A conserved mechanism of LRRC8 channel inhibition by two structurally distinct drugs.

Leucine Rich Repeat Containing 8 (LRRC8) anion channels are emerging therapeutic targets, but their pharmacology is poorly developed. We employed a structurally defined homomeric channel chimera (8C-8A(IL125)) and heteromeric LRRC8A/LRRC8C (8A/8C) channels to investigate the mechanism of action of two structurally distinct LRRC8 inhibitors: zafirlukast and pranlukast. Molecular dynamics simulations identified zafirlukast binding sites in 8C-8A(IL125) comprising the amino (N)-terminal domain (NTD) and inter-subunit fenestrae between transmembrane (TM) helices 1 and 2. Pranlukast also clusters in fenestrae albeit closer to the external pore. Patch clamp analysis revealed that mutations in NTD, TM1, and TM2 alter 8C-8A(IL125) and 8A/8C sensitivity to zafirlukast and pranlukast, suggesting a common mechanism. The association between voltage-dependent inactivation induced by mutations or low pH and inhibitor sensitivity suggests that drug inhibition involves disruption of protein-lipid interactions and destabilization of the pore. This may represent a common mechanism of LRRC8 channel inhibition by lipophilic drugs.