The ClC-3 chloride channel promotes acidification of lysosomes in CHO-K1 and Huh-7 cells

Xinhua Li, Ting Wang, Zhifang Zhao, Steven A. Weinman


ClC-3 is a voltage-gated Clchannel that is highly conserved and widely expressed, although its function, localization, and properties remain a matter of considerable debate. In this study, we have shown that heterologous expression of ClC-3 in either Chinese hamster ovary (CHO-K1) or human hepatoma (Huh-7) cells results in the formation of large, acidic vesicular structures within cells. Vesicle formation is prevented by bafilomycin, an inhibitor of the vacuolar ATPase, and is not induced by an E224A mutant of ClC-3 with altered channel activity. This demonstrates that vesicle formation requires both proton pumping and Clchannel activity. Manipulation of the intracellular Clconcentration demonstrated that the ClC-3-associated vesicles shrink and swell consistent with a highly Cl-permeable membrane. The ClC-3 vesicles were identified as lysosomes based on their colocalization with the lysosome-associated proteins lamp-1, lamp-2, and cathepsin D and on their failure to colocalize with fluorescently labeled endosomes. We conclude that ClC-3 is an intracellular channel that conducts Cl when it is present in intracellular vesicles. Its overexpression results in its appearance in enlarged lysosome-like structures where it contributes to acidification by charge neutralization.

  • endosomes
  • bafilomycin
  • ClC channels


  • This work was supported by National Institute of Diabetes and Digestive and Kidney DiseasesGrant DK-42917.

  • Address for reprint requests and other correspondence: S. A. Weinman, Dept. of Physiology and Biophysics, Univ. of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0641 (E-mail: sweinman{at}

  • The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

  • First published February 13, 2002;10.1152/ajpcell.00504.2001

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