Solute carrier family 17 member 5 (Sialin) (SLC17A5)

Solute carrier family 17 member 5 (SLC17A5), commonly known as Sialin, is a lysosomal membrane protein that functions as a transporter for sialic acid and inorganic nitrate (UniProt: Q9NRA2). In lysosomes, it exports sialic acid to the cytosol, while in the plasma membrane of salivary gland acinar cells, it acts as an electrogenic H+/nitrate cotransporter (PubMed: 22267511). This transport is a critical step in the enterosalivary circulation of nitrate, where dietary nitrate is concentrated in saliva, reduced to nitrite by oral bacteria, and further converted to nitric oxide (NO) in the acidic environment of the stomach or through systemic nitrite reductases (PubMed: 25599331). This pathway serves as an important alternative source of NO, particularly under hypoxic conditions where the canonical L-arginine-NOS pathway is impaired. Mutations in the SLC17A5 gene lead to sialic acid storage diseases, such as Salla disease and infantile sialic acid storage disease (ISSD), characterized by neurodegeneration (PubMed: 10508514). From a therapeutic perspective, Sialin is a target for modulating NO bioavailability to treat cardiovascular conditions like hypertension and endothelial dysfunction through the administration of inorganic nitrate (PubMed: 25421027).

Other names

SialinSLC17A5ASTISSDSDSLDNitrate transporterMembrane glycoprotein HP59

Facilitates the active transport of inorganic nitrate into salivary glands as part of the enterosalivary circulation, providing a substrate for the production of nitric oxide via the nitrate-nitrite-NO pathway.