Expression and patho-physiological function of cystine transporter

运输系统x_c^-介导细胞外胱氨酸和细胞内谷氨酸之间的交换运输。该系统由两种蛋白质组成，xCT和4F2hc，前者被认为是真正的转运蛋白。本项目研究了xCT基因在部分细胞和组织中的表达和转录调控，并尝试构建xCT基因敲除小鼠，以阐明xCT ^系统在全鼠中的病理生理作用。实验结果如下：xCT基因在脑膜和部分脑室周围器官，如脑后区和脑膜下器官中强烈表达。这可能表明系统x~'有助于维持脑脊液中的氧化还原状态（即半胱氨酸/胱氨酸比率）2。与顺铂敏感细胞株相比，系统x_c^-在顺铂耐药型人卵巢癌细胞株中高表达。发现系统x_c^-通过增加谷胱甘肽水平而促进顺铂耐药3。我们研究了亲电剂诱导体系x_c^-活性的机理。我们发现在xCT基因的5'侧区存在几个亲电反应元件，并且亲电剂通过其中一个与转录因子Nrf24相关的元件通过转录诱导xCT。我们研究了胱氨酸剥夺诱导x_c^-系统的机制。我们发现在xCT基因S'侧存在两个氨基酸应答元件，并且通过这两个元件与转录因子ATF45相关的胱氨酸剥夺诱导xCT转录。xCT基因敲除小鼠已被成功培育。目前，这些小鼠在出生3个月后明显正常，表型分析仍有待研究

Transport system x_c^-mediates the exchange transport between extracellular cystine and intracellular glutamate. This system is composed of two proteins, xCT and 4F2hc, and the former is thought to be the actual transporter. In this project we have investigated the expression and the transcriptional regulation of xCT gene in some cells and tissues and have tried to produce xCT gene-knockout mouse to elucidate the patho-physiological role of system x_c^-in whole mouse. The results are as follows1.xCT gene was strongly expressed in meninges and some circumventricular organs, e. g., area postrema and subfornical organ. This may suggest that system x~' contributes to the maintenance of the redox state (i, e., cysteine/cystine ratio) in the cerebrospinal fluid2.System x_c^-was highly expressed in cisplatin-resistant variant of human ovarian cancer cell lines compared with cisplatin sensitive cell lines. It was found that system x_c^-contributes to the cisplatin-resistancy by increasing glutathione level3.We have studied the mechanism by which system x_c^-activity is induced by electrophilic agents. We found that several electrophile response elements exist in the 5'-flanking region of xCT gene and that electrophilic agents induce the xCT transciptionally via one of these elements in association with the transcription factor Nrf24.We have studied the mechanism by which system x_c^-is induced by cystine deprivation. We found that two amino acid response elements exist in the S'-flanking region of xCT gene and that the xCT is induced transcriptionally by cystine deprivation via these two elements in association with the transcription factor ATF45.xCT gene-knockout mice have been successfully produced. At present these mice, three months after birth, are apparently normal and the phenotype analysis remains to be investigated