Prolactina potencializa a secreção de insulina via formação do complexo SNARE em ilhotas pancreaticas / Prolactin modulates the insulin secretion by SNARE complex formation in neonatal rat islets

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Prolactin induces maturation of insulin secretion in cultured neonatal rat islets. In this study, we investigated whether the improved secretory response to glucose caused by prolactin involves alteration in the expression, association and phosphorylation of several proteins that participate in these processes. Messenger RNA was extracted from neonatal rat islets cultured for five days in the presence of prolactin and reverse transcribed. Gene expression was analyzed by semi-quantitative RT-PCR and by western blotting for proteins. The gene transcription and protein expression of kinesin and MAP-2 were increased in prolactin-treated islets compared to the controls. The association and phosphorylation of proteins was analyzed by immunoprecipitation followed by western blotting, after acute exposure to prolactin. Prolactin increased the association between SNARE proteins and kinesin/MAP-2 while the association of munc-I8/syntaxin IA was decreased. Serine phosphorylation of SNAP-25, syntaxin IA, munc-18, MAP-2 was significantly higher whereas kinesin phosphorylation was decreased in prolactintreated islets. There was an increase in SNARE complex formation in islets stimulated with prolactin, 22 mM glucose, 40 mM K+, 200 f.lMcarbachol and 1 f.lMPMA (pKC activator). The prolactin-induced increase in the formation of SNARE complex and syntaxin IA phosphorylation was inhibited by PD098059, a blocker of the MAPK pathway. These findings indicate that prolactin primes pancreatic B-cells to release insulin by increasing the expression and phosphorylation/association of proteins implicated in the secretory machinery, probably via the MAPKlPKC pathway

ASSUNTO(S)

snare proteins ilhotas de kinesina kinesin langerhans islets of langerhans proteinas snare map2 prolactina prolactin

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