High Rac1 activity is functionally translated into cytosolic structures with unique nanoscale cytoskeletal architecture
High Rac1 activity is functionally translated into cytosolic structures with unique nanoscale cytoskeletal architecture
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DOI：
10.1073/pnas.1808830116
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发表时间：
2019-01-22
影响因子：
11.1
通讯作者：
Hanein, Dorit
中科院分区：
文献类型：
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作者：
Marston, Daniel J.;Anderson, Karen L.;Hanein, Dorit
Rac1激活是调节极化细胞迁移的信号传导途径的核心。到目前为止，还不可能在分子水平上直接探索Rac1激活引发的结构变化。在这里，通过一个多尺度的成像工作流程，结合Rac1动态与电子cryotomography的生物传感器成像，我们确定，在拥挤的环境中的真核细胞，一个独特的纳米级架构的灵活的，信号依赖性肌动蛋白结构。在具有高Rac 1活性的细胞区域中，我们发现了一种结构体系，该结构体系从腹侧膜跨越到该膜上方约60 nm的高度，由方向不对齐的密集排列的肌动蛋白丝组成，大多数短于150 nm。这种独特的Rac1诱导的形态是显着不同的树突状网络架构中，相对较短的细丝从现有的，较长的肌动蛋白丝发出。这些Rac1介导的支架组件缺乏大的大分子，如核糖体或其他细丝类型，这些大分子在成像体积的外围和其余部分内是丰富的。Rac1活性的停止诱导了一个完整而快速的结构转变，导致在150 s内没有可检测到的这种结构的残留物，为GTdR信号事件诱导的快速肌动蛋白丝网络周转提供了直接的结构证据。很容易推测，这种高度动态的纳米支架系统对局部空间线索很敏感，因此有助于支持更复杂的肌动蛋白丝结构的形成，例如上皮间质转化所要求的结构，或者通过完全消散来重置该区域。
Rac1 activation is at the core of signaling pathways regulating polarized cell migration. So far, it has not been possible to directly explore the structural changes triggered by Rac1 activation at the molecular level. Here, through a multiscale imaging workflow that combines biosensor imaging of Rac1 dynamics with electron cryotomography, we identified, within the crowded environment of eukaryotic cells, a unique nanoscale architecture of a flexible, signal-dependent actin structure. In cell regions with high Rac1 activity, we found a structural regime that spans from the ventral membrane up to a height of similar to 60 nm above that membrane, composed of directionally unaligned, densely packed actin filaments, most shorter than 150 nm. This unique Rac1-induced morphology is markedly different from the dendritic network architecture in which relatively short filaments emanate from existing, longer actin filaments. These Rac1-mediated scaffold assemblies are devoid of large macromolecules such as ribosomes or other filament types, which are abundant at the periphery and within the remainder of the imaged volumes. Cessation of Rac1 activity induces a complete and rapid structural transition, leading to the absence of detectable remnants of such structures within 150 s, providing direct structural evidence for rapid actin filament network turnover induced by GTPase signaling events. It is tempting to speculate that this highly dynamical nanoscaffold system is sensitive to local spatial cues, thus serving to support the formation of more complex actin filament architectures-such as those mandated by epithelialmesenchymal transition, for example-or resetting the region by completely dissipating.