LRRC8A-containing chloride channel is crucial for cell volume recovery and survival under hypertonic conditions

Regulation of cell volume is essential for tissue homeostasis and cell viability. In response to hypertonic stress, cells need rapid electrolyte influx to compensate water loss and to prevent cell death in a process known as regulatory volume increase (RVI). However, the molecular component able to trigger such a process was unknown to date. Using a genome-wide CRISPR/Cas9 screen, we identified LRRC8A, which encodes a chloride channel subunit, as the gene most associated with cell survival under hypertonic conditions. Hypertonicity activates the p38 stress-activated protein kinase pathway and its downstream MSK1 kinase, which phosphorylates and activates LRRC8A. LRRC8A-mediated Cl- efflux facilitates activation of the with-no-lysine (WNK) kinase pathway, which in turn, promotes electrolyte influx via Na+/K+/2Cl- cotransporter (NKCC) and RVI under hypertonic stress. LRRC8A-S217A mutation impairs channel activation by MSK1, resulting in reduced RVI and cell survival. In summary, LRRC8A is key to bidirectional osmotic stress responses and cell survival under hypertonic conditions.This work was supported by grants from the Ministry of Science, Innovation, and Universities (PGC2018-094136-B-I00 to F.P.; BFU2017-85152-P and Fondo Europeo de Desarrollo Regional [FEDER] to E.d.N.; RTI2018-099718-B-I00 and FEDER to M.A.V.), the Catalan Government (2017 SGR 799), the Fundación Botín, and the Banco Santander through its Santander Universities Global Division to F.P. We gratefully acknowledge institutional funding from the Ministry of Science, Innovation and Universities through the Centres of Excellence Severo Ochoa Award and from the Centres de Recerca de Catalunya (CERCA) Programme of the Catalan Government and the Unidad de Excelencia María de Maeztu, funded by the Agencia Estatal de Investigación (AEI) (CEX2018-000792-M). F.P. and E.d.N. are recipients of an Institució Catalana de Recerca i Estudis Avançats (ICREA) Acadèmia award (Generalitat de Catalunya)