Study reveals how cells use octopus-like tentacles to move around the body

Using the world’s best tweezers, a team of researchers from the University of Copenhagen has shed new light on a fundamental mechanism in all living cells that helps them explore their surroundings and even penetrate tissue. Their discovery could have implications for research into cancer, neurological diseases and more.

With octopus-like tentacles, a cell rushes toward its target, a bacterium, like a predator hunting its prey. The scene could take place in a nature program. Instead, the nanoscale tracking is observed through a microscope at the University of Copenhagen’s Niels Bohr Institute. The micrograph shows a human immune cell chasing and then engulfing a bacterium.

With their new study, a team of Danish researchers have expanded the world’s understanding of how cells use octopus-like tentacles called filopodia to move around our bodies. This discovery of how cells move had never been addressed. The study is published today in the renowned journal Nature Communications.

While the cell has no eyes or sense of smell, its surface is covered with ultra-thin filopodia resembling intricate octopus tentacles. These filopodia help a cell move toward a bacterium, while also acting as sensory feelers that identify the bacterium as prey.”

Associate Professor Poul Martin Bendix, Head of the Laboratory for Experimental Biophysics, Niels Bohr Institute

The discovery is not that filopodia act as sensory devices—which was already well known—but rather how they can rotate and behave mechanically, helping a cell move, like a cancer cell invading new tissue .

“Obviously, our results are of interest to cancer researchers. Cancer cells are known to be very invasive. And it is reasonable to assume that they particularly depend on the effectiveness of their filopodia to probe and facilitate their surroundings.’ Dispersal. So it’s conceivable that by finding ways to inhibit cancer cell filopodia, cancer growth could be stopped,” explains Associate Professor Poul Martin Bendix.

That’s why researchers from the Danish Cancer Society Research Center are 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 important for the filopodia of cancer cells.

The motor and cutting torch of the cell

According to Poul Martin Bendix, the mechanical function of filopodia can be compared to a rubber band. A rubber band has no strength when it is unwound. But when you twist it, it contracts. This combination of twisting and contraction helps a cell move in a specific direction and makes the filopodia very flexible.

“They are able to bend – twist, if you will – so they can explore the entire space around the cell, and they can even penetrate tissues around them,” says lead author Natascha Leijnse.

The mechanism discovered by the Danish researchers seems to be found in all living cells. Besides cancer cells, it is also important to study the importance of filopodia in other cell types such as embryonic stem cells and brain cells, which are highly dependent on filopodia for development.

Examine cells with the best tweezers in the world

The project involved an interdisciplinary collaboration at the Niels Bohr Institute, where Associate Professor Amin Doostmohammadi, who leads a research group simulating biologically active materials, helped model the behavior of filopodia.

“It is very interesting that Amin Doostmohammadi was able to simulate the mechanical movements that we saw through the microscope, completely independent of chemical and biological details,” explains Poul Martin Bendix.

The main reason the team was able to be the first to describe the mechanical behavior of filopodia is that the NBI has unique equipment for this type of experiment, as well as skilled researchers with vast experience working with optical tweezers. If an object is exceptionally small, it becomes impossible to hold it mechanically. However, it can be held and moved with a laser beam whose wavelength is carefully calibrated to the object to be examined. This is called optical tweezers.

“At NBI we have some of the best optical tweezers for biomechanical studies in the world. The experiments require the use of multiple optical tweezers and the simultaneous use of ultra-fine microscopy,” explains Poul Martin Bendix.

The study was led by NBI engineering scientist Younes Barooji, alongside Poul Martin Bendix and assistant professor Natascha Leijnse. The article about cell filopodia was published today in nature communication.


Magazine reference:

Leijnse, N., et al. (2022) Filopodia rotate and writhe by actively creating a twist in their actin shaft. nature communication.

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