Schulze E, Kirschner M
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
Nature. 1988 Jul 28;334(6180):356-9. doi: 10.1038/334356a0.
The microtubule cytoskeleton is thought to be intimately involved in generating and maintaining cell polarity and can generate many different morphological structures from a few structural elements. The mechanism by which these structures are generated has been partially elucidated from studies of microtubule polymerization both in vitro and in vivo. Microtubules in vitro exist in growing (polymerizing) and shrinking (depolymerizing) populations that interconvert infrequently. This behaviour, termed dynamic instability, permits microtubules in the cell rapidly to explore different arrangements and allows selective stabilization of specific morphologies. To investigate the regulation of these processes, we have implemented techniques for direct observation of fluorescently labelled microtubules and developed them to observe the dynamic behaviour of individual microtubules in single living cells. Sammak and Borisy recently used this technique to show that the dynamics of microtubules in fibroblasts is explained by dynamic instability. Although we also conclude here that dynamic instability explains much of microtubule behaviour in vivo, we find significant deviations from the properties of tubulin in vitro. These results suggest that local cytoplasmic factors strongly influence microtubule dynamics; such control has important implications for cellular morphogenesis.
微管细胞骨架被认为与细胞极性的产生和维持密切相关，并且能够从少数结构元件生成许多不同的形态结构。这些结构产生的机制已通过体外和体内微管聚合研究得到部分阐明。体外微管存在于生长（聚合）和收缩（解聚）群体中，它们很少相互转换。这种行为被称为动态不稳定性，它使细胞中的微管能够快速探索不同的排列方式，并允许特定形态的选择性稳定。为了研究这些过程的调控，我们采用了直接观察荧光标记微管的技术，并对其进行改进以观察单个活细胞中单个微管的动态行为。Sammak和Borisy最近使用这项技术表明，成纤维细胞中微管的动态变化可以用动态不稳定性来解释。虽然我们在此也得出结论，动态不稳定性解释了体内微管行为的大部分，但我们发现其与体外微管蛋白的特性存在显著差异。这些结果表明，局部细胞质因子强烈影响微管动态；这种调控对细胞形态发生具有重要意义。
