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升高大鼠肝细胞内谷胱甘肽水平：肝细胞生长因子可引起大鼠肝细胞内谷胱甘肽水平的升高，且呈剂量和时间依赖性。γ生物合成限速酶--谷氨酰半胱氨酸合成酶(γ-GCS)的活性也明显增强。Northern印迹分析显示γ-GCS mRNA的表达被诱导。这些结果表明，生长激素诱导谷胱甘肽合成与γ-gcs基因转录激活及随后γ-gcs活性升高有关。(2)γ-谷氨酰半胱氨酸合成酶在再生大鼠肝脏中的表达：在再生大鼠肝脏中，γ-gcs活性升高，在第2天达到最大值。γ-GCS m RNA的表达在24 h内升高，在第二天达到最高。这些结果表明，肝部分切除后再生肝中γ-gcs基因的转录激活和γ-gcs活性的序列上调有关。(3)酿酒酵母在好氧和厌氧条件下培养：空气水平的氧气胁迫和压力保护：啤酒酵母细胞在好氧和厌氧条件下分别进行有氧和厌氧培养，检测并比较两种细胞中保护物质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。好氧提高了化合物和酶的活性。谷胱甘肽合成的增加可能与半胱氨酸水平的增加有关，而半胱氨酸水平的增加又被发现是由半胱氨酸β合成酶的氧依赖激活控制的。

(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.