title: Autocatalytic cleavage of Clostridium difficile toxin B.
abstract: Clostridium difficile, the causative agent of nosocomial antibiotic-associated diarrhoea and pseudomembranous colitis, possesses two main virulence factors: the large clostridial cytotoxins A and B. It has been proposed that toxin B is cleaved by a cytosolic factor of the eukaryotic target cell during its cellular uptake. Here we report that cleavage of not only toxin B, but also all other large clostridial cytotoxins, is an autocatalytic process dependent on host cytosolic inositolphosphate cofactors. A covalent inhibitor of aspartate proteases, 1,2-epoxy-3-(p-nitrophenoxy)propane, completely blocked toxin B function on cultured cells and was used to identify its catalytically active protease site. To our knowledge this is the first report on a bacterial toxin that uses eukaryotic signals for induced autoproteolysis to deliver its toxic domain into the cytosol of target cells. On the basis of our data, we present an integrated model for the uptake and inositolphosphate-induced activation of toxin B.
authors.affiliation: Johannes-Gutenberg Universität Mainz, Institut für medizinische Mikrobiologie and Hygiene, Hochhaus am Augustusplatz, 55131 Mainz, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Reineke
authors.forename: Stefan
authors.initials: S
authors.lastname: Tenzer
authors.forename: Maja
authors.initials: M
authors.lastname: Rupnik
authors.forename: Andreas
authors.initials: A
authors.lastname: Koschinski
authors.forename: Oliver
authors.initials: O
authors.lastname: Hasselmayer
authors.forename: André
authors.initials: A
authors.lastname: Schrattenholz
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Schild
authors.forename: Christoph
authors.initials: C
authors.lastname: von Eichel-Streiber
mesh_terms: D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites / Q000187:drug effects; D001685:Biological Factors / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D002384:Catalysis / Q000187:drug effects; D002457:Cell Extracts / Q000737:chemistry; D002460:Cell Line; D016360:Clostridioides difficile / Q000472:pathogenicity* / Q000502:physiology; D004852:Epoxy Compounds / Q000494:pharmacology; D009596:Nitrophenols / Q000494:pharmacology; D010833:Phytic Acid / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport; D013154:Spleen / Q000166:cytology; D013552:Swine; D037521:Virulence Factors / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D001685:Biological Factors; D002457:Cell Extracts; D004852:Epoxy Compounds; D009596:Nitrophenols; D037521:Virulence Factors; C031815:toxB protein, Clostridium difficile; D010833:Phytic Acid; C007606:1,2-epoxy-3-(p-nitrophenoxy)propane; D016282:Aspartic Acid Endopeptidases