Insulin-mediated cell proliferation and survival involve inhibition of c-Jun N-terminal kinases through a phosphatidylinositol 3-kinase- and mitogen-activated protein kinase phosphatase-1-dependent pathway.
We previously reported that long term treatment with insulin led to sustained inhibition of c-Jun N-terminal kinases (JNKs) in CHO cells overexpressing insulin receptors. Here we investigated the signaling molecules involved in insulin inhibition of JNKs, focusing on phosphatidylinositol 3-kinase (PI 3-K) and mitogen-activated protein kinase phosphatase-1 (MKP-1). In addition, we examined the relevance of JNK inhibition for insulin-mediated proliferation and survival. Insulin inhibition of JNKs was mediated by PI 3-K, as it was blocked by wortmannin and LY294002 and required the de novo synthesis of a phosphatase(s), as it was abolished by orthovanadate and actinomycin D. MKP-1 was a good candidate because 1) insulin stimulation of MKP-1 expression correlated with insulin inhibition of JNKs; 2) insulin stimulation of MKP-1 expression, like insulin inhibition of JNKs, was mediated by PI 3-K; and 3) the transient expression of an antisense MKP-1 RNA reduced the insulin inhibitory effect on JNKs. The overexpression of a dominant negative JNK1 mutant increased insulin stimulation of DNA synthesis and mimicked the protective effect of insulin against serum withdrawal-induced apoptosis. The overexpression of wild-type JNK1 or antisense MKP-1 RNA reduced the proliferative and/or antiapoptotic responses to insulin. Altogether, these results demonstrate that insulin inhibits JNKs through a PI 3-K- and MKP-1-dependent pathway and provide evidence for a key role for JNK inhibition in insulin regulation of proliferation and survival.
Desbois-Mouthon
C
C
INSERM U-402, Faculté de Médecine Saint-Antoine, Paris, France. desbois@stantoine.inserm.fr
Cadoret
A
A
Blivet-Van Eggelpoël
M J
MJ
Bertrand
F
F
Caron
M
M
Atfi
A
A
Cherqui
G
G
Capeau
J
J
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D016466:CHO Cells; D002452:Cell Count / Q000187:drug effects; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D054638:Dual Specificity Phosphatase 1; D006003:Glycogen / Q000096:biosynthesis; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010957:Plasmids / Q000235:genetics; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014162:Transfection / Q000235:genetics
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D007328:Insulin; D006003:Glycogen; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases