Evaluation of common variants in MG53 and the risk of type 2 diabetes and insulin resistance in Han Chinese
We have examined the role of autophosphorylation in insulin signal transmission by oligonucleotide directed mutagenesis of seven potential tyrosine autophosphorylation sites in the human insulin receptor. Chinese hamster ovary cells transfected with these receptors were analyzed for insulin stimulated 2-deoxyglucose uptake, thymidine incorporation, endogenous substrate phosphorylation, and in vitro kinase activity. We found that phosphorylation on tyrosine residues 953, 1316, and 1322 were not necessary for receptor-mediated signal transduction. Mutation of tyrosine 960 reduced but did not abolish the signaling capabilities of the receptor. Finally, the simultaneous mutation of tyrosine residues 1146, 1150, and 1151 (the numbering system is that of Ullrich et al. (Ullrich, A., Bell, J. R., Chen, E. Y., Herrera, R., Petruzzelli, L. M., Dull, T. J., Gray, A., Coussens, L., Liao, Y. C., Tsubokawa, M., Mason, A., Seeburg, P.H., Grunfeld, C., Rosen, O. M., and Ramachandran, J. (1985) Nature 313, 756-761) resulted in a biologically inactive receptor, suggesting that the insulin receptor can be inactivated by removal of key autophosphorylation sites.