α-Synuclein accumulation and GBA deficiency due to L444P GBA mutation contributes to MPTP-induced parkinsonism

Abstract

BackgroundMutations in glucocerebrosidase (GBA) cause Gaucher disease (GD) and increase the risk of developing Parkinson’s disease (PD) and Dementia with Lewy Bodies (DLB). Since both genetic and environmental factors contribute to the pathogenesis of sporadic PD, we investigated the susceptibility of nigrostriatal dopamine (DA) neurons in L444P GBA heterozygous knock-in (GBA+/L444P) mice to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a selective dopaminergic mitochondrial neurotoxin.MethodWe used GBA+/L444P mice, α-synuclein knockout (SNCA−/−) mice at 8 months of age, and adeno-associated virus (AAV)-human GBA overexpression to investigate the rescue effect of DA neuronal loss and susceptibility by MPTP. Mitochondrial morphology and functional assay were used to identify mitochondrial defects in GBA+/L444P mice. Motor behavioral test, immunohistochemistry, and HPLC were performed to measure dopaminergic degeneration by MPTP and investigate the relationship between GBA mutation and α-synuclein. Mitochondrial immunostaining, qPCR, and Western blot were also used to study the effects of α-synuclein knockout or GBA overexpression on MPTP-induced mitochondrial defects and susceptibility.ResultsL444P GBA heterozygous mutation reduced GBA protein levels, enzymatic activity and a concomitant accumulation of α-synuclein in the midbrain of GBA+/L444P mice. Furthermore, the deficiency resulted in defects in mitochondria of cortical neurons cultured from GBA+/L444P mice. Notably, treatment with MPTP resulted in a significant loss of dopaminergic neurons and striatal dopaminergic fibers in GBA+/L444P mice compared to wild type (WT) mice. Levels of striatal DA and its metabolites were more depleted in the striatum of GBA+/L444P mice. Behavioral deficits, neuroinflammation, and mitochondrial defects were more exacerbated in GBA+/L444P mice after MPTP treatment. Importantly, MPTP induced PD-like symptoms were significantly improved by knockout of α-synuclein or augmentation of GBA via AAV5-hGBA injection in both WT and GBA+/L444P mice. Intriguingly, the degree of reduction in MPTP induced PD-like symptoms in GBA+/L444Pα-synuclein (SNCA)−/− mice was nearly equal to that in SNCA−/− mice after MPTP treatment.ConclusionOur results suggest that GBA deficiency due to L444P GBA heterozygous mutation and the accompanying accumulation of α-synuclein render DA neurons more susceptible to MPTP intoxication. Thus, GBA and α-synuclein play dual physiological roles in the survival of DA neurons in response to the mitochondrial dopaminergic neurotoxin, MPTP.Electronic supplementary materialThe online version of this article (10.1186/s13024-017-0233-5) contains supplementary material, which is available to authorized users.

Impaired cellular bioenergetics caused by GBA1 depletion sensitizes neurons to calcium overload

“…These differences, together with the difference in oxidative stress, that was increased only in gba1 −/− neurons, may contribute to the difference of disease phenotype in the gba1 −/− and gba1 +/− mice. In agreement with our data, a mouse model carrying the heterozygous GBA1 PDassociated mutation L444P was shown to have defective mitochondria, supporting a role of impaired bioenergetics in GBA1-associated PD [57]. Dopaminergic neurons at risk of neurodegeneration in PD are physiologically characterized by Ca 2+ -dependent pace-making activity, while intrinsic Ca 2+ buffering capacity is reduced [22], imposing a major energy demand, which will be amplified by mechanisms that compromise bioenergetic reserve, putting these cells especially at risk [58].…”

Microtubule Dysfunction: A Common Feature of Neurodegenerative Diseases

“…The TPD binding of MTs stabilizes the longitudinal contacts between tubulin subunits and prevents MT disassembly [ 311 ]. In 2018, Zhang and colleagues tested CNDR-51657, a prototype of TPD, on a PS19 transgenic mouse model of tauopathies which expresses the P301S mutant form of human tau and shows the progressive accumulation of neurofibrillary tangles with age [ 294 ]. This study has demonstrated that low doses of CNDR-51657 significantly improved MT density in hippocampal neurons and reduced axonal dystrophy with a resulting reduction in tau pathology.…”

“…This study has demonstrated that low doses of CNDR-51657 significantly improved MT density in hippocampal neurons and reduced axonal dystrophy with a resulting reduction in tau pathology. Importantly, no adverse effects were observed in compound-treated mice, including no change in white blood cell counts [ 294 ].…”

The Vicious Cycle Between α‐Synuclein Aggregation and Autophagic‐Lysosomal Dysfunction

“…GCase is not directly involved in α‐syn degradation, but its reduced activity/availability promotes the accumulation and aggregation of α‐syn in different cellular cultures and animal models . Mazzulli and colleagues demonstrated, in human cortical neurons, that GCase depletion compromises protein degradation capacity, leading to increased α‐syn levels.…”

“…85 GCase is not directly involved in α-syn degradation, but its reduced activity/availability promotes the accumulation and aggregation of α-syn in different cellular cultures and animal models. 63,[86][87][88][89] Mazzulli and colleagues 63 demonstrated, in human cortical neurons, that GCase depletion compromises protein degradation capacity, leading to increased α-syn levels. Furthermore, GCase knockdown and concomitant expression of WT α-syn and A53T α-syn enhanced α-syn-mediated neurotoxicity through formation of soluble and insoluble hMW species.…”