Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy.
Mol Cell Biochem. 2011 Oct;356(1-2):269-75. doi: 10.1007/s11010-011-0958-3. Epub 2011 Jul 13.
CK2 is a highly conserved protein kinase involved in different cellular processes, which shows a higher activity in actively proliferating mammalian cells and in various types of cancer and cancer cell lines. We recently demonstrated that CK2 activity is strongly influenced by growth rate in yeast cells as well. Here, we extend our previous findings and show that, in cells grown in either glucose or ethanol-supplemented media, CK2 presents no alteration in K(m) for both the ATP and the peptide substrate RRRADDSDDDDD, while a significant increase in V (max) is observed. In chemostat-grown cells, no difference of CK2 activity was observed in cells grown at the same dilution rate in media supplemented with either ethanol or glucose, excluding the contribution of carbon metabolism on CK2 activity. By using the eIF2β-derived peptide, which can be phosphorylated by the holoenzyme but not by the free catalytic subunits, we show that the holoenzyme activity requires the concurrent presence of both β and β' encoding genes. Finally, conditions of nitrogen deprivation leading to a G0-like arrest result in a decrease of total CK2 activity, but have no effect on the activity of the holoenzyme. These findings newly indicate a regulatory role of β and β' subunits of CK2 in the nutrient response.
CK2 是一种高度保守的蛋白激酶，参与多种细胞过程，在活跃增殖的哺乳动物细胞和各种类型的癌症及癌细胞系中表现出更高的活性。我们最近证明，CK2 的活性在酵母细胞中也受到生长速度的强烈影响。在这里，我们扩展了之前的发现，表明在葡萄糖或乙醇补充培养基中生长的细胞中，CK2 对 ATP 和肽底物 RRRADDSDDDDD 的 K(m) 没有变化，而 V(max) 显著增加。在恒化器培养的细胞中，在补充有乙醇或葡萄糖的培养基中以相同稀释率生长的细胞中，没有观察到 CK2 活性的差异，排除了碳代谢对 CK2 活性的贡献。通过使用可以被全酶而不是游离催化亚基磷酸化的 eIF2β 衍生肽，我们表明全酶活性需要同时存在 β 和 β'编码基因。最后，导致 G0 样停滞的氮饥饿条件导致总 CK2 活性下降，但对全酶活性没有影响。这些发现新表明 CK2 的β和β'亚基在营养响应中起调节作用。
