Molecular Cloning, Characterization, and Expression Analysis of Cathepsin A in the Chinese Giant Salamander Andrias davidianus.

Cathepsin A (CTSA) is serine carboxypeptidase, an important protease in the lysosome. In this study, the full complementary DNA (cDNA) sequence of CTSA in Chinese giant salamanders Andrias davidianus was cloned, and its sequence features were analyzed. Tissue expression patterns of CTSA in healthy and Aeromonas hydrophila-infected salamanders were also investigated. The full cDNA sequence of salamander CTSA was 1,620 base pairs in length, encoding 472 amino acids. Salamander CTSA shared high sequence identities with other vertebrates' CTSAs, ranging from 62.7% to 68.9%. In healthy salamanders, CTSA was highly expressed in spleen, followed by brain, intestine, and stomach. After A. hydrophila infection, salamander CTSA was significantly upregulated in lung, heart, muscle, and kidney; was downregulated in liver, spleen, and intestine; and exhibited no significant changes in stomach and skin, indicating that salamander CTSA might play defense roles in multiple tissues during bacterial infection. These results provide a solid basis for further study of the immune function of amphibian CTSA. Received September 18, 2016; accepted June 18, 2017.