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Correspondence to Tsung-Yu Chen: tycchen{at}ucdavis.edu
The effect of intracellular adenosine triphosphate (ATP) on the "common gating" of the CLC-1 chloride channel has been studied by several laboratories with controversial results. Our previous study on the channel expressed in Xenopus oocytes using excised inside-out patch-clamp methods showed a robust effect of ATP in shifting the open probability curve of the common gate toward more depolarizing voltages (Tseng, P.Y., B. Bennetts, and T.Y. Chen. 2007. J. Gen. Physiol. 130:217–221). The results were consistent with those from studying the channel expressed in mammalian cells using whole cell recording methods (Bennetts, B., M.W. Parker, and B.A. Cromer. 2007. J. Biol. Chem. 282:32780–32791). However, a recent study using excised-patch recording methods for channels expressed in Xenopus oocytes reported that ATP had no direct effect on CLC-1 (Zifarelli, G., and M. Pusch. 2008. J. Gen. Physiol. 131:109–116). Here, we report that oxidation of CLC-1 may be the culprit underlying the controversy. When patches were excised from mammalian cells, the sensitivity to ATP was lost quickly—within 2–3 min. This loss of ATP sensitivity could be prevented or reversed by reducing agents. On the other hand, CLC-1 expressed in Xenopus oocytes lost the ATP sensitivity when patches were treated with oxidizing reagents. These results suggest a novel view in muscle physiology that the mechanisms controlling muscle fatigability may include the oxidation of CLC-1.
Abbreviations used in this paper: β-ME, β-mercaptoethanol; CuPhe, copper phenanthroline; DTT, dithiolthreitol; HEK, human embryonic kidney; MTS, methane thiosulfonate(s); redox, oxidation and reduction.
© 2008 Zhang et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jgp.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
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