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Cyclic di-GMP Signaling Regulates Invasion by Ehrlichia chaffeensis of Human Monocytes
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| Zeitschriftentitel: | Journal of Bacteriology |
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| Personen und Körperschaften: | , , , |
| In: | Journal of Bacteriology, 192, 2010, 16, S. 4122-4133 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
American Society for Microbiology
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| Schlagwörter: |
| Zusammenfassung: | <jats:title>ABSTRACT</jats:title> <jats:p> Cyclic di-GMP (c-di-GMP) is a bacterial second messenger produced by GGDEF domain-containing proteins. The genome of <jats:italic>Ehrlichia chaffeensis</jats:italic> , an obligatory intracellular bacterium that causes human monocytic ehrlichiosis, encodes a single protein that contains a GGDEF domain, called PleD. In this study, we investigated the effects of c-di-GMP signaling on <jats:italic>E. chaffeensis</jats:italic> infection of the human monocytic cell line THP-1. Recombinant <jats:italic>E. chaffeensis</jats:italic> PleD showed diguanylate cyclase activity as it generated c-di-GMP <jats:italic>in vitro</jats:italic> . Because c-di-GMP is not cell permeable, the c-di-GMP hydrophobic analog 2′- <jats:italic>O</jats:italic> -di( <jats:italic>tert</jats:italic> -butyldimethylsilyl)-c-di-GMP (CDGA) was used to examine intracellular c-di-GMP signaling. CDGA activity was first tested with <jats:italic>Salmonella enterica</jats:italic> serovar Typhimurium. CDGA inhibited well-defined c-di-GMP-regulated phenomena, including cellulose synthesis, clumping, and upregulation of <jats:italic>csgD</jats:italic> and <jats:italic>adrA</jats:italic> mRNA, indicating that CDGA acts as an antagonist in c-di-GMP signaling. [ <jats:sup>32</jats:sup> P]c-di-GMP bound several <jats:italic>E. chaffeensis</jats:italic> native proteins and two <jats:italic>E. chaffeensis</jats:italic> recombinant I-site proteins, and this binding was blocked by CDGA. Although pretreatment of <jats:italic>E. chaffeensis</jats:italic> with CDGA did not reduce bacterial binding to THP-1 cells, bacterial internalization was reduced. CDGA facilitated protease-dependent degradation of particular, but not all, bacterial surface-exposed proteins, including TRP120, which is associated with bacterial internalization. Indeed, the serine protease HtrA was detected on the surface of <jats:italic>E. chaffeensis</jats:italic> , and TRP120 was degraded by treatment of <jats:italic>E. chaffeensis</jats:italic> with recombinant <jats:italic>E. chaffeensis</jats:italic> HtrA. Furthermore, anti-HtrA inhibited CDGA-induced TRP120 degradation. Our results suggest that <jats:italic>E. chaffeensis</jats:italic> invasion is regulated by c-di-GMP signaling, which stabilizes some bacterial surface-exposed proteins against proteases. </jats:p> |
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| Umfang: | 4122-4133 |
| ISSN: |
0021-9193
1098-5530 |
| DOI: | 10.1128/jb.00132-10 |