Biology subjects

Pierre, P.

Publications and source records attributed to Pierre, P..

11 recordsLinked to original sources

bioRxiv2026

A hierarchical regulatory cascade defines the temporal window of natural transformation in Staphylococcus aureus

Natural transformation (NT), a major mechanism of horizontal gene transfer, promotes bacterial genome plasticity and contributes to the dissemination of antibiotic resistance. NT requires the development of competence, a transient and tightly regulated physiological state that is induced by environmental cues. Although competence has recently been demonstrated in the human pathogen Staphylococcus aureus, the regulatory architecture and temporal coordination governing its development remain poorly understood. Using a highly sensitive luciferase-based transcriptional reporter, we demonstrate that NT gene expression in S. aureus is transient, thereby defining a temporal window during which DNA uptake and recombination can occur. We further identify two classes of NT genes with distinct regulatory requirements and activation kinetics: Class I genes require both SigH and ComK1 and are activated approximately 2.5 hours later than Class II genes, which are regulated exclusively by ComK1. Mechanistically, we demonstrate that ComK1 activates sigH transcription, establishing a hierarchical regulatory cascade that explains its essential role in Class I gene expression. Finally, time-resolved transcriptomic analyses identify the global regulator CodY as an early regulator of competence that differentially controls comK1 and sigH transcription, thereby linking metabolic adaptation to competence development. Together, our findings define the regulatory architecture that governs competence development in S. aureus and reveal how a hierarchical cascade integrates environmental and metabolic cues to restrict horizontal gene transfer to a precise developmental window. This work provides a mechanistic framework for understanding how bacteria coordinate physiological adaptation with genome diversification through NT. Author summaryBacteria constantly evolve by acquiring new genetic information from their environment. One important mechanism driving this process is natural transformation, which allows bacterial cells to take up and integrate exogenous DNA into their genomes. However, this process is not continuously active: bacteria must first enter a specialized physiological state called competence. How pathogens control the development of competence remain poorly understood. In this study, we investigate how the human pathogen Staphylococcus aureus regulates natural transformation. Using a highly sensitive reporter system that allows us to monitor gene expression over time, we show that competence is activated only during a limited period, creating a defined window during which bacteria can acquire new DNA sequences. We uncover a hierarchical regulatory cascade involving the transcription factors ComK1 and SigH that controls the sequential activation of natural transformation genes. We further identify the metabolic regulator CodY as an upstream regulator that connects bacterial physiological state with the initiation of competence. Our findings reveal that natural transformation is not a random or continuous process, but a precisely timed developmental program controlled by multiple regulatory layers. By defining how S. aureus coordinates environmental sensing, metabolism, and horizontal gene transfer, this work provides new insight into how bacterial pathogens generate genetic diversity and adapt to changing environments, including conditions that may promote the emergence of antibiotic resistance.

microbiology↗

bioRxiv2026

STING dampens the unfolded protein response to enable the presentation of self-antigens on MHC-I during inflammation.

A growing body of evidence supports the contribution of the long-lasting adaptive immune system in Parkinsons disease (PD). We showed that the PD-associated protein PINK1 negatively regulates the presentation of mitochondrial antigens (MitAP) on MHC-I molecules. In vivo evidence indicated that MitAP activation in mice, in the absence of PINK1, led to cytotoxic CD8+ T cell stimulation and severe motor impairments, reversible by L-DOPA. We show here that following TLR4 activation, MitAP is engaged through a pathway involving cGAS-STING, which acts as a rheostat to dampen the unfolded protein response (UPR). Without STING, the stress response is amplified, leading to a translational attenuation that inhibits the expression of XBP1s, a transcription factor required for MitAP. STING activity also regulates the repertoire of peptides displayed at the cell surface during inflammation, highlighting a potential role in immunosurveillance. These findings establish STING and the UPR as key immune regulators targetable for therapeutic intervention during autoimmune diseases and PD.

immunology↗

bioRxiv2026

Modulating Innate Immune Responses to Curli Fibers Through Protein Engineering

Curli fibers produced by Escherichia coli are functional amyloids that activate Toll-like receptor 2 (TLR2), initiating innate immune responses at mucosal surfaces. While microbiome-derived curli contribute to host-microbe interactions, their intrinsic immunostimulatory activity limits their utility as programmable scaffolds for engineered probiotic systems, and dysregulated TLR2 activation has been linked to inflammatory bowel disease, systemic lupus erythematosus, neurodegeneration, and sepsis. Here, we engineered E. coli Nissle 1917 to produce modified curli fibers designed to inhibit TLR2 through two mechanistically distinct strategies: steric shielding via silk-elastin-like protein sequences, and direct receptor antagonism via a known TLR2 antagonist, staphylococcal superantigen-like protein 3 (SSL3). Both engineered variants assembled into structurally intact amyloid fibers and exhibited significantly reduced intrinsic TLR2-dependent NF-{kappa}B activation in reporter cells. In competitive inhibition assays against structurally diverse TLR2 agonists, the SSL3 fusion achieved near-complete inhibition maintained under rising agonist load, while steric shielding provided moderate, agonist-class-dependent inhibition. In primary human monocyte-derived dendritic cells, the SSL3 fusion robustly attenuated IL-8 secretion and transcriptional induction of IL-8, IL-6, and IL-1{beta}, whereas steric shielding produced only partial attenuation that did not translate to broad inflammatory suppression. These results establish engineered curli as a tunable platform for receptor-specific modulation of innate immune signaling and highlight the broader potential of modular microbial amyloids as programmable interfaces for engineering host-microbe interactions at mucosal surfaces. IMPORTANCEBacteria residing in the gut produce protein fibers called curli that potently activate the immune system through a receptor called Toll-like receptor 2 (TLR2). While TLR2 plays a beneficial role in maintaining gut health, its overactivation drives chronic inflammation in conditions including inflammatory bowel disease, autoimmune diseases, neurodegenerative diseases, and sepsis, and curli fibers have been directly implicated in several of these conditions. Here, we engineered curli fibers produced by the probiotic E. coli Nissle 1917 to inhibit TLR2 activation, transforming a naturally inflammatory bacterial fiber into a programmable immune modulator. We demonstrated that direct receptor antagonism, rather than steric shielding, is required for effective immune modulation in primary human immune cells, establishing a design principle for engineering bacteria-derived fibers as programmable interfaces with host immunity. The modularity of the curli scaffold positions this platform as a broader tool for programming interactions between probiotic bacteria and the mucosal immune system.

synthetic biology↗

bioRxiv2024

Distinct metabolic profiles of circulating plasmacytoid dendritic cells in systemic sclerosis patients stratified by clinical phenotypes

BackgroundPlasmacytoid dendritic cells (pDCs) play a key role in systemic sclerosis (SSc) pathophysiology. However, despite the recognised importance of metabolic reprogramming for pDC function, their metabolic profile in SSc remains to be elucidated. Thus, our study aimed to investigate the role of pDC metabolism in SSc. MethodsPeripheral blood mononuclear cells (PBMCs) were isolated from the blood of healthy donors and SSc patients. SCENITH, a single-cell flow cytometry-based method, was applied to infer the metabolic profile of circulating pDCs from patients with SSc. pDCs (CD304+ Lin-) at steady-state or stimulated with CpG A were analysed. Toll-like receptor (TLR)9 activation was confirmed by ribosomal protein S6 phosphorylation. ResultsCirculating pDCs from 10 healthy donors and 14 SSc patients were analysed. pDCs from anti-centromere antibody-positive (ACA+) patients displayed higher mitochondrial dependence and lower glycolytic capacity than those from anti-topoisomerase I antibody- positive (ATA+) patients. Furthermore, cells from both ACA+ patients and limited cutaneous SSc (lcSSc) patients showed a stronger response towards TLR9 activation than cells from ATA+, anti-RNA polymerase III antibody-positive (ARA+) or diffuse cutaneous SSc (dcSSc) patients. ConclusionsOur results show that pDCs from ACA+ patients rely more on oxidative phosphorylation (OXPHOS) and are more responsive to external stimuli, suggesting that pDCs from ATA+ patients may be more activated or exhausted. These findings point for the possible contribution of pDC metabolism to SSc clinical course, unveiling new potential targets for therapeutic approaches in SSc.

immunology↗

bioRxiv2024

Single-Nuclei Analysis of the Unfolded Protein Response (SNUPR): A Novel Method revealing bortezomib resistance mechanisms in Multiple Myeloma

AbstractThe unfolded protein response (UPR) is a key stress resistance pathway that has become a key potential target for improving the efficacy of cancer chemotherapy. The UPR involves the activation of three ER-resident stress sensors: PERK, IRE-1 and ATF6 with different signalling outcomes leading to cell death or survival. These cell-fate decisions are difficult to predict and are the result of the complex interaction of PERK, IRE-1 and ATF6 downstream events that have differences in their dynamics and their interplay. These characteristics of the UPR are still poorly defined due to lack of methods to monitor their activation simultaneously at single-cell level. We developed SNUPR (Single Nuclei analysis of the Unfolded Protein Response), an accessible technique that allows the profiling of the three UPR branches in nuclear suspensions by flow cytometry, and applied it to study UPR dynamics in a cancer-specific context. By performing transcriptomic analysis, we found that ER-stress sensor specific gene signatures correlate with patient survival in several blood malignancies, and by using SNUPR, we detected high heterogeneity during UPR activation in vitro in different human cancer cell lines, which could not be have been predicted by the level of expression of the sensors. Our SNUPR analyses further indicate that this heterogeneity is explained by variations in the intensity and duration of ER stress-induced protein synthesis inhibition via PERK, acting as upstream regulator of both the IRE-1/XBP1 and ATF6 dependent transcriptional programs. We extend the relevance of these observations by demonstrating that IRE-1/XBP1s pathway plays a critical role in bortezomib resistance of multiple myeloma cells and patients. We present here SNUPR, that can be used to monitor UPR dynamics with single-cell resolution and identified clinical contexts in which targeting a specific UPR branch could be detrimental or help circumventing chemotherapy resistance. One Sentence SummarySNUPR method enable single-cell UPR profiling and reveals the role of IRE-1 axis in predicting bortezomib resistance in multiple myeloma. HighlightsO_LISNUPR allows simultaneous profiling of PERK, IRE-1 and ATF6 activation with single- cell resolution. C_LIO_LIInhibition of protein synthesis via PERK control the activation levels of the IRE-1/XBP1s and ATF6 pathway. C_LIO_LIIRE-1 activation and associated transcriptional signatures predict the outcome of patients with multiple myeloma treated with Bortezomib. C_LIO_LIIRE-1 activity, but not PERK or ATF6, is essential to acquire bortezomib resistance in multiple myeloma cell lines. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=190 HEIGHT=200 SRC="FIGDIR/small/617161v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@297668org.highwire.dtl.DTLVardef@1cab0eorg.highwire.dtl.DTLVardef@2238b4org.highwire.dtl.DTLVardef@b8ebf6_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

Induction of the ISR by AB5 subtilase cytotoxin drives IFN-I expression in pDCs via STING activation

We demonstrate that exposure to the AB5 subtilase cytotoxin (SubAB) induces the unfolded protein response (UPR) in human peripheral blood mononuclear cells, concomitant with a pro-inflammatory response across distinct cell subsets. Notably, SubAB selectively induces type-I interferon (IFN) expression in plasmacytoid dendritic cells, acting synergistically with Toll-like receptor 7 stimulation. The induction of type-I IFN in response to SubAB relies on stimulator of interferon genes (STING) activation, coupled with protein synthesis inhibition mediated by protein kinase R-like endoplasmic reticulum kinase and phosphorylation of the eukaryotic translation initiation factor 2 subunit-alpha. By impeding mRNA translation through the integrated stress response, SubAB precipitates the downregulation of the negative innate signaling feedback regulator Tax1-binding protein 1. This downregulation is necessary to unleash TANK-binding kinase 1 signaling associated with STING activation. These findings shed new light on how UPR-inducing conditions may regulate the immune system during infection or pathogenesis.

immunology↗

bioRxiv2024

VPS34-IN1 inhibits cap-mediated translation and synergizes with STING to drive type-I IFN expression in human plasmacytoid DCs

Inhibition of the phosphatidylinositol kinase vacuolar protein sorting 34 (VPS34) with the pharmacological compound VPS34-IN1 has a range of effects on the dynamics of endosomes. While VPS34 inhibition has been suggested as a potential therapeutic approach for treating certain cancers, our findings indicate that it has minimal cytotoxic effects on leukemic blastic plasmacytoid dendritic cell neoplasms (BPDCN). VPS34-IN1, however, interferes with plasmacytoid dendritic cells (pDCs) function by blocking the recruitment of serum and glucocorticoid-regulated kinase 3 (SGK3) to endosomes, which is shown to be necessary for Toll-like receptor 7 (TLR7) signaling. In a contrasting parallel, VPS34-IN1 triggers the activation of the stimulator of interferon genes (STING) and significantly enhances pDCs response to the STING agonist 23-cyclic guanosine monophosphate-adenosine monophosphate (23-cGAMP). This cooperative action with VPS34-IN1 leads to strongly increased expression of type-I interferons (IFNs), associated with an alteration of STING degradation and importantly, inhibition of cap-mediated mRNA translation. Inhibition of protein synthesis by VPS34-IN1 appears to be central to this synergy with STING activation, notably by compromising the expression of IFIT1/ISG56, a negative regulator of innate signaling. Thus, despite their limited toxicity towards different cancer lines, inhibitors targeting VPS34 and SGK3 may present promising compounds for controlling the expression of type-I IFNs in response to various microbial stimuli and pathological contexts. One-sentence summaryPharmacological inhibition of VPS34 affects multiple signaling pathways downstream of innate immunity receptors and consequently can inhibit or potentiate type-I Interferon induction according to the danger or microbial stimuli received by plasmacytoid DCs.

immunology↗

bioRxiv2024

InteractORF, predictions of human sORF functions from an interactome study

Short open reading frames (sORFs) are widespread yet often poorly annotated, and an increasing number are known to encode functional sORF-encoded peptides (sPEPs, or microproteins). Here, we use a system approach to determine the functions of sPEPs in three tissues: monocytes, skeletal muscle and brain. We first predicted interactions between sPEPs and canonical proteins and characterized their interaction interfaces. sPEPs preferentially target specific canonical partners rather than interacting promiscuously, and two functional groups emerge from their interaction features. A small subset (~2%) exhibits canonical protein-like features, with structured domains interacting with diverse proteins involved in tissue-specific functions. In contrast, most sPEPs contain short linear motifs with extensive phosphorylation potential, suggesting they may be involved in signaling. We then constructed the first sPEP-containing interactome networks and infer sPEP functions from network topology. Most sPEPs appear to act as regulatory elements modulating diverse cellular processes rather than acting directly as functional components. Knowledge-based validations using characterized sPEPs, show that our framework can capture context-specific functions beyond current annotations. Together with their limited evolutionary constraint, the pervasive regulatory roles of sPEPs suggest that they constitute a reservoir of functional novelty and an evolutionarily flexible layer of cellular regulation.

bioinformatics↗

bioRxiv2020

MetamORF: A repository of unique short Open Reading Frames identified by both experimental and computational approaches for gene-level and meta-analysis

The development of high-throughput technologies revealed the existence of non-canonical short open reading frames (sORFs) on most eukaryotic RNAs. They are ubiquitous genetic elements highly conserved across species and suspected to be involved in numerous cellular processes. MetamORF (http://metamorf.hb.univ-amu.fr/) aims to provide a repository of unique sORFs identified in the human and mouse genomes with both experimental and computational approaches. By gathering publicly available sORF data, normalizing it and summarizing redundant information, we were able to identify a total of 1,162,675 unique sORFs. Despite the usual characterization of ORFs as short, upstream or downstream, there is currently no clear consensus regarding the definition of these categories. Thus, the data has been reprocessed using a normalized nomenclature. MetamORF enables new analyses at loci, gene, transcript and ORF levels, that should offer the possibility to address new questions regarding sORF functions in the future. The repository is available through an user-friendly web interface, allowing easy browsing, visualization, filtering over multiple criteria and export possibilities. sORFs could be searched starting from a gene, a transcript, an ORF ID, or looking in a genome area. The database content has also been made available through track hubs at UCSC Genome Browser.

bioinformatics↗

bioRxiv2020

Developmentally regulated PERK activity renders dendritic cells insensitive to subtilase cytotoxin-induced integrated stress response

In stressed cells, phosphorylation of eukaryotic initiation factor 2 (eIF2) controls transcriptome-wide changes in mRNA translation and gene expression known as the integrated stress response (ISR). We show here that dendritic cells (DCs) display unusually high eIF2 phosphorylation, which is mostly caused by a developmentally regulated activation of the ER kinase PERK (EIF2AK3). Despite high p-eIF2 levels, differentiated DCs display active protein synthesis and no signs of a chronic ISR. eIF2 phosphorylation does not majorly impact DC differentiation nor cytokines production. It is however important to adapt protein homeostasis to the variations imposed on DCs by the immune or physiological contexts. This biochemical specificity prevents translation arrest and expression of the transcription factor ATF4 during ER-stress induction by subtilase cytotoxin or upon DC stimulation with bacterial lipopolysaccharides. This is also exemplified by the influence of the actin cytoskeleton dynamics on eIF2 phosphorylation and the migratory deficit observed in PERK-deficient DCs.

immunology↗

bioRxiv2017

The RAG transposon is active through the deuterostome evolution and domesticated in jawed vertebrates.

RAG1 and RAG2 are essential subunits of the V(D)J recombinase required for the generation of the variability of antibodies and T-cell receptors in jawed vertebrates. It was demonstrated that the amphioxus homologue of RAG1-RAG2 is encoded in an active transposon, belonging to the transposase DDE superfamily. The data provided supports to the possibility that the RAG transposon has been active through the deuterostome evolution and is still active in several lineages. The RAG transposon corresponds to several families present in deuterostomes. RAG1-RAG2 V(D)J recombinase evolved from one of them, partially due to the new ability of the transposon to interact with the cellular reparation machinery. Considering the fact that the RAG transposon survived millions of years in many different lineages, in multiple copies, and that DDE transposases evolved their association with proteins involved in repair mechanisms, we propose that the apparition of V(D)J recombination machinery could be a predictable genetic event.

immunology↗