Arp2/3 and Mena/VASP Require Profilin 1 for Actin Network Assembly at the Leading Edge
Arp2/3 and Mena/VASP Require Profilin 1 for Actin Network Assembly at the Leading Edge
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DOI：
10.1016/j.cub.2020.04.085
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发表时间：
2020-07-20
期刊：
影响因子：
9.2
通讯作者：
Vitriol，Eric A.
中科院分区：
文献类型：
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作者：
Skruber，Kristen;Warp，Peyton;Vitriol，Eric A.
细胞具有多种类型的肌动蛋白结构，它们必须从一个共同的单体库组装起来。然而，它仍然知之甚少单体是如何分布到不同的细丝网络之间和共享。简化的模型系统表明，单体是有限的和异质的，这改变了肌动蛋白网络组装通过偏向聚合和网络间的竞争。然而，很少有人知道单体如何影响复杂的肌动蛋白结构，其中不同的网络竞争单体重叠，功能上相互依赖。一个例子是迁移细胞的前缘，其中包含由多个组装因子生成的细丝网络。前缘动态切换形成不同的肌动蛋白结构，如板状伪足或丝状伪足，通过改变这些组装因子的活动的平衡。在这里，我们试图确定单体结合蛋白profilin 1（PFN 1）如何控制哺乳动物细胞中肌动蛋白的组装和组织。PFN 1敲除细胞中的肌动蛋白聚合被严重破坏，特别是在前沿，Arp 2/3和Mena/VASP为基础的细丝组装被抑制。进一步的研究表明，在PFN 1缺失的情况下，Arp 2/3不再定位于前缘，Mena/VASP无功能。此外，我们发现，Arp 2/3和Mena/VASP网络之间的网络竞争和合作的离散阶段存在于不同的PFN 1浓度。低水平的PFN 1导致丝状伪足只在前缘形成，而较高的浓度抑制丝状伪足，有利于片状伪足和前丝状伪足束。这些结果表明，肌动蛋白结构的巨大变化可以简单地通过修改PFN 1的可用性。
Cells have many types of actin structures, which must assemble from a common monomer pool. Yet, it remains poorly understood how monomers are distributed to and shared between different filament networks. Simplified model systems suggest that monomers are limited and heterogeneous, which alters actin network assembly through biased polymerization and internetwork competition. However, less is known about how monomers influence complex actin structures, where different networks competing for monomers overlap and are functionally interdependent. One example is the leading edge of migrating cells, which contains filament networks generated by multiple assembly factors. The leading edge dynamically switches between the formation of different actin structures, such as lamellipodia or filopodia, by altering the balance of these assembly factors' activities. Here, we sought to determine how the monomer-binding protein profilin 1 (PFN1) controls the assembly and organization of actin in mammalian cells. Actin polymerization in PFN1 knockout cells was severely disrupted, particularly at the leading edge, where both Arp2/3 and Mena/VASP-based filament assembly was inhibited. Further studies showed that in the absence of PFN1, Arp2/3 no longer localizes to the leading edge and Mena/VASP is non-functional. Additionally, we discovered that discrete stages of internetwork competition and collaboration between Arp2/3 and Mena/VASP networks exist at different PFN1 concentrations. Low levels of PFN1 caused filopodia to form exclusively at the leading edge, while higher concentrations inhibited filopodia and favored lamellipodia and pre-filopodia bundles. These results demonstrate that dramatic changes to actin architecture can be made simply by modifying PFN1 availability.