Identification and characterization of an HtrA sheddase produced byCoxiella burnetii

Abstract

AbstractHaving previously shown that soluble E-cadherin (sE-cad) is found in sera of Q fever patients, and that infection of BeWo cells byC. burnetiileads to modulation of the E-cad/β-cat pathway, our purpose was to identify which sheddase(s) might catalyze the cleavage of E-cad. Here, we searched for a direct mechanism of cleavage initiated by the bacterium itself, assuming the possible synthesis of a sheddase encoded in the genome ofC. burnetiior an indirect mechanism based on the activation of a human sheddase. Using a straightforward bioinformatics approach to scan the complete genomes of four laboratory strains ofC. burnetii, we demonstrate thatC. burnetiiencodes a 451 amino acid sheddase (CbHtrA) belonging to the HtrA family and differently expressed according to the bacterial virulence. An artificial CbHtrA gene (CoxbHtrA) was expressed and the CoxbHtrA recombinant protein was found to have sheddase activity. We also found evidence that theC. burnetiiinfection triggers an over-induction of the human HuHtrA gene expression. Finally, we demonstrate that cleavage of E-cad by CoxbHtrA on THP-1-cells leads to an M2 polarization of the target cells and the induction of their secretion of IL-10, which ‘disarms’ the target cells and improvesC. burnetiireplication. Taken together these results demonstrate that the genome ofC.burnetiiencodes a functional HtrA sheddase and establish a link between the HtrA sheddase-induced cleavage of E-cad, the M2 polarization of the target cells and their secretion of IL-10, and the intracellular replication ofC. burnetii.