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A novel T608R missense mutation in insulin receptor substrate-1 identified in a subject with type 2 diabetes impairs metabolic insulin signaling
- Source :
- The Journal of clinical endocrinology and metabolism. 88(4)
- Publication Year :
- 2003
-
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-3T3IR 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.
- Subjects :
- Male
medicine.medical_specialty
Monosaccharide Transport Proteins
Endocrinology, Diabetes and Metabolism
medicine.medical_treatment
Clinical Biochemistry
Mutant
Mutation, Missense
Muscle Proteins
Type 2 diabetes
Transfection
Biochemistry
Mice
Phosphatidylinositol 3-Kinases
Endocrinology
Internal medicine
Insulin receptor substrate
medicine
Adipocytes
Missense mutation
Animals
Humans
Insulin
Amino Acid Sequence
Immunosorbent Techniques
Polymorphism, Single-Stranded Conformational
Glucose Transporter Type 4
biology
Biochemistry (medical)
Type 2 Diabetes Mellitus
3T3 Cells
Middle Aged
medicine.disease
Phosphoproteins
IRS1
Rats
Insulin receptor
Diabetes Mellitus, Type 2
biology.protein
Insulin Receptor Substrate Proteins
Insulin Resistance
Signal Transduction
Subjects
Details
- ISSN :
- 0021972X
- Volume :
- 88
- Issue :
- 4
- Database :
- OpenAIRE
- Journal :
- The Journal of clinical endocrinology and metabolism
- Accession number :
- edsair.doi.dedup.....1f4c37d10ec49248308263cfbd8458d3