DIFFERENTIATION AND REGULATION OF GENE EXPRESSION IN ASTROCYTES AND NEURONS

我们研究了编码蛋白质的基因的调控 对星形胶质细胞的分化和 星形胶质细胞和神经元之间的联系。 我们筛选了人类和老鼠 编码谷氨酰胺的cDNA的脑表达文库 合成酶（GS）、谷氨酸脱氢酶（GDH）和谷氨酸脱氢酶 (GA)并测定了后两者的核苷酸序列。 地塞米松诱导GS mRNA的合成，但不诱导 另外两种酶。 在硫代乙酰胺诱导的肝 大鼠脑组织中谷氨酸脱羧酶水平 (GAD)mRNA保持不变，GDH下降， GA，尤其是GS的水平增加;这与 预期谷氨酸在星形胶质细胞中是稀缺的，因为它 迅速转化为谷氨酰胺。 我们分离出一个星形胶质细胞 不产生任何胶质细胞酸性的衍生细胞系 蛋白（GFAP）或其mRNA;暴露后GTP剥夺 对于霉酚酸盐，转录和转导都被诱导 大约20倍。 检测了脑细胞的一些主要膜蛋白。 一个与主要的生长锥相同或非常相似 蛋白质（GAP-43）的MW、等电点、磷酸化和 抗体染色。 我们发现这种蛋白质是糖基化的， 可以用碘标记整个细胞，这表明它 穿过细胞膜到达外界。 既然我们找到了 蛋白质也存在于星形胶质细胞中，它可能参与星形胶质细胞/神经元 互动 我们还发现了一种促进神经突生长的 星形胶质细胞细胞外基质中的一种因子，可能是层粘连蛋白 因为生长至少部分地被抗- 层粘连蛋白。

We investigate the regulation of genes encoding proteins important for astrocyte differentiation and the interaction between astrocytes and neurons. We have screened human and rat brain expression libraries for cDNAs encoding glutamine synthetase (GS), glutamate dehydrogenase (GDH) and glutaminase (GA) and determined the nucleotide sequences of the latter two. Dexamethasone induced the synthesis of GS mRNA but not of the other two enzymes. During thioacetamide induced hepatic encephalopathy in the rat, the level of glutamate decarboxylase (GAD) mRNA remained constant, that of GDH decreased whereas the levels of GA and especially GS increased; this agrees with the expectation that glutamate is scarce in astrocytes because it is rapidly converted to glutamine. We have isolated an astrocyte derived cell line which does not produce any glial fibrillary acidic protein (GFAP) or its mRNA; upon GTP deprivation by exposure to mycophenolate, both transcription and transduction are induced about 20-fold. Some major membrane proteins of brain cells were examined. One was identical or very similar to the major growth cone protein (GAP-43) by MW, isoelectric point, phosphorylation, and antibody staining. We found that this protein is glycosylated and can be labeled with iodine in whole cells, which indicates that it reaches through the membrane to the outside. Since we find the protein also in astrocytes, it may be involved in astrocyte/neuron interaction. We have also identified a neurite growth promoting factor in the extracellular matrix of astrocytes; it may be laminin because the outgrowth is at least partially inhibited by anti- laminin.