DC-SIGN-MFN · Dissecting Multivalent Viral Receptor-carbohydrate Interactions Using Polyvalent Multifunctional Glycan-Quantum Dot

Dissecting Multivalent Viral Receptor-carbohydrate Interactions Using Polyvalent Multifunctional Glycan-Quantum Dot

Multivalent lectin-glycan interactions (MLGIs) play a key role in facilitating viral infections, affecting hundreds of millions people worldwide. Understanding the underlying structural mechanisms is key to be able to design glycoconjugates that can potently and specifically block such interactions, thereby preventing infection. Compared to other anti-viral strategies, developing glycoconjugates to block virus entry to host is advantageous: it can prevent virus mutating and developing resistance. This is especially important for unstable RNA viruses, e.g. SARS COV-2 responsible for the Covid-19 pandemic, whose rapid mutation can severely hamper the effectiveness most anti-viral strategies. However, research advances have been hampered by inability of current methods to reveal key structural information (e.g. binding site orientation, distance, & binding mode) of some key cell membrane lectins. This is important because, (1) glycoconjugates's antiviral potency depends on critically the ability to match the spatial arrangements of MLGI partners; (2) many lectins have overlapping glycan specificity, this can prevent glycoconjugates from blocking other MGLIs non-specifically to induce severer side effects. For example, despite 20 years of research, the detailed structures of two closely related and vitally important tetrameric lectins, DC-SIGN and DC-SIGNR, remain unknown. They can bind to virus surface glycans to enhance the infections of many viruses (e.g. HIV, HCV and Ebola). Unfortunately, conventional biophysical techniques, e.g. SPR and ITC, although powerful in providing quantitative binding thermodynamics and kinetics, they cannot provide structural information. This fellowship aims to develop a novel multimodal readout strategy (combining FRET, TEM and particle size analysis) using compact glycan-quantum dots (QDs) by exploiting multivalency and QD’s strong fluorescence and high contrast in TEM imaging. By tuning glycan structure, valency, inter-glycan spacing, it aims to create a perfect spatial & orientation match to those of glycan-binding-domains (CRDs) in DC-SIGN/R, leading to greatly enhanced binding affinity. By studying QD-glycans and their assemblies binding with DC-SIGN/R, we will reveal key structural data (e.g. CRD orientation, distance, binding mode) in DC-SIGN/R. It also aims to verify the binding data with native receptors on cell surfaces, correlate receptor binding affinity with virus inhibition potency, and study their immune cell activation.

Data: CORDIS, © European Union