Effect of insulin levels on the phosphorylation of specific amino acid residues in IRS-1: Implications for burn-induced insulin resistance

• Published in: International journal of molecular medicine Vol. 24; no. 4; pp. 531 - 538
• Main Authors: Lu, Xiao-Ming, Hamrahi, Victoria, Tompkins, Ronald, Fischman, Alan
• Format: Journal Article
• Language: English
• Published: Greece D.A. Spandidos 01-10-2009
• Subjects: Animals; Antibodies, Monoclonal; Burns - physiopathology; Cell Line; Electrophoresis, Polyacrylamide Gel; Humans; Immunoprecipitation; Insulin - pharmacology; Insulin Receptor Substrate Proteins - genetics; Insulin Receptor Substrate Proteins - metabolism; Insulin Resistance - physiology; Mice; Phosphorylation - drug effects; Tandem Mass Spectrometry
• ISSN: 1107-3756; 1791-244X
• DOI: 10.3892/ijmm_00000262

Alterations in the phosphorylation and/or degradation of insulin receptor
substrate-1 (IRS-1) produced by burn injury may be responsible, at least in part,
for burn-induced insulin resistance. In particular, following burn injury, reductions
in glucose uptake by skeletal muscle may be secondary to altered abundance and/or
phosphorylation of IRS-1. In this study, we performed in vitro experiments with
293 cells transfected with IRS-1. These studies demonstrated that there is a dramatic
change in the phosphorylation pattern of Tyr, Ser and Thr residues in IRS-1 as
a function of insulin levels. Specifically, Ser and Thr residues in the C-terminal
region were phosphorylated only at high insulin levels. SILAC (stable isotope
labeling with amino acids in cell culture) followed by sequencing of C-terminal
IRS-1 fragments by tandem mass spectrometry demonstrated that there is significant
protein cleavage at these sites. These findings suggest that one of the biological
roles of the C-terminal region of IRS-1 may be negative modulation of the finely
coordinated insulin signaling system. Clearly, this could represent an important
factor in insulin resistance, and identification of kinase inhibitors that are
responsible for the phosphorylation may foster new lines of research for the development
of drugs for treating insulin resistance.