A new regulation system by Ca binding protein in photoreceptor signal transduction

(1)肝细胞生长因子通过诱导γ-谷氨酰半胱氨酸合成酶提高大鼠肝细胞谷胱甘肽水平：发现肝细胞生长因子（HGF）可引起大鼠肝细胞内谷胱甘肽（GSH）水平呈剂量和时间依赖性升高。GSH生物合成的限制性酶γ-谷氨酰半胱氨酸合成酶（γ-GCS）的活性也被HGF提高。Northern blot分析显示γ-GCS mRNA被诱导。这些结果表明，HGH诱导GSH合成与γ-GCS基因的转录激活以及随后γ-GCS活性的升高有关。(2)再生大鼠肝脏γ-谷氨酰半胱氨酸合成酶mRNA表达：再生大鼠肝脏GSH水平γ-GCS活性升高，在第2天达到最大值。γ-GCS mRNA的表达在24 h内增加，在第2天达到最大值。上述结果提示，部分肝切除术后再生大鼠肝脏GSH水平升高与γ-GCS基因转录激活和γ-GCS活性序列升高有关。(3)在好氧和厌氧条件下培养的酿酒酵母：空气水平的氧胁迫和对应激的保护：在好氧和厌氧条件下培养酿酒酵母细胞，测定并比较两种细胞对氧胁迫的保护化合物半胱氨酸和谷胱甘肽的水平，以及防御酶、过氧化氢酶和超氧化物歧化酶的活性。好氧作用增加了化合物和酶的活性。谷胱甘肽合成的升高可能与半胱氨酸水平的升高有关，而半胱氨酸水平的升高又被发现是由半胱甘氨酸β合酶的氧依赖性激活控制的。

(1) Elevation of Glutathione Level in Rat Hepatocytes by Hepatocyte Growth Factor via Induction of γ-Glutamylcysteine Synthetase : Hepatocyte growth factor (HGF) was found to cause a dose-and time-dependent increase in intracellular glutathione (GSH) level in rat hepatocytes. The activity of γ-glutamylcysteine synthetase (γ-GCS), the rate-limiting enzyme of GSH biosynthesis, was also increased by HGF. Northern blot analysis revealed the induction of γ-GCS mRNA. These results suggested that the induction of GSH synthesis by HGH is associated with the transcriptional activation of γ-GCS gene and the subsequent elevation of γ-GCS activity.(2) Expression of γ-Glutamylcysteine Synthetase mRNA in Regenerating Rat Liver : The GSH level γ-GCS activity increased in regenerating rat liver, reaching a maximum on day 2. Furthermore, γ-GCS mRNA expression increased within 24 h and reached maximum on day 2. These results suggest that the increased GSH level in regenerating rat liver after partial hepatectomy is associated with the transcriptional activation of γ-GCS gene and the sequence elevation in γ-GCS activity.(3) Saccharomyces cerevisiae cultured under aerobic and anaerobic conditions : air-level oxygen stress and protection against stress : Cells of Saccharomyces cerevisiae were grown aerobically and anaerobically, and levels of the protective compounds, cysteine and glutathione, and activities of defensive enzynes, catalase and superoxide dismutase, against an oxygen stress were determined and compared in both cells. Aerobiosis increased both the compounds and enzyme activities. The elevated synthesis of glutathione could be associated with the increased levels of cysteine which in its turn was found to be controlled by the oxygen-dependent activation of cystathionine β-synthase.