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 Stingless bees have their nests protected by soldiers
24.02.2017 | Johannes Gutenberg-Universität Mainz

nachricht Antimicrobial substances identified in Komodo dragon blood
23.02.2017 | American Chemical Society

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

NASA eyes Pineapple Express soaking California

24.02.2017 | Earth Sciences

New gene for atrazine resistance identified in waterhemp

24.02.2017 | Agricultural and Forestry Science

New Mechanisms of Gene Inactivation may prevent Aging and Cancer

24.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>