Pathophysiology of functional mutations of the thiazide-sensitive Na-Cl cotransporter in Gitelman disease

Ernesto Sabath, Patricia Meade, Jennifer Berkman, Paola De Los Heros, Erika Moreno, Norma A. Bobadilla, Norma Vázqaez, David Ellison, Gerardo Gamba

Research output: Contribution to journalArticle

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Abstract

Most of the missense mutations that have been described in the human SLC12A3 gene encoding the thiazide-sensitive Na+-Cl- cotransporter (TSC, NCC, or NCCT), as the cause of Gitelman disease, block TSC function by interfering with normal protein processing and glycosylation. However, some mutations exhibit considerable activity. To investigate the pathogenesis of Gitelman disease mediated by such mutations and to gain insights into structure-function relationships on the cotransporter, five functional disease mutations were introduced into mouse TSC cDNA, and their expression was determined in Xenopus laevis oocytes. Western blot analysis revealed immunoreactive bands in all mutant TSCs that were undistinguishable from wild-type TSC. The activity profile was: wild-type TSC (100%) > G627V (66%) > R935Q (36%) = V995M (32%) > G610S (12%) > A585V (6%). Ion transport kinetics in all mutant clones were similar to wild-type TSC, except in G627V, in which a small but significant increase in affinity for extracellular Cl - was observed. In addition, G627V and G610S exhibited a small increase in metolazone affinity. The surface expression of wild-type and mutant TSCs was performed by laser-scanning confocal microscopy. All mutants exhibited a significant reduction in surface expression compared with wild-type TSC, with a profile similar to that observed in functional expression analysis. Our data show that biochemical and functional properties of the mutant TSCs are similar to wild-type TSC but that the surface expression is reduced, suggesting that these mutations impair the insertion of a functional protein into the plasma membrane. The small increase in Cl- and thiazide affinity in G610S and G627V suggests that the beginning of the COOH-terminal domain could be implicated in defining kinetic properties.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Physiology
Volume287
Issue number2 56-2
DOIs
StatePublished - Aug 2004

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Mutation
Metolazone
Thiazides
Insertional Mutagenesis
Ion Transport
Xenopus laevis
Missense Mutation
Glycosylation
Confocal Microscopy
Oocytes
Complementary DNA
Clone Cells
Western Blotting
Cell Membrane
Genes
thiazide receptor
Proteins

Keywords

  • Distal tubule
  • Diuretics
  • Na-Cl cotransporter
  • Salt reabsorption
  • Structure

ASJC Scopus subject areas

  • Physiology

Cite this

Pathophysiology of functional mutations of the thiazide-sensitive Na-Cl cotransporter in Gitelman disease. / Sabath, Ernesto; Meade, Patricia; Berkman, Jennifer; De Los Heros, Paola; Moreno, Erika; Bobadilla, Norma A.; Vázqaez, Norma; Ellison, David; Gamba, Gerardo.

In: American Journal of Physiology - Renal Physiology, Vol. 287, No. 2 56-2, 08.2004.

Research output: Contribution to journalArticle

Sabath, Ernesto ; Meade, Patricia ; Berkman, Jennifer ; De Los Heros, Paola ; Moreno, Erika ; Bobadilla, Norma A. ; Vázqaez, Norma ; Ellison, David ; Gamba, Gerardo. / Pathophysiology of functional mutations of the thiazide-sensitive Na-Cl cotransporter in Gitelman disease. In: American Journal of Physiology - Renal Physiology. 2004 ; Vol. 287, No. 2 56-2.
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abstract = "Most of the missense mutations that have been described in the human SLC12A3 gene encoding the thiazide-sensitive Na+-Cl- cotransporter (TSC, NCC, or NCCT), as the cause of Gitelman disease, block TSC function by interfering with normal protein processing and glycosylation. However, some mutations exhibit considerable activity. To investigate the pathogenesis of Gitelman disease mediated by such mutations and to gain insights into structure-function relationships on the cotransporter, five functional disease mutations were introduced into mouse TSC cDNA, and their expression was determined in Xenopus laevis oocytes. Western blot analysis revealed immunoreactive bands in all mutant TSCs that were undistinguishable from wild-type TSC. The activity profile was: wild-type TSC (100{\%}) > G627V (66{\%}) > R935Q (36{\%}) = V995M (32{\%}) > G610S (12{\%}) > A585V (6{\%}). Ion transport kinetics in all mutant clones were similar to wild-type TSC, except in G627V, in which a small but significant increase in affinity for extracellular Cl - was observed. In addition, G627V and G610S exhibited a small increase in metolazone affinity. The surface expression of wild-type and mutant TSCs was performed by laser-scanning confocal microscopy. All mutants exhibited a significant reduction in surface expression compared with wild-type TSC, with a profile similar to that observed in functional expression analysis. Our data show that biochemical and functional properties of the mutant TSCs are similar to wild-type TSC but that the surface expression is reduced, suggesting that these mutations impair the insertion of a functional protein into the plasma membrane. The small increase in Cl- and thiazide affinity in G610S and G627V suggests that the beginning of the COOH-terminal domain could be implicated in defining kinetic properties.",
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AU - Sabath, Ernesto

AU - Meade, Patricia

AU - Berkman, Jennifer

AU - De Los Heros, Paola

AU - Moreno, Erika

AU - Bobadilla, Norma A.

AU - Vázqaez, Norma

AU - Ellison, David

AU - Gamba, Gerardo

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