Biology subjects

Duncan, A. M.

Publications and source records attributed to Duncan, A. M..

2 recordsLinked to original sources

bioRxiv2022

Phosphatidylserine within the Viral Membrane Enhances Chikungunya Virus Infectivity in a Cell-type Dependent Manner

Chikungunya virus (CHIKV), an alphavirus of the Togaviridae family, is the causative agent of the human disease chikungunya fever (CHIKF), which is characterized by debilitating acute and chronic arthralgia. No licensed vaccines or antivirals exist for CHIKV. Preventing the attachment of viral particles to host cells is an attractive intervention strategy. Viral entry of enveloped viruses from diverse families including Filoviridae and Flaviviridae is mediated or enhanced by phosphatidylserine receptors (PSRs). PSRs facilitate the attachment of enveloped viruses to cells by binding to exposed phosphatidylserine (PS) in the viral lipid membrane - a process termed viral apoptotic mimicry. To investigate the role of viral apoptotic mimicry during CHIKV infection, we produced viral particles with discrete amounts of exposed PS on the virion envelope by exploiting the cellular distribution of phospholipids at the plasma membrane. We found that CHIKV particles containing high outer leaflet PS (produced in cells lacking flippase activity) were more infectious in Vero cells than particles containing low levels of outer leaflet PS (produced in cells lacking scramblase activity). However, the same viral particles were similarly infectious in NIH3T3 and HAP1 cells, suggesting PS levels can influence infectivity only in cells with high levels of PSRs. Interestingly, PS-dependent CHIKV entry was observed in mosquito Aag2 cells, but not C6/36 cells. These data demonstrate that CHIKV entry via viral apoptotic mimicry is cell-type dependent. Furthermore, viral apoptotic mimicry has a mechanistic basis to influence viral dynamics in vivo in both the human and mosquito host. ImportanceOutbreaks of Chikungunya virus (CHIKV) have occurred throughout Africa, Asia, and Europe. Climate change permits the expansion of Aedes mosquito vectors into more temperate regions, broadening the geographic range and increasing the frequency of future human outbreaks. The molecular basis underlying the broad host and cellular tropism of CHIKV remains unresolved. While several host molecules have been implicated in CHIKV viral attachment and entry, the role of lipid-mediated attachment (viral apoptotic mimicry) is unclear. We observed that higher levels of externalized phosphatidylserine (PS) in the viral lipid bilayer correlated with enhanced CHIKV infectivity in mammalian cells abundant with PS receptors and lacking alternative attachment factors. Interestingly, CHIKV infection in mosquito Aag2 cells was also affected by viral PS accessibility. This study further delineates the role of virus-cell attachment molecules in CHIKV infection. Viral apoptotic mimicry has potential to influence CHIKV dynamics in vivo in both the human and mosquito host.

microbiology↗

bioRxiv2020

Ebola virus requires phosphatidylserine scrambling activity for efficient budding and optimal infectivity

AbstractEbola virus (EBOV) interacts with cells using two categories of cell surface receptors, C-type lectins and phosphatidylserine (PS) receptors. PS receptors typically bind to apoptotic cell membrane PS and orchestrate the uptake and clearance of apoptotic bodies. Many viruses coated with PS-containing lipid envelopes, acquired during budding from host cells, can also exploit these receptors for internalization. PS is restricted to the inner leaflet of the plasma membrane in homeostatic cells, an orientation that would be unfavorable for PS receptor-mediated uptake if conserved on the viral envelope. Therefore, it is theorized that viral infection induces host cell PS externalization to the outer leaflet during replication. Cells have several membrane scramblase enzymes that enrich outer leaflet PS when activated. Here, we investigate two scramblases, TMEM16F and XKR8, as possible mediators of cellular and viral envelope surface PS levels during recombinant VSV/EBOV-GP replication and EBOV virus-like particle (VLP) production. We found that rVSV/EBOV-GP and EBOV VLPs produced in XKR8 knockout cells contain decreased levels of PS in their outer leaflets. {Delta}XKR8-made rVSV/EBOV-GP is 70% less efficient at infecting cells through apoptotic mimicry compared to viruses made in parental cells. Our data suggest that virion surface PS acquisition requires XKR8 activity, whereas TMEM16F activity is not essential. Unexpectedly, we observed defective rVSV/G, rVSV/EBOV-GP, and EBOV VLP budding in {Delta}XKR8 cells, suggesting that phospholipid scrambling via XKR8 enhances both Ebola infectivity and budding efficiency. Overexpression of XKR8 dramatically increased budding activity, suggesting outer leaflet PS is required for both particle production and increased infectivity. ImportanceThe Democratic Republic of the Congo experienced its deadliest Ebola outbreak from 2018 to 2020, with 3,444 confirmed cases and 2,264 deaths (as of March 12, 2020). Owing to the extensive damage that these outbreaks have caused in Africa, as well as its future epidemic potential, Ebola virus (EBOV) ranks among the top eight priority pathogens outlined by the WHO in 2018. A comprehensive understanding of Ebola entry pathways into target cells is critical for antiviral development and outbreak control. Thus far, host-cell scramblases TMEM16F and XKR8 have each been named as the sole mediator of Ebola envelope surface phosphatidylserine (PS). We assessed the contributions of these proteins using CRISPR knockout cells and two EBOV models: rVSV/EBOV-GP and EBOV VLPs. We observed that XKR8 is required for optimal EBOV envelope PS levels, PS receptor engagement, and particle budding across all viral models, whereas TMEM16F did not play a major role.

microbiology↗