van Zoelen E J, Mummery C L, Boonstra J, van der Saag P T, de Laat S W
J Cell Biochem. 1983;21(1):77-91. doi: 10.1002/jcb.240210109.
The pumping activity of the plasma membrane-bound Na+,K+-ATPase shows considerable variation during the cell cycle of mouse neuroblastoma Neuro-2A cells. Addition of external ATP at millimolar concentrations, which selectively enhances the plasma membrane permeability of Neuro-2A cells for sodium ions, stimulates the Na+,K+-ATPase pumping activity at all phases of the cell cycle from a factor of 1.05 in mitosis up to 2.2 in G1 phase. Determination of the number of Na+,K+-ATPase copies per cell by direct 3H-ouabain binding studies in the presence of external ATP shows a gradual increase in the number of pump sites on passing from mitosis to the late S/G2-phase by approximately a factor of 2. From these data the pumping activity per copy of Na+,K+-ATPase, optimally stimulated with respect to its various substrate ions, has been determined during the various phases of the cell cycle. This optimally stimulated pumping activity per enzyme copy, which is a reflection of the physicochemical state of the plasma membrane, is high in mitosis, almost twofold lower in early G1 phase, and increases gradually again during the other phases of the cell cycle. This shows that the observed regulation of Na+,K+-ATPase activity during the cell cycle is caused by a combination of three independent factors--namely variation in intracellular substrate availability (Na+), changes in number of enzyme copies per cell, and modulation of the plasma membrane environment of the protein molecules. The modulation of the optimal pumping activity per enzyme copy shows a good correlation (rho = 0.96) with the known modulation of protein lateral mobility during the cell cycle, such that a high protein lateral mobility correlates with a low enzyme activity. It is concluded that changes in plasma membrane properties take place during the Neuro-2A cell cycle that result in changes in the rate of protein lateral diffusion and Na+,K+-ATPase activity in directly correlated way.
质膜结合的Na⁺,K⁺-ATP酶的泵浦活性在小鼠神经母细胞瘤Neuro-2A细胞的细胞周期中表现出相当大的变化。添加毫摩尔浓度的外部ATP，可选择性增强Neuro-2A细胞对钠离子的质膜通透性，在细胞周期的所有阶段均刺激Na⁺,K⁺-ATP酶的泵浦活性，从有丝分裂期的1.05倍到G1期的2.2倍。在存在外部ATP的情况下，通过直接³H-哇巴因结合研究确定每个细胞中Na⁺,K⁺-ATP酶的拷贝数，结果显示从有丝分裂期到S/G2期后期，泵浦位点的数量逐渐增加，约为2倍。根据这些数据，已确定在细胞周期的各个阶段，相对于其各种底物离子而言被最佳刺激的每个Na⁺,K⁺-ATP酶拷贝的泵浦活性。这种每个酶拷贝的最佳刺激泵浦活性反映了质膜的物理化学状态，在有丝分裂期较高，在G1期早期几乎低两倍，并且在细胞周期的其他阶段再次逐渐增加。这表明在细胞周期中观察到的Na⁺,K⁺-ATP酶活性调节是由三个独立因素共同作用引起的，即细胞内底物可用性（Na⁺）的变化、每个细胞中酶拷贝数的变化以及蛋白质分子质膜环境的调节。每个酶拷贝的最佳泵浦活性调节与细胞周期中已知的蛋白质侧向迁移率调节具有良好的相关性（ρ = 0.96），使得高蛋白侧向迁移率与低酶活性相关。得出的结论是，在Neuro-2A细胞周期中发生了质膜性质的变化，这些变化以直接相关的方式导致蛋白质侧向扩散速率和Na⁺,K⁺-ATP酶活性的变化。
