Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020438 (hypercalciuria)
 2,502 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calcium-sensing receptor (CaSR) is a plasma membrane protein that regulates tubular reabsorption of Ca. To establish its role in idiopathic hypercalciuria, the association of urinary Ca excretion with the polymorphisms of CASR gene has been studied in healthy subjects and in hypercalciuric and normocalciuric Ca stone formers. CASR exon 7 single nucleotide polymorphisms (SNP), G/T at codon 986, G/A at codon 990, and C/G at codon 1011, were evaluated by PCR amplification and direct sequencing in 97 normocalciuric stone formers, 134 hypercalciuric stone formers, and 101 normocalciuric healthy controls. Four haplotypes were defined on the basis of CASR gene SNP: haplotype 1 was characterized by the most frequent sequence; haplotypes 2, 3, or 4 by the presence of a single polymorphic variant at codon 986, 990, or 1011, respectively. The relative risk of hypercalciuria was calculated with multinomial logistic regression and was significantly increased only in individuals carrying haplotype 3 (Odds ratio, 13.0 [95% confidence interval, 1.7 to 99.4]). Accordingly, Ca excretion was higher in subjects bearing haplotype 3, whereas those bearing haplotype 2 showed a slight increase of plasma Ca concentration. Multiple regression analysis showed that haplotype 3 explained 4.1% of the total variance of Ca excretion and 12.6% of the variance explained by the variables considered in the study. In conclusion, CASR gene could be a component of the complex genetic background regulating Ca excretion. Arg990Gly polymorphism could facilitate activation of CaSR and increase Ca excretion and susceptibility to idiopathic hypercalciuria.
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PMID:Influence of calcium-sensing receptor gene on urinary calcium excretion in stone-forming patients. 1223 40

Tight junction (TJ) properties are determined by membrane protein complexes of neighboring cells that form both a barrier and a selective pathway for paracellular substrate transport. Our previous work supports the view that paracellular permeability changes in the thick ascending limb (TAL) may underlie the mechanism for familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), a rare autosomal recessive disease linked to mutations in claudin-16 (CLDN16) and claudin-19 (CLDN19). CLDN16 knockdown (KD) mice are lacking CLDN16 expression by transgenic RNA interference. We observed that the transport defect for Mg(2+) and Ca(2+) in this animal model is caused by a loss of paracellular cation selectivity. The permeability ratio for Na(+) over Cl(-) in KD mice was lower by a factor of two without a change in paracellular conductance, compared to wild type (WT). This resulted in a collapse of the transepithelial voltage, which is the driving force for Mg(2+) and Ca(2+) absorption in TAL. Since CLDN16 KD mice revealed lower blood pressure and an increased aldosterone plasma concentration, we hypothesize that the reduction in paracellular selectivity could allow backflow of Na(+) and Cl(-) into the lumen of the TAL, thus enhancing the distal NaCl load and challenging the organism with a latent NaCl loss.
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PMID:Insights into driving forces and paracellular permeability from claudin-16 knockdown mouse. 1953

Receptor-mediated endocytosis, involving megalin and cubilin, mediates renal proximal-tubular reabsorption and is decreased in Dent disease because of mutations of the chloride/proton antiporter, chloride channel-5 (CLC-5), resulting in low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and renal failure. To facilitate studies of receptor-mediated endocytosis and the role of CLC-5, we established conditionally immortalized proximal-tubular epithelial cell lines (ciPTECs) from three patients with CLC-5 mutations (30:insH, R637X, and del132-241) and a normal male. Confocal microscopy using the tight junction marker zona occludens-1 (ZO-1) and end-binding protein-1 (EB-1), which is specific for the plus end of microtubules demonstrated that the ciPTECs polarized. Receptor-mediated endocytic uptake of fluorescent albumin and transferrin in 30:insH and R637X ciPTECs was significantly decreased, compared with normal ciPTECs, and could be further reduced by competition with 10-fold excess of unlabeled albumin and transferrin, whereas in the del132-241 ciPTEC, receptor-mediated endocytic uptake was abolished. Investigation of endosomal acidification by live-cell imaging of pHluorin-VAMP2 (vesicle-associated membrane protein-2), a pH-sensitive-GFP construct, revealed that the endosomal pH in normal and 30:insH ciPTECs was similar, whereas in del132-241 and R637X ciPTECs, it was significantly more alkaline, indicating defective acidification in these ciPTECs. The addition of bafilomycin-A1, a V-ATPase inhibitor, raised the pH significantly in all ciPTECs, demonstrating that the differences in acidification were not due to alterations in the V-ATPase, but instead to abnormalities of CLC-5. Thus, our studies, which have established human Dent disease ciPTECs that will facilitate studies of mechanisms in renal reabsorption, demonstrate that Dent disease-causing CLC-5 mutations have differing effects on endosomal acidification and receptor-mediated endocytosis that may not be coupled.
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PMID:Receptor-mediated endocytosis and endosomal acidification is impaired in proximal tubule epithelial cells of Dent disease patients. 2357 77