Role of Clp Proteins in Expression of Virulence Properties of Streptococcus mutans

Center for Oral Biology, University of Rochester Medical Center, NY 14642, USA.
Journal of bacteriology (Impact Factor: 2.81). 02/2009; 191(7):2060-8. DOI: 10.1128/JB.01609-08
Source: PubMed


Mutational analysis revealed that members of the Clp system, specifically the ClpL chaperone and the ClpXP proteolytic complex,
modulate the expression of important virulence attributes of Streptococcus mutans. Compared to its parent, the ΔclpL strain displayed an enhanced capacity to form biofilms in the presence of sucrose, had reduced viability, and was more sensitive
to acid killing. The ΔclpP and ΔclpX strains displayed several phenotypes in common: slow growth, tendency to aggregate in culture, reduced autolysis, and reduced
ability to grow under stress, including acidic pH. Unexpectedly, the ΔclpP and ΔclpX mutants were more resistant to acid killing and demonstrated enhanced viability in long-term survival assays. Biofilm formation
by the ΔclpP and ΔclpX strains was impaired when grown in glucose but enhanced in sucrose. In an animal study, the average number of S. mutans colonies recovered from the teeth of rats infected with the ΔclpP or ΔclpX strain was slightly lower than that of the parent strain. In Bacillus subtilis, the accumulation of the Spx global regulator, a substrate of ClpXP, has accounted for the ΔclpXP phenotypes. Searching the S. mutans genome, we identified two putative spx genes, designated spxA and spxB. The inactivation of either of these genes bypassed phenotypes of the clpP and clpX mutants. Western blotting demonstrated that Spx accumulates in the ΔclpP and ΔclpX strains. Our results reveal that the proteolysis of ClpL and ClpXP plays a role in the expression of key virulence traits
of S. mutans and indicates that the underlying mechanisms by which ClpXP affect virulence traits are associated with the accumulation
of two Spx orthologues.

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Available from: Jacqueline Abranches, Feb 10, 2015
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    • "view, two CDSs with altered expression in the Vru mutant showed homology to other known regulatory elements. Transcription of a gene encoding an RNA polymerase sigma factor was suppressed, whereas that encoding a putative transcriptional regulator, spxA (Kajfasz et al., 2009), was enhanced. "
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    ABSTRACT: The regulation and control of gene expression in response to differing environmental stimuli is crucial for successful pathogen adaptation and persistence. The regulatory gene vru of Streptococcus uberis encodes a stand-alone response regulator with similarity to the Mga of group A Streptococcus. Mga controls expression of a number of important virulence determinants. Experimental intramammary challenge of dairy cattle with a mutant of S. uberis carrying an inactivating lesion in vru showed reduced ability to colonize the mammary gland and an inability to induce clinical signs of mastitis compared with the wild-type strain. Analysis of transcriptional differences of gene expression in the mutant, determined by microarray analysis, identified a number of coding sequences with altered expression in the absence of Vru. These consisted of known and putative virulence determinants, including Lbp (Sub0145), SclB (Sub1095), PauA (Sub1785) and hasA (Sub1696).
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    • "Several genes encoding ribosomal proteins, translation initiation factors and elongation factors were downregulated in both mutants, consistent with the slow-growth phenotype previously described for the two Dclp mutant strains (Kajfasz et al., 2009 "
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    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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    • "The extent and importance of Clp-mediated proteolysis is well illustrated in Bacillus subtilis, where ClpP is responsible for 50 % of cellular protein turnover and is a major control factor in the transition from exponential-to stationaryphase growth (Kock et al., 2004) and the downregulation of central metabolism in glucose-starved cells (Gerth et al., 2008). The influence of ClpP extends to diverse areas of cellular activity, and the virulence of several bacterial pathogens, including Streptococcus mutans, Streptococcus pneumoniae, Staphylococcus aureus and Listeria monocytogenes , has been shown to rely on ClpP and Clp ATPases (Frees et al., 2004; Gaillot et al., 2000; Ibrahim et al., 2005; Kajfasz et al., 2009). "
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