Pasteurella multocidatoxin (PMT) is an exotoxin produced by several members of the zoonotic respiratory pathogenP. multocida. The role of PMT in disrupting the mammalian respiratory barrier remains to be elucidated. In this study, we discovered that inoculation of recombinantly expressed PMT increased the permeability of the respiratory epithelial barrier in mouse and respiratory cell models. This was evidenced by a decreased expression of tight junctions (ZO-1, occludin) and adherens junctions (β-catenin, E-cadherin), as well as enhanced cytoskeletal rearrangement. In mechanism, we demonstrated that PMT inoculation induced cytoplasmic Ca2+inflow, leading to an imbalance of cellular Ca2+homeostasis and endoplasmic reticulum stress. This process further stimulated the RhoA/ROCK signaling, promoting cytoskeletal rearrangement and reducing the expression of tight junctions and adherens junctions. Notably, the T-type voltage-gated Ca2+channel CaV3.1 was found to participate in PMT-induced cytoplasmic Ca2+inflow. Knocking out CaV3.1 significantly reduced the cytotoxicity induced by PMT on swine respiratory epithelial cells and mitigated cytoplasmic Ca2+inflow stimulated by PMT. Further analysis identified Ser (aa92), Glu (aa155), Tyr (aa167), and Leu (aa448) as crucial sites utilized by PMT to interact with CaV3.1. These findings suggest CaV3.1 serves as an important host receptor of PMT and contributes to PMT-induced respiratory epithelial barrier disruption.
Importance
PMT is a significant toxin produced by the zoonotic respiratory pathogenP. multocida, yet little is known about its pathogenesis beyond causing progressive atrophic rhinitis in pigs. In our study, we have discovered that PMT has the capacity to disrupt the integrity of the mammalian respiratory epithelial barrier. This disruption involves an imbalance in cellular Ca2+homeostasis, endoplasmic reticulum stress, and activation of the RhoA/ROCK signaling pathway induced by PMT. Importantly, we have identified CaV3.1 as a pivotal receptor that plays a crucial role in the pathogenic effects of PMT. Our findings highlight the potential of CaV3.1 as a target for intervention strategies aimed at combating the detrimental effects of PMT.
