title: Pasteurella multocida toxin: Targeting mast cell secretory granules during kiss-and-run secretion.
abstract: Pasteurella multocida toxin (PMT), a virulence factor of the pathogenic Gram-negative bacterium P. multocida, is a 146 kDa protein belonging to the A-B class of toxins. Once inside a target cell, the A domain deamidates the α-subunit of heterotrimeric G-proteins, thereby activating downstream signaling cascades. However, little is known about how PMT selects and enters its cellular targets. We therefore studied PMT binding and uptake in porcine cultured intestinal mucosal explants to identify susceptible cells in the epithelium and underlying lamina propria. In comparison with Vibrio cholera B-subunit, a well-known enterotoxin taken up by receptor-mediated endocytosis, PMT binding to the epithelial brush border was scarce, and no uptake into enterocytes was detected by 2h, implying that none of the glycolipids in the brush border are a functional receptor for PMT. However, in the lamina propria, PMT distinctly accumulated in the secretory granules of mast cells. This also occurred at 4 °C, ruling out endocytosis, but suggestive of uptake via pores that connect the granules to the cell surface. Mast cell granules are known to secrete their contents by a "kiss-and-run" mechanism, and we propose that PMT may exploit this secretory mechanism to gain entry into this particular cell type.
authors.affiliation: Department of Cellular and Molecular Medicine, The Panum Institute, Faculty of Health Sciences, University of Copenhagen, Denmark.
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Danielsen
authors.affiliation: Department of Cellular and Molecular Medicine, The Panum Institute, Faculty of Health Sciences, University of Copenhagen, Denmark.
authors.forename: Nina
authors.initials: N
authors.lastname: Christiansen
authors.affiliation: Department of Cellular and Molecular Medicine, The Panum Institute, Faculty of Health Sciences, University of Copenhagen, Denmark. Electronic address: midan@sund.ku.dk.
authors.forename: E Michael
authors.initials: EM
authors.lastname: Danielsen
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology / Q000382:microbiology; D008407:Mast Cells / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D016979:Pasteurella multocida / Q000737:chemistry* / Q000472:pathogenicity; D022142:Secretory Vesicles / Q000378:metabolism / Q000382:microbiology; D013552:Swine; D014734:Vibrio cholerae / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C062258:Pasteurella multocida toxin; D019204:GTP-Binding Proteins
keywords: Kiss-and-run; Mast cells; Pasteurella multocida toxin (PMT); Secretory granules; Small intestine; V. cholera toxin B-subunit (CTB)