Relevance of Ebola virus VP35 homo-dimerization on the type I interferon cascade inhibition

Abstract

Ebola virus high lethality relies on its ability to efficiently bypass the host innate antiviral response, which senses the viral dsRNA through the RIG-I receptor and induces type I interferon a/b production. In the bypassing action, the Ebola virus protein VP35 plays a pivotal role at multiple levels of the RIG-I cascade, masking the viral 5 0-triphosphorylated dsRNA from RIG-I, and interacting with other cascade components. The VP35 type I interferon inhibition is exerted by the C-terminal domain, while the N-terminal domain, containing a coiled-coil region, is primarily required for oligomerization. However, mutations at key VP35 residues L90/93/107A (VP35-3m) in the coiled-coil region were reported to affect oligomerization and reduce type I interferon antagonism, indicating a possible but unclear role of homo-oligomerization on VP35 interaction with the RIG-I pathway components. In this work, we investigated the VP35 dimerization thermodynamics and its contribution to type I interferon antagonism by computational and biological methods. Focusing on the coiled-coil region, we combined coarse-grained and all-atom simulations on wild type VP35 and VP35-3m homo-dimerization. According to our results, wild type VP35 coiled-coil is able to self-assemble into dimers, while VP35-3m coiled-coil shows poor propensity to even dimerize. Free-energy calculations confirmed the key role of L90, L93 and L107 in stabilizing the coiled-coil homo-dimeric structure. In vitro type I interferon antagonism studies, using full-length wild type VP35 and VP35-3m, revealed that VP35 homo-dimerization is an essential preliminary step for dsRNA binding, which appears to be the main factor of the VP35 RIG-I cascade inhibition, while it is not essential to block the other steps.

Quercetin Blocks Ebola Virus Infection by Counteracting the VP24 Interferon-Inhibitory Function

“…Since EBOV inhibition of the IFN response massively contributes to viral pathogenesis (4, 5), restoring the IFN system could represent a promising strategy for EBOV control (13). Two viral proteins have been demonstrated to suppress interferon responses, VP35 and VP24 (13,39). Different studies have shown that it is possible to block VP35 IFN-inhibitory function with natural compounds (11,12) and also antibodies ( 14), thus restoring the IFN production cascade.…”

The SARS-Coronavirus Infection Cycle: A Survey of Viral Membrane Proteins, Their Functional Interactions and Pathogenesis

“…Liu et al also found that the N-terminal hydrophobic TMS, but not the C-terminal hydrophilic region of M, was important for the response, confirming the results of Siu et al [ 312 ]. The M-mediated interferon antagonism noted here seems to be a common characteristic of a large number of (but definitely not all) viruses from different viral classifications [ 314 , 315 ].…”

Viral pathogen-induced mechanisms to antagonize mammalian interferon (IFN) signaling pathway

“…Many viruses also encode proteins that help conceal their genetic material from PRR. Some viruses possess dsRNA binding proteins that could potentially sequester these PAMPs from PPR recognition, such as VP35 from Ebola virus or σ3 from reovirus [ 73 , 74 ]. The encapsidation of the viral RNA can also impair RLR recognition.…”