Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Discovery may be first plant cell surface molecule that halts cell proliferation

22.09.2003


Protein contains both ’on’ and ’off’ switches



University of North Carolina at Chapel Hill scientists have discovered a unique protein on the surface membrane of plant cells, one that apparently contains both "on" and "off" molecular switches. Apart from its unique structure, the protein may be the first cell surface membrane receptor ever discovered in plants that regulates a key protein complex involved in cell growth and division. Known as the heterotrimeric G protein complex, it also is present in mammalian cells, including human.

The protein, known as AtRGS1, regulates the process of cell proliferation by turning the G protein complex off. A report of the discovery appears in today’s (Sept. 19) issue of the journal Science.


The protein was discovered in Arabidopsis thaliana, a wild mustard weed. Completion of the Arabidopsis genome sequence in 2000, the first for a higher plant, made it ideal for molecular investigation such as this. In addition, this small weed has homologues or counterparts of many important human proteins, including some involved in diseases, such as cystic fibrosis and cancer.

"We have identified the first and a truly novel regulator of G protein signaling, or RGS signaling protein, in Arabidopsis," said Dr. Jin-Gui Chen, senior research associate in the department of biology and the report’s first author. "This finding can be considered a breakthrough in G protein signaling."

Roughly 800 types of these cell receptors exist in human cells, said plant cell biologist Dr. Alan M. Jones, a senior study author and professor of biology in UNC’s College of Arts and Sciences.

"These are the molecular targets for about half of the drugs in use today worldwide, which account for $9 billion a year in sales." Teasing out the complexities of how signals are transduced into action within cells also holds implications for agriculture. "The new RGS protein’s function in the G protein signaling pathway may give us a handle on how fast plant organs can produce cells," said Jones.

"Indeed, this particular pathway is a growth pathway, and now we have another player [AtRGS1] we can utilize to bioengineer crops." Previous studies of mammalian cells had provided hints that G protein coupled receptors and RGS proteins are intimately linked functionally, said the other senior author of the study, Dr. David P. Siderovski. He is an assistant professor of pharmacology and a member of UNC’s Lineberger Comprehensive Center, part of UNC’s School of Medicine.

"And this study is the ultimate proof because they are intimately linked structurally," he added. "This really sets the paradigm clearly in the minds of all of us studying this signaling. For a long time there have been hints of receptor-specific recruitment of these RGS proteins. But plants have really slapped us awake to this because they’re one polypeptide; they’re actually conjoint."

The new study exemplifies UNC’s research strength in G protein signaling, including RGS proteins. Siderovski and Dr. Henrik G. Dohlman, associate professor of biochemistry and biophysics, were the first to independently discover this class of proteins nearly eight years ago.

Dohlman found the first such protein in yeast, while Siderovski had found similar proteins in humans.

Jones, who for many years has been studying the plant components equivalent to the G protein complex in mammals, asked Siderovski to explore the Arabidopsis data base for a G protein coupled receptor. In searching through protein sequences on a computer screen, Siderovski said he stumbled upon a divergent form of RGS protein in Arabidopsis, one with features of both a cell-surface receptor and an RGS protein. Dohlman, whose laboratory tested the function of the new protein in yeast, said a common theme in biology is that every ’on’ switch has an ’off’ switch. "What’s unique about this particular protein is it seems to contain elements of both the ’on’ switch and ’off’ switch in the same molecule. And this is unprecedented," he said.

"The classic paradigm is you have a cell surface receptor that activates a pathway by binding some molecule, such as calcium or a hormone," said Jones. "Here we have a ’CatDog’ phenomenon," he added, referring to a popular TV cartoon series, "a putative receptor that has the structural features of both an activator and an RGS-like deactivator."

Still, the researchers said, two interpretations may operate here. One is that the switches are simply physically linked. Or it could be that the ’off’ switch and the ’on’ switch are each regulated by external signals. They agree, however, that either scenario is extremely exciting.

"I think this opens up a new paradigm that may not be specific or unique to the plant cell. I would not be surprised if we find it in human cells," said Jones.

Other co-authors are Dr. Francis S. Willard, from the department of pharmacology and the Lineberger Center; Dr. Scott A. Chasse, a trainee with Dohlman from biochemistry and biophysics; and Jirong Huang and Jiansheng Liang, from the department of biology. Support for this research came from the National Institute of General Medical Sciences and the National Science Foundation via grants awarded to Siderovski, Dohlman and Jones.


Note: Contact Jones at (919) 962-6932 or alan_jones@unc.edu. Contact Siderovski at (919) 843-9363 or david_siderovski@med.unc.edu. Contact Dohlman at (919) 843-6894 or henrik_dohlman@med.unc.edu.

School of Medicine contact: Les Lang, (919) 843-9687 or llang@med.unc.edu

Leslie Lang | EurekAlert!
Further information:
http://www.med.unc.edu/

More articles from Life Sciences:

nachricht New insight into a central biological dogma on ion transport
26.06.2017 | Aarhus University

nachricht UK chemistry researchers develop catalyst that mimics the z-scheme of photosynthesis
26.06.2017 | University of Kentucky

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

New 3-D model predicts best planting practices for farmers

26.06.2017 | Agricultural and Forestry Science

New research reveals impact of seismic surveys on zooplankton

26.06.2017 | Life Sciences

Correct connections are crucial

26.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>