Complex regulation of human neutrophil activation by actin filaments: dihydrocytochalasin B and botulinum C2 toxin uncover the existence of multiple cation entry pathways.
In human neutrophils, the chemotactic peptide, N-formyl-L-methionyl-L-leucyl-L-phenalalanine (fMLP), the Ca(2+)-ATPase inhibitor, thapsigargin, and the lectins, concanavalin A (Con A) and mistletoe lectin I (ML I), stimulate the entry of Ca2+ and Na+ with subsequent activation of exocytosis and superoxide anion (O2-) formation. We studied the role of actin in neutrophil activation. The actin filament-disrupting substances, dihydrocytochalasin B (dhCB) and botulinum C2 toxin (C2 toxin) potentiated fMLP- and lectin-stimulated Ca(2+)- and Na+ entry. Lectin-induced Mn2+ entry was enhanced by actin disruption, whereas fMLP-triggered Mn2+ entry was unaffected. dhCB and C2 toxin inhibited fMLP- and lectin-stimulated Ba2+ influx. The actin disrupters also inhibited fMLP- and ML I-induced Sr2+ influx, whereas Con A-stimulated Sr2+ entry was not influenced by dhCB and C2 toxin. Thapsigargin-stimulated cation entry was not altered by actin disruption. DhCB and botulinum C2 toxin potentiated lysozyme release induced by all four stimuli. Con A and ML I per se activated O2- formation only in the presence and not in the absence of dhCB. Con A potentiated the stimulatory effects of ML I on O2- formation in the presence of dhCB and primed neutrophils to respond to ML I in the absence of dhCB. Our data indicate the following: (1) dhCB and C2 toxin uncover the existence of multiple cation entry pathways in neutrophils; (2) actin disruption facilitates exocytosis and O2- formation by enhancement of Ca(2+)- and Na+ entry and by altering the function of proteins involved in activation of secretion and O2- formation; and (3) Con A and ML I, which possess different sugar specificities, activate different signaling pathways in neutrophils.
Wenzel-Seifert
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Institut für Pharmakologie, Freie Universität Berlin, Germany.
Lentzen
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Aktories
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Seifert
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D000199:Actins / Q000097:blood / Q000187:drug effects / Q000502:physiology*; D001464:Barium / Q000097:blood; D001905:Botulinum Toxins / Q000494:pharmacology*; D002118:Calcium / Q000097:blood; D002412:Cations / Q000097:blood*; D003571:Cytochalasin B / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D037102:Lectins / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000097:blood; D009113:Muramidase / Q000097:blood; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation / Q000187:drug effects*; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D012964:Sodium / Q000097:blood; D013324:Strontium / Q000097:blood; D013481:Superoxides / Q000097:blood; D019284:Thapsigargin / Q000494:pharmacology; D014118:Toxins, Biological / Q000494:pharmacology
D000199:Actins; D002412:Cations; D037102:Lectins; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C488862:mistletoe lectin I; C009674:ribosome inactivating protein, Viscum; D013481:Superoxides; D001464:Barium; C024794:dihydrocytochalasin B; D003571:Cytochalasin B; D008345:Manganese; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019284:Thapsigargin; D012964:Sodium; D009113:Muramidase; D001905:Botulinum Toxins; C096324:botulinum toxin type C; D002118:Calcium; D013324:Strontium