Mechanism of glycoform specificity and in vivo protection by an anti-afucosylated IgG nanobody
Year: 2023
Type: article
Abstract: Immunoglobulin G (IgG) antibodies contain a single, complex N -glycan on each IgG heavy chain protomer embedded in the hydrophobic pocket between its Cγ2 domains. The presence of this glycan contributes to the structural organization of the Fc domain and determines its specificity for Fcγ receptors, thereby determining distinct cellular responses. On the Fc, the variable construction of this glycan structure leads to a family of highly-related, but non-equivalent glycoproteins known as glycoforms. We previously reported the development of synthetic nanobodies that distinguish IgG glycoforms without cross-reactivity to off-target glycoproteins or free glycans. Here, we present the X-ray crystal structure of one such nanobody, X0, in complex with its specific binding partner, the Fc fragment of afucosylated IgG1. Two X0 nanobodies bind a single afucosylated Fc homodimer at the upper Cγ2 domain, making both protein-protein and protein-carbohydrate contacts and overlapping the binding site for Fcγ receptors. Upon binding, the elongated CDR3 loop of X0 undergoes a conformational shift to access the buried N -glycan and acts as a ‘glycan sensor’, forming hydrogen bonds with the afucosylated IgG N -glycan that would otherwise be sterically hindered by the presence of a core fucose residue. Based on this structure, we designed X0 fusion constructs that disrupt pathogenic afucosylated IgG1-FcγRIIIa interactions and rescue mice in a model of dengue virus infection.
Source: Nature Communications
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $6,290
Funders: U.S. Department of Energy, U.S. Department of Health and Human Services, Bill and Melinda Gates Foundation, National Institutes of Health, Office of Science, Weill Cornell Medical College, National Cancer Institute, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases, National Center for Research Resources, Biological and Environmental Research, Brookhaven National Laboratory
Awards: Targeting EndoS to auto-antibodies, G1285306620, G1867732070, G1868695577, G241279073, Crystallization Robot for the Structural Biology Resource Center at Rockefeller, G3002096968, G3262563802, G3376477779, G3388457521, G357145406, G3850097093, G4735757437, G4972998915, G5417557083, G5633341255, G5765906131, G6476969910, G6733788163, Rockefeller University - to develop a COVID-19 assay for disease severity, G7463374569, Integrating innate and adaptive pathways in vaccine responses, G8461821187, G8527777847, G8775485830, Weill Cornell/Rockefeller/Sloan Kettering MST Program, Cancer Center Support Grant, Center for Biomolecular Structure (CBMS), Engineering IgG-specific endoglycosidases to selectively defeat effector functions
OpenAlex ID: W4377047280