Interaction of matrix metalloprotease-9 and Zpx in Cronobacter turicensis LMG 23827T mediated infections in the zebrafish model

Bacteria belonging to the genus Cronobacter (C.) have been recognized as causative agents of life-threatening systemic infections primarily in premature and low-birth weight neonates. Validation of putative bacterial virulence components as well as host factors potentially involved in the response to infection have been hampered in the past by the availability of suitable neonatal animal models. In the current study the zebrafish embryo model was employed to study the interaction of the zinc metalloprotease Zpx present in C. turicensis LMG23827T , with the eukaryotic MMP-9, a protease that functions to cleave extracellular matrix gelatin and collagen. Cleavage and activation of the human recombinant pro-MMP9 by zpx expressing C. turicensis cells was demonstrated in vitro and the presence and increase of the processed, active form of zebrafish pro-MMP-9 was shown in vivo. We provided evidence that Zpx induces the expression of the mmp-9 but also increases the levels of processed MMP-9 during infection. The involvement of the MMP-9 in induction of the expression of the bacterial Zpx was shown in zebrafish mmp-9 morphant experiments. This study identified MMP-9 as a substrate of Zpx and demonstrated yet undescribed mutual cross-talk between these two proteases in infections mediated by C. turicensis LMG23827T .