A novel CLCN5 pathogenic mutation supports Dent disease with normal endosomal acidification

作者：Yohan Bignon, Alexi K. Alekov, Nadia Frachon, Olivier Lahuna, Carine Jean-Baptiste Doh-Egueli, Georges Deschênes, Rosa Vargas‐Poussou, Stéphane Lourdel · 发表于：Human Mutation · 年份：2018 · DOI：10.1002/humu.23556 · 被引用次数：25 · 研究领域：Ion channel regulation and function、Erythrocyte Function and Pathophysiology、Cellular transport and secretion

Dent disease is an X-linked recessive renal tubular disorder characterized by low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, nephrocalcinosis, and progressive renal failure. Inactivating mutations of CLCN5, the gene encoding the 2Cl−/H+ exchanger ClC-5, have been reported in patients with Dent disease 1. In vivo studies in mice harboring an artificial mutation in the “gating glutamate” of ClC-5 (c.632A > C, p.Glu211Ala) and mathematical modeling suggest that endosomal chloride concentration could be an important parameter in endocytosis, rather than acidification as earlier hypothesized. Here, we described a novel pathogenic mutation affecting the “gating glutamate” of ClC-5 (c.632A>G, p.Glu211Gly) and investigated its molecular consequences. In HEK293T cells, the p.Glu211Gly ClC-5 mutant displayed unaltered N-glycosylation and normal plasma membrane and early endosomes localizations. In Xenopus laevis oocytes and HEK293T cells, we found that contrasting with wild-type ClC-5, the mutation abolished the outward rectification, the sensitivity to extracellular H+ and converted ClC-5 into a Cl− channel. Investigation of endosomal acidification in HEK293T cells using the pH-sensitive pHluorin2 probe showed that the luminal pH of cells expressing a wild-type or p.Glu211Gly ClC-5 was not significantly different. Our study further confirms that impaired acidification of endosomes is not the only parameter leading to defective endocytosis in Dent disease 1.