Sialin

Sialin is a protein that in humans is encoded by the SLC17A5 gene. It is a transmembrane protein primarily located in the lysosomal membrane. Sialin is involved in the transport of sialic acid, a sugar molecule, across the lysosomal membrane. Mutations in the SLC17A5 gene can lead to a rare lysosomal storage disease known as Salla disease or Infantile Sialic Acid Storage Disease (ISSD).

Structure

Sialin is a 495 amino acid protein with 12 transmembrane domains. The protein is primarily located in the lysosomal membrane, where it functions as a sialic acid transporter. The structure of sialin is similar to that of other members of the solute carrier family 17, which includes various phosphate and organic anion transporters.

Function

The primary function of sialin is to transport sialic acid, a sugar molecule, from the lysosome to the cytosol. Sialic acid is a key component of glycoproteins and glycolipids, which are essential for various cellular functions including cell adhesion and signal transduction. By transporting sialic acid out of the lysosome, sialin plays a crucial role in the metabolism of these important biomolecules.

Clinical significance

Mutations in the SLC17A5 gene that encodes sialin can lead to a rare lysosomal storage disease known as Salla disease or Infantile Sialic Acid Storage Disease (ISSD). These diseases are characterized by the accumulation of free sialic acid in the lysosome, leading to various neurological symptoms including developmental delay, hypotonia, and seizures. The severity of symptoms can vary widely, with Salla disease generally being less severe than ISSD.

See also

• Solute carrier family
• Salla disease
• Infantile Sialic Acid Storage Disease
• Lysosomal storage disease