This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Esposito, D. L. Articles by Cama, A. Search for Related Content PubMed PubMed Citation Articles by Esposito, D. L. Articles by Cama, A.

A Novel T608R Missense Mutation in Insulin Receptor Substrate-1 Identified in a Subject with Type 2 Diabetes Impairs Metabolic Insulin Signaling

Department of Oncology and Neurosciences, Section of Molecular Pathology, University Gabriele D’Annunzio, 66013 Chieti, Italy; and Diabetes Unit, Laboratory of Clinical Investigation, National Center for Complementary and Alternative Medicine, National Institutes of Health (Y.L., M.J.Q.), Bethesda, Maryland 20892

Address all correspondence and requests for reprints to: Michael J. Quon, M.D., Ph.D., Diabetes Unit, Laboratory of Clinical Investigation, National Center for Complementary and Alternative Medicine, National Institutes of Health, Building 10, Room 8C-218, 10 Center Drive, MSC 1755, Bethesda, Maryland 20892-1755. E-mail: quonm{at}nih.gov.

Abstract

Naturally occurring mutations in insulin receptor substrate-1 (IRS-1) have previously been implicated in impaired insulin action. We now report a novel mutation in IRS-1 with substitution of Arg for Thr⁶⁰⁸ that was identified in a patient with type 2 diabetes mellitus. We detected the T608R mutation in 1 of 136 chromosomes from diabetic patients and in 0 of 120 chromosomes from nondiabetic controls, suggesting that this is a rare IRS-1 variant. Conservation of Thr⁶⁰⁸ in human, monkey, rat, mouse, and chicken IRS-1 sequences is consistent with a crucial function for this residue. Moreover, Thr⁶⁰⁸ is located near the YMXM motif containing Tyr⁶¹² that is important for binding and activation of phosphoinositol 3-kinase (PI 3-kinase). To investigate whether the T608R mutation impairs insulin signaling, we transiently transfected NIH-3T3^IR cells with hemagglutinin-tagged wild-type or T608R mutant IRS-1 constructs. Recombinant IRS-1 immunoprecipitated from transfected cells treated with or without insulin was subjected to immunoblotting for the p85 regulatory subunit of PI 3-kinase as well as a PI 3-kinase assay. As expected, in control cells transfected with wild-type IRS-1, insulin stimulation caused an increase in p85 coimmunoprecipitated with IRS-1 as well as a 10-fold increase in IRS-1-associated PI 3-kinase activity. Interestingly, when cells transfected with IRS1-T608R were stimulated with insulin, both the amount of p85 coimmunoprecipitated with IRS1-T608R as well as the associated PI 3-kinase activity were approximately 50% less than those observed with wild-type IRS-1. Moreover, in rat adipose cells, overexpression of IRS1-T608R resulted in significantly less translocation of GLUT4 to the cell surface than comparable overexpression of wild-type IRS-1. We conclude that a naturally occurring substitution of Arg for Thr⁶⁰⁸ in IRS-1 is a rare human mutation that may contribute to insulin resistance by impairing metabolic signaling through PI 3-kinase-dependent pathways.

Footnotes

This work was supported by Telethon-Italy Grant E.0606 (to D.L.E.) and by a grant from the Italian Ministry of Instruction, University and Research to the Center of Excellence on Aging of the University of Chieti.

Abbreviations: HA, Hemagglutinin; IRS-1, insulin receptor substrate-1; PI 3-kinase, phosphoinositol 3-kinase; SSCP, single-strand conformational polymorphism; TLC, thin layer chromatography; WT, wild type.

This article has been cited by other articles:

				A. Danielsson, A. Ost, F. H. Nystrom, and P. Stralfors Attenuation of Insulin-stimulated Insulin Receptor Substrate-1 Serine 307 Phosphorylation in Insulin Resistance of Type 2 Diabetes J. Biol. Chem., October 14, 2005; 280(41): 34389 - 34392. [Abstract] [Full Text] [PDF]

				A. Sharma, S. Chavali, A. Mahajan, R. Tabassum, V. Banerjee, N. Tandon, and D. Bharadwaj Genetic Association, Post-translational Modification, and Protein-Protein Interactions in Type 2 Diabetes Mellitus Mol. Cell. Proteomics, August 1, 2005; 4(8): 1029 - 1037. [Abstract] [Full Text] [PDF]

				A. J. McGettrick, E. P. Feener, and C. R. Kahn Human Insulin Receptor Substrate-1 (IRS-1) Polymorphism G972R Causes IRS-1 to Associate with the Insulin Receptor and Inhibit Receptor Autophosphorylation J. Biol. Chem., February 25, 2005; 280(8): 6441 - 6446. [Abstract] [Full Text] [PDF]

				M. Korc Diabetes Mellitus in the Era of Proteomics Mol. Cell. Proteomics, June 1, 2003; 2(6): 399 - 404. [Full Text] [PDF]