(A and B) Silver-stained SDS-PAGE analysis of recombinant human PGRN incubated at a 1:10 enzyme/substrate ratio with purified human NE (A) and recombinant mouse PR3 (B). Both NE and PR3 completely cleaved ~80-kDa PGRN to smaller molecular fragments within 5 min of incubation. (C) Recombinant mouse PGRN was incubated with neutrophil lysates from WT, Ela2–/–, and Prtn3–/–Ela2–/– mice for 1 h at 37°C and analyzed by anti-mouse PGRN Western blot. Compared with untreated PGRN (control), WT neutrophils completely degraded PGRN. In Ela2–/– neutrophils, a faint band of intact PGRN was detected, while in Prtn3–/–Ela2–/– neutrophils, a distinct PGRN band remained, comparable to control.