In vitro inhibition and intracellular enhancement of lysosomal α‐galactosidase A activity in Fabry lymphoblasts by 1‐deoxygalactonojirimycin and its derivatives

Abstract

Fabry disease is a lysosomal storage disorder caused by deficient lysosomal α‐galactosidase A (α‐Gal A) activity. Deficiency of the enzyme activity results in progressive deposition of neutral glycosphingolipids with terminal α‐galactosyl residue in vascular endothelial cells. We recently proposed a chemical chaperone therapy for this disease by administration of 1‐deoxygalactonojirimycin, a potent inhibitor of the enzyme, at subinhibitory intracellular concentrations [Fan, J.‐Q., Ishii, S., Asano, N. and Suzuki, Y. (1999) Nat. Med.5, 112–115]. 1‐Deoxygalactonojirimycin served as a specific chaperone for those mutant enzymes that failed to maintain their proper conformation to avoid excessive degradation. In order to establish a correlation between in vitro inhibitory activity and intracellular enhancement activity of the specific chemical chaperone, a series of 1‐deoxygalactonojirimycin derivatives were tested for activity with both α‐Gal A and Fabry lymphoblasts. 1‐Deoxygalactonojirimycin was the most potent inhibitor of α‐Gal A with an IC 50 value of 0.04 µ m. α‐Galacto‐homonojirimycin, α‐allo‐homonojirimycin and β‐1‐C‐butyl‐deoxygalactonojirimycin were effective inhibitors with IC 50 values of 0.21, 4.3 and 16 µ m, respectively. N‐Alkylation, deoxygenation at C‐2 and epimerization at C‐3 of 1‐deoxygalactonojirimycin markedly lowered or abolished its inhibition toward α‐Gal A. Inclusion of 1‐deoxygalactonojirimycin, α‐galacto‐homonojirimycin, α‐allo‐homonojirimycin and β‐1‐C‐butyl‐deoxygalactonojirimycin at 100 µ m in culture medium of Fabry lymphoblasts increased the intracellular α‐Gal A activity by 14‐fold, 5.2‐fold, 2.4‐fold and 2.3‐fold, respectively. Weaker inhibitors showed only a minimum enhancement effect. These results suggest that more potent inhibitors act as more effective specific chemical chaperones for the mutant enzyme, and the potent competitive inhibitors of α‐Gal A are effective specific chemical chaperones for Fabry disease.