Fig. 9

Proteolysis of basement membrane HSPG by cathepsin S. (A) Two micrograms of native proteoglycan was incubated with 300 ng or 30 ng of human recombinant cathepsin S for 150 min at acidic pH and analyzed as described in Materials and Methods. Lane 1, HSPG incubated with 300 ng cathepsin S and 5 µM E64 included in the reaction mixture; lane 2, HSPG incubated with 30 ng of cathepsin S; lane 3 HSPG incubated with 300 ng cathepsin S. (B) Ten nanograms of recombinant cathepsin S was incubated with 1 µg of HSPG (1:1000 substrate: enzyme ratio) for 1.5 hr in sodium phosphate buffer, pH 6.5 or pH 7.5, containing 50 µM E64. Mock digestion contained no cathepsin S. Samples were analyzed by silver staining, gels were scanned and desensitized as described. The results represent % control.