Inhibition of thrombin-induced platelet activation by dioctanoylglycerol pretreatment is not correlated with the 47 kDa protein phosphorylation.
The effect of platelet pretreatment with moderate amounts of 1,2-dioctanoylglycerol on subsequent thrombin-induced activation and its correlation with the degree of protein phosphorylation is studied. Protein kinase C preactivation (treatment with 1 microM dioctanoylglycerol for 20 min) significantly reduces thrombin-promoted platelet aggregation, cytosolic calcium-rise, ATP-secretion and, albeit to a lesser extent, protein phosphorylation. Exposure of platelets to dioctanoylglycerol brings about a transient phosphorylation of a 47 kDa protein and a slight but more persistent phosphorylation of proteins of approximate molecular mass 26 and 68 kDa. It is hypothesized that the latter phosphoproteins are responsible for the inhibition of the thrombin-promoted platelet activation. Agonist-evoked aggregation is more affected by a long (20 min) rather than a short (1 min) pretreatment with dioctanoylglycerol, showing no correlation with the phosphorylation of the major substrates of protein kinase C.
Ruzzene
M
M
Department of Biological Chemistry, University of Padova, Italy.
Francesconi
M
M
Cavallini
L
L
Battistella
L
L
Deana
R
R
D000255:Adenosine Triphosphate / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D004075:Diglycerides / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008970:Molecular Weight; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000187:drug effects*; D013917:Thrombin / Q000037:antagonists & inhibitors*
D001798:Blood Proteins; D004075:Diglycerides; D010975:Platelet Aggregation Inhibitors; C044295:1,2-dioctanoylglycerol; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D013917:Thrombin; D002118:Calcium