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Infection and Immunity, February 2008, p. 857-862, Vol. 76, No. 2
0019-9567/08/$08.00+0     doi:10.1128/IAI.00622-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Listeria monocytogenes Desensitizes Immune Cells to Subsequent Ca2+ Signaling via Listeriolysin O-Induced Depletion of Intracellular Ca2+ Stores{triangledown}

Nelson O. Gekara,1* Lothar Groebe,2 Nuno Viegas,1 and Siegfried Weiss1

Department of Molecular Immunology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany,1 Department of Mucosal Immunity, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany2

Received 2 May 2007/ Returned for modification 31 July 2007/ Accepted 12 November 2007

Listeriolysin O (LLO), the pore-forming toxin of Listeria monocytogenes, is a prototype of the cholesterol-dependent cytolysins (CDCs) secreted by several pathogenic and nonpathogenic gram-positive bacteria. In addition to mediating the escape of the bacterium into the cytosol, this toxin is generally believed to be a central player in host-pathogen interactions during L. monocytogenes infection. LLO triggers the influx of Ca2+ into host cells as well as the release of Ca2+ from intracellular stores. Thus, many of the cellular responses induced by LLO are related to calcium signaling. Interestingly, in this study, we report that prolonged exposure to LLO desensitizes cells to Ca2+ mobilization upon subsequent stimulations with LLO. Cells preexposed to LLO-positive L. monocytogenes but not to the LLO-deficient {Delta}hly mutant were found to be highly refractory to Ca2+ induction in response to receptor-mediated stimulation. Such cells also exhibited diminished Ca2+ signals in response to stimulation with LLO and thapsigargin. The presented results suggest that this phenomenon is due to the depletion of intracellular Ca2+ stores. The ability of LLO to desensitize immune cells provides a significant hint about the possible role played by CDCs in the evasion of the immune system by bacterial pathogens.

* Corresponding author. Mailing address: Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany. Phone: 49 531 6181 5108. Fax: 49 531 6181 51002. E-mail: nelson.gekara{at}helmholtz-hzi.de

{triangledown} Published ahead of print on 3 December 2007.

Editor: V. J. DiRita

Infection and Immunity, February 2008, p. 857-862, Vol. 76, No. 2
0019-9567/08/$08.00+0     doi:10.1128/IAI.00622-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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