Expression of band 3 anion exchanger induces chloride current and taurine transport: structure-function analysis.

Abstract

Most, but not all, cell types release intracellular organic solutes (e.g. taurine) in response to cell swelling to achieve cell volume regulation. Although this efflux is blocked by classical inhibitors of the electroneutral anion exchanger band 3 (AE1), it is thought to involve an anion channel. The role of band 3 in volume‐dependent taurine transport was determined by expressing, in Xenopus oocytes, band 3 from erythrocytes which do (trout) or do not (mouse) release taurine when swollen. AE1 of both species elicited anion exchange activity, but only trout band 3 showed chloride channel activity and taurine transport. Chimeras constructed from trout and mouse band 3 allowed the identification of some protein domains critically associated with channel activity and taurine transport. The data provide evidence that swelling‐induced taurine movements occur via an anion channel which is dependent on, or controlled by, band 3. They suggest the involvement of proteins of the band 3 (AE) family in cell volume regulation.

Evidence for Up-regulation of the Endogenous Na-K-2Cl Co-transporter by Molecular Interactions with the Anion Exchanger tAE1 Expressed in Xenopus Oocyte

“…Influx Measurements-Cl influx measurements were done as described previously (13,15). Rb influx measurements were done in media containing 10 Ϫ4 M ouabain to avoid looking at K ϩ movements through the Na-K-ATPase.…”

“…Electrophysiology-Electrophysiological parameters were measured as described previously (13) Chimera Construction-Except for TB3-gyraseB, all other chimera constructions are described in previously published papers (13). 2 The chimera tAE1-gyraseB was made by PCR with plasmids pSP64tAE1 and pcDNA3Raf-gyrB.…”

“…All of the AE polypeptides can be divided into two main domains of about the same size: an N-terminal cytoplasmic domain interacting with cytoskeleton and a membrane spanning domain, which is responsible for ion translocation, with a short C-terminal end in the cytoplasm. By expression studies of tAE1 in Xenopus oocytes, we have demonstrated previously that this normally electroneutral anion exchanger is able to form an anion conductive path-way permeable to different charged or neutral osmolytes such as urea, choline, sorbitol, Na ϩ , and K ϩ (13)(14)(15). In physiological conditions, these transport properties of tAE1 are activated by a decrease in intracellular ionic strength in swollen erythrocytes, and they are involved in the cell regulatory volume decrease response (16,17).…”

Leaky Cl − –HCO 3 − exchangers: cation fluxes via modified AE1

“…In fishes, particularly trout, it has been known for a decade that trout band 3 (tAE1) has important extra transport properties, and does not function strictly in an anion exchange mode (Guizouarn et al 2001). Experiments with oocyte expression have confirmed that tAE1 can function predominantly as an anion channel, but simultaneously as a transport pathway for organic osmolytes, and monovalent cations, indicating a high degree of promiscuity (Fievet et al 1995(Fievet et al , 1998Guizouarn et al 2001). Physiologically, this functional modification is for cell volume regulation, in response to cell swelling: the classical regulatory volume decrease.…”

Propriétés inattendues de l’échangeur anionique du globule rouge : la leçon des poissons

“…Deux études indépendantes, l'une sur la régulation de volume cellulaire des globules rouges de truite et l'autre sur la perméabilité membranaire des hématies de patients souffrant d'anémies hémoly-tiques héréditaires, ont permis de démas-quer une fonction de transport des cations tout à fait inattendue pour un AE1. Nous avons montré il y a plusieurs années que, contrairement aux bandes 3 de mammifères, la bande 3 des globules rouges de truite était capable d'adopter une conformation canal anionique permettant le transport à travers la membrane plasmique de solutés tels le Na, le K mais aussi la taurine, principal acide aminé contenu dans ces cellules [4,5]. Cette conformation est induite par la dilution des élec-trolytes intracellulaires lors d'une entrée d'eau importante dans la cellule [6].…”