Identification of an alternative splicing variant of cathepsin C/dipeptidyl-peptidase I.

Cathepsin C/dipeptidyl-peptidase I is a papain-like lysosomal cysteine proteinase implicated in the processing of various proenzymes to their active forms. In this study, we identified an alternative splicing variant of cathepsin C in both human and mouse species for the first time. The variant messenger RNA (mRNA) encodes 137 amino acids corresponding to the first and second exons, followed by additional 31 amino acids. The two newly recognized exons are located in the former intron 2. The variant mRNA is distributed ubiquitously, but predominantly in kidney, placenta, and lymph nodes. Furthermore, both interleukin 4 (IL-4) and IL-13, but not a range of cytokines induce expression of the variant in bronchial epithelial cells. These results indicate that the variant may play a role in regulating the biological activities of cathepsin C, involved in the pathogenesis of bronchial asthma.