Category: Alzheimer’s

Working as part of a public program to screen compounds to find potential medicines and other biologically useful molecules, scientists from The Scripps Research Institute and Massachusetts Institute of Technology (MIT) have discovered an extremely potent class of potential anti-cancer and anti-neurodegenerative disorder compounds. The scientists hope their findings will one day lead to new therapies for cancer and Alzheimer's disease patients.

The research — scheduled for publication in the journal Proceedings of the National Academy of Sciences (PNAS) the week of March 7, 2011 — was led by Benjamin F. Cravatt III, professor and chair of the Department of Chemical Physiology at Scripps Research and a member of its Skaggs Institute for Chemical Biology, and MIT chemistry professor Gregory Fu.

"It was immediately clear that a single class of compounds stood out," said Daniel Bachovchin, a graduate student in the Cravatt lab and the study's first author. "The fact that these compounds work so potently and selectively in cancer cells and mice, right off the screening deck and before we'd done any medicinal chemistry, is very encouraging and also very unusual."

Browsing in the Public Library

The National Institutes of Health (NIH) Common Fund Molecular Libraries Program currently funds nine screening and medicinal chemistry-related centers at academic institutions around the United States to enable scientists to find biologically interesting molecules, independently of commercial labs. In these centers, academic scientists can test thousands of compounds at once through high-throughput screens against various biological targets to uncover "proof-of-concept" molecules useful in studying human health and in developing new treatments for human diseases.

"Initially the compounds in the NIH Molecular Libraries repository were purchased from commercial sources and augmented through chemical diversity initiatives," explained Ingrid Y. Li, director of the Molecular Libraries Program at the NIH National Institute of Mental Health (NIMH). "In recent years we've also encouraged academics to donate structurally unusual compounds, to add novelty to the library."

In 2008, Fu's lab donated a set of molecules known as aza-beta-lactams (ABLs) — molecular cousins of penicillin and other beta-lactam antibiotics. "These were molecules that probably didn't exist in commercial compound libraries, and their bioactivity had been virtually unexplored," said Fu.

Meanwhile, across the country, in the Cravatt lab at Scripps Research campus in La Jolla, California, Bachovchin was developing an unusually fast and flexible test for enzyme activity, using fluorescent molecular probes that bind to an enzyme's active site. Researchers can use such tests to measure whether an enzyme of interest loses its activity in the presence of another chemical compound. Bachovchin, Cravatt, and their colleagues decided to apply the new technique to the NIH compound library, to find an inhibitor for an enzyme known as PME-1 (phosphatase methylesterase 1).

Long seen as a potential high-value drug target, PME-1 chemically modifies a growth-slowing enzyme, known as PP2A, in a way that negates PP2A's ability to serve as a tumor suppressor. Studies have shown that when PME-1 production is reduced in some kinds of brain cancer cells, the tumor-suppressing activity of PP2A increases, and cancerous growth is slowed or stopped. Researchers also have found hints that PME-1 might play a role in promoting Alzheimer's disease, by regulating PP2A's ability to dephosphoryate the Alzheimer's-associated tau protein.

"Despite its importance, no one had been able to develop a PME-1 inhibitor, mainly because standard substrate assays for the enzyme were difficult to adapt for high-throughput screening," said Cravatt. "But we believed that we could use our new 'substrate-free' screening technology for PME-1; and we knew that we needed to try a large, high-throughput screen, because our small-scale efforts to find PME-1 inhibitors had come up empty."

Scripps Research runs an NIH Molecular Libraries Program screening center at its Jupiter, Florida campus. There, the institute's researchers set up an automated version of Bachovchin's new screening technique and used it to search for strong PME-1 inhibitors among the 300,000-plus small-molecule compounds in the NIH library.

Super Potent, Super Selective

Like many molecules, ABLs can exist in two mirror-image versions, known as enantiomers, and they usually are synthesized as an equal mixture of both compounds. But Fu and his group had used new chemistry techniques to produce the ABLs in an "enantiomerically selective" way, in case one enantiomer of a compound had more activity than its mirror-image twin. And, in fact, one of these enantiomeric molecules, ABL127, turned out to fit so precisely into a nook on PME-1 that it completely blocked PME-1 activity in cell cultures and in the brains of mice. Aside from being extremely potent, it also was highly selective for PME-1, so that even at higher doses, it had negligible effects on other enzymes in the PME-1 family, known as serine hydrolases. In mice, ABL127's inhibition of PME-1 activity caused a more than one-third drop in the measured level of demethylated ("inactive") PP2A.

The Cravatt and Fu labs are now working together to synthesize more ABLs and explore their chemistry, looking for the best possible PME-1 inhibitor. The near-term goal is to use ABL127 as a scientific probe to study PME-1 functions in animals. A longer-term goal is to develop ABL127, or related compounds, as potential oncology or Alzheimer's disease drugs.

"Already several labs from both academia and industry have contacted us about collaborating on PME-1 research," said Cravatt. "So our findings here are scientifically interesting, and I think could, one day, be valuable clinically. But it's important to emphasize that we wouldn't have these findings at all, were it not for the NIH Molecular Libraries Program and its compound library. Both on the screening side and the chemistry side, the NIH enabled us academics to bring technologies to the table unlikely to be found in a traditional 'pharma' setting. Our discoveries thus stand as a fine example of the value of public screening for creating novel, in vivo-active pharmacological probes for challenging protein targets."

The paper's other co-authors were Justin T. Mohr and Jacob M. Berlin of the Fu laboratory at MIT; Timothy P. Spicer, Virneliz Fernandez-Vega, Peter Chase, Peter S. Hodder, and Stephan C. Schürer of the Scripps Molecular Screening Center in Jupiter, Florida; and Anna E. Speers, Chu Wang, Daniel K. Nomura and Hugh Rosen of the Scripps Research campus in La Jolla, California.

The activities described in this release are funded through the National Institutes of Health (MH084512, CA132630, and GM57034).

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Journal Reference:

1. K. C. Nicolaou, S. Sanchini, D. Sarlah, G. Lu, T. R. Wu, D. K. Nomura, B. F. Cravatt, B. Cubitt, J. C. de la Torre, A. J. Hessell, D. R. Burton. Organic Synthesis Toward Small-Molecule Probes and Drugs Special Feature: Design, synthesis, and biological evaluation of a biyouyanagin compound library. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1015258108

By mimicking the structure of the silk moth's antenna, University of Michigan researchers led the development of a better nanopore — a tiny tunnel-shaped tool that could advance understanding of a class of neurodegenerative diseases that includes Alzheimer's.

A paper on the work is newly published online in Nature Nanotechnology. This project is headed by Michael Mayer, an associate professor in the U-M departments of Biomedical Engineering and Chemical Engineering. Also collaborating are Jerry Yang, an associate professor at the University of California, San Diego and Jiali Li, an associate professor at the University of Arkansas.

Nanopores — essentially holes drilled in a silicon chip — are miniscule measurement devices that enable the study of single molecules or proteins. Even today's best nanopores clog easily, so the technology hasn't been widely adopted in the lab. Improved versions are expected to be major boons for faster, cheaper DNA sequencing and protein analysis.

The team engineered an oily coating that traps and smoothly transports molecules of interest through nanopores. The coating also allows researchers to adjust the size of the pore with close-to-atomic precision.

"What this gives us is an improved tool to characterize biomolecules," Mayer said. "It allows us to gain understanding about their size, charge, shape, concentration and the speed at which they assemble. This could help us possibly diagnose and understand what is going wrong in a category of neurodegenerative disease that includes Parkinson's, Huntington's and Alzheimer's."

Mayer's "fluid lipid bilayer" resembles a coating on the male silk moth's antenna that helps it smell nearby female moths. The coating catches pheromone molecules in the air and carries them through nanotunnels in the exoskeleton to nerve cells that send a message to the bug's brain.

"These pheromones are lipophilic. They like to bind to lipids, or fat-like materials. So they get trapped and concentrated on the surface of this lipid layer in the silk moth. The layer greases the movement of the pheromones to the place where they need to be. Our new coating serves the same purpose," Mayer said.

One of Mayer's main research tracks is to study proteins called amyloid-beta peptides that are thought to coagulate into fibers that affect the brain in Alzheimer's. He is interested in studying the size and shape of these fibers and how they form.

"Existing techniques don't allow you to monitor the process very well. We wanted to see the clumping of these peptides using nanopores, but every time we tried it, the pores clogged up," Mayer said. "Then we made this coating, and now our idea works."

To use nanopores in experiments, researchers position the pore-pricked chip between two chambers of saltwater. They drop the molecules of interest into one of the chambers and send an electric current through the pore. As each molecule or protein passes through the pore, it changes the pore's electrical resistance. The amount of change observed tells the researchers valuable information about the molecule's size, electrical charge and shape.

Due to their small footprint and low power requirements, nanopores could also be used to detect biological warfare agents.

A research highlight on this work will appear in an upcoming edition of Nature. The paper is titled "Controlling protein translocation through nanopores with bio-inspired fluid walls."

This research is funded by the National Science Foundation, the National Institutes of Health, the Alzheimer's Disease Research Center, the Alzheimer's Association and the National Human Genome Research Institute. The university is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

Researchers at the University of Illinois at Chicago have shown for the first time that damage to a particular area of the brain and a consequent reduction in noradrenaline are associated with multiple sclerosis.

The study is available online in the journal Brain.

The pathological processes in MS are not well understood, but an important contributor to its progression is the infiltration of white blood cells involved in immune defense through the blood-brain barrier.

Douglas Feinstein, research professor in anesthesiology at the UIC College of Medicine, and his colleagues previously showed that the neurotransmitter noradrenaline plays an important role as an immunosuppressant in the brain, preventing inflammation and stress to neurons. Noradrenaline is also known to help to preserve the integrity of the blood-brain barrier.

Because the major source of noradrenaline is neurons in an area of the brain called the locus coeruleus, the UIC researchers hypothesized that damage to the LC was responsible for lowered levels of noradrenaline in the brains of MS patients.

"There's a lot of evidence of damage to the LC in Alzheimer's and Parkinson's disease, but this is the first time that it has been demonstrated that there is stress involved to the neurons in the LC of MS patients, and that there is a reduction in brain noradrenaline levels," said Paul Polak, research specialist in the health sciences in anesthesiology and first author on the paper.

For the last 15 years, Feinstein and his colleagues have been studying the importance of noradrenaline to inflammatory processes in the brain.

"We have all the models for studying this problem, so in some ways it was a small step to look at this question in MS," said Polak.

The researchers found that LC damage and reduced levels of noradrenaline occur in a mouse model of MS and that similar changes could be found in the brains of MS patients.

The findings suggest that LC damage, accompanied by reduction in noradrenaline levels in the brain, may be a common feature of neurologic diseases, Polak said.

"There are a number of FDA-approved drugs that have been shown to raise levels of noradrenaline in the brain, and we believe that this type of therapeutic intervention could benefit patients with MS and other neurodegenerative diseases, and should be investigated," he said.

Sergey Kalinin, post-doctoral research associate in anesthesiology, also contributed to the study. This study was supported by grants from the Department of Veteran Affairs and Partners for Cures.

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Journal Reference:

1. P. E. Polak, S. Kalinin, D. L. Feinstein. Locus coeruleus damage and noradrenaline reductions in multiple sclerosis and experimental autoimmune encephalomyelitis. Brain, 2011; DOI: 10.1093/brain/awq362

 UC Santa Barbara scientists have made a discovery that has the potential for use in the early diagnosis and eventual treatment of plaque-related diseases such as Alzheimer's disease and Type 2 diabetes. 

The amyloid diseases are characterized by plaque that aggregates into toxic agents that interact with cellular machinery, explained Michael T. Bowers, lead author and professor in the Department of Chemistry and Biochemistry. Other amyloid diseases include Parkinson's disease, Huntington's disease, and atherosclerosis. Amyloid plaques are protein fibrils that, in the case of Alzheimer's disease, develop prior to the appearance of symptoms.

"The systems we use are model systems, but the results are groundbreaking," said Bowers. He explained that his research provides the first examples of the conversion of randomly assembled aggregates of small peptides into ordered beta sheets that comprise fibrils. Fibrils are the final structural state of the aggregation process.

Their work is published in a recent issue of Nature Chemistry. In the article, Bowers describes how understanding the fundamental forces that relate aggregation, shape, and biochemistry of soluble peptide aggregates is central to developing diagnostic and therapeutic strategies for amyloid diseases.

Bowers and his research team used a method called ion-mobility spectrometry-mass spectrometry (IMS-MS). This method enabled the team to deduce the peptide self-assembly method. They then examined a series of amyloid-forming peptides clipped from larger peptides or proteins associated with disease.

Bowers explained that IMS-MS has the potential to open new avenues for investigating the pathogenic mechanisms of amyloid diseases, their early diagnosis and eventual treatment.

The first author of the paper is Christian Blieholder, a Humbolt Postdoctoral Fellow at UCSB. Thomas Wyttenbach, UCSB associate researcher, is a co-author. Nicholas F. Dupuis, who was a Ph.D. student at UCSB at the time of the research, is also a co-author; he is now a postdoctoral fellow at the University of Colorado.

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Journal Reference:

1. Christian Bleiholder, Nicholas F. Dupuis, Thomas Wyttenbach, Michael T. Bowers. Ion mobility–mass spectrometry reveals a conformational conversion from random assembly to β-sheet in amyloid fibril formation. Nature Chemistry, 2010; 3 (2): 172 DOI: 10.1038/nchem.945

The population of aged persons worldwide is expanding rapidly, and it is becoming increasingly clear that there are many different diseases that affect the minds of these individuals. Researchers at the University of Kentucky are breaking new ground in the ongoing project of identifying and defining those diseases most likely to affect an aged population. Dr. Peter Nelson of the University of Kentucky Sanders-Brown Center on Aging is the lead author on a paper soon to be published in the journal Brain; the paper deals with the little-understood but serious condition hippocampal sclerosis (HS-AGING).

Many different diseases may produce symptoms of dementia — defined as cognitive decline and impaired memory — in aged persons. Although Alzheimer's disease is probably the most recognized cause of dementia, HS-AGING also causes serious cognitive impairment in older adults. In those who live to a very advanced age (beyond the age of 95) HS-AGING is roughly as prevalent as Alzheimer's.

It is important for physicians and scientists to understand the unique pathology of HS-AGING, and to be able to differentiate it from other diseases, as it is only by making an accurate diagnosis that clinicians can hope to treat people who present with signs of cognitive decline.

Nelson, a neuropathologist, analyzed autopsy data from 1,100 individuals, each with substantial clinical data available from before death. The long-term clinical information was obtained through the University of Kentucky Alzheimer's Disease Center, the Nun Study and the Georgia Centenarian Study (all autopsies were performed at the University of Kentucky). The large numbers of patients and the high quality of the data enabled the research team to gather new clues about the prevalence and impact of HS-AGING.

"We and others have shown previously that HS-AGING has a strong impact on cognition. The goal of the new study was to define HS-AGING as a distinct disease entity," said Nelson.

"There were some surprises. The high prevalence of HS-AGING in individuals older than 95 was unexpected. In addition, by analyzing neuropathological data alongside clinical data, we were able to determine that there is a recognizable cognitive profile for individuals likely to develop HS-AGING," said Nelson.

In the future, clinicians may be able to utilize cognitive tests with increased accuracy to differentiate a diagnosis of HS-AGING from a general diagnosis of cognitive decline. Being able to pinpoint the cause of cognitive decline may lead to better and more accurate diagnosis and treatment of aging individuals who present with signs of dementia.

"This is an extremely exciting paper because it provides the largest study of HS-AGING in the literature to date, by far. These studies help to define the cognitive features, pathological features, and risk factors that correlate with HS-AGING," said Linda Van Eldik, director of the Sanders-Brown Center on Aging and co-author of the paper.

The next step for Nelson will be to use a grant from the NIH (through the Alzheimer's Disease Genetic Consortium) to study HS-AGING from a genomic approach.

"We want to show the specific genetic fingerprint of HS-AGING so that we can begin to develop ways of better diagnosing and curing the disease during life," said Nelson. "Our ultimate goal is to prevent or cure the disease, and a greater understanding of the disorder at the genetic and biological levels is critical. Dr. Nelson's studies are providing the essential foundation required for translating the science into new therapies for the Commonwealth of Kentucky and well beyond," summarized Van Eldik.

Peter Nelson is the recipient of a newly approved grant from the National Institutes of Health (NIH) to conduct a study of HS-AGING genetics.

A new study from the Centre for Addiction and Mental Health (CAMH) has found evidence suggesting that a variation of a specific gene may play a role in late-onset Alzheimer's, the disease which accounts for over 90% of Alzheimer's cases. This innovative study has combined genetics and brain imaging to determine who may be at risk for developing late-onset Alzheimer's disease long before symptoms appear.

The gene, which is called brain-derived neurotrophic factor (BDNF), is crucial to maintaining healthy function of the brain, primarily the brain's memory centre of the hippocampus and entorhinal cortex, and is responsible for learning and memory function. Past research has found that less BDNF is present in the memory centre of those diagnosed with Alzheimer's disease. However genetic association studies alone have not produced definite findings regarding this gene. Instead, a combination of genetics and brain imaging were used to demonstrate clear effects of this gene in the brain.

In the study published in the Archives of General Psychiatry, a variation of the BDNF gene called val66met, was tracked and examined in healthy individuals to see what effect it had on the brain. Genotyping was used to determine which study participants carried the gene variation. Then two types of brain imaging — high-resolution magnetic resonance imaging (MRI) cortical thickness mapping and diffusion tensor imaging (DTI) (an MRI-based technique that measures key structural connections in the brain)– were applied to measure the physical structures of the brain in each individual. This combination of genetic screening and imaging found that BDNF val66met gene variation influenced exactly those brain structures and connections that deteriorate at the earliest phases of Alzheimer's disease.

"Our sample consisted of healthy adults who passed all cognitive testing and displayed no clinical symptoms of Alzheimer's disease, yet the brains of those who carried the gene variation had differences in their brain structures consistent with changes we see in people at the earliest stages of Alzheimer's disease," said Dr. Aristotle Voineskos, physician and scientist at CAMH, and principal investigator of the study.

Participants who carried the variation were more likely to have thinner temporal lobe structures and disrupted white matter tract connections leading into the temporal lobe — the same structures and neural networks that have deteriorated in the brains of Alzheimer's patients when their brains are examined post-mortem.

"In the past, Alzheimer's disease could only be diagnosed and treated once outward symptoms became present," added Dr. Voineskos. "Early identification is key because, in addition to seeking therapeutic treatments early to reduce suffering, delaying Alzheimer's onset by only two years has the potential of saving the Canadian health care system nearly $15 billion over the next 10 years. The combination of brain imaging and genetics is a key approach that may help us to identify people at risk for Alzheimer's disease."

This breakthrough in image-genetics research can be valuable in the research of other brain diseases and will enable researchers to examine how a gene affects the brain and possibly intervene before a person develops an illness.

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Journal Reference:

1. A. N. Voineskos, J. P. Lerch, D. Felsky, S. Shaikh, T. K. Rajji, D. Miranda, N. J. Lobaugh, B. H. Mulsant, B. G. Pollock, J. L. Kennedy. The Brain-Derived Neurotrophic Factor Val66Met Polymorphism and Prediction of Neural Risk for Alzheimer Disease. Archives of General Psychiatry, 2011; 68 (2): 198 DOI: 10.1001/archgenpsychiatry.2010.194

Like two unruly boys who need to be split up in class, a pair of protein molecules work together to speed up the toxic events of Alzheimer's disease. Researchers at the UT Health Science Center San Antonio February 4 announced the discovery of the second molecule and said its identification could lead to drugs that disrupt the interaction, and thereby block or slow Alzheimer's onset or progression.

Alzheimer's disease is an irreversible, progressive brain disease marked by deterioration of nerve cells and eventual complete loss of cognitive functioning — thinking, memory and reason. Many Alzheimer's patients have brain lesions called amyloid plaques, which consist of protein fragments called amyloid-beta. Small aggregates of amyloid-beta are thought to contribute prominently to the degeneration of brain cells in Alzheimer's.

How genes are activated

The discovery involves an amyloid beta fragment called AICD. Scientists have known that AICD controls expression of genes that contribute to Alzheimer's, but how it did so was unclear — until now. "We discovered a protein molecule that communicates with AICD to turn on target genes," said Thomas G. Boyer, Ph.D., professor of molecular medicine at the Health Science Center. "We hope to exploit this knowledge to identify compounds or drugs that can disrupt these signals, leading to a novel and effective treatment for this disease."

Alzheimer's disease is the most common cause of dementia among older people, and estimates indicate that as many as 5.3 million Americans suffer from it. While several drugs approved by the U.S. Food and Drug Administration can temporarily slow worsening symptoms, no treatment is currently available to slow or stop the degeneration of nerve cells that lies at the root of the disease.

The finding is in the Feb. 4 issue of EMBO Reports, published by the European Molecular Biology Organization. The research is the doctoral dissertation of Xu Xuan, a student in Dr. Boyer's laboratory at the Health Science Center's Institute of Biotechnology. The other co-author is Haiying Zhou, who obtained her Ph.D. in the Boyer laboratory and is pursuing postdoctoral studies at the University of California, Berkeley.

"Nucleolus," or small nucleus, is the term coined by early biologists for the tiny structure within the nucleus which they saw under the microscope. In this structure within the nucleus, RNA molecules and proteins are assembled to form ribosomes, the true protein factories of cells.

Defective nucleoli have been implicated in several rare hereditary diseases, most recently also in neurodegenerative disorders such as Alzheimer's and Huntington's disease. Despite intense research efforts around the world, the molecular causes of Parkinson's disease are still unclear. Under the leadership of Dr. Rosanna Parlato, scientists from the departments of Professor Dr. Guenther Schuetz and Professor Dr. Ingrid Grummt at DKFZ have investigated whether the demise of nucleoli also plays a role in this disease, which is also known as "shaking palsy."

The investigators studied dopamine-producing neurons in the brain of Parkinson's disease patients under the microscope. When Parkinson's disease occurs, this type of cells malfunctions and dies, causing the characteristic palsy symptoms. Indeed, the majority of nucleoli in these cells were found to be defective.

This discovery caused the group to investigate whether disrupted nucleoli may really cause Parkinson's-like symptoms or whether this was only an incidental finding. To this end, they modified the DNA of mice in such a way that the dopamine-producing cells of the experimental animals could only form defective nucleoli. These mice showed symptoms resembling Parkinson's disease, such as characteristically impaired movements. In addition, the dopamine-producing neurons in their brain died prematurely.

In order to find out why these symptoms occur, the researchers took a closer look at all functions of the genetically modified cells. And they found an important change: The activity of the mTOR enzyme, a key regulator of intracellular signaling pathways, was reduced in the genetically modified cells. As a result of reduced mTOR activity, the function of mitochondria, the cellular power plants, is disrupted. This functional disruption causes oxidative stress within the cell; highly reactive oxygen compounds accumulate and cause damage to a multitude of molecules in the cell.

"Defective nucleoli apparently cause oxidative stress in cells. This can lead to massive cell damage and may be a key prerequisite for the typical nerve damage of Parkinson's disease," says Dr. Rosanna Parlato. "The dopamine-producing neurons are particularly sensitive to oxidative stress." However, the scientists are not sure whether the damage in the nucleoli is really the sole cause of this neurodegeneration. "In any case, the nucleolus functions as a stress sensor showing us that a cell is in danger."

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Journal Reference:

1. C. Rieker, D. Engblom, G. Kreiner, A. Domanskyi, A. Schober, S. Stotz, M. Neumann, X. Yuan, I. Grummt, G. Schutz, R. Parlato. Nucleolar Disruption in Dopaminergic Neurons Leads to Oxidative Damage and Parkinsonism through Repression of Mammalian Target of Rapamycin Signaling. Journal of Neuroscience, 2011; 31 (2): 453 DOI: 10.1523/JNEUROSCI.0590-10.2011

Researchers from the Institute of Biotechnology and Biomedicine and the UAB Department of Biochemistry and Molecular Biology have developed and patented a method using Saccharomyces cerevisiae yeast to detect in human proteins the formation of oligomers, small toxic aggregations of molecules which can initiate the assembly of amyloid fibres found in neurodegenerative diseases. The test allows validating the efficacy of compounds which could dissolve or inhibit these aggregates, as well as studying at basic level the therapeutic potentiality of a large number of molecules.

Oligomers are formed by the union of two to twenty molecules. Recent research studies seem to indicate that their toxicity is higher than that of amyloid fibres. However, studying these substances is not easy given that they are unstable and their formations are transitory.

The method developed by researchers at UAB locates and monitors in vivo the aggregation process of the protein using fluorescence techniques and without the need to resort to alternative methods. It also allows studying compounds which inhibit oligomers as potentially therapeutic mechanisms to prevent posterior formations of amyloid plaques.

The screening system was carried out by genetically modifying Saccharomyces cerevisiae yeast to link human protein aggregation to cell death. It is based on the fusion of the human peptide under study with the human variant of a protein needed for the survival of the modified yeast, dihydrofolate reductase (DHFR). The aggregation of the peptide deactivates the DHFR protein and finally produces the death of the cell, thereby providing a detection system of molecules with tendency to aggregate and in which any compound capable of separating or inhibiting this aggregation would favour the survival of the cell.

Researchers carried out the study with the AB42 peptide, the main cause of Alzheimer's disease. To validate the test they worked with several compounds in vitro which, in studies related to the disease, had demonstrated to be effective against the formation of oligomers, amyloid fibres or both types of molecules. The system only showed to be effective with compounds affecting oligomers, which makes it a very specific method for the initial detection of the aggregation process. The system was also validated with chaperones, a group of proteins which increase the dissolution of protein aggregation and favour cell survival. In addition to AB42, researchers validated the assay with regard to the detection of initial aggregations, by using proteins involved in Parkinson's and Huntington's disease.

According to Salvador Ventura, one of the authors of the study, the system is easy to use and allows scientists to work quickly and to analyse with reliability the potential therapeutic efficacy of an infinite number of compounds at experimental level. Now there is the need to automate the system — with plates allowing for the simultaneous analysis of more than fifty molecules per assay — to be used in basic research. For the moment the system has been patented by the researchers.

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Journal Reference:

1. Montse Morell, Natalia S. de Groot, Josep Vendrell, Francesc X. Avilés, Salvador Ventura. Linking amyloid protein aggregation and yeast survival. Molecular BioSystems, 2011; DOI: 10.1039/c0mb00297f

Research from the University of California, San Diego School of Medicine provides new clues for the compulsive behavior and cognitive defects associated with a rare childhood neurological disease called Lesch-Nyhan Disease (LND). Two pathways found to be defective in LND are known to be associated with other neurodegenerative disease, such as Alzheimer's and Parknson's diseases, suggesting common causes of cognitive and behavioral defects in these neurological disorders.

The research is published online January 29 in the PLoS ONE.

"This study is important because it opens completely new and unexpected areas of research into the genetic cause of compulsive and self-injurious behavior in Lesch-Nyhan disease," said principal investigator Theodore Friedmann, MD, professor of pediatrics at UCSD's Center for Neural Circuit and Behavior and Rady Children's Hospital-San Diego, a research and teaching affiliate of the UCSD School of Medicine.

"We think that the findings also have implications for far more common diseases related to the central nervous system, such as Alzheimer's and Parkinson's diseases, since defects similar or related to those that we've found are also seen in other neurodegenerative diseases — suggesting common mechanisms for some of the cognitive, behavioral and neurological defects in all these disorders," Friedmann added.

LND is an inherited disease caused by a deficiency of the HGPRT enzyme, produced by mutations in the HPRT gene located on the X chromosome, which causes a build-up of uric acid in all bodily fluids. The rare disorder, first identified by medical student Michael Lesch and his mentor, William L. Nyhan — currently a research professor of pediatrics at UC San Diego School of Medicine — is almost always seen in males. Complications usually appear in the first year of life, with neurological signs including poor muscle control and moderate cognitive deficiencies. A particularly disturbing aspect of the disease is uncontrollable and involuntary compulsive self-mutilating behaviors, characterized by lip and finger biting.

The late J. Edwin Seegmiller, MD, a pioneer in the field of human genetics and founding faculty member of the UCSD School of Medicine, first found that the HGPRT enzyme was missing in children with Lesch Nyhan Disease. Friedmann — who had studied in the Seegmiller lab at the National Institutes of Health and later joined UCSD's pediatric department — was the first to isolate and study the human HPRT gene.

Now Friedmann and his team have discovered a connection between defects in the HPRT gene and two well-known signaling pathways. These defects were known to be associated with other neurological diseases including Parkinson's, Alzheimer's and Huntington diseases, but they had not previously been connected to LND.

HPRT is one of what is known as "housekeeping genes" that are expressed in most cells and usually thought to have simple functions in regulating metabolism and not necessarily in regulating complex processes in embryonic and neurological development. However, in 2009, Friedman's lab showed that HPRT plays an important role in affecting how transcription factor genes are expressed, and thus helps regulate important developmental pathways.

In this study, the researchers identified a number of signaling pathways that are significantly altered in HPRT-deficient cells, including aberrations related to the Wnt and presenilin (PS)-1 pathways. Wnt signaling controls many aspects of vertebrate development and biological processes including stem cell self-renewal and differentiation and neural pathway development, among others. Defects in the PS-1 signaling pathway play a causal role in forms of familial Alzheimer's disease, and also interact with Wnt.

Analyzing microarray-based gene expression data, the researchers found that the abnormal purine metabolism found in patients with LND causes defects in these two pathways. Interactions between the Wnt and PS-1 signaling pathways also suggest that they may cooperate in other neurodegenerative diseases.

"Such similarities in cell function are not likely to be coincidental," said Friedmann. "Instead, they offer important clues to cognitive defects and open up new targets for therapies to treat these diseases."

Additional contributors include first author Tae Hyuk Kang and Ghiabe-Henri Guibinga, both at UC San Diego and Rady Children's Hospital-San Diego.

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Journal Reference:

1. Tae Hyuk Kang, Ghiabe-Henri Guibinga, Theodore Friedmann. HPRT Deficiency Coordinately Dysregulates Canonical Wnt and Presenilin-1 Signaling: A Neuro-Developmental Regulatory Role for a Housekeeping Gene?PLoS ONE, 2011; 6 (1): e16572 DOI: 10.1371/journal.pone.0016572