Leijnse Natascha, Oddershede Lene B, Bendix Poul M
Niels Bohr Institute and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark.
Niels Bohr Institute and
Proc Natl Acad Sci U S A. 2015 Jan 6;112(1):136-41. doi: 10.1073/pnas.1411761112. Epub 2014 Dec 22.
Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell-cell communication. Filopodia contain cross-linked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.
细胞可通过丝状伪足与周围环境相互作用，丝状伪足是延伸至细胞体之外的膜性突起。在诸如运动、侵袭和细胞间通讯等动态细胞过程中，丝状伪足至关重要。丝状伪足含有交联的肌动蛋白丝，通过诸如整合素等蛋白质连接体附着于周围细胞膜。这些肌动蛋白丝被认为在力传导、弯曲和旋转中起关键作用。我们通过对膜性突起中的F-肌动蛋白进行同步力谱分析和共聚焦成像，研究了丝状伪足内的肌动蛋白是否以及如何负责丝状伪足的动态变化。观察到肌动蛋白轴周期性地发生螺旋盘绕和旋转运动，这与丝状伪足内肌动蛋白的逆行运动同时发生。发现细胞会缩回附着在丝状伪足尖端的珠子，并且缩回与肌动蛋白轴的旋转和盘绕相关。这些结果提示了一种先前未被识别的机制，通过该机制细胞可利用丝状伪足肌动蛋白轴的旋转来诱导盘绕，进而使丝状伪足肌动蛋白束轴向缩短。
