Abstract
Mutations in glucocerebrosidase (GBA1) cause Gaucher disease and also represent a common risk factor for Parkinson’s disease and Dementia with Lewy bodies. Recently, new tool molecules were described which can increase turnover of an artificial substrate 4MUG when incubated with mutant N370S GBA1 from human spleen. Here we show that these compounds exert a similar effect on the wild-type enzyme in a cell-free system. In addition, these tool compounds robustly increase turnover of 4MUG by GBA1 derived from human cortex, despite substantially lower glycosylation of GBA1 in human brain, suggesting that the degree of glycosylation is not important for compound binding. Surprisingly, these tool compounds failed to robustly alter GBA1 turnover of 4MUG in the mouse brain homogenate. Our data raise the possibility that in vivo models with humanized glucocerebrosidase may be needed for efficacy assessments of such small molecules.
Highlights
Glucocerebrosidase is a lysosomal protein which breaks down glucosylceramide into glucose and ceramide [1,2]
50–70% of normal activity was reported in brain lysates from Parkinson’s disease (PD) patients [9] and ~ 75–80% of normal activity was seen in brain lysates from Dementia with Lewy bodies (DLB) patients [10]
We first determined the potency of two GBA1 inhibitors, CBE and isofagomine, under our conditions in a cell free system with purified human GBA1 and the artificial substrate 4MUG
Summary
Glucocerebrosidase is a lysosomal protein which breaks down glucosylceramide into glucose and ceramide [1,2]. Two mutant alleles in the glucocerebrosidase gene cause a lysosomal storage disorder called Gaucher disease. The mutations in glucocerebrosidase often cause decreased protein stability or enzymatic activity [2,3,4,5]. In Gaucher patients, glucocerebrosidase activity is decreased to ~ 5–20% of normal levels [3] and is accompanied by increased levels of its natural substrate, glucosylceramide [6]. GBA1 dysfunction has been recently linked to Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB). Mutations in GBA1 represent a common risk factor for both diseases [7,8]. Decreased GBA activity has been observed in brain lysates from patients.
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