Inhibition of Fc epsilon-RI-mediated activation of rat basophilic leukemia cells by Clostridium difficile toxin B (monoglucosyltransferase)
Treatment of rat basophilic leukemia (RBL) 2H3-hm1 cells with Clostridium difficile toxin B (2 ng/ml), which reportedly depolymerizes the actin cytoskeleton, blocked [3H]serotonin release induced by 2,4-dinitrophenyl-bovine serum albumin, carbachol, mastoparan, and reduced ionophore A23187-stimulated degranulation by about 55-60%. In lysates of RBL cells, toxin B 14C-glucosylated two major and one minor protein. By using two-dimensional gel electrophoresis and immunoblotting, RhoA and Cdc42 were identified as protein substrates of toxin B. In contrast to toxin B, Clostridium botulinum transferase C3 that selectively inactivates RhoA by ADP-ribosylation did not inhibit degranulation up to a concentration of 150 microg/ml. Antigen-stimulated tyrosine phosphorylation of a 110-kDa protein was inhibited by toxin B as well as by the phosphatidylinositol 3-kinase inhibitor wortmannin. Depolymerization of the microfilament cytoskeleton of RBL cells by C. botulinum C2 toxin or cytochalasin D resulted in an increased [3H]serotonin release induced by antigen, carbachol, mastoparan, or by calcium ionophore A23187, but without affecting toxin B-induced inhibition of degranulation. The data indicate that toxin B inhibits activation of RBL cells by glucosylation of low molecular mass GTP-binding proteins of the Rho subfamily (most likely Cdc42) by a mechanism not involving the actin cytoskeleton.
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Institut für Pharmakologie und Toxikologie der Albert-Ludwigs-Universität Freiburg, Germany.
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von Eichel-Streiber
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D019297:2,4-Dinitrophenol; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000633:toxicity*; D000001:Calcimycin / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D002460:Cell Line; D016360:Clostridioides difficile; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004140:Dinitrophenols / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005964:Glucosyltransferases / Q000633:toxicity*; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D015471:Leukemia, Basophilic, Acute; D010455:Peptides; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D051381:Rats; D017455:Receptors, IgE / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D014316:Tritium; D014407:Tumor Cells, Cultured; D014862:Wasp Venoms / Q000494:pharmacology; D000077191:Wortmannin
D019297:2,4-Dinitrophenol; D000246:Adenosine Diphosphate Ribose; D000730:Androstadienes; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D000001:Calcimycin; D002217:Carbachol; D004140:Dinitrophenols; D004791:Enzyme Inhibitors; D005964:Glucosyltransferases; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017455:Receptors, IgE; D012701:Serotonin; D012710:Serum Albumin, Bovine; D014316:Tritium; D014862:Wasp Venoms; D000077191:Wortmannin; C034638:dinitrophenyl-bovine serum albumin; C031815:toxB protein, Clostridium difficile; C037500:mastoparan