BBS Faculty Member - Priscilla Yang

Priscilla Yang

Department of Microbiology and Molecular Genetics

Harvard Medical School
New Research Building, Room 930
77 Avenue Louis Pasteur
Boston, MA 02115
Tel: 617-432-5415
Fax: 617-432-5418
Email: priscilla_yang@hms.harvard.edu
Lab Members: 6 postdoctoral fellows, 1 technician
Visit my lab page here.



My laboratory uses methods drawn from both biology and chemistry to study host-pathogen interactions at the molecular and pathway levels. We develop tools to precisely manipulate and monitor the infection of host cells by viruses and then use these tools to 1) understand how viruses perturb normal biochemical equilibria in the host cell, 2) define the consequences of these perturbations, and 3) exploit this knowledge in the design and validation of new antiviral targets and strategies. Our current research models are hepatitis B virus (HBV), hepatitis C virus (HCV), and dengue virus (DENV) because they are scientifically interesting but, more importantly, because they are significant causes of human morbidity and mortality. Current research in my group spans three major areas.

First, we seek to identify cellular factors and pathways important for productive viral replication and that are candidate targets for pharmacological intervention. Through small molecule and RNAi screens, we have identified cellular kinases and bioactive lipids that regulate DENV replication in mammalian and insect cells. Using small molecule inhibitors as mechanistic probes, we have determined that Fyn kinase regulates dengue virus genome replication while Abl kinases regulate a later step in the viral life cycle, likely viral assembly and/or egress. Similarly, we have determined that fenretinide, a synthetic bioactive lipid, potently inhibits the genome replication of DENV, HCV, and other members of the
Flaviviridae. On-going efforts are aimed at elucidating the biochemical mechanism(s) underlying the effects of these small molecule inhibitors on DENV and on translating these basic discoveries. This includes preclinical efforts to “repurpose” fenretinide and existing FDA-approved inhibitors of Src and Abl kinases as potential antivirals.

Second, we seek to develop novel small molecule probes of viral processes. Through several different screening efforts, we have discovered multiple peptides and small molecule inhibitors of DENV entry. DENV entry is known to be catalyzed by the E protein on the virion surface. Attachment to factors on the host cell surface is mediated by E and triggers clathrin-mediated endocytosis. Subsequent escape of the viral nucleocapsid from the endosome and release of the genome to the cytosol requires fusion of the viral and endosomal membranes in a chemical reaction catalyzed by E upon exposure to acidic pH. The peptides and small molecule inhibitors that we have discovered act at various points after clathrin-mediated endocytosis. We are currently studying the mechanisms of action of these inhibitors in cell culture models and biochemical model systems. Since the molecular details of virus-driven membrane fusion remain obscure, these inhibitors provide valuable tools for probing the structural and biochemical mechanisms underlying this fundamental biological process. In addition, we have on-going efforts to improve the selectivity, potency, resistance profile, and pharmacokinetic properties of these inhibitors so that they can be validated as antivirals in vivo, optimization efforts that are critical to advancing DENV entry inhibitors as preclinical candidates. This work is a three-way collaboration between my group and that of Stephen C. Harrison and Nathanael Gray in the Biological and Molecular Pharmacology Department.

Third, my group is studying the essential roles of lipids in the life cycle of viral pathogens. All viruses rely upon host lipids to supply energy, to protect the viral genome, to organize viral processes within the host cell, and/or to transduce signals leading to favorable conditions for viral replication. Since little is known about the chemical composition of lipid membranes utilized by specific viruses and the relationship between lipid structure and biochemical function in viral processes, we are tackling this understudied yet fundamental aspect of host-virus interactions using a combination of chemical tools and traditional virology and biochemistry. Our studies have been developed within a framework of three related hypotheses. First, we hypothesize that there is selectivity at the molecular level in the particular lipids that are needed to optimally replicate a given virus. Second, we hypothesize that viruses have specific mechanisms to perturb host lipid metabolism in ways that lead to the increased steady-state abundance of the lipids required to support optimal viral replication. Third, we hypothesize that we can exploit the virus’s dependence on host lipids and host lipid metabolism to selectively inhibit viral pathogens. In the context of hepatitis C virus (HCV) in replication, we have demonstrated that HCV causes a greater than 10-fold increase in the steady-state abundance of desmosterol. Inhibiting desmosterol biosynthesis with small molecule inhibitors or by RNAi is not cytotoxic but drastically inhibits HCV infection by blocking replication of the viral genome. This antiviral effect can be reversed with the addition of exogenous desmosterol while the addition of other sterols that are structurally very similar has a much less profound effect on HCV. Experiments like this provide support for our hypotheses regarding HCV’s lipid selectivity, its perturbation of host lipid metabolism to benefit viral replication, and the opportunity to exploit this lipid selectivity for antiviral purposes. We are currently studying the molecular basis for these phenomena and are also interested in applying these and other chemical methods to analyze the interaction of viral pathogens with host lipids.



Last Update: 6/18/2014



Publications

Vetter, M.L., Zhang, Z., Liu, S., Wang, J., Cho, H., Zhang, J., Zhang, W., Gray, N.S., and Yang, P.L. (2014) Fluorescent Visualization of Src Using Dasatinib-BODIPY. ChemBioChem, in press DOI: 10.1002/ cbic.201402010R1

de Wispelaere, M., LaCroix, A., and
Yang, P.L. (2013) The Small Molecules AZD0530 and Dasatinib Inhibit Dengue Virus RNA Replication via Fyn kinase. Journal of Virology, 87(13):7367-81. PMCID: PMC3700292.

Vetter, M.L., Rodgers, M.A., Patricelli, M.P., and
Yang, P.L. (2012) Chemoproteomic Profiling Identifies Changes in DNA-PK as Markers of Early Dengue Virus Infection. ACS Chemical Biology, 7(12):2019-2026. NIHMSID # 410237, PMCID: PMC3528803. Chosen for the cover and author highlight

Zhang, Z., Kwiatkowski, N., Zeng, H., Lim, S.M., Gray, N.S., Zhang, W., and
Yang, P.L. (2012) Leveraging kinase inhibitors to develop small molecule tools for imaging kinases by fluorescence microscopy. Mol. BioSyst., 8(10):2523-2526. PMCID: PMC3616611. Highlighted by the journal as a HOT Article

Rodgers, M.A., Villareal, V.A., Schaefer, E.A., Peng, L.F., Corey, K.E., Chung, R.T., and
Yang, P.L. (2012) Lipid metabolite profiling identifies desmosterol metabolism as a new antiviral target for hepatitis C virus. Journal of the American Chemical Society, 134(16):6896-6899. NIHMS370147, PMCID: PMC3375380.

Schmidt, A., Lee, K.,
Yang, P.L., and Harrison, S.L. (2012) Small molecules of dengue virus entry. PLoS Pathogens 8(4): e1002627. PMCID: PMC3320583.

O.M. Sessions, N.J. Barrows, J.A. Souza-Neto, T.J. Robinson, C.L. Hershey, M.A. Rodgers, J.L. Ramirez, G. Dimopoulos,
P.L. Yang, J.L. Pearson, and M.A. Garcia-Blanco. (2009) Discovery of dengue virus host factors in insects and humans. Nature 458(7241):1047-1050.



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