Aerolysin induces G-protein activation and Ca2+ release from intracellular stores in human granulocytes.
Aerolysin is a pore-forming toxin that plays a key role in the pathogenesis of Aeromonas hydrophila infections. In this study, we have analyzed the effect of aerolysin on human granulocytes (HL-60 cells). Proaerolysin could bind to these cells, was processed into active aerolysin, and led to membrane depolarization, indicating that granulocytes are potential targets for this toxin. Fura-2 measurements were used to analyze the effect of aerolysin on cytosolic [Ca2+] homeostasis. As expected for a pore-forming toxin, aerolysin addition led to Ca2+ influx across the plasma membrane. In addition, the toxin triggered Ca2+ release from agonist and thapsigargin-sensitive intracellular Ca2+ stores. This Ca2+ release was independent of the aerolysin-induced Ca2+ influx and occurred in two kinetically distinct phases: an initial rapid and transient phase and a second, more sustained, phase. The first, but not the second phase was sensitive to pertussis toxin. Activation of pertussis toxin-sensitive G-proteins appeared to be a consequence of pore formation, rather than receptor activation through aerolysin-binding, as it: (i) was not observed with a binding competent, insertion-incompetent aerolysin mutant, (ii) had a marked lag time, and (iii) was also observed in response to other bacterial pore-forming toxins (staphylococcal alpha-toxin, streptolysin O) which are thought to bind to different receptors. G-protein activation through pore-forming toxins stimulated cellular functions, as evidenced by pertussis toxin-sensitive chemotaxis. Our results demonstrate that granulocytes are potential target cells for aerolysin and that in these cells, Ca2+ signaling in response to a pore-forming toxin involves G-protein-dependent cell activation and Ca2+ release from intracellular stores.
Krause
K H
KH
Infectious Diseases Division, University Hospital, 1211 Geneva 14, Switzerland.
Fivaz
M
M
Monod
A
A
van der Goot
F G
FG
D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000378:metabolism / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D004072:Digitonin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006098:Granulocytes / Q000187:drug effects / Q000378:metabolism*; D018922:HL-60 Cells; D006460:Hemolysin Proteins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D037342:Pertussis Toxin; D052899:Pore Forming Cytotoxic Proteins; D011188:Potassium / Q000378:metabolism; D013301:Streptolysins / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D007473:Ion Channels; D052899:Pore Forming Cytotoxic Proteins; D013301:Streptolysins; D010566:Virulence Factors, Bordetella; C107096:proaerolysin; C021091:staphylococcal alpha-toxin; C025964:streptolysin O; C032676:aerolysin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D004072:Digitonin; D011188:Potassium; D002118:Calcium