Blenis J, Erikson R L
Proc Natl Acad Sci U S A. 1986 Mar;83(6):1733-7. doi: 10.1073/pnas.83.6.1733.
Ribosomal protein S6 kinase activity was measured in lysates prepared from serum-deprived chicken embryo fibroblasts (CEF) treated for various times with phorbol 12-myristate 13-acetate (PMA). Maximal activity was observed within 15 min, and it declined to the initial level by 4 hr. Incubation of these cells with PMA 4-60 hr after the initial treatment did not result in an additional increase in S6 protein kinase activity. These results are consistent with down-regulation of the PMA receptor, protein kinase C, and the dependence of PMA-stimulated S6 kinase activity on this enzyme. Long-term pretreatment of CEF with PMA only partially attenuated the stimulation of the S6 protein kinase activity by serum or by expression of the Rous sarcoma virus transforming gene product, pp60v-src. A similar protein kinase activity also was stimulated in cells treated with cycloheximide or sodium vanadate. Pretreatment with PMA had little effect on this response. These data indicate that it is likely that there are at least two mechanisms through which S6 kinase activity can be regulated, one of which apparently utilizes protein kinase C whereas the other(s) does not. Additional experiments show PMA-stimulated glucose transport was not attenuated by long-term incubation with phorbol ester, suggesting that another mechanism, which is not dependent on the presence of protein kinase C, maintains this response after the proposed down-regulation of the PMA receptor.
在用佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）处理不同时间的血清饥饿鸡胚成纤维细胞（CEF）制备的裂解物中测量核糖体蛋白S6激酶活性。在15分钟内观察到最大活性，并在4小时时降至初始水平。在初始处理后4 - 60小时用PMA孵育这些细胞不会导致S6蛋白激酶活性进一步增加。这些结果与PMA受体、蛋白激酶C的下调以及PMA刺激的S6激酶活性对该酶的依赖性一致。用PMA对CEF进行长期预处理仅部分减弱了血清或劳氏肉瘤病毒转化基因产物pp60v - src的表达对S6蛋白激酶活性的刺激。在用环己酰亚胺或钒酸钠处理的细胞中也刺激了类似的蛋白激酶活性。用PMA预处理对这种反应影响很小。这些数据表明，S6激酶活性可能至少通过两种机制进行调节，其中一种显然利用蛋白激酶C，而另一种则不依赖于蛋白激酶C。额外的实验表明，长期用佛波醇酯孵育不会减弱PMA刺激的葡萄糖转运，这表明在PMA受体下调后，另一种不依赖于蛋白激酶C存在的机制维持了这种反应。
