AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism; it is inhibited under obese conditions and is activated by exercise and by many anti-diabetic drugs. Emerging evidence also suggests that AMPK regulates cell differentiation, but the underlying mechanisms are unclear. We hypothesized that AMPK regulates cell differentiation via altering -catenin expression, which involves phosphorylation of class IIa histone deacetylase 5 (HDAC5). In both C3H10T1/2 cells and mouse embryonic fibroblasts (MEFs), AMPK activity was positively correlated with -catenin content. Chemical inhibition of HDAC5 increased -catenin mRNA expression. HDAC5 overexpression reduced and HDAC5 knockdown increased H3K9 acetylation and cellular -catenin content. HDAC5 formed a complex with myocyte enhancer factor-2 to down-regulate -catenin mRNA expression. AMPK phosphorylated HDAC5, which promoted HDAC5 exportation from the nucleus; mutation of two phosphorylation sites in HDAC5, Ser-259 and -498, abolished the regulatory role of AMPK on -catenin expression. In conclusion, AMPK promotes -catenin expression through phosphorylation of HDAC5, which reduces HDAC5 interaction with the -catenin promoter via myocyte enhancer factor-2. Thus, the data indicate that AMPK regulates cell differentiation and development via cross-talk with the wingless and Int (Wnt)/ -catenin signaling pathway.
AMP-activated protein kinase (AMPK),2 a heterotrimeric enzyme composed of ␣, , and ␥ subunits, is recognized as a critical regulator of energy metabolism (1-3). In addition to its capacity to acutely regulate the activity of metabolic enzymes through phosphorylation, AMPK also regulates gene expression (4 -9). Emerging evidence also suggests that AMPK regulates cell differentiation and tissue development (10 -12). Recently, it was shown that double knock-out of AMPK ␣1 and ␣2 subunits is lethal to mice at embryonic stage 10.5 (13), further confirming the important role of AMPK in early development. Mechanisms linking AMPK to cell differentiation and animal development, however, remain poorly defined.-Catenin is a key mediator of Wingless and Int (Wnt)/-catenin signaling pathway, which is required for early embryonic development (14, 15), cell proliferation, and differentiation (16 -18). We postulate that AMPK regulates cell differentiation through cross-talk with the Wnt/-catenin signaling pathway. We previously observed that AMPK phosphorylates -catenin, which enhances -catenin stability (19). In this study we further observed that the mRNA expression of -catenin was promoted by AMPK and suggested that histone deacetylase 5 (HDAC5) has an essential role in linking AMPK with -catenin expression.Epigenetic modifications including histone acetylation and methylation and DNA methylation regulate gene transcription (20,21). Histone acetylation is regulated by histone acetyltransferase and HDAC (22). HDAC5 belongs to the class IIa HDAC family and acts as a conserved transcriptional repressor. HDAC5 interacts with myocyte enhancer fact...