Campylobacter jejuniserine protease HtrA plays an important role in heat tolerance, oxygen resistance, host cell adhesion, invasion, and transmigration

Abstract

Campylobacter jejuni is an important pathogen of foodborne illness. Transmigration across the intestinal epithelial barrier and invasion are considered as primary reasons for tissue damage triggered by C. jejuni. Using knockout mutants, it was shown that the serine protease HtrA may be important for stress tolerance and physiology of C. jejuni. HtrA is also secreted in the extracellular environment, where it can cleave junctional host cell proteins such as E-cadherin. Aim of the present study was to establish a genetic complementation system in two C. jejuni strains in order to introduce the wild-type htrA gene in trans, test known htrA phenotypes, and provide the basis to perform further mutagenesis. We confirm that reexpression of the htrA wild-type gene in ΔhtrA mutants restored the following phenotypes: 1) C. jejuni growth at high temperature (44 °C), 2) growth under high oxygen stress conditions, 3) expression of proteolytically active HtrA oligomers, 4) secretion of HtrA into the supernatant, 5) cell attachment and invasion, and 6) transmigration across polarized epithelial cells. These results establish a genetic complementation system for htrA in C. jejuni, exclude polar effects in the ΔhtrA mutants, confirm important HtrA properties, and permit the discovery and dissection of new functions.

HtrA-mediated E-cadherin cleavage is limited to DegP and DegQ homologs expressed by gram-negative pathogens

“…For instance, DegP was identified as a critical factor for IcsA (VirG) surface presentation in Shigella flexneri ( S. flexneri ) [14]. Furthermore, reduced adherence of a C. jejuni htrA knock-out mutant was observed in vitro [15–18] suggesting that the expression of adhesins might be downregulated. However, in a mouse model for C. jejuni infections, isogenic htrA -negative bacteria colonized equally well, while host cell apoptosis and the pro-inflammatory immune responses were significantly attenuated [19, 20].…”

The Periplasmic Chaperone Network of Campylobacter jejuni: Evidence that SalC (Cj1289) and PpiD (Cj0694) Are Involved in Maintaining Outer Membrane Integrity

“…HtrA has been shown to be essential for E. coli survival at high temperatures, and this phenotype has been confirmed in C. jejuni (Lipinska et al, 1989; Brøndsted et al, 2005; Boehm et al, 2015). It is known that HtrA is secreted by C. jejuni and H. pylori in the gut to digest the host cell adhesion protein E -cadherin, and recently this was shown to be mediated by OM vesicles (Elmi et al, 2016).…”

“…The effects of removal of Cj0596 (PEB4), Cj1069 (VirK) and Cj1228 (HtrA) have been previously studied in mutants made in different parental wild-type backgrounds (Novik et al, 2009; Rathbun et al, 2009; Boehm et al, 2015). Here, we sought to compare the phenotypes of these mutants with those in genes encoding the putative chaperones Cj0694 and Cj1289, which have not previously been characterized, in a single parental strain background.…”

Extracellular HtrA serine proteases: An emerging new strategy in bacterial pathogenesis

“…Generally, ectodomain shedding of E-cadherin leads to loss of intercellular adhesion, and disintegration of the intracellular AJ complex is involved in cancer-associated signal transduction, which has been summarised in several excellent review articles (Chan, 2006;Repetto, De Paoli, De Re, Canzonieri, & Cannizzaro, 2014). HtrA activity in C. jejuni is important not only for heat tolerance and oxygen resistance but also for bacterial invasion and transmigration, which finally contributes to in vivo pathogenesis (Boehm, Lind, Backert, & Tegtmeyer, 2015;. Among those bacteria, C. jejuni attracted special attention, since HtrA is secreted and responsible for E-cadherin shedding in cell culture infection models (Boehm et al, 2013;Hoy et al, 2012).…”