Open AccessFusion of L egionella pneumophila outer membrane vesicles with eukaryotic membrane systems is a mechanism to deliver pathogen factors to host cell membranes
Author(s) -
Jäger Jens,
Keese Susanne,
Roessle Manfred,
Steinert Michael,
Schromm Andra B.
Publication year - 2015
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/cmi.12392
Subject(s) - biology , bacterial outer membrane , legionella pneumophila , membrane , vacuole , microbiology and biotechnology , internalization , biophysics , vesicle , cell membrane , biochemistry , cytoplasm , cell , bacteria , genetics , escherichia coli , gene
Summary The formation and release of outer membrane vesicles ( OMV s) is a phenomenon observed in many bacteria, including L egionella pneumophila . During infection, this human pathogen primarily invades alveolar macrophages and replicates within a unique membrane‐bound compartment termed L egionella ‐containing vacuole. In the current study, we analysed the membrane architecture of L . pneumophila OMV s by small‐angle X ‐ray scattering and biophysically characterized OMV membranes. We investigated the interaction of L . pneumophila OMV s with model membranes by F örster resonance energy transfer and Fourier transform infrared spectroscopy. These experiments demonstrated the incorporation of OMV membrane material into liposomes composed of different eukaryotic phospholipids, revealing an endogenous property of OMV s to fuse with eukaryotic membranes. Cellular co‐incubation experiments showed a dose‐ and time‐dependent binding of fluorophore‐labelled OMV s to macrophages. Trypan blue quenching experiments disclosed a rapid internalization of OMV s into macrophages at 37 and 4°C. Purified OMV s induced tumour necrosis factor ‐ α production in human macrophages at concentrations starting at 300 ng ml −1 . Experiments on HEK 293‐ TLR 2 and TLR 4/ MD ‐2 cell lines demonstrated a dominance of TLR 2‐dependent signalling pathways. In summary, we demonstrate binding, internalization and biological activity of L . pneumophila OMV s on human macrophages. Our data support OMV membrane fusion as a mechanism for the remote delivery of virulence factors to host cells.