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Title: Determining the role of Aedes aegypti host SUMOylation in suppressing arbovirus replication
Author: Stokes, Samuel
ISNI:       0000 0004 7654 9382
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2018
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Approximately half the world's human population is at risk of infection from mosquito-borne arboviruses. Currently, interactions between the mosquito antiviral response and infecting arboviruses remains poorly understood; deciphering these will be crucial to the development of novel methods to limit replication and transmission that could help control future outbreaks. Previous mammalian studies have shown that the Homo sapiens Small Ubiquitin-related Modifier (SUMO) pathway plays a fundamental role in multiple aspects of cell biology, including the regulation of host cell immunity. However, this pathway and its impact on arbovirus replication remain uncharacterised in mosquito hosts such as Aedes aegypti (Ae. aegypti; Aa). Comparison between the Ae. aegypti and H. sapiens (Hs) SUMOylation pathways demonstrated a high degree of amino acid sequence and structural similarity. The most notable predicted difference is the lack of ability of AaSUMO to form poly-SUMO chains, which have important functions in H. sapiens. Biochemical analysis of the AaSUMOylation pathway identified a conserved function, and confirmed that AaSUMO could not efficiently form poly-SUMO chains, unlike HsSUMO3 (its closest H. sapiens homologue) due to the absence of an internal SUMO conjugation motif. Catalytically inactive mutants revealed the necessity of AaPIAS (Protein inhibitor of activated STAT) to induce the formation of poly-SUMO chains. Confocal microscopy confirmed that AaSUMO protein is expressed in haemocytes, the salivary glands, ovaries, and midgut, all of which are sites of arboviral replication. Q-PCR investigations have also revealed the AaSUMOylation pathway to be ubiquitously expressed. In vitro depletion of the AaSUMOylation pathway led to significantly enhanced levels of Zika, Semliki Forest, and Bunyamwera virus replication, identifying a vital role for AaSUMOylation in the suppression of these arboviruses. Subsequent studies in H. sapiens cells have also identified a significant role for HsPIAS1 in suppressing the replication of Zika, Semliki Forest, and Bunyamwera viruses. Furthermore, depletion of HsSUMO1 significantly enhanced the replication of Bunyamwera virus, indicating that SUMOylation suppresses arbovirus in a virus-dependent manner. Collectively, these data have identified a novel role for the SUMOylation pathway in suppressing arbovirus replication in both the vertebrate and invertebrate species in which arboviruses replicate.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR355 Virology