Mutations causing the majority of Gaucher's disease cases compromise beta-glucocerbrosidase (GC) folding in the endoplasmic reticulum (ER), leading to ER-associated degradation (ERAD), and loss of activity of GC in the lysosome. While the majority of the mutant enzymes are somewhat compromised with regard to catalytic efficiency, the most significant problem is that there is insufficient enzyme that makes it to the lysosome for normal function. As a consequence, the glycolipid substrate glucosylceramide accumulates in the lysosome in patients, leading to pathology. We seek to discover the key components that direct the trafficking of GC from the ER to the lysosome. We will explore the general hypothesis that the critical interaction between GC, ER-associated folding pathways (ERAF) and trafficking receptors is disrupted in misfolded GC variants, resulting in loss of delivery to the lysosome and targeting for ERAD in the ER. Knowledge of these transport pathways will be crucial for interpretation of the effects of small molecule rescue of activity and is likely to provide important general insight(s) into new mechanisms of lysosomal hydrolase trafficking and may reveal unanticipated approaches to therapeutic intervention in disease. We will develop multiple strategies to identify small molecules that function as chemical chaperones or folding modulators to correct lysosomal storage disorders. In these studies we will explore the hypothesis that two classes of compounds can be used to rescue misfolding-chemical chaperones that selectively bind GC to correct the fold and folding modulators that alter the folding capacity of the cell. The latter class will be discovered by high throughput screening and may serve as general reagents for therapeutic intervention in a broader range of protein misfolding diseases and are anticipated to provide insight into the function of the ER-associated folding (ERAF) machinery.
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