The tyrosine kinase inhibitors methyl 2,5-dihydroxycinnamate and genistein reduce thrombin-evoked tyrosine phosphorylation and Ca2+ entry in human platelets.
Platelet activation is associated with the phosphorylation of a number of platelet proteins at tyrosine residues. The significance of this is unknown. Here we have investigated the effects of two tyrosine kinase inhibitors, methyl 2,5-dihydroxycinnamate and genistein, on thrombin-evoked protein tyrosine phosphorylation and Ca2+ signal generation in fura-2-loaded human platelets. Both compounds inhibited thrombin-evoked tyrosine phosphorylation and reduced the elevation of [Ca2+]i in the presence, but not the absence, of external Ca2+. This suggested a selective inhibition of thrombin-evoked Ca2+ entry but not release from internal stores. Both compounds also reduced thrombin-evoked Mn2+ entry. In contrast, selective blockade of protein kinase C with Ro 31/8220-002 potentiated the thrombin-evoked Ca2+ signal. These data are compatible with a role for protein tyrosine phosphorylation contributing to thrombin-evoked Ca2+ entry in human platelets.
Sargeant
P
P
Physiological Laboratory, University of Cambridge, UK.
Farndale
R W
RW
Sage
S O
SO
D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D002934:Cinnamates / Q000494:pharmacology*; D004347:Drug Interactions; D004591:Electrophoresis, Polyacrylamide Gel; D019833:Genistein; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007529:Isoflavones / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism*
D002934:Cinnamates; D007211:Indoles; D007529:Isoflavones; D014443:Tyrosine; C004742:daidzein; C067472:methyl 2,5-dihydroxycinnamate; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D013917:Thrombin; D002118:Calcium; C064758:Ro 31-8220