Leucine-rich repeat-containing 8B protein is associated with the endoplasmic reticulum Ca²⁺+ leak in HEK293 cells

Leucine-rich repeat-containing 8 (LRRC8) proteins have been proposed to evolutionarily originate from the combination of the channel protein pannexin, and a leucine-rich repeat (LRR) domain. Five paralogs of LRRC8, namely LRRC8A, LRRC8B, LRRC8C, LRRC8D and LRRC8E have been reported. LRRC8A has been shown to be instrumental in cell swelling. Here, we identify LRRC8B as a key player in the cellular Ca2+ signaling network. Overexpression of human LRRC8B in HEK293 cells reduced the Ca2++ level in the endoplasmic reticulum (ER). LRRC8Boverexpressing cells exhibited a lesser release of Ca2++ from the ER in response to ATP, carbachol and intracellular administration of inositol (1,4,5)-trisphosphate (IP3). LRRC8B-knockdown cells showed a slower depletion of the ER Ca2++ stores when sarco-endoplasmic reticulum Ca2++-ATPasewas blockedwith thapsigargin (TG), while overexpression of LRRC8B had the opposite effect. LRRC8B-overexpressing cells exhibited a higher level of store-operated Ca2++ entry following storedepletion by TG. Collectively, LRRC8B participates in intracellular Ca2++ homeostasis by acting as a leak channel in the ER. This study gives a fundamental understanding of the role of a novel protein in the elemental cellular process of ER Ca2++ leak and expands the known roles for LRRC8 proteins.