Choline/H+ antiporter (PubMed:19357133, PubMed:23651124, PubMed:31855247, PubMed:33789160). Also acts as a high-affinity ethanolamine/H+ antiporter, regulating the supply of extracellular ethanolamine (Etn) for the CDP-Etn pathway, redistribute intracellular Etn and balance the CDP-Cho and CDP-Etn arms of the Kennedy pathway (PubMed:33789160). Involved in membrane synthesis and myelin production (PubMed:31855247).