Development of an ?-synuclein knockdown peptide and evaluation of its efficacy in Parkinson's disease models.
ABSTRACT: Convincing evidence supports the premise that reducing ?-synuclein levels may be an effective therapy for Parkinson's disease (PD); however, there has been lack of a clinically applicable ?-synuclein reducing therapeutic strategy. This study was undertaken to develop a blood-brain barrier and plasma membrane-permeable ?-synuclein knockdown peptide, Tat-?syn-degron, that may have therapeutic potential. The peptide effectively reduced the level of ?-synuclein via proteasomal degradation both in cell cultures and in animals. Tat-?syn-degron decreased ?-synuclein aggregates and microglial activation in an ?-synuclein pre-formed fibril model of spreading synucleinopathy in transgenic mice overexpressing human A53T ?-synuclein. Moreover, Tat-?syn-degron reduced ?-synuclein levels and significantly decreased the parkinsonian toxin-induced neuronal damage and motor impairment in a mouse toxicity model of PD. These results show the promising efficacy of Tat-?syn-degron in two different animal models of PD and suggest its potential use as an effective PD therapeutic that directly targets the disease-causing process.
Project description:Transgenic mice line M83 that express the A53T mutant α-synuclein protein at six times the level of endogenous mice α-synuclein are a model of α-synucleinopathy found in Parkinson's disease (PD). This Hualpha-Syn (A53T) PD model is useful in assessing non-motor deficits at earlier stages of onset of PD. We report findings on metabolic changes using [<sup>18</sup>F]FDG PET/CT in the Hualpha-Syn (A53T) PD mouse model in comparison to non-carrier mice. Whole-body PET/CT imaging of male and female mice were carried out 2 h after [<sup>18</sup>F]FDG ip administration under 3% isoflurane anesthesia. Brain images were analyzed with PET images coregistered to a mouse brain MRI template. Hualpha-Syn (A53T) mice had significantly lower [<sup>18</sup>F]FDG uptake in several brain regions compared to the no-carrier mice. Significant hind limb muscle and lower spinal cord [<sup>18</sup>F]FDG hypometabolism at 9 months of age in A53T PD mice was also indicative of neurodegenerative disease, with a progressive motoric dysfunction leading to death. Significant decrease (up to 30%) in [<sup>18</sup>F]FDG uptake were observed in 9-month old male and female Hualpha-Syn (A53) mice. This is consistent with the cortical hypometabolism in PD patients. Hualpha-Syn (A53) mice may thus be a suitable model for studies related to PD α-synucleinopathy for the discovery of new biomarkers.
Project description:Despite converging epidemiological evidence for the inverse relationship of regular caffeine consumption and risk of developing Parkinson's disease (PD) with animal studies demonstrating protective effect of caffeine in various neurotoxin models of PD, whether caffeine can protect against mutant ?-synuclein (?-Syn) A53T-induced neurotoxicity in intact animals has not been examined. Here, we determined the effect of chronic caffeine treatment using the ?-Syn fibril model of PD by intra-striatal injection of preformed A53T ?-Syn fibrils. We demonstrated that chronic caffeine treatment blunted a cascade of pathological events leading to ?-synucleinopathy, including pSer129?-Syn-rich aggregates, apoptotic neuronal cell death, microglia, and astroglia reactivation. Importantly, chronic caffeine treatment did not affect autophagy processes in the normal striatum, but selectively reversed ?-Syn-induced defects in macroautophagy (by enhancing microtubule-associated protein 1 light chain 3, and reducing the receptor protein sequestosome 1, SQSTM1/p62) and chaperone-mediated autophagy (CMA, by enhancing LAMP2A). These findings support that caffeine-a strongly protective environment factor as suggested by epidemiological evidence-may represent a novel pharmacological therapy for PD by targeting autophagy pathway.
Project description:Parkinson's disease (PD) is a movement disorder caused by neurodegeneration in neocortex, substantia nigra and brainstem, and synucleinopathy. Some inherited PD is caused by mutations in ?-synuclein (?Syn), and inherited and idiopathic PD is associated with mitochondrial perturbations. However, the mechanisms of pathogenesis are unresolved. We characterized a human ?Syn transgenic mouse model and tested the hypothesis that the mitochondrial permeability transition pore (mPTP) is involved in the disease mechanisms. C57BL/6 mice expressing human A53T-mutant ?Syn driven by a thymic antigen-1 promoter develop a severe, age-related, fatal movement disorder involving ataxia, rigidity, and postural instability. These mice develop synucleinopathy and neocortical, substantia nigra, and cerebello-rubro-thalamic degeneration involving mitochondriopathy and apoptotic and non-apoptotic neurodegeneration. Interneurons undergo apoptotic degeneration in young mice. Mutant ?Syn associated with dysmorphic neuronal mitochondria and bound voltage-dependent anion channels. Genetic ablation of cyclophilin D, an mPTP modulator, delayed disease onset, and extended lifespans of mutant ?Syn mice. Thus, mutant ?Syn transgenic mice on a C57BL/6 background develop PD-like phenotypes, and the mPTP is involved in their disease mechanisms.
Project description:Ankyrin-rich BTB/POZ domain containing protein-2 or BPOZ-2, a scaffold protein, has been recently shown to control the degradation of many biological proteins ranging from embryonic development to tumor progression. However, its role in the process of neuronal diseases has not been properly explored. Since, abnormal clearance of metabolic proteins contributes to the development of alpha-synuclein (?-syn) pathologies in Parkinson's disease (PD), we are interested to explore if BPOZ-2 participates in the amelioration of ?-syn in vivo in basal ganglia. Here we report that lentiviral administration of bpoz-2 gene indeed lowers the burden of ?-syn in DA neurons in the nigra of A53T transgenic (A53T-Tg) mouse. Our detailed immunological analyses have shown that the overexpression of bpoz-2 dramatically improves both somatic and neuritic ?-syn pathologies in the nigral DA neurons. Similarly, the specific ablation of bpoz-2 by lentiviral-shRNA stimulates the load of monomeric and polymeric forms of ?-syn in the nigral DA neurons of A53T-Tg. While investigating the mechanism, we observed that BPOZ-2 was involved in a protein-protein association with PINK1 and therefore could stimulate PINK1-dependent autophagic clearance of ?-syn. Our results have demonstrated that bpoz-2 gene delivery could have prospect in the amelioration of alpha-synucleinopathy in PD and other Lewy body diseases.
Project description:Background: Mutations in glucocerebrosidase (GBA), a lysosomal enzyme are the most common genetic risk factor for developing Parkinson's disease (PD). We studied how reduced GCase activity affects ?-synuclein (?-syn) and its mutants (A30P and A53T) aggregation, neurodegeneration, sleep and locomotor behavior in a fly model of PD. Methods: We developed drosophila with GBA gene knockdown (RNAi) (with reduced GCase activity) that simultaneously expresses either wildtype (WT) or mutants such as A30P or A53T ?-syn. Western blot and confocal microscopy were performed to study the ?-syn aggregation and neurodegeneration in these flies. We also studied the sleep and locomotor activity of those flies using Drosophila activity monitor (DAM) system. Results: Western blot analysis showed that GBA RNAi A53T ?-syn flies (30 days old) had an increased level of Triton insoluble synuclein (that corresponds to ?-syn aggregates) compared to corresponding A53T flies without GBA RNAi (control), while mRNA expression of ?-syn remained unchanged. Confocal imaging of whole brain staining of 30 days old drosophila showed a statistically significant decrease in neuron numbers in PPL1 cluster in flies expressing ?-syn WT, A30P and A53T in the presence GBA RNAi compared to corresponding control. Staining with conformation specific antibody for ?-syn aggregates showed an increased number of neurons staining for ?-syn aggregates in A53T fly brain with GBA RNAi compared to control A53T flies, thus confirming our protein analysis finding that under decreased GBA enzyme activity, mutant A53T aggregates more than the control A53T without GBA silencing. Sleep analysis revealed decreased total activity in GBA silenced flies expressing mutant A53T compared to both A53T control flies and GBA RNAi flies without synuclein expression. Conclusion: In A53T flies with reduced GCase activity, there is increased ?-syn aggregation and dopamine (DA) neuronal loss. This study demonstrates that reduced GCase activity both in the context of heterozygous GBA1 mutation associated with PD and in old age, contribute to increased aggregation of mutant ?-syn A53T and exacerbates the phenotype in a fly model of PD.
Project description:Parkinson's disease (PD) is the second most common neurodegenerative disease. A key pathological feature of PD is Lewy bodies, of which the major protein component is ?-synuclein (?-syn). Human genetic studies have shown that mutations (A53T, A30P, E46K) and multiplication of the ?-syn gene are linked to familial PD. Mice overexpressing the human A53T mutant ?-syn gene develop severe movement disorders. However, the molecular mechanisms of ?-syn toxicity are not well understood. Recently, mitochondrial dysfunction has been linked with multiple neurodegenerative diseases including Parkinson's disease. Here we investigated whether mitochondrial motility, dynamics and respiratory function are affected in primary neurons from a mouse model expressing the human A53T mutation. We found that mitochondrial motility was selectively inhibited in A53T neurons while transport of other organelles was not affected. In addition, A53T expressing neurons showed impairment in mitochondrial membrane potential and mitochondrial respiratory function. Furthermore, we found that rapamycin, an autophagy inducer, rescued the decreased mitochondrial mobility. Taken together, these data demonstrate that A53T ?-syn impairs mitochondrial function and dynamics and the deficit of mitochondrial transport is reversible, providing further understanding of the disease pathogenesis and a potential therapeutic strategy for PD.
Project description:Mutations in GBA1, the gene encoding glucocerebrosidase, are associated with an enhanced risk of developing synucleinopathies such as Parkinson's disease (PD) and dementia with Lewy bodies. A higher prevalence and increased severity of motor and non-motor symptoms is observed in PD patients harboring mutant GBA1 alleles, suggesting a link between the gene or gene product and disease development. Interestingly, PD patients without mutations in GBA1 also exhibit lower levels of glucocerebrosidase activity in the central nervous system (CNS), implicating this lysosomal enzyme in disease pathogenesis. Here, we investigated whether modulation of glucocerebrosidase activity in murine models of synucleinopathy (expressing wild type Gba1) affected ?-synuclein accumulation and behavioral phenotypes. Partial inhibition of glucocerebrosidase activity in PrP-A53T-SNCA mice using the covalent inhibitor conduritol-B-epoxide induced a profound increase in soluble ?-synuclein in the CNS and exacerbated cognitive and motor deficits. Conversely, augmenting glucocerebrosidase activity in the Thy1-SNCA mouse model of PD delayed the progression of synucleinopathy. Adeno-associated virus-mediated expression of glucocerebrosidase in the Thy1-SNCA mouse striatum led to decrease in the levels of the proteinase K-resistant fraction of ?-synuclein, amelioration of behavioral aberrations and protection from loss of striatal dopaminergic markers. These data indicate that increasing glucocerebrosidase activity can influence ?-synuclein homeostasis, thereby reducing the progression of synucleinopathies. This study provides robust in vivo evidence that augmentation of CNS glucocerebrosidase activity is a potential therapeutic strategy for PD, regardless of the mutation status of GBA1.
Project description:Both ?-Synuclein (?Syn) accumulation and mitochondrial dysfunction have been implicated in the pathology of Parkinson's disease (PD). Although studies suggest that ?Syn and its missense mutant, A53T, preferentially accumulate in the mitochondria, the mechanisms by which ?Syn and mitochondrial proteins regulate each other to trigger mitochondrial and neuronal toxicity are poorly understood. ATP-dependent Clp protease (ClpP), a mitochondrial matrix protease, plays an important role in regulating mitochondrial protein turnover and bioenergetics activity. Here, we show that the protein level of ClpP is selectively decreased in ?Syn-expressing cell culture and neurons derived from iPS cells of PD patient carrying ?Syn A53T mutant, and in dopaminergic (DA) neurons of ?Syn A53T mice and PD patient postmortem brains. Deficiency in ClpP induces an overload of mitochondrial misfolded/unfolded proteins, suppresses mitochondrial respiratory activity, increases mitochondrial oxidative damage and causes cell death. Overexpression of ClpP reduces ?Syn-induced mitochondrial oxidative stress through enhancing the level of Superoxide Dismutase-2 (SOD2), and suppresses the accumulation of ?Syn S129 phosphorylation and promotes neuronal morphology in neurons derived from PD patient iPS cells carrying ?Syn A53T mutant. Moreover, we find that ?Syn WT and A53T mutant interact with ClpP and suppress its peptidase activity. The binding of ?Syn to ClpP further promotes a distribution of ClpP from soluble to insoluble cellular fraction in vitro and in vivo, leading to reduced solubility of ClpP. Compensating for the loss of ClpP in the substantia nigra of ?Syn A53T mice by viral expression of ClpP suppresses mitochondrial oxidative damage, and reduces ?Syn pathology and behavioral deficits of mice. Our findings provide novel insights into the mechanism underlying ?Syn-induced neuronal pathology, and they suggest that ClpP might be a useful therapeutic target for PD and other synucleinopathies.
Project description:Parkinson's disease (PD) pathology is characterized by the formation of intra-neuronal inclusions called Lewy bodies, which are comprised of alpha-synuclein (?-syn). Duplication, triplication or genetic mutations in ?-syn (A53T, A30P and E46K) are linked to autosomal dominant PD; thus implicating its role in the pathogenesis of PD. In both PD patients and mouse models, there is increasing evidence that neuronal dysfunction occurs before the accumulation of protein aggregates (i.e., ?-syn) and neurodegeneration. Characterization of the timing and nature of symptomatic dysfunction is important for understanding the impact of ?-syn on disease progression. Furthermore, this knowledge is essential for identifying pathways and molecular targets for therapeutic intervention. To this end, we examined various functional and morphological endpoints in the transgenic mouse model expressing the human A53T ?-syn variant directed by the mouse prion promoter at specific ages relating to disease progression (2, 6 and 12 months of age). Our findings indicate A53T mice develop fine, sensorimotor, and synaptic deficits before the onset of age-related gross motor and cognitive dysfunction. Results from open field and rotarod tests show A53T mice develop age-dependent changes in locomotor activity and reduced anxiety-like behavior. Additionally, digigait analysis shows these mice develop an abnormal gait by 12 months of age. A53T mice also exhibit spatial memory deficits at 6 and 12 months, as demonstrated by Y-maze performance. In contrast to gross motor and cognitive changes, A53T mice display significant impairments in fine- and sensorimotor tasks such as grooming, nest building and acoustic startle as early as 1-2 months of age. These mice also show significant abnormalities in basal synaptic transmission, paired-pulse facilitation and long-term depression (LTD). Combined, these data indicate the A53T model exhibits early- and late-onset behavioral and synaptic impairments similar to PD patients and may provide useful endpoints for assessing novel therapeutic interventions for PD.
Project description:Mechanisms underlying ?-synuclein (?Syn) mediated neurodegeneration are poorly understood. Intramuscular (IM) injection of ?Syn fibrils in human A53T transgenic M83+/- mice produce a rapid model of ?-synucleinopathy with highly predictable onset of motor impairment. Using varying doses of ?Syn seeds, we show that ?Syn-induced phenotype is largely dose-independent. We utilized the synchrony of this IM model to explore the temporal sequence of ?Syn pathology, neurodegeneration and neuroinflammation. Longitudinal tracking showed that while motor neuron death and ?Syn pathology occur within 2?months post IM, astrogliosis appears at a later timepoint, implying neuroinflammation is a consequence, rather than a trigger, in this prionoid model of synucleinopathy. Initiating at 3?months post IM, immune activation dominates the pathologic landscape in terminal IM-seeded M83+/- mice, as revealed by unbiased transcriptomic analyses. Our findings provide insights into the role of neuroinflammation in ?Syn mediated proteostasis and neurodegeneration, which will be key in designing potential therapies.