Cao L G, Wang Y L
Cell Biology Group, Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
J Cell Biol. 1990 Nov;111(5 Pt 1):1905-11. doi: 10.1083/jcb.111.5.1905.
The contractile ring in dividing animal cells is formed primarily through the reorganization of existing actin filaments (Cao, L.-G., and Y.-L. Wang. 1990. J. Cell Biol. 110:1089-1096), but it is not clear whether the process involves a random recruitment of diffusible actin filaments from the cytoplasm, or a directional movement of cortically associated filaments toward the equator. We have studied this question by observing the distribution of actin filaments that have been labeled with fluorescent phalloidin and microinjected into dividing normal rat kidney (NRK) cells. The labeled filaments are present primarily in the cytoplasm during prometaphase and early metaphase, but become associated extensively with the cell cortex 10-15 min before the onset of anaphase. This process is manifested both as an increase in cortical fluorescence intensity and as movements of discrete aggregates of actin filaments toward the cortex. The concentration of actin fluorescence in the equatorial region, accompanied by a decrease of fluorescence in polar regions, is detected 2-3 min after the onset of anaphase. By directly tracing the distribution of aggregates of labeled actin filaments, we are able to detect, during anaphase and telophase, movements of cortical actin filaments toward the equator at an average rate of 1.0 micron/min. Our results, combined with previous observations, suggest that the organization of actin filaments during cytokinesis probably involves an association of cytoplasmic filaments with the cortex, a movement of cortical filaments toward the cleavage furrow, and a dissociation of filaments from the equatorial cortex.
动物细胞分裂时的收缩环主要是通过对现有肌动蛋白丝的重新组织形成的(Cao, L.-G., and Y.-L. Wang. 1990. J. Cell Biol. 110:1089 - 1096),但尚不清楚该过程是涉及从细胞质中随机募集可扩散的肌动蛋白丝,还是皮质相关丝向赤道方向的定向移动。我们通过观察用荧光鬼笔环肽标记并显微注射到分裂的正常大鼠肾(NRK)细胞中的肌动蛋白丝的分布来研究这个问题。标记的丝在前期和早中期主要存在于细胞质中,但在后期开始前10 - 15分钟与细胞皮质广泛结合。这个过程表现为皮质荧光强度的增加以及肌动蛋白丝离散聚集体向皮质的移动。后期开始后2 - 3分钟,检测到赤道区域肌动蛋白荧光浓度增加,同时极区荧光减少。通过直接追踪标记的肌动蛋白丝聚集体的分布,我们能够在后期和末期检测到皮质肌动蛋白丝以平均1.0微米/分钟的速度向赤道移动。我们的结果与先前的观察结果相结合,表明胞质分裂期间肌动蛋白丝的组织可能涉及细胞质丝与皮质的结合、皮质丝向分裂沟的移动以及丝从赤道皮质的解离。