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 β₂-adrenergic receptor on Tyr³⁵⁰, Tyr³⁵⁴, and Tyr³⁶⁴ in the C-terminal cytoplasmic domain, as well as enhanced sequestration of the β₂-adrenergic receptor. Both β-adrenergic agonists and insulin provoke sequestration of β₂-adrenergic receptors in a synergistic manner. In the current work, cross-talk between insulin action and β₂-adrenergic receptors revealed that insulin activation of Erk1,2 was amplified via β₂-adrenergic receptors. In Chinese hamster ovary cells, expression of β₂-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 β₂-adrenergic receptor. The potentiation of insulin signaling requires the integrity of Tyr³⁵⁰ of the β₂-adrenergic receptor, a residue phosphorylated in response to insulin, β₂-adrenergic receptors with a Y350F mutation failed to potentiate insulin activation of Erk1,2. Expression of the C-terminal domain of the β₂-adrenergic receptor (Pro³²³-Leu⁴¹⁸) in cells expressing the intact β₂-adrenergic receptor acts as a dominant negative, blocking the potentiation of insulin activation of Erk1,2 via the β₂-adrenergic receptor. Blockade of β₂-adrenergic receptor sequestration does not alter the ability of the β₂-adrenergic receptor to potentiate insulin action on Erk1,2. We propose a new paradigm in which a G-protein-linked receptor, such as the β₂-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.