Transcriptome analysis reveals that ClpXP proteolysis controls key virulence properties of Streptococcus mutans.

Center for Oral Biology, University of Rochester Medical Center, Rochester, NY 14642, USA.
Microbiology (Impact Factor: 3.06). 08/2011; 157(Pt 10):2880-90. DOI: 10.1099/mic.0.052407-0
Source: PubMed

ABSTRACT The ClpXP proteolytic complex is critical for maintaining cellular homeostasis, as well as expression of virulence properties. However, with the exception of the Spx global regulator, the molecular mechanisms by which the ClpXP complex exerts its influence in Streptococcus mutans are not well understood. Here, microarray analysis was used to provide novel insights into the scope of ClpXP proteolysis in S. mutans. In a ΔclpP strain, 288 genes showed significant changes in relative transcript amounts (P≤0.001, twofold cut-off) as compared with the parent. Similarly, 242 genes were differentially expressed by a ΔclpX strain, 113 (47 %) of which also appeared in the ΔclpP microarrays. Several genes associated with cell growth were downregulated in both mutants, consistent with the slow-growth phenotype of the Δclp strains. Among the upregulated genes were those encoding enzymes required for the biosynthesis of intracellular polysaccharides (glg genes) and malolactic fermentation (mle genes). Enhanced expression of glg and mle genes in ΔclpP and ΔclpX strains correlated with increased storage of intracellular polysaccharide and enhanced malolactic fermentation activity, respectively. Expression of several genes known or predicted to be involved in competence and mutacin production was downregulated in the Δclp strains. Follow-up transformation efficiency and deferred antagonism assays validated the microarray data by showing that competence and mutacin production were dramatically impaired in the Δclp strains. Collectively, our results reveal the broad scope of ClpXP regulation in S. mutans homeostasis and identify several virulence-related traits that are influenced by ClpXP proteolysis.

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    ABSTRACT: Using B. subtilis as a model organism, we investigated thermotolerance development by analyzing cell survival and in vivo protein aggregate formation in severely heat shocked cells primed by a mild heat shock. We observed an increased survival during severe heat stress, accompanied by a strong reduction of heat-induced cellular protein aggregates in cells lacking the ClpXP protease. We could demonstrate that the transcription factor Spx, a regulatory substrate of ClpXP, is critical for the prevention of protein aggregate formation because its regulon encodes redox chaperones, such as thioredoxin, required for protection against thiol specific oxidative stress. Consequently B. subtilis cells grown in the absence of oxygen were more protected against severe heat shock and much less protein aggregates were detected compared to aerobically grown cells. The presented results indicate that in B. subtilis Spx and its regulon plays not only an important role for oxidative but also for heat stress response and thermotolerance development. In addition, our experiments suggest that the protection of misfolded proteins from thiol oxidation during heat shock can be critical for the prevention of cellular protein aggregation in vivo.
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