Consequences of point mutations in trout anion exchanger 1 (tAE1) transmembrane domains: Evidence that tAE1 can behave as a chloride channel
✍ Scribed by Sonia Martial; Hélène Guizouarn; Nicole Gabillat; Bernard Pellissier; Franck Borgese
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 298 KB
- Volume
- 207
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
In this study, we have shown that, when expressed in Xenopus oocytes, trout anion exchanger 1 (tAE1) was able to act as a bifunctional protein, either an anion exchanger or a chloride conductance. Point mutations of tAE1 were carried out and their effect on Cl^−^ conductance and Cl^−^ unidirectional flux were studied. We have shown that mutations made in transmembrane domain 7 had dramatic effects on tAE1 function. Indeed, when these residues were mutated, either individually or together (mutants E632K, D633G, and ED/KG), Cl^−^ conductance was reduced to 28–44% that of wild‐type tAE1. Moreover, ion substitution experiments showed that anion selectivity was altered. However, the exchanger function was unchanged, as evidenced by the fact that Cl^−^ influx and K~m~ were identical for each of these mutants and similar to the wild‐type protein parameters. By contrast, mutations made in the C‐terminal domains of the protein (R819M, Q829K) affected both transport functions. Cl^−^ conductance was increased by ∼200% with respect to tAE1 and anion selectivity was impaired. Likewise, Cl^−^ influx was increased by ∼260% and was no longer saturable. These and other mutations carried out in transmembrane domains 7, 8, 12–14 of tAE1 allow us to demonstrate without doubt that, in addition to its anion exchanger activity, tAE1 can also function as a chloride channel. Above all, this work led us to identify amino acids involved in this double function organization. J. Cell. Physiol. © 2006 Wiley‐Liss, Inc.