Biology subjects

Foti, A.

Publications and source records attributed to Foti, A..

5 recordsLinked to original sources

bioRxiv2026

Lipid chlorination mobilizes Neutrophil Elastase to initiate NETosis

Neutrophils are the first cells recruited to sites of infection, where they contain and kill pathogens through phagocytosis, degranulation, and the release of neutrophil extracellular traps (NETs) - web-like structures of decondensed chromatin that trap and destroy microbes. NET formation is essential for host defense, but when dysregulated it also contributes to disease, including sepsis, autoimmunity, and thrombosis. A central step in NET release is the translocation of neutrophil elastase (NE) from azurophilic granules to the nucleus, yet how NE crosses the granule membrane has remained unresolved. Using neutrophils and granules from healthy donors and from patients deficient in NADPH oxidase or myeloperoxidase (MPO), we show that MPO-derived hypochlorous acid chlorinates plasmalogens abundant in the granule membrane, generating 2-chlorofatty acids that permeabilize the granule and release NE into the cytosol. This reaction requires chloride, occurs within transient intracellular oxidant-rich compartments, and is both necessary and sufficient to trigger NE mobilization and NET formation. These findings identify lipid chlorination as the chemical link between the neutrophil oxidative burst and the execution of NETosis.

immunology↗

bioRxiv2026

A newly identified detoxification system protects uropathogenic Escherichia coli from reactive chlorine species

Neutrophils eliminate invading pathogens through the production of reactive oxygen and chlorine species (ROS/RCS), with hypochlorous acid (HOCl) representing the most abundant and bactericidal oxidant produced in this process. Compared to bacterial defenses against ROS, which are well studied, little is known about how pathogens respond to and counter RCS, including HOCl. Here, we identify and mechanistically characterize RcrB, a protein of the uncharacterized DUF417 protein family, for which no role in oxidative stress defense has been described yet. We report a previously unrecognized role as an RCS detoxification system that confers high-level resistance to uropathogenic Escherichia coli (UPEC). We show that RcrB is an inner membrane protein and strongly induced during RCS exposure and phagocytosis. Loss of RcrB results in profound HOCl hypersensitivity, accompanied by elevated macromolecular damage and severe metabolic perturbations, establishing RcrB as a central determinant of UPECs RCS stress resistance. Heterologous expression of RcrB in HOCl-sensitive intestinal E. coli strains is sufficient to restore resistance but requires functional glutathione biosynthesis. Quantitative HOCl trapping assays demonstrate that RcrB expression protects the bacterial population by significantly reducing extracellular HOCl, indicating active chemical quenching rather than passive membrane protection. Structure-function analysis of RcrB confirms this conclusion and demonstrate that conserved, redox-active amino acids facing the periplasm are essential for its detoxification activity. In summary, our study reveals a hitherto unknown bacterial strategy for mitigating RCS and reveal a distinct mechanism by which UPEC may survive the mammalian host defense. Significance StatementDuring infection, human immune cells such as neutrophils kill bacteria by releasing powerful oxidants, including hypochlorous acid (HOCl), the active ingredient of household bleach. How pathogenic bacteria survive this chemical attack is still poorly understood. This study identifies a membrane protein in uropathogenic Escherichia coli as a key defense factor that neutralizes HOCl before it can damage the cell. RcrB acts at the bacterial cell envelope, where it detoxifies HOCl in a glutathione-dependent manner to maintain a balanced redox homeostasis and cellular integrity, thereby even protect neighboring bacteria. These findings reveal a previously unrecognized frontline defense strategy that helps pathogens survive immune attack and may represent a new target for antimicrobial therapies.

microbiology↗

bioRxiv2024

SOD1 controls neutrophil oxidative burst and microbial killing

AbstractNeutrophils are immune cells specialized in producing large amounts of reactive oxygen species (ROS) to kill microbes. However, the mechanisms by which these cells regulate the balance of different ROS species and mitigate oxidative stress remain unclear. Here, we demonstrate that superoxide dismutase 1 (SOD1) plays a crucial role in ROS formation and antimicrobial activity in neutrophils. Our findings reveal that SOD1 modulates the ratio of superoxide (O2-) to hydrogen peroxide (H2O2) during the ROS burst, thereby supporting myeloperoxidase (MPO) enzymatic activity. By employing biochemical, cell biological, and genetic approaches, we show that SOD1 is crucial for ROS formation during NETosis and microbial infections, as it reduces oxidative stress and enables complete neutrophil activation. Impairment of SOD1 activity increases cysteine oxidation and lipid peroxidation. Neutrophils isolated from a patient with a SOD1 mutation exhibit decreased ROS production and impaired neutrophil extracellular trap (NET) formation. Our findings suggest that SOD1 is a novel regulatory factor in the oxidative burst that enables the full immunological response of neutrophils.

immunology↗

bioRxiv2023

Myeloperoxidase-dependent tyrosine halogenation potentiates alpha-defensins functions

Neutrophils are immune cells that eliminate microbes using a powerful arsenal of reactive oxygen species, hypohalous acids, proteases, and antimicrobial peptides -- yet how these cytotoxic effectors act in concert remains poorly understood. Here, we identify an unrecognized synergy between oxidative and non-oxidative neutrophil defenses. We show that myeloperoxidase-derived hypohalous acids selectively halogenate -defensins (HNP1-3) at conserved tyrosine residues. This post-translational modification occurs in both human and rat neutrophils and is prominent in diseases marked by neutrophil-rich inflammation, including cystic fibrosis, bacterial pneumonia, and Staphylococcus aureus abscesses. Halogenation increases HNP1 hydrophobicity without altering its structure, reprogramming these peptides into potent immunomodulatory mediators. Using single-cell transcriptomics and a in vivo peritonitis model, we demonstrate that halogenated HNP1s amplify immune signaling. Our analysis of the human haloproteome reveals a novel oxidative mechanism by which hypohalous acids rewire immune protein functions, uncovering an unexpected layer of cooperation between neutrophil effector systems. The discovery of halogenated HNP1s represents, to our knowledge, the first characterization of a protein halogenation that has biologically significance in human immunity.

biochemistry↗

bioRxiv2021

Redox-mediated inactivation of the transcriptional repressor C3600 makes uropathogenic Escherichia coli exquisitely resistant to reactive chlorine species

The ability to overcome stressful environments is critical for pathogen survival in the host. One challenge for bacteria is the exposure to reactive chlorine species (RCS), which are generated by innate immune cells as critical part of the oxidative burst. Hypochlorous acid (HOCl) is the most potent antimicrobial RCS and associated with extensive macromolecular damage in the phagocytized pathogen. However, bacteria have evolved defense strategies to alleviate the effects of HOCl-mediated damage. Among these are RCS-sensing transcriptional regulators that control the expression of HOCl-protective genes under non- and HOCl stress. Uropathogenic Escherichia coli (UPEC), the major causative agent of urinary tract infections (UTIs), is particularly exposed to infiltrating neutrophils during pathogenesis, however, their responses to and defenses of HOCl are still completely unexplored. Here, we present evidence that UPEC strains tolerate higher levels of HOCl and are better protected from neutrophil-mediated killing compared to other E. coli. Transcriptomic analysis of HOCl-stressed UPEC revealed the upregulation of an operon consisting of three genes, one of which encodes the transcriptional regulator C3600. We identified C3600 as a HOCl-sensing transcriptional repressor, which, under non-stress conditions, is bound to the operator and represses the expression of its target genes. During HOCl exposure, however, the repressor forms reversible intermolecular disulfide bonds and dissociates from the DNA resulting in the de-repression of the operon. Deletion of one of the target genes renders UPEC significantly more susceptible to HOCl indicating that the HOCl-mediated induction of the regulon plays a major role for UPECs HOCl resistance. IMPORTANCEHow do pathogens deal with antimicrobial oxidants produced by the innate immune system during infection? Uropathogenic Escherichia coli (UPEC), the most common etiological agent of urinary tract infections (UTIs), is particularly exposed to infiltrating neutrophils and, therefore, must counter elevated levels of the antimicrobial oxidant HOCl to establish infection. Our study provides fundamentally new insights into a defense mechanism that enables UPEC to fend off the toxic effects of HOCl stress. Intriguingly, the defense system is predominantly found in UPEC and absent in non-invasive enteropathogenic E. coli. Our data suggest that expression of the target gene c3601 is exclusively responsible for UPECs increased HOCl tolerance in culture and therefore potentially contributes to UPECs survival during phagocytosis. Thus, this novel HOCl stress defense system could potentially serve as an attractive drug target to increase the bodys own capacity to fight UTIs.

microbiology↗