A dynamic formin-dependent deep F-actin network in axons.
A dynamic formin-dependent deep F-actin network in axons.
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DOI：
10.1083/jcb.201506110
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发表时间：
2015-08-03
期刊：
影响因子：
--
通讯作者：
Roy S
中科院分区：
文献类型：
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作者：
Ganguly A;Tang Y;Wang L;Ladt K;Loi J;Dargent B;Leterrier C;Roy S
F-肌动蛋白选择性探针、定量工具和超分辨率显微镜的低光实时成像揭示了轴突中动态的、依赖于形式的深层 F-肌动蛋白细胞骨架网络。尽管神经元生长锥处的肌动蛋白已得到充分研究，但人们对沿着轴突轴和突触前纽扣的肌动蛋白组织和动力学知之甚少。使用选择性标记丝状肌动蛋白（F-肌动蛋白）的探针，我们发现了沿轴突的焦点“肌动蛋白热点”（间隔约 3-4 µm），肌动蛋白在此进行连续组装/拆卸。这些病灶是肌动蛋白剧烈聚合的巢穴，产生沿着轴突双向喷射的长丝——我们称之为“肌动蛋白痕迹”的现象。除了最近描述的质膜下“肌动蛋白环”之外，超分辨率显微镜还揭示了轴突内深层肌动蛋白丝。 F-肌动蛋白热点与固定轴突内体共定位，并且阻断囊泡运输会减少肌动蛋白轨迹，这表明囊泡和 F-肌动蛋白动力学之间存在机制联系。肌动蛋白轨迹依赖于福尔马林，但不依赖于 Arp2/3，有助于丰富突触前按钮处的肌动蛋白。最后，福尔明抑制会极大地破坏突触循环。总的来说，现有数据表明轴突中存在两层 F-肌动蛋白组织，稳定的“肌动蛋白环”为质膜提供机械支撑，动态的“肌动蛋白轨迹”生成具有假定生理作用的灵活的细胞骨架网络。
Low-light live imaging of F-actin–selective probes, quantitative tools, and super-resolution microscopy reveals a dynamic, formin-dependent deep F-actin cytoskeletal network in axons. Although actin at neuronal growth cones is well-studied, much less is known about actin organization and dynamics along axon shafts and presynaptic boutons. Using probes that selectively label filamentous-actin (F-actin), we found focal “actin hotspots” along axons—spaced ∼3–4 µm apart—where actin undergoes continuous assembly/disassembly. These foci are a nidus for vigorous actin polymerization, generating long filaments spurting bidirectionally along axons—a phenomenon we call “actin trails.” Super-resolution microscopy reveals intra-axonal deep actin filaments in addition to the subplasmalemmal “actin rings” described recently. F-actin hotspots colocalize with stationary axonal endosomes, and blocking vesicle transport diminishes the actin trails, suggesting mechanistic links between vesicles and F-actin kinetics. Actin trails are formin—but not Arp2/3—dependent and help enrich actin at presynaptic boutons. Finally, formin inhibition dramatically disrupts synaptic recycling. Collectively, available data suggest a two-tier F-actin organization in axons, with stable “actin rings” providing mechanical support to the plasma membrane and dynamic "actin trails" generating a flexible cytoskeletal network with putative physiological roles.