title: Acute regulation of the SLC26A3 congenital chloride diarrhoea anion exchanger (DRA) expressed in Xenopus oocytes.
abstract: Mutations in the human SLC26A3 gene, also known as down-regulated in adenoma (hDRA), cause autosomal recessive congenital chloride-losing diarrhoea (CLD). hDRA expressed in Xenopus oocytes mediated bidirectional Cl--Cl- and Cl--HCO3- exchange. In contrast, transport of oxalate was low, and transport of sulfate and of butyrate was undetectable. Two CLD missense disease mutants of hDRA were nonfunctional in oocytes. Truncation of up to 44 C-terminal amino acids from the putatively cytoplasmic C-terminal hydrophilic domain left transport function unimpaired, but deletion of the adjacent STAS (sulfate transporter anti-sigma factor antagonist) domain abolished function. hDRA-mediated Cl- transport was insensitive to changing extracellular pH, but was inhibited by intracellular acidification and activated by NH4+ at acidifying concentrations. These regulatory responses did not require the presence of either hDRA's N-terminal cytoplasmic tail or its 44 C-terminal amino acids, but they did require more proximate residues of the C-terminal cytoplasmic domain. Although only weakly sensitive to inhibition by stilbenes, hDRA was inhibited with two orders of magnitude greater potency by the anti-inflammatory drugs niflumate and tenidap. cAMP-insensitive Cl--HCO3- exchange mediated by hDRA gained modest cAMP sensitivity when co-expressed with cystic fibrosis transmembrane conductance regulator (CFTR). Despite the absence of hDRA transcripts in human cell lines derived from CFTR patients, DRA mRNA was present at wild-type levels in proximal colon and nearly so in the distal ileum of CFTR(-/-) mice. Thus, pharmacological modulation of DRA might be a useful adjunct treatment of cystic fibrosis.
authors.affiliation: Molecular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: Marina N
authors.initials: MN
authors.lastname: Chernova
authors.forename: Lianwei
authors.initials: L
authors.lastname: Jiang
authors.forename: Boris E
authors.initials: BE
authors.lastname: Shmukler
authors.forename: Clifford W
authors.initials: CW
authors.lastname: Schweinfest
authors.forename: Paola
authors.initials: P
authors.lastname: Blanco
authors.forename: Steven D
authors.initials: SD
authors.lastname: Freedman
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Stewart
authors.forename: Seth L
authors.initials: SL
authors.lastname: Alper
mesh_terms: D000818:Animals; D017920:Antiporters; D001639:Bicarbonates / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm; D003967:Diarrhea / Q000151:congenital / Q000235:genetics / Q000503:physiopathology; D005260:Female; D015870:Gene Expression; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006982:Hypertonic Solutions / Q000494:pharmacology; D007082:Ileum / Q000502:physiology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D018181:Mice, Inbred CFTR; D016296:Mutagenesis; D020125:Mutation, Missense; D009865:Oocytes / Q000502:physiology; D017434:Protein Structure, Tertiary; D000076988:Sulfate Transporters; D014981:Xenopus
chemical_list: D017920:Antiporters; D001639:Bicarbonates; C505032:CFTR protein, human; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D006982:Hypertonic Solutions; D008565:Membrane Proteins; C081011:SLC26A3 protein, human; C489860:Slc26a3 protein, mouse; D000076988:Sulfate Transporters; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP