Irreversible versus repairable membrane poration: differences in permeabilization elicited by Bordetella Adenylate Cyclase Toxin and its hemolysin domain in macrophages.

Rapid plasma membrane repair in response to pore-forming toxins is crucial for cell survival, but the molecular mechanisms employed by eukaryotic nucleated cells to maintain membrane integrity and the specificities of such pathways remain poorly understood. Here, we have explored the permeabilization elicited by the Bordetella pertussis adenylate cyclase toxin, a 200-kDa protein toxin with α-helical pore-forming domain that forms pores of tunable size, and evaluated the response of target macrophages to such toxin poration. We show here that the response and the fate of target macrophages depend on toxin pore width. We find that the toxin's hemolysin moiety induces a transient membrane permeabilization by forming wide enough pores allowing Ca influx into the target cell cytosol. This activates a Ca -dependent cellular response involving exocytosis and endocytosis steps eliminating toxin pores and restoring membrane integrity. In contrast, the full-length native toxin, at low concentrations, forms very small pores that cause insidious perturbation of cell ion homeostasis that escapes control by the macrophage membrane repair response, eventually leading to cell death. Our data reveal that permeability to Ca and ATP are key elements in the membrane repair pathway for eliminating α-helical pores of bacterial origin.