A key NCATS approach to solving translational problems is to focus on improving scientific methods and tools that can speed the translation of laboratory discoveries into new treatments for patients. NCATS scientists demonstrate the potential of new approaches by incorporating them into a broad range of drug discovery and development projects. Ultimately, these new platforms and ideas can have far-reaching effects as NCATS scientists disseminate them to members of the larger scientific community for adoption in their own studies.
With support from the Michael J. Fox Foundation for Parkinson's Research (MJFF), James Inglese, Ph.D., director of NCATS' Assay Development and Screening Technology Laboratory, and Richard Youle, Ph.D., of the National Institute of Neurological Disorders and Stroke, are leading a project that showcases how NCATS' chemical screening resources can advance development of potential therapeutics for a broad range of diseases.
"This Parkinson's disease research project embodies what the NCATS mission is all about: the use of innovative approaches to enhance our ability to discover and develop therapeutics to better treat patients," Inglese said.
Over the past several years, Youle and his colleagues have unraveled a molecular pathway that appears to be involved in Parkinson's disease, a brain disorder marked by shaking (tremors) and problems with walking, movement and coordination. Progressive death of neurons (brain cells) in an area of the brain that controls movement leads to these symptoms. Scientists believe one cause of this neuronal death is dysfunctional mitochondria, which often are referred to as a cell's "powerhouse" because they generate the energy cells need to function. Defective mitochondria leak toxic substances that have the potential to damage or destroy a cell. Normally, a protein called parkin signals the cell to destroy and remove faulty mitochondria, but for patients with Parkinson's, this maintenance mechanism is disrupted.
Youle's group suspected that finding a chemical compound that enhances parkin activity could potentially prevent mitochondrial-induced damage and neuronal death. The compound would open a new therapeutic avenue for treating Parkinson's disease. But the team needed a way to screen for such candidate compounds.
Enter Inglese's group, which designs and creates assays that can be used to screen chemical libraries for compounds that have therapeutic potential in a specific disease. A postdoctoral researcher from Youle’s team, Sam Hasson, Ph.D., had been studying the parkin pathway and teamed with Inglese to develop an assay using neuron-like cells grown in a lab.
Together, the project team integrated a new screening technology developed by Inglese and his team called coincidence reporting, which uses biological tools known as reporter genes. Through a process called genome editing, the researchers insert two reporter genes within the natural DNA sequence of a gene of interest — in this case the gene for parkin — where they produce detectable signals such as light when the gene under study is expressed.
In contrast to the traditional practice of using a single reporter gene, the integration of two different reporters within the gene of interest enables scientists conducting a screen to look for two coinciding signals to indicate that the gene of interest has been affected.
Using the coincidence reporting method, the team is conducting quantitative high-throughput (large scale) screening, or qHTS, with NCATS' chemical libraries to identify compounds that increase parkin activity. Inglese and colleagues developed qHTS, a method that involves testing compounds at multiple concentrations instead of one. Screening at multiple concentrations increases the probability of finding potential hits. The NCATS libraries include a collection of about:
- 400,000 small molecules with known biological activities or the potential to affect biological functions,
- 25,000 chemical compounds derived from natural product extracts, and
- 2,750 compounds that already have been approved to treat another condition or have been tested in human studies.
The MJFF funding supports the team’s efforts to develop assays, complete the screening, analyze the results and perform follow-up studies with the most promising compounds to narrow down a list of a small number of potential therapeutics. Measuring their efficacy in flies and mice will follow. The hope is to test the best candidates for their ability to treat Parkinson's in human patients.
Although the MJFF support is specific to potential treatments for Parkinson's disease, the compounds identified could be used to treat a number of rare diseases also marked by mitochondrial dysfunction. "By screening for potential therapeutics targeting a disruption that occurs in a number of conditions in addition to Parkinson's, we may be able to treat many disorders instead of just one," Youle said.
What's more, added Inglese, because Parkinson's gives us the opportunity to work on an innovative process, the improved screening and assay methods that will emerge can be used by other scientists to solve many other translational research problems. In this way, "not only do the patient groups benefit, but the broader scientific community also benefits because the improvements we make will be applicable to many more diseases," Inglese said. "Developing methods that benefit many can have effects far beyond those communities."
Posted July 2014