Pyroptolysins are versatile, sterol-sensing bacterial toxins

Abstract

Gasdermin pores mediate cellular self-sacrifice for the immune defense pyroptosis. Here we describe how the gasdermin fold was repurposed during evolution into a membrane targeting bacterial toxin. These proteins, which we call pyroptolysins, are chimeras of gasdermins and cholesterol-dependent cytolysins. Like the cytolysins, pyroptolysins are active on cholesterol-rich membranes, but unlike cytolysins, they are poorly active on mammalian cells. Structural snapshots of the pyroptolysins confirm their dual homology and reveal pre-organized complexes primed for membrane insertion. Unexpectedly, we found the pyroptolysins to be active in vitro and in vivo on membranes with remarkably low sterol content, displaying insecticidal activity. Our results establish the gasdermin fold as a versatile pore-forming scaffold, capable of inducing cell death from the inside and the outside of cells.