Different requirements for protein kinase C activation and Ca2+-independent insulin secretion in response to guanine nucleotides. Endogenously generated diacylglycerol requires elevated Ca2+ for kinase C insertion into membranes.

Détails

ID Serval
serval:BIB_E05A9D49DC68
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Different requirements for protein kinase C activation and Ca2+-independent insulin secretion in response to guanine nucleotides. Endogenously generated diacylglycerol requires elevated Ca2+ for kinase C insertion into membranes.
Périodique
Journal of Biological Chemistry
Auteur⸱e⸱s
Regazzi R., Li G., Ullrich S., Jaggi C., Wollheim C.B.
ISSN
0021-9258
Statut éditorial
Publié
Date de publication
06/1989
Peer-reviewed
Oui
Volume
264
Numéro
17
Pages
9939-9944
Langue
anglais
Résumé
Electrically permeabilized RINm5F cells were used to assess the factors required for activation of protein kinase C (PKC) and insulin secretion. PKC was activated either by phorbol 12-myristate 13-acetate (PMA) or by the generation of endogenous diacylglycerol in response to the nonhydrolyzable guanine nucleotide analog guanosine 5'-O-(thiotriphosphate) (GTP gamma S). As shown previously, both PMA and GTP gamma S elicit Ca2+-independent insulin secretion. This effect was mimicked by guanyl-5'-yl imidodiphosphate (Gpp(NH)p) but not by guanosine 5'-O-(3-fluorotriphosphate) and guanosine 5'-O-(3-phenyltriphosphate) possessing only one negative charge in the gamma-phosphate group. The action of PMA was mediated by PKC, since the agent caused both phosphorylation of specific protein substrates and association of the enzyme with cellular membranes. This translocation was independent of the Ca2+ concentration employed. In contrast, GTP gamma S only promoted association of PKC with membranes at 10(-6) and 10(-5) M Ca2+ and failed to alter significantly protein phosphorylation in the absence of Ca2+. Neither Gpp(NH)p, which stimulates insulin release, nor the other two GTP analogs, increased the proportion of PKC associated with membranes. To verify that the Ca2+-dependent effect of GTP gamma S on PKC is due to activation of phospholipase C, we measured the generation of diacylglycerol. GTP gamma S indeed stimulated diacylglycerol production in the leaky cells by about 50% at Ca2+ concentrations between 10(-7) and 10(-5) M, an effect which was almost abolished in the absence of Ca2+. Thus, at 10(-7) M Ca2+, the concentration found in resting intact cells, the generated diacylglycerol was not sufficient to cause PKC insertion into the membrane, demonstrating that both elevated Ca2+ and diacylglycerol are necessary for translocation to occur. It is concluded that while PKC activation by PMA elicits Ca2+-independent insulin secretion, the kinase seems not to mediate the stimulatory action of GTP analogs in the absence of Ca2+.
Mots-clé
Animals, Calcium/pharmacology, Cell Line, Cell Membrane/enzymology, Cell Membrane Permeability, Diglycerides/physiology, Enzyme Activation, Glycerides/physiology, Guanine Nucleotides/pharmacology, Guanosine 5'-O-(3-Thiotriphosphate), Guanosine Triphosphate/analogs & derivatives, Guanosine Triphosphate/pharmacology, Insulin/secretion, Kinetics, Phosphorylation, Protein Kinase C/metabolism, Tetradecanoylphorbol Acetate/pharmacology, Thionucleotides/pharmacology
Pubmed
Web of science
Création de la notice
24/01/2008 14:30
Dernière modification de la notice
20/08/2019 16:04
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