clpB, a Novel Member of theListeria monocytogenesCtsR Regulon, Is Involved in Virulence but Not in General Stress Tolerance

Abstract

Clp-HSP100 ATPases are a widespread family of ubiquitous proteins that occur in both prokaryotes and eukaryotes and play important roles in the folding of newly synthesized proteins and refolding of aggregated proteins. They have also been shown to participate in the virulence of several pathogens, including Listeria monocytogenes. Here, we describe a member of the Clp-HSP100 family of L. monocytogenes that harbors all the characteristics of the ClpB subclass, which is absent in the closely related gram-positive model organism, Bacillus subtilis. Transcriptional analysis of clpB revealed a heat shock-inducible A -type promoter. Potential binding sites for the CtsR regulator of stress response were identified in the promoter region. In vivo and in vitro approaches were used to show that expression of clpB is repressed by CtsR, a finding indicating that clpB is a novel member of the L. monocytogenes CtsR regulon. We showed that ClpB is involved in the pathogenicity of L. monocytogenes since the ⌬clpB mutant is significantly affected by virulence in a murine model of infection; we also demonstrate that this effect is apparently not due to a defect in general stress resistance. Indeed, ClpB is not involved in tolerance to heat, salt, detergent, puromycin, or cold stress, even though its synthesis is inducible by heat shock. However, ClpB was shown to play a role in induced thermotolerance, allowing increased resistance of L. monocytogenes to lethal temperatures. This work gives the first example of a clpB gene directly controlled by CtsR and describes the first role for a ClpB protein in induced thermotolerance and virulence in a gram-positive organism.

Microarray Analysis of Quorum-Sensing-Regulated Genes inPorphyromonas gingivalis

“…It has also been shown that an S. enterica serovar Typhimurium heat shock protein is involved in mucus-mediated interaction of the bacterium with the host (18). Additionally, other stress gene mutants (clpB) were found to have decreased virulence in Salmonella enterica serovar Typhimurium (51) and Listeria monocytogenes (7). Further, protection against a variety of infectious agents is thought to be due to antibodies directed against specific stress proteins that often involve conserved epitopes.…”

σBActivation under Environmental and Energy Stress Conditions inListeria monocytogenes

“…The findings obtained in this study highlight the importance of conducting expression analyses to identify the direct and indirect contributions of different transcriptional regulators to virulence and the stress response in bacterial pathogens under defined conditions. In addition to B and PrfA, a number of other transcriptional regulators also control expression of genes that contribute to virulence and the stress response, including L. monocytogenes CtsR (8,37). Interestingly, mutations in the CtsR-regulated gene clpC, which encodes an ATPase that belongs to a class of heat shock proteins involved in stress tolerance, result in attenuated L. monocytogenes virulence and bacterial susceptibility to multiple stresses, including high temperature, high osmolarity, and iron limitation (43,44,45).…”

Identification ofListeria monocytogenesGenes Contributing to Intracellular Replication by Expression Profiling and Mutant Screening

“…Of particular interest is the fourfold up-regulation of clpB encoding a subunit of the ATPdependent Clp protease. This proteolytic enzyme in bacterial cells has been shown previously to be an important factor for efficient intracellular growth of L. monocytogenes (7,30,31,36). By degradation of unnecessary proteins, Clp may provide amino acids, which could also serve as C and/or N sources for intracellularly growing L. monocytogenes.…”