Insulin activation of mitogen-activated protein kinases Erk1,2 is amplified via β-adrenergic receptor expression and requires the integrity of the Tyr350 of the receptor

Insulin activates a complex set of intracellular responses, including the activation of mitogen-activated protein kinases Erk1,2. The counterregulatory actions of insulin on:catecholamine action are well known and include phosphorylation of the beta (2)-adrenergic receptor on Tyr(350), Tyr(354), and Tyr(364) in the C-terminal cytoplasmic domain, as well as enhanced sequestration of the beta (2)-adrenergicreceptor. Both beta -adrenerse agonists and insulin provoke sequestration of beta (2)-adrenerac receptors in a synergistic manner. In the current work, crosstalk between insulin action and beta (2)-adrenergic receptors revealed that insulin activation of Erk1,2 was amplified via beta (2)-adrenerse receptors. In Chinese hamster ovary cells, expression of beta (2)-adrenerse receptors enhanced 5-10-fold the activation of Erk1,2 by insulin and prolonged the activation, the greatest enhancement occurring at 5 min post-insulin. The potentiation of insulin signaling on Erk1,2 was proportional to the level of expression of beta (2)-adrenerse receptor. The potentiation of insulin signaling requires the integrity of Tyr350 Of the beta (2)-adrenergic receptor, a residue phosphorylated in response to insulin. beta (2)-adrenergic receptors with a Y350F mutation failed to potentiate insulin activation of Erk1,2. Expression of the C-terminal domain of the beta (2)-adrenerse receptor (pro(323)-Leu(418)) in cells expressing the intact: beta (2)-adrenergic receptor acts as a dominant negative,:blocking the potentiation of insulin activation of Erk1,2 via the beta (2)-adrenergic receptor. Blockade of beta (2)-adrenergic receptor sequestration does not alter the ability of the beta (2)-adrenergic receptor to potentiate insulin action On Erk1,2, We propose a new paradigm in which a G-protein-linked receptor, such as the beta (2)-adrenergic receptor, itself acts as a receptor-based scaffold via its binding site for Src homology 2 domains, facilitating signaling of the mitogen-activated protein kinase pathway by insulin.