University of Manchester, C.4255 Michael Smith Building, Faculty of Life Sciences, Oxford Road, Manchester M13 9PT, UK.
Curr Opin Cell Biol. 2012 Dec;24(6):838-44. doi: 10.1016/j.ceb.2012.08.003. Epub 2012 Sep 2.
Tight coupling between cell growth and cell cycle progression allows cells to adjust their size to the demands of proliferation in varying nutrient environments. Target of rapamycin (TOR) signalling pathways co-ordinate cell growth with cell cycle progression in response to altered nutritional availability. To increase cell size the active TOR Complex 1 (TORC1) promotes cell growth to delay mitosis and cell division, whereas under limited nutrients TORC1 activity is decreased to reduce cell size. It remains unclear why cell size is subject to such tight control. Recent evidence suggests that in addition to modulating cell size, changes in nutrient availability also alter nuclear:cytoplasmic (N/C) ratios and may therefore compromise optimal cellular physiology. This could explain why cells increase their size when conditions are favourable, despite being competent to survive at a smaller size if necessary.
细胞生长和细胞周期进程之间的紧密偶联使细胞能够根据不同营养环境中增殖的需求来调整其大小。雷帕霉素靶蛋白（TOR）信号通路通过改变营养物质的可用性来协调细胞生长和细胞周期进程。为了增加细胞大小，活跃的雷帕霉素复合物 1（TORC1）促进细胞生长以延迟有丝分裂和细胞分裂，而在有限的营养物质下，TORC1 的活性降低以减少细胞大小。目前尚不清楚为什么细胞大小受到如此严格的控制。最近的证据表明，除了调节细胞大小外，营养物质可用性的变化还会改变核质比（N/C），因此可能会损害最佳的细胞生理机能。这可以解释为什么在条件有利的情况下，细胞会增加其大小，尽管在必要时，细胞有能力在更小的尺寸下生存。
