OBJECTIVE—Insulin resistance associated with obesity and diabetes is ameliorated by specific overexpression of GLUT4 in skeletal muscle. The molecular mechanisms regulating skeletal muscle GLUT4 expression remain to be elucidated. The purpose of this study was to examine these mechanisms.
RESEARCH DESIGN AND METHODS AND RESULTS—Here, we report that AMP-activated protein kinase (AMPK) regulates GLUT4 transcription through the histone deacetylase (HDAC)5 transcriptional repressor. Overexpression of HDAC5 represses GLUT4 reporter gene expression, and HDAC inhibition in human primary myotubes increases endogenous GLUT4 gene expression. In vitro kinase assays, site-directed mutagenesis, and site-specific phospho-antibodies establish AMPK as an HDAC5 kinase that targets S259 and S498. Constitutively active but not dominant-negative AMPK and 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR) treatment in human primary myotubes results in HDAC5 phosphorylation at S259 and S498, association with 14-3-3 isoforms, and H3 acetylation. This reduces HDAC5 association with the GLUT4 promoter, as assessed through chromatin immunoprecipitation assays and HDAC5 nuclear export, concomitant with increases in GLUT4 gene expression. Gene reporter assays also confirm that the HDAC5 S259 and S498 sites are required for AICAR induction of GLUT4 transcription.
CONCLUSIONS—These data reveal a signal transduction pathway linking cellular energy charge to gene transcription directed at restoring cellular and whole-body energy balance and provide new therapeutic targets for the treatment and management of insulin resistance and type 2 diabetes.
- AICAR, 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside
- AMPK, AMP-activated protein kinase
- CaMK, calcium/calmodulin-dependent protein kinases
- ChIP, chromatin immunoprecipitation
- GEF, GLUT4 enhancer factor
- H3, histone 3
- H3K9, histone 3 lysine 9
- HAT, histone acetyl-transferase
- HDAC, histone deacetylase
- MEF, myocyte enhancer factor
- Received June 20, 2007.
- Accepted January 1, 2008.