The two studies, one published in the journal Proceedings of the National Academy of Sciences (PNAS), the other in the journal ASSAY and Drug Development Technologies, could lead new approaches to some of the most problematic diseases facing a rapidly aging world population, including Alzheimer’s and Huntington’s diseases and dementia.
“We are actively looking at molecules critical to memory formation, so these two studies work in parallel,” said Sathyanarayanan V. Puthanveettil, a TSRI biologist who led both studies. “In one study, we’re reaching for a basic understanding of the process, and in the other, we’re finding new ways to identify drug candidates so that we can cure these diseases.”
Unlocking the ‘Synaptic Proteome’
The PNAS study is one of the first detailed descriptions of the proteins that are transported to the synapses, which as a group are called the “synaptic proteome.” Synapses are the part of a nerve cell (neuron) that passes electrochemical signals to other cells during functions such as memory storage. This new approach has the potential to advance our understanding of how synapses work, how their composition changes with learning and how brain diseases might affect them.
“We know these molecules function in the synapse, and if we can regulate their function there may be some very good therapeutic opportunities there,” Puthanveettil said.
The study focuses on kinesin, a molecular motor protein that plays a role in the transport of other proteins throughout a cell.
Analyzing three kinesin complexes, the researchers found that approximately 40 to 50 percent of the protein cargos were synaptic proteins—and that the identity and location of these kinesins determine which proteins they transport. These results reveal a previously underappreciated role of kinesins in regulating the composition of the entire synaptic proteome.
Interestingly, a bioinformatics analysis revealed the three kinesin cargo complexes examined in the study are involved in neurologic diseases. Approximately 60 cargos (out of 155) of the kinesin Kif5C are implicated in psychiatric disorders, while around 20 cargos of another kinesin Kif3A are implicated in developmental disorders.
“This shows for the first time how kinesins expressed in the same neurons can carry substantially different cargos,” said Research Associate Xin-An Liu, the first author of the study. “We can use this approach to identify what molecules may be targeted for memory and in major disorders. The next step is to find how the synaptic proteome changes in neuropsychiatric diseases.”
Toward New Drug Candidates
In the ASSAY study, Puthanveettil and his colleagues describe their new high-throughput screening test for discovering potential drug candidates based on kinesin and axonal transport for the treatment of memory disorders.
“The luminescence-based assay that we developed is highly reproducible and robust,” said Puthanveetil.
Using the approach, the team screened a compound collection and identified a number of small molecules that turned on or off activity of a human kinesin.
In addition to Liu and Puthanveettil, other authors of the PNAS study, “New Approach to Capture and Characterize Synaptic Proteome,” include Beena Kadakkuzha, Bruce Pascal, Caitlin Steckler, Komolitdin Akhmedov and Michael Chalmers of The Scripps Research Institute; and Long Yan of Max Planck Florida Institute for Neuroscience. See http://www.pnas.org/content/early/2014/10/28/1401483111.abstract
This study was supported by the Whitehall Foundation and the National Institute of Mental Health of the National Institutes of Health (R21MH096258-01A1).
In addition to Puthanveettil and Kadakkuzha, authors of the ASSAY study, “High-Throughput Screening for Small Molecule Modulators of Motor Protein Kinesin,” include Timothy Spicer, Peter Chase, Jeffery B. Richman and Peter Hodder (present address: Amgen, Inc.) of TSRI. See http://online.liebertpub.com/doi/abs/10.1089/adt.2014.579
This work was supported by the Alzheimer’s Drug Discovery Foundation, Margaret Q. Landenberger Research Foundation and TSRI.
About The Scripps Research Institute
The Scripps Research Institute (TSRI) is one of the world’s largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs about 3,000 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists—including two Nobel laureates—work toward their next discoveries. The institute’s graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see www.scripps.edu.
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