Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unexpected new mechanism behind rheumatoid arthritis

08.02.2011
A team of researchers at the University of Gothenburg, Sweden, has identified an enzyme that protects against inflammation and joint destruction. Made when the researchers blocked production of the enzyme GGTase-I in transgenic mice, this unexpected discovery could lead to the identification of new mechanisms that control the development of inflammatory disorders, as well as new medicines.

The article has been published in the Journal of Clinical Investigation (JCI). GGTase-I is found in all cells but is particularly important for the function of so-called CAAX proteins in inflammatory cells. GGTase-I attaches a cholesterol-like fatty acid on the CAAX proteins.

Researchers previously believed that this fatty acid played an important role in activating the proteins and could contribute to the functioning of inflammatory cells. There are now medicines that include substances that suppress the activity of GGTase-I with the aim of stopping the CAAX proteins from working. These substances are already being clinically tested on cancer patients, and researchers have also wondered whether they could be used to alleviate inflammatory disorders such as rheumatoid arthritis.

However, treatment with substances that inhibit GGTase-I has often been non-specific, making it difficult for researchers to assess the real potential of GGTase-I as a drug target.

“We therefore developed genetic strategies in transgenic mice to switch off the gene that codes for GGTase-I,” says PhD student Omar Khan who is heading up the study along with professor Martin Bergö and co-worker docent/consultant Maria Bokarewa from the Institute of Medicine. “This allowed us to investigate whether a complete blockade of GGTase-I can inhibit the development of inflammatory disorders and whether there are any side-effects.”

However, the results were quite the opposite of what the researchers were expecting. Instead of inhibiting inflammation, the deficiency of GGTase-I in macrophages (a common type of inflammatory cell) led to the mice developing chronic inflammation with cartilage and bone erosion in the joints, very similar to rheumatoid arthritis in humans.

“We had to reassess the role that GGTase-I plays in the function of CAAX proteins, and found that one group of CAAX proteins could not only function quite normally in macrophages that didn’t have any GGTase-I, but even increased in number and activity. This led to hyper-activation of the macrophages, which produced large quantities of inflammatory substances and, in turn, led to arthritis in the mice.”

GGTase-I acts on over 50 different CAAX proteins. The study shows that just one of these proteins – RAC1 – appears to be behind the disorder. This means that one function of GGTase-I is to suppress the activity of RAC1 and protect mice from developing arthritis. The results suggest that medicines that inhibit GGTase-I might actually induce arthritis instead of providing a cure. This will be important information for the ongoing clinical trials with GGTase-I inhibitors in cancer patients.

“The study has also resulted in an effective and simple genetic mouse model for arthritis that can be used to study the effect of new medicines and identify the mechanisms involved in the development of the disorder,” says Khan. “The next step is to try to decide whether and how GGTase-I and RAC1 are implicated in arthritis in humans.”

CAAX PROTEINS
CAAX proteins are a collection of proteins in the cells that have the amino acid sequence C-A-A-X at one end. This sequence is a signal for the protein to attract a number of enzymes, including GGTase-I, which switches on a cholesterol-like fatty acid on the CAAX proteins. This enables the protein to bind to membranes in the cells, for example the inside of the membrane that surrounds the cell. CAAX proteins include RAS (a well-known cancer protein) and the RAC and RHO proteins, which are important for many different cell functions.
For more information, please contact:
Professor Martin Bergö, Institute of Medicine, Sahlgrenska Academy, tel: +46 (0)31 342 7858, mobile: +46 (0)73 312 2224, e-mail: martin.bergo@wlab.gu.se
PhD student Omar Khan, Institute of Medicine, Sahlgrenska Academy, +46(0)31 342 4723, e-mail: omar.khan@wlab.gu.se

Docent/consultant Maria Bokarewa, Institute of Medicine, Sahlgrenska Academy, tel: +46 (0)31 342 4021, mobile: +46 (0)70 651 3292, e-mail: maria.bokarewa@rheuma.gu.se

Bibliographic data
Journal: Journal of Clinical Investigation (JCI).
Title of article: Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice

Authors: Omar M. Khan, Mohamed X. Ibrahim, Ing-Marie Jonsson, Christin Karlsson, Meng Liu, Anna-Karin M. Sjogren, Mikael Brisslert, Sofia Andersson, Claes Ohlsson, Lillemor Mattsson Hultén, Maria Bokarewa and Martin O. Bergo

Helena Aaberg | idw
Further information:
http://www.gu.se
http://www.sahlgrenska.gu.se/digitalAssets/1327/1327114_khan_et_al_jci43758.pdf

Further reports about: CAAX GGTase-I Medicine Rac1 fatty acid inflammatory cells proteins rheumatoid arthritis

More articles from Life Sciences:

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

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

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

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>