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This Article Full Text Full Text (PDF) Supplemental data All Versions of this Article: 584/1/59    most recent jphysiol.2007.136119v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Stewart, A. K. Articles by Alper, S. L. Search for Related Content PubMed PubMed Citation Articles by Stewart, A. K. Articles by Alper, S. L. Related Collections Cellular

¹ Department of Medicine, Harvard Medical School
² Molecular and Vascular Medicine Unit and Renal Unit, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
³ Burdon-Sanderson Cardiac Science Centre and Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK

The widely expressed anion exchanger polypeptide AE2/SLC4A2 is acutely inhibited by acidic intracellular (pH_i), by acidic extracellular pH (pH_o), and by the calmodulin inhibitor, calmidazolium, whereas it is acutely activated by NH₄⁺. The homologous erythroid/kidney AE1/SLC4A1 polypeptide is insensitive to these regulators. Each of these AE2 regulatory responses requires the presence of AE2's C-terminal transmembrane domain (TMD). We have now measured ³⁶Cl^– efflux from Xenopus oocytes expressing bi- or tripartite AE2–AE1 chimeras to define TMD subregions in which AE2-specific sequences contribute to acute regulation. The chimeric AE polypeptides were all functional at pH_o 7.4, with the sole exception of AE2_(1-920)/AE1_(613-811)/AE2_(1120-1237). Reciprocal exchanges of the large third extracellular loops were without effect. AE2 regulation by pH_i, pH_o and NH₄⁺ was retained after substitution of C-terminal AE2 amino acids 1120–1237 (including the putative second re-entrant loop, two TM spans and the cytoplasmic tail) with the corresponding AE1 sequence. In contrast, the presence of this AE2 C-terminal sequence was both necessary and sufficient for inhibition by calmidazolium. All other tested TMD substitutions abolished AE2 pH_i sensitivity, abolished or severely attenuated sensitivity to pH_o and removed sensitivity to NH₄⁺. Loss of AE2 pH_i sensitivity was not rescued by co-expression of a complementary AE2 sequence within separate full-length chimeras or AE2 subdomains. Thus, normal regulation of AE2 by pH and other ligands requires AE2-specific sequence from most regions of the AE2 TMD, with the exceptions of the third extracellular loop and a short C-terminal sequence. We conclude that the individual TMD amino acid residues previously identified as influencing acute regulation of AE2 exert that influence within a regulatory structure requiring essential contributions from multiple regions of the AE2 TMD.

(Received 8 May 2007; accepted after revision 6 August 2007; first published online 9 August 2007)
Corresponding author S. L. Alper: RW763 East Campus, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215, USA. Email: salper{at}caregroup.harvard.edu

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				M. N. Chernova, A. K. Stewart, P. N. Barry, M. L. Jennings, and S. L. Alper Mouse Ae1 E699Q mediates SO42-i/aniono exchange with [SO42-]i-dependent reversal of wild-type pHo sensitivity Am J Physiol Cell Physiol, August 1, 2008; 295(2): C302 - C312. [Abstract] [Full Text] [PDF]

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