Gga-miR-30c-5p Suppresses Avian Reovirus (ARV) Replication by Inhibition of ARV-Induced Autophagy via Targeting ATG5.

Avian reovirus (ARV) causes viral arthritis, chronic respiratory diseases, retarded growth, and malabsorption syndrome. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression posttranscriptionally by silencing or degrading their targets, thus playing important roles in the host response to pathogenic infection. However, the role of miRNAs in host response to ARV infection is still not clear. In this study, we show that ARV infection markedly increased gga-miR-30c-5p expression in DF-1 cells and that transfection of cells with gga-miR-30c-5p inhibited ARV replication while knockdown of endogenous gga-miR-30c-5p enhanced viral growth in cells. Importantly, we identified the autophagy related 5 (ATG5), an important proautophagic protein, as a bona fide target of gga-miR-30c-5p. Transfection of DF-1 cells with gga-miR-30c-5p markedly reduced ATG5 expression accompanied with reduced conversion of ARV-induced-microtubule-associated protein 1 light chain 3 II (LC3-II) from LC3-I, an indicator of autophagy in host cell, while knockdown of endogenous gga-miR-30c-5p enhanced ATG5 expression as well as ARV-induced conversion of LC3-II, facilitating viral growth in cells. Furthermore, knockdown of ATG5 by RNA interference (RNAi) or treatment of cells with autophagy inhibitors (3-MA and wortmannin) markedly reduced ARV-induced LC3-II and syncytium formation, suppressing viral growth in cells, while overexpression of ATG5 increased ARV-induced LC3-II and syncytium formation, promoting viral growth in cells. Thus, gga-miR-30c-5p suppressed viral replication by inhibition of ARV-induced autophagy via targeting ATG5. These findings unraveled the mechanism of how host cells combat against ARV infection by self-encoded small RNA and furthered our understanding of the role of microRNAs in host response to pathogenic infection. IMPORTANCE Avian reovirus (ARV) is an important poultry pathogen causing viral arthritis, chronic respiratory diseases, and retarded growth, leading to considerable economic losses to the poultry industry across the globe. Elucidation of the pathogenesis of ARV infection is crucial to guiding the development of novel vaccines or drugs for the effective control of these diseases. Here, we investigated the role of miRNAs in host response to ARV infection. We found that infection of host cells by ARV remarkably upregulated gga-miR-30c-5p expression. Importantly, gga-miR-30c-5p suppressed ARV replication by inhibition of ARV-induced autophagy via targeting autophagy related 5 (ATG5) accompanied by suppression of virus-induced syncytium formation, thus serving as an important antivirus factor in host response against ARV infection. These findings will further our understanding of how host cells combat against ARV infection by self-encoded small RNAs and may be used as a potential target for intervening ARV infection.