Primary research interest

Cellular response to foreign nucleic acids

About me

Research and teaching in immunology

Following my PhD on transcriptional regulation in macrophages I went in 1996 to the University of Cambridge on a CJ Martin Fellowship to work in a molecular parasitology laboratory. I returned to the Institute for Molecular Bioscience at The University of Queensland in 1998 where I continued work on immune cell responses to foreign DNA. I was awarded an Australian Research Council Future Fellowship in 2009 to move to the School of Chemistry & Molecular Biosciences.

Research focus and collaborations

Pathogen recognition by the innate immune system

The broad theme of my laboratory is innate immune cell recognition of pathogens. The last decade has seen an explosion of information on how cells identify the presence of invading organisms. This principally involves cells of the innate immune system which identify an infection and subsequently activate the acquired immune system (T and B cells). “Pattern recognition receptors” (PRR) on innate immune cells bind to characteristically foreign molecules which are conserved amongst groups of pathogens. These foreign molecules are called “PAMPs” or “Pathogen associated molecular patterns”. The bacterial cell wall provides many PAMPs for recognition of bacterial infection, such as lipopolysaccharide, peptidoglycan, lipoproteins and flagellin. Detection of viral infection is more challenging, as viruses have very diverse molecules and can evolve rapidly to evade detection. However all viruses carry nucleic acids, and these are emerging as key to the initiation of anti-viral responses. The particular focus of my laboratory is cellular recognition of foreign nucleic acids. These responses are relevant not only to infectious disease, but also to the autoimmune disease lupus, other inflammatory conditions and possibly cancer. A knowledge of cellular responses to introduced DNA will also aid improvements in techniques which rely on the introduction of DNA into cells, such as experimental transfection and gene therapy.

Recognition of foreign extracellular/endosomal DNA

Responses of cells to foreign DNA fall into two categories. Firstly, Toll-like receptor 9 (TLR9) recognises DNA within the endosomal compartment. This DNA can arise from the uptake of free DNA by cell surface receptors, or by uptake of organisms which are broken down in the phagosomal/endosomal system, releasing DNA. TLR9 responses are elicited by DNA which is deficient in methylation of the cytosine residue in CG dinucleotides. Vertebrate DNA is not stimulatory, due to a low frequency of unmethylated CG sequences. These bacterial and viral “CpG” motifs trigger cellular signalling leading to secretion of inflammatory cytokines and enhancement of antigen presenting cell function. TLR9 responses are seen in murine B cells and macrophages, and will stimulate immune defence, without implying that the responding cell is infected, since DNA was only recognised within the endosomal compartment.

Recognition of cytosolic DNA

Several other systems of DNA recognition operate in the cytoplasm of infected cells, and are likely to be critical in recognition of infection of cells with DNA viruses and retroviruses. Cells respond to cytosolic DNA with secretion of interferon-beta, a powerful anti-viral molecule, as well as cell death and secretion of the inflammatory cytokine interleukin-1beta (IL-1beta). Both cell death and IL-1beta are dependent on recognition of foreign DNA by the PYHIN (HIN-200) protein AIM2, which initiates formation of the “inflammasome” – a protein complex which recruits and activates the protease caspase 1. Caspase 1 cleaves pro-IL-1beta prior to its secretion, and also initiates “pyroptosis”- rapid lytic cell death which promotes inflammation. We recently discovered that the inflammasome initiates a second pathway of cell death (apoptotic death) in parallel, via activation of caspase 8. We showed that the function of AIM2 is inhibited by another DNA-binding PYHIN family member p202. p202 is variably expressed between mouse strains and may be involved in susceptibility to viral or bacterial infection. Work in our lab continues to investigate the role of PYHIN proteins in responses to foreign DNA, as well as the evolution of defences against DNA. We are particularly interested in mechanisms of cell death mediated by recognition of foreign DNA, and the relevance of these pathways to autoimmunity.

colocalisation between p202 and microinjected DNA
DNA introduced into the cytoplasm of cells is rapidly recognised by members of the PYHIN family, AIM2 and p202. Here, colocalisation between p202 and microinjected DNA is shown

Projects

  • Initiation of cell death pathways by recognition of cytosolic DNA
  • Evolution of defences against invading DNA
  • Structure and functional analysis of PYHIN (HIN-200) proteins
  • Responses to DNA in the autoimmune disease systemic lupus erythematosus
  • Protein-protein interactions involved in inflammasome-induced apoptotic death
  • Endogenous retroelements in cancer

Collaborations

  • Prof Hao Wu, Harvard Medical School. Structure and function of PYHIN proteins
  • Assoc Prof Richard Ferrero, Monash University. Innate immune stimulation by bacterial outer membrane vesicles
  • Dr Matt Sweet, University of Queensland. Anti-microbial effects of zinc
  • Assoc Prof Mariapia Degli-Esposti, Lions Eye Institute WA. Inflammasome-mediated responses to MCMV
  • Dr Michelle Wykes, QIMR. Inflammasome responses in malarial infection
  • Dr Kate Schroder, University of Queensland. Protein-protein interactions in the inflammasome

Funded projects

  • NHMRC Research Fellowship (SRFA) 2014-2018, Inflammasome function in protection against infectious disease and autoimmunity
  • NHMRC Project Grant 2014-2016, PR Young, KJ Stacey & JM Mackenzie, The dengue virus glycoprotein NS1 binds cholesterol and mediates cellular activation, Total value of grant: $611,226
  • NHMRC Project Grant 2013-2015, KJ Stacey & K Schroder, Caspase 8 apoptotic signalling induced by the inflammasome, Total value of grant: $582,000
  • NHMRC Project Grant 2011-2013, KJ Stacey & TL Roberts, The mechanism of death in response to cytoplasmic DNA, and its role in tumour suppression, Total value of grant: $500,000
  • NHMRC Project Grant 2010-2012 KJ Stacey, TL Roberts & MJ Sweet, Cytoplasmic DNA as a danger signal for mammalian cells, Total value of grant: $571,000
  • ARC Discovery Grant 2012-2014, KJ Stacey, Combatting DNA: A process conserved in evolution?, Total value of grant: $295,000
  • ARC Discovery Grant 2012-2014, RL Ferrero (Monash University) & KJ Stacey, Caspase 8 apoptotic signalling induced by the inflammasome, Total value of grant: $270,000
  • ARC Future Fellowship 2009-2013, Foreign DNA is a danger signal for mammalian cells, Total value of grant: $686,400

Teaching interests

Achievements and awards

  • 2011 Immunology and Cell Biology Chris and Bhama Parish Publication of the Year Award (TL Roberts, first author)
  • 2010 NHMRC Career Development Award Level 2 (not taken up)
  • 2009 ARC Future Fellowship
  • 2004 University of Queensland Fellowship for Women (part-time)
  • 1996 CJ Martin Fellowship

Featured publications

Researcher biography

Following my PhD on transcriptional regulation in macrophages I went in 1996 to the University of Cambridge on a CJ Martin Fellowship to work in a molecular parasitology laboratory. I returned to the Institute for Molecular Bioscience at the University of Queensland in 1998 where I continued work on immune cell responses to foreign DNA. I was awarded an ARC Future Fellowship in 2009 to move to the School of Chemistry and Molecular Bioscience, where I also lecture in immunology