Cleavage of E-cadherin by porcine respiratory bacterial pathogens facilitates airway epithelial barrier disruption and bacterial paracellular transmigration

Abstract

Airway epithelial cells are the first line of defense against respiratory pathogens. Porcine bacterial pathogens, such as Bordetella bronchiseptica, Actinobacillus pleuropneumoniae, Glaesserella (Haemophilus) parasuis, and Pasteurella multocida, breach this barrier to lead to local or systematic infections. Here, we demonstrated that respiratory bacterial pathogen infection disrupted the airway epithelial intercellular junction protein, E-cadherin, thus contributing to impaired epithelial cell integrity. E-cadherin knocking-out in newborn pig tracheal cells via CRISPR/Cas9 editing technology confirmed that E-cadherin was sufficient to suppress the paracellular transmigration of these porcine respiratory bacterial pathogens, including G. parasuis, A. pleuropneumoniae, P. multocida, and B. bronchiseptica. The E-cadherin ectodomain cleavage by these pathogens was probably attributed to bacterial HtrA/DegQ protease, but not host HtrA1, MMP7 and ADAM10, and the prominent proteolytic activity was further confirmed by a serine-to-alanine substitution mutation in the active center of HtrA/DegQ protein. Moreover, deletion of the htrA gene in G. parasuis led to severe defects in E-cadherin ectodomain cleavage, cell adherence and paracellular transmigration in vitro, as well as bacterial breaking through the tracheal epithelial cells, systemic invasion and dissemination in vivo. This common pathogenic mechanism shared by other porcine respiratory bacterial pathogens explains how these bacterial pathogens destroy the airway epithelial cell barriers and proliferate in respiratory mucosal surface or other systemic tissues.

Keywords: Airway epithelial barrier; E-cadherin; Glaesserella parasuis; HtrA; paracellular transmigration; porcine respiratory disease complex.

Figure 1.

Porcine respiratory bacterial infection disrupted the integrity of respiratory epithelial barrier in vivo and in vitro.

Figure 2.

E-cadherin played key roles in preventing porcine respiratory bacterial transmigration of NPTr cells

Figure 3.

E-cadherin ectodomain shedding was independent of host proteases matrix metalloprotease 7 (MMP7) and a disintegrin and metalloprotease 10 (ADAM10) during porcine respiratory bacterial infection

Figure 4.

Bacterial HtrA/DegQ protein cleaved E-cadherin

Figure 5.

HtrA-mediated E-Cadherin cleavage was important for G. parasuis infection

Figure 6.

HtrA contributed to bacterial transmigration of the respiratory epithelial barrier