ISSN:
1573-4919
Keywords:
Ca2+-pump
;
Ca2+-ATPase
;
protein kinase A
;
protein kinase C
;
calmodulin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract The regulation of the guinea-pig pancreatic acinar plasma membrane Ca2+ pump by protein kinase A, protein kinase C and calmodulin was investigated. The results were compared with the effects of these regulators on the high affinity Ca2+-ATPase found in this membrane preparation. The catalytic subunit of cyclic AMP-dependent protein kinase stimulated Ca2+ transport 2-fold, but had no effect on Ca2+-dependent ATPase activity. Purified protein kinase C, the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate and diacylglycerol derivative, 1-stearoyl-2-arachidonoyl-sn-glycerol, failed to stimulate the Ca2+-uptake but augmented the Ca2+-dependent ATPase activity. Exogenously added calmodulin failed to stimulate either activity. In addition, two antagonists of calmodulin activity, trifluoperazine and compound 48/80 produced a concentration-dependent inhibition of Ca2+-transport. These data suggest the presence of endogenous calmodulin within guinea-pig pancreatic acinar plasma membranes. Both calmodulin antagonists failed to influence the Ca2+-dependent ATPase activity. The ability of boiled extracts from guinea-pig pancreatic acinar plasma membranes to stimulate the Ca2+-ATPase activity in calmodulin-depleted erythrocyte plasma membranes confirmed the presence of endogenous calmodulin. Our results imply a role for calmodulin and cAMP-dependent protein kinase, but not protein kinase C, in the regulation of Ca2+ efflux from pancreatic acinar cells. These results also provide further evidence suggesting that the high affinity Ca2+-ATPase does not catalyze the plasma membrane Ca2+-transport activity observed in pancreatic acini.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00227572
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