Functions as a sodium-dependent amino acid transporter which countertransport protons. Mediates the saturable, pH-sensitive, and electrogenic cotransport of several neutral amino acids including glycine, asparagine, alanine, serine, glutamine and histidine with sodium (By similarity). Not inhibited by lithium. Down-regulated in Dgn3 deficient mice. Belongs to the amino acid/polyamine transporter 2 family.