Internalization of staphylococcal leukotoxins that bind and divert the C5a receptor is required for intracellular Ca(2+) mobilization by human neutrophils.
A growing number of receptors, often associated with the innate immune response, are being identified as targets for bacterial toxins of the beta-stranded pore-forming family. These findings raise the new question of whether the receptors are activated or merely used as docking points facilitating the formation of a pore. To elucidate whether the Staphylococcus aureus Panton-Valentine leukocidin and the leukotoxin HlgC/HlgB act through the C5a receptor (C5aR) as agonists, antagonists or differ from the C5a complement-derived peptide, their activity is explored on C5aR-expressing cells. Both leukotoxins equally bound C5aR in neutrophils and in stable transfected U937 cells and initiated mobilization of intracellular Ca(2+) . HlgC/HlgB requires the presence of robust intracellular acidic Ca(2+) stores in order to evoke a rise in free [Ca(2+) ]i , while the LukS-PV/LukF-PV directly altered reticular Ca(2+) stores. Intracellular target specificity is conferred by the F-subunit associated to the S-subunit binding the receptor. Furthermore, internalization of the two leukotoxin components (S- and F-subunits) associated to C5aR is required for the initiation of [Ca(2+) ]i mobilization. Electrophysiological recordings on living cells demonstrated that LukS-PV/LukF-PV does not alter the membrane resistance of C5aR-expressing cells. The present observations suggest that part of the pore-forming process occurs in distinct intracellular compartments rather than at the plasma membrane.
Fédération de Médecine Translationnelle de Strasbourg, EA7290 Virulence Bactérienne Précoce, Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg, Université de Strasbourg, Strasbourg, France.
Mira Y
MY
Tawk
Fédération de Médecine Translationnelle de Strasbourg, EA7290 Virulence Bactérienne Précoce, Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg, Université de Strasbourg, Strasbourg, France.
Kiran
K
Zimmermann
INCI - UPR-CNRS 3212, Physiologie des réseaux de neurones, Strasbourg, France.
Jean-Louis
JL
Bossu
National Research Council of Italy, Institute of Biophysics and Bruno Kessler Foundation, Trento, Italy.
Cristina
C
Potrich
Fédération de Médecine Translationnelle de Strasbourg, EA7290 Virulence Bactérienne Précoce, Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg, Université de Strasbourg, Strasbourg, France.
Tristan
T
Bourcier
National Research Council of Italy, Institute of Biophysics and Bruno Kessler Foundation, Trento, Italy.
Mauro
M
Dalla Serra
INCI - UPR-CNRS 3212, Physiologie des réseaux de neurones, Strasbourg, France.
Bernard
B
Poulain
Fédération de Médecine Translationnelle de Strasbourg, EA7290 Virulence Bactérienne Précoce, Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg, Université de Strasbourg, Strasbourg, France.
Gilles
G
Prévost
Fédération de Médecine Translationnelle de Strasbourg, EA7290 Virulence Bactérienne Précoce, Institut de Bactériologie et Hôpitaux Universitaires de Strasbourg, Université de Strasbourg, Strasbourg, France.
Emmanuel
E
Jover
D001427:Bacterial Toxins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D055724:Electrophysiological Phenomena; D005098:Exotoxins / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D007956:Leukocidins / Q000378:metabolism*; D009000:Monocytes / Q000382:microbiology / Q000502:physiology; D009504:Neutrophils / Q000382:microbiology* / Q000502:physiology*; D011485:Protein Binding; D044087:Receptor, Anaphylatoxin C5a / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000276:immunology*
D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D044087:Receptor, Anaphylatoxin C5a; C018579:leukotoxin; D002118:Calcium