Evidence for a role for tyrosine phosphorylation of phospholipase C gamma 2 in collagen-induced platelet cytosolic calcium mobilization.
(1) The non-specific protein kinase C inhibitor, staurosporine, inhibited collagen-induced increases in cytosolic free Ca2+ while having no effect on Ca2+ mobilization by other platelet agonists. A more specific inhibitor of protein kinase C, Ro 31-8220, did not inhibit collagen-induced Ca2+ mobilization. Neither drug had an effect on platelet adhesion to collagen. (2) Staurosporine inhibited collagen-stimulated tyrosine phosphorylation, while Ro 31-8220 had no effect. (3) It also inhibited collagen-induced phosphatidic acid formation, inositol trisphosphate formation and arachidonic acid liberation. (4) Ro 31-8220 did not inhibit collagen-stimulated arachidonic acid formation, but it enhanced collagen-stimulated phosphatidic acid and inositol trisphosphate formation. (5) Immunoprecipitation of phospholipase C gamma 2 (PLC gamma 2) with a specific antibody demonstrated that PLC gamma 2 was phosphorylated on tyrosine after stimulation by collagen. (6) The phosphorylation of PLC gamma 2 was inhibited by staurosporine but not by Ro 31-8220. These results provide additional evidence that the mechanism of signal transduction for collagen is different from other platelet agonists and indicate that it involves activation of PLC gamma through a tyrosine kinase-dependent mechanism.
Daniel
J L
JL
Department of Pharmacology, Temple University Medical School, Philadelphia, PA 19140.
Dangelmaier
C
C
Smith
J B
JB
D000470:Alkaloids / Q000494:pharmacology; D016718:Arachidonic Acid / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism; D010766:Phosphorylation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011233:Precipitin Tests; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction; D019311:Staurosporine; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*
D000470:Alkaloids; D007211:Indoles; D007295:Inositol Phosphates; D010712:Phosphatidic Acids; D010975:Platelet Aggregation Inhibitors; D016718:Arachidonic Acid; D012701:Serotonin; D014443:Tyrosine; D003094:Collagen; D010738:Type C Phospholipases; D019311:Staurosporine; D002118:Calcium; C064758:Ro 31-8220