The Mechanism of Calcium-Activated Chloride ANO6 Channel Inhibition by CaCCinh-A01

Abstract

Proteins of the anoctamine family (ANO) form calcium-activated chloride channels (CaCC) and phospholilpid scramblases. The ANO6 (TMEM16F) protein, which combines the functions of a calcium-dependent scramblase and those of an ion channel, is considered as a molecular target for the treatment of blood clotting disorders, COVID-19-associated pneumonia, neurodegenerative diseases, and other pathologies. CaCCinh-A01, which is a channel blocker of the ANO family, is studied as a potential pharmacological drug. Previously, the effect of this inhibitor was studied using methods representing the integral ion current through the membrane, which does not allow the properties of single channels to be distinguished. Therefore, it remains unknown which characteristics of single channels are sensitive to the blocker: channel open probability, the current amplitude, or the dwelling time of the channel open state. By registration of single ANO6 channels in HEK293 cells, we showed that the action of the inhibitor is due to a decrease in both the current amplitude and the open state dwelling time of single ANO6 channels, which, in turn, leads to a decrease in their open state probability. Thus, we have characterized the mechanism of current reduction through ANO6 channels by the inhibitor CaCCinh A01.