Shutova Maria S, Alexandrova Antonina Y, Vasiliev Jury M
Institute of Carcinogenesis, Cancer Research Center, Russian Academy of Medical Sciences, Moscow, Russia.
Cell Motil Cytoskeleton. 2008 Sep;65(9):734-46. doi: 10.1002/cm.20295.
Interplay of two cytoskeletal systems--microfilaments and microtubules is essential for directional cell movement. To better understand the role of those cytoskeletal systems in polarization of cells, rat fibroblasts were incubated with drugs inhibiting activity of myosin II: blebbistatin and Y-27632. Both drugs led to disappearance of actin-myosin bundles and mature focal cell-matrix adhesions but did not affect polarization and directional motility. The rate of motility even increased after inhibitor treatment. The characteristic feature of inhibitor-treated fibroblasts was collapse of the cytoplasm accompanied by bundling of microtubules that led to transformation of lamellae into long immobile tails. The only exception was the leading anterior lamella which was not transformed into the tail and supported directional movement of the cell. The tail at the cell rear determined the position of anterior lamella and direction of locomotion. Depolymerization of microtubules by colcemid stopped directional locomotion of inhibitor-treated cells. These data show that integrity of the microtubular system provides the basic mechanism of polarization and orientation which is only modified by interactions with actin-myosin system and cell-substrate adhesions. We suggest that the position of bundled tail microtubules and dispersed microtubules in leading lamella determine polarization in cells lacking stress fibers and focal adhesions. Thus, polarization is based on microtubule-dependent mechanisms both in non-contractile and contractile cells. These mechanisms could switch dependent on circumstances as fibroblasts may acquire non-contractile phenotype, not only after direct inhibition of myosin II but also in certain conditions of microenvironment.
两个细胞骨架系统——微丝和微管之间的相互作用对于细胞的定向运动至关重要。为了更好地理解这些细胞骨架系统在细胞极化中的作用，将大鼠成纤维细胞与抑制肌球蛋白II活性的药物：blebbistatin和Y - 27632一起孵育。两种药物都导致肌动蛋白 - 肌球蛋白束和成熟的局灶性细胞 - 基质黏附消失，但不影响极化和定向运动性。抑制剂处理后运动速率甚至增加。经抑制剂处理的成纤维细胞的特征是细胞质塌陷，伴有微管成束，导致片状伪足转变为长长的不动尾巴。唯一的例外是前端的片状伪足，它没有转变为尾巴并支持细胞的定向运动。细胞后端的尾巴决定了前端片状伪足的位置和运动方向。用秋水仙酰胺使微管解聚会阻止经抑制剂处理的细胞的定向运动。这些数据表明，微管系统的完整性提供了极化和定向的基本机制，该机制仅通过与肌动蛋白 - 肌球蛋白系统和细胞 - 底物黏附的相互作用而被修饰。我们认为，成束的尾巴微管和前端片状伪足中分散的微管的位置决定了缺乏应力纤维和黏着斑的细胞中的极化。因此，无论是在非收缩性细胞还是收缩性细胞中，极化都是基于微管依赖性机制。这些机制可能会根据情况而切换，因为成纤维细胞不仅在直接抑制肌球蛋白II后，而且在某些微环境条件下可能会获得非收缩性表型。
