Characterization of cytopathic factors through genome-wide analysis of the Zika viral proteins in fission yeast

Abstract

The Zika virus (ZIKV) causes microcephaly and the Guillain-Barré syndrome. Little is known about how ZIKV causes these conditions or which ZIKV viral protein(s) is responsible for the associated ZIKVinduced cytopathic effects, including cell hypertrophy, growth restriction, cell-cycle dysregulation, and cell death. We used fission yeast for the rapid, global functional analysis of the ZIKV genome. All 14 proteins or small peptides were produced under an inducible promoter, and we measured the intracellular localization and the specific effects on ZIKV-associated cytopathic activities of each protein. The subcellular localization of each ZIKV protein was in overall agreement with its predicted protein structure. Five structural and two nonstructural ZIKV proteins showed various levels of cytopathic effects. The expression of these ZIKV proteins restricted cell proliferation, induced hypertrophy, or triggered cellular oxidative stress leading to cell death. The expression of premembrane protein (prM) resulted in cell-cycle G1 accumulation, whereas membrane-anchored capsid (anaC), membrane protein (M), envelope protein (E), and nonstructural protein 4A (NS4A) caused cell-cycle G2/M accumulation. A mechanistic study revealed that NS4A-induced cellular hypertrophy and growth restriction were mediated specifically through the target of rapamycin (TOR) cellular stress pathway involving Tor1 and type 2A phosphatase activator Tip41. These findings should provide a reference for future research on the prevention and treatment of ZIKV diseases. T he recent Zika virus (ZIKV) outbreak was surprising in its rapidity and alarming in its association with microcephaly in newborns (1-3) and the Guillain-Barré syndrome in adults (4, 5). Currently, little is known about ZIKV pathogenicity. ZIKV infects various neuronal cells and affects brain neurogenesis by reducing cellular proliferation and inducing cell-cycle abnormalities, cell death/apoptosis, and autophagy (2, 3, 6-8). However, it is not known which viral determinant(s) cause these cytopathic effects. The objective of this study was to identify ZIKV factors responsible for the ZIKV-mediated cytopathic effects that underlie the diseases associated with ZIKV.

Guillain–Barré syndrome, transverse myelitis and infectious diseases

“…A mechanistic study revealed that NS4A-induced cellular hypertrophy and growth restriction were mediated specifically through the target of rapamycin (TOR) cellular stress pathway involving Tor1 and type 2A phosphatase activator Tip41. 191 Moreover, the appearance of neurologic syndromes associated with ZIKV could be related to the persistence of the virus, which can persist for a substantially long period, likely as a result of activation of mTOR, proinflammatory, and anti-apoptotic pathways that promote survival of infected cells, as well as exclusion of virusspecific antibodies from CSF. If persistent or occult neurologic and lymphoid disease similarly occurs following clearance of peripheral virus in ZIKV-infected humans, such a finding would have important clinical implications.…”

Zika Virus: What Have We Learnt Since the Start of the Recent Epidemic?

“…NS4A and NS4B deregulate Akt-mTOR signaling to inhibit neurogenesis and induce autophagy ( Liang et al, 2016 ). In addition, the expression of NS4A has been also related to activation of the cellular stress pathway involving Tor1 and type 2A phosphatase activator Tip41 ( Li G. et al, 2017 ). NS5 is the viral RNA-dependent RNA polymerase that is in charge of genome replication constituting a major target for antiviral design ( Lu et al, 2017 ; Xu et al, 2017 ).…”

Potential Therapeutics: Toe Hold in the Fight against Zika Virus

“…In a recent study using a fission yeast cell system, it has been shown that all ZIKV structural proteins, with the exception of Pr and two non-structural proteins (NS2B and NS4A), conferred cytopathic effects that included inhibition of growth/ proliferation, cell hypertrophy, cellcycle dysregulation, and cell death [60]. Genetic studies suggested that cellular hypertrophy and growth restriction were mediated through the Tor1 and Tip41 proteins of the TOR cellular stress-response pathway [60].…”

“…Genetic studies suggested that cellular hypertrophy and growth restriction were mediated through the Tor1 and Tip41 proteins of the TOR cellular stress-response pathway [60].…”