Pseudomonas aeruginosa lectin LecB inhibits tissue repair processes by triggering β-catenin degradation

AbstractPseudomonas aeruginosa is an opportunistic pathogen that induces severe lung infections such as ventilator-associated pneumonia and acute lung injury. Under these conditions, the bacterium diminishes epithelial integrity and inhibits tissue repair mechanisms, leading to persistent infections. Understanding the involved bacterial virulence factors and their mode of action is essential for the development of new therapeutic approaches.In our study we discovered a so far unknown effect of the P. aeruginosa lectin LecB on host cell physiology. LecB alone was sufficient to attenuate migration and proliferation of human lung epithelial cells and to induce transcriptional activity of NF-κB. These effects are characteristic of impaired tissue repair. Moreover, we found a strong degradation of β-catenin, which was partially recovered by the proteasome inhibitor lactacystin. In addition, LecB induced loss of cell–cell contacts and reduced expression of the β-catenin targets c-myc and cyclin D1. Blocking of LecB binding to host cell plasma membrane receptors by soluble l-fucose prevented these changes in host cell behavior and signaling, and thereby provides a powerful strategy to suppress LecB function.Our findings suggest that P. aeruginosa employs LecB as a virulence factor to induce β-catenin degradation, which then represses processes that are directly linked to tissue recovery

Lectin-mediated protocell crosslinking to mimic cell-cell junctions and adhesion

International audienceCell adhesion is a crucial feature of all multicellular organisms, as it allows cells to organise themselves into tissues to carry out specific functions. Here, we present a mimetic approach that uses multivalent lectins with opposing binding sites to crosslink glycan-functionalised giant unilamellar vesicles. The crosslinking process drives the progression from contact puncta into elongated protocellular junctions, which form the vesicles into polygonal clusters resembling tissues. Due to their carbohydrate specificity, different lectins can be engaged in parallel with both natural and synthetic glycoconjugates to generate complex interfaces with distinct lectin domains. In addition, the formation of protocellular junctions can be combined with adhesion to a functionalised support by other ligand-receptor interactions to render increased stability against fluid flow. Furthermore, we consider that adhesion is a complex process of attraction and repulsion by doping the vesicles with a PEG-modified lipid, and demonstrate a dosedependent decrease of lectin binding and formation of protocellular junctions. We suggest that the engineering of prototissues through lectin-glycan interactions is an important step towards synthetic minimal tissues and in designing artificial systems to reconstruct the fundamental functions of biology

Signalling to the nucleus under the control of light and small molecules

One major regulatory mechanism in cell signalling is the spatiotemporal control of the localization of signalling molecules. We synthetically designed an entire cell signalling pathway, which allows controlling the transport of signalling molecules from the plasma membrane to the nucleus, by using light and small molecules

GUV-AP: multifunctional FIJI-based tool for quantitative image analysis of Giant Unilamellar Vesicles

MOTIVATION: Giant Unilamellar Vesicles (GUVs) are widely used synthetic membrane systems that mimic native membranes and cellular processes. Various fluorescence imaging techniques can be employed for their characterization. In order to guarantee a fast and unbiased analysis of imaging data, the development of automated recognition and processing steps is required. RESULTS: We developed a fast and versatile Fiji-based macro for the analysis of digital microscopy images of GUVs. This macro was designed to investigate membrane dye incorporation and protein binding to membranes. Moreover, we propose a fluorescence intensity-based method to quantitatively assess protein binding. AVAILABILITY AND IMPLEMENTATION: The ImageJ distribution package FIJI is freely available online: https://imagej.net/Fiji. The macro file GUV-AP.ijm is available at https://github.com/AG-Roemer/GUV-AP. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online

Uptake of Marasmius oreades agglutinin disrupts integrin-dependent cell adhesion

Background Fruiting body lectins have been proposed to act as effector proteins in the defense of fungi against parasites and predators. The Marasmius oreades agglutinin (MOA) is a lectin from the fairy ring mushroom with specificity for Galα1-3Gal containing carbohydrates. This lectin is composed of an N-terminal carbohydrate-binding domain and a C-terminal dimerization domain. The dimerization domain of MOA shows in addition calcium-dependent cysteine protease activity, similar to the calpain family. Methods Cell detachment assay, cell viability assay, immunofluorescence, live cell imaging and Western blot using MDCKII cell line. Results In this study, we demonstrate in MDCKII cells that after internalization, MOA protease activity induces profound physiological cellular responses, like cytoskeleton rearrangement, cell detachment and cell death. These changes are preceded by a decrease in FAK phosphorylation and an internalization and degradation of β1-integrin, consistent with a disruption of integrin-dependent cell adhesion signaling. Once internalized, MOA accumulates in late endosomal compartments. Conclusion Our results suggest a possible toxic mechanism of MOA, which consists of disturbing the cell adhesion and the cell viability. General significance After being ingested by a predator, MOA might exert a protective role by diminishing host cell integrity.ISSN:0304-4165ISSN:1872-800

Cationic amphipathic peptides accumulate sialylated proteins and lipids in the plasma membrane of eukaryotic host cells

Cationic antimicrobial peptides (CAMPs) selectively target bacterial membranes by electrostatic interactions with negatively charged lipids. It turned out that for inhibition of microbial growth a high CAMP membrane concentration is required, which can be realized by the incorporation of hydrophobic groups within the peptide. Increasing hydrophobicity, however, reduces the CAMP selectivity for bacterial over eukaryotic host membranes, thereby causing the risk of detrimental side-effects. In this study we addressed how cationic amphipathic peptides—in particular a CAMP with Lysine–Leucine–Lysine repeats (termed KLK)—affect the localization and dynamics of molecules in eukaryotic membranes. We found KLK to selectively inhibit the endocytosis of a subgroup of membrane proteins and lipids by electrostatically interacting with negatively charged sialic acid moieties. Ultrastructural characterization revealed the formation of membrane invaginations representing fission or fusion intermediates, in which the sialylated proteins and lipids were immobilized. Experiments on structurally different cationic amphipathic peptides (KLK, 6-MO-LF11-322 and NK14-2) indicated a cooperation of electrostatic and hydrophobic forces that selectively arrest sialylated membrane constituents