Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The body's own recycling system

12.10.2012
Researchers discover "molecular emergency brake" in charge of regulating self-digestion

Times of distress literally eat away at the core of starving cells: They start to digest their own parts and recycle them for metabolic purposes. This process – called autophagy – also plays a role in immune defense. Here, it is switched on to eliminate pathogens that have invaded the body.


Ralf Höcker/HZI

Using a microscope, the researchers are able to zoom in on the cells: If autophagy proceeds undisturbed, they are able to observe little digestive bubbles, shown in red, inside of which material is being degraded (left). If the final step is blocked, autophagosomes accumulate inside the cell, shown here in green (right). The dark circular area at the center is the nucleus.

Now, Prof. Ingo Schmitz at the Helmholtz Centre for Infection Research (HZI) in Braunschweig, Germany, together with a team of researchers, has discovered that a "molecular brake" regulates autophagy. They published their findings in the scientific journal, Cell Death & Differentiation.

Almost everything that happens inside a cell, including autophagy, is tightly regulated on a biochemical level. Like that, the cell makes sure that processes only take place when they are needed and that they are shut off when the need has expired. "Inside the cell, there exists a network of molecules. Between them, information is constantly being exchanged," says Schmitz, head of the research group “Systems-oriented Immunology and Inflammation Research” at HZI, who also holds a chair at the Otto von Guericke University in Magdeburg.

"In a way, it looks like a big city subway map." However, only the starting point and the destination of a given "cellular subway line" are relatively easy to study. To explore the different stops along the way, is more difficult. But because other lines intersect and interact with each other at these points, it is very exciting for researchers to decode all molecules involved in these signal transduction processes. It also helps them better understand diseases caused by defects in these information highways.

What exactly happens on a molecular level during the later stages of autophagy was largely unknown – until now. Schmitz and his team, along with researchers from the Otto von Guericke University Magdeburg, the Heinrich Heine University Düsseldorf, the Tübingen University, and the Temple University School of Medicine in Philadelphia, USA, have decoded one part of the molecular subway map.

Under the microscope, researchers can observe how larger-sized cellular components destined for degradation and recycling are enclosed within a small bubble, the so-called autophagosome. This structure then fuses with yet another little bubble, which digests the autophagosome's contents. "Autophagy is a survival mechanism to ensure that the cell is able to obtain the necessary nutrients during times of starvation," explains Schmitz.

For their studies, the scientists stained certain molecules and autophagosomes inside cells. This allowed them to observe microscopically which molecules are in charge of regulating the formation of the little digestive bubbles. To prompt self-digestion, they either starved the cells or simulated an infection. In the process, they discovered that the cells simultaneously also turned on autophagy-inhibiting molecules – "like some kind of emergency brake that ensures autophagy doesn't get out of control." Such negative feedback loops are not unusual for cells, they frequently help prevent overshooting reactions.

The researchers managed to identify the components of this feedback loop and found a protein called p38 to play a key role in the process. The scientists were especially surprised to observe p38 proteins on the surface of the autophagosomes. Normally, this protein is localized inside the nucleus where it gets switched on whenever the cell is under stress. On the surfaces of autophagosomes, p38 performs a very different job: It alters another molecule, called Atg5, to get it to block the final step of autophagy, involving formation of the little digestive bubble. Autophagy is inhibited, and, essentially, the cell pulls the "molecular emergency brake."

If it didn't, diseases could potentially result. As such, defective molecules of the Atg family have been implicated in the etiology of the inflammatory bowel disease, Morbus Crohn. "Looking at Atg5-deficient mice, which die of nutrient-deficiency shortly after they are born, we see just how important it is to tightly regulate autophagy," emphasizes Ralf Höcker, one of the study's first authors. As so often, it is important to find the right balance, in this case, between too much and too little self-digestion.

Original publication:
Eric Keil, Ralf Höcker, Marc Schuster, Frank Essmann, Nana Ueffing, Barbara Hoffman, Dan A. Liebermann, Klaus Pfeffer, Klaus Schulze-Osthoff, Ingo Schmitz
Phosphorylation of Atg5 by the Gadd45b-MEKK4-p38 pathway inhibits autophagy
Cell Death & Differentiation, 2012
doi:10.1038/cdd.2012.129
http://www.nature.com/cdd/journal/vaop/ncurrent/abs/cdd2012129a.html
The research group "Systems-oriented Immunology and Inflammation Research" explores the molecular processes that make immune cells tolerant to the body’s own tissues. This includes especially the cellular suicide program apoptosis.
The Helmholtz Centre for Infection Research (HZI):
The Helmholtz Centre for Infection Research contributes to the achievement of the goals of the Helmholtz Association of German Research Centres and to the successful implementation of the research strategy of the German Federal Government. The goal is to meet the challenges in infection research and make a contribution to public health with new strategies for the prevention and therapy of infectious diseases.
The Otto von Guericke University Magdeburg:
One of the Otto von Guericke University Magdeburg Medical Faculty’s research emphases is "Immunology including molecular medicine relating to inflammation". The goal is to develop new therapeutic approaches and deliver them to the patient.

Dr. Birgit Manno | Helmholtz-Zentrum
Further information:
http://www.uni-magdeburg.de
http://www.helmholtz-hzi.de
http://www.helmholtz-hzi.de/en/news_events/news/view/article/complete/the_bodys_own_recycling_system/

More articles from Life Sciences:

nachricht Embryonic development: How do limbs develop from cells?
18.05.2018 | Humboldt-Universität zu Berlin

nachricht Reading histone modifications, an oncoprotein is modified in return
18.05.2018 | 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: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>