Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sticky proteins provide new insight into drug action

16.11.2006
How drugs such as adrenalin do primarily one thing – in this case, increase the heart rate – now makes more sense to scientists.

“Any time you get a sudden jolt, adrenaline (a.k.a. epinephrine) is why your heart rate goes up,” says Dr. Nevin A. Lambert, a biophysicist at the Medical College of Georgia. “If your heart is about to stop and the doctor administers epinephrine, that is what he or she is trying to do.”

New research, to be published in the Nov. 21 print issue of Proceedings of the National Academy of Sciences and already available online in Early Edition, may help explain how cells respond correctly to epinephrine.

Most drugs never get inside cells; they interact with external receptors that activate G proteins roaming inside cells. “If you are going to change the way the cell works, you have to transduce a signal from outside a cell inside,” says Dr. Lambert. “It’s like a relay. G proteins interact with receptors; they run into them, they collide with them. The receptor itself does not do anything other than turn on these G proteins.”

... more about:
»Ion »activate »epinephrine »interact »receptor

There are only four classes of G proteins, but cells contain thousands of copies of them which interact with hundreds of surface receptors. Each G protein is actually three protein subunits stuck together: alpha, beta and gamma.

Textbooks have long said that once G proteins are activated, the alpha protein splits from the beta and gamma subunits, which are irrevocably stuck together as a beta-gamma pair. Each half of the now dissociated G protein can cause the cell to do something different. “Sometimes they help each other out; sometimes they work at cross purposes,” says Dr. Lambert.

With epinephrine, that should mean the alpha subunit enables production of cyclic AMP, which increases the heart rate, while the beta-gamma pair should activate ion channels, making cells less electrically excitable and decreasing the heart rate.

However, it has been known for some time that while epinephrine does increase cyclic AMP in heart cells, it does not activate ion channels. While this situation makes sense because the cell isn’t asked to respond in two completely opposite ways, it has not been at all clear how the cell allows one response and suppresses the other.

That likely is because the G proteins activated by epinephrine receptors don’t readily dissociate, contrary to the textbook picture. MCG researchers have also shown that at least one other class of G proteins does dissociate, suggesting the textbook picture is at least partly correct.

Why the difference? Previous work on G proteins, including the discovery of the G proteins and their role in signal transduction, was mostly done in test tubes using purified proteins. MCG researchers used a technique they developed to actually look at G protein function inside living human cells.

Their findings suggest that epinephrine interacts with a G protein that doesn’t let go of the beta-gamma subunit.

“There was a constant question about how drugs sometimes avoid doing unwanted things,” says Dr. Lambert. “This helps us understand how drugs can be specific. The flipside of the coin is some drugs acting on some receptors will have multiple actions because the G proteins do dissociate.”

No doubt, the newfound information about G proteins is just one step toward better understanding how hundreds of receptors can act through just four classes of G proteins and produce so many physiologic results. “It’s like how can 100 cars drive down four roads and end up in 100 different places,” Dr. Lambert says.

But it’s a timely piece as science moves toward designer drugs, including some that could actually target G proteins directly, bypassing intermediary receptors, with the hope of getting a more robust response.

In Dr. Lambert’s lab, MCG graduate student Gregory J. Digby, first author on the PNAS paper, is now looking at G protein subunits that do and don’t fall apart with the long-range goal of designing ones that do what they want. “Right now, it’s all engineering for the sake of understanding how they work,” says Dr. Lambert.

Researchers suspect it’s literally the stickiness between the subunits that determine whether they split, and that the bottom line will be two classes of G proteins dissociating and two not.

Other co-authors include Robert M. Lober, M.D./Ph.D. student, and Pooja R. Sethi, laboratory technician. Dr. Alfred G. Gilman, longtime chair of pharmacology and now dean of the University of Texas Southwestern Medical School who won the 1994 Nobel Prize in Medicine for discovering G proteins, edited the paper.

The research was funded by the National Science Foundation and the National Institutes of Health.

Toni Baker | EurekAlert!
Further information:
http://www.mcg.edu

Further reports about: Ion activate epinephrine interact receptor

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Supersensitive through quantum entanglement

28.06.2017 | Physics and Astronomy

X-ray photoelectron spectroscopy under real ambient pressure conditions

28.06.2017 | Physics and Astronomy

Mice provide insight into genetics of autism spectrum disorders

28.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>