Rice University scientists have discovered a new way to look inside
living cells and see the insoluble fibrillar deposits associated with
Parkinson's disease.
The combined talents of two Rice laboratories -- one that studies the
misfolded proteins that cause neurodegenerative diseases and another
that specializes in photoluminescent probes -- led to the spectroscopic
technique that could become a valuable tool for scientists and
pharmaceutical companies.
The research by the Rice labs of Angel Martí and Laura Segatori appeared online this month in the Journal of the American Chemical Society.
The researchers designed a molecular probe based on the metallic
element ruthenium. Testing inside live neuroglioma cells, they found the
probe binds with the misfolded alpha-synuclein proteins that clump
together and form fibrils and disrupt the cell's functions. The
ruthenium complex lit up when triggered by a laser -- but only when
attached to the fibril, which allowed aggregation to be tracked using
photoluminescence spectroscopy.
Researchers trying to understand molecular mechanisms of protein
misfolding have had limited alternatives to monitor protein aggregation
in cells, Martí said. A probe that can monitor the formation of
aggregates should be of great value in the search for drugs that break
up fibrils or prevent them from ever forming.
Two years ago, Martí, an assistant professor of chemistry and
bioengineering, and Rice graduate student Nathan Cook revealed their
metallic compounds that switch on like a light bulb when they attach to
misfolded proteins; that study involved the beta amyloids that form
plaques in the brains of Alzheimer's sufferers.
At about the same time, Cook approached Segatori, the T.N. Law
Assistant Professor of Chemical and Biomolecular Engineering and
assistant professor of biochemistry and cell biology, to ask if she
would serve on his dissertation committee. They started talking about
his work with Martí, and Segatori quickly saw the potential of a
partnership.
Segatori has made important strides in the study of diseases caused
by proteins that misfold and clump together. Alzheimer's, Parkinson's
and Gaucher diseases are examples, all the result of genetic mutations
or conditions that disrupt the way proteins fold and keep them from
performing their functions.
"There are a few compounds you can use to detect the presence of
these types of protein aggregates, but none of them have been reported
to work in cells," Segatori said. "When you're thinking about developing
a therapeutic strategy, you want to be able to detect the presence of
fibril aggregates in living cells, or even in animals. It's been very
nice to collaborate with someone with the expertise to do this."
"The connection between Parkinson's and Alzheimer's is natural,
although they are very different diseases because Alzheimer's beta
amyloid peptides are extracellular, while the onset of Parkinson's is
associated with alpha-synuclein protein inside cells," Martí said. "We
always thought we could apply the same techniques we used for beta
amyloids to probe the aggregation of other proteins.
"When we learned that Laura has cells that overexpress
alpha-synuclein, we thought, 'That's perfect.' She had the system and we
had the probes," he said.
Segatori pointed out the ruthenium complex has no therapeutic benefit
for Parkinson's sufferers, but "is a step toward understanding the
chemistry, which obviously will help in the development of drugs."
They see the possibility that metallic complexes can be tailored to
tag aggregates implicated in other degenerative diseases. "Metal
complexes are like Legos, in the sense that you can attach whatever you
want to them," Cook said.
As a proof of principle, the researchers created an in vitro cell
model of Parkinson's disease and found their ruthenium complexes clearly
labeled fibrillar alpha-synuclein proteins in cells.
"We can use it to test our strategies to prevent misfolding of
proteins or to increase their degradation, so they will be eliminated,"
Segatori said. "It will be an easy tool to use for a lot of
experiments."
Kiri Kilpatrick, a graduate student in Segatori's lab, co-authored the paper.
The National Science Foundation and the Welch Foundation supported the research.
Journal Reference:
- Nathan P. Cook, Kiri Kilpatrick, Laura Segatori, Angel A. Mart. Detection of α-Synuclein Amyloidogenic Aggregatesin Vitroand in Cells using Light-Switching Dipyridophenazine Ruthenium(II) Complexes. Journal of the American Chemical Society, 2012; 121214074651005 DOI: 10.1021/ja3100287
Courtesy: ScienceDaily
No comments:
Post a Comment