Adapter protein that plays a role in regulating cell-surface expression of adrenergic receptors and probably also other G protein-coupled receptors. Plays a role in NEDD4-mediated ubiquitination and endocytosis af activated ADRB2 and subsequent ADRB2 degradation. May recruit NEDD4 to ADRB2. Alternatively, may function as adapter protein that does not play a major role in recruiting NEDD4 to ADRB2, but rather plays a role in a targeting ADRB2 to endosomes. Interacts (via PPxY motifs) with NEDD4 (via WW domains). Interacts with ADRB2. Interacts with ADRB3. Interacts with HGS (via PPxY motifs). Does not bind TXN (thioredoxin). Interacts with ITCH. Associated with plasma membrane, as well as with endosomes and lysosomes during endocytosis. Belongs to the arrestin family.