Insulin-induced c-Jun N-terminal kinase activation is negatively regulated by protein kinase C delta.
We investigated the role of protein kinase C (PKC) in insulin-induced c-Jun N-terminal kinase (JNK) activation in rat 1 fibroblasts expressing human insulin receptors. Insulin treatment led to increased SAPK/ERK kinase 1 (SEK1) phosphorylation, and then stimulated JNK activity in a dose- and time-dependent manner, as measured either by a solid-phase kinase assay using glutathione S-transferase (GST)-c-Jun fusion protein as a substrate, or by quantitation of the levels of phosphorylated JNK by Western blotting using anti-phospho-JNK antibody. Insulin-induced JNK activation was potentiated by either preincubating cells with 2 nM GF109203X (PKC inhibitor) or down-regulation of PKC by overnight treatment with 100 nM tetradecanoyl phorbol acetate. In contrast, brief preincubation with 100 nM tetradecanoyl phorbol acetate inhibited the insulin- induced JNK activation. Furthermore, we found that 5 microM rottlerin, a PKCdelta inhibitor, enhanced insulin-induced JNK activation, but a PKCbeta inhibitor, LY333531, had no effect. Consistent with these findings, overexpression of PKCdelta led to decreased insulin-induced JNK activation, whereas overexpression of PKCbeta had no effect. Although overexpression of wild-type PKCdelta attenuated insulin-induced JNK activation, a kinase-dead PKCdelta mutant did not cause such attenuation. Finally, we found that the magnitude of insulin-induced JNK activation was inversely correlated with the expression level of PKCdelta among different cell lines. In conclusion, the expression of PKCdelta may negatively regulate insulin-induced JNK activation.
Morino
K
K
Third Department of Medicine, Shiga University of Medical Science, Seta, Otsu, Shiga 520-2192, Japan.
Maegawa
H
H
Fujita
T
T
Takahara
N
N
Egawa
K
K
Kashiwagi
A
A
Kikkawa
R
R
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002460:Cell Line; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000201:enzymology; D015870:Gene Expression; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology*; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000098:Acetophenones; D001578:Benzopyrans; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D007328:Insulin; D007527:Isoenzymes; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; C085746:rottlerin; D005982:Glutathione Transferase; D011972:Receptor, Insulin; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases; D013755:Tetradecanoylphorbol Acetate