Research

Overview

Research in the Li group focuses on developing and implementing an array of novel mass spectrometry (MS) based strategies to answer questions about the most complex and elusive set of signaling molecules, the neuropeptides, and gain new insights into the roles of peptide hormones and neurotransmitters play in the plasticity of neural circuits and behavior. As such, our research program emphasizes two interlinked aspects. First, we plan to develop and apply enabling mass spectrometric tools coupled with front-end microseparation strategies that are capable of global analysis of peptides and proteins in complex biological matrices in a high throughput and high sensitivity manner. Secondly, with the improved analytical methodologies and techniques, we aim to advance our knowledge in neuropeptidergic signaling and neuroproteomics and their applications in biomedicine and drug discovery.

While significant effort has been directed to analytical technique and method development, it is the biomedical importance of understanding the neuropeptidergic system that drives our research to continuously refine and improve the analytical capabilities to address challenging neuroscience problems. Specifically, we are interested in understanding the molecular aspects of neuropeptidergic systems in the regulation of feeding behavior and cardiovascular function in decapod crustaceans. The crustacean nervous systems are chosen due to the extensive knowledge about peptidergic signaling in the system and the technical advantages of investigating neuromodulation and hormonal regulation in these well-defined neuronal networks. We are also conducting the first comparative neuropeptidomic analysis in a relatively large collection of decapod crustacean species (in collaboration with Dr. Andrew Christie at the University of Washington) to gain important knowledge on the large chemical diversity and molecular evolution of neuropeptides. Our short-term goal is to develop a robust analytical measurement platform for neuropeptide analysis and generate volumes of useful information on neuropeptides in crustacean model systems.

Although the methodology is developed using crustacean model system as a test-bed, the technology advancement resulting from our research is widely applicable to the large-scale analysis of peptides and proteins in many biological systems, including those of mammalians and human. Towards this end, we have initiated a number of exciting collaborations targeted to neurochemical analysis in mammalian systems. These collaborative projects include the investigation of peptidergic signaling in opioid-mediated feeding behavior in rats using microdialysis sampling followed by MS-based approaches (in collaboration with Dr. Ann Kelley), the discovery of prion disease biomarkers in cerebral spinal fluids and serum (in collaboration with Dr. Judd Aiken), and the proteomic analysis of neuroprotective pathways in Alzheimer's Disease (in collaboration with Dr. Jeff Johnson). We expect that these exciting collaborations will help to transform advances in analytical tools into important findings leading to biological insight and biomedical breakthrough.

In summary, our research will (a) develop improved MS-based methods for neuropeptide and protein analysis both at large-scale and micro-scale and (b) provide essential information on understanding the mechanisms of neuromodulation of behaviorally relevant neural circuits and peptide regulation and peptide evolution. Our research program can be described as bioanalytical, but combining aspects of biological mass spectrometry, peptide/protein biochemistry, microseparations, neuropharmacology, neurochemistry, immunochemistry, and bioinformatics. The interdisciplinary nature of our research program transcends the traditional boundaries of each individual field, and takes advantage of the power and rigors of analytical tools to advance exciting neurochemical research and discovery.

Method Development

• In-Situ Peptide Analysis of Neuronal Tissues and Single Cells by MALDI FTMS
• Coupling Immunoaffinity Depletion/Enrichment with High Resolution MALDI FTMS
• Multidimensional Fractionation and Capillary Separation Methods coupled to Both MALDI FTMS and ESI QTOF MS/MS Analyses for Peptide Identification and Characterization of Posttranslational Modifications (PTMs)
• Developing a Hybrid Strategy Employing De novo MS/MS Sequencing Followed by Sequence Homology Database Searching for Peptide Discovery
• Differential Isotopic Labeling for Improved De Novo MS/MS Peptide Sequencing and Quantitative Analysis of Neuropeptides and Proteins
• Developing Peptide Elution Time Prediction and Accurate Mass Methodology for Large-Scale Peptide Identification
• In vivo Microdialysis Sampling Coupled to LC/MS Analysis of Neuropeptides

Biological Projects

• Discovering new neuropeptides and neurohormones in the stomatogastric nervous system (STNS) of Cancer borealis and Cancer productus
• Profiling Neuropeptides and Neurohormones in Crustacean Hemolymph
• Comparative Neuropeptidomic Analysis of Thoracic Ganglion from Decapod Crustaceans (in collaboration with Dr. Andrew Christie)
• Investigation of Single-Cell Neuropeptidomes in Crustacean STNS
• A Peptidomic Approach to the Neuroendocrine Regulation of Feeding Behavior in Decapod Crustacean
• Pericardial Organ Peptidomics for Neurohormonal Regulation of Crustacean Cardiovascular System
• Neuronal Circuit Modulation and Regulation by Neuropeptides (in collaboration with Dr. Eve Marder)
• Characterization of Crustacean Pyrokinin-Related Peptides (in collaboration with Dr. Michael Nusbaum)
• Peptidergic Signaling in Opioid-Mediated Feeding Behavior in Rats (in collaboration with Dr. Ann Kelley)
• Discovering Prion Disease Biomarkers in Cerebral Spinal Fluids and Serum (in collaboration with Dr. Judd Aiken)
• Proteomics in Alzheimer's Disease (in collaboration with Dr. Jeff Johnson)
• Neuroactive Peptides in Medicinal Leech (in collaboration with Dr. Karen Mesce and Dr. Brian Norris)