Kaneko Takeshi, Fujiyama Fumino
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, 606-8501, Kyoto, Japan.
Neurosci Res. 2002 Apr;42(4):243-50. doi: 10.1016/s0168-0102(02)00009-3.
Two vesicular glutamate transporters (VGluTs) have been identified at the molecular level very recently and revealed to possess similar pharmacological characteristics for glutamate uptake. Vesicular glutamate transporter 1 (VGluT1), which was originally named brain-specific Na+-dependent inorganic phosphate cotransporter (BNPI), is mainly expressed in telencephalic regions, whereas vesicular glutamate transporter 2 (VGluT2), formerly referred to as differentiation-associated Na+-dependent inorganic phosphate cotransporter (DNPI), is produced principally in diencephalic and lower brainstem regions. Since no other proteins show as high molecular similarity to VGluT1 or VGluT2 as the two transporters exhibit, it is likely that the mammalian central nervous system use only two gene products for vesicular glutamate uptake. Immunoelectron-microscopic analysis has revealed that the two VGluTs are located on synaptic vesicles in axon terminals making an asymmetric type of synapses, supporting that they serve as vesicular transporters in excitatory terminals. Furthermore, mRNA and immunoreactivity for VGluTs are distributed largely in a complementary fashion to distinct populations of excitatory neurons; for example, in the cerebral cortex, thalamocortical axon terminals use VGluT2, whereas excitatory axon terminals of corticocortical or intracortical fibers seem to apply VGluT1 for glutamate uptake. This complementary distribution might suggest that the two VGluTs have an as yet unknown difference in functions.
最近在分子水平上鉴定出了两种囊泡谷氨酸转运体（VGluTs），并发现它们在摄取谷氨酸方面具有相似的药理学特性。囊泡谷氨酸转运体1（VGluT1）最初被命名为脑特异性钠依赖性无机磷酸共转运体（BNPI），主要表达于端脑区域，而囊泡谷氨酸转运体2（VGluT2），以前称为分化相关钠依赖性无机磷酸共转运体（DNPI），主要在间脑和低位脑干区域产生。由于没有其他蛋白质与这两种转运体表现出与VGluT1或VGluT2一样高的分子相似性，哺乳动物中枢神经系统很可能仅使用两种基因产物进行囊泡谷氨酸摄取。免疫电子显微镜分析表明，这两种VGluTs位于轴突终末的突触小泡上，形成不对称型突触，支持它们在兴奋性终末作为囊泡转运体发挥作用。此外，VGluTs的mRNA和免疫反应性在很大程度上以互补的方式分布于不同群体的兴奋性神经元；例如，在大脑皮层，丘脑皮质轴突终末使用VGluT2，而皮质皮质或皮质内纤维的兴奋性轴突终末似乎使用VGluT1摄取谷氨酸。这种互补分布可能表明这两种VGluTs在功能上存在尚未知晓的差异。
