Beta Arrestin 1 is a member of a family of proteins that are widely expressed but especially abundant in the central nervous system. Serving as an adaptor or scaffold molecule, beta Arrestin 1 is essential for mitogenic signaling. Beta Arrestin 1 has important roles in the cytoplasm and at the plasma membrane in the desensitization and internalization of G protein coupled receptors (GPCRs) and is increasingly appreciated to play an important role in the endocytosis and signaling of GPCRs. Beta Arrestin 1 in the cytosol is phosphorylated by ERK1 and 2 on serine 412 in a negative feedback mechanism and binds to the phosphorylated receptors at the plasma membrane.