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Major insulin signals such as stimulation of glucose uptake and DNA synthesis and modification of hexose metabolism are mediated by the tyrosine-phosphorylated insulin receptor substrate-1 (IRS-1; pp 180) in many species of cells. We cloned cDNA encoding a 190-kDa IRS-1-like protein (pp190) in simian COS cells and which is slightly larger than IRS-1 (pp180) of human, rat, and mouse cells. The deduced amino acid sequence of COS pp190 consisted of 1251 amino acids and was 96.4%, 87.9% and 88.7% identical to human, mouse and rat IRS-1. The COS pp190 bound to SH2 (src-homology 2) domains of p85, Grb2/Ash, and SH-PTP2, as did IRS-1. In IRS-1-knockout mice, insulin signals are thought to be mediated by IRS-2 (pp190),which is an alternative signaling molecule and is slightly larger than IRS-1. However, the COS pp190 may be a simian homologue of IRS-1, but not of IRS-2. The results of Southern blotting suggested the possibility that Chinese hamster ovary (CHO) cells have not only the IRS-I gene but also a gene related to the COS pp190.

We generated transgenic mice homozygous for the tyrosine kinase-deficient human insulin receptor (hIRK1030M(+/+)) under control of the insulin receptor promoter. Similar growth patterns and results of glucose tolerance tests were observed among normal, heterozygous, and homozygous mice. Insulin tolerance test indicated no significant difference in the hypoglycemic response to insulin among the three genotypes. However, the serum insulin levels of the homozygous mice before and after glucose loading (201.42 +/- 58.15 pg/ml to 578.57 +/- 49.03 pg/ml) were significantly higher than in the control mice (100.92 +/- 19.55 pg/ml to 356.36 +/- 55.08 pg/ml; p0.01 and p0.01, respectively) and heterozygous mice (74.46 +/- 18.55 pg/ml to 352.33 +/- 52.43 pg/ml; p0.005 and p0.01, respectively). Immunohistological evidence of pancreatic islets showed no significant difference among the three genotypes. Taken together, these results suggest that the tyrosine kinase-deficient insulin receptor causes hyperinsulinemia but not diabetes in these homozygous transgenic mice.