Role of Host Angiomotin as a Central Regulator of Filovirus Egress and Dissemination

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Filoviruses (Ebola [EBOV] and Marburg [MARV]) and arenaviruses (e.g. Lassa virus; LAFV) are zoonotic, emerging pathogens that cause outbreaks of severe hemorrhagic fever in humans and non-human primates. A fundamental understanding of the virus-host interface is critical for developing future strategies and countermeasures for therapeutic intervention. As the filovirus VP40 and LAFV Z matrix proteins drive virion assembly and egress, in part, by hijacking specific host proteins containing WW-domains that can interact with their highly conserved PPxY L-domain motifs, these interactions represent a novel therapeutic target to inhibit egress and dissemination of these hemorrhagic fever viruses. Our early studies to identify host WW-domain proteins that regulate filovirus and arenavirus budding identified the E3 ubiquitin ligases Nedd4, ITCH, and WWP1 as positive regulators of viral PPxY-mediated budding. However, in more recent studies, we identified WW-domain containing proteins YAP/TAZ, BAG3, and now WWOX (WW Domain Containing Oxidoreductase; a multi-functional tumor suppressor), as negative regulators of PPxY-mediated egress of VP40 and Z VLPs. The identification of YAP/TAZ, BAG3, and WWOX as negative regulators of viral PPxY-mediated budding is particularly intriguing since all three of these proteins interact with Angiomotin (Amot), a multi-PPxY containing protein that functions as a “master regulator” of Hippo pathway (YAP/TAZ) signaling, cytoskeletal dynamics, cell migration/proliferation, and tight junction (TJ) integrity. Moreover, expression and stability of Amot itself are regulated by PPxY/WW-domain interactions with the Nedd4 family of E3 ubiquitin ligases. Thus, we hypothesize that Amot is a central interactor linking both the positive and negative WW-domain containing regulators of virus egress, and that modular mimicry between viral and host PPxY motifs and the competitive nature of their binding to the same host WW-domain containing proteins will have a major impact on both cellular processes and viral replication and pathogenesis. Indeed, we were first to report that expression of endogenous Amot positively regulates PPxY-mediated egress of EBOV and MARV VP40 VLPs as well as egress and spread of live EBOV and MARV in cell culture. In this proposal, we will build upon our novel finding that PPxY-containing Amot can positively regulate egress and spread of PPxY-containing viruses including EBOV and MARV, and determine whether the competitive PPxY/WW-domain interplay among VP40/Z – Amot – host WW-domain interactors regulates egress of VLPs and live viruses in vitro and in vivo. Successful completion of these aims will provide novel insights into how this complex network of modular PPxY/WW-domain interactions with Amot impacts late stages of hemorrhagic fever virus egress and dissemination and serve as proof-of principle for therapeutic strategies targeting an essential viral-host interaction that may represent an Achilles heel for numerous RNA viruses.