title: Activation of cellular phospholipase A2 by Clostridium difficile toxin B.
abstract: C. difficile toxin B is a potent cytotoxin known to disrupt the microfilaments of cultured cells. We have recently shown also increased phospholipase A2 activity in cells treated with toxin B. The activity was detected as a toxin-induced, dose-dependent release of 14C-arachidonic acid from prelabeled fibroblasts. Here is shown that the toxin elicited a 14C-arachidonic acid release in a cell mutant resistant to the toxin B effect on the microfilaments. The toxin-induced release was further characterized using fibroblasts. Within 20 min high doses of toxin B (6 micrograms/ml) elicited a release which increased exponentially with time. Of the major membrane phospholipids the lipase activity affected mainly phosphatidyl ethanolamine. Neither cycloheximide nor pertussis toxin treatment or target cells inhibited the toxin-induced release, while it could be increased with 12-O-tetradecanoylphorbol-13-acetate. Our results also suggest a toxin-mediated increase in phospholipase C activity occurring at a later stage than the phospholipase A2 activation. We conclude that the ability of toxin B to induce phospholipase activation represents a hitherto unrecognized toxin B effect which is neither a cause nor a consequence of toxin-induced microfilament disorganization.
authors.affiliation: Department of Bacteriology, Karolinska Institute, Stockholm, Sweden.
authors.forename: M C
authors.initials: MC
authors.lastname: Shoshan
authors.forename: I
authors.initials: I
authors.lastname: Florin
authors.forename: M
authors.initials: M
authors.lastname: Thelestam
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D016360:Clostridioides difficile; D003599:Cytoskeleton / Q000187:drug effects*; D003603:Cytotoxins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D037342:Pertussis Toxin; D010741:Phospholipases A / Q000187:drug effects*; D054467:Phospholipases A2; D014176:Protein Biosynthesis; D011493:Protein Kinase C / Q000502:physiology; D010738:Type C Phospholipases / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003603:Cytotoxins; D010566:Virulence Factors, Bordetella; C031815:toxB protein, Clostridium difficile; D016718:Arachidonic Acid; D037342:Pertussis Toxin; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium