Dev Comp Immunol 2022 Oct 01;135:104486. doi: 10.1016/j.dci.2022.104486.

miR-137 modulates coelomocytes autophagy by targeting Atg13 in the sea cucumber Apostichopus japonicus.

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MicroRNAs (miRNAs), as important regulators of host immune responses, play an crucial position in the interaction between host and pathogen by inhibiting the target gene's transcriptional and post-transcriptional expression. A well-validated tumor suppressor, Previously, miR-137 was found to be variably expressed in the sick sea cucumber Apostichopus japonicus specimens by high-throughput sequencing. To further investigate the mechanism of miR-137 regulation of SUS, we identified Atg13 from sea cucumber by dual luciferase reporter assay and RACE (designated as AjAtg13) and was able to serve as a target gene for miR-137. The full-length cDNA of AjAtg13 is a 2197 bp fragment containing an ORF (open reading frame) of 1149 bp and encodes a total of 382 amino acid polypeptides with a predicted molecular weight of 41.7 kDa. Further expression profiling analysis showed increased mRNA levels of AjAtg13 and reduced expression levels of miR-137 in LPS-stimulated sea cucumber coelomocytes, hinting that miR-137 may negatively regulate AjAtg13. MiR-137 targets AjAtg13 through binding to the 3'UTR region by dual-luciferase reporter gene analysis. MiR-137 overexpression in coelomocytes repressed the expression of autophagy related genes, such as AjAtg13, AjLC3, at the same time, it significantly inhibited autophagy and reduced the ability to clear Vibrio splendidus. Conversely, inhibition of miR-137 significantly upregulated the expression of AjAtg13, promoted autophagy and increased clearance of V. splendidus. Subsequent interference with AjAtg13 also significantly inhibits autophagy. In summary, our results suggested that miR-137 could promote coelomocytes autophagy to restrict bacterial invasion by aiming at AjAtg13 in pathogen-stimulated sea cucumbers.

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