Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
Science. 2010 Sep 10;329(5997):1341-5. doi: 10.1126/science.1191710.
Filopodia are finger-like protrusive structures, containing actin bundles. By incubating frog egg extracts with supported lipid bilayers containing phosphatidylinositol 4,5 bisphosphate, we have reconstituted the assembly of filopodia-like structures (FLSs). The actin assembles into parallel bundles, and known filopodial components localize to the tip and shaft. The filopodia tip complexes self-organize--they are not templated by preexisting membrane microdomains. The F-BAR domain protein toca-1 recruits N-WASP, followed by the Arp2/3 complex and actin. Elongation proteins, Diaphanous-related formin, VASP, and fascin are recruited subsequently. Although the Arp2/3 complex is required for FLS initiation, it is not essential for elongation, which involves formins. We propose that filopodia form via clustering of Arp2/3 complex activators, self-assembly of filopodial tip complexes on the membrane, and outgrowth of actin bundles.
微丝足是一种指状的突起结构，包含肌动蛋白束。通过用含有磷脂酰肌醇 4,5 二磷酸的支持脂双层孵育青蛙卵提取物，我们重新组装了类似丝状伪足的结构（FLS）。肌动蛋白组装成平行束，并且已知的丝状伪足成分定位于尖端和轴。丝状伪足尖端复合物自组织形成——它们不是由预先存在的膜微区模板化的。F-BAR 结构域蛋白 toca-1 招募 N-WASP，随后是 Arp2/3 复合物和肌动蛋白。随后招募伸长蛋白、Diaphanous 相关formin、VASP 和 fascin。尽管 Arp2/3 复合物对于 FLS 的起始是必需的，但对于伸长来说并不是必需的，这涉及到formin。我们提出，丝状伪足通过 Arp2/3 复合物激活剂的聚集、丝状伪足尖端复合物在膜上的自组装以及肌动蛋白束的延伸而形成。
