Seneca Valley Virus 3C Protease Induces Pyroptosis by Directly Cleaving Porcine Gasdermin D

Abstract

Seneca Valley virus (SVV), a newly emerging virus belonging to the <i>Picornaviridae</i> family, has caused vesicular disease in the swine industry. However, the molecular mechanism of viral pathogenesis remains poorly understood. This study revealed that SVV infection could induce pyroptosis in SK6 cells in a caspase-dependent and -independent manner. SVV may inhibit caspase-1 activation at late infection because of 3C^pro cleavage of NLRP3, which counteracted pyroptosis activation. Further study showed that 3C^pro targeted porcine gasdermin D (pGSDMD) for cleavage through its protease activity. 3C^pro cleaved porcine GSDMD (pGSDMD) at two sites, glutamine 193 (Q193) and glutamine 277 (Q277), and Q277 was close to the caspase-1-induced pGSDMD cleavage site. pGSDMD_1-277 triggered cell death, which was similar to N-terminal fragment produced by caspase-1 cleavage of pGSDMD, and other fragments exhibited no significant inhibitory effects on cellular activity. Ectopic expression of pGSDMD converted 3C^pro-induced apoptosis to pyroptosis in 293T cells. Interestingly, 3C^pro did not cleave mouse GSDMD or human GSDMD. And, both pGSDMD and pGSDMD_1-277 exhibited bactericidal activities in vivo. Nevertheless, pGSDMD cannot kill bacteria in vitro. Taken together, our results reveal a novel pyroptosis activation manner produced by viral protease cleavage of pGSDMD, which may provide an important insight into the pathogenesis of SVV and cancer therapy.