Exosomal SpFlotillin-1 participates in resistance to Vibrio parahemolyticus infection in mud crab (Scylla paramamosain)

Exosomes have been considered anti-microbial immune factors in animals (including aquatic animals). However, the relationship between exosomal proteins and immune responses during bacterial infection has not been addressed. Flotillin-1 has previously been shown to enrich plasma membrane which implicates in cellular processes, including signal transduction, membrane trafficking, and molecular sorting. In this study, SpFlotillin-1 was cloned and characterized from mud crab (Scylla paramamosain). SpFlotillin-1 was found to be up-regulated in the hemocytes of mud crabs after infecting with V. parahaemolyticus. RNAi knockdown of SpFlotillin-1 showed capacity in suppressing phagocytosis and reducing the expression of antimicrobial peptides (AMPs) but increasing the ROS production in hemocytes. Furthermore, SpFlotillin-1 densely packaged in the exosomes can regulate the phagocytosis, expression of AMPs through MAPK and NF-kappa B pathway, and production of ROS, eventually activating the immune response to bacterial infection in mud crabs. Taken together, the results of this study provide a new finding on the mechanism that exosomal SpFlotillin-1 may participate in the V. parahaemolyticus infection through the regulation of phagocytosis and activation of AMP synthesis in mud crabs.

Automated summary

This study reveals the involvement of exosomal protein SpFlotillin-1 in regulating immune responses during bacterial infection in mud crabs. Up-regulation of SpFlotillin-1 inhibits phagocytosis and reduces antimicrobial peptide expression, while increasing ROS production. Moreover, SpFlotillin-1 densely packaged in exosomes modulates phagocytosis, AMP expression, and ROS production through the MAPK and NF-kappa B pathways, ultimately activating the immune response to bacterial infection in mud crabs.