Congenital chloride-losing diarrhea causing mutations in the STAS domain result in misfolding and mistrafficking of SLC26A3

Michael R. Dorwart, Nikolay Shcheynikov, Jennifer M R Baker, Julie D. Forman-Kay, Shmuel Muallem, Philip J. Thomas

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

Congenital chloride-losing diarrhea (CLD) is a genetic disorder causing watery stool and dehydration. Mutations in SLC26A3 (solute carrier 26 family member 3), which functions as a coupled Cl-/HCO3 - exchanger, cause CLD. SLC26A3 is a membrane protein predicted to contain 12 transmembrane-spanning α-helices and a C-terminal STAS (sulfate transporters and anti-sigma-factor) domain homologous to the bacterial anti-sigma-factor antagonists. The STAS domain is required for SLC26A3 Cl -/HCO3- exchange function and for the activation of cystic fibrosis transmembrane conductance regulator by SLC26A3. Here we investigate the molecular mechanism(s) by which four CLD-causing mutations (ΔY526/7, I544N, I675/6ins, and G702Tins) in the STAS domain lead to disease. In a heterologous mammalian expression system biochemical, immunohistochemical, and ion transport experiments suggest that the four CLD mutations cause SLC26A3 transporter misfolding and/or mistrafficking. Expression studies with the isolated STAS domain suggest that the I675/6ins and G702Tins mutations disrupt the STAS domain directly, whereas limited proteolysis experiments suggest that the ΔY526/7 and I544N mutations affect a later step in the folding and/or trafficking pathway. The data suggest that these CLD-causing mutations cause disease by at least two distinct molecular mechanisms, both ultimately leading to loss of functional protein at the plasma membrane.

Original languageEnglish (US)
Pages (from-to)8711-8722
Number of pages12
JournalJournal of Biological Chemistry
Volume283
Issue number13
DOIs
StatePublished - Mar 28 2008

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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