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Krysten Farjo, Gennadiy Moiseyev, Jian-Xing Ma; Targeting the STRA6/RBP4 Binding interaction to Treat Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1702.
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© ARVO (1962-2015); The Authors (2016-present)
Macular degeneration is initiated and perpetuated by the accumulation of toxic Vitamin A derivatives in the retinal pigment epithelium (RPE). Pharmacological inhibition of Vitamin A delivery or metabolism in the RPE can significantly slow and reduce vision loss in animal models of macular degeneration. Serum retinol binding protein (RBP4) transports Vitamin A, and delivers Vitamin A to RPE through binding to its receptor, STRA6. We sought to develop and characterize novel inhibitory peptides that target the STRA6/RBP4 interaction to reduce Vitamin A delivery to RPE.
We synthesized candidate inhibitory peptides based on the protein domains of STRA6 that are implicated in binding to RBP4 (including C43, C194-Q196, Y335-G341, and R461-N462). HEK-293 cells were used to generate a STRA6-stable cell line, which served as the basis for the development of a high throughput STRA6/RBP4 competition binding assay in which alkaline phosphatase-tagged RBP4 (AP-RBP4) is incubated with STRA6-stable cells alone or in combination with increasing concentrations of candidate inhibitory peptides. Quantification of AP activity is proportional to the amount of AP-RBP4 bound to STRA6-stable cells. In addition, we have established a cellular Vitamin A uptake assay to evaluate the efficacy of inhibitory peptides to reduce STRA6-mediated uptake of Vitamin A in STRA6-stable cells.
We have identified four inhibitory peptides that significantly reduce the STRA6/RBP4 binding interaction and/or inhibit STRA6-mediated Vitamin A uptake.
Peptides derived from the STRA6 protein domains implicated in binding to RBP4 have inhibitory activity to significantly reduce STRA6/RBP4 binding and STRA6-mediated Vitamin A uptake in cell culture. Ongoing studies are evaluating the ability of these peptides to inhibit Vitamin A uptake and visual cycle activity in mouse eyecups. These inhibitory peptides could serve as the basis for the development of a novel therapeutic to treat macular degeneration.
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