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 potassium, choline ions and 2-methylamino-isobutyric acid (MeAIB) (By similarity). Inhibited by lithium and N-methyl-D-glucamine. Restricted to the somatodendritic compartment of neurons. Found in the cellular processes of neurons in the developing brain (By similarity). Expressed in the cerebral cortex by pyramidal and GABAergic neurons, astrocytes and other non-neuronal cells (at protein level). Expressed in placenta, heart, lung, skeletal muscle, spleen, stomach and testis. Down-regulated by bacterial lipopolysaccharides (LPS) in glial cells. Down-regulated upon hypoxia. Belongs to the amino acid/polyamine transporter 2 family.