Functions as a sodium and chloride-dependent neutral amino acid transporter in kidneys. Requires CLTRN for surface expression and for its amino acid transporter activity. Interacts with CLTRN; this interaction regulates the trafficking of SLC6A18 to the cell membrane and its amino acid transporter activity. In kidneys localizes to the apical membrane in distal segments of the proximal tubule. Kidney-specific expression. By renal osmotic stress. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A18 subfamily.