STING is dispensable during KSHV infection of primary endothelial cells
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Viruses are obligate intracellular parasites requiring host cells to replicate and spread. To prevent this, cells utilize a variety of protein receptors in order to surveil for invading viruses, with detection resulting in a signaling cascade and the establishment of the antiviral state. Conversely, viruses employ several strategies to evade and suppress host innate immunity to facilitate replication and spread. Understanding the interplay between innate immunity and viral infection is critical for understanding factors that influence the course of infection and disease progression. In this thesis, I explored the interactions between innate immunity and Kaposi’s Sarcoma-associated herpesvirus (KSHV), an oncogenic virus. KSHV encodes several genes that target and antagonize innate immune pathways, including the cGAS-STING pathway. Previous studies indicated that the DNA sensor cGAS, and the downstream adaptor protein STING, are important for activating innate immune pathways and controlling KSHV infection. However, the role of these proteins in primary endothelial cells, the main proliferating cells in the Kaposi’s Sarcoma tumor, has not been explored. After giving background (Chapter 1) and methods (Chapter 2), I show that STING is dispensable during KSHV infection of primary endothelial cells in Chapter 3. I characterize a STING-null batch of primary lymphatic endothelial cells, which led me to investigate the importance of STING during KSHV infection of primary endothelial cells. I found that KSHV minimally induces interferon (IFN)- expression and does not detectably activate STING signaling. Furthermore, I find that genetic ablation of STING does not increase susceptibility to infection, nor does it increase the ability of KSHV to spread through the culture following lytic reaction. In Chapter 4, I investigate the requirement of the kinase CDC7 for survival of KSHV-infected cells. I find that pharmacologic inhibition of CDC7 leads to an increase in cell death in KSHV-infected cells compared to uninfected cells. Furthermore, I find that KSHV de novo infection decreases expression of CDC7 as well its substrate, MCM2. Additionally, I rule out either the requirement or the sufficiency of each gene in the latent locus. Overall, this thesis reveals the dispensability of STING in endothelial cells during KSHV infection and identifies CDC7 as required during KSHV latency. These experiments improve our understanding of host-virus interactions and provide new targets for therapy in KS patients.
- Microbiology