Binding Kinetics and Lateral Mobility of HSV-1 on End-Grafted Sulfated Glycosaminoglycans

Abstract

Many viruses, including herpes simplex (HSV), are recruited to their host cells via interaction between their envelope glycoproteins and cell-surface glycosaminoglycans (GAGs). This initial attachment is of a multivalent nature, i.e., it requires the establishment of multiple bonds between amino acids of viral glycoproteins and sulfated saccharides on the GAG chain. To gain understanding of how this binding process is modulated, we performed binding kinetics and mobility studies using end-grafted GAG chains that mimic the end attachment of these chains to proteoglycans. Total internal reflection fluorescence microscopy was used to probe binding and release, as well as the diffusion of single HSV-1 particles. To verify the hypothesis that the degree of sulfation, but also the arrangement of sulfate groups along the GAG chain, plays a key role in HSV binding, we tested two native GAGs (chondroitin sulfate and heparan sulfate) and compared our results to chemically sulfated hyaluronan. HSV-1 recognized all sulfated GAGs, but not the nonsulfated hyaluronan, indicating that binding is specific to the presence of sulfate groups. Furthermore we observed that a notable fraction of GAG-bound virions exhibit lateral mobility, although the multivalent binding to the immobilized GAG brushes ensures firm virus attachment to the interface. Diffusion was faster on the two native GAGs, one of which, chondroitin sulfate, was also characterized by the highest association rate per GAG chain. This highlights the complexity of multivalent virus-GAG interactions and suggests that the spatial arrangement of sulfates along native GAG chains may play a role in modulating the characteristics of the HSV-GAG interaction. Altogether, these results, obtained with a minimal and well-controlled model of the cell membrane, provide, to our knowledge, new insights into the dynamics of the HSV-GAG interaction.

Single Virion Tracking Microscopy for the Study of Virus Entry Processes in Live Cells and Biomimetic Platforms

“…In the in vitro environment of supported lipid bilayer platforms, virions diffusing along the bilayer follow a continuous trajectory, whereas those that bind, detach, and rebind elsewhere on the surface "appear" and "disappear" under TIRF microscopy. These modes of transport are easily distinguished from each other using this microscopy approach [79]. Supported lipid bilayers have an advantage over live cells for certain types of studies because of the ability to tightly control composition, receptor density and mobility, and surface geometry and heterogeneity.…”

Increasing the Affinity of an O‐Antigen Polysaccharide Binding Site in Shigella flexneri Bacteriophage Sf6 Tailspike Protein

“…Here, the typical bimodal O‐polysaccharide chain length distribution found in S. flexneri LPS results in a heterogeneous glycan ligand surface . A similar approach was chosen with eukaryotic viruses, where attachment studies were performed on glycosaminoglycan surfaces . Compared to dissociation constants obtained at single ligand binding sites in a solution set‐up, avidity effects occur upon multivalent protein binding to multivalent ligand surfaces.…”

Increasing the Affinity of an O-Antigen Polysaccharide Binding Site in Shigella Flexneri Bacteriophage Sf6 Tailspike Protein

“…[76] As imilar approachw as chosen with eukaryotic viruses, where attachment studies were performed on glycosaminoglycan surfaces. [77] Compared to dissociation constants obtained at single ligand bindings ites in as olution setup, avidity effects occur upon multivalent protein bindingt o multivalent ligand surfaces. This resultsi nn otable decrease of dissociation constants, more than two orders of magnitude have been reported in surface plasmon resonance set-ups.…”