Functional expression of carnitine/organic cation transporter OCTN1 in mouse brain neurons: Possible involvement in neuronal differentiation
Functional expression of carnitine/organic cation transporter OCTN1 in mouse brain neurons: Possible involvement in neuronal differentiation
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DOI：
10.1016/j.neuint.2012.08.004
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发表时间：
2012-12-01
影响因子：
4.2
通讯作者：
Kato, Yukio
中科院分区：
文献类型：
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作者：
Nakamichi, Noritaka;Taguchi, Takayuki;Kato, Yukio
本研究的目的是阐明肉碱/有机阳离子转运体OCTN1/SLC22A4在脑神经元中的功能表达和生理作用，该转运体在体内接受天然存在的抗氧化剂麦角硫因（ERGO）作为底物。在脑室内给药后，octn1（-/-）小鼠的几个脑区[H-3]ERGO的分布远低于野生型小鼠，而细胞外标记物[C-14]甘露醇在两株小鼠中的分布相似。野生型小鼠的[H-3]ERGO分布与食物摄入的ERGO量和各脑区OCTN1 mRNA水平有良好的相关性。免疫组织化学分析显示，OCTN1与神经元细胞标记物微管相关蛋白2 （MAP2）和β iii -微管蛋白分别在小鼠脑和原代培养的皮层神经元中共定位。此外，培养的皮质神经元表现出时间依赖性和饱和摄取[H-3]ERGO。这些结果表明OCTN1在脑神经元中具有功能性表达。将ERGO与血清同时添加到皮质神经元培养基中，可减弱MAP2、β iii -微管蛋白和突触形成标志物突触素I的mRNA和蛋白表达，并诱导维持未分化神经干细胞特性所需的性别决定区Y-box 2 （Sox2）的mRNA和蛋白表达。在神经元模型Neuro2a细胞中，siRNA敲除OCTN1降低了[H-3]ERGO的摄取，同时氧化应激标志物HO-1和Sox2上调，神经突生长标志物GAP43下调。有趣的是，siRNA敲低减少了显示长神经突的分化神经2a细胞的数量，但增加了细胞总数。因此，OCTN1参与细胞分化，但抑制其增殖，可能通过调节细胞氧化应激。这是OCTN1在大脑发育所需的神经元分化和增殖中发挥作用的第一个证据。爱思唯尔有限公司版权所有版权所有。
The aim of the present study is to clarify the functional expression and physiological role in brain neurons of carnitine/organic cation transporter OCTN1/SLC22A4, which accepts the naturally occurring antioxidant ergothioneine (ERGO) as a substrate in vivo. After intracerebroventricular administration, the distribution of [H-3]ERGO in several brain regions of octn1(-/-) mice was much lower than that in wild-type mice, whereas extracellular marker [C-14]mannitol exhibited similar distribution in the two strains. The [H-3]ERGO distribution in wild-type mice was well correlated with the amount of ERGO derived from food intake and the OCTN1 mRNA level in each brain region. Immunohistochemical analysis revealed colocalization of OCTN1 with neuronal cell markers microtubule-associated protein 2 (MAP2) and beta III-tubulin in mouse brain and primary cultured cortical neurons, respectively. Moreover, cultured cortical neurons exhibited time-dependent and saturable uptake of [H-3]ERGO. These results demonstrate that OCTN1 is functionally expressed in brain neurons. The addition of ERGO simultaneously with serum to culture medium of cortical neurons attenuated mRNA and protein expressions of MAP2, beta III-tubulin and synapse formation marker synapsin I, and induced those of sex determining region Y-box 2 (Sox2), which is required to maintain the properties of undifferentiated neural stem cells. In neuronal model Neuro2a cells, knock-down of OCTN1 by siRNA reduced the uptake of [H-3]ERGO with concomitant up-regulation of oxidative stress marker HO-1 and Sox2, and down-regulation of neurite outgrowth marker GAP43. Interestingly, the siRNA knockdown decreased the number of differentiated Neuro2a cells showing long neurites, but increased the total number of cells. Thus, OCTN1 is involved in cellular differentiation, but inhibits their proliferation, possibly via the regulation of cellular oxidative stress. This is the first evidence that OCTN1 plays a role in neuronal differentiation and proliferation, which are required for brain development. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.