Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study reveals enzyme function, could help find muscular dystrophy therapies

10.01.2012
Study reveals function of glycosylating enzyme involved in muscular dystrophy, brain development and infection by arenaviruses such as Lassa fever; ability to assay enzyme activity could help screen potential muscular dystrophy therapies

Researchers at the University of Iowa have worked out the exact function of an enzyme that is critical for normal muscle structure and is involved in several muscular dystrophies. The findings, which were published Jan. 6 in the journal Science, could be used to develop rapid, large-scale testing of potential muscular dystrophy therapies.

The enzyme, called LARGE, adds a critical sugar chain onto an important membrane protein called dystroglycan. This sugar chain acts like a glue allowing dystroglycan to attach to other proteins and by doing so, reinforce cell membranes in many tissues including muscle and brain. Dystroglycan does not function properly without this sugar link, and that malfunction causes muscular dystrophies and brain abnormalities.

"LARGE is a critical enzyme involved in maintaining muscle cell viability," says Kevin Campbell, Ph.D., professor and head of molecular physiology and biophysics at the UI Carver College of Medicine and a Howard Hughes Medical Institute investigator. "It adds on a unique sugar chain that allows the muscle cell to protect its membrane from injury. By figuring out the function of this enzyme we've finally identified this critical sugar link."

The new study shows that the enzyme activity of LARGE has two specific sugar-adding functions -- it transfers the sugars xylose and glucuronic acid. Using nuclear magnetic resonance analysis (NMR), the team was also able to determine the precise structure of the sugar chain produced by LARGE, which has not been seen before.

The study confirmed that this unique sugar chain is responsible for dystroglycan's ability to attach to its protein partners, which include laminin in muscle and neurexin in brain.

In addition to LARGE, several other enzymes are involved in building the important dystroglycan sugar chain, and mutations in all these enzymes cause congenital muscular dystrophies collectively known as secondary dystroglycanopathies. These disorders include Fukuyama Congenital Muscular Dystrophy, Walker-Warburg Syndrome, Muscle-Eye-Brain disease, Congenital Muscular Dystrophy 1C and 1D, and limb-girdle muscular dystrophy 2I.

However, in all cases, the part of the sugar chain that is critical for dystroglycan function is the part that is added by LARGE. Furthermore, work from Campbell's lab has shown that boosting LARGE activity in cells from patients with these types of muscular dystrophies is sufficient to restore dystroglycan function and overcome the defects in the cells.

By understanding what the LARGE enzyme does, the researchers have now been able to develop a test, or assay, to monitor enzyme activity.

"It's exciting that we now have this enzyme assay, which could be used in a large-scale high-throughput screen for drugs that increase (or decrease) LARGE activity," Campbell says.

Using the assay to identify compounds that boost LARGE activity might lead to potential treatments for the secondary dystroglycanopathies. The assay could also be used to look at variations in LARGE activity in patients' cells. This may help identify patients who are affected by these LARGE-related muscular dystrophies.

LARGE activity is important in other diseases

The unusual sugar chain that LARGE builds onto dystroglycan is also implicated in other diseases. A group of viruses that includes Lassa fever appear to require the sugar chain to infect cells. Lassa fever is a hemorrhagic illness that can cause serious disease and death.

Now that the researchers have determined the make-up of the unusual sugar, Campbell suggests that it will be possible to make and test it as a therapeutic to block or reduce infection by these viruses.

Campbell is also excited by another aspect of the Lassa fever link. A genome-wide study of populations in West Africa where Lassa fever is endemic suggests that the LARGE gene may be modified in this population. Campbell speculates that altering LARGE activity might provide some protection against infection by the Lassa fever virus. In the future, he hopes to use his team's newly developed enzyme assay to investigate if LARGE activity is altered in this population.

In addition to Campbell, the study team included Kei-ichiro Inamori, Ph.D., and Takako Yoshida-Moriguchi, Ph.D., who were co-first authors of the study, and Yuji Hara, Ph.D., Mary Anderson, and Liping Yu, Ph.D.

The study was funded in part by a National Institutes of Health grant for the Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center at the UI.

Jennifer Brown | EurekAlert!
Further information:
http://www.uiowa.edu

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>