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Localization of Slc26a9 and role of the STAS domain
Author(s) -
Sindic Aleksandra,
Plata Consuelo,
Sussman Caroline R.,
Mount David B.,
Chang MinHwang,
Romero Michael F.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a839
Subject(s) - chemistry , ion transporter , biophysics , biochemistry , biology , membrane
Some Slc26 family members function as Cl − /HCO 3 − exchangers (Slc26a3, ‐a4, ‐a6), whereas others function as Cl ‐ channels (Slc26a7) or anion‐gated molecular motors (Slc26a5). We have reported that Slc26a9 functions as a Cl − /HCO 3 − exchanger with a high Cl − conductance. We have now evaluated the role of S ulfate T ransporter A nti‐ S igma factor antagonist (STAS) domain, located at the protein's C‐terminus, by deleting the STAS domain (Slc26a9‐Δ STAS). We expressed mouse Slc26a9 and Slc26a9‐ΔSTAS in Xenopus oocytes and measured membrane potential ( V m ), currents, and intracellular pH and Cl − using microelectrodes. Slc26a9‐ΔSTAS deletes the STAS domain leaving intact the final C‐terminus. This deletion reduced Slc26a9 dependent currents. However, Slc26a9‐ STAS was still capable of HCO 3 − transport showing primarily a reduction in Cl ‐ conductance. To localize Slc26a9 protein we developed a chicken antibody against a C‐terminal peptide of mouse Slc26a9. Slc26a9 is found in rat respiratory tract (tracheal submucosal glands) and gut (esophagus and stomach). Our antibody not only recognized rat but also human SLC26A9 in CaLu‐3 cells (human airway submucosal gland cell‐line). We conclude that Slc26a9 is a Cl − /HCO 3 − exchanger, and, like Slc26a7, shows Cl − channel‐like currents which are diminished by the deletion of the STAS domain. Regulation of Slc26a9‐dependent Cl − conductance could be important for anion transport in the respiratory and gastrointestinal systems. DK56218, AHA, Wadsworth Foundation.