Biology subjects

Quinton, L.

Publications and source records attributed to Quinton, L..

10 recordsLinked to original sources

bioRxiv2026

Recombinant Echis disintegrins reveal distinct inhibitory profiles on platelet aggregation and endothelial cell migration

Disintegrins are snake venom toxins that bind integrins and modulate platelet aggregation and cell migration. Isolation from venom often yields insufficient quantities for comprehensive study, making recombinant expression essential for detailed toxin characterisation. Here, we produced and characterised four disintegrins from Echis coloratus and Echis ocellatus in Escherichia coli. These homologous proteins contain distinct integrin-binding motifs: EcDis_RGD, EoDis_RGD, EcDis_KGD, and EcDis_VGD. Functional activities were evaluated using human platelet aggregation and endothelial cell scratch wound-healing assays. RGD-containing disintegrins exhibited the strongest inhibition of platelet aggregation, with EcDis_RGD showing the highest potency. The EcDis_KGD disintegrin inhibited platelet aggregation less potently, whereas EcDis_VGD showed no detectable activity in our assays. In endothelial cells, EcDis_RGD disintegrin markedly impaired cell migration, while EoDis_RGD displayed weaker anti-migratory activity. Neither KGD- nor VGD-containing disintegrins significantly affected wound closure. EoDis_RGD exhibited similar antiplatelet activity to the native, venom-purified disintegrin ocellatusin, validating our recombinant expression strategy. However, the corresponding PII-SVMP preparation displayed reduced inhibitory activity, consistent with incomplete generation of fully mature disintegrins species. Our findings demonstrate the importance of both integrin-binding motif identity and surrounding sequence context in determining disintegrin function, and support further use of recombinant toxins in toxinology and as therapeutic lead molecules.

biochemistry↗

bioRxiv2026

Local conformational plasticity underlies ligand recognition and 1 proton coupling in MFS multidrug transporters

Polyspecific substrate recognition drives multidrug efflux and antibiotic resistance, yet its molecular basis remains unclear. Here, we use HDX-MS to compare ligand-dependent local dynamics in three multidrug efflux pumps: NorA, QacA and LmrP. In the apo state, all three display high flexibility in specific transmembrane helices, unlike homologous transporters with narrow substrate profiles. Substrate binding remodels these flexible regions, but in a transporter-specific manner, revealing divergent local adaptations within a conserved fold. In LmrP, protonation-mimicking mutation of a conserved acidic residue recapitulates the substrate-induced dynamic changes, supporting a model in which transmembrane helix flexibility couples protonation and substrate binding to the conformational changes required for transport. Together, our study identifies local plasticity beyond what is captured by static high-resolution structures, as an overlooked feature of polyspecific ligand recognition.

biochemistry↗

bioRxiv2025

Neutrophils respond with pathogen-specific defenses during bacterial pneumonia

Neutrophils have historically been envisioned as a homogenous population of short-lived innate immune cells that migrate to sites of infection, kill pathogens, and die. Recent work, including studies in pneumonia models, has shown that neutrophil transcriptomes reflect the environment from which they were isolated. We used high-parameter spectral flow cytometry to compare and contrast a wide array of surface proteins on neutrophils from different tissues, infections, host age, pathogen virulence, and across multiple time-points of pneumonia. Circulating and airspace neutrophils consistently differed, and surface protein phenotypes unique to each infection setting were identified, revealing tissue-specific and microbe-specific neutrophil plasticity. Phenotypic differences in circulating neutrophils from mice infected with different pathogens (E. coli, S. pneumoniae, S. aureus, and P. aeruginosa) identified, even in the absence of bacteremia. Neutrophil activation state was diminished with less virulent pathogens and host age. In the airspace, VISTA, CD200R, and PD-L1 were selectively high on BAL neutrophils (BALN) during S. pneumoniae infection, and we identified pro-degranulation-like (CD88High VISTAHigh PD-L1+ CD101-) neutrophils in S. pneumoniae and pro-phagocytosis-like (CD101+ CD18Low PD-L1-) neutrophils in E. coli infections. Stimulation of VISTA with its ligand VISG-3 enhanced the neutrophil respiratory burst, degranulation, and killing of S. pneumoniae but not E. coli. We conclude that neutrophil cell surface protein expression depends on anatomic location and infection type, resulting in pathogen-specific neutrophil-mediated immune defense in discreet areas of the pneumonic lung. Graphical AbstractIn brief, Pihl et al. have found that neutrophil cell surface phenotype varies drastically based on tissue, time post-infection, and infection. BALN from early infections have higher activation and maturation statuses, while blood neutrophils are more migration primed, and late infections have more immune-suppressive and altered pathogen killing statuses. Neutrophil phenotype is skewed towards pro-phagocytosis associated marker expression on BALN from E. coli-infected mice while S. pneumoniae results in a pro-degranulation phenotype. In vitro BMN stimulation of VISTA with VSIG-3 results in degranulation, respiratory burst, and pathogen specific killing of S. pneumoniae but not E. coli. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/649365v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@4e4829org.highwire.dtl.DTLVardef@1638108org.highwire.dtl.DTLVardef@1ac413dorg.highwire.dtl.DTLVardef@1ef36b5_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

Nitrogen sources enhance siderophore-mediated competition for iron between potato common scab and late blight causative agents

Withdrawal StatementThe authors have withdrawn their manuscript owing to the fact that the P. infestans strain received from third parties is not the one referred in the manuscript despite having the certificate from the providing collection. All the experiments and data are correct but not included into a proper research context. A new version of this work will be published in near future. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

microbiology↗

bioRxiv2023

The fate of bacterial secondary metabolites in the rhizosphere: Streptomyces degrades and feeds on cyclic lipopeptides produced by competitors

Cyclic lipopeptides are key bioactive secondary metabolites produced by some plant beneficial rhizobacteria such as Pseudomonas and Bacillus. They exhibit antimicrobial properties, promote induced systemic resistance in plants and support key developmental traits including motility, biofilm formation and root colonization. However, our knowledge about the fate of lipopeptides once released in the environment and especially upon contact with neighboring rhizobacteria remains limited. Here, we investigated the enzymatic degradation of Bacillus and Pseudomonas cyclic lipopeptides by Streptomyces venezuelae. We observed that Streptomyces is able to degrade the three lipopeptides surfactin, iturin and fengycin upon confrontation with of B. velezensis in vitro and in planta according to specific mechanisms. S. venezuelae was also able to degrade the structurally diverse sessilin, tolaasin, orfamide, xantholisin and putisolvin-type lipopeptides produced by Pseudomonas, indicating that this trait is likely engage in the interaction with various competitors.Furthermore, the degradation of CLPs is associated with the release of free amino and fatty acids and was found to enhance Streptomyces growth, indicating a possible nutritional utilization. Thereby, this work stresses on how the enzymatic arsenal of S. venezuelae may contribute to its adaptation to BSMs-driven interactions with microbial competitors. The ability of Streptomyces to degrade exogenous lipopeptides and feed on them adds a new facet to the implications of the degradation of those compounds by Streptomyces, where linearization of surfactin was previously reported as a detoxification mechanism. Additionally, we hypothesize that lipopeptide-producing rhizobacteria and their biocontrol potential are impacted by the degradation of their lipopeptides as observed with the polarized motility of B. velezensis, avoiding the confrontation zone with Streptomyces and the loss of antifungal properties of degraded iturin. This work illustrates how CLPs, once released in the environment, may rapidly be remodeled or degraded by members of the bacterial community, with potential impacts on CLP-producing rhizobacteria and the biocontrol products derived from them.

microbiology↗

bioRxiv2023

Exploring the phytobeneficial and biocontrol capacities of endophytic bacteria isolated from hybrid vanilla pods

Few studies have been conducted on endophytic bacteria of vanilla. In this study, 58 bacterial strains were isolated from two hybrid vanilla plants from Madagascar, Manitra ampotony and Tsy taitra. They were genetically characterised and divided into four distinct phylotypes. A selection of twelve strains corresponding to the identified genetic diversity were tested in vitro for four phytobeneficial capacities: phosphate solubilisation, free nitrogen fixation, phytohormone and siderophore production. They were also evaluated in vitro for their ability to biocontrol the growth of the vanilla pathogenic fungi, Fusarium oxysporum f. sp. radicis vanillae and Cholletotrichum orchidophilum. Bacteria belonging to three different phyla were found to be highly competent in each of the phytobeneficial capacities tested. Bacteria belonging to the phylum related to Bacillus siamensis showed the best capacity to inhibit fungal growth making them good candidates for controlling fungal diseases of vanilla. This competence was highlighted with spectral imaging showing the production of lipopeptides by the bacterial strains confronted with the pathogenic fungi of vanilla.

microbiology↗

bioRxiv2022

Grapevine leaf MALDI-MS imaging reveals the localisation of a putatively identified sucrose metabolite associated to Plasmopara viticola development

Despite well-established pathways and metabolites involved in grapevine-Plasmopara viticola interaction, information on the molecules involved in the first moments of pathogen contact with the leaf surface and their specific location is still missing. To understand and localise these molecules, we analysed grapevine leaf discs infected with P. viticola with MSI. Plant material preparation was optimised, and different matrices and solvents were tested. Our data shows that trichomes hamper matrix deposition and the ion signal. Results show that putatively identified sucrose presents a higher accumulation and a non-homogeneous distribution in the infected leaf discs in comparison with the controls. This accumulation was mainly on the veins, leading to the hypothesis that sucrose metabolism is being manipulated by the development structures of P. viticola. Up to our knowledge this is the first time that the localisation of a putatively identified sucrose metabolite was shown to be associated to P. viticola infection sites.

plant biology↗

bioRxiv2020

Mechanism of cellular production and in vivo seeding effects of hexameric β-amyloid assemblies

BackgroundThe {beta}-amyloid peptide (A{beta}) plays a key role in Alzheimers disease. After its production by catabolism of the amyloid precursor protein (APP) through the action of presenilin 1 (PS1)- or presenilin 2 (PS2)-dependent {gamma}-secretases, monomeric A{beta} can assemble in oligomers. In a pathological context, this eventually leads to the formation of fibrils, which deposit in senile plaques. Many studies suggest that A{beta} toxicity is related to its soluble oligomeric intermediates. Among these, our interest focuses on hexameric A{beta}, which acts as a nucleus for A{beta} self-assembly. MethodsBiochemical analyses were used to identify hexameric A{beta} in a wide range of models; cell lines, cerebrospinal fluid from cognitively impaired patients and transgenic mice exhibiting human A{beta} pathology (5xFAD). We isolated this assembly and assessed both its effect on primary neuron viability in vitro, and its contribution to amyloid deposition in vivo following intracerebral injection. In both cases, we used wild-type mice (C57BL/6) to mimic an environment where hexameric A{beta} is present alone and 5xFAD mice to incubate hexameric A{beta} in a context where human A{beta} species are pre-existing. Using CRISPR-Cas9, we produced stable knockdown human cell lines for either PS1 or PS2 to elucidate their contribution to the formation of hexameric A{beta}. ResultsIn WT mice, we found that neither in vitro or in vivo exposure to hexameric A{beta} was sufficient to induce cytotoxic effects or amyloid deposition. In 5xFAD mice, we observed a significant increase in neuronal death in vitro following exposure to 5M hexameric A{beta}, as well as a 1.47-fold aggravation of amyloid deposition in vivo. At the cellular level, we found hexameric A{beta} in extracellular vesicles and observed a strong decrease in its excretion when PS2 was knocked down by 60%. ConclusionsOur results indicate the absence of cytotoxic effects of cell-derived hexameric A{beta} by itself, but its capacity to aggravate amyloid deposition by seeding other A{beta} species. We propose an important role for PS2 in the formation of this particular assembly in vesicular entities, in line with previous reports linking the restricted location of PS2 in acidic compartments to the production of more aggregation-prone A{beta}.

neuroscience↗

bioRxiv2020

Cell-derived hexameric β-amyloid: a novel insight into composition, self-assembly and nucleating properties

A key hallmark of Alzheimers disease (AD) is the extracellular deposition of amyloid plaques composed primarily of the amyloidogenic amyloid-{beta} (A{beta}) peptide. The A{beta} peptide is a product of sequential cleavage of the Amyloid Precursor Protein (APP), the first step of which gives rise to a C-terminal Fragment (C99). Cleavage of C99 by {gamma}-secretase activity releases A{beta} of several lengths and the A{beta}42 isoform in particular has been identified as being neurotoxic. The misfolding of A{beta} leads to subsequent amyloid fibril formation by nucleated polymerisation. This requires an initial and critical nucleus for self-assembly. Here, we identify and characterise the composition and self-assembly properties of cell-derived hexameric A{beta}42 and show its nucleating properties which are dependent on the A{beta} monomer availability. Identification of nucleating assemblies that contribute to self-assembly in this way may serve as therapeutic targets to prevent the formation of toxic oligomers.

biochemistry↗

bioRxiv2020

Multidisciplinary Interrogation of a Crucial Protein Interface in the Type II Secretion System

The type IV filament superfamily comprises widespread membrane-associated polymers in prokaryotes. The Type II secretion system (T2SS), a significant virulence pathway in many pathogens, belongs to this superfamily. A knowledge gap in the understanding of the T2SS is the molecular role of a small pseudopilin protein. Using multiple biophysical techniques, we have deciphered how this missing component of the Xcp T2SS architecture is structurally integrated, and thereby also unlocked its function. We demonstrate that the low abundance XcpH is the adapter that bridges a trimeric initiating tip complex XcpIJK with a periplasmic filament of XcpG subunits. Our model reveals that each pseudopilin protein caps an XcpG protofilament in an overall pseudopilus compatible with the dimensions of the periplasm and the outer membrane-spanning secretin through which substrates of the T2SS pass. Unexpectedly, to fulfill its adapter function, the XcpH N-terminal helix must be unwound, a property shared with the XcpG subunits. We provide the first complete structural model of a type IV filament, a result immediately transferable to understanding of other T2SS and the type IV pili.

microbiology↗