RRC ID 11970
Author Hayashi H, Suruga K, Yamashita Y.
Title Regulation of intestinal Cl-/HCO3- exchanger SLC26A3 by intracellular pH.
Journal Am J Physiol Cell Physiol
Abstract SLC26A3, a Cl(-)/HCO(3)(-) exchanger, is highly expressed in intestinal epithelial cells, and its mutations cause congenital chloride diarrhea. This suggests that SLC26A3 plays a key role in NaCl absorption in the intestine. Electroneutral NaCl absorption in the intestine is mediated by functional coupling of the Na(+)/H(+) exchanger and Cl(-)/HCO(3)(-) exchanger. It is proposed that the coupling of these exchangers may occur as a result of indirect linkage by changes of intracellular pH (pH(i)). We therefore investigated whether SLC26A3 is regulated by pH(i). We generated a hemagglutinin epitope-tagged human SLC26A3 construct and expressed it in Chinese hamster ovary cells. Transport activities were measured with a fluorescent chloride-sensitive dye dihydro-6-methoxy-N-ethylquinolinium iodide (diH-MEQ). pH(i) was clamped at a range of values from 6.0 to 7.4. We monitored the transport activity of SLC26A3 by reverse mode of Cl(-)/HCO(3)(-) and Cl(-)/NO(3)(-) exchange. None of these exchange modes induced membrane potential changes. At constant external pH 7.4, Cl(-)/HCO(3)(-) exchange was steeply inhibited with pH(i) decrease between 7.3 and 6.8 as opposed to thermodynamic prediction. In contrast, however, Cl(-)/NO(3)(-) exchange was essentially insensitive to pH(i) within physiological ranges. We also characterized the pH(i) dependency of COOH-terminal truncation mutants. Removal of the entire COOH-terminal resulted in decrease of the transport activity but did not noticeably affect pH(i) sensitivity. These results suggest that Cl(-)/HCO(3)(-) exchange mode of human SLC26A3 is controlled by a pH-sensitive intracellular modifier site, which is likely in the transmembrane domain. These observations raise the possibility that SLC26A3 activity may be regulated via Na(+)/H(+) exchanger 3 (NHE3) through the alteration of pH(i) under physiological conditions.
Volume 296(6)
Pages C1279-90
Published 2009-6-1
DOI 10.1152/ajpcell.00638.2008
PII 00638.2008
PMID 19321737
MeSH Animals Antiporters / genetics Antiporters / metabolism* Bicarbonates / metabolism* CHO Cells Chloride-Bicarbonate Antiporters Chlorides / metabolism* Cricetinae Cricetulus Fluorescent Dyes / metabolism Humans Hydrogen-Ion Concentration Intestinal Absorption Intestinal Mucosa / metabolism* Membrane Potentials Mutation Nitrates / metabolism Protein Structure, Tertiary Quinolinium Compounds / metabolism Recombinant Fusion Proteins / metabolism Sodium Chloride / metabolism* Sodium-Hydrogen Exchanger 3 Sodium-Hydrogen Exchangers / metabolism Sulfate Transporters Transfection
IF 3.485
Times Cited 18
DNA material D-HA double HA-tagged expression vector (RDB02139)