Required for the uptake of creatine. Plays an important role in supplying creatine to the brain via the blood-brain barrier (By similarity). Expressed in brain, cerebellum, spinal cord, to a lesser extent, heart, but only very low expression in lung, kidney, and muscle. Belongs to the sodium:neurotransmitter symporter (SNF) (TC 2.A.22) family. SLC6A8 subfamily. Was originally thought to be a choline transporter.