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AC ProvostCERTO Faculte de Medecine Necker Paris France, MO Pequignot, S Salle, K Sainton, M Abitbol; Gene and Protein Expression of Srb1 (Scavenger receptor Class B, Type 1) a Cell Surface HDL Receptor of CD36 Superfamilly, in the Adult Rat Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4562.
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Purpose: The class B type I scavenger receptor Sr-b1 is a member of the CD36 receptor family. Sr-b1 plays a key antiatherosclerotic role in HDL metabolism: it mediates the selective uptake of lipoprotein cholesterol from peripheral tissues and plasma, and the delivery of cholesteryl esters to the liver and steroidogenic tissues (synthesis of bile and steroids). The CD36 protein family is involved in the recognition and clearance of apoptotic cells by macrophages and rod outer segments (ROS) phagocytosis by retinal pigment epithelial cells (RPE). Our aim was to determine the Sr-b1 gene expression pattern and protein localization in the normal rat eye. Methods: We compared the expression of Sr-b1 mRNA in different control tissues and in retina using semi-quantitative RT-PCR and its cellular localization by in-situ hybridization (with digoxygenine-labeled probes) on paraffin tissue sections. SR-B1 proteins in the normal rat eye have been analyzed by immunohistochemistry using the RED-1 antibody. Results: We demonstrate for the first time by semi-quantitative RT-PCR that Sr-b1 mRNA is highly expressed in RPE and neuroretina. We define more precisely the Sr-b1 mRNA localization by in situ hybridization on ocular tissue sections in different types of cell bodies: choriocapillary endothelial cells, RPE cells, photoreceptors, inner nuclear layer and ganglionnic cell layer. Then we localize the SR-B1 proteins by immunohistochemistry on ocular tissue section : in choriocapillary endothelial cells, RPE cells, rod inner segment (RIS), plexiform layers and ganglionnic cells. Conclusion: The high level of SR-B1 protein in both choroidal cells and RPE cells may reflect a key role of Sr-b1 gene in the hemato-ocular cholesterol transport: through these cells, the SR-B1 receptor might provide the cholesterol to the whole retina and eliminate lipid worsts of metabolism and ROS phagocytosis. This receptor may also provide the cholesterol needed by the synthesis of photoreceptor membrane shedding discs in RIS. Future studies will be focused on the antiatherogenic properties of this gene in the eye and on the Sr-b1 involvement in age-related macular degenerations.
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