An Zhou, Ph.D.
Our three-pronged approach:
- High throughput quantitative proteomics utilizing the latest mass spectrometry, protein labeling and bioinformatic tools. This enables us to contrast protein profiles of different ischemic conditions, as a means to identify effector proteins of a particular ischemic condition.
- Studying protein biosynthesis by individually defined cellular mechanisms. For proteins of interest, we investigate in detail the rate of biosynthesis, stability, post-translational modifications and modification enzymes involved, subcellular localization and trafficking, as well as regulation of these processes. By doing so, we aim to pin-point which steps would have the greatest potential for developing therapeutic agents in treating neuronal ischemic injury.
- Including multiple neuronal ischemic models. In parallel, we study neuronal ischemia in both brain and retina. Besides the obvious significance to human health, we believe a principle understanding of the underlying mechanisms needs to be tested in different neuronal tissues and organs.
CURRENT RESEARCH PROJECTS
Quantitative proteomic reconfiguration in induction of neuroprotection against stroke.
From Drosophila to human, as well as in plants, a broad spectrum of genes are under the control of a multi-component, epigenetic regulatory machinery, the PcG/TrxG complex. PcG (Polycomb group) and TrxG (Trithorax group) proteins exert opposing actions (repressing vs. activating) in transcriptional regulation. The ultimate expressiveness of the target genes depends on the makeup of the PcG/TrxG complex. Recently, by combining quantitative proteomics, cell biology, molecular biology and physiological studies, we have identified a PcG-mediated mechanism that protects the brain from an otherwise injurious ischemic insult (Stapels et al., 2010). Follow-up studies suggest that members of TrxG proteins may also be involved. This mechanism may also operate in the ischemic retina (Stowell et al., 2010). The project aims to quantitatively describe stoichiometric changes of the PcG/TrxG complex under different ischemic conditions, over time, to help us to understand how this machinery function and how to modulate it.
Translational and post-translational regulation of PcG proteins.
Several lines of evidence indicate that in neuronal tissues and cells that are made resistant (tolerant) to ischemic injury (e.g. by a sub-lethal, preconditioning ischemia), there is a rapid increase in PcG protein levels, and such an increase is independent of gene transcript levels (Piper at al., 2010, SfN Poster #153.7/K19). Using the latest Click protein labeling technique, we have shown that the nascent proteome, i.e. the proteome consisting of newly synthesized proteins, of ischemic-injured or ischemic-tolerant neuronal cells is enriched with translational regulation processes (Zhou et al., 2011). We also know that PcG proteins are subject to post-translational modifications, which are essential for their function as epigenetic regulators. We aim to characterize the biosynthesis of PcG proteins under different conditions, and seek how neuroprotection may be achieved by controlling PcG protein biosynthesis.
Epigenetic regulation of endogenous neuroprotection in retinas.
The retina presents a unique model system for studying neuronal stress response, since it can be subjected to multiple stresses simultaneously such as light, pressure (intraocular pressure, IOP) and ischemia (either by high IOP or blood vessel blockade). Currently, our work is focused on high IOP-induced ischemic injury and its prevention. We and others have shown that ischemic retinal injury can be prevented if the retina is first exposed to a brief preconditioning high IOP prior to an otherwise injurious high IOP. Hence in retina, an endogenous protective mechanism can apparently be brought into action by a preconditioning high IOP, a phenomenon similar to what observed in brain. Results of our initial examination of ischemic-injured and ischemic-tolerant retinas demonstrate changes of a number of PcG and histone proteins, suggesting the involvement of an epigenetic mechanism (Stowell et al., 2010). The objective of this project is to dissect molecular events during the development of ischemic injury and its tolerance in retina, and compare them to that in brain, at both transcriptional and translational levels.
Stroke occurs more often and is more lethal in African Americans than in Caucasians. As a part of the Translational Program in Stroke at Morehouse School of Medicine, we use our expertise in proteomics and protein biosynthesis to assist the identification of protein biomarkers for stroke in African Americans of the Southeast Stroke Belt. Current efforts focus on characterizing proteomes of the peripheral blood of African American stroke patients.
Research Key Words: proteomic, epigenetic, polycombs proprotein, processing, proteolytic, biosynthesis, neuropeptides.