Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Yeast model offers clues to possible drug targets for Lou Gehrig's disease, study shows

29.10.2012
Amyotrophic lateral sclerosis, also called Lou Gehrig's disease, is a devastatingly cruel neurodegenerative disorder that robs sufferers of the ability to move, speak and, finally, breathe.

Now researchers at the Stanford University School of Medicine and San Francisco's Gladstone Institutes have used baker's yeast — a tiny, one-celled organism — to identify a chink in the armor of the currently incurable disease that may eventually lead to new therapies for human patients.

"Even though yeast and humans are separated by a billion years of evolution, we were able to use the power of yeast genetics to identify an unexpected potential drug target for ALS," said Aaron Gitler, PhD, an associate professor of genetics at Stanford. "Many neurodegenerative disorders such as ALS, Parkinson's and Alzheimer's exhibit protein clumping or misfolding within the neurons that is thought to either cause or contribute to the conditions. We are trying to figure out why these proteins aggregate in neurons in the brain and spinal cord, and what happens when they do."

In 2008, Gitler received a New Innovator award from the National Institutes of Health to use yeast as a model for understanding human neurodegenerative diseases and as a way to identify new targets for drug development.

Gitler is the co-senior author of the research, which will be published online Oct. 28 in Nature Genetics. Robert Farese, Jr., MD, a senior investigator at the Gladstone Institutes, is the other co-senior author. Stanford graduate student Maria Armakola shares co-first authorship with Matthew Higgins, PhD, a postdoctoral scholar at Gladstone.

Most cases of ALS have no clear-cut cause. However, it has recently been shown that an RNA-binding protein called TDP-43 accumulates in clumps in the cytoplasm of spinal cord neurons in many people with the condition, and mutations in this protein have been found in some people with the ALS. Researchers like Gitler and Farese have been able to mimic the disease in yeast by expressing TDP-43 at higher-than-normal levels, which causes the protein to form lethal clumps in the cells' cytoplasm.

"In humans, the progression of the disease can take years before symptoms arise," said Gitler. "But in yeast, we see protein clumping in the cytoplasm within two days and the cells rapidly begin to die." With their model system in place, Gitler and Farese set out to see whether it was possible to protect yeast cells from this effect by tinkering with the function of other proteins in the cell.

In this study, the researchers discovered that blocking the production of a protein called Dbr1 in a yeast model stops the TDP-43 clumping and allows the cells to live normally. The researchers confirmed the results in human nerve cells grown in the laboratory and in rat neurons overexpressing TDP-43.

"In this study we made no assumptions as to how TDP-43 injures cells," said Farese, "but instead screened the whole yeast genome to find genes that might prevent the toxicity. Independently, both our lab and the Gitler lab found that loss of Dbr1, an enzyme involved in RNA processing, could do this."

Dbr1 serves as part of the cellular clean-up crew that mops up the bits of unwanted RNA generated as part of the protein production line. In our DNA, most genes consist of coding regions, called exons, broken up into several segments by non-coding regions, called introns. Cells can make many different, related proteins from the same stretch of DNA by mixing and matching different exons in a process called splicing.

When the DNA is first copied, or transcribed, into RNA, the introns as well as the exons are included. But the cell quickly splices out the introns, which are released into the cytoplasm as little loops, or lariats. Dbr1, in turn, clips the loops to open them and make them accessible to the cell's disposal system.

Blocking the production of Dbr1 causes the RNA lariats to build up in the cytoplasm. The researchers showed — by creating lariats with a binding site for a fluorescent tracking protein — that the mutant TDP-43 binds to these excess lariats rather than clumping. The effect is like using a paper towel to mop up a spill on your computer keyboard: binding to the lariats appears to keep TDP-43 from causing havoc elsewhere.

"Normally, TDP-43 is found in the nucleus," said first author Armakola. "But in the diseased cells, it aggregates in the cytoplasm and forms clumps. We developed a novel way to track where these lariats go in living cells, and we saw that when Dbr1 is missing, the lariats act as a sink to sequester TDP-43."

The researchers note that it's still not entirely clear whether the cells die because the mutant TDP-43 is drawing essential RNA transcripts or regulatory molecules away from the nucleus and into the cytoplasm, or because it's not performing its normal RNA-binding function in the nucleus. Both could contribute to the progression of the disease.

The results in the yeast, rodent and human cells, however, suggest that therapeutic approaches aimed at blocking Dbr1 function, or even creating artificial lariat-like formations to draw away the mutant molecule, should be explored.

"Next, we'd like to explore blocking Dbr1 function in animals such as flies, worms and rodents," said Armakola. "We're also interested in identifying small molecule inhibitors of Dbr1."

Other Stanford co-authors include graduate student Matthew Figley. The research was supported by the NIH, the Ellison Medical Foundation, the Packard Center for ALS Research at Johns Hopkins, the Consortium for Frontotemporal Research, the ALS Association, the Taube-Koret Center, the Hellman Family Foundation, the Pew Charitable Trusts, the Rita Allen Foundation, the Searle Scholars Program, the Keck Foundation and the National Center for Research Resources.

The Stanford University School of Medicine consistently ranks among the nation's top medical schools, integrating research, medical education, patient care and community service. For more news about the school, please visit http://mednews.stanford.edu. The medical school is part of Stanford Medicine, which includes Stanford Hospital & Clinics and Lucile Packard Children's Hospital. For information about all three, please visit http://stanfordmedicine.org/about/news.html

Krista Conger | EurekAlert!
Further information:
http://www.stanford.edu

More articles from Health and Medicine:

nachricht Plasmonic biosensors enable development of new easy-to-use health tests
14.12.2017 | Aalto University

nachricht ASU scientists develop new, rapid pipeline for antimicrobials
14.12.2017 | Arizona State University

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

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

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>