Chaperone therapy for neuronopathic lysosomal diseases: competitive inhibitors as chemical chaperones for enhancement of mutant enzyme activities.

Chaperone therapy is a newly developed molecular approach to lysosomal diseases, a group of human genetic diseases causing severe brain damage. We found two valienamine derivatives, N-octyl-4-epi-beta-valienamine (NOEV) and N-octyl-beta-valienamine (NOV), as promising therapeutic agents for human beta-galactosidase deficiency disorders (mainly G(M1)-gangliosidosis) and beta-glucosidase deficiency disorders (Gaucher disease), respectively. We briefly reviewed the historical background of research in carbasugar glycosidase inhibitors. Originally NOEV and NOV had been discovered as competitive inhibitors, and then their paradoxical bioactivities as chaperones were confirmed in cultured fibroblasts from patients with these disorders. Subsequently G(M1)-gangliosidosis model mice were developed and useful for experimental studies. Orally administered NOEV entered the brain through the blood-brain barrier, enhanced beta-galactosidase activity, reduced substrate storage, and improved neurological deterioration clinically. Furthermore, we executed computational analysis for prediction of molecular interactions between beta-galactosidase and NOEV. Some preliminary results of computational analysis of molecular interaction mechanism are presented in this article. NOV also showed the chaperone effect toward several beta-glucosidase gene mutations in Gaucher disease. We hope chaperone therapy will become available for some patients with G(M1)-gangliosidosis, Gaucher disease, and potentially other lysosomal storage diseases with central nervous system involvement.