Figure 3.

Binding of Expressed Enzymes to CI-MPR

Expi293 cells or mouse D9 L-cells were co-transfected with expression plasmids for the indicated lysosomal enzymes along with empty vector, WT α/β precursor, or the S1-S3 mutant cDNA. D9 L-cells were used for generating GAA, while Expi293 cells were used for the other lysosomal enzymes. Forty-eight to 72 hr post-transfection, the media was collected, and aliquots were incubated with CI-MPR-beads to bind the phosphorylated lysosomal enzymes. The percentage of each lysosomal enzyme that bound to the CI-MPR-beads was determined as described in the Experimental Procedures. Values obtained with cells transfected with the empty vector (“endogenous”) represent the activity of the endogenous GlcNAc-1-phosphotransferase. *p < 0.05, **p < 0.01.