Spotted seabass Lateolabrax maculatus GSDMEa: a pyroptosis executor activated by CASP3/7 during bacterial infection.

Abstract

Pyroptosis is a lytic form of programmed cell death executed by gasdermin, which is activated by caspase (CASP) cleavage. Pyroptosis plays a pivotal role in host defense against bacterial infection. Spotted seabass Lateolabrax maculatus, one of the major aquaculture fish in China, is vulnerable to the bacterial pathogen Photobacterium damselae subsp. piscicida (PDP), which causes significant economic losses due to high mortality outbreaks. To date, no study on L. maculatus gasdermin has been documented, and the role of gasdermin in bacterial infection is unclear. In this study, we identified from L. maculatus two gasdermin E (GSDME) (designated LmGSDMEa and LmGSDMEb, respectively) and three CASPs (designated LmCASP3, 6, and 7, respectively), and characterized their biological activities. LmCASP3 and LmCASP7, but not LmCASP6, directly induced apoptosis. LmCASP3/7 specifically cleaved LmGSDMEa at theNTVDsite, generating an active N-terminal fragment (NT265) that converted apoptosis into pyroptosis. Unlike LmGSDMEa, LmGSDMEb could not trigger pyroptosis. When spotted seabass were challenged with PDP, the expression levels of LmCASP3/7, LmGSDMEa, and pyroptosis-associated inflammatory cytokines were upregulated in fish tissues. Consistently, PDP infection promoted the production and activation of LmGSDMEa and LmCASP3/7 in spotted seabass macrophages, resulting in pyroptotic cell death. Collectively, this study revealed the activation and regulation mechanism of GSDMEa-mediated pyroptosis in spotted seabass, and provided new insights into the role of pyroptosis in fish immunity during bacterial infection.