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: Cell division speed influences gene architecture

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

Cell division speed influences gene architecture

Apr 23, 2014

Speed-reading is a technique used to read quickly. It involves visual searching for clues to meaning and skipping non-essential words and/ or sentences. Similarly to humans, biological systems are sometimes ...

Secret life of cells revealed with new technique

Apr 23, 2014

(Phys.org) —A new technique that allows researchers to conduct experiments more rapidly and accurately is giving insights into the workings of proteins important in heart and muscle diseases.

In the 'slime jungle' height matters

Apr 23, 2014

(Phys.org) —In communities of microbes, akin to 'slime jungles', cells evolve not just to grow faster than their rivals but also to push themselves to the surface of colonies where they gain the best access ...

Queuing theory helps physicist understand protein recycling

Apr 22, 2014

We've all waited in line and most of us have gotten stuck in a check-out line longer than we would like. For Will Mather, assistant professor of physics and an instructor with the College of Science's Integrated Science Curriculum, ...

User comments : 0

More news stories

Breast cancer replicates brain development process

New research led by a scientist at the University of York reveals that a process that forms a key element in the development of the nervous system may also play a pivotal role in the spread of breast cancer.