CyclosporinA Derivative as Therapeutic Candidate for Alport Syndrome by Inducing Mutant Type IV Collagen Secretion

Background Type IV collagen << 3,4,5 (<< 345(IV)) is an obligate trimer that is secreted to form a collagen network, which is the structural foundation of basement membrane. Mutation in one of the genes (COL4A3, A4, A5) encoding these proteins underlies the progressive genetic nephropathy Alport syndrome (AS) due to deficiency in trimerization and/or secretion of the << 345(IV) trimer. Thus, improving mutant << 345(IV) trimerization and secretion could be a good therapeutic approach for AS. Methods Using the nanoluciferase-based platform that we previously developed to detect << 345(IV) formation and secretion in HEK293T cells, we screened libraries of natural product extracts and compounds to find a candidate compound capable of increasing mutant << 345(IV) secretion. Results The screening of >13,000 extracts and >600 compounds revealed that cyclosporin A (CsA) increased the secretion of mutant << 345(IV)-G1244D. To elucidate the mechanism of the effect of CsA, we evaluated CsA derivatives with different ability to bind to calcineurin (Cn) and cyclophilin (Cyp). Alisporivir (ALV), which binds to Cyp but not to Cn, increased the trimer secretion of mutant << 345(IV). Knockdown studies on Cyps showed that PPIF/cyclophilin D was involved in the trimer secretion-enhancing activity of CsA and ALV. We confirmed that other << 345(IV) mutants are also responsive to CsA and ALV. Conclusions CsA was previously reported to improve proteinuria in patients with AS, but owing to its nephrotoxic effect, CsA is not recommended for treatment in patients with AS. Our data raise the possibility that ALV could be a safer option than CsA. This study provides a novel therapeutic candidate for AS with an innovative mechanism of action and reveals an aspect of the intracellular regulatory mechanism of << 345(IV) that was previously unexplored.

Automated summary

This study provides a novel therapeutic candidate, alisporivir, for Alport syndrome (AS) by enhancing the secretion of mutant 345(IV) and reveals the importance of cyclophilin D in this process. It suggests that alisporivir could be a safer option than cyclosporin A for AS treatment.