Clathrin-mediated endocytosis of the β-adrenergic receptor is regulated by phosphorylation/dephosphorylation of β-arrestin1

beta-Arrestins serve a dual regulatory role in the life cycle of G protein-coupled receptors such as the ,beta(2)-adrenergic receptor, First, they mediate rapid desensitization by binding to G protein-coupled receptor kinase-phosphorylated receptors, Second, they target the receptors for internalization into endosomal vesicles, wherein receptor dephosphorylation and resensitization occur, Here we report that phosphorylation of a carboxyl terminal serine (Ser-412) in beta-arrestin1 regulates its endocytotic but not its desensitization function, Cytoplasmic beta-arrestin1 is constitutively phosphorylated and is recruited to the plasma membrane by agonist stimulation of the receptors. At the plasma membrane, beta-arrestin1 is rapidly dephosphorylated, a process that is required for its clathrin binding and receptor endocytosis but not for its receptor binding and desensitization. Once internalized, beta-arrestin1 is re-phosphorylated., Thus, as with the classical endocytic adaptor protein complex AP2, beta-arrestin1 functions as a clathrin adaptor in receptor endocytosis which is regulated by dephosphorylation at the plasma membrane.