Abstract

Insulin upregulates hexokinase II (HKII) expression in skeletal muscle, and this effect is altered in type 2 diabetic patients. This study was conducted to identify the transcription factors that mediate the effect of insulin on HKII gene expression in human muscle. We have cloned the promoter region of the HKII gene and investigated its regulation in a primary culture of human skeletal muscle cells. We defined a region (−369/−270) that conferred the transcriptional response to insulin. This region contains a sterol regulatory element (SRE) that interacted with the recombinant active form of SRE binding protein-1c (SREBP-1c) in electrophoretic mobility shift assays, and, using chromatin immunoprecipitation assay, we showed that endogenous SREBP-1 interacted directly with the promoter region of the HKII gene in human muscle cells. Mutation of the SRE sequence completely suppressed the response of the promoter to insulin stimulation. Finally, overexpression of the rodent mature form of SREBP-1c (adipocyte determination and differentiation factor-1 [ADD1]-403) was able to reproduce insulin action, whereas a dominant-negative form (ADD1-403R) prevented the effect of insulin on HKII promoter constructs. These results demonstrate that SREBP-1c is involved in the effect of insulin on HKII gene transcription and indicate that it is one of the mediators of insulin action on gene expression in human skeletal muscle.