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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Peng, Jennifer Travis, Gabriel H. Bok, Dean Mata, Nathan L. Radu, Roxana A. Hu, Jane |
| Description | Author Affiliation: Radu RA ( Jules Stein Eye Institute, California, USA.) |
| Abstract | Visual perception begins with the absorption of a photon by an opsin pigment, inducing isomerization of its 11-cis-retinaldehyde chromophore. After a brief period of activation, the resulting all-trans-retinaldehyde dissociates from the opsin apoprotein rendering it insensitive to light. Restoring light sensitivity to apo-opsin requires thermal re-isomerization of all-trans-retinaldehyde to 11-cis-retinaldehyde via an enzyme pathway called the visual cycle in retinal pigment epithelial (RPE) cells. Vertebrates can see over a 10(8)-fold range of background illumination. This implies that the visual cycle can regenerate a visual chromophore over a similarly broad range. However, nothing is known about how the visual cycle is regulated. Here we show that RPE cells, functionally or physically separated from photoreceptors, respond to light by mobilizing all-trans-retinyl esters. These retinyl esters are substrates for the retinoid isomerase and hence critical for regenerating visual chromophore. We show in knock-out mice and by RNA interference in human RPE cells that this mobilization is mediated by a protein called 'RPE-retinal G protein receptor' (RGR) opsin. These data establish that RPE cells are intrinsically sensitive to light. Finally, we show that in the dark, RGR-opsin inhibits lecithin:retinol acyltransferase and all-trans-retinyl ester hydrolase in vitro and that this inhibition is released upon exposure to light. The results of this study suggest that RGR-opsin mediates light-dependent translocation of all-trans-retinyl esters from a storage pool in lipid droplets to an 'isomerase pool' in membranes of the endoplasmic reticulum. This translocation permits insoluble all-trans-retinyl esters to be utilized as substrate for the synthesis of a new visual chromophore. |
| ISSN | 00219258 |
| e-ISSN | 1083351X |
| Journal | Journal of Biological Chemistry |
| Issue Number | 28 |
| Volume Number | 283 |
| Language | English |
| Publisher | American Society for Biochemistry and Molecular Biology (United States) |
| Publisher Date | 2008-07-11 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Epithelial Cells Metabolism Eye Proteins Pigment Epithelium Of Eye Receptors, G-Protein-Coupled Retinaldehyde Rod Opsins Visual Perception Physiology Acyltransferases Genetics Animals Carboxylic Ester Hydrolases Cell Membrane Endoplasmic Reticulum Mice Mice, Knockout RNA Interference Cis-trans-Isomerases Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Biochemistry Molecular Biology |
| Content Type | Text |
| Resource Type | Article |
| Subject | Cell Biology Biochemistry Molecular Biology |
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