Knirsch L, Clerch L B
Lung Biology Laboratory, Department of Pediatrics, Georgetown University School of Medicine, Washington, DC 20007, USA.
Biochemistry. 2001 Jul 3;40(26):7890-5. doi: 10.1021/bi010197n.
All cells tested contain a cytosolic protein that binds to a defined region in the 3' untranslated region of manganese superoxide dismutase (MnSOD) RNA; both the MnSOD RNA-binding protein (MnSOD-BP) and the cis element are required for efficient translation of MnSOD RNA [Chung, D. J., Wright, A. E., and Clerch, L. B. (1997) Biochemistry 37, 16298-16306]. This study was designed to test the hypothesis that MnSOD-BP activity is regulated by phosphorylation. When cell extracts from whole rat lung or a rat lung fibroblast cell line, RFL-6, were treated in vitro with a protein tyrosine phosphatase, there was a 4-fold increase in MnSOD-BP activity indicating that MnSOD-BP activity was upregulated by tyrosine dephosphorylation. RFL-6 cells treated in cell culture with herbimycin A or genistein, inhibitors of protein tyrosine kinase, had significantly more MnSOD-BP activity than cells treated with diluent. In RFL-6 cells treated with herbimycin A, the increase in MnSOD-BP activity was associated with an increase in the level of MnSOD protein without a change in MnSOD mRNA concentration. We propose that the modulation of MnSOD protein expression by the tyrosine phosphorylation state of MnSOD-BP is a potential therapeutic target for increasing MnSOD activity during periods of oxidative stress.
所有被检测的细胞都含有一种胞质蛋白，该蛋白可与锰超氧化物歧化酶（MnSOD）RNA的3'非翻译区中的一个特定区域结合；锰超氧化物歧化酶RNA结合蛋白（MnSOD-BP）和顺式元件对于MnSOD RNA的有效翻译都是必需的[Chung, D. J., Wright, A. E., and Clerch, L. B. (1997) Biochemistry 37, 16298 - 16306]。本研究旨在验证MnSOD-BP活性受磷酸化调节这一假说。当用蛋白酪氨酸磷酸酶体外处理来自大鼠全肺或大鼠肺成纤维细胞系RFL-6的细胞提取物时，MnSOD-BP活性增加了4倍，这表明MnSOD-BP活性通过酪氨酸去磷酸化而上调。在细胞培养中用蛋白酪氨酸激酶抑制剂赫曲霉素A或染料木黄酮处理的RFL-6细胞，其MnSOD-BP活性显著高于用稀释剂处理的细胞。在用赫曲霉素A处理的RFL-6细胞中，MnSOD-BP活性的增加与MnSOD蛋白水平的增加相关，而MnSOD mRNA浓度没有变化。我们提出，MnSOD-BP的酪氨酸磷酸化状态对MnSOD蛋白表达的调节是在氧化应激期间增加MnSOD活性的一个潜在治疗靶点。
