Biology subjects

Fisch, D.

Publications and source records attributed to Fisch, D..

5 recordsLinked to original sources

bioRxiv2025

Wall teichoic acid is required for DNA-triggered innate immune receptor activation by Staphylococcus aureus

Receptors that stimulate inflammation are commonly activated by ligands that are buried within microbial cells. The mechanisms that facilitate immunostimulatory ligand release from microbes during infection are largely undefined. Using the pathogen Staphylococcus aureus, we describe wall teichoic acid (WTA) as a critical mediator of DNA release from bacterial cells during infection. Mechanistically, we found that the -glycosylated form of WTA, generated by the enzyme TarM, is the primary mediator of bacterial DNA release within macrophages. This process is antagonized by the enzyme O-acetyltransferase, which prevents WTA attachment to peptidoglycan. This competition among peptidoglycan modifying enzymes determines activation of cytosolic DNA receptors AIM2 and cGAS. WTA therefore operates as a meta-regulator of inflammation, by controlling the availability of microbial ligands that stimulate innate immunity.

immunology↗

bioRxiv2023

p97/VCP targets Toxoplasma gondii vacuoles for parasite restriction in interferon-stimulated human cells

Infection with the parasite Toxoplasma gondii leads to production of interferon gamma (IFN{gamma}) that stimulates cells to upregulate defence proteins targeting the parasite for cell intrinsic elimination or growth restriction. Various host defence mechanisms operate at the parasitophorous vacuole (PV) in different human cell types leading to PV disruption, acidification, or membrane envelopment. Ubiquitin and p62 are players in all human host control mechanisms of Toxoplasma, but other unifying proteins have not been identified. Here, we show that p97/valosin-containing protein (VCP), as well as its associated proteins ANKRD13A and UBXD1 control Toxoplasma infection while recruited to the PV in IFN{gamma}-stimulated endothelial cells. Convergent deposition of ANKRD13A, p97/VCP and UBXD1 onto the same vacuole is dependent on vacuolar ubiquitination and observed within 2h post-infection. ANKRD13A, p97/VCP and UBXD1 all drive the acidification mechanism of the vacuole, which is the IFN{gamma}-dependent control pathway of Toxoplasma in endothelial cells. We assessed p97/VCP in Toxoplasma control in various human cells and demonstrate that p97/VCP is a universal IFN{gamma}-dependent host restriction factor targeting the Toxoplasma PV in epithelial (HeLa) and endothelial cells (HUVEC), fibroblasts (HFF) and macrophages (THP1).

immunology↗

bioRxiv2021

Toxoplasma-proximal and distal control by GBPs in human macrophages

Human guanylate-binding proteins (GBPs) are key players of interferon-gamma (IFN{gamma})-induced cell intrinsic defense mechanisms targeting intracellular pathogens. In this study we combine the well-established Toxoplasma gondii infection model with three in vitro macrophage culture systems to delineate the contribution of individual GBP family members to control this apicomplexan parasite. Use of high-throughput imaging assays and genome engineering allowed us to define a role for GBP1, 2 and 5 in parasite infection control. While GBP1 performs a pathogen-proximal, parasiticidal and growth-restricting function through accumulation at the parasitophorous vacuole of intracellular Toxoplasma, GBP2 and 5 perform a pathogen-distal, growth-restricting role. We further find that mutants of the GTPase or isoprenylation site of GBP1/2/5 affect their normal function in Toxoplasma control by leading to mis-localization of the proteins.

microbiology↗

bioRxiv2020

The Gb3-enriched CD59/flotillin plasma membrane domain regulates host cell invasion by Pseudomonas aeruginosa

The opportunistic pathogen Pseudomonas aeruginosa is responsible for a high number of acute and chronic hospital-acquired infections. As it develops more and more resistances against existing antibiotics, P. aeruginosa has been placed highest on the global priority list of antibiotic-resistant bacteria for which alternative treatments are urgently needed. Former studies have highlighted the crucial role of the bacterial lectin LecA and the host cell glycosphingolipid globotriaosylceramide (Gb3) for the cellular uptake of P. aeruginosa into epithelial cells via the lipid zipper mechanism. To further characterize the host cell plasma membrane domain for LecA-driven attachment and invasion, we analyzed the protein and lipid composition of pulled-down membrane domains for novel interaction partners of LecA by mass spectrometry. We unraveled a predilection of LecA for binding to saturated Gb3 species in the extracellular membrane leaflet and an induction of dynamic phosphatidylinositol (3,4,5)-trisphosphate clusters at the intracellular leaflet co-localizing with sites of LecA binding. Moreover, we identified the GPI-anchored protein CD59 and flotillins, known as cargo and eponymous component of flotillin-assisted endocytosis, as LecA interaction partners. Depletion of each of these host cell proteins resulted in more than 50% of reduction in invasiveness of the P. aeruginosa strain PAO1 highlighting the importance of this LecA-induced plasma membrane domain. Our strategy to reduce the complexity of host-pathogen interactions by first identifying interaction partners of a single virulence factor and subsequently transferring these findings to the bacterium has been proven to be a successful approach in elucidating the molecular mechanisms of bacterial infections.

cell biology↗

bioRxiv2019

Differential spatiotemporal targeting of Toxoplasma and Salmonella by GBP1 assembles caspase signalling platforms

Guanylate binding proteins (GBPs), a family of interferon (IFN)-inducible GTPases, can promote cell-intrinsic defense by removal of intracellular microbial replicative niches through host cell death. GBPs target pathogen-containing vacuoles or the pathogen itself, and assist in membrane-disruption and release of microbial molecules that trigger cell death by activating the inflammasomes. We previously showed that GBP1 mediates atypical apoptosis or pyroptosis of human macrophages infected with Toxoplasma gondii (Tg) or Salmonella enterica Typhimurium (STm), respectively. In mice, the p47 Immunity-related GTPases (IRGs) control the recruitment of GBPs to microbe-containing vacuoles and subsequent cell death. However, humans are devoid of functional IRGs, and the pathogen-proximal immune detection mechanisms by GBP1 are poorly understood. Here, we describe two novel single-cell assays which show that GBP1 promotes the lysis of Tg-containing vacuoles and Tg plasma membrane, resulting in the cytosolic detection of Tg-DNA. In contrast, we show GBP1 only targets cytosolic STm and does not contribute to bacterial escape into the cytosol of human macrophages. GBP1 interacts with caspase-4 and recruits it directly to the bacterial surface, where caspase-4 can be activated by LPS. During STm infection, caspase-1 cleaves and inactivates GBP1 at Asp192, a site conserved in related mammalian GBP1 proteins but not in murine Gbps. STm-infected human macrophages expressing a cleavage-deficient GBP1 mutant exhibit higher pyroptosis due to the absence of caspase-1-mediated feedback inhibition of the GBP1-caspase-4 pathway. Our comparative studies elucidate microbe-specific spatiotemporal roles of GBP1 in detecting infection and the assembly and regulation of divergent caspase signaling platforms.

microbiology↗