A modulator of wild-type glucocerebrosidase improves pathogenic phenotypes in dopaminergic neuronal models of Parkinson’s disease

Mutations in the <i>GBA1</i> gene encoding the lysosomal enzyme β-glucocerebrosidase (GCase) represent the most common risk factor for Parkinson's disease (PD). GCase has been identified as a potential therapeutic target for PD and current efforts are focused on chemical chaperones to translocate mutant GCase into lysosomes. However, for several <i>GBA1</i>-linked forms of PD and PD associated with mutations in <i>LRRK2</i>, <i>DJ-1</i>, and <i>PARKIN</i>, activating wild-type GCase represents an alternative approach. We developed a new small-molecule modulator of GCase called S-181 that increased wild-type GCase activity in iPSC-derived dopaminergic neurons from sporadic PD patients, as well as patients carrying the 84GG mutation in <i>GBA1</i>, or mutations in <i>LRRK2</i>, <i>DJ-1</i>, or <i>PARKIN</i> who had decreased GCase activity. S-181 treatment of these PD iPSC-derived dopaminergic neurons partially restored lysosomal function and lowered accumulation of oxidized dopamine, glucosylceramide and α-synuclein. Moreover, S-181 treatment of mice heterozygous for the D409V <i>GBA1</i> mutation (<i>Gba1^D409V/+</i> ) resulted in activation of wild-type GCase and consequent reduction of GCase lipid substrates and α-synuclein in mouse brain tissue. Our findings point to activation of wild-type GCase by small-molecule modulators as a potential therapeutic approach for treating familial and sporadic forms of PD that exhibit decreased GCase activity.