clpB, a class III heat-shock gene regulated by CtsR, is involved in thermotolerance and virulence of Enterococcus faecalis

Abstract

Here, we transcriptionally and phenotypically characterized the clpB gene from Enterococcus faecalis. Northern blot analysis identified a monocistronic mRNA strongly induced at 48 and 50 6C. In silico analysis identified that the clpB gene encodes a protein of 868 aa with a predicted molecular mass of approximately 98 kDa, presenting two conserved ATP-binding domains. Sequence analysis also identified a CtsR-binding box upstream of the putative "10 sequence, and inactivation of the ctsR gene resulted in an approximately 2-log increase in clpB mRNA expression, confirming ClpB as a member of the CtsR regulon. While expression of clpB was induced by heat stress, a DclpB strain grew relatively well under many different stressful conditions, including elevated temperatures. However, expression of ClpB appears to play a major role in induced thermotolerance and in pathogenesis, as assessed by using the Galleria mellonella virulence model.

Stress Physiology of Lactic Acid Bacteria

“…In contrast, ClpX is not essential in S. mutans (304). Phenotypic studies with mutant strains lacking functional ClpP, ClpL, ClpE, or ClpB revealed the central role of these proteins under stress conditions and, for pathogenic LAB species, in virulence (303,(305)(306)(307)(308). In contrast to the situation in B. subtilis, LAB clpC mutants usually do not exhibit stress-sensitive phenotypes (306,309).…”

“…E. faecalis carries genes for ClpP, ClpB, ClpC, ClpE, and ClpX (214). Deletion of clpB reduced the ability of E. faecalis to acquire thermotolerance and for pathogenesis as assessed in Galleria mellonella larvae (308). Another highly conserved bacterial protein associated with the pathogenic potential of streptococcal species is HtrA.…”

Simultaneous Host-Pathogen Transcriptome Analysis during Granulibacter bethesdensis Infection of Neutrophils from Healthy Subjects and Patients with Chronic Granulomatous Disease

“…6A). The protein encoded by clpB is a protein aggregate-disrupting chaperone that has been shown to be a virulence factor in a variety of pathogens, including Francisella tularensis (50), Leptospira interrogans (51), and Enterococcus faecalis (52). To date, our efforts to genetically manipulate G. bethesdensis using standard molecular biology approaches have failed.…”

Protein aggregation in Ehrlichia chaffeensis during infection of mammalian cells

“…ClpB cooperates with the members of Hsp70 and Hsp40 chaperone families in resolubilization and reactivation of aggregated proteins that accumulate in cells under conditions of stress (Zolkiewski, Zhang and Nagy 2012;Mogk, Kummer and Bukau 2015). ClpB supports virulence and survival of a number of bacterial and protozoan pathogens including Staphylococcus aureus (Frees et al 2004), Pseudomonas aeruginosa (Lehoux, Sanschagrin and Levesque 2002), Salmonella typhimurium (Turner et al 1998), Shigella dysenteriae (Pieper et al 2009;Kuntumalla et al 2011), Porphyromonas gingivalis (Capestany et al 2008), Mycoplasma pneumoniae (Kannan et al 2008), Francisella tularensis (Meibom et al 2008), Enterococcus faecalis (de Oliveira et al 2011), Mycobacterium tuberculosis (Estorninho et al 2010;Vaubourgeix et al 2015), Leptospira interrogans (Lourdault et al 2011), Leischmania donovani (Krobitsch and Clos 1999) and Plasmodium falciparum (Beck et al 2014;Elsworth et al 2014). These established links between ClpB and the infectivity and survival of multiple different pathogens suggest that host-induced stress can result in misfolding and aggregation of pathogen's proteins and that their functional restoration can be mediated by ClpB.…”