Saumendra N. Sarkar, Ph.D.
Campus: 5517 Centre Avenue
Office: HCCLB 1.8
Lab: HCCLB 1.7
Pittsburgh, PA 15213
- BS Presidency College, University of Calcutta
- MS University College of Science and Technology, University of Calcutt
- PhD Molecular Biophysics Unit, Indian Institute of Science
- Associate Professor, Dept. of Microbiology and Molecular Genetics; Dept. of Immunology
- Member, Immunology Graduate Program
- Member, Molecular Virology And Microbiology Graduate Program
- Member, Cancer Virology Program
Our research is primarily focused on the innate immunity, particularly the cellular signaling pathways involved in Interferon induction during virus infection and cancer. The host defense against RNA or DNA virus infection is initiated by innate immune receptors such as RIG-I (Retinoic acid-inducible gene I)-like (RLR), Toll-like receptors (TLR) and specific DNA-sensors through the detection of non-self nucleic acids. This initiates the cellular innate immune response, primarily mediated by type I interferons (IFN), and shapes subsequent adaptive immunity. Although several basic principles of virus detection and host signaling have been identified, the specific mechanisms by which these pathways are modulated by host components remains poorly understood.
We have been systematically defining regulatory mechanisms during the early and late phase of viral RNA detection and the signaling. We showed that in non-hematopoietic cells in addition to RIG-I activation by viral RNA, additional stimuli, e.g. Ca2+ mobilization, PKC activation are necessary for optimal IFN induction and protection against virus replication. These stimuli activated a separate signaling cascade allowing optimum IRF3 activation and IFN induction (Zhu et al, 2011). However, following initial induction of IFN, a number of IFN-stimulated genes (ISG) are induced, which again profoundly modulate the RLR signaling pathway – the so called late modulators. One such protein Oligoadenylate synthetase-like (OASL) increases the sensitivity of RIG-I signaling by mimicking one of the RIG-I-ligand, and exerts a strong antiviral activity against multiple RNA viruses (Zhu et al, 2014) Yet another protein, MOV10 (Moloney leukemia virus 10 homolog) seemed to be involved in initiating another parallel signaling process when stimulated by viral RNA (Cuevas et al, 2014). Therefore, these modulators together control and fine tune the antiviral innate immune response, which can be targeted for future development of novel therapies against specific viral diseases.
Another major interest of my lab is to define the role of innate immune responses, specifically IFN response in shaping tumorigenesis and metastasis. Many cancers, especially carcinomas, appear to induce a spontaneous adaptive T cell response in the early stages of tumor development, and the presence of this T cell infiltrate has been linked to favorable clinical outcome in multiple cancer types. Recent results have indicated that tumors can induce type I Interferon (IFN) production in the tumor microenvironment (TME), which is required for a spontaneous T cell response in vivo. However, the innate immune pathways that induce this IFN production, and promote the adaptive immune response under sterile conditions are poorly understood. Using viral oncoprotein expression, we found that the DNA-damage response induced in many tumor cells due to their high replication stress may be responsible for this IFN induction in the TME (Forero et al, 2014). Another recently discovered IFN induction pathway mediated by DNA-sensor signaling also contributes to this process (Ohkuri et al, 2014). Currently, we are focused on understanding these signaling processes that are involved in inducing IFN in the TME.
McCormick, K.D., Ghosh, A., Trivedi, S., Wang, L., Coyne, C.B., Ferris, R.L., and Sarkar, S.N. (2016) Innate immune signaling through differential RIPK1 expression promote tumor progression in head and neck squamous cell carcinoma. Carcinogenesis. 37, 522-529.
Cuevas, R.A., Ghosh, A., Wallerath, C., Hornung, V., Coyne, C.B., and Sarkar, S.N. (2016) MOV10 Provides Antiviral Activity against RNA Viruses by Enhancing RIG-I-MAVS-Independent IFN Induction. J Immunol. 196, 3877-3886.
Zhu, J., Zhang, Y., Ghosh, A., Cuevas, R.A., Forero, A., Dhar, J., Ibsen, M.S., Schmid-Burgk, J.L., Schmidt, T., Ganapathiraju, M.K., Fujita, T., Hartmann, R., Barik, S., Hornung, V., Coyne, C.B., and Sarkar, S.N. (2014) Antiviral activity of human OASL protein is mediated by enhancing signaling of the RIG-I RNA sensor. Immunity. 40, 936-948.
Ohkuri, T., Ghosh, A., Kosaka, A., Zhu, J., Ikeura, M., David, M., Watkins, S.C., Sarkar, S.N., and Okada, H. (2014) STING contributes to antiglioma immunity via triggering type I IFN signals in the tumor microenvironment. Cancer Immunol Res. 2, 1199-1208.
Forero, A., Giacobbi, N.S., McCormick, K.D., Gjoerup, O.V., Bakkenist, C.J., Pipas, J.M., and Sarkar, S.N. (2014) Simian virus 40 large T antigen induces IFN-stimulated genes through ATR kinase. J Immunol. 192, 5933-5942.
Umemura, N., Zhu, J., Mburu, Y.K., Forero, A., Hsieh, P.N., Muthuswamy, R., Kalinski, P., Ferris, R.L., and Sarkar, S.N. (2012) Defective NF-kappaB signaling in metastatic head and neck cancer cells leads to enhanced apoptosis by double-stranded RNA. Cancer Res. 72, 45-55.
Zhu, J., Coyne, C.B., and Sarkar, S.N. (2011) PKC alpha regulates Sendai virus-mediated interferon induction through HDAC6 and beta-catenin. EMBO J. 30, 4838-4849.