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.