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 Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard

nachricht New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>