The pharmacological chaperone 1-deoxynojirimycin increases the activity and lysosomal trafficking of multiple mutant forms of acid alpha-glucosidase

Abstract

Pompe disease is a lysosomal storage disorder (LSD) caused by mutations in the gene that encodes acid alpha-glucosidase (GAA). Recently, small molecule pharmacological chaperones have been shown to increase protein stability and cellular levels for mutant lysosomal enzymes and have emerged as a new therapeutic strategy for the treatment of LSDs. In this study, we characterized the pharmacological chaperone 1-deoxynojirimycin (DNJ) on 76 different mutant forms of GAA identified in Pompe disease. DNJ significantly increased enzyme activity and protein levels for 16 different GAA mutants in patient-derived fibroblasts and in transiently transfected COS-7 cells. Additionally, DNJ increased the processing of these GAA mutants to their mature lysosomal forms, suggesting facilitated trafficking through the secretory pathway. Immunofluorescence microscopy studies showed increased colocalization of GAA with the lysosomal marker LAMP2 after incubation with DNJ, confirming increased lysosomal trafficking. Lastly, a GAA structural model was constructed based on the related eukaryotic glucosidase maltase-glucoamylase. The mutated residues identified in responsive forms of GAA are located throughout most of the structural domains, with half of these residues located in two short regions within the catalytic domain. Taken together, these data support further evaluation of DNJ as a potential treatment for Pompe disease in patients that express responsive forms of GAA.

Biochemical and structural study on a S529V mutant acid α-glucosidase responsive to pharmacological chaperones

“…This therapy is based on the concept that imino sugars including DNJ and NB-DNJ interact with mutant GAA proteins, and thereby improve their stability and transportation to lysosomes. 13,14,28 However, these imino sugars are potent inhibitors of a-glucosidases including GAA and intestinal maltase-glucoamylase, and the administration of an excess dose results in intracellular storage of glycogen, 29 and glucosylated and galactosylated oligosaccharides. 30 So, it seems to be difficult to determine the proper doses of these chemicals for pharmacological chaperone therapy, and inadequate doses of them would worsen Pompe disease and might lead to diarrhea.…”

“…Furthermore, the mutant GAA species for which imino sugars are effective are limited. 13,14,28 Hence, characterization of mutant GAAs responsive to imino sugars, and detailed information about the complex formation of a mutant GAA and an imino sugar are strongly required for improvement of pharmacological chaperone therapy.…”

“…Considering the results of western blotting, these imino sugars should facilitate the transportation and processing of the S529V mutant GAA, and stabilize it. Recently, Flanagan et al 28 reported that 16 species of mutant GAAs, including p.S529V, responded to DNJ, and that 60 species including p.R600C, p.S619N, p.D645E and p.R672Q did not. Here we examined the characteristics of the S529V mutant GAA from a structural aspect.…”

New strategies for the treatment of lysosomal storage diseases (Review)

“…On the other hand, chaperone therapy appears to be feasible only in patients with responsive mutations mostly located in specific domains of the enzymatic protein (36).…”

New insights into therapeutic options for Pompe disease

“…Various inhibitors derived from deoxynojirimycin (DNJ) have been evaluated as pharmacological chaperones, in different lysosomal storage disorders (62). 1-deoxynojirimycin (DNJ) and N-butyl-DNJ (NBJ) were investigated in fibroblasts from Pompe patients (63,64). A significant increase of GAA activity was observed in fibroblasts from patients carrying different GAA mutants such as L552P, G549R, Y445F, and P545L mutations.…”