FIGURE 2.

Expression of MSCV-PPCA mutants in GS fibroblasts. GS were single- or double-transduced with MSCV-based bicistronic (GFP) retroviral vectors containing wild-type Neu1 cDNA (NEU1) and either wild-type PPCA (PPCA) or mutant PPCA (R20A, A251E, L354D, K355Q, W382A, P451A) cDNAs. The cells were fluorescence-sorted for transduced GFP-expressing cells. Fluorescence-sorted cells were analyzed on immunoblots with anti-PPCA (A) and anti-NEU1 (B) antibodies. C, the activities of cathepsin A (CA; black bars) and NEU1 (gray bars) were measured in homogenates of the transduced GS fibroblasts, nontransduced normal fibroblasts (Control), and nontransduced GS fibroblasts. Cathepsin A activity is expressed as nmol of substrate/min/mg total protein; NEU1 activity is expressed as nmol substrate/h/mg of total protein.