Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New clue to Parkinson's

15.08.2011
Shape of key protein surprises researchers

A new study finds that a protein key to Parkinson's disease has likely been mischaracterized. The protein, alpha-synuclein, appears to have a radically different structure in healthy cells than previously thought, challenging existing disease paradigms and suggesting a new therapeutic approach.

"Our data show that alpha-synuclein was essentially mistakenly characterized as a natively unfolded protein that lacked structure," said Dennis Selkoe, the Vincent and Stella Coates Professor of Neurologic Diseases at Brigham and Women's Hospital and Harvard Medical School and senior author of the paper, published online August 14 in the journal Nature. "We think this discovery has fundamental importance for understanding both how alpha-synuclein normally functions and how it becomes altered in Parkinson's."

When it comes to proteins, function follows form. A protein consists of a chain of chemical building blocks (amino acids), typically folded into an exquisite three-dimensional structure. Each twist and turn in the chain contributes to the protein's unique properties and behavior, so it's critical for scientists to accurately describe the arrangement of folds. But sometimes, they get the entire pattern wrong.

The new study suggests that's just what happened with alpha-synuclein, the protein that forms clumps called Lewy bodies in the brains of patients with Parkinson's and certain related disorders. Scientists have long assumed that alpha-synuclein occurs in healthy cells as a single, randomly-coiled chain that resembles a writhing snake. Selkoe's team has proven, however, that the structure is far more orderly and sophisticated.

"This will open some new therapeutic doors," said first author Tim Bartels, a postdoctoral researcher in Selkoe's lab. "Everybody thought the protein was unfolded, so pharmaceutical companies have focused on preventing unfolded alpha-synuclein from aggregating."

He recommends a new strategy—keeping the folded form of the protein stable.

How did the true structure of alpha-synuclein in healthy cells evade researchers for so long? Scientists knew that alpha-synuclein was abundant in the brain before they made the connection between the protein and Parkinson's disease in 1997. Experiments in the mid-1990s indicated the protein was stable when exposed to conditions that typically disrupt the structure of most other proteins.

Consider what happens when an egg is boiled: the liquid proteins of the egg white are precipitated by the heat and congeal into a dense white mass. But alpha-synuclein seemed to behave like an egg that remains entirely viscous despite many minutes on the stove. It didn't precipitate and congeal when boiled. This apparent hardiness made alpha-synuclein easy to work with in the lab. Scientists could boil the protein, even douse it with detergents and other rather harsh chemicals, while ostensibly leaving its structure intact.

Bartels and Selkoe wondered whether labs might be overlooking important aspects of the protein's natural biology by handling it so roughly, so they designed experiments to probe alpha-synuclein's behavior using gentler methods. They also bucked a trend by working with protein gathered from human cells rather than from engineered bacteria. The goal was to gain new insight into alpha-synuclein's clustering behavior.

The initial data took them by surprise. Single, isolated chains of alpha-synuclein—the "monomeric" form of the protein—were absent from their cellular samples.

"I did my PhD on alpha-synuclein, and—like the rest of the world—I assumed that it occurs natively as a monomeric, unfolded protein, so I was shocked," said Bartels.

Using special gels and other methods that are less disruptive to a protein's form, the team conducted additional experiments to explore the structure of alpha-synuclein in healthy blood and brain cells. The native protein was exactly four times the predicted weight of a single alpha-synuclein chain, suggesting that cells package four alpha-synuclein chains together as a "tetrameric" unit. Applying sophisticated equipment and techniques, the team validated the molecular weight of the package, confirmed that it consists solely of alpha-synuclein chains and showed that these four chains have orderly twists.

The researchers observed tetrameric alpha-synuclein to be the dominant form of the protein in healthy human cells, and remarkably resistant to aggregation. The tetramers maintained their original structure for 10 days, the entire length of the experiment, while the team monitored their samples for clustering behavior. In stark contrast, alpha-synuclein monomers began to form clusters after a few days and ended up as large aggregates called amyloid fibers. The Lewy bodies that accumulate in the brains of patients with Parkinson's consist mainly of such amyloid fibers.

"We hypothesize that the folded protein must disassemble into monomers before large pathological aggregates can form," said Selkoe, who is also co-director of the Center for Neurologic Diseases at Brigham and Women's Hospital. "If we can keep alpha-synuclein tetrameric and soluble, we might be able to prevent the neuronal degeneration of Parkinson's disease from progressing—or perhaps from even developing."

The finding could also prove useful in the quest for new diagnostics. Perhaps ratios of tetrameric protein to monomeric protein in blood cells, serum or spinal fluid will correspond to different propensities or stages of the disease.

Finally, the discovery of the folded tetramers should help labs to uncover the function of alpha-synuclein in healthy cells, which is still much debated. This functional knowledge should, in turn, contribute to researchers' understanding of Parkinson's and other diseases characterized by the formation of Lewy bodies rich in aggregated alpha-synuclein.

This research was funded by the National Institute of Neurological Disorders and Stroke.

Katie DuBoff | EurekAlert!
Further information:
http://www.harvard.edu

More articles from Health and Medicine:

nachricht Antibiotic effective against drug-resistant bacteria in pediatric skin infections
17.02.2017 | University of California - San Diego

nachricht Tiny magnetic implant offers new drug delivery method
14.02.2017 | University of British Columbia

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: 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

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>