Retbindin is an Extracellular Riboflavin Binding Protein Found at the Photoreceptor/Retinal Pigment Epithelium Interface [Glycobiology and Extracellular Matrices]

December 25th, 2014 by Kelley, R. A., Al-Ubaidi, M. R., Naash, M. I.

Retbindin is a novel retina-specific protein of unknown function. In this study we have used various approaches to evaluate protein expression, localization, biochemical properties, and function. We find that retbindin is secreted by the rod photoreceptors into the interphotoreceptor matrix where it is maintained via electrostatic forces. Retbindin is predominantly localized at the interface between photoreceptors and retinal pigment epithelium (RPE) microvilli, a region critical for retinal function and homeostasis. Interestingly, while it is associated with photoreceptor outer segments, retbindin's expression is not dependent on their presence. In vitro, retbindin is capable of binding riboflavin; implicating the protein as a metabolite carrier between the retina and the RPE. Altogether, our data show that retbindin is a novel photoreceptor specific protein with a unique localization and function. We hypothesize that retbindin is an excellent candidate for binding retinal flavins and possibly participating in their transport from the extracellular space to the photoreceptors. Further investigations are warranted to determine the exact function of retbindin in retinal homeostasis and disease.
  • Posted in Journal of Biological Chemistry, Publications
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