Ebola Virus Glycoproteins Induce Global Surface Protein Down-Modulation and Loss of Cell Adherence

Abstract

The Ebola virus envelope glycoprotein (GP) derived from the pathogenic Zaire subtype mediates cell rounding and detachment from the extracellular matrix in 293T cells. In this study we provide evidence that GPs from the other pathogenic subtypes, Sudan and Côte d'Ivoire, as well as from Reston, a strain thought to be nonpathogenic in humans, also induced cell rounding, albeit at lower levels than Zaire GP. Sequential removal of regions of potential O-linked glycosylation at the C terminus of GP1 led to a step-wise reduction in cell detachment without obviously affecting GP function, suggesting that such modifications are involved in inducing the detachment phenotype. While causing cell rounding and detachment in 293T cells, Ebola virus GP did not cause an increase in cell death. Indeed, following transient expression of GP, cells were able to readhere and continue to divide. Also, the rounding effect was not limited to 293T cells. Replication-deficient adenovirus vectors expressing Ebola virus GP induced the loss of cell adhesion in a range of cell lines and primary cell types, including those with proposed relevance to Ebola virus infection in vivo, such as endothelial cells and macrophages. In both transfected 293T and adenovirus-infected Vero cells, a reduction in cell surface expression of adhesion molecules such as integrin ␤1 concurrent with the loss of cell adhesion was observed. A number of other cell surface molecules, however, including major histocompatibility complex class I and the epidermal growth factor receptor, were also down-modulated, suggesting a global mechanism for surface molecule down-regulation.

Tetherin-mediated restriction of filovirus budding is antagonized by the Ebola glycoprotein

“…We next sought to determine the contribution of the highly glycosylated mucin domain to the antitetherin activity of Ebola GP. The mucin domain within GP is known to contribute to cellular pathogenesis by affecting surface levels of a variety of cellular proteins (14,15). It appears that this region of GP, however, is not required to counteract tetherin because deletion of the mucin domain had no effect upon the ability of GP to promote virion release from tetherin-expressing cells (Fig.…”

“…An extremely divergent mucin-like region is localized to the C-terminal region of GP1. Several groups have previously shown that the GP mucin domain causes downmodulation of cell surface proteins (14,15). Therefore, we initially hypothesized that the mucin domain within Ebola GP would prove critical in interfering with tetherin activity.…”

Inhibition of Ebola virus glycoprotein-mediated cytotoxicity by targeting its transmembrane domain and cholesterol

“…In addition, the interaction between b1-integrin and GP was shown to contribute to the loss of adhesion of GP-expressing cells 7,24 . Furthermore, a role for the GP 2 subunit in counteracting interferon-induced antiviral response via the protein tetherin (BST-2) has been proposed 25 .…”

“…The dysregulation of the immune response and a heavy inflammatory reaction, described as a 'cytokine storm', are induced on EBOV infection 5 . Whether the detachment of infected endothelial cells and the concomitant leakage of the endothelial barrier are important factors in the pathogenesis of Ebola virus disease remains controversial [6][7][8][9][10][11] . Among other factors, the cytotoxicity of EBOV has been attributed to the envelope glycoprotein (GP) 6 ; however, the molecular mechanism underlying the pathogenicity of this virus is unclear.…”

Lentivirus-mediated gene transfer to the respiratory epithelium: a promising approach to gene therapy of cystic fibrosis

“…Both may create a concern with respect to biosafety. The first strategy relies on viral glycoproteins, which may be toxic in vivo 99,100 and thus the next necessary step will be to mutate them in order for the system to be safer. 56 The second strategy may be not compatible with the CF environment and be more deleterious than expected.…”