Phospholipid Hydrolysis Caused by Clostridium perfringens α-Toxin Facilitates the Targeting of Perfringolysin O to Membrane Bilayers

Clostridium perfringens causes gas gangrene and gastrointestinal disease in humans. These pathologies are mediated by potent extracellular protein toxins, particularly alpha-toxin and perfringolysin O (PFO). While alpha-toxin hydrolyzes phosphatidylcholine and sphingomyelin, PFO forms large transmembrane pores on cholesterol-containing membranes. It has been suggested that the ability of PFO to perforate the membrane of target cells is dictated by how much free cholesterol molecules are present. Given that C. perfringens alpha-toxin cleaves the phosphocholine headgroup of phosphatidylcholine, we reasoned that alpha-toxin may increase the number of free cholesterol molecules in the membrane. Our present studies reveal that alpha-toxin action on membrane bilayers facilitates the PFO-cholesterol interaction as evidenced by a reduction in the amount of cholesterol required in the membrane for PFO binding and pore formation. These studies suggest a mechanism for the concerted action of a-toxin and PFO during C. perfringens pathogenesis.