Vision involves the conversion of light into electrochemical signals that are processed by the retina and subsequently sent to and interpreted by the brain. The process of converting light to an electrochemical signal begins when the membrane-bound protein, rhodopsin, absorbs light within the retina. In the active state, rhodopsin activates transducin, a GTP binding protein that promotes the hydrolysis of cGMP by phosphodiesterase (PDE). The decrease of intracellular cGMP concentrations causes the ion channels within the outer segment of the rod or cone to close, thus causing membrane hyperpolarization and, eventually, signal transmission. Rhodopsin's activity is believed to be shut off by its phosphorylation followed by binding of the soluble protein arrestin. Arrestins are cytosolic proteins that are involved in G protein-coupled receptor (GPCR) desensitization. Arrestin binding to activated GPCRs is phosphorylation dependent and, once bound, uncouple the GPCR from the associated heterotrimeric G proteins. There are currently 4 known mammalian isoforms, beta-arrestin1 (arrestin2), beta-arrestin2 (arrestin3), visual arrestin (arrestin1), and cone arrestin. The beta- isoforms are ubiquitously expressed and are known to interact with acetylcholine and adrenergic receptors. Visual and cone arrestins are found to interact directly with transducin.
arrestin 2; arrestin 3; Arrestin beta-1; Arrestin beta-2; arrestin, beta 1; arrestin, beta 2; Beta-arrestin-1; Beta-arrestin-2; beta-arrestin2; Non-visual arrestin-2; Non-visual arrestin-3; S-Arrestin