Feedback regulation of β-arrestin1 function by extracellular signal- regulated kinases

Abstract

The functions of β-arrestin1 to facilitate clathrin-mediated endocytosis of the β2-adrenergic receptor and to promote agonist-induced activation of extracellular signal-regulated kinases (ERK) are regulated by its phosphorylation/dephosphorylation at Ser-412. Cytoplasmic β-arrestin1 is almost stoichiometrically phosphorylated at Ser-412. Dephosphorylation of β- arrestin1 at the plasma membrane is required for targeting a signaling complex that includes the agonist-occupied receptors to the clathrin-coated pits. Here we demonstrate that β-arrestin1 phosphorylation and function are modulated by an ERK-dependent negative feedback mechanism. ERK1 and ERK2 phosphorylate β-arrestin1 at Ser-412 in vitro. Inhibition of ERK activity by a dominant-negative MEK1 mutant significantly attenuates β-arrestin1 phosphorylation, thereby increasing the concentration of dephosphorylated β- arrestin1. Under such conditions, β-arrestin1-mediated β2-adrenergic receptor internalization is enhanced as is its ability to bind clathrin. In contrast, if ERK-mediated phosphorylation is increased by transfection of a constitutively active MEK1 mutant, receptor internalization is inhibited. Our results suggest that dephosphorylated β-arrestin1 mediates endocytosis- dependent ERK activation. Following activation, ERKs phosphorylate β- arrestin1, thereby exerting an inhibitory feedback control of its function.