Cyclic AMP-dependent phosphorylation of the inositol-1,4,5-trisphosphate receptor inhibits Ca2+ release from platelet membranes.
Purified internal platelet membranes were treated with the catalytic subunit of protein kinase A to determine its effect on inositol-1,4,5-trisphosphate (IP3)-mediated Ca2+ release. Release kinetics were monitored using rhod-2, a Ca(2+)-specific fluorophore. Protein kinase A maximally inhibited the rate of IP3-mediated Ca2+ release by approximately 30% at saturating IP3 (10 microM). This inhibition was eliminated by pretreatment with a specific kinase inhibitor peptide. Partial purification of the platelet IP3 receptor showed that both endogenous kinases and added A kinase directly phosphorylate the receptor. Since the IP3 receptor is phosphorylated in the absence of added kinase, the observed inhibition (30%) by protein kinase A does not represent the maximal effect of phosphorylation.
Quinton
T M
TM
University of Louisville, School of Medicine, KY 40292.
Dean
W L
WL
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D015220:Calcium Channels; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000097:blood* / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D015220:Calcium Channels; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D013729:Terpenes; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D000252:Calcium-Transporting ATPases; D002118:Calcium