Poster Presentation The 48th Lorne Conference on Protein Structure and Function 2023

Structural studies of cell signalling adaptor protein STimulator of INterferon Genes in complex with small molecule inhibitors (#116)

Maria Eleni Georgopoulou 1 2 , Claire M. Weekley 1 2 3 , Tracy L. Nero 1 3 , Eric G. Hanssen 2 4 , Bruce X. Wong 1 , Juliet M. Taylor 1 , Peter J. Crack 1 , Michael W. Parker 1 2 3 5
  1. Department of Biochemistry and Pharmacology, Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
  2. ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
  3. Australian Cancer Research Foundation Facility for Innovative Cancer Drug Discovery, Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
  4. Ian Holmes Imaging Centre, Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
  5. Australian Cancer Research Foundation Rational Drug Discovery Centre, St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia

Stimulator of interferon genes, also known as STING, is a key facilitator of innate immunity. It is a membrane signalling protein, and functions as a small homodimer of 80 kDa whose C-terminal ligand binding domain is exposed in the cytosol. When the monomers come together to form the dimer, the C-terminal region of each monomer forms a butterfly-shaped ligand binding site [1].

STING has the ability to sense pathogen or damage-associated molecular patterns (PAMPs and DAMPs), which are conserved molecular motifs secreted upon pathogen infection or by stressed, damaged, dying, or cancerous cells. A broad range of dsDNA, cyclic dinucleotides, and cGAMP are responsible for STING activation triggering a downstream cascade of signalling events that lead to the production of interferons [2, 3]. Given its role in the first line of cell defense to maintain immune homeostasis, STING is very important in the context of disease. Its activation has been linked with pathogen neutralisation and cancer treatment with immunotherapy. On the other hand, prolonged or chronic stimulation of the STING pathway has been associated with hyperinflammation, autoimmune diseases and the detrimental effects observed in traumatic brain injury [2, 4]. Dampening the STING pathway might be beneficial in many cases. Unfortunately, few STING inhibitors have reached the pre-clinical stage, and none have made it to clinical trials [5, 6].

We aim to explore druggable pockets located in human STING with small molecule inhibitors and use direct binding assays and cryo-electron microscopy to confirm binding and guide structure-based drug design. Inhibitors of STING have been identified through in silico screening and confirmed with in vitro assays. Progress has been made towards the expression of full-length human STING with the BacMam system and I will report advances in the expression and purification of STING and its interactions with selected small molecule inhibitors.

  1. Shang, G., et al., Cryo-EM structures of STING reveal its mechanism of activation by cyclic GMP–AMP. Nature, 2019. 567(7748): p. 389-393.
  2. Ergun, S.L. and L. Li, Structural insights into STING signaling. Trends in Cell Biology, 2020. 30(5): p. 399-407.
  3. Zhang, H., Q.-D. You, and X.-L. Xu, Targeting stimulator of interferon genes (STING): a medicinal chemistry perspective. Journal of medicinal chemistry, 2019. 63(8): p. 3785-3816.
  4. Abdullah, A., et al., STING-mediated type-I interferons contribute to the neuroinflammatory process and detrimental effects following traumatic brain injury. Journal of neuroinflammation, 2018. 15(1): p. 1-17.
  5. Guerini, D., STING agonists/antagonists: their potential as therapeutics and future developments. Cells, 2022. 11(7): p. 1159.
  6. Kong, X., et al., STING as an emerging therapeutic target for drug discovery: perspectives from the global patent landscape. Journal of Advanced Research, 2022.