| Autor: |
Sharma Y; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Lo R; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Tomilin VN; Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, USA., Ha K; Department of Physiology, UCSF, San Francisco, California, USA., Deremo H; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Pareek AV; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Dong W; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Liao X; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA., Lebedeva S; Department of Pharmacology, Institute of Pharmacy, I.M. Sechenov First Moscow State Medical University, Moscow, Russia., Charu V; Department of Pathology, Stanford University School of Medicine, Stanford, California, USA., Kambham N; Department of Pathology, Stanford University School of Medicine, Stanford, California, USA., Mutig K; Department of Pharmacology, Institute of Pharmacy, I.M. Sechenov First Moscow State Medical University, Moscow, Russia.; Department of Translational Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany., Pochynyuk O; Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, USA., Bhalla V; Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Stanford, California, USA. |
| Abstrakt: |
Mutations in the CLCNKB gene (1p36), encoding the basolateral chloride channel ClC-Kb, cause type 3 Bartter syndrome. We identified a family with a mixed Bartter/Gitelman phenotype and early-onset kidney failure and by employing a candidate gene approach, identified what we believe is a novel homozygous mutation (CLCNKB c.499G>T [p.Gly167Cys]) in exon 6 of CLCNKB in the index patient. We then validated these results with Sanger and whole-exome sequencing. Compared with wild-type ClC-Kb, the Gly167Cys mutant conducted less current and exhibited impaired complex N-linked glycosylation in vitro. We demonstrated that loss of Gly-167, rather than gain of a mutant Cys, impairs complex glycosylation, but that surface expression remains intact. Moreover, Asn-364 was necessary for channel function and complex glycosylation. Morphologic evaluation of human kidney biopsies revealed typical basolateral localization of mutant Gly167Cys ClC-Kb in cortical distal tubular epithelia. However, we detected attenuated expression of distal sodium transport proteins, changes in abundance of distal tubule segments, and hypokalemia-associated intracellular condensates from the index patient compared with control nephrectomy specimens. The present data establish what we believe are novel regulatory mechanisms of ClC-Kb activity and demonstrate nephron remodeling in humans, caused by mutant ClC-Kb, with implications for renal electrolyte handling, blood pressure control, and kidney disease. |
