title: Novel c-di-GMP recognition modes of the mouse innate immune adaptor protein STING.
abstract: The mammalian ER protein STING (stimulator of interferon genes; also known as MITA, ERIS, MPYS or TMEM173) is an adaptor protein that links the detection of cytosolic dsDNA to the activation of TANK-binding kinase 1 (TBK1) and its downstream transcription factor interferon regulatory factor 3 (IFN3). Recently, STING itself has been found to be the direct receptor of bacterial c-di-GMP, and crystal structures of several human STING C-terminal domain (STING-CTD) dimers in the apo form or in complex with c-di-GMP have been published. Here, a novel set of structures of mouse STING-CTD (mSTING(137-344)) in apo and complex forms determined from crystals obtained under different crystallization conditions are reported. These novel closed-form structures exhibited considerable differences from previously reported open-form human STING-CTD structures. The novel mSTING structures feature extensive interactions between the two monomers, a unique asymmetric c-di-GMP molecule with one guanine base in an unusual syn conformation that is well accommodated in the dimeric interface with many direct specific interactions and two unexpected equivalent secondary peripheral c-di-GMP binding sites. Replacement of the amino acids crucial for specific c-di-GMP binding in mSTING significantly changes the ITC titration profiles and reduces the IFN-β reporter luciferase activity. Taken together, these results reveal a more stable c-di-GMP binding mode of STING proteins that could serve as a template for rational drug design to stimulate interferon production by mammalian cells.
authors.affiliation: Agricultural Biotechnology Center, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Ko-Hsin
authors.initials: KH
authors.lastname: Chin
authors.forename: Zhi-Le
authors.initials: ZL
authors.lastname: Tu
authors.forename: Yi-Che
authors.initials: YC
authors.lastname: Su
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Yu
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Chen
authors.forename: Yuan-Chao
authors.initials: YC
authors.lastname: Lo
authors.forename: Chin-Pan
authors.initials: CP
authors.lastname: Chen
authors.forename: Glen N
authors.initials: GN
authors.lastname: Barber
authors.forename: Mary Lay-Cheng
authors.initials: ML
authors.lastname: Chuah
authors.forename: Zhao-Xun
authors.initials: ZX
authors.lastname: Liang
authors.forename: Shan-Ho
authors.initials: SH
authors.lastname: Chou
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D018360:Crystallography, X-Ray; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D007113:Immunity, Innate; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D000099197:STING Protein
chemical_list: D006152:Cyclic GMP; D008565:Membrane Proteins; C530855:Sting1 protein, mouse; D000099197:STING Protein; C062025:bis(3',5')-cyclic diguanylic acid
keywords: c-di-GMP; innate immune receptors; mouse STING; π-helix