Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pressure Relief Valve in Cellular Membrane Identified

16.04.2014

Regulation of cell volume is critical for the body’s cells, f. e. during cellular exposure to fluids of varying salt concentrations, in cell division, cell growth, but also in diseases such as cancer, stroke and myocardial infarction.

A certain chloride channel, a membrane protein that allows the passage of the chloride ion, is of crucial importance in volume regulation. It is activated by the swelling of the cell and then releases chloride ions and organic matter (osmolytes) from the cell. Researchers in Berlin-Buch have now succeeded for the first time in elucidating the molecular identity of this volume-regulated anion channel (VRAC) (Science Express, DOI: 10.1126/science.1252826)*.


The volume-regulated anion channel VRAC

(Scheme: Lab. Jentsch/Copyright: MDC/FMP)

Researchers led by Professor Thomas J. Jentsch (Max Delbrück Center for Molecular Medicine, MDC, Berlin-Buch/Leibniz-Institut für Molekulare Pharmakologie, FMP) identified a molecule, LRRC8A, which is an essential constituent of the volume-regulated anion channel (VRAC). This protein needs to be assembled with related proteins (LRRC8B to E) to form channels with probably six subunits.

They could also show for the first time that these chloride channels are also permeable to small organic molecules such as taurine or amino acids. For over 20 years, research groups across the globe have been seeking to elucidate the molecular structure of the volume-regulated anion channel (VRAC). It took Jentsch’s team almost four years to achieve this breakthrough.

The regulation of cell volume is important for many functions in the organism. The volume-regulated anion channel (VRAC) which Thomas Jentsch and his coworkers Felizia Voss and Tobias Stauber now identified at the molecular level is expressed in all vertebrate cells.

If a particular cell volume is exceeded, the channel opens and permits the outflow of osmolytes such as chloride ions as well as small organic molecules such as taurine and amino acids. By contrast, cations such as potassium or sodium cannot permeate.

Once the channel is opened, chloride and other osmolytes pass in a passive process called diffusion. Due to its biophysical properties the channel only allows anions and certain organic compounds to pass. Thus, the cell reduces the concentration of its osmolytically active constituents to (or even below) that of the surrounding fluid. At the same time, the water content of the cell decreases as the water molecules flow out via aquaporins in the cell membrane. The volume of the cell decreases again.

LRRC8A was discovered as a VRAC component using a genome-wide RNA interference (siRNA) screen in collaboration with Katina Lazarow and Jens von Kries from the FMP Screening Unit. By means of short RNA snippets, the translation of the genetic information into the corresponding proteins can be suppressed. Using a one-by-one approach in a large-scale cell culture experiment, the Berlin group transiently silenced the products of all approximately 20,000 human genes.

In an automated screening process the researchers investigated which of the genes are required for the swelling-activated anion flux across the cell membrane. The approximately 130,000 time-dependent ion flux measurements were statistically analyzed with help from the Bioinformatics Group of the MDC (Nancy Mah/Miguel Andrade-Navarro).

The essential role of LRRC8 proteins in the volume-regulated anion channel was verified using CRISPR/Cas technology, which just became available during the past two years. With this method, specific genes on the chromosomes can be disrupted completely. Different combinations of LRRC8 proteins, all including the obligate LRRC8A, – either by omitting some of the family members from gene disruption or by reconstituting different combinations – led to different electrophysiological properties of the channel. “This allows us to explain the behavior of the channel in different tissues which until now had remained elusive,” Thomas Jentsch said.

"Cells can swell or in the worst case even burst. Water transport and content must therefore be tightly regulated," he added. Water transport is always driven by the osmotic gradient. Cells take up chloride from their surroundings, whereas organic substances such as taurine or amino acids are produced within the cells.

Deciphering the molecular structure of this chloride channel may also pave the way for better medical treatments, for example, after stroke. "In the case of damage in the brain, cells swell and release glutamate, which acts upon receptors on nerve cells. The subsequent inflow of calcium raises the intracellular concentration of this ion to toxic levels," Jentsch said. With the onset of programmed cell death (apoptosis) during cancer chemotherapy, however, there is a strong reduction in cell volume. The volume-regulated chloride channel also appears to be involved in this process.

*Identification of LRRC8 Heteromers as Essential Component of the Volume-regulated Anion Channel VRAC.

Felizia K. Voss1,2,3, Florian Ullrich1,2,3, Jonas Münch1,2,3, Katina Lazarow1, Darius Lutter1,2,3, Nancy Mah2, Miguel A. Andrade-Navarro2, Jens P. von Kries1, Tobias Stauber1,2 * and Thomas J. Jentsch1,2,4 *
*Correspondence to: Jentsch@fmp-berlin.de (T.J.J.); tstauber@fmp-berlin.de (T.S.).

1Leibniz-Institut für Molekulare Pharmakologie (FMP), Berlin
2Max Delbrück Center for Molecular Medicine (MDC), Berlin
3Graduate program of the Freie Universität Berlin
4Neurocure, Charité Universitätsmedizin, Berlin
Science Express, 10. April 2014; DOI: 10.1126/science.1252826

Contact:
Barbara Bachtler
Press Department
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch
in the Helmholtz Association
Robert-Rössle-Straße 10
13125 Berlin
Germany
Phone: +49 (0) 30 94 06 - 38 96
Fax: +49 (0) 30 94 06 - 38 33
e-mail: presse@mdc-berlin.de
http://www.mdc-berlin.de/

Silke Oßwald
Public Relations
Leibniz-Institut für Molekulare Pharmakologie
im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
Robert-Roessle-Str. 10
13125 Berlin, Germany
Phone: +49-30-94793-104
e-mail: osswald@fmp-berlin.de
http://www.fmp-berlin.info/de/home.html

The Max Delbrück Center for Molecular Medicine (MDC) is one of 18 research centers of the Helmholtz Association. It was founded in 1992 to link basic molecular basic research with clinical research. The MDC is working closely with the Charité - University Medicine in the Berlin Institute of Health (BIH) and has evolved in recent years into an internationally recognized research institute.

The Leibniz-Institut für Molekulare Pharmakologie (FMP) is part of the Forschungsverbund Berlin e.V. (FVB), a federation of eight institutes in Berlin in the field of natural, life and environmental sciences with a staff of more than 1500 employees. The multiple award-winning institutions are members of the Leibniz Association. The Forschungsverbund came into being in 1992 in a unique historical situation as the successor organization of the former Academy of Sciences of the GDR.

Barbara Bachtler | Max-Delbrück-Centrum

Further reports about: Cellular FMP Leibniz-Institut MDC Medicine Molecular Relief Valve acids amino chloride genes proteins volume

More articles from Life Sciences:

nachricht Mass spectrometry sheds new light on thallium poisoning cold case
14.12.2018 | University of Maryland

nachricht Protein involved in nematode stress response identified
14.12.2018 | University of Illinois College of Agricultural, Consumer and Environmental Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>