Date of Award
12-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biology
First Advisor
Margo Brinton, PhD
Second Advisor
Richard Plemper, PhD
Third Advisor
Mukesh Kumar, PhD
Abstract
In response to viral infections and other environmental stresses, eukaryotic cells shut down global translation by assembling dynamic cytoplasmic stress granules (SGs). Viruses require cellular translation machinery for their protein synthesis and have therefore developed mechanisms to subvert SG assembly. The stress sensor, PKR, was found to be activated by viral dsRNA during an infection with the arterivirus, simian hemorrhagic fever virus (SHFV). However, bona fide SG formation was inhibited. Instead, G3BP1, the main nucleating protein of SGs, was redistributed into foci located adjacent to the viral dsRNA foci. LC-MS/MS analysis showed that SHFV non-structural proteins (nsps) were the most enriched proteins to co-precipitate with G3BP1 from SHFV-infected cell lysates, and reciprocal co-IP assays confirmed direct interactions between G3BP1 and SHFV proteins, nsp2 and the nucleocapsid (N) protein. A FGAP motif in nsp2 and an FAEP motif in the N protein were shown to be required for interaction with G3BP1. As an additional mechanism of SG inhibition, G3BP1 cleavage occurred during an infection, and was likely mediated by a viral protease.
An infection with SHFV causes a lethal hemorrhagic fever disease in Asian macaques but a persistent asymptomatic infection in African cercopithecid monkeys. SHFV and other simian arteriviruses genomes encodeadditional proteins, including an extra set of the minor structural proteins, that are not found in non-simian arterviruses. Only SHFV and two other simian arteriviruses also encode an E′ protein, which is believed to be a functionally redundant duplicate of the arterivirus envelope (E) protein. MS analysis of purified SHFV virions showed that the E′ protein is not a virion structural component. E′ was instead confirmed to localize to mitochondria by IFA and co-fractionation assays. Further analysis showed that E′ is an integral protein of the OMM and directly interacts with the selective autophagy adaptor protein, SQSTM1. Mitochondria fragmentation, indicative of mitophagy, was observed in E′ expressing cells and in SHFV-infected cells by 24 hpi. The characteristics of the E′ protein indicate that it has divergent functions from the SHFV E protein. Together, these studies provide new insights into SHFV molecular biology and viral-host protein interactions that contribute to pathogenesis.
Recommended Citation
Lavender, Ayisha, "Analysis of the stress granule response and virus-host protein interactions in simian hemorrhagic fever virus (SHFV)-infected cells." Dissertation, Georgia State University, 2024.
https://scholarworks.gsu.edu/biology_diss/280
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