Mode of regulation of the extracellular signal-regulated kinases in the pancreatic beta-cell line MIN6 and their implication in the regulation of insulin gene transcription.
Physiological concentrations of glucose that lead to Ca2+ entry and insulin secretion activate extracellular signal-regulated protein kinases (ERK1 and ERK2) in the MIN6 pancreatic beta-cell line. Here we show that this activation is inhibited by the down-regulation of protein kinase C (PKC) and by genistein, an inhibitor of protein tyrosine kinases. In contrast with results obtained in other cell types, neither the epidermal growth factor activity nor the Src family protein tyrosine kinases seem to be involved in the Ca2+-dependent activation of ERKs. inhibition of tyrosine phosphatases by vanadate leads to the activation of ERKs. As observed in the response to glucose, this activation is dependent on Ca2+ entry through L-type voltage-dependent Ca2+ channels. Thus the activation of ERKs in response to glucose depends on PKC and possibly on a tyrosine kinase/tyrosine phosphatase couple. To define the role of ERK activation by glucose we studied the regulation of transcription of the insulin gene. We found that this transcription is regulated in the MIN6 cells in the same range of glucose concentration as in primary islets, and that specific inhibition of mitogen-activated protein kinase kinase, the direct activator of ERK, impaired the response of the insulin gene to glucose. This was observed by analysis of the transfected rat insulin I gene promoter activity and a Northern blot of endogenous insulin mRNA.
Benes
C
C
Equipe d'Accueil Signalisation Cellulaire et Parasites, UFR Cochin Université René Descartes, Pavillon Gustave Roussy (6ème étage), 27 rue du Faubourg Saint Jacques, 75674 Paris cedex 14, France.
Poitout
V
V
Marie
J C
JC
Martin-Perez
J
J
Roisin
M P
MP
Fagard
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D005947:Glucose / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007328:Insulin / Q000235:genetics*; D007515:Islets of Langerhans / Q000201:enzymology / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D014162:Transfection; D014638:Vanadates / Q000037:antagonists & inhibitors / Q000494:pharmacology
D002121:Calcium Channel Blockers; D007328:Insulin; D007527:Isoenzymes; D012333:RNA, Messenger; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017027:Protein Tyrosine Phosphatases; D005947:Glucose; D011188:Potassium; D002118:Calcium