The conserved isoleucine-valine-phenylalanine motif couples activation state and endocytic functions of β-arrestins

Beta-arrestins (beta arrs) play a central role in the regulation of G-protein-coupled receptors (GPCRs). Their binding to phosphorylated activated GPCRs induces a conformational transition to an active state resulting in the release of their flexible C-terminal tail. Binding sites for clathrin and the adaptor protein (AP)-2 clathrin adaptor complex are then unmasked, which drive the recruitment of beta arrs-GPCR complexes into clathrin-coated pits (CCPs). A conserved isoleucine-valine-phenylalanine (IVF) motif of the C-terminal tail controls beta arr activation through intramolecular interactions. Here, we provide structural, biochemical and functional evidence in living cells that the IVF motif also controls binding to AP-2. While the F residue is directly involved in AP-2 binding, substitutions of I and V residues, markedly enhanced affinity for AP-2 resulting in active beta arr mutants, which are constitutively targeted to CCPs in the absence of any GPCR activation. Conformational change and endocytic functions of beta arrs thus appear to be coordinated via the complex molecular interactions established by the IVF motif.