Functions as a sodium-dependent amino acid transporter. Mediates the saturable, pH-sensitive and electrogenic cotransport of glutamine and sodium ions with a stoichiometry of 1:1. May also transport small zwitterionic and aliphatic amino acids with a lower affinity. May supply glutamatergic and GABAergic neurons with glutamine which is required for the synthesis of the neurotransmitters glutamate and GABA. Inhibited by lithium, potassium, choline ions, N-methyl-D-glucamine and 2-methylamino-isobutyric acid (MeAIB). Decrease in pH from 8.0 to 7.0 results in decreased affinity for L-glutamine. Restricted to the somatodendritic compartment of neurons. Found in the cellular processes of neurons in the developing brain. Specifically expressed in brain and retina (at protein level). Also detected in spleen, small intestine and lung. Up-regulated by BDNF. Belongs to the amino acid/polyamine transporter 2 family.