New findings clarify how cells use octopus-like tentacles called filopodia to move around in our bodies.
“While the cell doesn’t have eyes or a sense of smell, its surface is equipped with ultra-slim filopodia that resemble entangled octopus tentacles. These filopodia help a cell move towards a bacterium, and at the same time, act as sensory feelers that identify the bacterium as a prey,” explains associate professor Poul Martin Bendix, head of the laboratory for experimental biophysics at the University of Copenhagen’s Niels Bohr Institute.
The discovery is not that filopodia act as sensory devices—which was already well established—but rather about how they can rotate and behave mechanically, which helps a cell move, as when a cancer cell invades new tissue.
“Obviously, our results are of interest to cancer researchers. Cancer cells are noted for their being highly invasive. And, it is reasonable to believe that they are especially dependent on the efficacy of their filopodia, in terms of examining their surroundings and facilitating their spread. So, it’s conceivable that by finding ways of inhibiting the filopodia of cancer cells, cancer growth can be stalled,” explains Bendix.
For this reason, researchers from the Danish Cancer Society Research Center are a part of the team behind the discovery. Among other things, the cancer researchers are interested in whether switching off the production of certain proteins can inhibit the transport mechanisms which are important for the filopodia of cancer cells.
According to Bendix, the mechanical function of filopodia is comparable to a rubber band. Untwisted, a rubber band has no power. But if you twist it, it contracts. This combination of twisting and contraction helps a cell move directionally and makes the filopodia very flexible.
“They’re able to bend—twist, if you will—in a way that allows them to explore the entire space around the cell, and they can even penetrate tissues in their environment,” says Natascha Leijnse, lead author of the paper in Nature Communications.
The mechanism appears to be found in all living cells. Besides cancer cells, it is also relevant to study the importance of filopodia in other types of cells, such as embryonic stem cells and brain cells, which depend on filopodia for their development.
For the project, associate professor Amin Doostmohammadi, who heads a research group that simulates biologically active materials, modeled filopodia behavior.
“It is very interesting that Amin Doostmohammadi could simulate the mechanical movements we witnessed through the microscope, completely independent of chemical and biological details,” explains Bendix.
Describing the mechanical behavior of filopodia depended on the researcher’s access to NBI equipment called optical tweezers. When an object is extraordinarily small, it becomes impossible to hold onto it mechanically. Instead, researchers can hold and move the object with a laser beam with a carefully calibrated wavelength.
“The experiments require the use of several optical tweezers and the simultaneous deployment of ultra-fine microscopy,” explains Bendix.
Source: University of Copenhagen