Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

One of the hallmarks of Parkinson's disease (PD) is pathological structure, termed Lewy body, containing inclusions of ubiquitinated proteins in the dopaminergic neurons in the substantia nigra. The mechanism leading to the formation of these aggregates is unclear, although it has been shown that mutations in alpha-synuclein or in the ubiquitin-related enzyme UCH-L1 might induce such protein aggregation. We, therefore, examined the possible role of 6-hydroxydopamine (6-OHDA), a dopaminergic neurotoxin used in PD experimental models, in causing protein degradation and its association with the ubiquitin system. Using antiubiquitin antibodies we found that exposure of SH-SY5Y neuroblastoma and PC-12 cell lines to 6-OHDA increased the levels of free ubiquitin and ubiquitin-conjugated proteins, in a dose-dependent manner. Furthermore, metabolic labeling with 35S-methionine, demonstrated that 6-OHDA markedly increased protein degradation, as indicated by the secretion of protein metabolites to the medium. Inhibition of the proteasome activity by the specific inhibitor MG132, attenuated the protein degradation induced by 6-OHDA and potentiated its toxicity. Administration of the antioxidant N-acetylcysteine to the 6-OHDA-treated cells, increased cell survival and reduced protein degradation. In conclusion, our findings suggest that 6-OHDA toxicity is associated with protein degradation and ubiquitin-proteasome system activation.
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PMID:6-Hydroxydopamine increases ubiquitin-conjugates and protein degradation: implications for the pathogenesis of Parkinson's disease. 1204 47

Mutations in the parkin gene cause autosomal recessive inherited juvenile parkinsonism (ARJP) and account for the majority of cases of inherited Parkinson's disease (PD) of young onset (<45 years of age). Patients with parkin mutations commonly have atypical clinical features such as dystonia at onset, hyper-reflexia, diurnal fluctuations, and sleep benefit; however, parkin mutation patients with both typical PD symptoms and older age of onset have been identified. Parkin is a ubiquitin protein ligase (E3), a component in the pathway that attaches ubiquitin to specific proteins, designating them for degradation by the proteasome. Several substrates for parkin have been identified (CDCrel-1, o-glycosylated alpha-synuclein, parkin associated endothelin-like cell receptor, and synphilin). The role of these substrates in the pathogenesis of ARJP is under active study. Most patients with parkin mutations lack Lewy bodies, suggesting that functional parkin is involved in the formation of these highly ubiquitinated inclusions. Furthermore, the recognition that parkin mutations can lead to a disorder clinically similar to sporadic PD, but presumably lacking Lewy bodies, calls into question the necessity of Lewy bodies for the diagnosis of PD and nigral cell death. Studies of parkin are increasing the focus on the role of the ubiquitin-proteasome system in the pathogenesis of both familial and sporadic PD.
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PMID:Significance of the parkin gene and protein in understanding Parkinson's disease. 1204 48

Mutations in alpha-synuclein, parkin and ubiquitin C-terminal hydrolase L1, and defects in 26/20S proteasomes, cause or are associated with the development of familial and sporadic Parkinson's disease (PD). This suggests that failure of the ubiquitin-proteasome system (UPS) to degrade abnormal proteins may underlie nigral degeneration and Lewy body formation that occur in PD. To explore this concept, we studied the effects of lactacystin-mediated inhibition of 26/20S proteasomal function and ubiquitin aldehyde (UbA)-induced impairment of ubiquitin C-terminal hydrolase (UCH) activity in fetal rat ventral mesencephalic cultures. We demonstrate that both lactacystin and UbA caused concentration-dependent and preferential degeneration of dopaminergic neurons. Inhibition of 26/20S proteasomal function was accompanied by the accumulation of alpha-synuclein and ubiquitin, and the formation of inclusions that were immunoreactive for these proteins, in the cytoplasm of VM neurons. Inhibition of UCH was associated with a loss of ubiquitin immunoreactivity in the cytoplasm of VM neurons, but there was a marked and localized increase in alpha-synuclein staining which may represent the formation of inclusions bodies in VM neurons. These findings provide direct evidence that impaired protein clearance can induce dopaminergic cell death and the formation of proteinaceous inclusion bodies in VM neurons. This study supports the concept that defects in the UPS may underlie nigral pathology in familial and sporadic forms of PD.
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PMID:Impairment of the ubiquitin-proteasome system causes dopaminergic cell death and inclusion body formation in ventral mesencephalic cultures. 1206 77

The proteolytic activities of 26/20S proteasomes are impaired in the substantia nigra pars compacta (SNc) in sporadic Parkinson's disease (PD). In the present study, we examined the structural integrity of the proteasome by determining the levels of the beta- and alpha-subunits which together normally constitute the catalytic core of 26/20S proteasomes. Western blot analyzes and immunohistochemical staining revealed a major and selective loss of alpha-subunits in dopaminergic neurons of the SNc but not in other brain regions in sporadic PD. This defect is known to cause the proteasome to become unstable and prevents its assembly with resultant impairment of enzymatic activity. Thus, structural and function defects in 26/20S proteasomes may underlie protein accumulation, formation of proteinaceous Lewy bodies and dopaminergic neuronal death in the SNc in sporadic PD.
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PMID:Selective loss of 20S proteasome alpha-subunits in the substantia nigra pars compacta in Parkinson's disease. 1209 45

Because genetic defects relating to the ubiquitin-proteasome system were reported in familial parkinsonism, we evaluated proteasomal function in autopsied brains with sporadic Parkinson's disease. We found that proteasome peptidase activities in a fraction specific to the proteasome were preserved in five brain areas (including the striatum) of Parkinson's disease where neuronal loss is not observed. Striatal protein levels of two proteasome subunits were normal in Parkinson's disease but reduced mildly in disease controls (multiple system atrophy). Our brain data suggest that a systemic, global disturbance in the catalytic activity and degradation ability of the proteasome itself is unlikely to explain the cause of Parkinson's disease.
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PMID:Brain proteasomal function in sporadic Parkinson's disease and related disorders. 1211 87

Parkinson's disease is a neurodegenerative disorder characterized by the progressive degeneration of the dopaminergic nigrostriatal pathway, and the presence of Lewy bodies. Over the past few years, several genes involved in inherited forms of the disease have been uncovered. In a small number of families with autosomal dominant inheritance, mutations have been identified in the genes encoding a-synuclein and ubiquitin carboxy-terminal hydrolase L1. Mutations in the parkin gene are a common cause of autosomal recessive parkinsonism with early onset, and also account for more than 15% of isolated cases with onset before age 45. The function of Parkin, a ubiquitin ligase involved in the degradation of protein substrates by the ubiquitin-proteasome pathway, highlights that ubiquitin-mediated proteolysis may play an important role in the pathophysiology of idiopathic Parkinson's disease.
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PMID:[Parkin, alpha-synuclein and other molecular aspects of Parkinson's disease]. 1213 40

Mutations in the alpha-synuclein gene (A30P and A53T) are reported to cause familial Parkinson's disease (PD), but it is not known how they result in selective dopaminergic cell death. Here we report on effects of mutant alpha-synucleins on dopamine transporter (DAT)-mediated toxicity of the selective dopaminergic neurotoxin 1-methyl-4-phenylpyridinium ion (MPP+) in vitro. We established human embryonic kidney HEK-293 cell lines stably co-expressing each alpha-synuclein isoform and the human DAT. We demonstrate that expression of all alpha-synuclein isoforms enhances toxicity of general complex I inhibition (rotenone), but only the expression of mutant alpha-synucleins induces significant increased DAT-dependent toxicity of very low concentrations of MPP+ compared to wild-type protein. Proteasomal inhibition by lactacystin does not alter MPP+-toxicity in all cell lines. Our data suggest a new mechanism of MPP+-induced dopaminergic toxicity by an interaction between mutant alpha-synucleins and the DAT, which is independent of the function of the proteasome.
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PMID:Expression of mutant alpha-synucleins enhances dopamine transporter-mediated MPP+ toxicity in vitro. 1215 87

Structural and functional defects in 26/20S proteasomes occur in the substantia nigra pars compacta and may underlie protein accumulation, Lewy body formation and dopaminergic neuronal death in Parkinson's disease. We therefore determined the pathogenicity of proteasomal impairment following stereotaxic unilateral infusion of lactacystin, a selective proteasome inhibitor, into the substantia nigra pars compacta of rats. These animals became progressively bradykinetic, adopted a stooped posture and displayed contralateral head tilting. Administration of apomorphine to lactacystin-treated rats reversed behavioral abnormalities and induced contralateral rotations. Lactacystin caused dose-dependent degeneration of dopaminergic cell bodies and processes with the cytoplasmic accumulation and aggregation of alpha-synuclein to form inclusion bodies. These findings support the notion that failure of the ubiquitin-proteasome system to degrade and clear unwanted proteins is an important etiopathogenic factor in Parkinson's disease.
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PMID:Proteasome inhibition causes nigral degeneration with inclusion bodies in rats. 1216 69

Parkinson's disease (PD) is a progressive neurodegenerative disease involving neurodegeneration of dopaminergic neurons of the substantia nigra (SN), a part of the midbrain. Oxidative stress has been implicated to play a major role in the neuronal cell death associated with PD. Importantly, there is a drastic depletion in cytoplasmic levels of the thiol tripeptide glutathione within the SN of PD patients. Glutathione (GSH) exhibits several functions in the brain chiefly acting as an antioxidant and a redox regulator. GSH depletion has been shown to affect mitochondrial function probably via selective inhibition of mitochondrial complex I activity. An important biochemical feature of neurodegeneration during PD is the presence of abnormal protein aggregates present as intracytoplasmic inclusions called Lewy bodies. Oxidative damage via GSH depletion might also accelerate the build-up of defective proteins leading to cell death of SN dopaminergic neurons by impairing the ubiquitin-proteasome pathway of protein degradation. Replenishment of normal glutathione levels within the brain may hold an important key to therapeutics for PD. Several reports have suggested that iron accumulation in the SN patients might also contribute to oxidative stress during PD.
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PMID:Glutathione, iron and Parkinson's disease. 1221 3

Many studies have suggested the ubiquitin-proteasome system played an essential role in the pathogenesis of neurodegenerative disorders. In 1999, we provided evidence that a mutation of the system could directly cause neurodegeneration using the gad mouse. Namely, we identified the gad mutation was caused by an intragenic deletion of a gene encoding ubiquitin C-terminal hydrolase 1(UCH-L1), which is a member of de-ubiquitinating enzyme family. In human, missense mutation of UCH-L1 gene was reported in a German family with Parkinson's disease. As well, the parkin gene product was revealed to be an E3 ubiquitin ligase which recognize a form of alpha-synuclein as a substrate. Thus, the investigation of the ubiquitin-proteasome system should provide a clue for understanding neurodegeneration. We have characterized UCH-L1 and identified candidates of endogenous substrates as well as interacting proteins of UCH-L1. In addition, we found amount of monomeric ubiquitin was decreased in the brain of the gad mouse compared with wild type mice. We have also tried to develop "protein therapy" using UCH-L1 protein with TAT sequence. We observed the protein was delivered to brain after intraperitoneal injection in the wild type mouse. This approach would provide a new therapeutic strategy for neurodegeneration.
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PMID:[The ubiquitin-proteasome system and neurodegeneration]. 1223 99


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