Iwao Beniko, Yara Miki, Hara Naomi, Kawai Yuiko, Yamanaka Tsuyoshi, Nishihara Hiroshi, Inoue Takeshi, Inazu Masato
Department of Psychiatry, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
Department of Anesthesiology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
Neurochem Int. 2016 Feb;93:40-50. doi: 10.1016/j.neuint.2015.12.011. Epub 2015 Dec 31.
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.
在本研究中，我们检测了人脑微血管内皮细胞（hBMECs）中胆碱转运体的分子和功能特征。胆碱摄入hBMECs是一个可饱和的过程，由一个不依赖Na⁺、依赖膜电位和pH的转运系统介导。这些细胞有两种不同的[³H]胆碱转运系统，其Km值分别为35.0±4.9μM和54.1±8.1μM。胆碱摄取受到胆碱、乙酰胆碱（ACh）和胆碱类似物半胱氨酸-3（HC-3）的抑制。各种有机阳离子也与胆碱转运系统相互作用。胆碱转运体样蛋白1（CTL1）和CTL2 mRNA高表达，而高亲和力胆碱转运体1（CHT1）和有机阳离子转运体（OCTs）的mRNA在hBMECs中不表达。CTL1和CTL2蛋白定位于人脑皮质切片中的脑微血管内皮细胞。CTL1和CTL2蛋白均表达于质膜和线粒体上。CTL1和CTL2蛋白分别主要表达于质膜和线粒体。我们得出结论，在hBMECs中，胆碱主要通过中等亲和力的胆碱转运系统CTL1和CTL2进行转运。这些转运体负责摄取细胞外胆碱和有机阳离子。CTL2主要在线粒体中参与胆碱转运，可能是胆碱氧化控制的主要位点。
