Host Protein BAG3 is a Negative Regulator of Lassa VLP Egress.

Ziying Han,Corbett Berry,Marius Sudol,Philip Hicks,Michael Schwoerer,Ronald Harty,Bruce Freedman,Gordon Ruthel,Mark Bedford,Cari Sagum,Sachdev Sidhu,Jingjing Liang

doi:10.3390/diseases6030064

Abstract

Lassa fever virus (LFV) belongs to the Arenaviridae family and can cause acute hemorrhagic fever in humans. The LFV Z protein plays a central role in virion assembly and egress, such that independent expression of LFV Z leads to the production of virus-like particles (VLPs) that mimic egress of infectious virus. LFV Z contains both PTAP and PPPY L-domain motifs that are known to recruit host proteins that are important for mediating efficient virus egress and spread. The viral PPPY motif is known to interact with specific host WW-domain bearing proteins. Here we identified host WW-domain bearing protein BCL2 Associated Athanogene 3 (BAG3) as a LFV Z PPPY interactor using our proline-rich reading array of WW-domain containing mammalian proteins. BAG3 is a stress-induced molecular co-chaperone that functions to regulate cellular protein homeostasis and cell survival via Chaperone-Assisted Selective Autophagy (CASA). Similar to our previously published findings for the VP40 proteins of Ebola and Marburg viruses, our results using VLP budding assays, BAG3 knockout cells, and confocal microscopy indicate that BAG3 is a WW-domain interactor that negatively regulates egress of LFV Z VLPs, rather than promoting VLP release. Our results suggest that CASA and specifically BAG3 may represent a novel host defense mechanism, whereby BAG3 may dampen egress of several hemorrhagic fever viruses by interacting and interfering with the budding function of viral PPxY-containing matrix proteins.

Highlights

Viral hemorrhagic fever (VHF) is a severe syndrome that can be caused by a number of emergingRNA viruses including arenaviruses such as Lassa and filoviruses such as Ebola [1]
We found that in the presence of BCL2 Associated Athanogene 3 (BAG3)-WT, VP40 colocalized with microtubule-associated light chain 3 (LC3), a well-known marker for aggresomes [19]
plasma membrane (PM) projections cells co-expressing (Figure 5, bottom row, white boxes). These results suggest that BAG3-WT, but not BAG3-ΔN, is playing a role in dampening the release of Lassa fever virus (LFV)-Z virus-like particles (VLPs) perhaps at the site of budding at the PM, and these findings correlate well with results from our VLP budding assays

Summary

Introduction

RNA viruses including arenaviruses such as Lassa and filoviruses such as Ebola [1]. Both Lassa and Ebola viruses are zoonotic pathogens with the ability to cause severe VHF disease in humans with high case fatality rates [1]. Diseases 2018, 6, 64 mechanisms of these diseases, including a better understanding of the specific interactions between the virus and the host that may contribute to the disease process. Both Lassa and Ebola encode matrix proteins that play key roles in virion assembly and egress from infected cells.

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Results

Conclusion