Peptide-Modulated Activity Enhancement of Acidic Protease Cathepsin E at Neutral pH
Figure 3
Biological effects of a paired peptide on HeLa cells. (a) Induction of cancer cell death by cathepsin E and its enhancement by a peptide. Cell viability was determined using a cell counting kit after treating HeLa cells for 20 h with cathepsin E and peptide T11 at different molar ratios (cathepsin E: peptide = 1 : 0, 1 : 10, 1 : 100). (b) Effect of a cathepsin E-activating peptide on cancer cell apoptosis. Apoptotic cells were stained with Annexin V-Cy3 for 24 h after incubating HeLa cells in the presence of 77 nM cathepsin E and 7.7 μM peptide T11. (c) Assessment of caspase activity induced by cathepsin E-activating peptide. Caspase-3 and/or -7 was measured at 24 h after incubating HeLa cells in the presence of 77 nM cathepsin E and 7.7 μM peptide T11. Error bars indicate the standard deviations of three independent experiments. Statistical significance is denoted by the symbols (* < 0.05, **< 0.01) and was based on comparison by Student’s t-test.
