TY - JOUR AB - High glucose (HG) has been shown to induce insulin resistance in both type 1 and type 2 diabetes. However, the molecular mechanism behind this phenomenon is unknown. Insulin receptor substrate (IRS) proteins are the key signaling molecules that mediate insulin's intracellular actions. Genetic and biological studies have shown that reductions in IRS1 and/or IRS2 protein levels are associated with insulin resistance. In this study we have shown that proteasome degradation of IRS1, but not of IRS2, is involved in HG-induced insulin resistance in Chinese hamster ovary (CHO) cells as well as in primary hepatocytes. To further investigate the molecular mechanism by which HG induces insulin resistance, we examined various molecular candidates with respect to their involvement in the reduction in IRS1 protein levels. In contrast to the insulin-induced degradation of IRS1, HG-induced degradation of IRS1 did not require IR signaling or phosphatidylinositol 3-kinase/Akt activity. We have identified glycogen synthase kinase 3beta (GSK3 beta or GSK3B as listed in the MGI Database) as a kinase required for HG-induced serine(332) phosphorylation, ubiquitination, and degradation of IRS1. Overexpression of IRS1 with mutation of serine(332) to alanine partially prevents HG-induced IRS1 degradation. Furthermore, overexpression of constitutively active GSK3 beta was sufficient to induce IRS1 degradation. Our data reveal the molecular mechanism of HG-induced insulin resistance, and support the notion that activation of GSK3 beta contributes to the induction of insulin resistance via phosphorylation of IRS1, triggering the ubiquitination and degradation of IRS1. AD - The Section of Endocrinology, The University of Chicago, 900 East 57th Street, Chicago, Illinois 60637, USA. AN - 20466847 AU - Leng, S. AU - Zhang, W. AU - Zheng, Y. AU - Liberman, Z. AU - Rhodes, C. J. AU - Eldar-Finkelman, H. AU - Sun, X. J. C2 - 3072280 DA - Aug DO - 10.1677/JOE-09-0456 ET - 2010/05/15 J2 - The Journal of endocrinology KW - Animals CHO Cells/metabolism Cricetinae Cricetulus Glucose/*metabolism Glycogen Synthase Kinase 3/*metabolism Hepatocytes/metabolism Immunoblotting Insulin Receptor Substrate Proteins/*metabolism *Insulin Resistance Phosphatidylinositol 3-Kinases/*metabolism Proteasome Endopeptidase Complex/*metabolism Signal Transduction *Ubiquitination LA - eng M1 - 2 M3 - Research Support, N.I.H., Extramural N1 - Leng, Sanhua Zhang, Wenshuo Zheng, Yanbin Liberman, Ziva Rhodes, Christopher J Eldar-Finkelman, Hagit Sun, Xiao Jian R01 DK060128/DK/NIDDK NIH HHS/ R01 DK062336-04/DK/NIDDK NIH HHS/ England J Endocrinol. 2010 Aug;206(2):171-81. Epub 2010 May 13. PY - 2010 SN - 1479-6805 (Electronic) 0022-0795 (Linking) SP - 171-81 ST - Glycogen synthase kinase 3 beta mediates high glucose-induced ubiquitination and proteasome degradation of insulin receptor substrate 1 T2 - J Endocrinol TI - Glycogen synthase kinase 3 beta mediates high glucose-induced ubiquitination and proteasome degradation of insulin receptor substrate 1 UR - http://www.ncbi.nlm.nih.gov/pubmed/20466847 VL - 206 ID - 134 ER -