LRRC8A
Description
The LRRC8A (leucine rich repeat containing 8 VRAC subunit A) is a protein-coding gene located on chromosome 9.
Leucine-rich repeat-containing protein 8A is a protein that in humans is encoded by the LRRC8A gene. Researchers have found out that this protein, along with the other LRRC8 proteins LRRC8B, LRRC8C, LRRC8D, and LRRC8E, is a subunit of the heteromer protein volume-regulated anion channel (VRAC). VRACs are crucial to the regulation of cell size by transporting chloride ions and various organic osmolytes, such as taurine or glutamate, across the plasma membrane, and that is not the only function these channels have been linked to. While LRRC8A is one of many proteins that can be part of VRAC, it is the most important subunit for the channel’s ability to function. However, while we know it is necessary for VRAC function, other studies have found that it is not sufficient for the full range of usual VRAC activity. This is where the other LRRC8 proteins come in, as the different composition of these subunits affects the range of specificity for VRACs. The transmembrane portion of LRRC8 proteins are similar to those in Pannexins. LRRC8A alone can form a hexameric VRAC, for which the cyro-EM structure has been determined in its mice and human versions. In addition to its role in VRACs, the LRRC8 protein family is also associated with agammaglobulinemia-5.
Essential component of the volume-regulated anion channel (VRAC, also named VSOAC channel), an anion channel required to maintain a constant cell volume in response to extracellular or intracellular osmotic changes (PubMed:24725410, PubMed:29769723, PubMed:24790029, PubMed:26530471, PubMed:26824658, PubMed:28193731). The VRAC channel conducts iodide better than chloride and can also conduct organic osmolytes like taurine (PubMed:24725410, PubMed:30095067, PubMed:24790029, PubMed:26530471, PubMed:26824658, PubMed:28193731). Mediates efflux of amino acids, such as aspartate and glutamate, in response to osmotic stress (PubMed:28193731). LRRC8A and LRRC8D are required for the uptake of the drug cisplatin (PubMed:26530471). In complex with LRRC8C or LRRC8E, acts as a transporter of immunoreactive cyclic dinucleotide GMP-AMP (2'-3'-cGAMP), an immune messenger produced in response to DNA virus in the cytosol: mediates both import and export of 2'-3'-cGAMP, thereby promoting transfer of 2'-3'-cGAMP to bystander cells (PubMed:33171122). In contrast, complexes containing LRRC8D inhibit transport of 2'-3'-cGAMP (PubMed:33171122). Required for in vivo channel activity, together with at least one other family member (LRRC8B, LRRC8C, LRRC8D or LRRC8E); channel characteristics depend on the precise subunit composition (PubMed:24790029, PubMed:26824658, PubMed:28193731). Can form functional channels by itself (in vitro) (PubMed:26824658). Involved in B-cell development: required for the pro-B cell to pre-B cell transition (PubMed:14660746). Also required for T-cell development (By similarity). Required for myoblast differentiation: VRAC activity promotes membrane hyperpolarization and regulates insulin-stimulated glucose metabolism and oxygen consumption (By similarity). Also acts as a regulator of glucose-sensing in pancreatic beta cells: VRAC currents, generated in response to hypotonicity- or glucose-induced beta cell swelling, depolarize cells, thereby causing electrical excitation, leading to increase glucose sensitivity and insulin secretion (PubMed:29371604). Also plays a role in lysosome homeostasis by forming functional lysosomal VRAC channels in response to low cytoplasmic ionic strength condition: lysosomal VRAC channels are necessary for the formation of large lysosome-derived vacuoles, which store and then expel excess water to maintain cytosolic water homeostasis (PubMed:31270356, PubMed:33139539). {ECO:0000250|UniProtKB:Q80WG5, ECO:0000269|PubMed:14660746, ECO:0000269|PubMed:24725410, ECO:0000269|PubMed:24790029, ECO:0000269|PubMed:26530471, ECO:0000269|PubMed:26824658, ECO:0000269|PubMed:28193731, ECO:0000269|PubMed:29371604, ECO:0000269|PubMed:29769723, ECO:0000269|PubMed:30095067, ECO:0000269|PubMed:31270356, ECO:0000269|PubMed:33139539, ECO:0000269|PubMed:33171122}
LRRC8A is also known as AGM5, HsLRRC8A, LRRC8, SWELL1.
