Cathepsin B-like and hemoglobin-type cysteine proteases: Stage-specific gene expression in Angiostrongy cantonensis

Three cysteine protease genes, cathepsin B-like enzyme gene 1, 2 (AC-cathB-1, AC-cathB-2) and hemoglobin-type cysteine protease gene (AC-hem) were isolated and described from Angiostrongylus cantonensis adult. The deduced amino acid sequence of Ac-cathB-1 and AC-cathB-2 contain all of the conserved regions of cathepsin B. AC-cathB-2 is similar to a host intrusion-related cysteine protease B from Parelaphostrongylus tenuis, and the AC-hem shares high similarity to legumain from Haemonchus contortus. AC-cathB-1 was expressed significantly higher in L1 as compared with AC-hem, the AC-cathB-2 followed; AC-cathB-2 transcripts in L3 were found increased rapidly and obviously abundant, suggesting that AC-cathB-1 and AC-cathB-2 may play an important role in intermediate and final host invasion, separately. The cysteine protease genes were more or less expressed in adult stage excepted for AC-cathB-2. As the AC-cathB-1 and AC-hem highly expressed in adult worms, suggesting AC-hem may activate AC-cathB-1 which involved in the host invasion and feeding process.

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► Two cathepsin B-like and one hemoglobin-type cysteine protease gene was cloned.
► Varied transcription patterns of the proteases were observed in different stages.
► AC-cathBs play an important role in host invasion; AC-hem activated AC-cathB-1.
► AC-cathB-2 is similar to cathB of Parelaphostrongylus tenuis, AC-hem resemble legumain of Haemonchus contortus.
► Ac-cathBs contain all of the conserved regions of cathepsin B from other parasites.