Subunit Dependent Regulation of LRRC8 Mediated VRAC Currents by Oxidation

Abstract

Volume-regulated anion channels (VRAC) are heteromers composed of the essential LRRC8A subunit and at least one among the LRRC8B-E subunits [1]. Reactive oxygen species (ROS) play physiological and pathophysiological roles and VRAC channels are known to be highly ROS sensitive. Using fluorescently tagged LRRC8 proteins that give rise to constitutive currents in Xenopus oocytes [2] we tested direct effects of oxidation on different subunit combinations of LRRC8 channels. 8A/8E heteromers were dramatically potentiated (more than 10-fold) by oxidation of intracellular cysteine residues by chloramine-T or tert-butyl hydroperoxide. Oxidation was not necessary for hypotonicity induced activation. In contrast, 8A/8C and 8A/8D heteromers were strongly inhibited by oxidation. In agreement with the non-inactivating current characteristic of VRAC in T lymphocytes that is a typical feature of the 8C subunit, we found that VRAC currents in Jurkat cells are inhibited by oxidation and that the 8E subunit is the least expressed in Jurkat cells. A reduction of VRAC during acute T cell activation associated with ROS production might be of physiological relevance in the immune response.