Human Insulin Receptors Expressed in Insulin-Insensitive Mouse Fibroblasts Couple with Extant Cellular Effector Systems to Confer Insulin Sensitivity and Responsiveness*

Abstract

When cDNA for human kidney insulin receptors was used to transfect NIH3T3 mouse fibroblast cells with few or no endogenous insulin receptors, a resultant cell line, 3T3/HIR, expressed more than 6 million receptors/cell. Results of the present study demonstrated that these human receptors in murine cells mediated a diverse group of responses, including insulin binding and internalization as well as insulin-stimulated tyrosine phosphorylation of the receptor and a putative cellular substrate pp185. In addition, the cells were stimulated by insulin in various acute and long term metabolic processes, including glucose transport, glycogen formation, amino acid uptake, and thymidine uptake and incorporation into DNA. There were weak or no responses to insulin in control fibroblasts transfected only with the pSV2Neo plasmid containing a bacterial gene for neomycin resistance (3T3/NEO cells). These findings indicated that transfection of insulin receptor cDNA conferred insulin sensitivity to the target cells in a broad range of cellular responses and further demonstrated that effector molecules for mediating such responses were present in cells that normally lacked sensitivity to this hormone. Expressed receptors readily coupled with the effector systems to become fully functional.