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A pharmacogenetic approach to identify mutant forms of ?-galactosidase A that respond to a pharmacological chaperone for Fabry disease.

ABSTRACT: Fabry disease is caused by mutations in the gene (GLA) that encodes ?-galactosidase A (?-Gal A). The iminosugar AT1001 (GR181413A, migalastat hydrochloride, 1-deoxygalactonojirimycin) is a pharmacological chaperone that selectively binds and stabilizes ?-Gal A, increasing total cellular levels and activity for some mutant forms (defined as "responsive"). In this study, we developed a cell-based assay in cultured HEK-293 cells to identify mutant forms of ?-Gal A that are responsive to AT1001. Concentration-dependent increases in ?-Gal A activity in response to AT1001 were shown for 49 (60%) of 81 mutant forms. The responses of ?-Gal A mutant forms were generally consistent with the responses observed in male Fabry patient-derived lymphoblasts. Importantly, the HEK-293 cell responses of 19 ?-Gal A mutant forms to a clinically achievable concentration of AT1001 (10?µM) were generally consistent with observed increases in ?-Gal A activity in peripheral blood mononuclear cells from male Fabry patients orally administered AT1001 during Phase 2 clinical studies. This indicates that the cell-based responses can identify mutant forms of ?-Gal A that are likely to respond to AT1001 in vivo. Thus, the HEK-293 cell-based assay may be a useful aid in the identification of Fabry patients with AT1001-responsive mutant forms.

SUBMITTER: Wu X

PROVIDER: S-EPMC3170878 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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A pharmacogenetic approach to identify mutant forms of α-galactosidase A that respond to a pharmacological chaperone for Fabry disease.

Wu Xiaoyang X Katz Evan E Della Valle Maria Cecilia MC Mascioli Kirsten K Flanagan John J JJ Castelli Jeffrey P JP Schiffmann Raphael R Boudes Pol P Lockhart David J DJ Valenzano Kenneth J KJ Benjamin Elfrida R ER

Human mutation 20110712 8

Fabry disease is caused by mutations in the gene (GLA) that encodes α-galactosidase A (α-Gal A). The iminosugar AT1001 (GR181413A, migalastat hydrochloride, 1-deoxygalactonojirimycin) is a pharmacological chaperone that selectively binds and stabilizes α-Gal A, increasing total cellular levels and activity for some mutant forms (defined as "responsive"). In this study, we developed a cell-based assay in cultured HEK-293 cells to identify mutant forms of α-Gal A that are responsive to AT1001. Con ...[more]

PMID: 21598360

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Project description:Fabry disease is an X-linked genetic disorder characterized by deficient activity of ?-galactosidase A (GLA) and accumulation of glycolipids, and various GLA gene mutations lead to a wide range of clinical phenotypes from the classic form to the later-onset one. To investigate the biochemical heterogeneity and elucidate the basis of the disease using available clinical samples, we measured GLA activity, GLA protein and accumulated globotriaosylsphingosine (Lyso-Gb3), a biomarker of this disease, in plasma samples from Fabry patients. The analysis revealed that both the enzyme activity and the protein level were apparently decreased, and the enzyme activity was well correlated with the protein level in many Fabry patients. In these cases, a defect of biosynthesis or excessive degradation of mutant GLAs should be involved in the pathogenesis, and the residual protein level would determine the accumulation of Lyso-Gb3 and the severity of the disease. However, there are some exceptional cases, i.e., ones harboring p.C142Y, p.R112H and p.M296I, who exhibit a considerable amount of GLA protein. Especially, a subset of Fabry patients with p.R112H or p.M296I has been attracted interest because the patients exhibit almost normal plasma Lyso-Gb3 concentration. Structural analysis revealed that C142Y causes a structural change at the entrance of the active site. It will lead to a complete enzyme activity deficiency, resulting in a high level of plasma Lyso-Gb3 and the classic Fabry disease. On the other hand, it is thought that R112H causes a relatively large structural change on the molecular surface, and M296I a small one in a restricted region from the core to the surface, both the structural changes being far from the active site. These changes will cause not only partial degradation but also degeneration of the mutant GLA proteins, and the degenerated enzymes exhibiting small and residual activity remain and probably facilitate degradation of Lyso-Gb3 in plasma, leading to the later-onset phenotype. The results of this comprehensive analysis will be useful for elucidation of the basis of Fabry disease.

Dataset Information

A pharmacogenetic approach to identify mutant forms of ?-galactosidase A that respond to a pharmacological chaperone for Fabry disease.

Publications

A pharmacogenetic approach to identify mutant forms of α-galactosidase A that respond to a pharmacological chaperone for Fabry disease.

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