Jurivich D A, Chung J, Blenis J
Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611.
J Cell Physiol. 1991 Aug;148(2):252-9. doi: 10.1002/jcp.1041480210.
The regulation of S6 kinase activity was used to monitor perturbations of intracellular signaling activity during heat shock of quiescent murine and human fibroblasts. Previous reports on exponentially growing insect and plant cells had indicated that 40S ribosomal protein S6 is dephosphorylated during heat shock; thus inhibition of S6 kinase activity by heat shock was anticipated in NIH 3T3 fibroblasts and human cells (HeLa, diploid embryonic fibroblasts MRC-5, and skin-derived fibroblasts). Unexpectedly, two distinct S6 protein kinases were activated in quiescent fibroblasts after heat exposure. One of the enzymes was partially purified by sequential column chromatography and was determined to be equivalent to the enzyme activated by serum and other growth factors, referred to here as pp70-S6 protein kinase. The other protein S6 kinase, pp90rsk, was identified by a specific immunoprecipitation assay. Monitoring both enzymatic activities during heat shock revealed a temporal pattern of activation that was reversed when compared to non-stressed, mitogen-stimulated cells. Finally, heat shock stimulated protein S6 phosphorylation in cultured, quiescent mammalian cells. These data demonstrate that specific protein kinases can be activated during heat shock, and that some early mitogenic signals may also participate in the response of cells to physiologic stress.
利用S6激酶活性的调节来监测静止的小鼠和人成纤维细胞热休克期间细胞内信号活性的扰动。先前关于指数生长的昆虫和植物细胞的报道表明，40S核糖体蛋白S6在热休克期间发生去磷酸化；因此，预计在NIH 3T3成纤维细胞和人细胞（HeLa细胞、二倍体胚胎成纤维细胞MRC-5和皮肤来源的成纤维细胞）中热休克会抑制S6激酶活性。出乎意料的是，热暴露后静止的成纤维细胞中两种不同的S6蛋白激酶被激活。其中一种酶通过连续柱层析进行了部分纯化，确定其等同于由血清和其他生长因子激活的酶，此处称为pp70-S6蛋白激酶。另一种蛋白S6激酶，pp90rsk，通过特异性免疫沉淀试验鉴定。在热休克期间监测这两种酶活性揭示了一种激活的时间模式，与未受应激、有丝分裂原刺激的细胞相比，这种模式是相反的。最后，热休克刺激了培养的静止哺乳动物细胞中蛋白S6的磷酸化。这些数据表明，特定的蛋白激酶在热休克期间可以被激活，并且一些早期有丝分裂信号也可能参与细胞对生理应激的反应。
