Abstract
Trafficking deficiency caused by missense mutations is a well-known phenomenon occurring for mutant, misfolded proteins. Typically, the misfolded protein is retained by the protein quality control system and degraded by the endoplasmic reticulum-associated protein degradation pathway and thus does not reach its destination although residual function of the protein may be preserved. Chemical and pharmacological chaperones can improve the targeting of trafficking-deficient proteins and thus may be promising candidates for therapeutic applications. Here, we report the application of a cellular bioassay based on the bioluminescent calcium reporter aequorin to quantify surface expression of mutant CNGA3 channels associated with the autosomal-recessively inherited retinal disease achromatopsia. A screening of 77 compounds enabled the identification of effective chemical and pharmacological chaperones resulting in a 1.5 to 4.8 fold increase of surface expression of mutant CNGA3. We confirmed that the rescue of the defective trafficking is not limited to a single mutation in CNGA3 using selected compounds. Active compounds and our structure-activity correlated data for the dihydropyridine compound class may provide valuable information for developing a treatment of the trafficking defect in achromatopsia.
Significance Statement We describe a novel luminescence-based assay to detect the surface expression of mutant, trafficking deficient CNGA3 channels based on the calcium sensitive photoprotein aequorin. Using this assay for a compound screening, we identified novel chemical and pharmacological chaperones restoring the surface localization of mutant trafficking-deficient CNGA3 channels. The results from our work may serve as starting point for the development of potent compounds rescuing trafficking deficiencies in the autosomal-recessively inherited retinal disease achromatopsia.
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