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The Ebola virus is a deadly pathogen that has been threatening public health for decades. Recent studies have revealed alternative viral invasion routes where Ebola virus approaches cells via interactions among phosphatidylserine (PS), PS binding ligands such as Gas6, and TAM family receptors such as Axl. In this study, we investigate the interactions among phosphatidylserine on the Ebola viral-like particle (VLP) membrane, human Gas6, and human Axl using atomic force microscope-based single molecule force spectroscopy to compare their binding strength and affinity from a biomechanical perspective. The impact of calcium ions on their interactions is also studied and quantified to provide more details on the calcium-dependent phosphatidylserine-Gas6 binding mechanism. Our results indicate that, in the presence of calcium ions, the binding strengths of VLP-Gas6 and VLP-Gas6-Axl increase but are still weaker than that of Gas6-Axl, and the binding affinity of VLP-Gas6 and VLP-Gas6-Axl is largely improved. The binding strength and affinity of Gas6-Axl basically remain the same, indicating no impact in the presence of calcium ions. Together, our study suggests that, under physiological conditions with calcium present, the Ebola virus can utilize its membrane phosphatidylserine to dock on cell surface via Gas6-Axl bound complex.
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Biomechanical characterization of TIM protein–mediated Ebola virus–host cell adhesion
Abstract Since the most recent outbreak, the Ebola virus (EBOV) epidemic remains one of the world’s public health and safety concerns. EBOV is a negative-sense RNA virus that can infect humans and non-human primates, and causes hemorrhagic fever. It has been proposed that the T-cell immunoglobulin and mucin domain (TIM) family proteins act as cell surface receptors for EBOV, and that the interaction between TIM and phosphatidylserine (PS) on the surface of EBOV mediates the EBOV–host cell attachment. Despite these initial findings, the biophysical properties of the TIM-EBOV interaction, such as the mechanical strength of the TIM-PS bond that allows the virus-cell interaction to resist external mechanical perturbations, have not yet been characterized. This study utilizes single-molecule force spectroscopy to quantify the specific interaction forces between TIM-1 or TIM-4 and the following binding partners: PS, EBOV virus-like particle, and EBOV glycoprotein/vesicular stomatitis virus pseudovirion. Depending on the loading rates, the unbinding forces between TIM and ligands ranged from 40 to 100 pN, suggesting that TIM-EBOV interactions are mechanically comparable to previously reported adhesion molecule–ligand interactions. The TIM-4–PS interaction is more resistant to mechanical force than the TIM-1–PS interaction. We have developed a simple model for virus–host cell interaction that is driven by its adhesion to cell surface receptors and resisted by membrane bending (or tension). Our model identifies critical dimensionless parameters representing the ratio of deformation and adhesion energies, showing how single-molecule adhesion measurements relate quantitatively to the mechanics of virus adhesion to the cell.
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- Award ID(s):
- 1804117
- PAR ID:
- 10153602
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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