Effects of Ca2+, calmodulin and cyclic AMP on the phosphorylation of endogenous proteins by homogenates of rt islets of langerhans.
Biochim Biophys Acta
; 714(2): 313-9, 1982 Feb 02.
Article
em En
| MEDLINE
| ID: mdl-6275912
ABSTRACT
Activation of Ca2+ -calmodulin- and cyclic AMP-dependent protein kinases has been suggested to be involved in stimulus-secretion coupling in the pancreatic beta-cell. To study the properties of suc kinases and their endogenous protein substrates homogenates of rat islets of Langerhans were incubated with [gamma-32P]ATP. Phosphorylated proteins were separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis and detected by autoradiography. The phosphorylation of certain proteins could be enhanced by Ca2+ plus calmodulin or by cyclic AMP. The major effect of Ca2+ and calmodulin was to stimulate the phosphorylation of a protein (P53) of molecular weight 53,100 +/- 500 (n = 15). Maximum phosphorylation of protein P53 occurred within 2 min with 2 micrometers free Ca2+ and 0.7 micrometers calmodulin. Incorporation of label into protein P53 was inhibited by trifluoperazine or W7 but not by cyclic AMP-dependent protein kinase inhibitor. Phosphorylation of a proteins of similar molecular weight could be enhanced to a lesser extent in the absence of Ca2+ but in the presence of cyclic AMP and 3-isobutylmethylxanthine this phosphorylation was blocked by cyclic AMP-dependent protein kinase inhibitor. Cyclic AMP also stimulated incorporation of label into polypeptides of molecular weights 55,000 and 70-80,000. The results are consistent with the hypothesis that protein phosphorylation mechanisms may play a role in the regulation of insulin secretion.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas Quinases
/
Proteínas de Ligação ao Cálcio
/
Calmodulina
/
Cálcio
/
Ilhotas Pancreáticas
/
AMP Cíclico
Limite:
Animals
Idioma:
En
Ano de publicação:
1982
Tipo de documento:
Article