Department of Neuroscience & Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.
Epilepsia. 2009 Jul;50(7):1717-28. doi: 10.1111/j.1528-1167.2009.02054.x. Epub 2009 Apr 6.
Vesicular glutamate transporters (VGLUTs) are responsible for loading synaptic vesicles with glutamate, determining the phenotype of glutamatergic neurons, and have been implicated in the regulation of quantal size and presynaptic plasticity. We analyzed VGLUT subtype expression in normal human hippocampus and tested the hypothesis that alterations in VGLUT expression may contribute to long-term changes in glutamatergic transmission reported in patients with temporal lobe epilepsy (TLE).
VGLUT immunohistochemistry, immunofluorescence, in situ hybridization, Western blotting, and quantitative polymerase chain reaction (qPCR) were performed on biopsies from TLE patients without (non-HS) and with hippocampal sclerosis (HS) and compared to autopsy controls and rat hippocampus. VGLUT1 expression was compared with synaptophysin, neuropeptide Y (NPY), and Timm's staining.
VGLUT1 was the predominant VGLUT in human hippocampus and appeared to be localized to presynaptic glutamatergic terminals. In non-HS hippocampi, VGLUT1 protein levels were increased compared to control and HS hippocampi in all subfields. In HS hippocampi VGLUT1 expression was decreased in subfields with severe neuronal loss, but strongly up-regulated in the dentate gyrus, characterized by mossy fiber sprouting.
VGLUT1 is used as marker for glutamatergic synapses in the human hippocampus. In HS hippocampi VGLUT1 up-regulation in the dentate gyrus probably marks new glutamatergic synapses formed by mossy fiber sprouting. Our data indicate that non-HS patients have an increased capacity to store glutamate in vesicles, most likely due to an increase in translational processes or upregulation of VGLUT1 in synapses from afferent neurons outside the hippocampus. This up-regulation may increase glutamatergic transmission, and thus contribute to increased extracellular glutamate levels and hyperexcitability.
囊泡谷氨酸转运体（VGLUTs）负责将谷氨酸装载到突触小泡中，决定谷氨酸能神经元的表型，并与量子大小和突触前可塑性的调节有关。我们分析了正常人类海马体中的 VGLUT 亚型表达，并测试了这样一种假设，即 VGLUT 表达的改变可能导致颞叶癫痫（TLE）患者报告的谷氨酸能传递的长期变化。
对 TLE 患者无（非 HS）和有海马硬化（HS）的活检进行 VGLUT 免疫组织化学、免疫荧光、原位杂交、Western blot 和定量聚合酶链反应（qPCR）检测，并与尸检对照和大鼠海马体进行比较。VGLUT1 表达与突触小体蛋白、神经肽 Y（NPY）和 Timm 染色进行比较。
VGLUT1 是人类海马体中主要的 VGLUT，似乎定位于突触前谷氨酸能末梢。在非 HS 海马体中，与对照和 HS 海马体相比，所有亚区的 VGLUT1 蛋白水平均升高。在 HS 海马体中，VGLUT1 表达在神经元丢失严重的亚区减少，但在齿状回强烈上调，特征是苔藓纤维发芽。
VGLUT1 被用作人类海马体中谷氨酸能突触的标志物。在 HS 海马体中，齿状回 VGLUT1 的上调可能标志着由苔藓纤维发芽形成的新的谷氨酸能突触。我们的数据表明，非 HS 患者可能增加了囊泡中谷氨酸的储存能力，这很可能是由于翻译过程增加或来自海马体以外的传入神经元突触中 VGLUT1 的上调。这种上调可能会增加谷氨酸能传递，从而导致细胞外谷氨酸水平升高和过度兴奋。
