Laboratories

Research

Main Scientific Achievements

• Discovery that interferon-induced GTPase family of guanylate-binding proteins (GBPs) transform the surface of cytosol-invading bacteria into a signalling platform for activation of the lipopolysaccharide receptor, Caspase-4.
• Revelation that GBPs acting in a hierarchical manner recruit and activate Caspase-4 to (i) trigger gasdermin-D dependent pyroptotic death of infected cells, thus limiting the bacterial burden, and to (ii) initiate processing of the pro-inflammatory cytokine IL-18, thus promoting inflammation.
• Finding that GBP1 immobilises the cytosolic pathogen Shigella flexneri by inhibiting bacterial actin-dependent motility.
• Uncovering that Galectin-8 is a novel cytosolic danger receptor that accumulates on damaged host endo-membranes, where it serves as an autophagy inducing signal and is crucial for the defence against cytosol-invading bacteria.

Research Description

The immune system identifies and eliminates microorganisms that breach the integrity of our tissues, but we are only beginning to uncover the intracellular mechanisms that engage invading pathogens to restrict infection. Not only specialised immune cells, but also regular cells (e.g. epithelial cells) have evolved complex autonomous mechanisms to detect and respond to infection. Exposure to cytokines, e.g. interferons (IFNs), enhances cell-autonomous immunity for efficient control of diverse intracellular pathogens through the induction of target genes. On the other hand, pathogens devise various adaptation strategies to evade or overcome those defence mechanisms.

A prime example of the IFN-induced pro-inflammatory immunity factors are the GTPases from the guanylate-binding proteins (GBPs) family. GBPs sense cytosolic bacteria to form a signalling platform, which by recruiting and activating the cytosolic lipopolysaccharide receptor, Caspase-4, initiates pyroptotic death of infected cells and, via the pro-inflammatory cytokine IL-18, informs immune cells of the ongoing infection. However, despite recent advances, and in contrast to relatively well-studied anti-viral immunity, the molecular details of how cytokine-enhanced immunity protects the cell interior against bacterial, and especially fungal pathogens, is severely understudied.

Through generous funding from EMBO, NAWA and NCN, in the laboratory we endeavour to understand intracellular mechanisms of anti-microbial immunity. We investigate the cytokine-induced anti-pathogen state activated to resist bacterial infection. We are also initiating a research program to study the host-fungi interactions and anti-fungal cell-intrinsic and innate immune defences. At the molecular level, we research how our body cells recognise microorganisms and to what immune response it leads – which signalling pathways are activated, what is the fate of the detected pathogen and the host cell, and why? Also, we are interested in the subversive strategies pathogens have developed to evade the immune system. We employ large-scale state-of-the-art screening approaches to identify novel host factors of the cell-autonomous and cytokine-inducible anti-microbial defence mechanisms of the innate immunity. Moreover, we aim to determine the specific molecular mechanisms of action of newly identified immunity factors.

The identification of host restriction factors may allow future development of novel therapeutics directed against pathogenic microorganisms, including difficult to treat multidrug resistant strains. Furthermore, since IFN plays an essential role in the development of systemic autoimmunity, understanding of the molecular mechanisms initiating pro-inflammatory processes may lead to better treatment of inflammatory diseases.

Methodology

Using cutting-edge technologies, we are driving a deeper understanding of how core immunological processes are regulated in favour of the host, or the pathogen, and how these new mechanisms might be harnessed to treat diverse diseases. We employ state-of-the-art screening approaches to identify host restriction factors required for defence against pathogenic microorganisms. Using a combination of molecular biology, cell biology, genetics, proteomics, biochemistry and microbiology, we determine the specific mechanism of action of novel immunity factors, to understand their effector functions, downstream signalling and pro-inflammatory potential.

More specifically, our primary experimental models are mammalian cells infected in vitro with pathogens in the safe environment of a modern BSL2 cell culture laboratory. We have extensive experience in cell manipulation (e.g., transfection, retroviral/lentiviral transduction, RNAi gene silencing, and CRISPR/Cas9 technology). Amongst many techniques, we routinely use standard techniques of molecular biology (e.g. cloning and mutagenesis of DNA, large scale recombinant protein expression and purification from bacterial systems, Western blotting), and cell biology of infection (e.g. fluorescent microscopy).

Selected Publications

• Guanylate-binding proteins convert cytosolic bacteria into caspase-4 signaling platforms. Wandel MP#, Kim B-H, Park E-S, Boyle KB, Nayak K, Lagrange B, Herod A, Henry T, Zilbauer M, Rohde J, MacMicking JD, Randow F# (#corresponding authors). Nature Immunology. 2020. doi: 10.1038/s41590-020-0697-2.
• GBPs Inhibit Motility of Shigella flexneri but Are Targeted for Degradation by the Bacterial Ubiquitin Ligase IpaH9.8. Wandel MP*, Pathe C*, Werner EI, Ellison CJ, Boyle KB, von der Malsburg A, Rohde J, Randow F (*equal contribution). Cell Host and Microbe. 2017. doi: 10.1016/j.chom.2017.09.007.
• Sterical hindrance promotes selectivity of the autophagy cargo receptor NDP52 for the danger receptor galectin-8 in antibacterial autophagy. Li S*, Wandel MP*, Li F, Liu Z, He C, Wu J, and Shi Y, Randow F (*equal contribution). Science Signaling. 2013. doi: 10.1126/scisignal.2003730.
• Galectin 8 targets damaged vesicles for autophagy to defend cells against bacterial invasion. Thurston TLM, Wandel MP, Muhlinen Von N, Foeglein Á, and Randow F. Nature. 2012. doi: 10.1038/nature10744.