SWELL1, a Plasma Membrane Protein, Is an Essential Component of Volume-Regulated Anion Channel

Abstract

Summary Maintenance of a constant cell volume in response to extracellular or intracellular osmotic changes is critical for cellular homeostasis. Activation of a ubiquitous volume-regulated anion channel (VRAC) plays a key role in this process; however, its molecular identity in vertebrates remains unknown. Here, we used a cell-based fluorescence assay and performed a genome-wide RNAi screen to find components of VRAC. We identified SWELL1 (LRRC8A), a member of a four-transmembrane protein family with unknown function, as essential for hypotonicity-induced iodide influx. SWELL1 is localized to the plasma membrane, and its knockdown dramatically reduces endogenous VRAC currents and regulatory cell volume decrease in various cell types. Furthermore, point mutations in SWELL1 cause a significant change in VRAC anion selectivity, demonstrating that SWELL1 is an essential VRAC component. These findings enable further molecular characterization of the VRAC channel complex and genetic studies for understanding the function of VRAC in normal physiology and disease.

Megalencephalic leukoencephalopathy with cysts: the Glialcam‐null mouse model

“…Notably, however we found no evidence for delayed astrocyte maturation or astrogliosis in both Mlc1 ‐null18 and Glialcam ‐null mice (not shown). LRRC8A has recently been identified as an essential component of the mammalian VRAC 35, 36. We found no differences in LRRC8A expression and subcellular localization between wild‐type, Glialcam ‐null and Mlc1 ‐null mice, which does not exclude a functional interaction between the related proteins.…”

“…We extended the immunohistochemical and immuno‐EM analysis to expression of the caveolar lipid raft protein caveolin‐1 and the recently identified VRAC channel component LRRC8A in wild‐type, Glialcam ‐null and Mlc1 ‐null mice 18, 35, 36. We found no differences between mutant and control animals (Fig.…”

Specific and essential but not sufficient roles of LRRC8A in the activity of volume-sensitive outwardly rectifying anion channel (VSOR)

“…These results indicate that LRRC8A is a key component for VSOR in murine cells, as is the case in human cells. 13,14,20 LRRC8A is not involved in current generation of other distinct types of anion channels…”

“…[6][7][8][9][10][11][12] In 2014, 2 research groups independently reported that the leucine-rich repeat containing 8A (LRRC8A), which has 4 transmembrane domains and a leucine-rich repeat (LRR) domain at the C-terminus, is a core factor of VSOR in human cells. 13,14 They reported in common that knockdown of LRRC8A diminished endogenous VSOR currents in human cells, and such reduced currents could be rescued by introduction of exogenous LRRC8A, but overexpression of LRRC8A alone in normal cells paradoxically reduced endogenous VSOR currents. 13,14 Also, VSOR was shown to be a heteromeric channel containing not only LRRC8A but also other LRRC8 family members.…”

“…13,14 They reported in common that knockdown of LRRC8A diminished endogenous VSOR currents in human cells, and such reduced currents could be rescued by introduction of exogenous LRRC8A, but overexpression of LRRC8A alone in normal cells paradoxically reduced endogenous VSOR currents. 13,14 Also, VSOR was shown to be a heteromeric channel containing not only LRRC8A but also other LRRC8 family members. 13 Indeed, a multimeric complex mainly of these members with a molecular mass of »800 kDa was found to be sufficient to form the osmo-and ionic strength-sensitive anion channels in lipid bilayers.…”