title: Functional expression of choline transporter like-protein 1 (CTL1) and CTL2 in human brain microvascular endothelial cells.
abstract: In this study, we examined the molecular and functional characterization of choline transporter in human brain microvascular endothelial cells (hBMECs). Choline uptake into hBMECs was a saturable process that was mediated by a Na(+)-independent, membrane potential and pH-dependent transport system. The cells have two different [(3)H]choline transport systems with Km values of 35.0 ± 4.9 μM and 54.1 ± 8.1 μM, respectively. Choline uptake was inhibited by choline, acetylcholine (ACh) and the choline analog hemicholinium-3 (HC-3). Various organic cations also interacted with the choline transport system. Choline transporter-like protein 1 (CTL1) and CTL2 mRNA were highly expressed, while mRNA for high-affinity choline transporter 1 (CHT1) and organic cation transporters (OCTs) were not expressed in hBMECs. CTL1 and CTL2 proteins were localized to brain microvascular endothelial cells in human brain cortical sections. Both CTL1 and CTL2 proteins were expressed on the plasma membrane and mitochondria. CTL1 and CTL2 proteins are mainly expressed in plasma membrane and mitochondria, respectively. We conclude that choline is mainly transported via an intermediate-affinity choline transport system, CTL1 and CTL2, in hBMECs. These transporters are responsible for the uptake of extracellular choline and organic cations. CTL2 participate in choline transport mainly in mitochondria, and may be the major site for the control of choline oxidation.
authors.affiliation: Department of Psychiatry, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Beniko
authors.initials: B
authors.lastname: Iwao
authors.affiliation: Department of Anesthesiology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Yara
authors.affiliation: Department of Anesthesiology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Hara
authors.affiliation: Institute of Medical Science, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
authors.forename: Yuiko
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Department of Molecular Preventive Medicine, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yamanaka
authors.affiliation: Department of Translational Pathology, Hokkaido University, Graduate School of Medicine, N15 W7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishihara
authors.affiliation: Department of Psychiatry, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Institute of Medical Science, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan; Department of Molecular Preventive Medicine, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. Electronic address: inazu@tokyo-med.ac.jp.
authors.forename: Masato
authors.initials: M
authors.lastname: Inazu
mesh_terms: D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001921:Brain / Q000098:blood supply* / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D055806:Microvessels / Q000166:cytology / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D012964:Sodium / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; C510732:SLC44A1 protein, human; C484524:SLC44A2 protein, human; D012964:Sodium; D002794:Choline
keywords: Blood-brain barrier; Brain microvascular endothelial cells; Choline; Choline transporter-like protein; Transporter