TY - JOUR
T1 - Hypertonic activation of AE2 anion exchanger in Xenopus oocytes via NHE- mediated intracellular alkalinization
AU - Humphreys, B. D.
AU - Jiang, L.
AU - Chernova, M. N.
AU - Alper, S. L.
PY - 1995
Y1 - 1995
N2 - Xenopus oocytes express endogenous Na+/H+ exchange activity but lack significant endogenous Cl-/HCO3/- exchange activity. Coupled operation of Na+/H+ exchange and Cl-/HCO3/- exchange contributes in many cell types to the cellular response to hypertonic stress. We therefore examined in Xenopus oocytes the osmotic regulation of chloride transport mediated by recombinant anion exchanger proteins AE2 and AE1. Hypotonicity was without effect on either anion transporter. Hypertonicity activated AE2-associated 36Cl- influx and efflux in a time- and osmolarity-dependent manner, whether incremental osmoles were charged or uncharged, but had no measurable effect on AE1 function. Hypertonic stimulation of AE2 was completely inhibited by Na+ removal or by addition of amiloride. In contrast, neither maneuver altered isotonic activity of AE2. Hypertonicity also induced amiloride-sensitive elevation of oocyte intracellular pH (pH(i)), and shifted the sigmoidal relationship of extracellular pH vs. AE2 activity ≥ 0.5 units to the acid. Injection of pH 7.4 buffer into oocytes attenuated both hypertonic alkalinization and activation of AE2-associated 36Cl- influx, without inhibition of isotonic AE2 function. These data demonstrate that recombinant AE2 expressed in Xenopus oocytes is activated by increased pH(i) and that hypertonic activation of AE2 is secondary to hypertonic activation of Na+/H+ exchange.
AB - Xenopus oocytes express endogenous Na+/H+ exchange activity but lack significant endogenous Cl-/HCO3/- exchange activity. Coupled operation of Na+/H+ exchange and Cl-/HCO3/- exchange contributes in many cell types to the cellular response to hypertonic stress. We therefore examined in Xenopus oocytes the osmotic regulation of chloride transport mediated by recombinant anion exchanger proteins AE2 and AE1. Hypotonicity was without effect on either anion transporter. Hypertonicity activated AE2-associated 36Cl- influx and efflux in a time- and osmolarity-dependent manner, whether incremental osmoles were charged or uncharged, but had no measurable effect on AE1 function. Hypertonic stimulation of AE2 was completely inhibited by Na+ removal or by addition of amiloride. In contrast, neither maneuver altered isotonic activity of AE2. Hypertonicity also induced amiloride-sensitive elevation of oocyte intracellular pH (pH(i)), and shifted the sigmoidal relationship of extracellular pH vs. AE2 activity ≥ 0.5 units to the acid. Injection of pH 7.4 buffer into oocytes attenuated both hypertonic alkalinization and activation of AE2-associated 36Cl- influx, without inhibition of isotonic AE2 function. These data demonstrate that recombinant AE2 expressed in Xenopus oocytes is activated by increased pH(i) and that hypertonic activation of AE2 is secondary to hypertonic activation of Na+/H+ exchange.
UR - http://www.scopus.com/inward/record.url?scp=0028888516&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.1995.268.1.c201
DO - 10.1152/ajpcell.1995.268.1.c201
M3 - Article
C2 - 7840148
AN - SCOPUS:0028888516
SN - 0363-6143
VL - 268
SP - C201-C209
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 1 37-1
ER -