8dgg
Structure of glycosylated LAG-3 homodimer
Structural highlights
FunctionLAG3_MOUSE Lymphocyte activation gene 3 protein: Inhibitory receptor on antigen activated T-cells (PubMed:12209638, PubMed:12421911, PubMed:12672063, PubMed:15100286, PubMed:15634887, PubMed:30580966). Delivers inhibitory signals upon binding to ligands, such as FGL1 (PubMed:30580966). FGL1 constitutes a major ligand of LAG3 and is responsible for LAG3 T-cell inhibitory function (PubMed:30580966). Following TCR engagement, LAG3 associates with CD3-TCR in the immunological synapse and directly inhibits T-cell activation (PubMed:12209638, PubMed:12421911, PubMed:12672063, PubMed:15100286, PubMed:15634887). May inhibit antigen-specific T-cell activation in synergy with PDCD1/PD-1, possibly by acting as a coreceptor for PDCD1/PD-1 (PubMed:21300912). Negatively regulates the proliferation, activation, effector function and homeostasis of both CD8(+) and CD4(+) T-cells (PubMed:12209638, PubMed:12421911, PubMed:12672063, PubMed:15100286, PubMed:15634887). Also mediates immune tolerance: constitutively expressed on a subset of regulatory T-cells (Tregs) and contributes to their suppressive function (PubMed:15485628). Also acts as a negative regulator of plasmacytoid dendritic cell (pDCs) activation (PubMed:19201841). Binds MHC class II (MHC-II); the precise role of MHC-II-binding is however unclear (PubMed:12209638, PubMed:12421911, PubMed:15634887).[1] [2] [3] [4] [5] [6] [7] [8] [9] 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.[10] Publication Abstract from PubMedLymphocyte activation gene-3 (LAG-3) is an inhibitory receptor expressed on activated T cells and an emerging immunotherapy target. Domain 1 (D1) of LAG-3, which has been purported to directly interact with major histocompatibility complex class II (MHCII) and fibrinogen-like protein 1 (FGL1), has been the major focus for the development of therapeutic antibodies that inhibit LAG-3 receptor-ligand interactions and restore T cell function. Here, we present a high-resolution structure of glycosylated mouse LAG-3 ectodomain, identifying that cis-homodimerization, mediated through a network of hydrophobic residues within domain 2 (D2), is critically required for LAG-3 function. Additionally, we found a previously unidentified key protein-glycan interaction in the dimer interface that affects the spatial orientation of the neighboring D1 domain. Mutation of LAG-3 D2 residues reduced dimer formation, dramatically abolished LAG-3 binding to both MHCII and FGL1 ligands, and consequentially inhibited the role of LAG-3 in suppressing T cell responses. Intriguingly, we showed that antibodies directed against D1, D2, and D3 domains are all capable of blocking LAG-3 dimer formation and MHCII and FGL-1 ligand binding, suggesting a potential allosteric model of LAG-3 function tightly regulated by dimerization. Furthermore, our work reveals unique epitopes, in addition to D1, that can be targeted for immunotherapy of cancer and other human diseases. Structural insights reveal interplay between LAG-3 homodimerization, ligand binding, and function.,Silberstein JL, Du J, Chan KW, Frank JA, Mathews II, Kim YB, You J, Lu Q, Liu J, Philips EA, Liu P, Rao E, Fernandez D, Rodriguez GE, Kong XP, Wang J, Cochran JR Proc Natl Acad Sci U S A. 2024 Mar 19;121(12):e2310866121. doi: , 10.1073/pnas.2310866121. Epub 2024 Mar 14. PMID:38483996[11] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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