Eligible Student Poster 49th Lorne Conference on Protein Structure and Function 2024

Structural studies of cell signalling adaptor protein STimulator of INterferon Genes (STING) in complex with small molecule inhibitors (#125)

Maria Eleni Georgopoulou 1 2 , Claire M Weekley 1 2 3 , Tracy L Nero 1 3 , Eric Hanssen 1 2 4 , Bruce Wong 1 , Juliet Taylor 1 , Peter 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 an endoplasmic reticulum associated membrane signalling protein, functioning as a small homodimer of 80 kDa with its C-terminal ligand binding domain 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, only few STING inhibitors have reached the pre-clinical stage, and none have made it to clinical trials [5, 6].

Our research aims to shed light on the molecular mechanisms of STING inhibition by providing structural insights into inhibitor-STING complexes. Currently, there are only structures of STING with activators, but none with inhibitors. We will explore druggable pockets located in full-length human STING with a series of inhibitors that have been previously reported in the literature but lack structural validation. We will use direct binding assays and cryo-electron microscopy to confirm binding and guide structure-based drug design. Progress has been made towards the expression, purification and characterisation of full-length human STING and I will report advances in cryo-EM experiments and direct binding assays, exploring how STING interacts with the selected 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.