Novel c-di-GMP recognition modes of the mouse innate immune adaptor protein STING

Acta Crystallogr D Biol Crystallogr. 2013 Mar;69(Pt 3):352-66. doi: 10.1107/S0907444912047269. Epub 2013 Feb 16.

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.

Keywords: c-di-GMP; innate immune receptors; mouse STING; π-helix.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptive Immunity
  • Animals
  • Crystallography, X-Ray
  • Cyclic GMP / analogs & derivatives*
  • Cyclic GMP / chemistry
  • Cyclic GMP / metabolism
  • Immunity, Innate
  • Membrane Proteins / chemistry*
  • Membrane Proteins / metabolism*
  • Mice

Substances

  • Membrane Proteins
  • Sting1 protein, mouse
  • bis(3',5')-cyclic diguanylic acid
  • Cyclic GMP

Associated data

  • PDB/4G3L
  • PDB/4G4D