Defective receptors for platelet-derived growth factor AA in human fibroblasts with mutant insulin receptors

Leprechaunism is an inherited disorder characterized by growth restriction and severe insulin resistance and caused by mutations in the insulin receptor gene. Cells from these patients have defective insulin binding. Fibroblasts from some patients have concomitant defects in other tyrosine kinase receptors, such as those for Insulin-like Growth Factor I (IGF-I) and Epidermal Growth Factor (EGF). In this report, binding of insulin, IGF-I, EGF, and Platelet derived growth factor (PDGF) AA and PDGF-BB is compared among fibroblasts of patients with defined mutations in their insulin receptor gene. Fibroblasts from patient Atl-1, homozygous for a R86P substitution in the insulin receptor, had reduced binding of Platelet-Derived Growth Factor AA (PDGF-AA), a specific ligand for type alpha PDGF receptors. The reduction in PDGF binding impaired the ability of this growth factor to stimulate DNA synthesis.