Endothelial cell-dependent phosphorylation of a platelet protein mediated by cAMP- and cGMP-elevating factors.
We reported previously that a 46/50-kDa membrane-associated vasodilator-stimulated phosphoprotein (VASP) is phosphorylated in intact human platelets in response to both cGMP- and cAMP-elevating vasodilator drugs and presented evidence that this is mediated by cGMP- and cAMP-dependent protein kinases, respectively. VASP was recently purified and an antibody against it was developed which detects a phosphorylation-induced mobility change of VASP in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Halbrügge, M., Friedrich, C., Eigenthaler, M., Schanzenbächer, P., and Walter, U. (1990) J. Biol. Chem. 265, 3088-3093). We have now used these methods for the quantitative analysis of VASP phosphorylation during coincubations of human endothelial cells and human platelets. Endothelial cell-derived factors caused the rapid, stoichiometric, and reversible phosphorylation of platelet VASP during these coincubations. Other experiments indicated that the endothelium-derived factors which stimulate VASP phosphorylation are prostacyclin and endothelium-derived relaxing factor whose effects are mediated by cAMP/cAMP-dependent protein kinase and cGMP/cGMP-dependent protein kinase, respectively. The results suggest that VASP phosphorylation is an important component of the inhibitory effects of prostacyclin and endothelium-derived relaxing factor on platelet activation and that VASP phosphorylation is a useful biochemical marker for the interaction of endothelial cells and platelets.
Nolte
C
C
Medizinische Universitätsklinik, Klinische Forschergruppe, Würzburg, Federal Republic of Germany.
Eigenthaler
M
M
Schanzenbächer
P
P
Walter
U
U
D001345:Autoradiography; D001685:Biological Factors / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation
D001685:Biological Factors; D001798:Blood Proteins; D010750:Phosphoproteins; D009569:Nitric Oxide; D011464:Epoprostenol; D000242:Cyclic AMP; D006152:Cyclic GMP