Biology subjects

Steiert, B.

Publications and source records attributed to Steiert, B..

5 recordsLinked to original sources

bioRxiv2025

The Chlamydia trachomatis secreted effector protein CT181 binds to Mcl-1 to prolong neutrophil survival

Chlamydia trachomatis (C.t) infections can lead to severe complications due to the pathogens ability to evade the host immune response, often resulting in asymptomatic infections. The mechanisms underlying this immune subversion remain incompletely understood but likely involve specific bacterial effector proteins. Here, we identify CT181 as a novel effector that directly binds to Mcl-1, a key regulator of neutrophil survival. While a C.t. CT181 mutant exhibited only modest defects in epithelial cell replication and inclusion development, it was essential for C.t. survival in neutrophils, correlating with Mcl-1 stabilization. Using a murine infection model, we demonstrate that CT181 is required for C.t. colonization and cytokine production in vivo. Our findings establish CT181 as the first bacterial effector protein known to bind Mcl-1 to enhance neutrophil survival, revealing a critical strategy by which C.t. promotes immune dysregulation, facilitating bacterial persistence while driving C.t. pathogenesis.

microbiology↗

bioRxiv2024

Chlamydia trachomatis TmeA promotes pedestal formation through N-WASP and TOCA-1 interactions

Chlamydia trachomatis (C.t.) is the causative agent of several human diseases, including the sexually transmitted infection chlamydia and eye infection trachoma. As an obligate intracellular bacterial pathogen, invasion is essential for establishing infection and subsequent pathogenesis. To facilitate invasion, C.t. secretes effector proteins through its type III secretion system (T3SS). These effectors facilitate bacterial entry by manipulating multiple pathways involved in host actin cytoskeletal regulation. Previous studies have demonstrated that the T3SS effector protein TmeA is crucial for C.t. invasion, as it recruits and activates N-WASP. This interaction leads to recruitment and activation of the Arp2/3 complex, promoting cytoskeletal rearrangements at the invasion site to facilitate C.t. uptake. In this study, we define the role of the N-WASP CRIB domain in mediating this interaction, showing that TmeA acts as a functional mimic of Cdc42 in activating N-WASP. Additionally, we identified TOCA-1 as another host protein that directly interacts with TmeA. In other bacterial pathogens, notably Enterohemorrhagic E. coli, N-WASP and TOCA-1 are hijacked to mediate pedestal formation. Using siRNA to knockdown N-WASP and TOCA-1, followed by transmission electron microscopic, we observed that both N-WASP and TOCA-1 are important for in C.t.-mediated pedestal formation. Collectively, these findings reveal a unique mechanism of TmeA-mediated invasion, where direct interactions with N-WASP and TOCA-1 facilitate pedestal formation. ImportanceChlamydia trachomatis (C.t.) is an obligate intracellular bacterial pathogen that poses a significant threat to human health, being associated with various diseases, including chlamydia-- the most prevalent bacterial sexually transmitted infection--and trachoma. While Chlamydia infections are often asymptomatic, they can lead to serious complications such as sterility, ectopic pregnancy, and increased risk of cervical and ovarian cancers. Due to its intracellular nature, host cell invasion is essential for C.t. survival. Here, we present new data detailing the binding interactions between the C.t. invasion effector protein TmeA and host cell proteins N-WASP and TOCA-1, demonstrating that both N-WASP and TOCA-1 are involved in pedestal formation during C.t. invasion. This research advances our understanding of TmeA-mediated host cell invasion, illuminating a key pathway required for C.t.-mediated pathogenesis.

microbiology↗

bioRxiv2024

Global mapping of the Chlamydia trachomatis conventional secreted effector-host interactome reveals CebN interacts with nucleoporins and Rae1 to impede STAT1 nuclear translocation.

To usurp host defenses and establish a replicative niche, obligate intracellular pathogens are tasked with remodeling the host cell using a comparatively small repertoire of effector proteins. For Chlamydia trachomatis (C.t), discovery of secreted proteins and their host targets has been particularly challenging due to the bacteriums historical genetic intractability. Using affinity purification-mass spectrometry, we defined host interaction partners for 21 secreted effector proteins, providing the first comprehensive type III secretion system (T3SS) effector- host interactome generated during infection. Among these, we show that the C-terminus of CebN (CT584) binds multiple nucleoporins and Rae1, host factors previously associated only with viral immune evasion. Remarkably, we shown that CebN localizes to the nuclear envelope not only in infected cells but also in uninfected bystander cells. Functionally, CebN is both necessary and sufficient to perturb STAT1 nuclear import following IFN-{gamma} stimulation and its expression is critical for C.t. survival, as evidenced by reduced bacterial replication and smaller inclusions in cells infected with a CebN mutant. Together, these finds expand our understanding of chlamydia effector biology and highlight novel bacterial strategies for manipulating host defenses at the nuclear pore. SIGNIFICANCEChlamydia trachomatis (C.t.) is a leading cause of sexually transmitted infections and blindness, yet the molecular mechanisms it uses to manipulate host defenses remain poorly defined. Unlike many pathogens, C.t. relies on a limited set of effectors to remodel the host cell and establish its niche. We identified host targets for 21 C.t. effector proteins. Focusing on CebN, we show that it binds nucleoporins and Rae1, host factors previously linked only to viral immune antagonism. CebN localizes to the nuclear envelope of both infected and bystander cells, and is critical for replication, inclusion development, and perturbation of STAT1 nuclear import following IFN-{gamma} stimulation. These findings uncover a novel strategy by which C.t. manipulates nuclear pore function to evade host defenses and establish infection.

microbiology↗

bioRxiv2023

Likelihood-ratio test statistic for the finite-sample case in nonlinear ordinary differential equation models

Likelihood ratios are frequently utilized as basis for statistical tests, for model selection criteria and for assessing parameter and prediction uncertainties, e.g. using the profile likelihood. However, translating these likelihood ratios into p-values or confidence intervals requires the exact form of the test statistics distribution. The lack of knowledge about this distribution for nonlinear ordinary differential equation (ODE) models requires an approximation which assumes the so-called asymptotic setting, i.e. a sufficiently large amount of data. Since the amount of data from quantitative molecular biology is typically limited in applications, this finite-sample case regularly occurs for mechanistic models of dynamical systems, e.g. biochemical reaction networks or infectious disease models. Thus, it is unclear whether the standard approach of using statistical thresholds derived for the asymptotic large-sample setting in realistic applications results in valid conclusions. In this study, empirical likelihood ratios for parameters from 19 published nonlinear ODE benchmark models are investigated using a resampling approach for the original data designs. Their distributions are compared to the asymptotic approximation and statistical thresholds are checked for conservativeness. It turns out, that corrections of the likelihood ratios in such finite-sample applications are required in order to avoid anti-conservative results. Author summaryStatistical methods based on the likelihood ratio are ubiquitous in mathematical modelling in systems biology. For example confidence intervals of estimated parameters rely on the statistical properties of the likelihood-ratio test. However, it is often overlooked that these intervals sizes rely on assumptions on the amounts of data, which are regularly violated in typical applications in systems biology. By checking the appropriateness of these assumptions in models from the literature, this study shows that in a surprisingly large fraction confidence intervals might be too small. Using a geometric interpretation of parameter estimation in the so-called data space, it is motivated why these issues appear and how they depend on the identifiability of the model parameters. In order to avoid such problematic situations, this work makes suggestions on how to adapt the statistical threshold values for likelihood-ratio test. By this, it can be assured that valid statistical conclusions are drawn from the analysis, also in situations where only smaller data sets are available. Such corrections yield for example more conservative confidence interval sizes and thus decrease a potential underestimation of the parameter uncertainty.

systems biology↗

bioRxiv2022

The Chlamydia trachomatis type III secreted effector protein CteG induces centrosome amplification through interactions with centrin-2

The centrosome is the main microtubule organizing center of the cell and is crucial for mitotic spindle assembly, chromosome segregation, and cell division. Centrosome duplication is tightly controlled, yet several pathogens, most notably oncogenic viruses, perturb this process leading to increased centrosome numbers. Infection by the obligate intracellular pathogen Chlamydia trachomatis (C.t.) correlates with blocked cytokinesis, supernumerary centrosomes, and multipolar spindles; however, the mechanisms behind how C.t. induces these cellular abnormalities from the confines of its inclusion, remain largely unknown. Here we show that the type III secreted effector protein, CteG, binds to centrin-2 (CETN2), a key structural component of centrosomes and regulator of centriole duplication. This interaction requires a functional calcium binding EF hand 4 of CETN2, which is recognized via the C-terminus of CteG. Significantly, we show that deletion of CteG, or knockdown of CETN2, significantly impairs chlamydias ability to induce centrosome amplification. Uniquely, we have identified the first bacterial effector to target centrins, crucial regulators of the eukaryotic cell cycle. These findings have not only allowed us to begin addressing how C.t. induces gross cellular abnormalities during infection, but also indicate that obligate intracellular bacteria may contribute to cellular transformation events that negatively impact host physiology even when the pathogen is long removed. Understanding the consequences of CteG-CETN2 interactions, its impact on centrosome amplification, and the long-term effect this has on host cells could explain why chlamydial infection leads to an increased risk of cervical or ovarian cancer. Significance StatementThe presence of more than two centrosomes is a hallmark of many types of cancer, including cervical and ovarian cancers of which Chlamydia trachomatis (C.t.) infection is a significant risk factor. Despite the importance of this problem, how C.t. orchestrates these drastic changes in the host cell remains poorly understood. Here, we describe how C.t. uses a single effector protein, CteG, to drive centrosome amplification via manipulation of a key regulator of centriole duplication, centrin-2. This work begins to define how C.t. induces centrosome amplification to promote its replication while potentially contributing to devastating long-term negative consequences for normal host physiology. Further it may help elucidate why chlamydial infection leads to an increased cancer risk.

microbiology↗