Nuclear localization of procathepsin L/MEP in ras-transformed mouse fibroblasts.

It has been well-documented that secretion of procathepsin L is enhanced in ras-oncogene-transformed cells. In the present study, intracellular localization of cathepsin L was investigated by cell fractionation using Nonidet P-40 followed by immunoblot analysis. The results showed that a significant amount of procathepsin L was detectable in the nuclear fraction of Ha-ras, Ki-ras- and erbB2-transformed NIH3T3 mouse fibroblasts while procathepsin L was detected only in the cytoplasmic fraction of NIH3T3 cells and v-mos-transformed cells. These results suggest that the processing and translocation of cathepsin L are seriously impeded in ras- and erbB2-transformed cells.