Rapid dephosphorylation of protein kinase C substrates by protein kinase A activators results from inhibition of diacylglycerol release.
The biochemical events encompassing the dephosphorylation of protein kinase C substrates by protein kinase A activators have been investigated in a neurotumor cell line, NCB-20. Treatment of [32P]orthophosphate-labeled cells with protein kinase A activators (e.g. forskolin, dibutyryl cAMP, prostaglandin E1) resulted in an inhibition of protein kinase C activity due to a failure of the protein kinase C complex to translocate into the membrane. Phospholipase C activity, as measured by the synchronous release of diacylglycerol and inositol phosphates (inositol 1,4,5-trisphosphate, inositol 1,4-bisphosphate, and inositol 1-phosphate) in response to bradykinin, was inhibited up to 50% following exposure to protein kinase A activators. At the same time, phospholipase C-specific inositol phospholipid substrates (phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate) were found to accumulate in NCB-20 cells following treatment with protein kinase A activators. This suggests that phospholipase C may be altered through protein kinase A-mediated protein phosphorylation. Second messenger generation (inositol phosphates, diacylglycerol, and Ca2+) is therefore inhibited through cyclic AMP-mediated shutdown of the inositol lipid cycle at the level of phospholipase C.
McAtee
P
P
Department of Biochemistry and Molecular Biology, University of Chicago, Illinois 60637.
Dawson
G
G
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D001921:Brain; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D004075:Diglycerides / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005989:Glycerides / Q000378:metabolism*; D006822:Hybrid Cells; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D009447:Neuroblastoma; D010710:Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D001095:Arachidonic Acids; D004075:Diglycerides; D005989:Glycerides; D007295:Inositol Phosphates; D010710:Phosphates; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D005576:Colforsin; D016718:Arachidonic Acid; D003994:Bucladesine; D011494:Protein Kinases; D011493:Protein Kinase C; D000527:Alprostadil; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D015056:1-Methyl-3-isobutylxanthine