Disease relevance of Clcn5

• Dent's disease patients with mutant ClC-5 channels and ClC-5 knockout (KO) mice both have low molecular mass proteinuria [1].
• Instead, the goiter associated with ClC-5 KO results from impaired rate of apical iodide efflux by down-regulation of pendrin expression [2].
• High citrate diet delays progression of renal insufficiency in the ClC-5 knockout mouse model of Dent's disease [3].
• ClC-5 knockout mice fed a zero citrate diet had significantly increased tubular atrophy, interstitial fibrosis, cystic changes, and nephrocalcinosis compared to ClC-5 knockout mice fed a high citrate diet [3].
• These results improve our understanding of Dent's disease, taken as a paradigm for renal Fanconi syndrome and nephrolithiasis, and demonstrate multiple roles for ClC-5 in the kidney [4].

High impact information on Clcn5

• ClC-5 Cl- -channel disruption impairs endocytosis in a mouse model for Dent's disease [5].
• It is caused by mutations in ClC-5, a renal chloride channel that is expressed in endosomes of the proximal tubule [5].
• Thus, impaired protein endocytosis caused by invalidation of ClC-5 primarily reflects a trafficking defect of megalin and cubilin in PTC [6].
• The ClC-5 chloride channel resides mainly in vesicles of the endocytotic pathway and contributes to their acidification [7].
• Possibly by recycling, a small fraction of ClC-5 also reaches the plasma membrane [7].

Chemical compound and disease context of Clcn5

• The loss of the chloride channel, ClC-5, delays apical iodide efflux and induces a euthyroid goiter in the mouse thyroid gland [2].
• ClC-5 chloride channel deficiency causes proteinuria, hypercalciuria, and nephrolithiasis (Dent's disease) [8].

Biological context of Clcn5

• An enhancer element that confers a 10- to 20-fold increase in the promoter activity of the mouse Clcn5 gene was found within the first intron [9].
• Nine-month-old ClC-5 knockout mice on a zero citrate diet had significantly decreased glomerular filtration rate (GFR), whereas 9-month-old ClC-5 knockout mice on a high citrate diet had normal renal function [3].
• Kidney-specific upregulation of vitamin D3 target genes in ClC-5 KO mice [10].

Anatomical context of Clcn5

• We found that ClC-5 is highly expressed in wild-type mouse thyroid ( approximately 40% of mRNA kidney level) [2].
• In Percoll gradients, ClC-5 overlapped with plasma membrane and early endosome markers, but best codistributed with the late endosomal marker, Rab7 [2].
• Impaired endosomal acidification in proximal tubule caused by reduced chloride conductance is a proposed mechanism; however, functional analysis of ClC-5 in oocytes predicts low ClC-5 chloride conductance in endosomes because of their acid interior pH and positive potential [8].
• ClC-5 is expressed in part in cells lining the proximal tubule (PT) of the kidney, where it colocalizes with albumin-containing endocytic vesicles belonging to the receptor-mediated endocytic pathway that ensures efficient reabsorption of ultrafiltrated LMW proteins [4].
• These observations allowed us to conclude that defective protein endocytosis linked to ClC-5 inactivation is due at least in part to a major and selective loss of megalin and cubilin at the brush border, reflecting a trafficking defect in renal PT cells [4].

Associations of Clcn5 with chemical compounds

• METHODS: We studied the effect of zero and high citrate diet on renal function of ClC-5 knockout mice and wild-type mice [3].
• When comparing ClC-5 KO with wild-type mice, thyroid 125I uptake after 1 h was doubled, incorporation into Tg was decreased by approximately 2-fold, so that trichloroacetic acid-soluble 125I increased approximately 4-fold [2].
• Our results provide direct evidence for ClC-5 involvement in acidification of early endosomes in proximal tubule by a chloride shunt mechanism [8].
• The defective endocytosis in ClC-5 KO mice entails an increased luminal concentration of PTH, subsequent stimulation of apical PTH receptors which causes an increased endocytosis of the phosphate transporter NaPi and phosphaturia [11].
• In spite of reduced serum levels of 1,25(OH)(2)-vitamin D(3) in ClC-5 KO mice, 1,25(OH)(2)-vitamin D(3) is increased in later nephron segments as a consequence of impaired proximal tubular endocytosis [10].

Physical interactions of Clcn5

• Here, endosomal pH and chloride concentration were measured in proximal tubule cell cultures from wildtype vs. ClC-5 deficient mice using fluorescent sensors coupled to transferrin (early/recycling endosomes) or alpha(2)-macroglobulin (late endosomes) [8].

Regulatory relationships of Clcn5

• ClC-5 is expressed in apical endosomes of proximal tubular cells where it co-localizes with endocytosed proteins and the proton ATPase [11].

Other interactions of Clcn5

• Transforming growth factor-beta1 (TGF-beta1) was significantly increased in 9-month-old ClC-5 knockout mice on zero citrate diet compared to 9-month-old wild-type mice on the same diet [3].
• Initial pH in transferrin-labeled endosomes was approximately 7.2, decreasing at 15 min to 6.0 vs. 6.5 in wildtype vs. ClC-5 deficient cells, respectively; corresponding endosomal chloride concentration increased from approximately 16 mM to 47 vs. 36 mM [8].
• Thus, the endocytosis of ClC-5, which itself is crucial for the endocytosis of other proteins, depends on the interaction of a carboxyl-terminal internalization signal with ubiquitin-protein ligases containing WW domains [7].
• Stimulating endocytosis by expressing rab5 or its GTPase-deficient Q79L mutant decreased WT ClC-5 currents but did not affect channels with mutated motifs [7].
• The reduction in proximal tubular endocytosis resulting from a lack of ClC-5 raises the luminal concentration of filtered proteins and peptides like parathyroid hormone (PTH) [10].

Analytical, diagnostic and therapeutic context of Clcn5

• By Western blotting, ClC-5 was found in thyroid tissue extracts of WT, but not of ClC-5 KO mice [12].
• The ClC-5 chloride channel knock-out mouse - an animal model for Dent's disease [11].
• Expression profiling, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), and hormone measurements were used to investigate whether the disruption of ClC-5 affects other signalling pathways [10].
• 3. Slow whole-cell recordings, using nystatin-perforated patches from transfected CHO-K1 cells, also produced voltage-dependent Cl(-) currents consistent with ClC-5 expression [13].

References