Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stability without junctions

28.12.2016

Cadherin prevents cortical deformation

Scientists from the Mechanobiology Institute, Singapore (MBI) at the National University of Singapore (NUS) have discovered that cadherin clusters, which are well known for forming junctions between cells, also play a role in stabilising the cell cortex. The study was published in the scientific journal Current Biology on 15 December 2016.


Figure: Surface and equatorial plane views of the C. elegans embryo. Non-junctional and non-adhesive HMR-1 clusters (green dots) are visible on the surface of a single cell and also on both cells following cell division. A belt of HMR-1 forming cell-cell junctions is observed between the 2 daughter cells (white-green line).

Credit: Mechanobiology Institute, National University of Singapore

A new role for cadherin

Multicellular life depends on the ability of cells to adhere to one another. This takes place through cell-cell junctions, protein complexes that physically connect cells together. At the core of cell-cell junctions is the protein cadherin, which spans across the cell membrane, sticking out of the cell to connect to cadherins on neighbouring cells. Cadherin also attaches to the internal cell cortex, a dense layer of proteins underneath the cell membrane which has two major components: the filament-forming protein actin that provides structural stability, and the motor protein myosin that enables dynamic movement of the cortex depending on the needs of the cell. This physical bridge between cells enables the transmission of both mechanical and biochemical signals across multicellular tissues.

However, scientists have observed clusters of cadherin on the cell surface which are not involved in cell-cell junctions. While it has been speculated that these non-junctional and non-adhesive cadherin clusters are being kept in reserve in order to strengthen or create new cell-cell junctions, the actual function of these clusters remained unknown.

With their expertise in cell adhesion and developmental biology, Principal Investigator Assistant Professor Ronen Zaidel-Bar and Research Fellow Dr Anup Padmanabhan of MBI used embryos from the nematode C. elegans to probe the function of these non-junctional cadherin clusters. After tagging the worm equivalent of cadherin, a protein named HMR-1, with a fluorescent marker, they were able to follow its location and movement by live imaging.

Focusing their investigation on the zygote, the single fertilised egg cell that develops into an embryo, they discovered that HMR-1 formed non-junctional, non-adhesive clusters similar to cadherin. Even though these non-junctional HMR-1 clusters did not form connections outside of the cell, they still remained internally associated with actin filaments of the cell cortex, but not the myosin motor proteins. In fact, the presence of non-junctional HMR-1 clusters prevents cortical accumulation of myosin and decreases the contractile activity of proteins that drive cortical movement.

In order to determine whether non-junctional HMR-1 affected cytokinesis - the physical process by which the cell cortex rotates and contracts to divide the cell into two - the scientists genetically altered the level of HMR-1. Reducing the amount of HMR-1 resulted in faster cytokinesis while increasing HMR-1 levels slowed it down, demonstrating that these non-junctional clusters have a key function in regulating movement of the cell cortex. Analysis of cortical dynamics during cell division revealed that HMR-1 clusters attached to the actin filaments effectively provided drag against cytoskeleton movement, by acting as structural anchors lodged in the cell membrane. The importance of this anchoring in maintaining cell integrity became clear following extended observation of embryos with reduced levels of HMR-1, which were vulnerable to cortical splitting, where a segment of cortex tears away from the cell membrane.

In essence, the non-junctional HMR-1 clusters can be thought of as cellular staples that help secure the cortex to the cell surface. The friction from the clusters stabilises the cortex and slows down cortical flow, preventing dramatic cortical deformation, while allowing enough cortical movement for fundamental processes like cytokinesis.

This new discovery means that scientists must re-evaluate their understanding of cadherin. The importance of non-junctional cadherin in stabilising the cell cortex must now be considered along with the classical function of cadherin in maintaining cell-cell junctions. This fresh perspective may unlock new avenues of investigation regarding the role of cadherin in health and disease.

Media Contact

Amal Naquiah
amal@nus.edu.sg
65-651-65125

 @NUSingapore

http://www.nus.edu.sg/ 

Amal Naquiah | EurekAlert!

Further reports about: MBI actin filaments cadherin cell membrane cell surface cortical filaments

More articles from Life Sciences:

nachricht Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology

nachricht The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>