Rod-derived Cone Viability Factor 2

Rod-derived Cone Viability Factor (RdCVF) is a truncated thioredoxin secreted by rod photoreceptors that protects cones. Because the secondary loss of cones in retinitis pigmentosa (RP) is the major visual handicap of this untreatable neurodegenerative disease, the administration of RdCVF is thought to be a promising therapy for RP. We show that RdCVF is acting by binding to Basigin-1 (BSG1) at the surface of cones. BSG1 is an alternative splice product of the BSG gene, a transmembrane protein with an extra immunoglobin domain expressed specifically in the retina. BSG1 binds to the glucose transporter GLUT1. RdCVF increases glucose entry into cones. We found that the increase in glucose is used by cones to induce cell survival by stimulating aerobic glycolysis. A disease associated missense mutation of RdCVF results in its inability to bind to BSG1, to stimulate glucose uptake and to prevent secondary cone death of a model of RP.