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 A room with a view - or how cultural differences matter in room size perception
25.04.2017 | Max-Planck-Institut für biologische Kybernetik

nachricht Studying a catalyst for blood cancers
25.04.2017 | University of Miami Miller School of Medicine

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Early organic carbon got deep burial in mantle

25.04.2017 | Earth Sciences

A room with a view - or how cultural differences matter in room size perception

25.04.2017 | Life Sciences

Warm winds: New insight into what weakens Antarctic ice shelves

25.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>