Three classes of glucocerebrosidase inhibitors identified by quantitative high-throughput screening are chaperone leads for Gaucher disease.
Zheng, W., Padia, J., Urban, D.J., et al. Proc. Nat. Acad. Sci., 104 (32), 13192-13197 (August 7, 2007).
Scientists at the National Genome Research Institute applied a newly developed high-throughput screening technique to search for compounds that might act as chemical chaperones as a therapy for Gaucher disease. This autosomal recessive disorder is characterized by an abnormally folded lysosomal enzyme, glucocerebrosidase (GC), which is involved in lipid storage. More than 200 genetic mutations have been identified that result in a misfolding, decreased stability, and/or mistrafficking of this enzyme. Although enzyme replacement therapy is available to treat the disease, less expensive and more convenient alternatives are being sought. One approach is the creation of chemical chaperones, small molecules whose binding to GC might correct its conformational state and thereby enable appropriate transfer of the enzyme to the lysosome.
In all, nearly 60,000 compounds were screened for an ability to interact with GC in vitro, as evidenced by enzyme inhibition or activation. Three distinct classes of compounds were found to be inhibitors, and none resembled the iminosugars that were already known to affect the enzyme, but with limited specificity. The nonsugar molecules were mixed inhibitors to GC, raising the Km and lowering the Vmax, and were specific in that none showed activity against lipid hydrolases. Moreover, the compounds increased GC activity in fibroblasts (N370S) carrying specific Gaucher-related mutations by 40%-90%, but had limited affect on wild-type enzyme activity. A double-labeling experiment showed that the elevated GC activity was associated with a significant increase in enzyme protein in the fibroblast lysosomes. Accordingly, the three compounds appear to have acted as small chemical chaperones for intracellular trafficking of GC.
The compounds were deemed leads for further refinement in the eventual development of new therapeutic agents. Yet, the experiments were successful in providing the proof of concept, one which may give rise to low-cost therapies for a number of lysosomal enzyme disorders, including Sandhoff, Fabry, and Tay-Sachs diseases.
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