Impact of β-galactosidase mutations on the expression of the canine lysosomal multienzyme complex

Abstract

β-galactosidase (GLB1) forms a functional lysosomal multienzyme complex with lysosomal protective protein (PPCA) and neuraminidase 1 (NEU1) which is important for its intracellular processing and activity. Mutations in the β-galactosidase gene cause the lysosomal storage disease G M1-gangliosidosis. In order to identify additional molecular changes associated with the presence of β-galactosidase mutations, the expression of canine lysosomal multienzyme complex components in GLB1 +/+, GLB1 +/− and GLB1 −/− fibroblasts was investigated by quantitative RT-PCR, Western blot and enzymatic assays. Quantitative RT-PCR revealed differential regulation of total β-galactosidase, β-galactosidase variants and protective protein for β-galactosidase gene ( PPGB) in GLB1 +/− and GLB1 −/− compared to GLB1 +/+ fibroblasts. Furthermore, it was shown that PPGB levels gradually increased with the number of mutant β-galactosidase alleles while no change in the NEU1 expression was observed. This is the first study that simultaneously examine the effect of GLB1 +/+, GLB1 +/− and GLB1 −/− genotypes on the expression of lysosomal multienzyme complex components. The findings reveal a possible adaptive process in GLB1 homozygous mutant and heterozygous individuals that could facilitate the design of efficient therapeutic strategies.