| Summary: | Autophagy is a cytoprotective mechanism triggered in response to adverse environmental conditions. Herein, we investigated the autophagy process in the oriental river prawn (<i>Macrobrachium nipponense</i>) following hypoxia. Full-length cDNAs encoding autophagy-related genes (ATGs) <i>ATG3</i>, <i>ATG4B</i>, <i>ATG5</i>, and <i>ATG9A</i> were cloned, and transcription following hypoxia was explored in different tissues and developmental stages. The <i>ATG3</i>, <i>ATG4B</i>, <i>ATG5</i>, and <i>ATG9A</i> cDNAs include open reading frames encoding proteins of 319, 264, 268, and 828 amino acids, respectively. The four <i>M. nipponense</i> proteins clustered separately from vertebrate homologs in phylogenetic analysis. All four mRNAs were expressed in various tissues, with highest levels in brain and hepatopancreas. Hypoxia up-regulated all four mRNAs in a time-dependent manner. Thus, these genes may contribute to autophagy-based responses against hypoxia in <i>M. nipponense</i>. Biochemical analysis revealed that hypoxia stimulated anaerobic metabolism in the brain tissue. Furthermore, in situ hybridization experiments revealed that <i>ATG4B</i> was mainly expressed in the secretory and astrocyte cells of the brain. Silencing of <i>ATG4B</i> down-regulated <i>ATG8</i> and decreased cell viability in juvenile prawn brains following hypoxia. Thus, autophagy is an adaptive response protecting against hypoxia in <i>M. nipponense</i> and possibly other crustaceans. Recombinant <i>MnATG4B</i> could interact with recombinant <i>MnATG8</i>, but the <i>GST</i> protein could not bind to <i>MnATG8</i>. These findings provide us with a better understanding of the fundamental mechanisms of autophagy in prawns.
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