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?-Galactosidase aggregation is a determinant of pharmacological chaperone efficacy on Fabry disease mutants.

ABSTRACT: Fabry disease is a lysosomal storage disorder caused by loss of ?-galactosidase function. More than 500 Fabry disease mutants have been identified, the majority of which are structurally destabilized. A therapeutic strategy under development for lysosomal storage diseases consists of using pharmacological chaperones to stabilize the structure of the mutant protein, thereby promoting lysosomal delivery over retrograde degradation. The substrate analog 1-deoxygalactonojirimycin (DGJ) has been shown to restore activity of mutant ?-galactosidase and is currently in clinical trial for treatment of Fabry disease. However, only ?65% of tested mutants respond to treatment in cultured patient fibroblasts, and the structural underpinnings of DGJ response remain poorly explained. Using computational modeling and cell culture experiments, we show that the DGJ response is negatively affected by protein aggregation of ?-galactosidase mutants, revealing a qualitative difference between misfolding-associated and aggregation-associated loss of function. A scoring function combining predicted thermodynamic stability and intrinsic aggregation propensity of mutants captures well their aggregation behavior under overexpression in HeLa cells. Interestingly, the same classifier performs well on DGJ response data of patient-derived cultured lymphoblasts, showing that protein aggregation is an important determinant of chemical chaperone efficiency under endogenous expression levels as well. Our observations reinforce the idea that treatment of aggregation-associated loss of function observed for the more severe ?-galactosidase mutants could be enhanced by combining pharmacological chaperone treatment with the suppression of mutant aggregation, e.g. via proteostatic regulator compounds that increase cellular chaperone expression.

SUBMITTER: Siekierska A

PROVIDER: S-EPMC3436532 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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α-Galactosidase aggregation is a determinant of pharmacological chaperone efficacy on Fabry disease mutants.

Siekierska Aleksandra A De Baets Greet G Reumers Joke J Gallardo Rodrigo R Rudyak Stanislav S Broersen Kerensa K Couceiro Jose J Van Durme Joost J Schymkowitz Joost J Rousseau Frederic F

The Journal of biological chemistry 20120706 34

Fabry disease is a lysosomal storage disorder caused by loss of α-galactosidase function. More than 500 Fabry disease mutants have been identified, the majority of which are structurally destabilized. A therapeutic strategy under development for lysosomal storage diseases consists of using pharmacological chaperones to stabilize the structure of the mutant protein, thereby promoting lysosomal delivery over retrograde degradation. The substrate analog 1-deoxygalactonojirimycin (DGJ) has been show ...[more]

PMID: 22773828

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Project description:Fabry disease is one of the most common lysosomal storage disorders caused by mutations in the gene encoding lysosomal ?-galactosidase A (?-Gal A) and resultant accumulation of glycosphingolipids. The sugar mimetic 1-deoxygalactonojirimycin (DGJ), an orally available pharmacological chaperone, was clinically approved as an alternative to intravenous enzyme replacement therapy. The decision as to whether a patient should be treated with DGJ depends on the genetic variant within the ?-galactosidase A encoding gene (GLA). A good laboratory practice (GLP)-validated cell culture-based assay to investigate the biochemical responsiveness of the variants is currently the only source available to obtain pivotal information about susceptibility to treatment. Herein, variants were defined amenable when an absolute increase in enzyme activity of ?3% of wild type enzyme activity and a relative increase in enzyme activity of ?1.2-fold was achieved following DGJ treatment. Efficacy testing was carried out for over 1000 identified GLA variants in cell culture. Recent data suggest that about one-third of the variants comply with the amenability criteria. A recent study highlighted the impact of inter-assay variability on DGJ amenability, thereby reducing the power of the assay to predict eligible patients. This prompted us to compare our own ?-galactosidase A enzyme activity data in a very similar in-house developed assay with those from the GLP assay. In an essentially retrospective approach, we reviewed 148 GLA gene variants from our former studies for which enzyme data from the GLP study were available and added novel data for 30 variants. We also present data for 18 GLA gene variants for which no data from the GLP assay are currently available. We found that both differences in experimental biochemical data and the criteria for the classification of amenability cause inter-assay discrepancy. We conclude that low baseline activity, borderline biochemical responsiveness, and inter-assay discrepancy are alarm signals for misclassifying a variant that must not be ignored. Furthermore, there is no solid basis for setting a minimum response threshold on which a clinical indication with DGJ can be justified.

Dataset Information

?-Galactosidase aggregation is a determinant of pharmacological chaperone efficacy on Fabry disease mutants.

Publications

α-Galactosidase aggregation is a determinant of pharmacological chaperone efficacy on Fabry disease mutants.

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