Clostridium perfringens α-Toxin Impairs Lipid Raft Integrity in Neutrophils

Clostridium perfringens type A, a Gram-positive, anaerobic bacterium, causes gas gangrene. Recently, we reported that C. perfringens alpha-toxin blocked neutrophil differentiation in an enzyme activity-dependent manner to impair host innate immunity, which should be crucial for the pathogenesis of C. perfringens. However, the detailed mechanism remains unclear. Lipid rafts have been reported to be platforms for signaling molecules involved in the regulation of cell differentiation in many different cell types. In this study, we found that cell surface expression of a lipid raft marker, GM1 ganglioside, decreased in association with neutrophil differentiation by flow cytometry analysis and morphological observation. In vitro treatment of isolated mouse bone marrow cells with alpha-toxin or an alpha-toxin variant lacking phospholipase C and sphingomyelinase activities revealed that alpha-toxin increased the cell surface expression of GM1 ganglioside in an enzyme activity-dependent manner. C. perfringens infection also increased GM1 ganglioside levels in bone marrow myeloid cells. Moreover, treatment of bone marrow cells with methyl-beta-cyclodextrin, a lipid raft disrupting agent, impaired neutrophil differentiation. Together, our results suggest that the integrity of lipid rafts should be properly maintained during granulopoiesis, and alpha-toxin might perturb lipid raft integrity leading to the impairment of neutrophil differentiation.