Insulin receptor-deficient cells as a new tool for dissecting complex interplay in insulin and insulin-like growth factors.

Cell systems derived from knockout mice for the insulin receptor (IR) or the IGF-1 receptor (IGF-1R) represent unique tools for dissecting complex interplay in the actions of insulin and insulin-like growth factors through their cognate versus non-cognate receptor. In this study, we used a fibroblast cell line derived from IR-deficient mice to investigate metabolic and mitogenic effects of IGF-1 and insulin. IGF-1 was able to stimulate glucose uptake, glucose incorporation into glycogen and thymidine incorporation in such cells. Phosphatidylinositol 3-kinase and mitogen-activated protein kinase, two enzymes of major metabolic-mitogenic signaling pathways, were activated upon stimulating these cells with IGF-1. All these effects were also achieved when IR-deficient cells were stimulated with insulin. Thus, IGF-1R can represent an alternative receptor through which insulin might exert some of its effects.