Lee E, Shelden E A, Knecht D A
Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA.
Exp Cell Res. 1997 Aug 25;235(1):295-9. doi: 10.1006/excr.1997.3665.
Fluorescent phalloidin has been introduced into Dicytostelium amoebae in order to visualize dynamic changes in the localization of F-actin during pseudopod extension. Phalloidin was initially localized to the peripheral cortex of the cell. Newly formed pseudopods were not fluorescent, indicating that phalloidin was tightly bound to existing F-actin filaments and could not rapidly relocalize to newly formed filaments. As pseudopod extension proceeded, the fluorescent signal disappeared from the region directly underlying the expansion zone, leaving a gap in the actin cortex. Similar results were obtained in both wild-type cells and those lacking myosin II heavy chain. The disappearance of the fluorescent signal from the cortical region underlying the new pseudopod is presumed to be due to breakdown of the actin cortex and dispersion of the remnants. These results suggest that new pseudopods are not built upon the existing actin cortex but rather that the cortex is locally solated as part of the construction of the new actin network.
为了观察伪足延伸过程中F-肌动蛋白定位的动态变化，荧光鬼笔环肽已被引入盘基网柄菌变形虫中。鬼笔环肽最初定位于细胞的外周皮质。新形成的伪足没有荧光，这表明鬼笔环肽与现有的F-肌动蛋白丝紧密结合，不能迅速重新定位于新形成的丝上。随着伪足延伸的进行，荧光信号从扩张区正下方的区域消失，在肌动蛋白皮质中留下一个间隙。在野生型细胞和缺乏肌球蛋白II重链的细胞中都得到了类似的结果。新伪足下方皮质区域荧光信号的消失被认为是由于肌动蛋白皮质的分解和残余物的分散。这些结果表明，新的伪足不是建立在现有的肌动蛋白皮质上，而是皮质作为新肌动蛋白网络构建的一部分被局部溶解。
