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Identification and immunoregulatory role of cathepsin A in the red swamp crayfish, Procambarus clarkii

Huang, Long, Dai, Li-Shang, Wu, Ben-Li, Zhang, Ye, Chen, Jing, He, Ji-Xiang
International journal of biological macromolecules 2020 v.153 pp. 865-872
Procambarus clarkii, carboxypeptidase C, double-stranded RNA, gene expression, genes, heart, hemocytes, hepatopancreas, histidine, immunomodulation, innate immunity, invertebrates, lipopolysaccharides, messenger RNA, muscles, pathogens, peptidoglycans, polyinosinic-polycytidylic acid, reverse transcriptase polymerase chain reaction, sequence homology, serine, stomach, tissues
Cathepsins are a group of lysosomal hydrolytic enzymes, broadly distributed in animals, and regulate various physiological processes. However, the immune functions of cathepsins are poorly understood in invertebrates. Therefore, to further provide information about the importance of cathepsins in the innate immune system of crustaceans, cathepsin A from Procambarus clarkii (Pc-cathepsin A) was characterized and its distribution in different tissues was determined. The immunological functions of the Pc-cathepsin A were also evaluated. The Pc-cathepsin A showed high sequence homology to cathepsins of other species, as it contained serine and histidine active sites. Quantitative RT-PCR analysis revealed that the expression of Pc-cathepsin A was highest in the gill, gut, and the hepatopancreas, with variable amounts in the muscle, stomach, heart, and hemocytes. The mRNA expression of Pc-cathepsin A was significantly increased in hepatopancreas challenged with lipopolysaccharide (LPS), peptidoglycan (PGN), and polycytidylic acid (poly I:C). The results of an in vivo analysis revealed that Pc-cathepsin A knockdown by double-stranded RNA in P. clarkii modulated the expression of immune-pathway associated genes in hepatopancreas. Collectively, these results suggest that Pc-cathepsin A modulates innate immune responses by affecting the expression of immune-pathway associated genes, thus revealing a regulatory link between Pc-cathepsin A and immune pathways in P. clarkii, and that Pc-cathepsin A plays an essential biological role in the immune defence against microbial pathogens.