Written by Charlotte Harrison, science writer
Cells generate mechanical forces and explore their environment using filopodia. These dynamic tubular structures contain actin and are found on the cell’s surface.
A paper published in Nature Communications shows that to facilitate cell movement, a twisting motion occurs in the actin-rich part of the filopodia structure. The discovery aids our understanding of how cells move, and could be especially important for cancer research; for example, to find ways to block the movement of a cancer cell before it invades new tissue.
The study’s lead author, Poul Martin Bendix, has a cephalopod analogy for filopodia; “[The cell] surface is equipped with ultra-slim filopodia that resemble entangled octopus tentacles. These filopodia help a cell move towards [another cell]”.
To better understand how these entangled tentacles facilitate cell movement, the authors used confocal microscopy and optical tweezers. The optical tweezers technique uses a highly focused laser beam to hold and move microscopic and sub-microscopic objects.
Twisting and buckling tentacles
Overall, the study showed that filopodia explore their 3D extracellular space by growing and shrinking, combined with axial twisting and buckling. An in-depth investigation of the twisting showed that the twisting motion takes place within the actin core inside filopodia. This twisting was observed in filopodia from a range of cell types, including stem cells and terminally differentiated cells.
Further work involving physical modelling of actin and myosin showed that the twisting force builds up within a narrow channel in the actin shaft of filopodia, and that the build-up of a sufficient twisting force causes buckling of the actin shaft. Buckling is a mechanism by which filopodia generate the traction that facilities movement. The study concludes that activity-induced twisting of the actin shaft is a general mechanism underlying key functions of filopodia.
The lead author noted that the study benefits cancer research, given the highly invasive nature of cancer cells. “It’s conceivable that by finding ways of inhibiting the filopodia of cancer cells, cancer growth can be stalled,” said Bendix. Moreover, the results are relevant to other cell types, such as embryonic stem cells and brain cells, which are highly dependent on filopodia for their development.
Image Credit: Canva