A novel small molecule chaperone of rod opsin and its potential therapy for retinal degeneration

Yuanyuan Chen,Krzysztof Palczewski,Hossein Heidari-Torkabadi,Jianye Zhang,William E Harte,Hui Jin,Songqi Gao,Xiaoyu Li,Yu Chen,Xujie Liu,Gregory P Tochtrop,Phoebe L Stewart,Sahil Gulati,Marcin Golczak,Hong Tang,William Seibel,Yong Han,Beata Jastrzebska

doi:10.1038/s41467-018-04261-1

Abstract

Rhodopsin homeostasis is tightly coupled to rod photoreceptor cell survival and vision. Mutations resulting in the misfolding of rhodopsin can lead to autosomal dominant retinitis pigmentosa (adRP), a progressive retinal degeneration that currently is untreatable. Using a cell-based high-throughput screen (HTS) to identify small molecules that can stabilize the P23H-opsin mutant, which causes most cases of adRP, we identified a novel pharmacological chaperone of rod photoreceptor opsin, YC-001. As a non-retinoid molecule, YC-001 demonstrates micromolar potency and efficacy greater than 9-cis-retinal with lower cytotoxicity. YC-001 binds to bovine rod opsin with an EC50 similar to 9-cis-retinal. The chaperone activity of YC-001 is evidenced by its ability to rescue the transport of multiple rod opsin mutants in mammalian cells. YC-001 is also an inverse agonist that non-competitively antagonizes rod opsin signaling. Significantly, a single dose of YC-001 protects Abca4−/−Rdh8−/− mice from bright light-induced retinal degeneration, suggesting its broad therapeutic potential.

Highlights

Rhodopsin homeostasis is tightly coupled to rod photoreceptor cell survival and vision
Using a cell-based β-Gal fragment complementation assay, a high-throughput screen (HTS) was carried out to identify small molecules that promote the transport of the unstable P23H-mutant opsin protein from the endoplasmic reticulum (ER) to the plasma membrane (Fig. 1)[18,31]
Any reduction in the biosynthesis of rhodopsin leads to shortened ROS49, clearly indicating that rhodopsin homeostasis is closely coupled with rod outer segment (ROS) morphology

Summary

Introduction

Rhodopsin homeostasis is tightly coupled to rod photoreceptor cell survival and vision. Mutations destabilizing RPE65 (retinoid isomerase), ATP-binding cassette subfamily A member 4 (ABCA4), or rhodopsin (rod visual pigment) are associated with inherited retinal degenerations including Leber congenital amaurosis[2,3], Stargardt disease[4,5], or adRP6,7, respectively Owing to its abundance and essential physiological function, a pharmacological chaperone and modulator of rod opsin could slow the visual cycle for treatment of retinal degenerations related to all-trans-retinal toxicity, such as Stargardt disease[27,28,29], and adRP resulting from rhodopsin folding defects[30]. Compared to other GPCRs, little is known about small-molecule non-retinoid modulators of rod opsin other than 11-cis-retinal or its analogs, because photoreceptor-specific signaling pathways are difficult to reproduce in mammalian cell cultures for small-molecule screening

Methods

Results

Conclusion