085238
SN - 0003-9861
VL - 398
SP - 253
EP - 260
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -