Possible role of a cAMP-dependent phosphorylation in the calcium release mediated by inositol 1,4,5-trisphosphate in human platelet membrane vesicles.
The addition of inositol 1,4,5-trisphosphate (IP3) to a 45Ca-preloaded human platelet membrane fraction (dense tubular system) induced a transient release of Ca2+. When the vesicle fraction was loaded with 45Ca2+ to isotopic equilibrium in the presence of the catalytic subunit of the cAMP-dependent protein kinase, the level of Ca2+ uptake was increased and the subsequent IP3-induced Ca2+ release was enhanced. The stimulation was observed regardless of the IP3 concentration used, and was maximal with an enzyme concentration of 5 micrograms/ml. The addition of the protein kinase inhibitor prevented the stimulatory effect of the catalytic subunit on IP3-induced calcium release, and also abolished the calcium release detected in the absence of added enzyme. It is concluded that a cAMP-dependent protein phosphorylation may be involved in the regulation of the IP3-induced Ca2+ release in human platelets.
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D000242:Cyclic AMP / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000097:blood*; D008565:Membrane Proteins / Q000097:blood; D008566:Membranes / Q000378:metabolism; D010750:Phosphoproteins / Q000097:blood; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood; D013403:Sugar Phosphates / Q000097:blood*
D007295:Inositol Phosphates; D008565:Membrane Proteins; D010750:Phosphoproteins; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium