SpH‐protease exists in Caco‐2 cells

We have described a 60 kDa nuclear cysteine protease that degrades sperm histones during male chromatin remodeling after fertilization in sea urchins (SpH protease). This enzyme was shown to be localized in the mitotic furrow and to be involved in cell cycle control in sea urchin embryos. The N terminal sequence and the gene encoding this protease have homology with human cathepsin L family; therefore we investigated with antibodies raised against the sea urchins protease if a similar protease is present in Caco‐2 cells. Among Caco 2 chromosomal proteins obtained from confluent cell cultures, we found by Western blots, two bands migrating at 60 and 100 kDa in SDS/PAGE. We have also used these anti SpH protease antibodies to immunolocalize this protease in the intracellular context. This protease in mitotic cells localize on the mitotic furrow and remains in the nucleus in binuclear cells. On the other hand, when inhibitors of cysteine‐proteasas were used in different phases of the cell cycle we observed a disorganization of the mitotic spindle and an alteration in the localization of the protease during the S phase affecting DNA replication. Our results demonstrate that in Caco 2 cells exist a variant of cathepsin L protease that exhibits a similar localization to that was described for embryos of sea urchin, indicating a putative rol in cell proliferation. FONDECYT 11070067.