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Pneumolysin-dependent and -independent gene expression identified by cDNA microarray analysis of THP-1 human
P David Rogers1, Justin Thornton, Katherine S Barker
1Departments of Clinical Pharmacy and Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, USA.
Abstract:
Pneumolysin is an important virulence factor of Streptococcus pneumoniae, interacting with the membranes of host cells to elicit a multitude of inflammatory responses. We used cDNA microarrays to identify genes which are responsive to S. pneumoniae in a pneumolysin-dependent and -independent fashion. The THP-1 human monocytic cell line was coincubated for 3 h with medium alone, with the virulent type 2 S. pneumoniae strain D39, or with the isogenic strain PLN, which does not express pneumolysin. RNA was isolated from the monocytes and hybridized on cDNA microarrays. Of 4,133 genes evaluated, 142 were found to be responsive in a pneumolysin-dependent fashion, whereas 40 were found to be responsive independent of pneumolysin. Genes that were up-regulated in cells exposed to D39 relative to those exposed to PLN included genes encoding proteins such as mannose binding lectin 1, lysozyme, alpha-1 catenin, cadherin 17, caspases 4 and 6, macrophage inflammatory protein 1beta (MIP-1beta), interleukin 8 (IL-8), monocyte chemotactic protein 3 (MCP-3), IL-2 receptor beta (IL-2Rbeta), IL-15 receptor alpha (IL-15Ralpha), interferon receptor 2, and prostaglandin E synthase. Down-regulated genes included those encoding complement component receptor 2/CD21, platelet-activating factor acetylhydrolase, and oxidized low-density lipoprotein receptor 1 (OLR1). Pneumolysin-independent responses included down-regulation of the genes encoding CD68, CD53, CD24, transforming growth factor beta2, and signal transducers and activators of transcription 1. These results demonstrate the striking effects of pneumolysin on the host cell upon exposure to S. pneumoniae.
Insights
Pneumolysin from Streptococcus pneumoniae significantly impacts host cell gene expression. This study identified numerous genes responding to pneumolysin, revealing its crucial role in bacterial pathogenesis.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Pneumolysin is a key virulence factor of Streptococcus pneumoniae.
- It interacts with host cell membranes, triggering inflammatory responses.
Purpose of the Study:
- To identify genes responsive to Streptococcus pneumoniae in a pneumolysin-dependent and -independent manner.
- To elucidate the specific effects of pneumolysin on host cell gene expression.
Main Methods:
- Utilized cDNA microarrays to analyze gene expression in THP-1 human monocytic cells.
- Coincubated cells with virulent S. pneumoniae strain D39 and an isogenic strain lacking pneumolysin (PLN).
- Isolated RNA and hybridized to microarrays to assess gene expression changes.
Main Results:
- 142 genes responded in a pneumolysin-dependent fashion; 40 responded independently.
- Upregulated genes included those for inflammatory mediators (MIP-1beta, IL-8, MCP-3) and immune receptors.
- Downregulated genes included complement receptor 2/CD21 and OLR1; pneumolysin-independent responses affected CD68 and TGF-beta2.
Conclusions:
- Pneumolysin profoundly influences host cell gene expression upon S. pneumoniae exposure.
- The study highlights pneumolysin's critical role in modulating host inflammatory and immune responses.
- Identified specific genes and pathways affected by pneumolysin, offering insights into pneumococcal pathogenesis.