Glucocerebrosidase deficiency in substantia nigra of parkinson disease brains

Abstract

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, α-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 α-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. ANN NEUROL 2012;72:455–463.

Ambroxol effects in glucocerebrosidase and α‐synuclein transgenic mice

“…Significant reductions in GCase activity were observed in the brainstem, midbrain, cortex, and striatum of SNCA/SNCA mice. This finding further supports existing data, which demonstrate that increased α‐synuclein is associated with decrease in GCase activity in PD brains and in the SH‐SY5Y cell lines overexpressing SNCA 15. Analysis of α‐synuclein protein levels in different brain regions of SNCA/SNCA mice demonstrated approximately 50% increase in α‐synuclein levels compared to wild‐type mice in the brainstem, cortex, and striatum.…”

“…It has been shown in SH‐SY5Y cell cultures, neuronal cultures, conduritol‐β‐epoxide (CβE)‐treated mice, and transgenic Gba1 mouse models that reduced GCase activity results in increased α‐synuclein levels 7, 8, 9, 10, 11, 12, 13, 14. Conversely, it has been demonstrated in cell models that increased α‐synuclein causes a decrease in GCase activity 15. Moreover, the biochemical analysis of GBA1 wild‐type Parkinson patients showed that GCase activity and protein levels were significantly reduced in several brain regions,15, 16 further stressing the importance of GCase in PD development.…”

Mitochondrial dysfunction and mitophagy defect triggered by heterozygous GBA mutations

“…GBA enzyme activity was measured in lysosome-enriched fractions using 4-methylumbelliferyl β-D-glucopyranoside (Sigma, M3633) as a substrate, as in Gegg et al, 2012 [79]. Brain tissue or cell pellets were homogenized in buffer containing 250 mM sucrose, 10 mM Tris, pH 7.4, protease (Roche, 11836170001) and phosphatase inhibitor cocktails (Sigma, P5726).…”

Dysregulation of protein phosphatase 2A in parkinson disease and dementia with lewy bodies

“…Another mechanism through which α ‐synuclein accumulation leads to impaired PP2A activity is through the lysosomal enzyme glucocerebrosidase (GCase), which has strong genetic link to PD and is decreased in sporadic PD brains 50, 51. In this regard, accumulation of oligomeric and phosphorylated α ‐synuclein with age in the brains of cynomolgus monkeys is associated with decreased expression and activity of GCase, as well as reduced activity of PP2A particularly in brain regions that are susceptible to α ‐synucleinopathy‐related neurodegeneration.…”