Chaperone-Mediated Autophagy Protein BAG3 Negatively Regulates Ebola and Marburg VP40-Mediated Egress

PLoS Pathog. 2017 Jan 11;13(1):e1006132. doi: 10.1371/journal.ppat.1006132. eCollection 2017 Jan.


Ebola (EBOV) and Marburg (MARV) viruses are members of the Filoviridae family which cause outbreaks of hemorrhagic fever. The filovirus VP40 matrix protein is essential for virus assembly and budding, and its PPxY L-domain motif interacts with WW-domains of specific host proteins, such as Nedd4 and ITCH, to facilitate the late stage of virus-cell separation. To identify additional WW-domain-bearing host proteins that interact with VP40, we used an EBOV PPxY-containing peptide to screen an array of 115 mammalian WW-domain-bearing proteins. Using this unbiased approach, we identified BCL2 Associated Athanogene 3 (BAG3), a member of the BAG family of molecular chaperone proteins, as a specific VP40 PPxY interactor. Here, we demonstrate that the WW-domain of BAG3 interacts with the PPxY motif of both EBOV and MARV VP40 and, unexpectedly, inhibits budding of both eVP40 and mVP40 virus-like particles (VLPs), as well as infectious VSV-EBOV recombinants. BAG3 is a stress induced protein that regulates cellular protein homeostasis and cell survival through chaperone-mediated autophagy (CMA). Interestingly, our results show that BAG3 alters the intracellular localization of VP40 by sequestering VP40 away from the plasma membrane. As BAG3 is the first WW-domain interactor identified that negatively regulates budding of VP40 VLPs and infectious virus, we propose that the chaperone-mediated autophagy function of BAG3 represents a specific host defense strategy to counteract the function of VP40 in promoting efficient egress and spread of virus particles.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Animals
  • Apoptosis Regulatory Proteins / genetics*
  • Autophagy / genetics
  • Autophagy / physiology*
  • Cell Line, Tumor
  • Cell Survival / genetics
  • Cricetinae
  • Ebolavirus / genetics
  • Ebolavirus / metabolism*
  • Endosomal Sorting Complexes Required for Transport
  • HEK293 Cells
  • HeLa Cells
  • Hemorrhagic Fever, Ebola / pathology
  • Hemorrhagic Fever, Ebola / transmission*
  • Hemorrhagic Fever, Ebola / virology
  • Humans
  • Marburg Virus Disease / pathology
  • Marburg Virus Disease / transmission*
  • Marburg Virus Disease / virology
  • Marburgvirus / genetics
  • Marburgvirus / metabolism*
  • Nedd4 Ubiquitin Protein Ligases
  • Proline / analogs & derivatives
  • Proline / metabolism
  • Protein Structure, Tertiary
  • Protein Transport / physiology
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Repressor Proteins / metabolism
  • Ubiquitin-Protein Ligases / metabolism
  • Viral Matrix Proteins / metabolism*
  • Virus Release / genetics*


  • Adaptor Proteins, Signal Transducing
  • Apoptosis Regulatory Proteins
  • BAG3 protein, human
  • Endosomal Sorting Complexes Required for Transport
  • PPXY ligand
  • RNA, Small Interfering
  • Repressor Proteins
  • VP40 protein, virus
  • Viral Matrix Proteins
  • Proline
  • ITCH protein, human
  • Nedd4 Ubiquitin Protein Ligases
  • Nedd4 protein, human
  • Ubiquitin-Protein Ligases