ap20187 and Insulin-Resistance

Diabetes mellitus derives from either insulin deficiency (type I) or resistance (type II). Homozygous mutations in the insulin receptor (IR) gene cause the rare leprechaunism and Rabson-Mendenhall syndromes, severe forms of hyperinsulinemic insulin resistance for which no therapy is currently available. Systems have been developed that allow protein-protein interactions to be brought under the control of small-molecule dimerizer drugs. As a potential tool to rescue glucose homeostasis at will in both insulin and insulin receptor deficiencies, we developed a recombinant chimeric insulin receptor (LFv2IRE) that can be homodimerized and activated by the small-molecule dimerizer AP20187. In HepG2 cells transduced with adeno-associated viral (AAV) vectors encoding LFv2IRE, AP20187 induces LFv2IRE homodimerization and transphosphorylation minutes after drug administration, resulting in the phosphorylation of a canonical substrate of the insulin receptor tyrosine kinase, IRS-1. AP20187 activation of LFv2IRE is dependent on the dose of drug and the amount of chimeric receptor expressed in AAV-transduced cells. Finally, AP20187-dependent activation of LFv2IRE results in insulin-like effects, such as induction of glycogen synthase activity and cellular proliferation. In vivo LFv2IRE transduction of insulin target tissues followed by AP20187 dosing may represent a therapeutic strategy to be tested in animal models of insulin resistance due to insulin receptor deficiency or of type I diabetes. This system may also represent a useful tool to dissect in vivo the independent contribution of insulin target tissues to hormone action.

Topics: Blotting, Western; Cell Line; Cell Line, Tumor; Cell Proliferation; Dependovirus; Diabetes Mellitus, Type 1; Dimerization; Dose-Response Relationship, Drug; Fibroblasts; Gene Transfer Techniques; Genetic Vectors; Glycogen Synthase; Homozygote; Humans; Immunoprecipitation; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Mutation; Phosphoproteins; Phosphorylation; Protein Structure, Tertiary; Receptor, Insulin; Signal Transduction; Tacrolimus; Time Factors; Tyrosine