Support for a proposed retinoid-processing protein complex in apical retinal pigment epithelium

The interaction of cellular retinaldehyde-binding protein (CRALBP) with ERM (ezrin, radixin, moesin)-binding phosphoprotein 50 (EBP50) in retinal pigment epithelium (RPE) microsomes has led to the hypothesis that a retinoid-processing protein complex exists in apical RPE. Mouse RPE apical processes were isolated on wheat germ agglutinin-coated agarose beads. Proteomic analyses of the isolated apical RPE demonstrated the presence of CRALBP, EBP50, 11-cis-retinol dehydrogenase, cellular retinol-binding protein 1, and interphotoreceptor retinoid-binding protein. The results support the hypothesis that a visual cycle protein complex may serve in the localization and release of 11-cis-retinoid in the apical RPE.