Biology subjects

Vergnes, A.

Publications and source records attributed to Vergnes, A..

4 recordsLinked to original sources

bioRxiv2024

Maintaining the methionine residues of the chaperone Spy in a reduced state is crucial for periplasmic proteostasis.

The bacterial cell envelope is exposed to various stresses, including oxidative stress caused by different types of oxidants, such as reactive oxygen species (ROS) and reactive chlorine species (RCS). In E. coli, the reduction of chlorate into chlorite, a toxic RCS compound, induces the expression of the MsrPQ system, which repairs periplasmic proteins oxidized at methionine residues (methionine sulfoxide, Met-O). In this study, using a proteomic-based approach, we show that chlorite stress also triggers the overproduction of the periplasmic chaperone Spy. This response is mediated by the activation of the BaeSR two-component system. Furthermore, both in vivo and in vitro evidence reveal that Spys susceptibility to oxidation is critical for its chaperone activity. We demonstrate that the MsrPQ repair system ensures Spys functionality by reducing its Met-O, thereby safeguarding its role in periplasmic protein homeostasis. Overall, this work reveals Spy as a key target of chlorite-induced oxidative damage and underscores the essential role of MsrPQ in preserving periplasmic protein quality control.

microbiology↗

bioRxiv2022

Periplasmic oxidized-protein repair during copper stress in E. coli: a focus on the metallochaperone CusF.

Methionine residues are particularly sensitive to oxidation by reactive oxygen or chlorine species (ROS/RCS), leading to the appearance of methionine sulfoxide in proteins. This post-translational oxidation can be reversed by omnipresent protein repair pathways involving methionine sulfoxide reductases (Msr). In the periplasm of Escherichia coli, the enzymatic system MsrPQ, whose expression is triggered by the RCS, controls the redox status of methionine residues. Here we report that MsrPQ synthesis is also induced by copper stress via the CusSR two-component system, and that MsrPQ plays a role in copper homeostasis by maintaining the activity of the copper efflux pump, CusCFBA. Genetic and biochemical evidence suggest the metallochaperone CusF is the substrate of MsrPQ and our study reveal that CusF methionines are redox sensitive and can be restored by MsrPQ. Thus, the evolution of a CusSR-dependent synthesis of MsrPQ allows keeping copper homeostasis under aerobic conditions by maintenance of the reduced state of Met residues in copper-trafficking proteins. AUTHOR SUMMARYOur study investigates the interconnection between the copper stress response and the methionine redox homeostasis in the Gram-negative bacterium Escherichia coli. We report that the copper-activation of the CusSR two-component system induces the expression of the periplasmic oxidized-protein repair system, MsrPQ. We demonstrate that MsrPQ is crucial for CusCFBA copper efflux pump activity under aerobic conditions as it maintains the periplasmic component CusF in its functional reduced form. Methionine emerges as a critical residue in copper trafficking proteins: however this naturally-selected advantage must be balanced by methionines high susceptibility to oxidation. Therefore the induction of MsrPQ by copper allows copper homeostasis under aerobic conditions, illustrating that E. coli has developed an integrated and dynamic circuit for sensing and counteracting stress caused by copper and oxidants, thus allowing bacteria to adapt to host cellular defences.

microbiology↗

bioRxiv2021

HypVW is an HOCl-Sensing Two Component System in Escherichia coli

Two component systems (TCS) are signalling pathways that allow bacterial cells to sense, respond and adapt to fluctuating environments. Among the classical TCS of Escherichia coli, YedVW has been recently showed to be involved in the regulation of msrPQ, encoding for the periplasmic methionine sulfoxide reductase system. In this study, we demonstrate that hypochlorous acid (HOCl) induces the expression of msrPQ in a YedVW dependant manner, whereas H2O2, NO and paraquat (a superoxide generator) do not. Therefore, YedV appears to be an HOCl-sensing histidine kinase. Based on this finding, we proposed to rename this system HypVW. Moreover, using a directed mutagenesis approach, we show that Met residues located in the periplasmic loop of HypV (formerly YedV) are important for its activity. Given that HOCl oxidizes preferentially Met residues, we bring evidences that HypV could be activated via the reversible oxidation of its methionine residues, thus conferring to MsrPQ a role in switching HypVW off. Based on these results, we propose that the activation of HypV by HOCl could occur through a Met redox switch. HypVW appears to be the first characterized TCS able to detect HOCl in E. coli. This study represents an important step in understanding the mechanisms of reactive chlorine species resistance in prokaryotes. IMPORTANCEUnderstanding molecularly how bacteria respond to oxidative stress is crucial to fight pathogens. HOCl is one of the most potent industrial and physiological microbiocidal oxidant. Therefore, bacteria have developed counterstrategies to survive HOCl-induced stress. Over the last decade, important insights into these bacterial protection factors have been obtained. Our work establishes HypVW as an HOCl-sensing two component system in Escherichia coli MG1655 which regulates the expression of the periplasmic HOCl-oxidized proteins repair system MsrPQ. Moreover we bring evidences suggesting that HOCl could activate HypV through a methionine redox switch.

microbiology↗

bioRxiv2019

Segregation of floricolous ants along latitudinal and urbanization gradients

Recent call has been made to study the biogeography of species interactions in order to better understand ecosystems states and processes, as well as their response to global anthropogenic disturbances. Ants (Formicidae) are a dominant group of arthropods with a central role in ecosystem functioning. Many ant species, those feeding on liquids, are floricolous and consume nectar. The biogeography of ant-flower interactions is still poorly studied and especially in temperate area. Here we quantify variations in ant-flower interaction frequency in response to latitudinal and urbanization gradients at a country scale.\n\nWe used data from a flower-visitor monitoring program that includes pictures on 2511 flower plants across Continental France (Mainland) and over 4 years. We analysed the occurrence of the ant-flower interactions along two gradients: latitude and urbanization, this for 10 ant taxa corresponding to different taxonomical level (from family to species).\n\nAnts visited 26 % of the sampled plants. Most of the observed ant-flower interaction involved the subfamily Formicinae (82.1 %), followed by Myrmicinae and Dolichoderinae (6.9 % and 4.6 % respectively). Globally, (i) the probability of occurrence was negatively related to latitudes (ii) and to urbanization at lower latitude. (iii) Responses to latitude among sub families, genus and species level responses were segregated and taxonomically aggregated.\n\nAt lower taxonomic levels we found clear latitudinal niche partitioning among ant taxa suggesting that competition, on both evolutionary and ecological time scales, is a major process structuring ant communities. Finally, our results highlight that the effects of large scale perturbation like urbanization can vary and affect latitudinal gradient.

ecology↗