Op-jbio150120 429..436

The 50-AMP-activated protein kinase (AMPK) functions as a cellular energy sensor. 5-Aminoimidazole-4-carboxyamide-1-b-D-ribofranoside (AICAR) is a chemical activator of AMPK. In the liver, AICAR suppresses expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene. The rat enhancer of splitand hairyrelated protein-2 (SHARP-2) is an insulin-inducible transcriptional repressor and its target is the PEPCK gene. In this study, we examined an issue of whether the SHARP-2 gene expression is regulated by AICAR via the AMPK. AICAR increased the level of SHARP-2 mRNA in H4IIE cells. Whereas an AMPK inhibitor, compound-C, had no effects on the AICAR-induction, inhibitors for both phosphoinositide 3-kinase (PI 3-K) and protein kinase C (PKC) completely diminished the effects of AICAR. Western blot analyses showed that AICAR rapidly activated atypical PKC lambda (aPKCj). In addition, when a dominant negative form of aPKCj was expressed, the induction of SHARP-2 mRNA level by AICAR was inhibited. Calcium ion is not required for the activation of aPKCj. A calcium ion-chelating reagent had no effects on the AICARinduction. Furthermore, the AICAR-induction was inhibited by treatment with an RNA polymerase inhibitor or a protein synthesis inhibitor. Thus, we conclude that the AICAR-induction of the SHARP-2 gene is mediated at transcription level by a PI 3-K/aPKCj pathway.