title: Functional expression of choline transporter-like protein 1 (CTL1) in human neuroblastoma cells and its link to acetylcholine synthesis.
abstract: We examined the molecular and functional characterization of choline uptake into human neuroblastoma cell lines (SH-SY5Y: non-cholinergic and LA-N-2: cholinergic neuroblastoma), and the association between choline transport and acetylcholine (ACh) synthesis in these cells. Choline uptake was saturable and mediated by a single transport system. Removal of Na(+) from the uptake buffer strongly enhanced choline uptake. Choline uptake was inhibited by the choline analogue hemicholinium-3 (HC-3) and various organic cations, and was significantly decreased by acidification of the extracellular medium. The increase in choline uptake under Na(+)-free conditions was inhibited by a Na(+)/H(+) exchanger (NHE) inhibitor. Real-time PCR revealed that choline transporter-like protein 1 (CTL1), NHE1 and NHE5 mRNA are mainly expressed. Western blot and immunocytochemical analysis indicated that CTL1 protein was expressed in plasma membrane. ChAT mRNA was expressed at a much higher level in LA-N-2 cells than in SH-SY5Y cells. The conversion of choline to ACh was confirmed in both cells, and was enhanced in Na(+)-free conditions. These findings suggest that CTL1 is functionally expressed in both SH-SY5Y and LA-N-2 cells and is responsible for choline uptake that relies on a directed H(+) gradient as a driving force, and this transport functions in co-operation with NHE1 and NHE5. Furthermore, choline uptake through CTL1 is associated with ACh synthesis in cholinergic neuroblastoma cells.
authors.affiliation: Department of Pharmacology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yamada
authors.forename: Masato
authors.initials: M
authors.lastname: Inazu
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Tajima
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Matsumiya
mesh_terms: D000109:Acetylcholine / Q000096:biosynthesis*; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism*; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009924:Organ Culture Techniques; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015703:Antigens, CD; D027701:Organic Cation Transport Proteins; C510732:SLC44A1 protein, human; D000109:Acetylcholine