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submitted on 26.06.2020 and posted on 29.06.2020by Darshita Budhadev, Emma Poole, Inga Nehlmeier, Yuanyuan Liu, James Hooper, Elizabeth Kalverda, Uchangi Satyaprasad Akshath, Nicole Hondow, W. Bruce Turnbull, Stefan Pöhlmann, Yuan Guo, Dejian Zhou
Multivalent lectin-glycan interactions are widespread
in biology and are often exploited by pathogens to bind and infect host cells.
Glycoconjugates can block such interactions and thereby prevent infection. The
inhibition potency strongly depends on matching the spatial arrangement between
the multivalent binding partners. However, the structural details of some key
lectins remain unknown and different lectins may exhibit overlapping glycan
specificity. This makes it difficult to design a glycoconjugate that can
potently and specifically target a particular multimeric lectin for therapeutic
interventions, especially under the challenging in vivo conditions. Conventional techniques such as surface plasmon
resonance (SPR) and isothermal titration calorimetry (ITC) can provide
quantitative binding thermodynamics and kinetics. However, they cannot reveal
key structural information, e.g.
lectin’s binding site orientation, binding mode, and inter-binding site
spacing, which are critical to design specific
multivalent inhibitors. Herein we report that gold nanoparticles (GNPs)
displaying a dense layer of simple glycans are powerful mechanistic probes for
multivalent lectin-glycan interactions. They can not only quantify the
GNP-glycan-lectin binding affinities via
a new fluorescence quenching method, but also reveal drastically different
affinity enhancing mechanisms between two closely-related tetrameric lectins,
DC-SIGN (simultaneous binding to one GNP) and DC-SIGNR (inter-crosslinking with
multiple GNPs), via a combined
hydrodynamic size and electron microscopy analysis. Moreover, a new term,
potential of assembly formation (PAF) has been proposed to successfully predict
the assembly outcomes based on the binding mode between GNP-glycans and lectins.
Finally, the GNP-glycans can potently and completely inhibit DC-SIGN-mediated
augmentation of Ebola virus glycoprotein-driven cell entry (with IC50
values down to 95 pM), but only partially block DC-SIGNR-mediated virus
infection. Our results suggest that the ability of a glycoconjugate to
simultaneously block all binding sites of a target lectin is key to robust
inhibition of viral infection.