Globoid cell Leukodystrophy (GLD; Krabbe disease), is a devastating lysosomal storage disorder caused by mutations in galactosylceramidase (GALC) that severely impair enzymatic activity. Affected individuals typically present with symptoms in the first few months of life. Disease progression is generally rapid, leading to death within 1-2 years. Current treatment options for the disease are very limited. At least 62 mutations in the GALC gene have been identified that cause disease. The majority of these mutations are missense mutations that lie outside of the catalytic domain. We have recently demonstrated that at least several of these mutations appear to affect enzymatic activity by causing the enzyme to be misprocessed and subsequently degraded, similar to other misfolded protein disorders such as nephrogenic diabetes insipidus, primary hyperoxaluria type 1, congenital nephrotic syndrome, and other lysosomal storage diseases such as Gaucher disease and Fabry disease. In many of these instances small molecular weight inhibitors of the affected proteins themselves can """"""""trick"""""""" the quality control machinery of the cell to recognize the mutant protein as normal thus allowing it reach the appropriate organelle where it becomes active. Using this approach we have already screened through a small library of compounds and identified one inhibitor that when applied to cells harboring a mutant form of GALC resulted in a substantial increase in GALC enzymatic activity. In this exploratory application we propose to expand our in vitro screens to identify additional inhibitors of GALC and determine whether or not these compounds can influence mutant GALC enzymatic activity in model systems. Further we propose to determine the subcellular localization of this increased activity to determine if the enzyme has reached its proper location and to monitor natural substrate cleavage as a prelude to in vivo testing.
| Lee, Wing C; Kang, Dongcheul; Causevic, Ena et al. (2010) Molecular characterization of mutations that cause globoid cell leukodystrophy and pharmacological rescue using small molecule chemical chaperones. J Neurosci 30:5489-97 |
