Endocytosis is simpler than suspected

Jul 07, 2011
Endocytosis is simpler than suspected
Credit: John Heuser

A protein by the name of clathrin plays a key part in endocytosis, the process by which living cells absorb large molecules. The protein can form “cages”, in which these molecules become trapped. Until recently, the details of this process were not fully understood. Using computer simulations, researchers at the University of Twente, The Netherlands, have now uncovered the secrets of this mechanism. It seems that the traditional view of endocytosis was overly complex.

Cells use to absorb large . The cell membrane folds inwards, creating a pocket, which then pinches off to form a vesicle containing the target molecule. This vesicle is then transported to the site inside the cell where it is needed.

Clathrin has long been known to play a pivotal role in the process of wrapping up these trapped molecules. The protein's part in this process is to form "cages" around a piece of cell membrane containing the target molecule. These cages are similar in structure to old-fashioned footballs, consisting only of pentagons and hexagons. Clathrin complexes were already known to form flat, honeycomb-like structures in , consisting only of hexagons. Until recently, however, it was not known how clathrin complexes switch from one structure to the other. As a result, the practical aspects of the process of endocytosis were also poorly understood. The most important question in this regard is how pentagons are suddenly introduced into a structure consisting of only hexagons. Scientists have been researching this matter for forty years.

The previous hypotheses were all based on complex mechanisms involving numerous intermediate steps. Using computer simulations, researchers at the University of Twente have now shown that the mechanism is much simpler than people had previously assumed. The study revealed that, when the flat structure starts to bend, tensions within the grid can cause a small highly-curved piece to break off. Successive individual clathrin molecules then bind to the curved piece until the protein cage is complete. The findings are consistent with previous studies in which detached, curved structures had been observed in special electron microscope images. However, previous interpretations of these images were incorrect.

The study was conducted by Dr. Wouter den Otter and Prof. Wim Briels of the Computational BioPhysics group at the University of Twente. After entering details of clathrin's properties into software of their own design, they can simulate the processes involved in the formation of cages. Their results will soon be published in Traffic, a leading scientific journal in the field of molecular transport by membranes. As statistical physicists, the researchers take great pride in the fact that they are able to publish their work in a biological journal. "It shows that our work is relevant to them".

Explore further: Researchers successfully clone adult human stem cells

add to favorites email to friend print save as pdf

Related Stories

Cow Brain Protein May Hold Alternative Energy Promise

Apr 20, 2010

(PhysOrg.com) -- Of all the ideas that hold promise in alternative energy, cow brains are an odd candidate. They do not fit into the list of usual plant-based subjects, such as corn or switch grass. But cow ...

A turning point for young neurons

Aug 03, 2010

During neural development, newborn neurons extend axons toward distant targets then form connections with other cells. This process depends on the growth cone, a dynamic structure at the growing axon tip of ...

Cells use import machinery to export their goods as well

Jul 03, 2009

(PhysOrg.com) -- In the bustling economy of the cell, little bubbles called vesicles serve as container ships, ferrying cargo to and from the port — the cell membrane. Some of these vesicles, called post-Golgi vesicles, ...

Recommended for you

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

Apr 18, 2014

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

For resetting circadian rhythms, neural cooperation is key

Apr 17, 2014

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...