Interaction between heterologous receptor tyrosine kinases

Abstract
To determine whether heterologous receptor tyrosine kinases interact with each other we have investigated the ability of insulin receptors to transphosphorylate and transactivate IGF‐I receptors. Using partially purified receptors we show that hormone‐stimulated insulin receptors induced a 40% increase in IGF‐I receptor phosphorylation. Remarkably, this transphosphorylation of IGF‐I receptors by insulin receptors resulted in a 2.5‐fold augmentation of the IGF‐I receptor tyrosine kinase activity for substrates. Our findings demonstrate that transphosphorylation with transactivation can occur between insulin and IGF‐I receptors. We would like to propose that such a phenomenon participates in the insulin‐induced pleiotropic program by mediating the growth promoting effects of the hormone.