Biology subjects

Subtil, A.

Publications and source records attributed to Subtil, A..

6 recordsLinked to original sources

bioRxiv2025

IFN-I exacerbates the inflammatory response of epithelial cells to Chlamydia trachomatis infection by enhancing TLR3 expression

The inflammation induced by Chlamydia trachomatis infection in the female genital tract (FGT) can have severe consequences. Recent observations in women and mice infected with Chlamydia suggest that type I interferon (IFN-I) may have deleterious effects. This study aimed at elucidating the consequences of IFN-I production on C. trachomatis-induced inflammation in epithelial cells and the molecular pathway(s) involved. We showed that combination of IFN-I and Chlamydia resulted in a stronger induction of inflammation than Chlamydia alone, while IFN-I alone had no effect. Inhibiting AKT and mTOR, but not silencing STAT1, significantly attenuated the synergetic effect between IFN-I and bacteria on inflammation. Inhibition of ERK also blocked this synergistic effect, although ERK were not activated by IFN-I. We hypothesized that IFN-I enhanced the expression of a pathogen recognition receptor of the host, thereby potentiating detection of the bacteria and the subsequent inflammatory response. IFN-I, but not C. trachomatis infection, increased the expression of Toll-like receptor 3 (TLR3), and silencing or knocking-out TLR3 prevented the synergetic effect between infection and IFN-I. Furthermore, our data support the presence of dsRNA in infected cells and the activation of the MAPK/ERK and AP-1/ATF2 signaling cascades downstream of TLR3. Taken together, our data demonstrate that IFN-I exacerbates the host inflammatory response triggered by Chlamydia by increasing TLR3 expression and activation, leading to hyperinflammation. The identified signaling cascades represent potential targets for therapeutical intervention to limit tissue damage upon Chlamydia infection.

microbiology↗

bioRxiv2024

Metabolic imprint of an intracellular pathogen drives histone hypermethylation and tunes the host transcriptional response to infection

Chlamydia trachomatis, an intracellular bacterium, highjacks metabolites from the host cell for its own proliferation. We provide evidence of global hypermethylation of the host proteome, including histones, during the late stages of infection. Single cell analyses revealed co-occurrence of several methylated residues on histones. Histone hypermethylation correlated with bacterial load and was prevented by antibiotic treatment. Mapping of trimethylation of histone 3 at residues K4 and K9 revealed a broad distribution throughout the chromatin. Nuclear fractions of infected cells exhibited a four-fold decrease of demethylase activity towards H3K4me3 and a two-fold increase in succinate concentration, a competitive inhibitor for the demethylase co-factor -ketoglutarate. Supplementation of the culture medium with dimethyl-ketoglutarate (DMKG) or with iron, a second co-factor of histone lysine demethylases, reduced histone hypermethylation. DMKG supplementation modified the transcription of about one third of the infection-responsive genes, indicating that histone hypermethylation contributes to modulating the transcriptional response of the host to infection. Finally, chemical inhibition of histone demethylases in a mouse model of infection showed a moderate benefit regarding the outcome of infection. Overall, our data show that the metabolic pressure exerted by a pathogen with an intracellular lifestyle drives epigenetic changes in infected cells.

cell biology↗

bioRxiv2024

Chlamydia-driven ISG15 expression dampens the immune response of epithelial cells independently of ISGylation

Excessive inflammation upon C. trachomatis infection can cause severe damages in the female genital tract. This obligate intracellular bacterium develops mainly in epithelial cells, whose innate response contributes to the overall inflammatory response to infection. The ubiquitin-like protein interferon-stimulated gene 15 (ISG15) stimulates interferon {gamma} (IFN{gamma}) production and is required for bacterial clearance in several infectious contexts. Here, we describe and investigate the consequences of the increase in ISG15 expression by epithelial cells infected with C. trachomatis. Infection of HeLa cells and primary ecto-cervical epithelial cells resulted in a transcriptional up-regulation of ISG15 expression. This did not involve the canonical IFN-I signaling pathway and depended instead on the activation of the STING/TBK1/IRF3 pathway. Absence or reduction of ISG15 synthesis led to increased production of several cytokines and chemokines including interleukin (IL) 6 and IL8, implicating that ISG15 normally dampens the immune response induced by C. trachomatis infection in epithelial cells. ISG15 exerted its control from an intracellular location, but without involving ISGylation. Finally, higher levels of inflammation and delayed bacterial clearance were observed in the genital tracts of ISG15-KO mice infected by C. trachomatis compared to wild type animals, however IFN{gamma} production was unchanged. Altogether, our data show that ISG15 expression acts as a brake on the immune response to C. trachomatis infection in epithelial cells and limits bacterial burden and inflammation in mice.

microbiology↗

bioRxiv2021

PI4P and BLOC-1 remodel endosomal membranes into tubules

Intracellular trafficking is mediated by transport carriers that originate by membrane remodeling from donor organelles. Tubular carriers play major roles in the flux of membrane lipids and proteins to acceptor organelles. However, how lipids and proteins impose a tubular geometry on the carriers is incompletely understood. By exploiting imaging approaches at different scales on cells and in vitro membrane systems, we show that phosphatidylinositol-4-phosphate (PI4P) and biogenesis of lysosome-related organelles complex 1 (BLOC-1) govern the formation, stability and functions of recycling endosomal tubules. Endosomal PI4P production by type II PI4-kinases is needed to form nascent curved tubules through binding of BLOC-1 that stabilize and elongate them. Membrane remodeling by the PI4P/ BLOC-1 module functions not only in the recycling of endosomal cargoes, but also in the lifecycles of intracellular pathogens such as Chlamydia bacteria and influenza virus. This study demonstrates how a phospholipid and a protein complex coordinate as a minimal machinery to remodel cellular membranes into functional tubes.

cell biology↗

bioRxiv2020

Acquisition of a type 3 secretion signal in an housekeeping enzyme shaped glycogen metabolism in Chlamydia

The obligate intracellular bacteria Chlamydia trachomatis store glycogen in the lumen of the vacuoles in which they grow. Glycogen catabolism generates glucose-1-phosphate (Glc1P), while the bacteria are capable of taking up only glucose-6-phosphate (Glc6P). We tested whether the conversion of Glc1P into Glc6P could be catalyzed by a phosphoglucomutase (PGM) of host or bacterial origin. We found no evidence for the presence of the host enzyme in the vacuole. In C. trachomatis, two proteins are potential PGMs. By reconstituting the reaction, and by complementing PGM deficient fibroblasts, we demonstrated that only CT295 displayed robust PGM activity. Furthermore, we showed that glycogen accumulation by a subset of Chlamydia species correlated with the presence of a type three secretion (T3S) signal in their PGM. In conclusion, we established that the conversion of Glc1P into Glc6P was accomplished by a bacterial PGM, through the acquisition of a T3S signal in a "housekeeping" gene.

microbiology↗

bioRxiv2019

Infection-driven activation of transglutaminase 2 boosts glucose uptake and hexosamine biosynthesis

Transglutaminase 2 (TG2) is a ubiquitous enzyme with transamidating activity. We report here that the expression and activity of TG2 are enhanced in cells infected with the obligate intracellular bacteria Chlamydia trachomatis. Genetic or pharmacological inhibition of TG2 activity impair bacterial development. We show that TG2 increases glucose import by up-regulating the transcription of the glucose transporter genes GLUT-1 and GLUT-3. Furthermore, TG2 activation drives one specific glucose-dependent pathway in the host, i.e. hexosamine biosynthesis. Mechanistically, we identify the glucosamine:fructose-6-phosphate amidotransferase (GFPT) among the substrates of TG2. GFPT modification by TG2 increases its enzymatic activity, resulting in higher levels of UDP-N-acetylglucosamine biosynthesis. As a consequence, TG2 activation results in increased protein O-GlcNAcylation. The correlation between TG2 transamidating activity and O-GlcNAcylation is disrupted in infected cells because host hexosamine biosynthesis is being exploited by the bacteria, in particular to assist their division. In conclusion, our work establishes TG2 as a key player in controlling glucose-derived metabolic pathways in mammalian cells, themselves hijacked by C. trachomatis to sustain their own metabolic needs.

microbiology↗