Cathepsin D belongs to aspartic protease family, produced in the rough endoplasmic reticulum, and then transported to lysosomes, where it participates in various physiological processes. Despite its importance, only a few reports available on the functional role of cathepsin D in crustaceans. Herein, we cloned a cDNA fragment of cathepsin D from the hepatopancreas of the red swamp crayfish, Procambarus clarkii (Pc-cathepsin D) for the first time. It included 1158 base pairs open reading frame, encoding a protein of 385 amino acids. Multiple alignment analysis confirmed the presence of aspartic proteinase active sites and N glycosylation sites. Pc-cathepsin D mRNA expression was high in the gills followed by gut, heart, hepatopancreas of P. clarkii. At different time points post-infection with lipopolysaccharides, peptidoglycan, or polyinosinic polycytidylic acid, Pc-cathepsin D mRNA expression significantly enhanced compared with the control group. Knockdown of the Pc-cathepsin D by double-stranded RNA, strikingly, changed the expression of all the tested P. clarkii immune-associated genes, including Pc-Toll, Pc-lectin, Pc-cactus, Pc-anti-lipopolysaccharide factor, Pc-phospholipase, and Pc-sptzale. Altogether, these results suggest that Pc-cathepsin D is needed to confer innate immunity against microbial pathogens by modulating the expression of crucial transcripts that encode immune-associated genes.

组织蛋白酶 D 属于天冬氨酸蛋白酶家族，在粗面内质网中产生，然后转运至溶酶体，参与各种生理过程。尽管它很重要，但关于组织蛋白酶 D 在甲壳类动物中的功能作用的报道很少。在此，我们首次从红沼泽小龙虾Procambarus clarkii ( Pc-cathepsin D )的肝胰腺中克隆了组织蛋白酶 D 的 cDNA 片段。它包括1158个碱基对的开放阅读框，编码385个氨基酸的蛋白质。多重比对分析证实了天冬氨酸蛋白酶活性位点和 N 糖基化位点的存在。Pc-cathepsin D mRNA 在鳃中高表达，其次是肠道、心脏、肝胰腺克拉克假单胞菌。在脂多糖、肽聚糖或聚肌苷多胞苷酸感染后的不同时间点，与对照组相比，Pc-cathepsin D mRNA的表达显着增强。双链 RNA对Pc-组织蛋白酶 D的敲低，惊人地改变了所有测试的克拉氏假单胞菌免疫相关基因的表达，包括 Pc-Toll、Pc-凝集素、Pc-仙人掌、Pc-抗脂多糖因子、 Pc-磷脂酶和 Pc-sptzale。总之，这些结果表明需要Pc-组织蛋白酶 D通过调节编码免疫相关基因的关键转录物的表达来赋予针对微生物病原体的先天免疫。