Comparative Analysis of the Roles of HtrA-Like Surface Proteases in Two Virulent Staphylococcus aureus Strains

Abstract

The HtrA surface protease is involved in the virulence of many pathogens, mainly by its role in stress resistance and bacterial survival. Staphylococcus aureus encodes two putative HtrA-like proteases, referred to as HtrA 1 and HtrA 2 . To investigate the roles of HtrA proteins in S. aureus, we constructed htrA 1 , htrA 2 , and htrA 1 htrA 2 insertion mutants in two genetically different virulent strains, RN6390 and COL. In the RN6390 context, htrA 1 inactivation resulted in sensitivity to puromycin-induced stress. The RN6390 htrA 1 htrA 2 mutant was affected in the expression of several secreted virulence factors comprising the agr regulon. This observation was correlated with the disappearance of the agr RNA III transcript in the RN6390 htrA 1 htrA 2 mutant. The virulence of this mutant was diminished in a rat model of endocarditis. In the COL context, both HtrA 1 and HtrA 2 were essential for thermal stress survival. However, only HtrA 1 had a slight effect on exoprotein expression. The htrA mutations did not diminish the virulence of the COL strain in the rat model of endocarditis. Our results indicate that HtrA proteins have different roles in S. aureus according to the strain, probably depending on specific differences in the regulation of virulence factor and stress protein expression. We propose that HtrA 1 and HtrA 2 contribute to pathogenicity by controlling the production of certain extracellular factors that are crucial for bacterial dissemination, as revealed in the RN6390 background. We speculate that HtrA proteins act in the agr-dependent regulation pathway by assuring folding and/or maturation of some surface components of the agr system.

The HtrA-Like Protease CD3284 Modulates Virulence of Clostridium difficile

“…In Staphylococcus aureus COL, the deletion of htrA led to minimal changes in surface protein expression and virulence (73). In Brucella abortus, the htrA mutant was not found to be attenuated in a BALB/c mouse model (74).…”

Relapsing fever spirochaetes produce a serine protease that provides resistance to oxidative stress and killing by neutrophils

“…This gene, designated bhpA, encodes a protein with conserved domains found in a novel class of proteins, the HtrA-like serine proteases (Clausen et al, 2002). In other bacteria, these periplasmic proteases play a key role in the tolerance against various folding stresses (Strauch and Beckwith, 1988) and contribute to pathogenicity (Johnson et al, 1991;Boucher et al, 1996;Miller and Shinnick, 2000;Rigoulay et al, 2005). E. coli has three genes, degP, degQ, degS, that encode proteases in the HtrA family (Lipinska et al, 1988;Waller and Sauer, 1996).…”

Salmonella enterica Serovar Typhimurium HtrA: regulation of expression and role of the chaperone and protease activities during infection

“…This is not the case in Salmonella, but S. Typhimurium htrA mutants exhibit increased sensitivity to killing by reactive oxygen species and reduced survival and/or replication within macrophages (Baumler et al, 1994;Humphreys et al, 1999;Johnson et al, 1991), and are highly attenuated in the murine model of systemic Salmonella infection (Chatfield et al, 1992;Humphreys et al, 1999). Since the seminal studies in Salmonella, HtrA has been found to play a role in the virulence of a wide range of Gram-negative and Grampositive bacterial pathogens (Bringer et al, 2005;Cortes et al, 2002;Humphreys et al, 1999;Ibrahim et al, 2004;Johnson et al, 1991;Jones et al, 2001;Pallen & Wren, 1997;Pedersen et al, 2001;Rigoulay et al, 2005;Williams et al, 2000).…”