Membrane binding and bending in Ebola VP40 assembly and egress.

Robert V Stahelin

doi:10.3389/fmicb.2014.00300

Abstract

Lipid-enveloped viruses contain a lipid bilayer coat that protects their genome and helps to facilitate entry into the host cell. Filoviruses are lipid-enveloped viruses that have up to 90% clinical fatality and include Marbug (MARV) and Ebola (EBOV). These pleomorphic filamentous viruses enter the host cell through their membrane-embedded glycoprotein and then replicate using just seven genes encoded in their negative-sense RNA genome. EBOV budding occurs from the inner leaflet of the plasma membrane (PM) and is driven by the matrix protein VP40, which is the most abundantly expressed protein of the virus. VP40 expressed in mammalian cells alone can trigger budding of filamentous virus-like particles (VLPs) that are nearly indistinguishable from authentic EBOV. VP40, such as matrix proteins from other viruses, has been shown to bind anionic lipid membranes. However, how VP40 selectively interacts with the inner leaflet of the PM and assembles into a filamentous lipid enveloped particle is mostly unknown. This article describes what is known regarding VP40 membrane interactions and what answers will fill the gaps.

Highlights

The discovery of filoviruses, Marburg virus (MARV) and Ebola virus (EBOV) in 1967 and 1976, respectively, spread fear of new pandemics that could spread globally and kill millions of people (Dowdle, 1976; Johnson et al, 1977)
VP40 consists of 326 amino acids and has been shown to be a peripheral protein (Jasenosky et al, 2001), which localizes to the inner leaflet of the plasma membrane (PM) of human cells
VP40 MEMBRANE BINDING MODEL VP40 may be somewhat similar to the VSV matrix protein, which has been shown to engage in both electrostatic and hydrophobic interactions with lipid membranes (Ye et al, 1994; Gaudier et al, 2002)

Summary

INTRODUCTION

The discovery of filoviruses, Marburg virus (MARV) and Ebola virus (EBOV) in 1967 and 1976, respectively, spread fear of new pandemics that could spread globally and kill millions of people (Dowdle, 1976; Johnson et al, 1977). VP40 C-TERMINAL DOMAIN HYDROPHOBIC INTERACTIONS ARE IMPORTANT FOR VLP FORMATION In 2001, it was shown that VP40 alone formed VLPs from cells (Jasenosky et al, 2001) These studies investigated VP40 and respective truncation constructs’ ability to associate with cellular membranes. VP40 was found to be a peripheral protein as it was almost exclusively extracted in the aqueous phase These authors propose the important role of hydrophobic interactions of VP40 in membrane binding as they find 1 M NaCl did not release VP40 from the membrane bilayer. Octamer formation has been shown to occur in some mutations of the C-terminal domain, resulting in perinuclear globules (Bornholdt et al, 2013) This 18-residue truncation was shown to be oligomeric, associated with the detergent soluble fraction, and was unable to make VLPs (Panchal et al, 2003). 221-229 K224E/K225E K224M/K225M K224R/K225R M241R K274A/275A K274R/275R P283L/P286L

Reduced penetration into PM mimetic

Findings

CONCLUSION AND FUTURE PERSPECTIVES