Rinnerthaler G, Herzog M, Klappacher M, Kunka H, Small J V
Institute for Molecular Biology, Austrian Academy of Sciences, Salzburg.
J Struct Biol. 1991 Feb;106(1):1-16. doi: 10.1016/1047-8477(91)90058-5.
The first event in the process of translocation of a cell over a substrate is the forward protrusion of a thin layer of cytoplasm, sometimes referred to as the leading edge. To gain more direct information on structural reorganizations associated with protrusion we have documented the ultrastructure of the actin cytoskeleton of mouse macrophages whose history of locomotion prior to fixation for electron microscopy had been recorded by video microscopy. It is shown that rapid protrusion is associated with the formation of a dense, diagonal network of actin filaments, lacking organized bundles. In cell edges that showed minor fluctuations back and forth over a period of 30 sec or more no dense meshworks were found: instead, a loose peripheral bundle of actin filaments was commonly observed. Cell edges that first protruded and then retracted showed a similar ultrastructure to those that exhibited only forward movement, but the width of the leading edge meshwork was, by comparison, reduced. Measurements showed that there was an approximate correlation between the leading edge mesh width and the net forward translocation observed during the terminal 30 sec, up to fixation. The results are discussed in relation to present concepts of the protrusion mechanism.
细胞在基质上迁移过程中的首个事件是一层薄细胞质向前突出，有时被称为前缘。为了获取更多与突出相关的结构重组的直接信息，我们记录了小鼠巨噬细胞肌动蛋白细胞骨架的超微结构，这些巨噬细胞在用于电子显微镜观察的固定之前的运动过程已通过视频显微镜记录下来。结果表明，快速突出与肌动蛋白丝形成密集的对角网络有关，缺乏有组织的束状结构。在30秒或更长时间内来回有微小波动的细胞边缘未发现密集网络：相反，通常观察到松散的周边肌动蛋白丝束。先突出然后缩回的细胞边缘与仅向前移动的细胞边缘具有相似的超微结构，但相比之下，前缘网络的宽度减小。测量表明，前缘网络宽度与固定前最后30秒内观察到的净向前迁移之间存在近似相关性。结合当前关于突出机制的概念对结果进行了讨论。
