Ca2+ influx causes rapid translocation of protein kinase C to membranes. Studies of the effects of secretagogues in adrenal chromaffin cells.
In bovine adrenal chromaffin cells nicotinic stimulation or a depolarizing concentration of K+ caused a rapid, transient translocation to membranes of as much as 14% of the total cellular protein kinase C activity. The quantitative relationship between membrane-bound protein kinase C and Ca2+-dependent secretion was determined in cells rendered leaky by digitonin treatment. Intact cells were incubated with various concentrations of 12-O-tetradecanoylphorbol-13-acetate (TPA) to activate and cause translocation of protein kinase C to membrane before permeabilization in the presence of Ca2+. For the same amount of membrane-bound protein kinase C, a similar degree of enhancement of Ca2+-dependent secretion occurred in cells incubated for 1 or 30 min with TPA. Translocation of as little as 2-3% of the cellular protein kinase C to the membrane enhanced Ca2+-dependent secretion by 25-30%. Muscarinic agonists caused a 5% increase in membrane-bound protein kinase C at 2 s which rapidly reversed. Nicotinic and muscarinic receptor-mediated increases in membrane-bound protein kinase C were additive at 10 s and synergistic at 3 min. Muscarinic stimulation enhanced nicotinic receptor-dependent secretion. Prior incubation with TPA caused a similar enhancement of nicotinic-mediated secretion. The data indicate that protein kinase C which is translocated within seconds of stimulation of the cells with a nicotinic agonist or elevated K+ probably enhances the secretory response immediately or soon after exocytosis begins. In addition, the muscarinic receptor-mediated enhancement of nicotinic receptor-stimulated secretion may be due to newly activated protein kinase C.
TerBush
D R
DR
Department of Pharmacology, University of Michigan, Ann Arbor 48109-0626.
Bittner
M A
MA
Holz
R W
RW
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology*; D002838:Chromaffin System / Q000201:enzymology*; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D008566:Membranes / Q000201:enzymology; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013997:Time Factors
D008688:Methacholine Compounds; D016210:Methacholine Chloride; D005711:Gallopamil; D004246:Dimethylphenylpiperazinium Iodide; D011493:Protein Kinase C; D011188:Potassium; D002118:Calcium