División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City, México.
Dev Neurosci. 2010;32(4):321-8. doi: 10.1159/000321583. Epub 2010 Dec 14.
Taurine addition to cultured embryonic neural precursor cells (NPC) significantly increased cell proliferation [Hernández-Benítez et al., 2010]. The medium used for NPC growing and proliferation is a fetal serum-free medium, and therefore, NPC become taurine depleted. Addition of taurine to the cultured medium fully replenished the cell taurine pool, suggesting the functional expression of a taurine transporter (TauT) in these cells. In the present study, TauT in NPC was functionally characterized and its protein expression and the subcellular distribution of immunoreactivity were determined. ³H-taurine uptake in NPC could be separated into a non-saturable component and a Na(+)/Cl⁻-dependent, saturable component. The saturable component showed an apparent 2:1:1 Na(+)/Cl⁻/taurine stoichiometry, a V(max) of 0.39 ± 0.04 nmol/mg protein/min, and a K(m) of 21.7 ± 2.6 μM. TauT in NPC was strongly inhibited by hypotaurine and β-alanine (92 and 79%, respectively) and reduced (71%) by γ-aminobutyric acid. TauT protein is expressed in NPC as a single band of about 70 kDa. Essentially all (98.8%) of the neurosphere-forming cells were positive to TauT immunoreactivity. Immunolocalization visualized by confocal microscopy localized TauT predominantly at the cell membrane. TauT was also found at the cytosol and only occasionally at the nuclear membrane. This study represents the first characterization of TauT in NPC.
牛磺酸添加到培养的胚胎神经前体细胞（NPC）中可显著增加细胞增殖[Hernández-Benítez 等人，2010]。用于 NPC 生长和增殖的培养基是无胎牛血清培养基，因此 NPC 中牛磺酸被耗尽。向培养物中添加牛磺酸可完全补充细胞内的牛磺酸池，这表明这些细胞中功能性表达了牛磺酸转运体（TauT）。在本研究中，对 NPC 中的 TauT 进行了功能表征，并确定了其蛋白表达和免疫反应性的亚细胞分布。NPC 中的 ³H-牛磺酸摄取可分为非饱和成分和 Na(+)/Cl⁻依赖性饱和成分。饱和成分显示出明显的 2:1:1 Na(+)/Cl⁻/牛磺酸化学计量比、0.39±0.04 nmol/mg 蛋白/min 的 Vmax 和 21.7±2.6 μM 的 K(m)。NPC 中的 TauT 被低牛磺酸和 β-丙氨酸强烈抑制（分别为 92%和 79%），γ-氨基丁酸抑制 71%。TauT 蛋白在 NPC 中表达为约 70 kDa 的单一条带。基本上所有（98.8%）神经球形成细胞对 TauT 免疫反应性呈阳性。通过共聚焦显微镜观察到的免疫定位将 TauT 主要定位在细胞膜上。TauT 还存在于细胞质中，仅偶尔出现在核膜上。这项研究代表了 NPC 中 TauT 的首次特征描述。
