The SUMOylation pathway suppresses arbovirus replication in Aedes aegypti cells

Abstract

Mosquitoes are responsible for the transmission of many clinically important arboviruses that cause significant levels of annual mortality and socioeconomic health burden worldwide. Deciphering the mechanisms by which mosquitoes modulate arbovirus infection is crucial to understand how viral-host interactions promote vector transmission and human disease. SUMOylation is a post-translational modification that leads to the covalent attachment of the Small Ubiquitin-like MOdifier (SUMO) protein to host factors, which in turn can modulate their stability, interaction networks, sub-cellular localisation, and biochemical function. While the SUMOylation pathway is known to play a key role in the regulation of host immune defences to virus infection in humans, the importance of this pathway during arbovirus infection in mosquito vectors, such as Aedes aegypti (Ae. aegypti), remains unknown. Here we characterise the sequence, structure, biochemical properties, and tissue-specific expression profiles of component proteins of the Ae. aegypti SUMOylation pathway. We demonstrate significant biochemical differences between Ae. aegypti and Homo sapiens SUMOylation pathways and identify cell-type specific patterns of SUMO expression in Ae. aegypti tissues known to support arbovirus replication. Importantly, depletion of core SUMOylation effector proteins (SUMO, Ubc9 and PIAS) in Ae. aegypti cells led to enhanced levels of arbovirus replication from three different families; Zika (Flaviviridae), Semliki Forest (Togaviridae), and Bunyamwera (Bunyaviridae) viruses. Our findings identify an important role for mosquito SUMOylation in the cellular restriction of arboviruses that may directly influence vector competence and transmission of clinically important arboviruses.

Alphavirus nsP2 protease structure and cleavage prediction: Possible relevance to the pathogenesis of viral arthritis

“…As with other viruses, modulation of SUMOylation is nontrivial and likely time-dependent; depletion of the only E2 for SUMO, UBC9, protects against CHIKV infection in mice, [94] yet depletion of SUMOylation enhances SFV replication in mosquito cells. [95] Cleavage of UBE2Q1 in muscle may disrupt B4GALT1mediated cell adhesion to laminin and promote myoblast and satellite cell differentiation and syncytia formation [96,97] to allow infection of myofibers without virion egress. [98][99][100] This is supported by the ability of alphaviruses to form filopodia-like protrusions mediating cell-to-cell transmission [101] and possibly to shield the virus from antibodies, making effective vaccination more difficult.…”

SUMOylation Is Essential for Dengue Virus Replication and Transmission in the Mosquito Aedes aegypti

“…SUMO modification is known to be well-conserved between species; including H. sapiens, D. melanogaster , and S. cerevisiae ( Epps and Tanda, 1998 ; Fraser et al, 2000 ; Apionishev et al, 2001 ; Hayashi et al, 2002 ; Urena et al, 2016 ; Li et al, 2021 ). Bioinformatic analysis of the amino acid sequence and tertiary structure of SUMO proteins, E2 conjugating enzyme (Ubc9), and SUMOylation activating heterodimer (SAE1/2) has demonstrated these high conservation rates ( Stokes et al, 2020 ; Li et al, 2021 ). Interestingly, while previous studies show most eukaryotic organisms express both a SUMO1 and SUMO2/3 paralog, insects do not possess a SUMO1 paralog, and the insect SUMO2/3 paralogs lack the SCM ( Choy et al, 2013 ; Urena et al, 2016 ).…”

“…During infection and replication, viruses manipulate the SUMOylation process to ensure viral persistence within the host ( Varadaraj et al, 2014 ; Wimmer and Schreiner, 2015 ; Loboda et al, 2019 ; El Motiam et al, 2020 ). Multiple depletion studies have implicated components of the SUMOylation pathway in viral survival, pathogenesis, and host immunity ( Chiu et al, 2007 ; Brown et al, 2016 ; Conn et al, 2016 ; Su et al, 2016 ; Guo et al, 2017 ; Feng et al, 2018 ; Zhu et al, 2019 ; Stokes et al, 2020 ).…”

“…A study of A. aegypti SUMO (AaSUMO) pathways showed poly-SUMO chains form more efficiently in the presence of an A. aegypti Protein Inhibitor of Activated STAT (AaPIAS). Depletion of AaSUMO, AaUbc9, or AaPIAS in A. aegypti cell lines resulted in a small but consistent significant increase in Zika virus (ZIKV) replication ( Stokes et al, 2020 ). However, the in vivo roles of protein SUMOylation in regulating viral replication in the mosquito A. aegypti are yet to be elucidated.…”

Transcriptional response of Wolbachia-transinfected Aedes aegypti mosquito cells to dengue virus at early stages of infection

“…A study in Aedes aegypti Aa20 and Aag2 cells showed that RNASEK knockdown resulted in reduced DENV replication providing further evidence of its unique role in virus infection [59]. Furthermore, three essential genes (SUMO-activating enzyme E1, SUMO-conjugating enzyme UBC9, and E3 SUMO-protein ligase) of the SUMOylation pathway, known to play a key role in the regulation of host anti-viral defence against arbovirus infection such as Zika virus (ZIKV), Semliki Forest virus, and Bunyamwera virus in mosquito cells, were significantly up-regulated at 6 hpi [60].…”