Figure 4

Enzymatic activity of mutant HGSNAT-L125_R128del protein can be partially restored by the pharmacological chaperone, glucosamine. (A) N-acetyltransferase activity of COS-7 cells transfected with the pcDNA-HGSNAT-L125_R128del plasmid is significantly increased compared to that of cells transfected with the empty pcDNA plasmid (mock). The data show means (±S.D.) of individual measurements. Three transfections (each in duplicate) were performed on separate occasions.** and ***: statistically different from mock-transfected cells (p < 0.01 and p < 0.001, respectively) according to unpaired t-test. (B) COS-7 cells transfected with the pcDNA-HGSNAT-L125_R128del plasmid produce 160 kDa dimmers and 78 kDa monomers of HGSNAT precursor protein but show drastically reduced amounts of 44 kDa and 25 kDa mature HGSNAT chains produced by intra-lysosomal enzymatic cleavage. Panel shows representative data of 3 independent transfections. (C) N-acetyltransferase activity of COS-7 cells transfected with the pcDNA-HGSNAT-L125_R128del plasmid and of cultured primary fibroblasts of the patient homozygous for the c.372-2A > G mutation is significantly increased after treating the cells in culture with 10 mM glucosamine for 72 h (+GA). The data show means (±S.D.) of individual measurements. Three independent experiments measurements were performed each of them with 2 cell plates. * and **: statistically different from untreated cells (p < 0.05 and p < 0.01, respectively) by unpaired t-test.