Augmentation of staphylococcal alpha-toxin signaling by the epidermal platelet-activating factor receptor.
Staphylococcal alpha-toxin is a cytolytic toxin secreted by many strains of Staphylococcus aureus that has proinflammatory and cytotoxic effects on human keratinocytes. alpha-toxin exerts its effects by forming a transmembrane pore that behaves like an ionophore for ions such as calcium. Because cellular membrane disruption with resultant intracellular calcium mobilization is a potent stimulus for the synthesis for the lipid mediator platelet-activating factor, the ability of alpha-toxin to induce platelet-activating factor production was assessed, and whether the epidermal platelet-activating factor receptor could augment toxin-induced signaling in epithelial cells examined. Treatment of the human keratinocyte-derived cell line HaCaT with alpha-toxin resulted in significant levels of platelet-activating factor, which were approximately 50% of the levels induced by calcium ionophore A23187. alpha-toxin also stimulated arachidonic acid release in HaCaT keratinocytes. Pretreatment of HaCaT cells with platelet-activating factor receptor antagonists, or overexpression of the platelet-activating factor metabolizing enzyme acetylhydrolase II blunted alpha-toxin-induced arachidonic acid release by approximately one-third, suggesting a role for toxin-produced platelet-activating factor in this process. Finally, retroviral-mediated expression of the platelet-activating factor receptor into the platelet-activating factor receptor-negative epithelial cell line KB resulted in an augmentation of alpha-toxin-mediated intracellular calcium mobilization and arachidonic acid release. These studies suggest that alpha-toxin-mediated signaling can be augmented via the epidermal platelet-activating factor receptor.
Travers
Jeffrey B
JB
Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA. jtravers@iupui.edu
Leung
Donald Y M
DY
Johnson
Christopher
C
Schlievert
Patrick
P
Marques
Mariangela
M
Cosgrove
Jason
J
Clay
Keith L
KL
D016718:Arachidonic Acid / Q000378:metabolism; D001427:Bacterial Toxins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004817:Epidermis / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology; D006460:Hemolysin Proteins / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction; D013211:Staphylococcus aureus / Q000378:metabolism*; D013997:Time Factors
D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; C021091:staphylococcal alpha-toxin; D016718:Arachidonic Acid; D002118:Calcium