Chemical chaperone therapy: Chaperone effect on mutant enzyme and cellular pathophysiology in β-galactosidase deficiency

β-Galactosidase deficiency is a group of lysosomal lipid storage disorders with an autosomal recessive trait. It causes two clinically different diseases, G_M1-gangliosidosis and Morquio B disease. It is caused by heterogeneous mutations in the GLB1 gene coding for the lysosomal acid β-galactosidase. We have previously reported the chaperone effect of N-octyl-4-epi-β-valienamine (NOEV) on mutant β-galactosidase proteins. In this study, we performed genotype analyses of patients with β-galactosidase deficiency and identified 46 mutation alleles including 9 novel mutations. We then examined the NOEV effect on mutant β-galactosidase proteins by using six strains of patient-derived skin fibroblast. We also performed mutagenesis to identify β-galactosidase mutants that were responsive to NOEV and found that 22 out of 94 mutants were responsive. Computational structural analysis revealed the mode of interaction between human β-galactosidase and NOEV. Moreover, we confirmed that NOEV reduced G_M1 accumulation and ameliorated the impairments of lipid trafficking and protein degradation in β-galactosidase deficient cells. These results provided further evidence to NOEV as a promising chaperone compound for β-galactosidase deficiency.