The Role of Interphotoreceptor Retinoid-Binding Protein on the Translocation of Visual Retinoids and Function of Cone Photoreceptors

• DOI: 10.1523/jneurosci.3882-08.2009
• Publication Date: 2009-02-04T18:33:35Z
• Authors: Minghao Jin; Songhua Li; Steven Nusinowitz; Marcia Lloyd; Jane Hu; Roxana A. Radu; Dean Bok; Gabriel H. Travis
• Keywords: Opsin; Visual phototransduction; RPE65; Retinaldehyde; Transducin

The first event in light perception is absorption of a photon by the retinaldehyde chromophore an opsin pigment rod or cone photoreceptor cell. This induces isomerization chromophore, rendering bleached insensitive to light. Restoration sensitivity requires chemical reisomerization via multistep enzyme pathway, called visual cycle, cells retinal epithelium (RPE). Interphotoreceptor retinoid-binding protein (IRBP) present extracellular space between photoreceptors and RPE. IRBP known bind retinoids. Previous studies on irbp −/− mice suggested that plays insignificant role opsin-pigment regeneration. However, these were uncontrolled for severe mutation rpe65 gene. Rpe65 catalyzes rate-limiting step cycle. Here, we examined phenotype homozygous wild-type (Leu450) We show lack causes delayed transfer newly synthesized from RPE photoreceptors. Removal also retinas after exposure. It was previously shown rods degenerate mice. cones at similar rates. are more affected functionally greater reductions outer segment length than disproportionate function outer-segment appear result mistrafficking opsins due impaired delivery which functions as chaperone but not rhodopsin.