LRSAM1 mediated the degradation of intracellular Vibrio through the ubiquitination-autophagy-lysosome pathway in oyster

The leucine rich repeat and sterile alpha motif containing 1 (LRSAM1) as E3 ligase recognizes bacteria and generates a ubiquitin signal to initiate the autophagy process. In the present study, LRSAM1 was identified from the Pacific oyster Crassostrea gigas (designed as CgLRSAM1), which was able to recognize various pathogen-associated molecular patterns and bacteria and directly ubiquitinate Vibrio splendidus. V. splendidus was co-localized with CgLRSAM1 and ubiquitin after invading haemocytes, and the ubiquitinated V. splendidus was then internalized into haemocyte lysosomes by p62-LC3-mediated autophagy. In haemocytes of CgLRSAM1-RNAi oysters, the activation of CgLC3 was enhanced after V. splendidus stimulation. While the co-localization values of V. splendidus with ubiquitin, CgLC3 and lysosomes all decreased significantly after V. splendidus stimulation. These results indicated that CgLRSAM1 functioned as E3 ligase responsible for anti-Vibrio-associated ubiquitination and regulated the degradation of bacteria through the ubiquitination-autophagy-lysosome pathway.