부산대학교 도서관

Cathepsins are implicated in a multitude of physiological and pathophysiological processes. The aim of the present study was to investigate the function of cathepsin L (catL) in the proteolytic network of human lung epithelial cells and its role in the regulation of apoptosis. We found that catL-deficient A549 cells as well as lung tissue extracts of catL[-/-] mice express increased amounts of single-chain cathepsin D (catD). Degradation experiments indicate that catL specifically degrades the singlechain isoform of catD. Furthermore, we found that catLdeficient cells showed increased sensitivity to apoptosis. Finally, we demonstrate that the inhibition of catD activity by pepstatin A decreased the number of apoptotic cells in catLdeficient A549 cells after anti-Fas treatment. In conclusion, catL is involved in catD processing and the accumulation of catD isoforms in catL-deficient cells is associated with increased rates of spontaneous and anti-Fas-induced apoptosis.