Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New measures taken at UNIGE call theories about endocytosis into question

19.02.2015

Where does the force that draws the membrane of the eukaryotic cell inwards come from?

Cellular biology still harbors mysteries. Notably, there is no unequivocal explanation behind endocytosis, the biological process that allows exchanges between a cell and its environment. Two hypotheses prevail for explaining how the wall caves in and forms transport vesicles: either the initial impetus is due to a scaffold-like structure which the soccer ball-shaped clathrin proteins build between themselves, or clathrin's role is minor, and it is other, «adaptor» proteins who exert pressure on the cell wall until endocytosis begins. One recently completed study by the Faculty of Science at the University of Geneva (UNIGE) reconciles the two theories, suggesting a balance between forces present: clathrin proteins are only slightly more influential than the others, and it is a clever combination of physical mechanisms that contributes to creating favorable conditions for the deformation of the membrane. These conclusions captured the interest of the editors of Nature Communications, who just published them.


This is an illustration of a protein of clathrine, with its caracteristic form.

Credit: University of Geneva

In vitro procedures by researchers in UNIGE's Department of Biochemistry shed new light on the phenomenon of endocytosis, the biological cycle that takes place at the membrane level, and ends with the formation of the transport compartments necessary for external exchanges.

During endocytosis, the cell membrane of eukaryotic organisms becomes deformed, puckering and caving in, creating vesicles for transporting elements - like ions, nutrients, and signals - that are necessary for life. This compartment is deployed from the membrane towards the inside of the cell; its creation implies the use of a lot of energy, and a significant physical force. Two hypotheses provide different explanations for its origins.

A suction cup shaped like a soccer ball, or strong «adaptors» that act as wedges?

In order to explain the genesis of the phenomenon, the scientific community that specializes in the study of endocytosis offers two dominant theories: the first, in which clathrins, proteins shaped like soccer balls that build lego-like structures with each other, act as a suction cup that can suck in the cellular membrane and make it curved. The other theory gives the predominant role to other «adaptor» proteins, which work with clathrins, and deform the membrane in the same way that a wedge is used to split wood.

In Aurélien Roux's laboratory, Saleem Mohammed's delicate processes turn these perspectives upside down by reconciling the two hypotheses: it is not that the energy deployed by clathrin proteins to build scaffold-like structures between each other exceeds what is needed to deform the membrane. Nor that the adaptors broach the membrane by themselves.

Forces balance to open the membrane

Although clathrin remains the main agent behind endocytosis, it doesn't act as a steamroller. Its influence is more subtle than the suction cup hypothesis posits. This assembly protein's energy will join that of the adaptors, which are binding proteins, to make the cellular membrane curve inwards. The membrane has several special characteristics of its own, making it an endlessly fascinating field of research. Its plasticity and elasticity resemble that of human skin, while it has the kind of fluidity and malleability of a soap bubble. Impermeable and self-healing, the cellular membrane guarantees the integrity of the eukaryotic cell.

Physics could therefore be a great help when studying the biology of such a complex ensemble of lipids, sugars, and proteins. This is the multi-disciplinary approach favored by Aurélien Roux, who states that «Cellular biology is undergoing a revolution in terms of methodology: the quantitative aspect plays a significant role, and mathematics and physics help bring about new models for understanding the subtleties of life.»

Media Contact

Aurélien Roux
aurelien.roux@unige.ch
41-789-215-455

 @UNIGEnews

http://www.unige.ch 

Aurélien Roux | EurekAlert!

More articles from Life Sciences:

nachricht Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung

nachricht Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg

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

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

13.07.2018 | Event News

Research finds new molecular structures in boron-based nanoclusters

13.07.2018 | Materials Sciences

Algae Have Land Genes

13.07.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>