Nav: Home

Lane change in the cytoskeleton

February 12, 2020

Many amphibians and fish are able to change their color in order to better adapt to their environment. Munich-based scientists have now investigated the molecular mechanisms in the cytoskeleton necessary for this and revealed potential evolutionary paths.

All cells of higher organisms are permeated by a cytoskeleton that essentially consists of actin filaments and small protein tubes called microtubules. For a long time science considered the actin or microtubule networks as independent systems.

Today it is known that the two network types communicate with each other and thereby make vital cellular processes such as cell division or cell migration possible in the first place. However, it was still unknown how this collaboration works at the molecular level.

Dr. Zeynep Ökten from the Chair of Molecular Biophysics at the Technical University of Munich (TUM) and Erwin Frey, Professor of Statistical and Biological Physics at the Ludwig-Maximilians-Universität München - with their teams - have now for the first time identified a molecular mechanism by the example of change of color among animals which explains the communication between both network systems, and revealed potential evolutionary paths.

Transport pathways in the cell

Many functional components of a cell, such as the organelles, must be brought to the right place at the right time in the cell. For this purpose they are actively transported by molecular motors on the microtubules and actin filaments.

Studies have shown that motors which were long regarded as highly specific for one of the two network systems can in reality also be redirected to the other filament type. In mice, for example, scientists found an adapter protein that regulates this redirection.

Myosin transports its freight via the actin network, but the adapter protein also interacts with the microtubules and can redirect the transport on this network. Which network is preferred is controlled by a chemical modification to a specific binding site of the adapter protein.

Adapter protein with shifting mode

Fish and amphibians also have a protein corresponding to the mammalian adapter. The evolutionarily older fish and amphibians use it to adapt their skin color to environmental factors by redirecting pigment organelles within specialized cells.

That is why the research team used zebrafish and clawed frogs for experimental investigations in Ökten's laboratory to examine the origin and the molecular mechanisms of interaction between the microtubule network and the actin network.

Evolution of a molecular switch

The scientists found out that the mouse adapter protein as well as the clawed frog adapter protein has a specific domain which enables the switching between the transport of actin and microtubules.

Zebrafish, the evolutionarily oldest of examined animals, do not yet have this domain. "Here the motor proteins which move the pigments organelles are subject to different regulatory mechanisms, and there is no interaction between the different cytoskeleton networks", says Ökten.

"In contrast, switching between the networks is absolutely necessary among the clawed frogs so that the animal can change color - and this ability to switch has also been preserved in the further course of evolution from amphibian to higher vertebrates", explains Ökten further.

Theoretical model explains pigment redistribution

Moreover, the experimental results showed that the environmental signals which bring about the redistribution of pigment organelles in the organism of clawed frogs are associated with a change of probability with which the individual motor proteins from the actin filaments switch to the microtubule filaments.

"We have developed a theoretical model that correlates the switching probability of an individual motor protein with the cell-wide redistribution of pigment organelles", says Frey. Computer simulations revealed that the variation of switching probability is actually sufficient as the only parameter to provide a redistribution of organelles in the simulated cells.

"It is notable that our simulations remarkably precisely reflect the redistribution of organelles observed in the living organism", says Frey. "As a result, the theoretical approach underscores the functional importance of experimental results, and shows that the interaction between actin network and microtubule network, which has developed among lower vertebrates, exhibits a particularly high regulatory efficiency."
-end-
The research was funded by the European Research Council (ERC) and the German Research Foundation (DFG).

Publication:

Molecular Underpinnings of Cytoskeletal Crosstalk Angela Oberhofer, Emanuel Reithmann, Peter Spieler, Willi L. Stepp, Dennis Zimmermann, Bettina Schmid, Erwin Frey and Zeynep Ökten, PNAS 10.02.2020 - DOI: 0.1073/pnas.1917964117

Technical University of Munich (TUM)

Related Protein Articles:

A direct protein-to-protein binding couples cell survival to cell proliferation
The regulators of apoptosis watch over cell replication and the decision to enter the cell cycle.
A protein that controls inflammation
A study by the research team of Prof. Geert van Loo (VIB-UGent Center for Inflammation Research) has unraveled a critical molecular mechanism behind autoimmune and inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and psoriasis.
Resurrecting ancient protein partners reveals origin of protein regulation
After reconstructing the ancient forms of two cellular proteins, scientists discovered the earliest known instance of a complex form of protein regulation.
Sensing protein wellbeing
The folding state of the proteins in live cells often reflect the cell's general health.
Protein injections in medicine
One day, medical compounds could be introduced into cells with the help of bacterial toxins.
Discovery of an unusual protein
Scientists from Bremen discover an unusual protein playing a significant role in the Earth's nitrogen cycle.
Protein aggregation: Protein assemblies relevant not only for neurodegenerative disease
Amyloid fibrils play a crucial role in neurodegenerative illnesses. Scientists from Heinrich Heine University Düsseldorf (HHU) and Forschungszentrum Jülich have now been able to use cryo-electron microscopy (cryo-EM) to decode the spatial structure of the fibrils that are formed from PI3K SH3 domains - an important model system for research.
Old protein, new tricks: UMD connects a protein to antibody immunity for the first time
How can a protein be a major contributor in the development of birth defects, and also hold the potential to provide symptom relief from autoimmune diseases like lupus?
Infection-fighting protein also senses protein misfolding in non-infected cells
Researchers at the University of Toronto have uncovered an immune mechanism by which host cells combat bacterial infection, and at the same time found that a protein crucial to that process can sense and respond to misfolded proteins in all mammalian cells.
Quorn protein builds muscle better than milk protein
A study from the University of Exeter has found that mycoprotein, the protein-rich food source that is unique to Quorn products, stimulates post-exercise muscle building to a greater extent than milk protein.
More Protein News and Protein Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.