The molecular mechanism and evolutionary divergence of caspase 3/7-regulated gasdermin E activation

Abstract

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.