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View 2005 Conference Abstract
| Type of Submission |
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Submission Type: |
Poster |
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Subject Category: |
Infection and Immunity |
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| Session Information |
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Presentation Date: |
Tuesday June 14, 2005 |
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Abstract ID: |
B7 |
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Session: |
Poster I |
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Time: |
15:30-17:30 |
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| Presenting Author |
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| Other Authors |
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R GARDUNO, Dalhousie University
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| Title |
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The role of HtpB in the intracellular establishment of Legionella pneumophila |
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| Abstract Text |
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Legionella pneumophila is an intracellular bacterial pathogen of alveolar macrophages that causes the atypical pneumonia known as Legionnaires’ Disease. Inside macrophages, phagosomes containing L. pneumophila avoid fusion with lysosomes, recruit host vesicles and mitochondria, and mature into specialized replicative vacoules. These alterations in vesicular and organellar trafficking are mediated by the Dot/Icm type IV secretion system, implicated in the secretion of HtpB, the L. pneumophila 60-kDa chaperonin. HtpB plays a role in virulence since it: i) mediates invasion into HeLa cells, ii) is abundantly produced and secreted by intracellular L. pneumophila, and iii) alters cell signaling cascades in yeast. Our goal was to test whether HtpB also interferes with mammalian cell signaling cascades to redirect vesicular and organelle trafficking, an event essential for the intracellular proliferation of L. pneumophila. htpB was cloned into a tetracycline/doxycycline regulated expression vector, pTRE2hyg, and stably transfected into CHO-AA8 cells (Chinese hamster ovary cells expressing a tetracycline controlled transactivator). Phalloidin-stained CHO cells expressing recombinant HtpB display altered organization of stress fibers in relation to control CHO cells not expressing HtpB. Attachment and invasion of CHO cells by L. pneumophila was enhanced by the expression of recombinant HtpB. The recombinant HtpB did not affect the intracellular growth of wild type L. pneumophila, and was unable to rescue, in trans, the intracellular growth of an avirulent dotA mutant, which is unable to secrete HtpB. HtpB-coated beads significantly reduced the internalization but enhanced the intracellular growth of wild type L. pneumophila. HtpB-coated beads had little effect on the internalization and intracellular growth of the dotA mutant. Finally, internalized HtpB-coated beads, but not BSA-coated beads, were able to recruit host vesicles and mitochondria. These results strongly suggest that HtpB alters the mammalian cytoskeleton and redirects organelle trafficking, which may benefit the intracellular replication of L. pneumophila. |
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