Fabienne Paumet1*, Jordan Wesolowski1, Alejandro Garcia-Diaz2, Cedric Delevoye3, Nathalie Aulner4, Howard A. Shuman5, Agathe Subtil6, James E. Rothman2
1 Thomas Jefferson University, Department of Microbiology and Immunology, Philadelphia, Pennsylvania, United States of America, 2 Department of Cell Biology, Yale University, New Haven, Connecticut, United States of America, 3 Institut Curie, Structure et Compartiments Membranaires, CNRS-UMR144, Paris, France, 4 Institut Pasteur, Imagopole, Batiment Monod, Paris, France, 5 Department of Microbiology, Columbia University Medical Center, New York, New York, United States of America, 6 Institut Pasteur, Unité de Biologie des Interactions Cellulaires, CNRS-URA 2582, Paris, France
Pathogens use diverse molecular machines to penetrate host cells and manipulate intracellular vesicular trafficking. Viruses employ glycoproteins, functionally and structurally similar to the SNARE proteins, to induce eukaryotic membrane fusion. Intracellular pathogens, on the other hand, need to block fusion of their infectious phagosomes with various endocytic compartments to escape from the degradative pathway. The molecular details concerning the mechanisms underlying this process are lacking. Using both an in vitro liposome fusion assay and a cellular assay, we showed that SNARE-like bacterial proteins block membrane fusion in eukaryotic cells by directly inhibiting SNARE-mediated membrane fusion. More specifically, we showed that IncA and IcmG/DotF, two SNARE-like proteins respectively expressed by Chlamydia and Legionella, inhibit the endocytic SNARE machinery. Furthermore, we identified that the SNARE-like motif present in these bacterial proteins encodes the inhibitory function. This finding suggests that SNARE-like motifs are capable of specifically manipulating membrane fusion in a wide variety of biological environments. Ultimately, this motif may have been selected during evolution because it is an efficient structural motif for modifying eukaryotic membrane fusion and thus contribute to pathogen survival.