Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Need oxygen? Cells know how to spend and save

10.04.2007
Researchers at Johns Hopkins have discovered how cells fine-tune their oxygen use to make do with whatever amount is available at the moment.

Too little oxygen threatens life by compromising mitochondria that power it, so when oxygen is scarce, cells appear to adjust by replacing one protein with an energy-efficient substitute that "is specialized to keep the motor running smoothly even as it begins to run out of gas," says Gregg Semenza, M.D., Ph.D., a professor of pediatrics and director of the vascular biology program in the Institute for Cell Engineering at Hopkins. "This is one way that cells maintain energy production under less than ideal conditions." A report on the work is in the April 6 issue of Cell.

"Cells require a constant supply of oxygen," Semenza says, "so it's vital for them to quickly react to slight changes in oxygen levels." The protein-swap is how they do it.

In the mitochondria, the tiny powerhouses found in every cell, energy is produced by passing electrons through a series of relay stations called cytochromes until they eventually join with oxygen to form water. This final step is directed by the protein cytochrome coxidase, or COX for short. If electrons react with oxygen before reaching COX, they generate "free radicals" that can damage or destroy cells. The mitochondria are designed to produce energy without excess free radical production at normal oxygen levels.

... more about:
»COX4-1 »COX4-2 »Cox »HIF-1 »Hypoxia »mitochondria

Semenza's team noticed that one particular component of the COX protein complex, COX4, comes in two different forms, COX4-1 and COX4-2. Under normal oxygen conditions, the cells' mitochondria contain mostly COX4-1. The researchers suspected that COX 4-2 might be the active protein under stressful, low-oxygen conditions, which the researchers refer to as hypoxia.

To test the idea, the team compared the growth of human cells in normal oxygen conditions (what's generally present in normal room air) compared to cells grown in hypoxia. In low oxygen, liver, uterus, lung and colon cells all made COX4-2. The researchers then exposed mice to hypoxia for a few weeks and found that they too showed increased levels of COX4-2.

In 1992, Semenza's team had discovered a protein which they called HIF-1 (for hypoxia-inducible factor 1) that cells make in response to hypoxia. HIF-1 turns on genes that help cells survive when oxygen is low, such as during a heart attack or stroke. The researchers set out to figure out if the sensor protein HIF-1 triggers the COX-swapping.

By examining the gene control regions of COX4, they found that the HIF-1 sensor switched on COX4-2 activity when oxygen is low. And they learned that because COX4-1 already is in the mitochondria, the swap for COX4-2 occurs when the sensor turns on yet another gene that produces an enzyme to specifically chew up COX4-1. Engineering human cells to lack this enzyme and subjecting them to low oxygen, the scientists found the cells unable to rid themselves of COX4-1.

"It's remarkable that the one-celled yeast also swap COX subunits in response to hypoxia, but because they lack HIF-1, they accomplish the swap in a completely different way," says Semenza. "This suggests that adapting mitochondria to changes in oxygen levels may be a major challenge for most organisms on Earth."

Audrey Huang | EurekAlert!
Further information:
http://www.jhmi.edu
http://www.cell.com/
http://www.hopkinsmedicine.org/geneticmedicine/index.html

Further reports about: COX4-1 COX4-2 Cox HIF-1 Hypoxia mitochondria

More articles from Life Sciences:

nachricht Navigational view of the brain thanks to powerful X-rays
18.10.2017 | Georgia Institute of Technology

nachricht Separating methane and CO2 will become more efficient
18.10.2017 | KU Leuven

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Osaka university researchers make the slipperiest surfaces adhesive

18.10.2017 | Materials Sciences

Space radiation won't stop NASA's human exploration

18.10.2017 | Physics and Astronomy

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>