Congenital Chloride-losing Diarrhea Causing Mutations in the STAS Domain Result in Misfolding and Mistrafficking of SLC26A3

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-...

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Bibliographic Details
Published in:The Journal of biological chemistry 2008-03, Vol.283 (13), p.8711-8722
Main Authors: Dorwart, Michael R., Shcheynikov, Nikolay, Baker, Jennifer M.R., Forman-Kay, Julie D., Muallem, Shmuel, Thomas, Philip J.
Format: Article
Language:English
Subjects:
Amino Acid Motifs
Animals
Antiporters - chemistry
Antiporters - genetics
Antiporters - metabolism
Cell Line
Chloride-Bicarbonate Antiporters
Chlorides - metabolism
Chlorocebus aethiops
Circular Dichroism
Conserved Sequence
Diarrhea - congenital
Diarrhea - genetics
Diarrhea - metabolism
Humans
Molecular Sequence Data
Mutation - genetics
Protein Transport
Sequence Alignment
Sulfate Transporters
Temperature
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Summary: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.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M704328200