Imuta N, Ogawa S, Maeda Y, Kuwabara K, Hori O, Ueda H, Yanagihara T, Tohyama M
Department of Neurology, Osaka University Medical School, Suita, Japan.
J Neurochem. 1998 Feb;70(2):550-7. doi: 10.1046/j.1471-4159.1998.70020550.x.
Protein synthesis is important in the readaptive processes for cultured astrocytes after hypoxia and subsequent reoxygenation. We have identified 72-kDa inducible heat shock protein (HSP72) as a major stress protein in reoxygenated astrocytes. To assess the mechanism for reoxygenation-mediated induction of HSP72, a reporter gene that consists of a human HSP promoter fused to the luciferase gene was transfected into cultured astrocytes. Analysis of cellular energy nucleotides showed an increase of the ADP/ATP ratio after reoxygenation, which synchronized with activation of the HSP promoter. Activation of the HSP promoter was also observed after an addition of iodoacetic acid to hypoxic astrocytes, which reached the maximum when the ADP/ATP ratio reached 50%, but further decline in the energy profile caused inactivation of this promoter. Inhibition of protein synthesis after reoxygenation resulted in temporary restoration of the energy profile and suppression of the DNA binding activity of the heat shock factor. Addition of quercetin greatly decreased the [3H]leucine incorporation in the polysome fraction without any effect on the mature mRNA formation. These data suggest that the energy depletion in reoxygenation triggers induction of HSP72 after reoxygenation, which may act as a pivotal mediator in the stress response of reoxygenated astrocytes by facilitating protein synthesis.
蛋白质合成在缺氧及随后复氧后培养的星形胶质细胞的再适应过程中很重要。我们已确定72 kDa诱导型热休克蛋白（HSP72）是复氧星形胶质细胞中的主要应激蛋白。为评估复氧介导的HSP72诱导机制，将一个由人HSP启动子与荧光素酶基因融合而成的报告基因转染到培养的星形胶质细胞中。细胞能量核苷酸分析显示复氧后ADP/ATP比值增加，这与HSP启动子的激活同步。向缺氧星形胶质细胞中添加碘乙酸后也观察到HSP启动子的激活，当ADP/ATP比值达到50%时达到最大值，但能量状态的进一步下降导致该启动子失活。复氧后抑制蛋白质合成导致能量状态暂时恢复，并抑制热休克因子的DNA结合活性。添加槲皮素大大降低了多核糖体组分中[3H]亮氨酸的掺入，而对成熟mRNA的形成没有任何影响。这些数据表明，复氧时的能量消耗触发了复氧后HSP72的诱导，HSP72可能通过促进蛋白质合成在复氧星形胶质细胞的应激反应中起关键介导作用。
