title: Physiology of electrogenic SLC26 paralogues.
abstract: SLC26 anion exchangers transport monovalent and divalent anions, with a diversity of anion specificity and stoichiometry. Our microelectrode studies indicate that several SLC26 members are electrogenic. We reported that Slc26a6 functions as a Cl-/formate, Cl-/oxalate, Cl-/OH- and electrogenic Cl-/nHCO3- exchanger. Recently, we have also confirmed that Slc26a7 does not behave as a Cl-/HCO3- exchanger but does function as an electrogenic anion conductance, perhaps a channel. We have also cloned murine Slc26a9, which is strongly expressed in the respiratory tract and stomach. Radioisotope uptakes in Xenopus oocytes indicate that Slc26a9 is a highly selective anion exchanger, transporting Cl- but neither formate, oxalate, nor SO42-. We also utilized electrophysiology to voltage clamp (VC) and/or measure intracellular pH (pHi), Cl- ([Cl-],) and Na+ ([Na+]i), in response to various ion replacements. Cl- removal in HCO3- depolarizes oocytes (to > +60mV), alkalinizes oocytes, and decreases aCl-i. Slc26a9 thus functions as an electrogenic nCl-/HCO3- exchanger, suggesting a role in pulmonary and gastric HCO3- secretion and/or CO2 transport. VC experiments revealed channel-like currents (>10 microA at -60mV and >80 microA at +60mV) mediated by Slc26a9 in the presence and absence of HCO3-. Our experiments and those of others continue to reveal additional characteristics and unique roles for this new class of electrogenic anion transporters.
authors.affiliation: Physiology & Biophysics, Case Western Reserve University, School of Medicine, Cleveland, OH 44106-4970, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Romero
authors.forename: Min-Hwang
authors.initials: MH
authors.lastname: Chang
authors.forename: Consuelo
authors.initials: C
authors.lastname: Plata
authors.forename: Kambiz
authors.initials: K
authors.lastname: Zandi-Nejad
authors.forename: Adriana
authors.initials: A
authors.lastname: Mercado
authors.forename: Vadjista
authors.initials: V
authors.lastname: Broumand
authors.forename: Caroline R
authors.initials: CR
authors.lastname: Sussman
authors.forename: David B
authors.initials: DB
authors.lastname: Mount
mesh_terms: D000818:Animals; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D003001:Cloning, Molecular; D017136:Ion Transport; D051379:Mice; D008954:Models, Biological; D009865:Oocytes; D018408:Patch-Clamp Techniques; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D013270:Stomach / Q000166:cytology; D000076988:Sulfate Transporters
chemical_list: D017920:Antiporters; D002712:Chlorides; D012333:RNA, Messenger; C455628:SLC26A9 protein, human; D000076988:Sulfate Transporters