Anoctamin 6 is an essential component of the outwardly rectifying chloride channel

Abstract

Outwardly rectifying chloride channels (ORCC, ICOR) of intermediate single-channel conductance of around 50 pS, are ubiquitously expressed, but have remained a mystery since their description more than 25 y ago. These channels have been shown to be activated on membrane excision and depolarization of the membrane voltage and by cAMP in the presence of the cystic fibrosis transmembrane conductance regulator. We show that anoctamin 6 (Ano6), a member of the recently identified family of putative Cl − channels, is the crucial component of ORCC single-channel and whole-cell currents in airway epithelial cells and Jurkat T lymphocytes. Cystic fibrosis transmembrane conductance regulator augmented ORCC produced by Ano6 in A549 airway epithelial cells. Ano6 is activated during membrane depolarization or apoptosis of Jurkat T lymphocytes and epithelial cells, and is inhibited by 5-nitro-2-(3-phenylpropylamino) benzoic acid, 4,4′-diisothio-cyanostilbene-2,2′-disulfonic acid, or AO1. Ano6 belongs to the basic equipment of any cell type, including colonic surface epithelial cells. It forms the essential component of ORCC and seems to have a role for cell shrinkage and programmed cell death.

Functional Swapping between Transmembrane Proteins TMEM16A and TMEM16F

“…Several groups, including ours, reported that TMEM16F has little or no Ca 2ϩ -dependent Cl Ϫ channel activity (7,10,29), whereas Yang et al (11) showed that it functions as a cation channel. On the other hand, other reports have claimed that it works as a Cl Ϫ channel in dendritic cells (30), contributes to the outward rectifying Cl Ϫ current for cell shrinkage during apoptosis (31), and functions as a volume-sensitive outwardly rectifying anion channel (32). Finally, Shimizu et al (33) recently reported that TMEM16F functions as a Ca 2ϩ -dependent Cl Ϫ channel at high intracellular Ca 2ϩ concentrations but that it does not support volume-sensitive outwardly rectifying currents activated by osmotic swelling or apoptotic stimulation.…”

Targeted Identification of Sialoglycoproteins in Hypoxic Endothelial Cells and Validation in Zebrafish Reveal Roles for Proteins in Angiogenesis

“…TMEM16F is a calcium-activated chloride channel expressed on the surface of platelets that is involved in the Ca 2ϩ -dependent scrambling of phospholipids (38). The protein is a ubiquitous component of outwardly rectifying chloride channels of intermediate single channel conductance expressed in many cell types, including epithelial cells and T lymphocytes, where it could play a role in cell shrinkage and programmed cell death (39). Taken together the zebrafish experiments indicate that TMEM16F is probably essential for zebrafish development and specifically for ISVs and DLAV in angiogenesis.…”

Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

“…118,152,153 siRNA K D of ANO6 reduces cisplatin induced Caspase 3 activation (apoptosis) in ELA cells (Fig. 15) and staurosporine induced cell death in lung epithelial cells (A549 151 ). On the other hand, Okada and coworkers found that ANO6 K D has no effect on staurosporine induced AVD.…”

“…78 VRAC is known to play an important role in this process but also ANO proteins appear to play a role in AVD/apoptotic cell death in several cell types investigated. 45,150,151 The amplicon 11q13 contains the Ano1 gene as well as well as a Fas-Associated protein with Death Domain (FADD) gene, i.e., a gene associated with apoptosis, suggesting a coupling between the regulation of ANO1 and cell death. Not much is published about ANO1 and apoptosis.…”