Filopodia formation induced by active mDia2/Drf3
Filopodia formation induced by active mDia2/Drf3
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DOI：
10.1111/j.1365-2818.2008.02063.x
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发表时间：
2008-09-01
期刊：
影响因子：
--
通讯作者：
Faix, J.
中科院分区：
文献类型：
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作者：
Block, J.;Stradal, T. E. B.;Faix, J.
丝状伪足是由一束平行的肌动蛋白丝组成的杆状细胞表面突起。由于丝状伪足经常从片状伪足发出，有人提出，它们完全是由片状伪足网络中产生的肌动蛋白丝的会聚和伸长形成的。然而，丝状伪足的形成没有Arp 2/3-复合物，这是必要的板状伪足的形成，表明丝状伪足中的肌动蛋白丝可能是由其他成核剂产生的。在这里，我们分析了GFP标记的全长或组成型活性变体的人PDia 2/Drf 3的异位表达的影响。与不影响细胞行为并且完全是胞质的全长分子相比，缺乏C末端调节区的活性Drf 3（Drf 3 Delta DAD）诱导丝状伪足的形成并在其尖端积累。Drf 3 Delta DAD的低表达诱导杆状或锥形丝状伪足，而过度表达导致多个棒状丝状伪足。棒充满了密集成束的肌动蛋白丝，其数量，但不是包装密度减少进一步远离尖端。有趣的是，球杆在突出超过细胞周边后经常增加宽度，这与其尖端Drf 3 Delta DAD的增加量相关。这些数据表明Drf 3诱导的丝状伪足的形成和延伸是通过肌动蛋白丝的脱核而不是会聚伸长。最后，Drf 3 Delta DAD还诱导了异常的形成。片状伪足样结构，其中包含片状伪足标记和突出的丝状伪足蛋白肌成束蛋白。微阵列分析揭示了不同常用细胞系中高度可变的Drf 3表达水平。反映了需要更详细地分析不同的formins在肌动蛋白细胞骨架周转和不同细胞类型中的功能。
Filopodia Eire rod-shaped cell surface protrusions composed of a parallel bundle of actin filaments. Since filopodia frequently emanate from lamellipodia, it has been proposed that they form exclusively by the convergence and elongation of actin filaments generated in lamellipodia networks. However, filopodia form without Arp2/3-complex, which is essential for lamellipodia formation, indicating that actin filaments in filopodia may be generated by other nucleators. Here we analyzed the effects of ectopic expression of GFP-tagged full length or a constitutively active variant of the human formin mDia2/Drf3. By contrast to the full-length molecule, which did not affect cell behaviour and was entirely cytosolic, active Drf3 lacking the C-terminal regulatory region (Drf3 Delta DAD) induced the formation of filopodia and accumulated at their tips. Low expression of Drf3 Delta DAD induced rod-shaped or tapered filopodia, whereas over-expression resulted in multiple, club-shaped filopodia. The clubs were filled with densely bundled actin filaments, whose number but not packing density decreased further away from the tip. Interestingly, clubs frequently increased in width after protrusion beyond the cell periphery, which correlated with increased amounts of Drf3 Delta DAD at their tips. These data suggest Drf3-induced filopodia form and extend by de now nucleation of actin filaments instead of convergent elongation. Finally, Drf3 Delta DAD also induced the formation of unusual. lamellipodia-like structures, which contained both lamellipodial markers and the prominent filopodial protein fascin. Microarray analyses revealed highly variable Drf3 expression levels in different commonly used cell lines. reflecting the need for more detailed analyses of the functions of distinct formins in actin cytoskeleton turnover and different cell types.