title: Staphylococcus aureus α-toxin-mediated cation entry depolarizes membrane potential and activates p38 MAP kinase in airway epithelial cells.
abstract: Membrane potential (Vm)-, Na(+)-, or Ca(2+)-sensitive fluorescent dyes were used to analyze changes in Vm or intracellular ion concentrations in airway epithelial cells treated with Staphylococcus aureus α-toxin (Hla), a major virulence factor of pathogenic strains of these bacteria. Gramicidin, a channel-forming peptide causing membrane permeability to monovalent cations, a mutated form of Hla, rHla-H35L, which forms oligomers in the plasma membranes of eukaryotic cells but fails to form functional transmembrane pores, or the cyclodextrin-derivative IB201, a blocker of the Hla pore, were used to investigate the permeability of the pore. Na(+) as well as Ca(2+) ions were able to pass the Hla pore and accumulated in the cytosol. The pore-mediated influx of calcium ions was blocked by IB201. Treatment of cells with recombinant Hla resulted in plasma membrane depolarization as well as in increases in the phosphorylation levels of paxillin (signaling pathway mediating disruption of the actin cytoskeleton) and p38 MAP kinase (signaling pathway resulting in defensive actions). p38 MAP kinase phosphorylation, but not paxillin phosphorylation, was elicited by treatment of cells with gramicidin. Although treatment of cells with rHla-H35L resulted in the formation of membrane-associated heptamers, none of these cellular effects were observed in our experiments. This indicates that formation of functional Hla-transmembrane pores is required to induce the cell physiological changes mediated by α-toxin. Specifically, the changes in ion equilibria and plasma membrane potential are important activators of p38 MAP kinase, a signal transduction module involved in host cell defense.
authors: Animal Physiology and Biochemistry, Ernst Moritz Arndt-University, Greifswald, Germany.
authors: Ina
authors: I
authors: Eiffler
authors: Animal Physiology and Biochemistry, Ernst Moritz Arndt-University, Greifswald, Germany.
authors: Jane
authors: J
authors: Behnke
authors: Animal Physiology and Biochemistry, Ernst Moritz Arndt-University, Greifswald, Germany.
authors: Sabine
authors: S
authors: Ziesemer
authors: Animal Physiology and Biochemistry, Ernst Moritz Arndt-University, Greifswald, Germany.
authors: Christian
authors: C
authors: Müller
authors: Animal Physiology and Biochemistry, Ernst Moritz Arndt-University, Greifswald, Germany jph@uni-greifswald.de.
authors: Jan-Peter
authors: JP
authors: Hildebrandt
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D001427:Bacterial Toxins / Q000494:pharmacology; D020013:Calcium Signaling; D002460:Cell Line; D002463:Cell Membrane Permeability; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D020935:MAP Kinase Signaling System; D008564:Membrane Potentials; D013211:Staphylococcus aureus / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Staphylococcus aureus; airway epithelial cells; membrane potential; p38 MAP kinase; paxillin; plasma membrane ion permeability; virulence factor; α-hemolysin; α-toxin