Heinrich Doris, Youssef Simon, Schroth-Diez Britta, Engel Ulrike, Aydin Daniel, Blümmel Jacques, Spatz Joachim P, Gerisch Günther
Department für Physik, Ludwig-Maximilians-Universität, München, Germany.
Cell Adh Migr. 2008 Apr-May;2(2):58-68. doi: 10.4161/cam.2.2.6190. Epub 2008 Apr 23.
The spreading of motile cells on a substrate surface is accompanied by reorganization of their actin network. We show that spreading in the highly motile cells of Dictyostelium is non-monotonic, and thus differs from the passage of spreading cells through a regular series of stages. Quantification of the gain and loss of contact area revealed fluctuating forces of protrusion and retraction that dominate the interaction of Dictyostelium cells with a substrate. The molecular basis of these fluctuations is elucidated by dual-fluorescence labeling of filamentous actin together with proteins that highlight specific activities in the actin system. Front-to-tail polarity is established by the sorting out of myosin-II from regions where dense actin assemblies are accumulating. Myosin-IB identifies protruding front regions, and the Arp2/3 complex localizes to lamellipodia protruded from the fronts. Coronin is used as a sensitive indicator of actin disassembly to visualize the delicate balance of polymerization and depolymerization in spreading cells. Short-lived actin patches that co-localize with clathrin suggest that membrane internalization occurs even when the substrate-attached cell surface expands. We conclude that non-monotonic cell spreading is characterized by spatiotemporal patterns formed by motor proteins together with regulatory proteins that either promote or terminate actin polymerization on the scale of seconds.
运动细胞在底物表面的铺展伴随着其肌动蛋白网络的重组。我们发现，盘基网柄菌高度运动细胞的铺展是非单调的，因此不同于铺展细胞通过一系列规则阶段的过程。对接触面积增减的量化揭示了突出和收缩力的波动，这些力主导着盘基网柄菌细胞与底物的相互作用。通过对丝状肌动蛋白与突出肌动蛋白系统中特定活性的蛋白质进行双荧光标记，阐明了这些波动的分子基础。通过从密集肌动蛋白组装积累的区域中筛选出肌球蛋白-II来建立头尾极性。肌球蛋白-IB识别突出的前端区域，Arp2/3复合体定位于从前端突出的片状伪足。冠蛋白用作肌动蛋白解聚的敏感指标，以可视化铺展细胞中聚合和解聚的微妙平衡。与网格蛋白共定位的短暂肌动蛋白斑块表明，即使底物附着的细胞表面扩张，膜内化也会发生。我们得出结论，非单调细胞铺展的特征是由运动蛋白和调节蛋白形成的时空模式所决定；这些调节蛋白在数秒的时间尺度上促进或终止肌动蛋白聚合。
