Activation of a novel 33-kDa SER/THR kinase by tyrosine kinase and calpain in thrombin-stimulated platelets
Abstract number: P0717
Ido* M., Hayashi T., Suzuki K.
Mie University School of Medicine, Japan *Perinatal Center of Mie University Hospital, Japan;
Thrombin receptor/protease-activated receptor1 (PAR1) is a member of the G protein-coupled receptor family containing seven transmembrane domains. Thrombin cleaves extracellular region of PAR1 at the Arg41/Ser42 peptide bond and unmasks a tethered sequence beginning with Ser-Phe-Leu-Leu-Arg-Asn (thrombin receptor agonist peptide) (TRAP); subsequent binding of this ligand sequence to separate extracellular region of the receptor is coupled with a transmembrane signaling, leading to rapid activation of molecules that induces reorganization of the cytoskeletal signaling. Previously, we identified a 33-kDa Ser/Thr protein kinase (PK33) in platelets which activity is increased 10-fold by treatment with thrombin or TRAP. However, PK33-related signal transduction pathway and the role of PK33 in the platelet activation are still unclear. In the present study, we examined possible role of m-calpain and/or tyrosine kinase on thrombin- or TRAP-induced PK33 activation or platelet aggregation. PK33 activity was measured using in-gel renaturation protein kinase assay. Incubation of platelets with calpain inhibitor, calpeptin, or tyrosine kinase inhibitor, herbimycin A, inhibited thrombin- or TRAP-induced PK33 activation and platelet aggregation in a dose-dependent manner. Many signaling molecules including tyrosine kinases were found to be located in the specific membrane structure, lipid raft. Treatment of platelets with methyl-[fnof]À-cyclodextrin, which induces destruction of lipid raft, inhibited thrombin-induced PK33 activation. These findings suggest that m-calpain and tyrosine kinases are involved in the activation of PK33, which may play an important role in the platelet aggregation.
To cite this abstract use the following format:
Journal of Thrombosis and Haemostasis 2003; 1 Supplement 1 July: abstract number
|Subject:||Biochemistry and signal transduction|
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