Gaucher disease (GD) is a disorder of glycosphinglipid metabolism caused by 
deficiency of lysosomal acid beta-glucosidase (GC), resulting in progressive 
deposition of glucosylceramide in macrophages. The glucose analogue, 
N-butyl-deoxynojirimycin (NB-DNJ, Miglustat), is an inhibitor of the 
ceramide-specific glucosyltransferase (CSG) which catalyzes the first step of 
glycosphingolipids biosynthesis and is currently approved for the oral treatment 
of type 1 GD. Using site-directed mutagenesis, we constructed plasmids 
containing wild-type and several mutations in glucocerebrosidase (GBA) gene. The 
plasmids were transfected into COS-7 cells and stable transfected cell lines 
were obtained by geneticin (G418) selection. Cells were cultured during 6 days 
with medium with or without 10 microM NB-DNJ. The addition of NB-DNJ to COS-7 
cell medium leads to 1.3-, 2.1-, 2.3-, 3.6-, and 9.9-fold increase in the 
activity of S364R, wild-type, N370S, V15M, and M123T GC, respectively. However, 
no significant changes were observed in the activity of the L444P, L336P, and 
S465del mutated proteins, but a small decrease in the rare P266L variant was 
observed. These results suggest that NB-DNJ, in addition to the inhibitory 
effect on CSG, also works as a "chemical chaperone", increasing the activity of 
acid beta-glucosidase of wild-type and several GC mutated proteins, including 
the most frequent N370S mutation. The specific location of the Miglustat binding 
site in GC is unknown. Potential binding sites in the enzyme have been searched 
for using computational molecular docking. The searching strategy identified 
three potential GC binding sites for Miglustat, one being the substrate-binding 
site of the enzyme, which was the best-ranked site by AutoDock program. 
Therefore, it is possible that Miglustat exerts its chaperoning activity on acid 
beta-glucosidase by acting as an inhibitor bound at the active site. This 
increase on the activity of the acid beta-glucosidase would imply that Miglustat 
is not only a substrate reducer but also an inhibitor of the GC degradation, 
with very promising clinical implications for the treatment of GD patients.