Title: The chaperone PrsA2 regulates the secretion and folding of listeriolysin O toxin during Listeria monocytogenes infection
Abstract:
Pathogenic bacteria rely on secreted virulence factors to cause disease in susceptible hosts. However, the mechanisms underlying the folding, activation, and regulation of these factors in Gram-positive bacteria after membrane translocation remains largely unknown. Using proteomics, we identified that several proteins including the listeriolysin O toxin (LLO) are dependent on the peptidyl-prolyl isomerase (PPIase) chaperone PrsA2 for secretion. We followed with phenotypic, biochemical, biophysical assays, and computational analyses to examine the regulation of the secreted virulence factor, LLO and its interaction with the Gram-positive secretion chaperone PrsA2 from the bacterial pathogen Listeria monocytogenes (Lm). A critical facet of Lm virulence is bacterial internalization by host cells and the subsequent action of the cholesterol dependent pore-forming toxin, LLO, which enables bacterial escape from the host cell phagosome. Additionally, Lm relies upon the extracellular membrane-anchored chaperone PrsA2 to assist in folding virulence factors such as LLO as they are secreted. As a Gram-positive organism, the space between the Lm cell membrane and the cell wall is solvent exposed. Therefore, we hypothesized that the drop from neutral to acidic pH as the pathogen is internalized into a phagosome may be a primary step in regulating the interaction of the chaperone PrsA2 with the virulence factor LLO. Here, we provide evidence that PrsA2 physically interacts with LLO in a pH-dependent manner. Supporting this, we also identify molecular features of PrsA2 and LLO that are required for their interaction and ultimately the proper folding and activity of LLO. Additionally, protein-complex modelling suggests that the PrsA2 chaperone interacts with LLO via its cholesterol binding domain. These findings highlight a new mechanism by which a Gram-positive secretion chaperone regulates the secretion and folding of a pore-forming toxin under conditions relevant to host cell infection.
Cahoon Lab
Friday, December 1st, 2023
12:00PM
Langley A219B