ロドプシンに対するマウスモノクローナル抗体 抗Rhodopsin抗体 | Anti-Rhodopsin antibody

Rhodopsin is the protein in the mammalian retina responsible for the light sensitivity of rod cells, which are responsible for vision in low light levels. Somewhat surprisingly, the rhodopsin protein turned out to be a typical member of the seven transmembrane G protein-coupled receptor (GPCR) superfamily.Whereas other GPCRs initiate signaling on binding a specific ligand, rhodopsin exists with a ligand already bound, specifically the vitamin A related substance retinal.

Retinal can exist in two isomeric forms, 11-cis and 11-trans retinal. In the dark, rhodopsin is associated with 11-cis retinal, but photons cause the 11-cis form to flip to the 11-trans form, and this causes an alteration in the structure of the rhodopsin making it catalytically active. Activated rhodopsin in turn activates the GTP binding protein G protein transducin by favoring the loss of GDP and the addition of GTP. Transducin is a typical member of the family of heterotrimeric G proteins, and consists of an α and a βγ subunit. The α subunit is responsible for the GTP binding and the GTP bound form activates a phosphodiesterase (PDE) enzyme which hydrolyses cyclic GMP. This in turn increases the membrane potential of the rod cell and reduces the rate ofsynaptic signaling. So light stimulation actually results in a reduced rate of photoreceptor synaptic release. This information is transmitted through neurons of the retina to the visual centers of the brain.

Rhodopsin activity is shut off by phosphorylation under the influence of rhodopsin kinase, the activity of whichresults in binding of visual arrestin (a.k.a. arrestin-1 and S-antigen), which prevents rhodopsin from interacting with and activating more transducin molecules. This basic signaling paradigm proved to be a prototype for understanding how other GPCRs function, as proteins similar to transducin, arrestin and rhodopsin kinase are found in these pathways.