The sialic acid transporter is expressed on both lysosomes and synaptic vesicles, where it appears to allow export of sialic acid and accumulation of acidic amino acids, respectively [1], driven by proton gradients. In lysosomes, degradation of glycoproteins generates amino acids and sugar residues, which are metabolized further following export from the lysosome.

Loss-of-function mutations in sialin are associated with Salla disease (OMIM: 604369), an autosomal recessive neurodegenerative disorder associated with sialic acid storage disease [2].

1. Miyaji T, Omote H, Moriyama Y. (2011) Functional characterization of vesicular excitatory amino acid transport by human sialin. J Neurochem, 119 (1): 1-5. [PMID:21781115]

2. Verheijen FW, Verbeek E, Aula N, Beerens CE, Havelaar AC, Joosse M, Peltonen L, Aula P, Galjaard H, van der Spek PJ et al.. (1999) A new gene, encoding an anion transporter, is mutated in sialic acid storage diseases. Nat Genet, 23 (4): 462-5. [PMID:10581036]