Pyroptosis is a form of programmed cell death initiated by caspase (CASP)-dependent activation of gasdermin and plays a crucial role in the defense against bacterial infection. Large yellow croaker ( Larimichthys crocea ) is an important aquaculture fish that is susceptible to a number of bacterial pathogens, including Photobacterium damselae subsp. piscicida (PDP). Currently, the working mechanism of L. crocea gasdermin-mediated pyroptosis and its role in bacterial infection remain to be elucidated. In this study, we examined the biological activity of two L. crocea gasdermin E (GSDME) orthologues, LcGSDMEa and LcGSDMEb, and the regulation mechanism of these GSDMEs by CASPs. Seven L . crocea CASPs (LcCASPs) were identified and classified as LcCASP1, 2, 3, 6, 7, 8, and 9. LcGSDMEa was cleaved specifically by LcCASP3, 6, and 7. LcCASP3/7 cleaved LcGSDMEa at 262 DAVD 265 , yielding an N-terminal fragment (NT) named NT265. LcCASP6 cleaved, in a decreasing preference, at 262 DAVD 265 , 246 IESD 249, and 203 IEID 206 , which yielded different NTs named NT265, NT249, and NT206, respectively. NT265 and NT249, but not NT206, executed pyroptosis. LcGSDMEb was cleaved by LcCASP1/3/7/9 at 243 FEVD 246 , and the resulting products were unable to induce pyroptosis. PDP infection upregulated the expressions of LcGSDMEa and LcCASP3/6/7 in large yellow croaker cells and induced LcGSDMEa activation and pyroptosis. Inhibition of LcCASP7 significantly attenuated PDP-induced large yellow croaker cell death. Taken together, these results revealed the caspase-mediated regulatory mechanism of GSDMEa and GSDMEb in large yellow croaker and provided new insights into the role of GSDME-triggered pyroptosis in bacterial infection in fish. • LcGSDMEa, but not LcGSDMEb, is an efficient pyroptosis inducer. • LcCASP3/7 cleave LcGSDMEa to generate NT265 that executes pyroptosis. • LcCASP6 cleaves LcGSDMEa to yield pyroptotic NT265/NT249 and non-pyroptotic NT206. • LcGSDMEa mediates LcCASP7-dependent pyroptosis during bacterial infection.
Wang et al. (Sun,) studied this question.