8so3
From Proteopedia
CryoEM structure of a therapeutic antibody (favezelimab) bound to human LAG3
Structural highlights
FunctionLAG3_HUMAN Lymphocyte activation gene 3 protein: Inhibitory receptor on antigen activated T-cells (PubMed:7805750, PubMed:8647185, PubMed:20421648). Delivers inhibitory signals upon binding to ligands, such as FGL1 (By similarity). FGL1 constitutes a major ligand of LAG3 and is responsible for LAG3 T-cell inhibitory function (By similarity). Following TCR engagement, LAG3 associates with CD3-TCR in the immunological synapse and directly inhibits T-cell activation (By similarity). May inhibit antigen-specific T-cell activation in synergy with PDCD1/PD-1, possibly by acting as a coreceptor for PDCD1/PD-1 (By similarity). Negatively regulates the proliferation, activation, effector function and homeostasis of both CD8(+) and CD4(+) T-cells (PubMed:7805750, PubMed:8647185, PubMed:20421648). Also mediates immune tolerance: constitutively expressed on a subset of regulatory T-cells (Tregs) and contributes to their suppressive function (By similarity). Also acts as a negative regulator of plasmacytoid dendritic cell (pDCs) activation (By similarity). Binds MHC class II (MHC-II); the precise role of MHC-II-binding is however unclear (PubMed:8647185).[UniProtKB:Q61790][1] [2] [3] May function as a ligand for MHC class II (MHC-II) on antigen-presenting cells (APC), promoting APC activation/maturation and driving Th1 immune response.[UniProtKB:Q61790] Publication Abstract from PubMedLymphocyte activation gene 3 protein (LAG3) is an inhibitory receptor that is upregulated on exhausted T cells in tumors. LAG3 is a major target for cancer immunotherapy with many anti-LAG3 antibodies in clinical trials. However, there is no structural information on the epitopes recognized by these antibodies. We determined the single-particle cryoEM structure of a therapeutic antibody (favezelimab) bound to LAG3 to 3.5 A resolution, revealing that favezelimab targets the LAG3-binding site for MHC class II, its canonical ligand. The small size of the complex between the conventional (monovalent) Fab of favezelimab and LAG3 ( approximately 100 kDa) presented a challenge for cryoEM. Accordingly, we engineered a bivalent version of Fab favezelimab that doubled the size of the Fab-LAG3 complex and conferred a highly identifiable shape to the complex that facilitated particle selection and orientation for image processing. This study establishes bivalent Fabs as new fiducial markers for cryoEM analysis of small proteins. CryoEM structure of a therapeutic antibody (favezelimab) bound to human LAG3 determined using a bivalent Fab as fiducial marker.,Mishra AK, Shahid S, Karade SS, Agnihotri P, Kolesnikov A, Hasan SS, Mariuzza RA Structure. 2023 Aug 10:S0969-2126(23)00277-0. doi: 10.1016/j.str.2023.07.013. PMID:37619561[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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