Mutations in the CLCN5 gene encoding the 2Cl- /1H+ exchanger ClC-5 are associated with Dent disease 1, an inherited renal disorder characterized by low molecular weight (LMW) proteinuria and hypercalciuria. In the kidney, ClC-5 is mostly localized in proximal tubule cells where it is thought to play a key role in the endocytosis of LMW proteins. Here, we investigated the consequences of eight previously reported pathogenic missense mutations of ClC-5 surrounding the "proton glutamate" that serves as a crucial H+ -binding site for the exchanger. A complete loss of function was observed for a group of mutants that were either retained in the endoplasmic reticulum of HEK293T cells or unstainable at plasma membrane due to proteasomal degradation. In contrast, the currents measured for a second group of mutations in X. laevis oocytes were reduced. Molecular Dynamics simulations performed on a ClC-5 homology model demonstrated that such mutations may alter ClC-5 protonation by interfering with the water pathway. Analysis of clinical data from patients harboring these mutations demonstrated no phenotype/genotype correlation. This study reveals that mutations clustered in a crucial region of ClC-5 have diverse molecular consequences in patients with Dent disease 1, ranging from altered expression to defects in transport. This article is protected by copyright. All rights reserved.