Download MendeleyFc gamma RI FG-loop functions as a pH sensitive switch for IgG binding and release.
Lu, J., Spencer, M., Zou, Z., Traver, M., Brzostowski, J., Sun, P.D.(2023) Front Immunol 14: 1100499-1100499
- PubMed: 36814926
- DOI: https://doi.org/10.3389/fimmu.2023.1100499
- Primary Citation of Related Structures:
8DIN, 8DIR, 8DJ7 - PubMed Abstract:
Understanding the molecular mechanism underlying the hierarchic binding between FcγRs and IgG antibodies is critical for therapeutic antibody engineering and FcγR functions. The recent determination of crystal structures of FcγRI-Fc complexes, however, resulted in two controversial mechanisms for the high affinity receptor binding to IgG. Here, we describe high resolution structures of a bovine FG-loop variant of FcγRI in complex with the Fc fragment of IgG 1 crystallized in three different conditions at neutral pH, confirming the characteristic FG loop-Fc interaction is critical to the high affinity immunoglobulin binding. We showed that the FcγRI D2-domain FG-loop functioned as a pH-sensing switch for IgG binding. Further live cell imaging of FcγRI-mediated internalization of immune complexes showed a pH sensitive temporal-spatial antibody-antigen uptake and release. Taken together, we demonstrate that the structures of FcγRI-Fc crystallized at neutral and acidic pH, respectively, represent the high and low affinity binding states of the receptor for IgG uptake and release. These results support a role for FcγRI in antigen delivery, highlight the importance of Fc glycan in antibody binding to the high affinity receptor and provide new insights to future antibody engineering.
Organizational Affiliation:
Structural Immunology Section, Lab of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, United States.
