Grass carp ATG5 and ATG12 promote autophagy but down-regulate the transcriptional expression levels of IFN-I signaling pathway

Abstract

Autophagy is an essential and conserved process that plays an important role in physiological homeostasis, adaptive response to stress and the immune response. Autophagy-related proteins (ATGs) are key components of the autophagic machinery. In the study, grass carp (Ctenopharyngodon idella) autophagy-related gene 5 (ATG5) and 12 (ATG12) were identified. In the gill and intestine, ATG5 and ATG12 were highly expressed, but after grass carp reovirus (GCRV) infection, they were decreased significantly. In Ctenopharyngodon idella kidney (CIK) cells, the sharp variation of ATG5 and ATG12 expression was observed after poly(I:C) infection. Subcellular localisation showed that ATG5 and ATG12 were evenly distributed in the cytoplasm and nucleus. However, the interaction between ATG5 and ATG12 was only found in cytoplasm in both 293T cells and CIK cells. In addition, the overexpression of ATG5 or ATG12 in 293T cells showed enhanced autophagy, and autophagic process was facilitated when ATG5 and ATG12 were simultaneously overexpressed. Dual-luciferase activity assay indicated that both ATG5 and ATG12 remarkably suppressed the promoter activity of IRF3, IRF7, and IFN-I. Further, ATG5 and ATG12 conjugate showed far stronger inhibitory affection on the expression of IFN-I than either ATG5 or ATG12 in response to poly(I:C) or GCRV infection. Taken together, the results demonstrate that grass carp ATG5 and ATG12 play an important role in innate immunity and autophagy.