Multigene family of cathepsin B and cathepsin F cysteine proteases of Clonorchis sinensis

초록

Cysteine proteases of trematode parasites have attracted considerable attention for their essential roles in parasite physiology as well as in hostparasite interactions through their modulation of various pathobiological events, including host tissue invasion, nutrient uptake and host immune evasion. Cysteine protease activities have been identified in several life stages of Clonorchis sinensis, the Chinese liver fluke which causes clonorchiasis in humans, but highly limited information is currently available for in-depth characterization of the enzymes. In this study, we described multigene family of cathepsin B and F-like cysteine proteases of the parasite. Genetic analysis revealed that at least 4 and 11 genes encoding cathepsin B and F cysteine proteases, respectively, were identified in C. sinensis. Each gene shared highly conserved sequence characteristics found in cathepsin B and F cysteine proteases and showed high sequence identity each other. Two-dimensional gel electrophoresis analysis also confirmed the presence of multiple cathepsin B and F cysteine proteases in adult C. sinensis. Sequence and immunoblot analyses showed that most of the gene products are secreted proteins. Comparative analysis of expression patterns of the enzymes in various developmental stages of the parasite revealed that they showed similar expression patterns in the life cycle of the parasite. Our results, taken together, provide a framework for designing experimental studies of the characterization of each enzyme in the parasite.