Acid-sensitive outwardly rectifying (ASOR) anion channels in human epithelial cells are highly sensitive to temperature and independent of ClC-3

• Published in: Pflügers Archiv Vol. 465; no. 11; pp. 1535 - 1543
• Main Authors: Sato-Numata, Kaori, Numata, Tomohiro, Okada, Toshiaki, Okada, Yasunobu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2013; Springer Nature B.V
• Subjects: Action Potentials; Animals; Antiporters - genetics; Antiporters - metabolism; Biomedical and Life Sciences; Biomedicine; Cell Biology; Chloride Channels - genetics; Chloride Channels - metabolism; Chlorides - metabolism; Cisplatin - pharmacology; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Epithelial Cells - physiology; HEK293 Cells; HeLa Cells; Hot Temperature; Human Physiology; Humans; Hydrogen-Ion Concentration; Ion Channels; Ion Channels - genetics; Ion Channels - metabolism; Mice; Molecular Medicine; Neurosciences; Protons; Receptors; Receptors and Transporters; Chloride channel; ClC-3; ASOR; Thermal sensitivity
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s00424-013-1296-y

A novel type of anion channel activated by extracellular acidification, called acid-sensitive outwardly rectifying (ASOR) anion channel, was shown to be involved in acidotoxic necrotic death in human epithelial cells. However, its biophysical property and molecular identity have remained elusive. In human epithelial HeLa cells, here, whole-cell currents of ASOR anion channel were found to be augmented by warm temperature, with a threshold temperature of 32 °C. Temperature sensitivity of the conductance was found to be high (with Q 10 of 8.8) in the range of body temperature, suggesting a possible involvement of a non-diffusion-limited process such as a transporter-mediated conduction. In this regard, it is interesting that a Cl − /H + antiporter ClC-3 has recently been proposed as a candidate for the ASOR channel. However, siRNA-mediated knockdown of hClC-3 failed to suppress ASOR currents in HeLa cells. Also, endogenous ASOR currents in HEK293T cells were not affected by overexpression of human or mouse ClC-3. Furthermore, functional expression of the ASOR channel was virtually absent in the cisplatin-resistant human cancer KCP-4 cell line despite the fact that molecular expression of ClC-3 was indistinguishable between KCP-4 cells and parental cisplatin-sensitive KB-3-1 cells which endogenously exhibit high activity of ASOR anion channels. These results indicate that the ASOR anion channel is highly sensitive to temperature and independent of ClC-3.