The Arrestin family consists of four members: Arrestin 1 (visual Arrestin), Arrestin 2 (b-Arrestin 1), Arrestin 3 (b-Arrestin 2), and Arrestin 4 (cone Arrestin). While visual and cone Arrestins are found almost exclusively in the retina, b-Arrestins 1 and 2 are ubiquitously expressed, and were initially described as negative regulators of G protein-coupled receptor (GPCR) signaling. More recently, b-Arrestins have been determined to serve as scaffolds for various signaling pathways, including the MAPK cascades activating ERK2, p38a, and JNK3. These b-Arrestin scaffolds tie together the appropriate kinases in series, forming a discreet signaling module that localizes components to specific subcellular environments and facilitates greater kinase activation.