Autophagy is regulated by a variety of autophagy related genes (ATG), among them, ATG4 is a highly specific protease that is critical to autophagy. The purpose of this study was to investigate the role of the ATG4 response to Palmitic acid (PA) and their relationships with Endoplasmic reticulum (ER) stress in grass carp. In the present study, four ATG4 paralogs from grass carp were identified and analyzed. The open reading frames of ATG4A, ATG4B, ATG4C, and ATG4D were 1212, 1194, 1429, and 1482 bp long, encoding 403, 394, 475, and 493 amino acids, respectively. Secondly, the mRNA levels of ATG4 paralogs transcripts in 13 tissues of grass carp were analyzed to determine the tissue distribution. The highest (p < 0.05) expression of ATG4A, ATG4B, ATG4C, and ATG4D were found in the heart, white muscle, brain, and liver, respectively. Moreover, after stimulation with PA, the expression of the four ATG4 paralogs in Ctenopharyngodon idellus kidney (CIK) cells were significantly up-regulated (p < 0.05). Inhibiting ER stress with 4 phenylbutyrate (4-PBA) significantly reduced PA-induced autophagy in CIK cells, while the expression of PA-induced ATG4 paralogs were significantly decreased (p < 0.05), suggesting that ATG4 is involved in PA-induced autophagy. We also demonstrated that PA could induced inflammation-related genes in CIK cells, and the PA-induced inflammation were alleviated by 4-PBA. Moreover, overexpression ATG4C induced ER stress and decreased inflammation. Taken together, these results demonstrate for the first time that inhibition of ER stress could reduce PA-induced expression of ATG4 paralogs and some inflammation-related genes.

自噬受多种自噬相关基因（ATG）的调控，其中ATG4是高度特异性的蛋白酶，对自噬至关重要。这项研究的目的是调查ATG4对棕榈酸（PA）的反应及其与草鱼内质网（ER）胁迫的关系。在本研究中，鉴定并分析了草鱼的四个ATG4旁系同源物。ATG4A，ATG4B，ATG4C和ATG4D的开放阅读框长1212、1194、1429和1482 bp，分别编码403、394、475和493个氨基酸。其次，分析了草鱼的13种组织中ATG4旁系转录物的mRNA水平，以确定其分布。最高（p （<0.05）ATG4A，ATG4B，ATG4C和ATG4D的表达分别出现在心脏，白肌，大脑和肝脏中。此外，在用PA刺激后，在Ctenopharyngodon idellus肾（CIK）细胞中四个ATG4旁系同源物的表达显着上调（p  <0.05）。用4苯基丁酸酯（4-PBA）抑制ER应激可显着降低PA诱导的CIK细胞自噬，而PA诱导的ATG4旁系同源物的表达则显着降低（p <0.05），表明ATG4参与了PA诱导的自噬。我们还证明了PA可以诱导CIK细胞中炎症相关的基因，并且4-PBA可以减轻PA诱导的炎症。此外，过表达的ATG4C诱导ER应激并减少炎症。综上所述，这些结果首次证明了抑制内质网应激可以减少PA诱导的ATG4旁系同源物和一些炎症相关基因的表达。