IDENTIFICATION OF SUBSTRATE PROTEINS FOR CATHEPSIN-L THAT ARE SELECTIVELY HYDROLYZED DURING THE DIFFERENTIATION OF IMAGINAL DISCS OF SARCOPHAGA-PEREGRINA

Previously, we showed that cathepsin L is essential for the differenti ation of imaginal discs of the flesh fly [Homma, K. & Natori, S. (1994 ) J. Biol. Chem. 269, 15 258-15 264]. We have now identified imaginal disc proteins that are susceptible to digestion by cathepsin L and sho wed that they are selectively hydrolyzed during imaginal disc differen tiation. Two of these proteins, with molecular masses of 210 and 200 k Da, were further characterized. Immunofluorescence studies suggested t hat they were intrinsic components of the basement membranes of variou s tissues. They were selectively hydrolyzed at the elongation stage of imaginal leg disc differentiation. Western blotting of embryos at var ious developmental stages showed that these proteins were only detecte d at the end of embryogenesis.