Biology subjects

Hammoudi, P.-M.

Publications and source records attributed to Hammoudi, P.-M..

3 recordsLinked to original sources

bioRxiv2024

Recognition of phylogenetically diverse pathogens through enzymatically amplified recruitment of RNF213

Innate immunity senses microbial ligands known as pathogen-associated molecular patterns (PAMPs). Except for nucleic acids, PAMPs are exceedingly taxa-specific, thus enabling pattern recognition receptors to detect cognate pathogens while ignoring others. How the E3 ubiquitin ligase RNF213 can respond to phylogenetically distant pathogens, including Gram-negative Salmonella, Gram-positive Listeria, and eukaryotic Toxoplasma, remains unknown. Here we report that the evolutionary history of RNF213 is indicative of repeated adaptation to diverse pathogen target structures, especially in and around its newly identified CBM20 carbohydrate-binding domain, which we have resolved by cryo-EM. We find that RNF213 forms coats on phylogenetically distant pathogens. ATP hydrolysis by RNF213s dynein-like domain is essential for coat formation on all three pathogens studied as is RZ finger-mediated E3 ligase activity for bacteria. Coat formation is not diffusion-limited but instead relies on rate-limiting initiation events and subsequent cooperative incorporation of further RNF213 molecules. We conclude that RNF213 responds to evolutionarily distant pathogens through enzymatically amplified cooperative recruitment.

molecular biology↗

bioRxiv2024

Shigella flexneri evades LPS ubiquitylation through IpaH1.4-mediated degradation of RNF213

The evolutionary arms race between pathogens and hosts has resulted in pathogens acquiring diverse adaptive countermeasures that antagonize host immunity. Ubiquitylation of lipopolysaccharide (LPS) on cytosol-invading bacteria by the E3 ligase RNF213 creates eat-me signals for antibacterial autophagy but whether and how cytosol-adapted bacteria avoid LPS ubiquitylation remains poorly understood. Here we show that Shigella flexneri, a professional cytosol-dwelling enterobacterium, actively antagonizes LPS ubiquitylation through IpaH1.4, a secreted effector protein with ubiquitin E3 ligase activity. IpaH1.4 binds to the LPS E3 ubiquitin ligase RNF213, ubiquitylates it, and targets it for degradation by the proteasome, thus preventing LPS ubiquitylation. To understand how IpaH1.4 recognizes RNF213, we determined the structure of their complex using cryogenic electron microscopy. The specificity of the interaction is achieved via the leucine rich repeat of IpaH1.4, which binds the RING domain of RNF213 by hijacking the conserved RING interface required for binding of ubiquitin-charged E2 enzymes. Interestingly, IpaH1.4 also targets the E3 ligase LUBAC - required for the synthesis of M1-linked ubiquitin chains on cytosol-invading bacteria downstream of RNF213 - as well as multiple other E3 ligases involved in inflammation and immunity - through binding to the E2-interacting face of their RING domains. We conclude that IpaH1.4 has evolved to antagonize multiple anti-bacterial and pro-inflammatory host E3 ligases.

molecular biology↗

bioRxiv2019

Treatment of mice with IL2-complex enhances inflammasome-driven IFN-γ production and prevents lethal toxoplasmosis

Toxoplasmic encephalitis is an AIDS-defining condition in HIV+ individuals. The decline of IFN-{gamma}-producing CD4+ T cells in AIDS is a major contributing factor in reactivation of quiescent Toxoplasma gondii to an actively replicating stage of infection. Hence, it is important to identify CD4-independent mechanisms to control acute T. gondii infection. Here we have investigated the targeted expansion and regulation of IFN-{gamma} production by CD8+ T cells, DN T cells and NK cells in response to T. gondii infection using IL-2 complex (IL2C) pre-treatment in an acute in vivo mouse model. Our results show that expansion of CD8+ T cells, DN T cells and NK cell by S4B6 IL2C treatment increases survival rates of mice infected with T. gondii and this increased survival is dependent on both IL-12- and IL-18-driven IFN-{gamma} production. Processing and secretion of IFN-{gamma}-inducing, bioactive IL-18 is dependent on the sensing of active parasite invasion by multiple redundant inflammasome sensors in multiple hematopoietic cell types but independent from T. gondii-derived dense granule (GRA) proteins. Our results provide evidence for a protective role of IL2C-mediated expansion of CD8+ T cells, DN T cells and NK cells in murine toxoplasmosis and may represent a promising adjunct therapy for acute toxoplasmosis.\n\nAuthor SummaryA third of the worlds population is chronically infected with the parasite Toxoplasma gondii. In most cases the infection is asymptomatic, but in individuals suffering from AIDS, reactivation of brain and muscle cysts containing T. gondii is a significant cause of death. The gradual decline of CD4 T cells, the hallmark of AIDS, is believed to be a major contributing factor in reactivation of T. gondii infection and the development of acute disease. In this study, we show that targeted expansion of non-CD4 immune cell subsets can prevent severe disease and premature death via increased availability of interferon gamma-producing immune cells. We also demonstrate that the upstream signaling molecule interleukin-18 is required for the protective immune response by non-CD4 cells and show that the sensing of active parasite invasion by danger recognition molecules is crucial. Our findings reveal that targeted cell expansion may be a promising therapy in toxoplasmosis and suggests that the development of novel intervention strategies targeting danger recognition pathways may be useful against toxoplasmosis, particularly in the context of AIDS.

microbiology↗