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Cryo-EM structure of the ectodomain of BTN2A1-BTN3A1-BTN3A2 in complex with gdTCR
Structural highlights
FunctionBT3A2_HUMAN Plays a role in T-cell responses in the adaptive immune response. Inhibits the release of IFNG from activated T-cells.[1] [2] Publication Abstract from PubMedPhosphoantigens (pAgs), produced by infected or cancer cells, trigger the assembly of a membrane receptor complex comprising butyrophilin (BTN) members BTN3A1 and BTN2A1, leading to the activation of gammadelta T cells. BTN3A2 or BTN3A3 forms heteromers with BTN3A1, exhibiting higher gammadelta T cell receptor (TCR)-stimulating activity than BTN3A1 homomers. Cryoelectron microscopy (cryo-EM) structure reveals a pAg-induced BTN2A1-BTN3A1 heterotetramer with a 2:2 stoichiometry, stabilized by interactions between the intracellular B30.2 domains and the extracellular immunoglobulin V (IgV) domains. BTN3A2 or BTN3A3 heterodimerizes with BTN3A1, forming a pAg-induced tetrameric complex with BTN2A1. However, BTN3A1 heterodimers are more stable than BTN3A1 homodimers in this interaction. Cryo-EM reveals that BTN2A1-BTN3A1-BTN3A2 binds two gammadelta TCR ectodomains, with one being sandwiched between the IgV domains of BTN2A1 and BTN3A2, while the other interacts with the free BTN2A1 IgV in the complex, as evidenced by functional data. Together, our findings uncover the mechanism of ligand-induced inside-out stabilization of BTN receptor complexes for dimeric activation of gammadelta TCR. Phosphoantigen-induced inside-out stabilization of butyrophilin receptor complexes drives dimerization-dependent gammadelta TCR activation.,Zhu Y, Gao W, Zheng J, Bai Y, Tian X, Huang T, Lu Z, Dong D, Zhang A, Guo C, Huang Z Immunity. 2025 Apr 30:S1074-7613(25)00175-X. doi: 10.1016/j.immuni.2025.04.012. PMID:40334665[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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