b-arrestin 1 (ARRB1, ARB1, ARR1) is a member of the arrestin protein family, which also includes visual arrestin, cone arrestin and b-arrestin 2. b-arrestins bind phosphorylated heptahelical G protein coupled receptors to desensitize and target them to clathrin-coated pits for endocytosis. b-arrestin 1 acts as a cofactor in the b-adrenergic receptor kinase (BARK)-mediated desensitization of b-adrenergic receptors, resulting in specific dampening of cellular responses to stimuli such as hormones, neurotransmitters or sensory signals (1). b-arrestin 1 exists as two alternately spliced transcripts, encoding two isoforms. Isoform A is a longer variant, while isoform B lacks an alternate in-frame exon compared to isoform A, resulting in a shorter protein (1). The functions of the isoforms have not been fully described. b-arrestin 1 is a cytosolic protein, and is widely expressed in cells, particularly in the central nervous system and in peripheral blood leukocytes (2).