Regulation of insulin receptor substrate 1 (IRS-1)/AKT kinase-mediated insulin signaling by O-Linked beta-N-acetylglucosamine in 3T3-L1 adipocytes.
Increased O-linked beta-N-acetylglucosamine (O-GlcNAc) is associated with insulin resistance in muscle and adipocytes. Upon insulin treatment of insulin-responsive adipocytes, O-GlcNAcylation of several proteins is increased. Key insulin signaling proteins, including IRS-1, IRS-2, and PDK1, are substrates for OGT, suggesting potential O-GlcNAc control points within the pathway. To elucidate the roles of O-GlcNAc in dampening insulin signaling (Vosseller, K., Wells, L., Lane, M. D., and Hart, G. W. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 5313-5318), we focused on the pathway upstream of AKT. Increasing O-GlcNAc in 3T3-L1 adipocytes decreases phosphoinositide 3-kinase (PI3K) interactions with both IRS-1 and IRS-2. Elevated O-GlcNAc also reduces phosphorylation of the PI3K p85 binding motifs (YXXM) of IRS-1 and results in a concomitant reduction in tyrosine phosphorylation of Y(608)XXM in IRS-1, one of the two main PI3K p85 binding motifs. Additionally, insulin signaling stimulates the interaction of OGT with PDK1. We conclude that one of the steps at which O-GlcNAc contributes to insulin resistance is by inhibiting phosphorylation at the Y(608)XXM PI3K p85 binding motif in IRS-1 and possibly at PDK1 as well.
Whelan
Stephen A
SA
Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2185, USA.
Dias
Wagner B
WB
Thiruneelakantapillai
Lakshmanan
L
Lane
M Daniel
MD
Hart
Gerald W
GW
D041721:3T3-L1 Cells; D000117:Acetylglucosamine / Q000235:genetics / Q000378:metabolism*; D017667:Adipocytes / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins / Q000235:genetics / Q000378:metabolism*; D007333:Insulin Resistance; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000117:Acetylglucosamine; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; C526292:IRS1 protein, human; C526297:IRS2 protein, human; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; C000631429:PDK1 protein, human; C000631433:Pdk1 protein, mouse