Ebola virus (EBOV) infection of humans often results in severe hemorrhagic fever which is lethal in up to 90% of infected cases. Therefore, understanding the molecular mechanisms of Ebola virus pathogenesis is essential for development of successful therapeutics. Previous work has demonstrated that EBOV VP24 prevents type I and II Interferon (IFN) signaling by binding to the specific members of the karyopherin a (KPNA) family of nuclear import proteins to prevent nuclear accumulation of STAT-1. The ability of VP24 to block IFN signaling is one example of how EBOV can suppress the host response to infection. The goal of this proposal is to test if VP24 binding to KPNAs prevents binding and subsequent nuclear translocation of additional cellular proteins. We hypothesize VP24 blocks the nuclear import of additional cellular proteins and redistributes these proteins to the cytoplasm to promote EBOV replication. To this end, we have demonstrated that the heterogeneous ribonuclear protein C1/C2 complex (hnRNP C1/C2) interacts with members of the KPNA family, and that hnRNP C1/C2 binding to KPNA1 is diminished in the presence of VP24. VP24 inhibition of hnRNP C1/C2 binding to KPNA1 is of great interest since hnRNP CI/ C2 has been shown to play an important role in the replication cycle of other RNA viruses. Therefore, the first aim of this proposal is to fully characterize the interactions between VP24, the NPI-I KPNA family members and hnRNP C1/C2 and determine if VP24/KPNA interactions are sufficient to prevent hnRNP CI/ C2 nuclear accumulation. Since hnRNP C1/C2 facilitates both viral RNA and protein synthesis in other systems, the second aim will test if hnRNP C1/C2 interacts with EBOV RNA and impacts viral replication and/or protein translation.
The third aim of this proposal focuses on developing assays to screen for small molecule inhibitors against VP24 IFN antagonism. Identifying small molecular inhibitors that impair EBOV mediated IFN antagonism (and likely replication) would be very useful for treating EBOV.
EBOV is an extremely lethal microbe and while infection is rare, it is possible that additional outbreaks either from a natural or unnatural source could occur.
The aims presented in this proposal further define how EBOV VP24 modulates the normal cellular nuclear import and identify small compounds to inhibit VP24 function! Data obtained from these studies could strengthen the fields'understanding of the molecular mechanism of EBOV pathogenesis as well as identify effective drugs to inhibit EBOV replication.
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