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)-adrenergic receptor. Both beta-adrenergic agonists and insulin provoke sequestration of beta(2)-adrenergic receptors in a synergistic manner. In the current work, cross-talk between insulin action and beta(2)-adrenergic receptors revealed that insulin activation of Erk1,2 was amplified via beta(2)-adrenergic receptors. In Chinese hamster ovary cells, expression of beta(2)-adrenergic 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)-adrenergic receptor. The potentiation of insulin signaling requires the integrity of Tyr(350) 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)-adrenergic 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.