人GLUD1和GLUD2谷氨酸脱氢酶的细胞和亚细胞表达的频谱拓宽表明新功能。,Neurochemical Research

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人GLUD1和GLUD2谷氨酸脱氢酶的细胞和亚细胞表达的频谱拓宽表明新功能。
Neurochemical Research ( IF 3.7 ) Pub Date : 2016-07-16 , DOI: 10.1007/s11064-016-1986-x
Cleanthe Spanaki ₁ , Dimitra Kotzamani ₁ , Andreas Plaitakis _{1,

2}

Affiliation

哺乳动物谷氨酸脱氢酶1（GDH1）（EC 1.4.1.3）是一种线粒体酶，催化谷氨酸可逆氧化脱氨为α-酮戊二酸和氨，同时将NAD +和/或NADP +还原为NADH和/或NADPH。它把氨基酸与碳水化合物的代谢联系在一起，从而促进了克雷布斯周期异常，能量产生，氨气处理和氧化还原稳态。尽管GDH1是几十年前研究的首批主要代谢酶之一，但其在细胞生物学中的作用仍不完全清楚。然而，人们对新型GDH2同工酶的兴趣日益浓厚，该酶通过在灵长类动物中复制而出现，并随着前额叶人类皮层的扩张而经历了快速的进化选择。还，目前，GDH1和GDH2的抗动脉粥样硬化功能受到了高度重视，因为它与神经胶质瘤和其他瘤形成的生物学有关。在这里，我们使用了特异于人GDH1（hGDH1）和人GDH2（hGDH2）的抗体来研究这些同工酶在人体组织中的表达。结果显示，hGDH1和hGDH2均在人脑，肾脏，睾丸和类固醇生成器官中表达。但是，出现了不同的hGDH1和hGDH2表达模式。因此，尽管人类睾丸的支持细胞对hGDH2呈强阳性，但对hGDH1却呈阴性。相反，hGDH1在人肝中显示出非常高的表达水平，但肝细胞实际上不含hGDH2。在人类肾上腺中，两种hGDH均在产生类固醇的细胞中密集表达，具有与参与类固醇合成的胆固醇侧链裂解系统相匹配的hGDH2表达模式。类似地，在人类卵巢和胎盘中，hGDH1和hGDH2均在产生雌激素的细胞中密集表达。此外，hGDH1是一种管家酶，也可以在缺乏内分泌功能的细胞中表达。对于人脑，共聚焦显微镜使用免疫荧光（IF）进行的皮质切片研究表明，hGDH1和hGDH2均在类似于线粒体的粗糙结构内的灰质和白质星形胶质细胞质中表达。另外，hGDH1定位于星形胶质细胞亚群以及绝大多数少突胶质细胞及其前体的核膜上。值得注意的是，在人类皮层神经元中检测到了hGDH2特异性染色，出现了不同的表达方式。在大型皮质神经元（有些具有锥体形态）中观察到的一种模式是类似于线粒体的hGDH2特异性标记的细胞质结构。它们分布在细胞体轴突中或细胞表面上，紧邻包围谷氨酸能突触的星形细胞末端。在具有圆形致密核的小皮质神经元中观察到另一种模式，其中在核膜中发现了hGDH2特异性染色。这些观察结果及其功能含义的详细说明，提示不同细胞使用GDH通量来发挥其某些独特功能，如下所示。是类似于线粒体的细胞质结构的hGDH2特异性标记。它们分布在细胞体轴突中或细胞表面上，紧邻包围谷氨酸能突触的星形细胞末端。在具有圆形致密核的小皮质神经元中观察到另一种模式，其中在核膜中发现了hGDH2特异性染色。这些观察结果及其功能含义的详细说明，提示不同细胞使用GDH通量来发挥其某些独特功能，如下所示。是类似于线粒体的细胞质结构的hGDH2特异性标记。它们分布在细胞体轴突中或细胞表面上，紧邻包围谷氨酸能突触的星形细胞末端。在具有圆形致密核的小皮质神经元中观察到另一种模式，其中在核膜中发现了hGDH2特异性染色。这些观察结果及其功能含义的详细说明，提示不同细胞使用GDH通量来发挥其某些独特功能，如下所示。在具有圆形致密核的小皮质神经元中观察到另一种模式，其中在核膜中发现了hGDH2特异性染色。这些观察结果及其功能含义的详细说明，提示不同细胞使用GDH通量来发挥其某些独特功能，如下所示。在具有圆形致密核的小皮质神经元中观察到另一种模式，其中在核膜中发现了hGDH2特异性染色。这些观察结果及其功能含义的详细说明，提示不同细胞使用GDH通量来发挥其某些独特功能，如下所示。

"点击查看英文标题和摘要"

Widening Spectrum of Cellular and Subcellular Expression of Human GLUD1 and GLUD2 Glutamate Dehydrogenases Suggests Novel Functions.

Mammalian glutamate dehydrogenase1 (GDH1) (E.C. 1.4.1.3) is a mitochondrial enzyme that catalyzes the reversible oxidative deamination of glutamate to α-ketoglutarate and ammonia while reducing NAD+ and/or NADP+ to NADH and/or NADPH. It links amino acid with carbohydrate metabolism, contributing to Krebs cycle anaplerosis, energy production, ammonia handling and redox homeostasis. Although GDH1 was one of the first major metabolic enzymes to be studied decades ago, its role in cell biology is still incompletely understood. There is however growing interest in a novel GDH2 isoenzyme that emerged via duplication in primates and underwent rapid evolutionary selection concomitant with prefrontal human cortex expansion. Also, the anaplerotic function of GDH1 and GDH2 is currently under sharp focus as this relates to the biology of glial tumors and other neoplasias. Here we used antibodies specific for human GDH1 (hGDH1) and human GDH2 (hGDH2) to study the expression of these isoenzymes in human tissues. Results revealed that both hGDH1 and hGDH2 are expressed in human brain, kidney, testis and steroidogenic organs. However, distinct hGDH1 and hGDH2 expression patterns emerged. Thus, while the Sertoli cells of human testis were strongly positive for hGDH2, they were negative for hGDH1. Conversely, hGDH1 showed very high levels of expression in human liver, but hepatocytes were virtually devoid of hGDH2. In human adrenals, both hGDHs were densely expressed in steroid-producing cells, with hGDH2 expression pattern matching that of the cholesterol side chain cleavage system involved in steroid synthesis. Similarly in human ovaries and placenta, both hGDH1 and hGDH2 were densely expressed in estrogen producing cells. In addition, hGDH1, being a housekeeping enzyme, was also expressed in cells that lack endocrine function. Regarding human brain, study of cortical sections using immunofluorescence (IF) with confocal microscopy revealed that hGDH1 and hGDH2 were both expressed in the cytoplasm of gray and white matter astrocytes within coarse structures resembling mitochondria. Additionally, hGDH1 localized to the nuclear membrane of a subpopulation of astrocytes and of the vast majority of oligodendrocytes and their precursors. Remarkably, hGDH2-specific staining was detected in human cortical neurons, with different expression patterns having emerged. One pattern, observed in large cortical neurons (some with pyramidal morphology), was a hGDH2-specific labeling of cytoplasmic structures resembling mitochondria. These were distributed either in the cell body-axon or on the cell surface in close proximity to astrocytic end-feet that encircle glutamatergic synapses. Another pattern was observed in small cortical neurons with round dense nuclei in which the hGDH2-specific staining was found in the nuclear membrane. A detailed description of these observations and their functional implications, suggesting that the GDH flux is used by different cells to serve some of their unique functions, is presented below.

更新日期：2016-07-16

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