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M. Garlipp, F. Gonzalez-Fernandez; Light-Dependent Interaction of Interphotoreceptor Retinoid-Binding Protein (IRBP) With Xenopus Cone Outer Segments. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1896.
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Our long-term interest is to understand how IRBP targets the delivery and uptake of 11-cis retinal, all-trans and 11-cis retinol between the cells bordering the interphotoreceptor matrix (IPM). For example, IRBP has significant activity in promoting the outer segment delivery, and release of 11-cis retinal and all-trans retinol respectively. Although much attention has been given to the ease with which IRBP can be removed from the IPM by aqueous extraction, there are hints in the literature that not all of the IRBP is available for such extraction. Here, we ask whether IRBP demonstrates a physiologically relevant interaction with structures in the retina.
Wash resistant IRBP mainly labeled photoreceptor outer segments (OS), predominantly cones. Whereas in unwashed retinas matrix staining was diffuse and intense. Similar results were observed in exogenous IRBP experiments. XIRBP-647 staining was observed in cone OS. Ovalbumin-647 and unconjugated Alexa-647 dye showed minimal fluorescence. Dark adapted retinas in both paradigms showed reduced staining.
IRBP interacts with the cone OS in a light dependent manner. On going experiments are aimed at defining whether the interaction is to the out segment or its matrix sheath.
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