Role of Host Filamin Proteins in Regulating Filovirus Entry and Egress

Filoviruses (Ebola [EBOV] and Marburg [MARV]) are zoonotic, emerging pathogens that cause sporadic and global outbreaks of severe hemorrhagic fever in humans and non-human primates. As EBOV and MARV can establish persistent infections in the CNS, semen, eye, and other immunologically privileged sites inaccessible to antibody therapy, and their re-emergence can result in long-term sequelae and death, understanding of host defense mechanisms that could lead to the development of new antiviral therapies is more critical than ever. Our lab is at the forefront of identifying host proteins that interact both physically and functionally with the filovirus VP40 matrix protein, the driving force for virus assembly and egress, to regulate these late stages of virus replication. To better understand the functional filovirus-host interactome, our laboratory has focused on direct interactions between the PPxY Late (L) domain motif conserved in the VP40 proteins of EBOV (eVP40) and MARV (mVP40) and modular WW-domains from select host proteins. In addition to positive regulators of filovirus egress, we have recently identified WW-domain interactors that negatively regulate VP40-mediated budding, including YAP/TAZ, BAG3, and WWOX. While the impact of these negative regulators is likely multifactorial and complex, we have made the intriguing observation that filamin B, a common downstream effector of YAP/TAZ and BAG3, acts as a potential dual regulator of live EBOV/MARV infectivity/entry and live EBOV/MARV egress. As dual role regulation of key stages at opposite ends of the filovirus lifecycle is novel and unexpected, the ultimate goal of this proposal is to determine how host protein filamin B mechanistically impacts the filovirus lifecycle. Filamins are a family of actin crosslinking/stabilizing proteins that regulate actin dynamics at the plasma membrane to control cell migration and morphology, vesicle trafficking, macropinocytosis, and cell division. Notably, macropinocytosis macropinosomes is (MPs) that are densely coated with actin, filamin, and filamin-associated proteins a key entry pathway for filoviruses, as these viruses enter the cell in vesicles termed . In addition, filamins are linked to cellular processes that mimic virion formation and/or egress such as filopodia formation, cell migration, and cytokinesis. Thus, we hypothesize that filamin B regulates infectivity/entry of filoviruses through effects on macropinocytosis, and regulates filovirus budding through effects on egress of filopodia-like filovirus particles. In this exploratory proposal, we propose to investigate the mechanisms by which filamin regulates filovirus infectivity/entry (Aim 1) and egress (Aim 2). Results from these studies will impact the field by identifying a novel host protein(s) whose expression modulates two critical and opposite steps in the filovirus lifecycle; entry and exit, as well as providing a better fundamental understanding of the functional filovirus-host interactome and host defense mechanisms that could lead to the development of new antiviral therapies.