title: Involvement of a botulinum toxin-sensitive 22-kDa G protein in stimulated exocytosis of human neutrophils.
abstract: Studies of human peripheral blood neutrophils (PMNs) demonstrated that botulinum neurotoxin D (BT-D) ADP-ribosylates a 22-kDa PMN G protein (G22k) and inhibits the exocytosis of both specific and azurophilic granules stimulated by FMLP. Furthermore, this inhibition of PMN exocytosis by BT-D was found to be correlated with the degree of irreversible ADP-ribosylation of G22k by BT-D and to require modification of at least 85% of PMN G22k before significant inhibition of secretion is observed. Although both pertussis toxin and BT-D inhibited exocytosis in FMLP-stimulated PMNs, the inhibitory effects of the two toxins were found to be additive. Pertussis toxin and BT-D also inhibited Ca2+/GTP/GTP gamma S-induced secretion in digitonin-permeabilized PMNs, but there were distinct differences between the inhibitory effects of the two toxins. In contrast to BT-D, the exotoxin botulinum C3 was found to ADP-ribosylate primarily a 24- to 25-kDa PMN protein, and it was not found to inhibit Ca(2+)- and GTP-induced secretion in permeabilized PMNs. Ultrastructural studies of BT-D-treated PMNs showed an accumulation of distinct membrane-bound organelles in the periphery of the cells after FMLP stimulation, suggestive of a toxin-induced block in organelle-plasma membrane fusion. Taken together, these findings indicate that BT-D-sensitive G22k has a functional role in stimulated exocytosis of PMNs.
authors.affiliation: Department of Hematology, Walter Reed Army Institute of Research, Washington, DC 20307.
authors.forename: J
authors.initials: J
authors.lastname: Nath
authors.forename: A
authors.initials: A
authors.lastname: Powledge
authors.forename: D G
authors.initials: DG
authors.lastname: Wright
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism; D001905:Botulinum Toxins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects; D005089:Exocytosis; D019204:GTP-Binding Proteins / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010566:Virulence Factors, Bordetella; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006160:Guanosine Triphosphate; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D037342:Pertussis Toxin; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D002118:Calcium