Functions as a sodium and chloride-dependent neutral amino acid transporter in kidneys (PubMed:26240152, PubMed:19478081). Required CLTRN for cell surface expression and for its amino acid transporter activity (PubMed:26240152). Interacts with CLTRN; this interaction regulates the trafficking of SLC6A18 to the cell membrane and its activity. In kidneys localizes to the apical membrane in distal segments of the proximal tubule. Expressed predominantly in kidney. Animals lacking this protein exhibit no gross abnormalities and grow to adulthood, although they do exhibit hypertension. The elevated blood pressure appears to be attributable to a decreased level of renal glycine. High-affinity renal reabsorption of glycine is eliminated and intrarenal glycine concentration is reduced. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A18 subfamily. Human SLC6A18 has been shown to be an inactive protein.