Characterization of the inflammasome component SmASC in turbot (Scophthalmus maximus)

Apoptosis-associated speck-like protein containing a C-terminal caspase recruit domain (ASC) is an important adapter protein in the inflammasome complex that mediates inflammatory caspase activation and host innate immunity in mammals. However, the function of inflammasome components in lower vertebrate remains poorly understood. In this study, full length of SmASC was cloned from turbot (Scophthalmus maximus). Through bioinformatic analysis, we found that SmASC shares relatively high identity with ASC in bony fish. Furthermore, we found that the intact SmASC can form an oligomeric speck-like structure, while the PYD segment of SmASC can form the filamentous structure. Moreover, expression of SmASC was induced after intraperitoneal injection of Edwardsiella piscicida (E. piscicida) in vivo. To further explore the role of SmASC during infection, we constructed SmASC knockdown and overexpression models by administration of siRNA and overexpression plasmids in vivo, respectively. Expression of SmASC decreased the propagation of E. piscicida in different immune organs. In summary, our results characterize the function of SmASC in S. maximus, suggesting that the SmASC plays a critical role in turbot immune responses.