A conserved PLPLRT/SD motif of STING mediates the recruitment and activation of TBK1

• Published in: Nature (London) Vol. 569; no. 7758; pp. 718 - 722
• Main Authors: Zhao, Baoyu, Du, Fenglei, Xu, Pengbiao, Shu, Chang, Sankaran, Banumathi, Bell, Samantha L., Liu, Mengmeng, Lei, Yuanjiu, Gao, Xinsheng, Fu, Xiaofeng, Zhu, Fanxiu, Liu, Yang, Laganowsky, Arthur, Zheng, Xueyun, Ji, Jun-Yuan, West, A. Phillip, Watson, Robert O., Li, Pingwei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2019; Nature Publishing Group
• Subjects: 14/19; 631/250/262; 631/535/1258; 631/535/1266; 82/1; 82/103; 82/16; 82/29; 82/58; 82/80; 82/83; Amino Acid Motifs; Analysis; Antagonists; Autoimmune diseases; BASIC BIOLOGICAL SCIENCES; Chemical synthesis; Conserved Sequence; Crystallography, X-Ray; Cyclic GMP; EF hand proteins; Enzyme Activation; HEK293 Cells; Humanities and Social Sciences; Humans; Hydrogen bonds; Immune response; Influence; Interferon; Interferon regulatory factor 3; Interferon-beta - metabolism; Letter; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Models, Molecular; multidisciplinary; Mutation; Nucleic acids; Nucleotides, Cyclic - metabolism; Oligomerization; Peptides; Phosphorylation; Protein Binding; Protein kinases; Protein Serine-Threonine Kinases - metabolism; Science; Science (multidisciplinary); Signal Transduction; β-Interferon
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-019-1228-x

Nucleic acids from bacteria or viruses induce potent immune responses in infected cells 1 – 4 . The detection of pathogen-derived nucleic acids is a central strategy by which the host senses infection and initiates protective immune responses 5 , 6 . Cyclic GMP-AMP synthase (cGAS) is a double-stranded DNA sensor 7 , 8 . It catalyses the synthesis of cyclic GMP-AMP (cGAMP) 9 – 12 , which stimulates the induction of type I interferons through the STING–TBK1–IRF-3 signalling axis 13 – 15 . STING oligomerizes after binding of cGAMP, leading to the recruitment and activation of the TBK1 kinase 8 , 16 . The IRF-3 transcription factor is then recruited to the signalling complex and activated by TBK1 8 , 17 – 20 . Phosphorylated IRF-3 translocates to the nucleus and initiates the expression of type I interferons 21 . However, the precise mechanisms that govern activation of STING by cGAMP and subsequent activation of TBK1 by STING remain unclear. Here we show that a conserved PLPLRT/SD motif within the C-terminal tail of STING mediates the recruitment and activation of TBK1. Crystal structures of TBK1 bound to STING reveal that the PLPLRT/SD motif binds to the dimer interface of TBK1. Cell-based studies confirm that the direct interaction between TBK1 and STING is essential for induction of IFNβ after cGAMP stimulation. Moreover, we show that full-length STING oligomerizes after it binds cGAMP, and highlight this as an essential step in the activation of STING-mediated signalling. These findings provide a structural basis for the development of STING agonists and antagonists for the treatment of cancer and autoimmune disorders. A molecular model of STING-mediated signalling is proposed, as structural analysis identifies a crucial motif for the binding of TBK1 to STING, and a separate model involved in IRF-3 binding.