Insulin differentially regulates SAPKs/JNKs and ERKs in CHO cells overexpressing human insulin receptors.

In the present study, we compared the ability of insulin to regulate SAPKs/JNKs and ERKs in CHO cells overexpressing human insulin receptors. We show that acute insulin treatment induced a time-dependent increase both in SAPK/JNK and ERK activity but with distinct kinetics. PI-3-kinase inhibition by wortmannin completely blocked insulin activation of SAPKs/JNKs, whereas it partially decreased ERK activation. Prolonged exposure to insulin caused a marked inhibition of SAPK/JNK activity while it induced a sustained activation of ERKs. Insulin inhibition of SAPKs/JNKs was partly due to decreased tyrosine phosphorylation of JNK2. These data indicate that insulin differentially regulates SAPKs/JNKs and ERKs. Moreover, they provide the first evidence that insulin exerts opposite effects on SAPK/JNK activity according to the time of cell treatment.