Physiology of electrogenic SLC26 paralogues.
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.
Romero
Michael F
MF
Physiology & Biophysics, Case Western Reserve University, School of Medicine, Cleveland, OH 44106-4970, USA.
Chang
Min-Hwang
MH
Plata
Consuelo
C
Zandi-Nejad
Kambiz
K
Mercado
Adriana
A
Broumand
Vadjista
V
Sussman
Caroline R
CR
Mount
David B
DB
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
D017920:Antiporters; D002712:Chlorides; D012333:RNA, Messenger; C455628:SLC26A9 protein, human; D000076988:Sulfate Transporters