Digenic Inheritance in Cystinuria Mouse Model

Espino, Meritxell; Font-Llitjós, Mariona; Vilches, Clara; Salido, Eduardo; Prat, Esther; Heredia, Miguel López de; Palacı́n, Manuel; Nunes, Virginia

doi:10.1371/journal.pone.0137277

Cited by 10 publications

(12 citation statements)

References 19 publications

(31 reference statements)

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“…After overnight incubation for immunoprecipitation in the presence of detergent, AGT1 appeared more abundantly as homodimers (around 70 kDa in To further confirm rBAT as an AGT1 partner, the expression of AGT1 was examined in mice carrying a missense mutation in rBAT causing the loss of rBAT protein in brush-border membrane vesicles (BBMVs) (Fig. 1C, Right) (10,22). In the mutant mice, the band corresponding to the complex of AGT1 and its heavy chain detected by anti-AGT1 antibody was diminished in BBMVs, supporting the idea that rBAT is the heavy chain of AGT1 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…4F2hc interacts with most of the light chains in HATs whereas rBAT has been known to form a heterodimer only with b 0,+ AT/ SLC7A9. Because the rBAT-b 0,+ AT complex is presented on the apical membrane of proximal tubules in the kidney and involved in the reabsorption of cystine and dibasic amino acids, the mutations of either rBAT or b 0,+ AT cause cystinuria, a disorder of renal reabsorption of cystine and dibasic amino acids leading to serious renal lithiasis due to low solubility of cystine (7).An unsolved paradox on rBAT and b 0,+ AT has been the discrepancy between the distribution of rBAT and that of b 0,+ AT (5,(8)(9)(10). rBAT is the most abundant in the S3 segment of proximal tubules, and its expression declines toward the S1 segment (11,12).…”

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confidence: 99%

“…An unsolved paradox on rBAT and b 0,+ AT has been the discrepancy between the distribution of rBAT and that of b 0,+ AT (5,(8)(9)(10). rBAT is the most abundant in the S3 segment of proximal tubules, and its expression declines toward the S1 segment (11,12).…”

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confidence: 99%

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Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Nagamori

Wiriyasermkul

Guarch

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Heterodimeric amino acid transporters play crucial roles in epithelial transport, as well as in cellular nutrition. Among them, the heterodimer of a membrane protein b 0,+ AT/SLC7A9 and its auxiliary subunit rBAT/ SLC3A1 is responsible for cystine reabsorption in renal proximal tubules. The mutations in either subunit cause cystinuria, an inherited amino aciduria with impaired renal reabsorption of cystine and dibasic amino acids. However, an unsolved paradox is that rBAT is highly expressed in the S3 segment, the late proximal tubules, whereas b 0,+ AT expression is highest in the S1 segment, the early proximal tubules, so that the presence of an unknown partner of rBAT in the S3 segment has been proposed. In this study, by means of coimmunoprecipitation followed by mass spectrometry, we have found that a membrane protein AGT1/SLC7A13 is the second partner of rBAT. AGT1 is localized in the apical membrane of the S3 segment, where it forms a heterodimer with rBAT. Depletion of rBAT in mice eliminates the expression of AGT1 in the renal apical membrane. We have reconstituted the purified AGT1-rBAT heterodimer into proteoliposomes and showed that AGT1 transports cystine, aspartate, and glutamate. In the apical membrane of the S3 segment, AGT1 is suggested to locate itself in close proximity to sodium-dependent acidic amino acid transporter EAAC1 for efficient functional coupling. EAAC1 is proposed to take up aspartate and glutamate released into luminal fluid by AGT1 due to its countertransport so that preventing the urinary loss of aspartate and glutamate. Taken all together, AGT1 is the long-postulated second cystine transporter in the S3 segment of proximal tubules and a possible candidate to be involved in isolated cystinuria.amino acid transporter | cystine reabsorption | cystinuria | kidney T he heteromeric amino acid transporter (HAT) family is one of the major amino acid transporter families responsible for cellular uptake and epithelial transport (1-3). HATs form heterodimers composed of a 12 membrane spanning light chain (SLC7) that catalyzes transport functions and a single membrane spanning heavy chain (SLC3) essential for plasma membrane localization and stabilization of the light chains. Two heavy chains, SLC3A1/ rBAT and SLC3A2/4F2hc/CD98hc, covalently bound to light chains via a disulfide bridge have been identified so far (4-6). 4F2hc interacts with most of the light chains in HATs whereas rBAT has been known to form a heterodimer only with b 0,+ AT/ SLC7A9. Because the rBAT-b 0,+ AT complex is presented on the apical membrane of proximal tubules in the kidney and involved in the reabsorption of cystine and dibasic amino acids, the mutations of either rBAT or b 0,+ AT cause cystinuria, a disorder of renal reabsorption of cystine and dibasic amino acids leading to serious renal lithiasis due to low solubility of cystine (7).An unsolved paradox on rBAT and b 0,+ AT has been the discrepancy between the distribution of rBAT and that of b 0,+ AT (5,(8)(9)(10). rBAT is the most abundant in the S3 segmen...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Nagamori

Wiriyasermkul

Guarch

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In fact, cystinuria is common in many canine breeds and some wild carnivore species and also occurs frequently in humans (1: 7,000) [ 1 ]. A spontaneous cystinuria murine model has also recently been described (129S2/SvPasCrl) (p.Glu383Lys in SLC3A1 ) and 3 knockout murine models (C3HeB/FeJ-MRL/MpJ, 129P2/OlaHsd-57BL/6J) (p.Asp140Gly in SLC3A1 , disruption of exon 3 to 9 in in SLC7A9 , compound heterozygotes of the two variants [C3HeB/FeJ/MRL/MpJ-129P2/OlaHsd/57BL/6J]) have been generated [ 10 , 22 – 24 ].…”

Section: Discussionmentioning

confidence: 99%

“…The rBAT and b o,+ AT proteins are nearly the same size in all mammals (number of amino acids of rBAT/b o,+ AT: 681/490 in cats, 685/487 in humans, 700/490 in dogs, 685/487 in mice) and the amino acid sequences of b o,+ AT are highly conserved (humans 90%, dogs 95% and mice 89% homologous to cats) thereby allowing functional comparisons. While the molecular genetic basis for this disease has been described in many human patients [ 1 ], 4 murine models [ 10 , 22 – 24 ], 5 canine breeds (Raj et al unpublished, 2016) [ 3 ], and one cat with an SLC3A1 variant [ 6 ], we report here on the first 5 SLC7A9 variants in cystinuric cats.…”

Section: Discussionmentioning

confidence: 99%

Cystinuria Associated with Different SLC7A9 Gene Variants in the Cat

et al. 2016

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Cystinuria is a classical inborn error of metabolism characterized by a selective proximal renal tubular defect affecting cystine, ornithine, lysine, and arginine (COLA) reabsorption, which can lead to uroliths and urinary obstruction. In humans, dogs and mice, cystinuria is caused by variants in one of two genes, SLC3A1 and SLC7A9, which encode the rBAT and bo,+AT subunits of the bo,+ basic amino acid transporter system, respectively. In this study, exons and flanking regions of the SLC3A1 and SLC7A9 genes were sequenced from genomic DNA of cats (Felis catus) with COLAuria and cystine calculi. Relative to the Felis catus-6.2 reference genome sequence, DNA sequences from these affected cats revealed 3 unique homozygous SLC7A9 missense variants: one in exon 5 (p.Asp236Asn) from a non-purpose-bred medium-haired cat, one in exon 7 (p.Val294Glu) in a Maine Coon and a Sphinx cat, and one in exon 10 (p.Thr392Met) from a non-purpose-bred long-haired cat. A genotyping assay subsequently identified another cystinuric domestic medium-haired cat that was homozygous for the variant originally identified in the purebred cats. These missense variants result in deleterious amino acid substitutions of highly conserved residues in the bo,+AT protein. A limited population survey supported that the variants found were likely causative. The remaining 2 sequenced domestic short-haired cats had a heterozygous variant at a splice donor site in intron 10 and a homozygous single nucleotide variant at a branchpoint in intron 11 of SLC7A9, respectively. This study identifies the first SLC7A9 variants causing feline cystinuria and reveals that, as in humans and dogs, this disease is genetically heterogeneous in cats.

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Cystinuria: genetic aspects, mouse models, and a new approach to therapy

et al. 2018

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Cystinuria, a genetic disorder of cystine transport, is characterized by excessive excretion of cystine in the urine and recurrent cystine stones in the kidneys and, to a lesser extent, in the bladder. Males generally are more severely affected than females. The disorder may lead to chronic kidney disease in many patients. The cystine transporter (b 0,+ ) is a heterodimer consisting of the rBAT (encoded by SLC3A1) and b 0,+ AT (encoded by SLC7A9) subunits joined by a disulfide bridge. The molecular basis of cystinuria is known in great detail, and this information is now being used to define genotype-phenotype correlations. Current treatments for cystinuria include increased fluid intake to increase cystine solubility and the administration of thiol drugs for the more severe cases. These drugs, however, have poor patient compliance due to adverse effects. Thus, there is a need to reduce or eliminate the risks associated with therapy for cystinuria. Four mouse models for cystinuria have been described and these models provide a resource for evaluating the safety and efficacy of new therapies for cystinuria. We are evaluating a new approach for the treatment of cystine stones based on the inhibition of cystine crystal growth by cystine analogs. Our ongoing studies indicate that cystine diamides are effective in preventing cystine stone formation in the Slc3a1 knockout mouse model for cystinuria. In addition to crystal growth, crystal aggregation is required for stone formation. Male and female mice with cystinuria have comparable levels of crystalluria, but very few female mice form stones. The identification of

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Digenic Inheritance in Cystinuria Mouse Model

Cited by 10 publications

References 19 publications

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Cystinuria Associated with Different SLC7A9 Gene Variants in the Cat

Cystinuria: genetic aspects, mouse models, and a new approach to therapy

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