Adapter protein that plays a role in regulating cell-surface expression of adrenergic receptors and probably also other G protein-coupled receptors (PubMed:21982743). 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. Detected in visceral fat, subcutaneous fat, brown fat and skeletal muscle, and at lower levels in kidney. Up-regulated by fasting. Transiently up-regulated during the differentiation of pre-adipocytes. Mice are born at the expected Mendelian rate, but there is important perinatal lethality and the majority do not survive till weaning. Mutant mice have considerably less body mass and accumulate less body fat than wild-type, in spite of normal food intake. Heterozygous mice display higher oxygen uptake, increased activity levels and higher energy expenditure than wild-type. In addition, they display increased expression of genes required for thermogenesis, increased activation of signaling cascades downstream of beta-adrenergic receptors, more rapid readjustment of body temperature when exposed to cold and increased heat production. Belongs to the arrestin family.