A photic visual cycle of rhodopsin regeneration is dependent on Rgr.
During visual excitation, rhodopsin undergoes photoactivation and bleaches to opsin and all-trans-retinal. To regenerate rhodopsin and maintain normal visual sensitivity, the all-trans isomer must be metabolized and reisomerized to produce the chromophore 11-cis-retinal in biochemical steps that constitute the visual cycle and involve the retinal pigment epithelium (RPE; refs. 3-8). A key step in the visual cycle is isomerization of an all-trans retinoid to 11-cis-retinol in the RPE (refs. 9-11). It could be that the retinochrome-like opsins, peropsin, or the retinal G protein-coupled receptor (RGR) opsin12-16 are isomerases in the RPE. In contrast to visual pigments, RGR is bound predominantly to endogenous all-trans-retinal, and irradiation of RGR in vitro results in stereospecific conversion of the bound all-trans isomer to 11-cis-retinal. Here we show that RGR is involved in the formation of 11-cis-retinal in mice and functions in a light-dependent pathway of the rod visual cycle. Mutations in the human gene encoding RGR are associated with retinitis pigmentosa.
Chen
P
P
Department of Ophthalmology, University of Southern California, Los Angeles, California 90033 USA.
Hao
W
W
Rife
L
L
Wang
X P
XP
Shen
D
D
Chen
J
J
Ogden
T
T
Van Boemel
G B
GB
Wu
L
L
Yang
M
M
Fong
H K
HK
D000818:Animals; D003624:Darkness; D004307:Dose-Response Relationship, Radiation; D004596:Electroretinography; D005123:Eye / Q000378:metabolism* / Q000528:radiation effects; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D051379:Mice; D008817:Mice, Mutant Strains; D008956:Models, Chemical; D010775:Photic Stimulation; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000528:radiation effects; D012172:Retinaldehyde / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism* / Q000528:radiation effects
D005136:Eye Proteins; C089754:G protein-coupled receptor RGR; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D012243:Rhodopsin; D012172:Retinaldehyde