Evidence implicating protein kinase C in exocytosis from electropermeabilized bovine chromaffin cells.
The calcium sensitivity of exocytosis from electro-permeabilized chromaffin cells is increased by activators of protein kinase C, such as TPA and certain phorbol esters, diacylglycerols, and mezerein. A range of putative inhibitors of protein kinase C block both the phorbol ester-sensitive component of secretion and also the underlying insensitive component. These inhibitors are also shown to inhibit medulla protein kinase C activity in vitro. The extent of secretion is reduced when electro-permeabilized cells are exposed to Ca2+ levels much in excess of 50 microM. The onset of inhibition is faster than the relatively slow rate of Ca-dependent exocytosis and is insensitive to inhibitors of proteolysis. Adrenal medulla protein kinase C activity is also irreversibly inhibited by high Ca2+ concentrations. Both the secretory response and the protein kinase C activity in vitro have similar nucleotide and cation specificities. Although these data do not definitely establish an involvement of protein kinase C in exocytosis, none argue against it.
Knight
D E
DE
MRC Secretory Mechanism Group, Division of Biomedical Sciences, Kings College, London, England.
Sugden
D
D
Baker
P F
PF
D000818:Animals; D001241:Aspirin / Q000494:pharmacology; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology / Q000502:physiology; D002395:Catecholamines / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability; D002838:Chromaffin System / Q000166:cytology / Q000502:physiology*; D004075:Diglycerides / Q000096:biosynthesis / Q000494:pharmacology; D004558:Electric Stimulation; D005089:Exocytosis / Q000187:drug effects; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007294:Inositol / Q000494:pharmacology; D007700:Kinetics; D008970:Molecular Weight; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000502:physiology*; D013379:Substrate Specificity
D002395:Catecholamines; D002413:Cations, Divalent; D004075:Diglycerides; D010703:Phorbol Esters; D007294:Inositol; D011493:Protein Kinase C; D001241:Aspirin; D002118:Calcium; D007213:Indomethacin