Gasdermin (GSDM) is a family of pore-forming proteins that induce pyroptosis. To date, the origin and evolution of GSDM in Metazoa remain elusive. Here, we found that GSDM emerged early in Placozoa but is absent in a large number of invertebrates. In the lower vertebrate, fish, three types of GSDME, i.e., GSDMEa, GSDMEb, and a previously unreported type (designated GSDMEc), were idenitied. Evolutionarily, the three GSDMEs are distinctly separated: GSDMEa is closely related to tetrapod GSDME; GSDMEb exists exclusively in fish; GSDMEc forms the lineage root of tetrapod GSDMA/B/C/D. GSDMEc shares conserved genomic features with and is probably the prototype of GSDMA, which we found existing in all tetrapod classes. GSDMEc displays fast evolutionary dynamics, likely as a result of genomic transposition. A cross-metazoan analysis of GSDME revealed that GSDMEa shares a conserved caspase recognition motif with the GSDME of tetrapods and cnidarians, whereas GSDMEb has a unique caspase recognition motif similar to that of mammalian GSDMD, and GSDMEc exhibits no apparent caspase recognition motif. Through functional test, four highly conserved residues in vertebrate GSDME proved to be essential to auto-inhibition. Together our results provide new insights into the origin, evolution, and function of metazoan GSDMs.

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Cleavage of gasdermin, typically by caspase (CASP), is required for pyroptosis. In human, CASP3 and CASP7 recognize the same consensus motif DxxD, which is present in gasdermin E (GSDME), but only CASP3 cleaves GSDME. The underlying mechanism of this observation is unclear. In this study, we identified a pyroptotic pufferfish GSDME that was specifically cleaved by both pufferfish CASP3/7 and human CASP3/7. Domain swapping between pufferfish and human CASP/GSDME showed that the GSDME C-terminus and the CASP7 p10 subunit determined the cleavability of GSDME by CASP7. p10 contains a key residue that governs CASP7 substrate discrimination. This residue is highly conserved in vertebrate CASP3 and in most vertebrate (except mammalian) CASP7. In mammals, the key residue is conserved in non-primate (e.g., mouse) but not in primate. However, mouse CASP7 cleaved human GSDME but not mouse GSDME. These findings revealed the molecular mechanism of CASP7 substrate discrimination that underlies the evolutionary divergence of CASP3/7-mediated GSDME activation in vertebrate.