Molecular basis of lysosomal storage disease and the possibility of a new therapeutic approach

(1)人α-半乳糖苷酶的组织特异性翻译后修饰在人α-半乳糖苷酶(α-Gal)转基因小鼠中进行异源基因表达和翻译后糖基化修饰。小鼠的心脏和肝脏表达了大量的转录物以及高α-Gal活性。其在心脏和肾脏中的基因产物对内切糖苷酶H消化敏感，而在脾和肝脏中的基因产物对内切糖苷酶H酶具有较强的抗性。糖肽酶F处理证实了该酶的多肽部分具有相同的分子质量。我们的结论是，基因产物的不同分子量是由小鼠组织中不同程度的翻译后糖基化引起的。(2)突变的β-半乳糖苷酶在Morquio B病患者中底物特异性改变β-半乳糖苷酶是一种由酸性β-半乳糖苷酶缺乏(β-Gal)引起的溶酶体储存病，包括两种不同的临床表型：Gm1-神经节苷脂沉积症和Morquio B病。T…前者有中枢神经系统损害较多，而后者有骨骼损害而无中枢神经系统损害。为了阐明解释这两种疾病临床差异的分子证据，我们使用人工底物类似物研究了来自神经节苷脂沉积症和Morquio B病患者的突变体β-Gal的底物特异性。Morquio B病突变株β-Gal(W237L/W237L，Y83H/R482C)与Gm1-神经节苷脂类似物GalGal-β1-3GalNAc相比，对GalβL-4Glc NAC亲和力较低，而正常β-Gal和突变型β-Gal(R201C/R201C，151t/151t)与GM1-神经节苷脂类似物Gal-Gal亲和力较低。此外，Morquio B突变体对类似物(Galβ1-4GlcNAc/Galβ1-3GalNAc)的水解率显著降低，而Gm1-神经节苷脂突变体的水解率与正常β-Gal相似。我们得出结论，GM1神经节苷脂沉积症和Moquio B病之间不同的临床表型是由于Morquio B病患者独特的基因突变导致突变的P-Gal底物特异性改变所致。较少

(1) Tissue-specific posttranslational modification of human α-galactosidaseHeterogeneous gene expression and posttranslational glycosylation were examined in human α-galactosidase (α-Gal) transgenic mouse. The heart and liver of the mouse expressed a high amount of transcript as well as high α-Gal activity. Its gene products in the heart and kidney were sensitive to endoglycosidase H digestion, but those in the spleen and liver were largely resistant. Glycopeptidase F treatment confirmed an identical molecular mass for the peptide moiety of the enzyme. We conclude that heterogeneous molecular mass of the gene products is caused by different degree of posttranslational glycosylation in murine tissues.(2) Altered substrate specificity of mutant β-galactosidase in patients with Morquio B diseaseβ-Galactosidodosis is a lysosomal storage disease caused by a deficiency of acid β-galactosidase (β-Gal) consisting of two different clinical phenotypes, GM1-gangliosidosis and Morquio B disease. T … More he former has central nervous system lesions, whereas the latter has skeletal lesions with no central nervous system lesions. To clarify the molecular evidence to account for clinical difference between both diseases, we investigated substrate specificity of mutant β-Gal derived from patients with GM1-gangliosidosis and Morquio B disease using artificial substrate analogs. Mutant β-Gal (W237L/W237L, Y83H/R482C) from Morquio B disease exhibited relatively low affinity to Galβl-4Glc NAc , an analog of keratan sulfate, as compared with Galβ1-3GalNAc, an analog of GM1-gangliosid, but there was not such difference in both normal β-Gal and mutant β-Gal (R201C/R201C, 151T/151T) from GM1-gangliosidosis. Furthermore, Morquio B mutants showed considerable decrease in hydrolysis ratio for the analogs (Galβ1-4GlcNAc/Galβ1-3GalNAc), yet GM1-gangliosidosis mutants had similar hydrolysis ratio to normal β-Gal. We conclude that distinct clinical phenotypes between GM1-gangliosidosis and Moquio B disease are caused by altered substrate specificity of mutant P-Gal resulting from unique gene mutations in patients with Morquio B disease. Less