No evidence for substrate accumulation in Parkinson brains with GBA mutations.
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ABSTRACT:
SUBMITTER: Gegg ME
PROVIDER: S-EPMC4529481 | biostudies-other | 2015 Jul
REPOSITORIES: biostudies-other
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Project description:Somatic mutations in Parkinson disease are enriched in synaptic and neuronal processes
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Project description:ObjectiveMutations in the glucocerebrosidase gene (GBA) represent a significant risk factor for developing Parkinson disease (PD). We investigated the enzymatic activity of glucocerebrosidase (GCase) in PD brains carrying heterozygote GBA mutations (PD+GBA) and sporadic PD brains.MethodsGCase activity was measured using a fluorescent assay in cerebellum, frontal cortex, putamen, amygdala, and substantia nigra of PD+GBA (n = 9-14) and sporadic PD brains (n = 12-14). Protein expression of GCase and other lysosomal proteins was determined by western blotting. The relation between GCase, ?-synuclein, and mitochondria function was also investigated in vitro.ResultsA significant decrease in GCase activity was observed in all PD+GBA brain areas except the frontal cortex. The greatest deficiency was in the substantia nigra (58% decrease; p < 0.01). GCase activity was also significantly decreased in the substantia nigra (33% decrease; p < 0.05) and cerebellum (24% decrease; p < 0.05) of sporadic PD brains. GCase protein expression was lower in PD+GBA and PD brains, whereas increased C/EBP homologous protein and binding immunoglobulin protein levels indicated that the unfolded protein response was activated. Elevated ?-synuclein levels or PTEN-induced putative kinase 1 deficiency in cultured cells had a significant effect on GCase protein levels.InterpretationGCase deficiency in PD brains with GBA mutations is a combination of decreased catalytic activity and reduced protein levels. This is most pronounced in the substantia nigra. Biochemical changes involved in PD pathogenesis affect wild-type GCase protein expression in vitro, and these could be contributing factors to the GCase deficiency observed in sporadic PD brains.
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