Choline transporter that plays a role in the choline-acetylcholine system and is required to the efferent innervation of hair cells in the olivocochlear bundle for the maintenance of physiological function of outer hair cells and the protection of hair cells from acoustic injury (By similarity) (PubMed:23651124, PubMed:28013291). Also described as a thiamine pyrophosphate transporter in colon, may mediate the absorption of microbiota-generated thiamine pyrophosphate and contribute to host thiamine (vitamin B1) homeostasis (PubMed:24379411). Has also thiamine pyrophosphate transporter activity. Highly expressed in colon, also detected in prostate, trachea and lung (PubMed:24379411). Isoform 3 is also expressed in colon but a lower levels (PubMed:24379411). N-glycosylated; N-glycosylation of Asn-69, Asn-155 and Asn-393 is required for a proper thiamine pyrophosphate uptake. An interstitial deletion causing the fusion of exon 10 of CTL4 with the 3'-UTR of NEU has been detected in two patients affected by sialidosis. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CTL (choline transporter-like) family.