Hypoxia regulates glutamate metabolism and membrane transport in rat PC12 cells
Hypoxia regulates glutamate metabolism and membrane transport in rat PC12 cells
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DOI：
10.1046/j.1471-4159.2001.00214.x
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发表时间：
2001-03-01
影响因子：
4.7
通讯作者：
Millhorn, DE
中科院分区：
文献类型：
--
作者：
Kobayashi, S;Millhorn, DE
我们研究了缺氧对大鼠嗜铬细胞瘤（PC12）细胞谷氨酸代谢和摄取的影响。与谷氨酸产生、代谢和运输有关的各种关键酶在缺氧条件下得到协调调节。PC12细胞表达两种谷氨酸代谢酶，谷氨酰胺合成酶（GS）和谷氨酸脱羧酶（GAD），以及谷氨酸产生酶，磷酸活化谷氨酰胺酶（PAG）。暴露于缺氧（1% O-2） 6小时或更长时间后，GS mRNA和蛋白的表达增加，GS酶活性增强。缺氧导致PAG mRNA和蛋白表达显著降低，PAG活性降低。此外，缺氧导致GAD65和GAD67蛋白水平和GAD酶活性升高。PC12细胞表达三种Na+依赖性谷氨酸转运蛋白；EAAC1， GLT-1和GLAST。缺氧使EAAC1和GLT-1蛋白水平升高，但对GLAST无影响。慢性缺氧显著增强谷氨酸转运的Na+依赖成分。此外，慢性缺氧使谷氨酸含量降低，但使谷氨酰胺含量升高。综上所述，低氧诱导的谷氨酸代谢和转运相关酶的变化与谷氨酸细胞外浓度的降低是一致的。这可能在慢性缺氧时保护PC12细胞免受谷氨酸的细胞毒性作用中起作用。
We investigated the effect of hypoxia on glutamate metabolism and uptake in rat pheochromocytoma (PC12) cells. Various key enzymes relevant to glutamate production, metabolism and transport were coordinately regulated by hypoxia. PC12 cells express two glutamate-metabolizing enzymes, glutamine synthetase (GS) and glutamate decarboxylase (GAD), as well as the glutamate-producing enzyme, phosphate-activated glutaminase (PAG). Exposure to hypoxia (1% O-2) for 6 h or longer increased expression of GS mRNA and protein and enhanced GS enzymatic activity. In contrast, hypoxia caused a significant decrease in expression of PAG mRNA and protein, and, also decreased PAG activity. In addition, hypoxia led to an increase in GAD65 and GAD67 protein levels and GAD enzymatic activity. PC12 cells express three Na+-dependent glutamate transporters; EAAC1, GLT-1 and GLAST. Hypoxia increased EAAC1 and GLT-1 protein levels, but had no effect on GLAST. Chronic hypoxia significantly enhanced the Na+-dependent component of glutamate transport. Furthermore, chronic hypoxia decreased cellular content of glutamate, but increased that of glutamine. Taken together, the hypoxia-induced changes in enzymes related to glutamate metabolism and transport are consistent with a decrease in the extracellular concentration of glutamate. This may have a role in protecting PC12 cells from the cytotoxic effects of glutamate during chronic hypoxia.