The Ile93Met mutation in the ubiquitin carboxy-terminal-hydrolase-L1 gene is not observed in European cases with familial Parkinson's disease

Role of Deubiquitinases in Parkinson's Disease-Therapeutic Perspectives

Parkinson's disease (PD) is a neurodegenerative disorder that has been associated with mitochondrial dysfunction, oxidative stress, and defects in mitophagy as well as α-synuclein-positive inclusions, termed Lewy bodies (LBs), which are a common pathological hallmark in PD. Mitophagy is a process that maintains cellular health by eliminating dysfunctional mitochondria, and it is triggered by ubiquitination of mitochondrial-associated proteins-e.g., through the PINK1/Parkin pathway-which results in engulfment by the autophagosome and degradation in lysosomes. Deubiquitinating enzymes (DUBs) can regulate this process at several levels by deubiquitinating mitochondrial substrates and other targets in the mitophagic pathway, such as Parkin. Moreover, DUBs can affect α-synuclein aggregation through regulation of degradative pathways, deubiquitination of α-synuclein itself, and/or via co-localization with α-synuclein in inclusions. DUBs with a known association to PD are described in this paper, along with their function. Of interest, DUBs could be useful as novel therapeutic targets against PD through regulation of PD-associated defects.

Drosophila Ubiquitin C-Terminal Hydrolase Knockdown Model of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. Many factors have been shown to contribute to its pathogenesis including genetic and environmental factors. Ubiquitin C-terminal hydrolase L1 (UCHL1) is also known to be involved in the pathogenesis of PD. We herein modeled the study of UCHL1 in Drosophila melanogaster and investigated its functions in PD. The specific knockdown of the Drosophila ortholog of UCHL1 (dUCH) in dopaminergic neurons (DA neurons) led to the underdevelopment and/or degeneration of these neurons, specifically in DL1 DA neuron cluster in the larval brain lobe and PPM2, PPM3, PPL2ab, and VUM DA neuron clusters in the adult brain. These defects were followed by a shortage of dopamine in the brain, which subsequently resulted in locomotor dysfunction. The degeneration of DA neurons in dUCH knockdown adult brain, which occurred progressively and severely during the course of aging, mimics the epidemiology of PD. DA neuron and locomotor defects were rescued when dUCH knockdown flies were treated with vitamin C, a well-known antioxidant. These results suggest that dUCH knockdown fly is a promising model for studying the pathogenesis and epidemiology of PD as well as the screening of potential antioxidants for PD therapeutics.

Porcine UCHL1: genomic organization, chromosome localization and expression analysis

The human UCHL1 gene encodes the ubiquitin C-terminal hydrolase UCHL1, which comprises more than 2% of total brain protein. UCHL1 is a component of the ubiquitin-proteasome system, which degrades overexpressed and damaged proteins. Mutations in the UCHL1 gene are associated with susceptibility to and protection from Parkinson's disease. Here we report cloning, characterization, expression analysis and mapping of porcine UCHL1. The UCHL1 cDNA was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) using oligonucleotide primers derived from in silico sequences. The porcine cDNA codes for a protein of 223 amino acids which shows a very high similarity to human (98%) and to mouse (97%) UCHL1. In addition, the genomic organization of the porcine UCHL1 gene was determined. The porcine UCHL1 gene was mapped to chromosome 8(½p21)-p23. Three SNPs were found in the porcine UCHL1 sequence. Expression analysis by quantitative real time RT-PCR demonstrated that porcine UCHL1 mRNA is differentially expressed in various organs and tissues and similar to its human counterpart. UCHL1 transcript is most abundant in brain tissues and in the spinal cord. The UCHL1 mRNA expression was also investigated in developing porcine embryos. UCHL1 transcript was detected as early as 40 days of gestation. A significant decrease in UCHL1 transcript was detected in basal ganglia from day 60 to day 115 of gestation.

Association between the ubiquitin carboxyl-terminal esterase L1 gene (UCHL1) S18Y variant and Parkinson's Disease: a HuGE review and meta-analysis

The ubiquitin carboxyl-terminal esterase L1 gene, UCHL1, located on chromosome 4p14, has been studied as a potential candidate gene for Parkinson's disease risk. The authors conducted a Human Genome Epidemiology review and meta-analysis of published case-control studies of the UCHL1 S18Y variant and Parkinson's disease in Asian and Caucasian samples. The meta-analysis of studies in populations of Asian ancestry showed a statistically significant association between the Y allele and reduced risk of Parkinson's disease under a recessive model (odds ratio (OR) for YY vs. SY + SS = 0.79, 95% confidence interval (CI): 0.67, 0.94; P = 0.006). For a dominant model, the association was not significant in Asian populations (OR for YY + SY vs. SS = 0.88, 95% CI: 0.68, 1.14; P = 0.33). For populations of European ancestry, the meta-analysis showed a significant association between the Y allele and decreased risk of Parkinson's disease under a dominant model (OR = 0.89, 95% CI: 0.81, 0.98; P = 0.02) but not under a recessive model (OR = 0.92, 95% CI: 0.66, 1.30; P = 0.65). Using the Venice criteria, developed by the Human Genome Epidemiology Network Working Group on the assessment of cumulative evidence, the authors concluded that moderate evidence exists for an association between the S18Y variant and Parkinson's disease.

Pathogenesis of familial Parkinson's disease: new insights based on monogenic forms of Parkinson's disease

Parkinson's disease (PD) is one of the most common movement disorders caused by the loss of dopaminergic neuronal cells. The molecular mechanisms underlying neuronal degeneration in PD remain unknown; however, it is now clear that genetic factors contribute to the pathogenesis of this disease. Approximately, 5% of patients with clinical features of PD have clear familial etiology, which show a classical recessive or dominant Mendelian mode of inheritance. Over the decade, more than 15 loci and 11 causative genes have been identified so far and many studies shed light on their implication in not only monogenic but also sporadic form of PD. Recent studies revealed that PD-associated genes play important roles in cellular functions, such as mitochondrial functions, ubiquitin-proteasomal system, autophagy-lysosomal pathway and membrane trafficking. Furthermore, the proteins encoded by PD-associated genes can interact with each other and such gene products may share a common pathway that leads to nigral degeneration. However, their precise roles in the disease and their normal functions remain poorly understood. In this study, we review recent progress in knowledge about the genes associated with familial PD.

Lack of evidence for association of a UCH-L1 S18Y polymorphism with Parkinson's disease in a Han-Chinese population

Mutation in UCH-L1 has been reported as a rare cause of autosomal dominant Parkinson's disease (PD). A S18Y polymorphism in the same gene has been associated with sporadic PD. We investigated the frequency of this polymorphism among the Han-Chinese ethnic population in a case-control study. A total of 600 patients with PD and 334 unrelated healthy controls were genotyped using PCR-restriction fragment length polymorphism analysis. We did not observe any difference in allele or genotype frequencies between the cases and the controls (P>0.05). Our results do not support a role for this variant in sporadic PD.

Merging mouse transcriptome analyses with Parkinson's disease linkage studies

The hallmark of Parkinson's disease (PD OMIM #168600) is the degeneration of the nigral dopaminergic system affecting approximately 1% of the human population older than 65. In pursuit of genetic factors contributing to PD, linkage and association studies identified several susceptibility genes. The majority of these genes are expressed by the dopamine-producing neurons in the substantia nigra. We, therefore, propose expression by these neurons as a selection criterion, to narrow down, in a rational manner, the number of candidate genes in orphan PD loci, where no mutation has been associated thus far. We determined the corresponding human chromosome locations of 1435 murine cDNA fragments obtained from murine expression analyses of nigral dopaminergic neurons and combined these data with human linkage studies. These fragments represent 19 genes within orphan OMIM PD loci. We used the same approach for independent association studies and determined the genes in neighborhood to the peaks with the highest LOD score value. Our approach did not make any assumptions about disease mechanisms, but it, nevertheless, revealed α-synuclein, NR4A2 (Nurr1), and the tau genes, which had previously been associated to PD. Furthermore, our transcriptome analysis identified several classes of candidate genes for PD mutations and may also provide insight into the molecular pathways active in nigral dopaminergic neurons.

Parkinson's disease: the genetics of a heterogeneous disorder

Since the first description of Parkinson's disease (PD) in 1817 attempts have been made to resolve the etiology of this common neurodegenerative disorder. In the last century the influence of heredity in PD was controversial. The identification of mutations in six genes responsible for Mendelian forms of PD; alpha-synuclein (SNCA), parkin (PRKN), ubiquitin C-terminal hydrolase L1 (UCH-L1), oncogene DJ-1, PTEN-induced putative kinase 1 (PINK1), and most recently leucine-rich repeat kinase 2 (LRRK2), has confirmed the role of genetics in familial forms of the disease. The exact relationship of these familial disorders and related genes to the more common sporadic form is currently uncertain. The identification of LRRK2 mutations and the association of common variants in SNCA and UCH-L1 in apparently sporadic late-onset disease indicate these genes may be of greater importance than previously believed. The protein products of the six genes are involved in different pathways of neurodegeneration and have opened new avenues of research. This focused research will lead to the development of novel targeted therapies, which may revolutionize the treatment of PD for a substantial proportion of patients.

Genética de las enfermedades neurodegenerativas más prevalentes

A large number of mutations and polymorphisms associated with neurodegenerative disorders have been described during the last years. These findings have been helpful to improve our knowledge about the pathogenesis of these disorders. In this review we describe the genetic alterations and variants that cause or predispose to develop several neurodegenerative disorders, such as Huntington's disease, Alzheimer's disease, frontotemporal dementia, Parkinson's disease and other parkinsonisms. We also comment on the possible pathogenic mechanism of these mutations, clinical features and the usefulness of this information for the diagnosis and management of these disorders.

Oxidative stress regulated expression of Ubiquitin Carboxyl-terminal Hydrolase-L1: Role in cell survival

The ubiquitin Carboxyl-terminal Hydrolase-L1 gene (UCHL1) is a key enzyme in the protein degradation pathway; however, its precise role in protecting cells under stress conditions is unclear. In the present study we investigated the activity of this gene in human NT2/D1 embryonal carcinoma cells subjected to oxygen-glucose deprivation (OGD) and reoxygenation. OGD/reoxygenation cause global metabolic changes due to energy withdrawal and the subsequent generation of reactive oxygen species which initiates either a stress-adaptation-survival response or cell death, depending on the severity of the insult. A bi-phasic change in UCHL1 expression was observed by Q-PCR, Western blotting and flow cytometry. Down regulation of UCHL1 was detected immediately after OGD treatment and its expression was subsequently restored and increased 6 h after OGD treatment as well as during reoxygenation. Furthermore, flow cytometry analysis detected a lower level of UCHL1 only in apoptotic cells that had severe loss of mitochondrial membrane potential. Accordingly, down-regulation of endogenous UCHL1 by antisense cDNA in mouse N2a neuroblastoma cells increased the cell's sensitivity to OGD treatment. This down-regulation of endogenous UCHL1 led to the accumulation of p27, suggesting that UCHL1 is an essential gene to maintain cell homeostasis under normal growth and oxidative stress conditions.

Synuclein, dopamine and oxidative stress: co-conspirators in Parkinson's disease?

The etiology of Parkinson's disease (PD) is presently unknown. The unifying hallmark of disease is depletion of dopamine and loss of nigrostriatal dopamine neurons. Familial and sporadic forms of the disease are described. The familial mutations occur within alpha-synuclein and molecules involved in protein degradation and mitochondrial function. Sporadic PD is thought to involve the interplay of genetic and environmental factors. Despite disparate initiating triggers, a convergent pathobiologic model for this common neurodegenerative disease has been proposed. Likely players have emerged that may form the basis for this common pathway model of disease. In this review, we examine the role of three most implicated PD pathogenic conspirators: synuclein, dopamine and oxidative stress.

Proteome analysis of human substantia nigra in Parkinson's disease

Protein expression has been compared in human substantia nigra specimens from Parkinson's disease (PD) patients and from controls, and 44 proteins expressed in this midbrain region were identified by peptide mass fingerprinting. Among them, nine showed changes in their abundance. L and M neurofilament chains are less abundant in PD specimens, whereas peroxiredoxin II, mitochondrial complex III, ATP synthase D chain, complexin I, profilin, L-type calcium channel delta-subunit, and fatty-acid binding protein are significantly more present in PD samples than in controls. Besides the consolidated view of oxidative stress involvement in PD pathogenesis, suggested by overexpression of mitochondrial and reactive oxygen species (ROS)-scavenging proteins, these results indicate a possible potentiation mechanism of afferent signals to substantia nigra following degeneration of dopaminergic neurons.

Genetic contributions to Parkinson's disease

Sporadic Parkinson's disease (PD) is a common neurodegenerative disorder, characterized by the loss of midbrain dopamine neurons and Lewy body inclusions. It is thought to result from a complex interaction between multiple predisposing genes and environmental influences, although these interactions are still poorly understood. Several causative genes have been identified in different families. Mutations in two genes [alpha-synuclein and nuclear receptor-related 1 (Nurr1)] cause the same pathology, and a third locus on chromosome 2 also causes this pathology. Other familial PD mutations have identified genes involved in the ubiquitin-proteasome system [parkin and ubiquitin C-terminal hydroxylase L1 (UCHL1)], although such cases do not produce Lewy bodies. These studies highlight critical cellular proteins and mechanisms for dopamine neuron survival as disrupted in Parkinson's disease. Understanding the genetic variations impacting on dopamine neurons may illuminate other molecular mechanisms involved. Additional candidate genes involved in dopamine cell survival, dopamine synthesis, metabolism and function, energy supply, oxidative stress, and cellular detoxification have been indicated by transgenic animal models and/or screened in human populations with differing results. Genetic variation in genes known to produce different patterns and types of neurodegeneration that may impact on the function of dopamine neurons are also reviewed. These studies suggest that environment and genetic background are likely to have a significant influence on susceptibility to Parkinson's disease. The identification of multiple genes predisposing to Parkinson's disease will assist in determining the cellular pathway/s leading to the neurodegeneration observed in this disease.

Genetic causes of Parkinson?s disease: UCHL-1

The ubiquitin proteasome system is an important cellular pathway that ubiquitinates damaged proteins and degrades them via the 26S proteasome. Abnormalities of this pathway can result in molecular protein aggregation and have been associated with Parkinson's disease (PD). UCHL-1, an enzyme central to the system, possesses catalytic hydrolase activity that can hydrolyze peptide-ubiquitin bonds and recycle ubiquitin monomers for re-use in the same process. Recently, UCHL-1 has been shown to possess a second dimerisation-dependent ligase activity and, at least in vitro, this ligase activity promotes alpha synuclein aggregation. UCHL-1 was first implicated in PD by the discovery of an I93M mutation identified in a German sib-pair with probable autosomal dominant PD. Although no further UCHL-1 mutations have been identified, a common non-synonymous S18Y polymorphism has been suggested to reduce disease susceptibility in non-mendelian forms of PD. In vitro functional data support this protective effect, with evidence that S18Y possesses reduced ligase activity compared with wild type UCHL-1. One study has found increased hydrolase activity associated with S18Y, although another study has not. Important issues regarding UCHL-1 and its role in PD remain inconclusive, especially regarding the pathogenicity of the mendelian I93M mutation. This review tries to address some of these uncertainties.

Genes, proteins, and neurotoxins involved in Parkinson’s disease

Parkinson's disease (PD) is a common neurodegenerative disorder. The etiology of PD is likely due to combinations of environmental and genetic factors. In addition to the loss of neurons, including dopaminergic neurons in the substantia nigra pars compacta, a further morphologic hallmark of PD is the presence of Lewy bodies and Lewy neurites. The formation of these proteinaceous inclusions involves interaction of several proteins, including alpha-synuclein, synphilin-1, parkin and UCH-L1. Animal models allow to get insight into the mechanisms of several symptoms of PD, allow investigating new therapeutic strategies and, in addition, provide an indispensable tool for basic research. In animals PD does not arise spontaneously, thus, characteristic and specific functional changes have to be mimicked by application of neurotoxic agents or by genetic manipulations. In this review we will focus on genes and gene loci involved in PD, the functions of proteins involved in the formation of cytoplasmatic inclusions, their interactions, and their possible role in PD. In addition, we will review the current animal models of PD.

SEPT5_v2 is a parkin-binding protein

Mutations in parkin are associated with various inherited forms of Parkinson's disease (PD). Parkin is a ubiquitin ligase enzyme that catalyzes the covalent attachment of ubiquitin moieties onto substrate proteins destined for proteasomal degradation. The substrates of parkin-mediated ubiquitination have yet to be completely identified. Using a yeast two-hybrid screen, we isolated the septin, human SEPT5_v2 (also known as cell division control-related protein 2), as a putative parkin-binding protein. SEPT5_v2 is highly homologous to another septin, SEPT5, which was recently identified as a target for parkin-mediated ubiquitination. SEPT5_v2 binds to parkin at the amino terminus and in the ring finger domains. Several lines of evidence have validated the putative link between parkin and SEPT5_v2. Parkin co-precipitates with SEPT5_v2 from human substantia nigra lysates. Parkin ubiquitinates SEPT5_v2 in vitro, and both SEPT5_v1 and SEPT5_v2 accumulate in brains of patients with ARJP, suggesting that parkin is essential for the normal metabolism of these proteins. These findings suggest that an important relationship exists between parkin and septins.

Dysfunction of mitochondrial complex I and the proteasome: interactions between two biochemical deficits in a cellular model of Parkinson's disease

Two biochemical deficits have been described in the substantia nigra in Parkinson's disease, decreased activity of mitochondrial complex I and reduced proteasomal activity. We analysed interactions between these deficits in primary mesencephalic cultures. Proteasome inhibitors (epoxomicin, MG132) exacerbated the toxicity of complex I inhibitors [rotenone, 1-methyl-4-phenylpyridinium (MPP+)] and of the toxic dopamine analogue 6-hydroxydopamine, but not of inhibitors of mitochondrial complex II-V or excitotoxins [N-methyl-d-aspartate (NMDA), kainate]. Rotenone and MPP+ increased free radicals and reduced proteasomal activity via adenosine triphosphate (ATP) depletion. 6-hydroxydopamine also increased free radicals, but did not affect ATP levels and increased proteasomal activity, presumably in response to oxidative damage. Proteasome inhibition potentiated the toxicity of rotenone, MPP+ and 6-hydroxydopamine at concentrations at which they increased free radical levels >/= 40% above baseline, exceeding the cellular capacity to detoxify oxidized proteins reduced by proteasome inhibition, and also exacerbated ATP depletion caused by complex I inhibition. Consistently, both free radical scavenging and stimulation of ATP production by glucose supplementation protected against the synergistic toxicity. In summary, proteasome inhibition increases neuronal vulnerability to normally subtoxic levels of free radicals and amplifies energy depletion following complex I inhibition.

Convergent pathobiologic model of Parkinson's disease

The etiology of Parkinson's disease (PD) has yet to be delineated. Human genetic studies as well as neurotoxicant and transgenic animal models of PD suggest that multiple events trigger the initiation of this progressive age-related neurodegenerative disorder. In addition, we propose that despite disparate disease triggers a convergent pathobiologic pathway exists leading to cell death. The common pathway model posits that both familial and sporadic forms of Parkinson's disease obligately share a common pathophysiological substrate. Herein we discuss the evidence for a common pathway model of Parkinson's disease through a review of synuclein transgenic models and outline an approach for the identification of shared therapeutic targets. We end with a discussion of a potential alternative therapy for Parkinson's disease.

Genetic and environmental factors in the cause of Parkinson's disease

Despite being the subject of intense study, the pathogenesis of Parkinson's disease still remains unclear. In recent years, however, there has been increasing evidence to support a role for genetic factors in its cause. This has come from twin and family studies, the mapping and cloning of PARK genes that are associated with the development of PD, and analysis of potential susceptibility genes. There is also evidence indicating that environmental factors may play a role in the disease process. It is likely that for most cases, there is a complex interplay between these genetic and environmental influences in the causation of Parkinson's disease. This article reviews the evidence in support of genetic and environmental factors in the cause of PD.

Genes and parkinsonism

Genetic studies in families with mendelian inheritance of Parkinson's disease (PD) have reported the cloning of several disease-associated genes. These studies of rare familial forms of the disease have cast doubt on our understanding of the role of genetics in typical PD and have complicated the classification of the disorder. However, this genetic information might help us to construct a hypothesis for the pathogenetic processes that underlie PD. In this review we describe the molecular genetics of PD as currently understood to help explain the pathways that underlie neurodegeneration.

S18Y polymorphism in the UCH-L1 gene and Parkinson's disease: evidence for an age-dependent relationship

We studied the relationship between Parkinson's disease (PD) and the S18Y polymorphism in the UCH-L1 gene and the effect on this relationship of age at onset, smoking, and pesticides. Patients requested free health coverage for PD to the Mutualité Sociale Agricole (MSA), the French health insurance organization for people whose work is related to agriculture. Controls requested reimbursement of health expenses to the MSA. A maximum of three controls were matched to each case. Analyses included participants with both parents born in Europe. There were no differences in S18Y genotypes between patients (n = 209; 67% SS, 32% SY, 1% YY) and controls (n = 488; 66% SS, 30% SY, 4% YY). The relationship between PD and S18Y was modified by age at onset (P = 0.03). The Y allele was inversely associated with PD for patients with onset before 61 years (odds ratio [OR] = 0.53; 95% confidence interval [CI], 0.29-0.99); there was no association for older patients (62-68 years: OR = 1.21; 95% CI, 0.67-2.20; >68 years: OR = 1.24; 95% CI, 0.67-2.31). Among patients, Y carriers had a later onset than noncarriers (P = 0.04). These findings were not modified or confounded by smoking and pesticides. In this community-based case-control study, carriers of the Y allele were at decreased risk of developing PD at a young age, independently of pesticides and smoking.

Lysosomal malfunction accompanies alpha-synuclein aggregation in a progressive mouse model of Parkinson's disease

We have detected granular and filamentous inclusions that are alpha-synuclein- and ubiquitin-immunoreactive in the cytoplasm of dopaminergic and cortical neurons of C57/black mice treated chronically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and probenecid. The immunoreactive aggregates only become evident several weeks after large-scale dopaminergic cell death and a downregulation of alpha-synuclein gene expression. Numerous lipofuscin granules accumulate alpha-synuclein in the nigral and limbic cortical neurons of treated mice. These data provide evidence that insoluble proteins, such as alpha-synuclein, build up as granular and filamentous inclusions in dopaminergic neurons that survive the initial toxic MPTP insult. They further suggest that defective protein degradation rather than altered gene expression underlies deposition of alpha-synuclein and that abundant lysosomal compartments are present to seal off the potentially toxic material.

The genetic basis of Parkinson's disease

Although the mechanisms underlying neurodegeneration in Parkinson's disease are not fully understood, considerable evidence suggests that genetic factors can influence susceptibility to the disease. In this article, we critically review this evidence and examine studies estimating patterns of inheritance. In a few families, Parkinson's disease is clearly inherited in a Mendelian fashion, and in some of these the disease causing genes have already been identified. Possible pathogenic mechanisms by which these genes cause Parkinson's disease are discussed. Further candidate genes and systematic efforts to identify genes influencing susceptibility to the disease in general are also summarised. The identification of such susceptibility genes will eventually enable us to more accurately classify this complex disease.

Parkinson's genetics: molecular insights for the new millennium

In idiopathic Parkinson's disease and familial parkinsonism, the limited number of overlapping clinical and pathological outcomes argue that a common underlying molecular pathway is perturbed. Genetic methods are a powerful approach to identify molecular components of disease. We summarize recent attempts to identify the genetic components of familial parkinsonism, without a priori assumptions about disease causation. Much effort has been expended on mapping in families with early-onset disease, in which parkinsonism appears inherited as a Mendelian trait. More recently, association methods have been employed in late-onset disease using affected sib-pairs and population isolates. These findings have been extrapolated to Parkinson's disease in the community with some success. We review the molecular synthesis now emerging from a genetic perspective.

Mutation analysis and association studies of the ubiquitin carboxy-terminal hydrolase L1 gene in Huntington's disease

Huntington's disease (HD) is attributed to a triplet CAG repeat mutation, and about 70% of the variance in age-at-onset can be explained by the size of the repeat expansion. Among potential candidates as modifier genes, we investigated the role of ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) gene. We examined the association of HD with the I93M mutation and S18Y polymorphism in 138 HD patients and 136 control subjects, but we did not identify the I93M mutation. The S18Y polymorphism was present in 17% of HD patients. Of the variance in the age-at-onset that was not accounted for by the CAG repeat, 13% could be attributed to S18Y polymorphism. We sequenced the entire coding region of the UCH-L1 gene in seven HD patients with unexplained older or younger onset age. The S18Y polymorphism was found in three out of the four patients presenting with a later age-at-onset. We conclude that the UCH-L1 gene may be a genetic factor that influences the variability in age-at-onset of HD.

ACT and UCH-L1 polymorphisms in Parkinson's disease and age of onset

alpha1-Antichymotrypsin (ACT) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) have been suggested as susceptibility factors for Parkinson's disease (PD). We replicated these findings in a Chinese case-control sample consisting of 160 PD cases and 160 carefully matched control subjects. Genotypes were determined using polymerase chain reaction and BstN1 or Rsa1 restriction enzyme assay. Analysis showed no significant difference between PD patients and controls for genotype or allele frequencies of the ACT and UCH-L1 S18Y polymorphisms. UCH-L1 S18Y polymorphism carriers, however, were found to be significantly less frequent in early-onset PD patients with a reduced risk of 0.557 (95% C.I. = 0.314-0.985; P = 0.043). These data suggest that ACT polymorphism does not influence the risk for developing PD. UCH-L1 S18Y polymorphism, however, may be a weak protective factor against early-onset PD.

Two large British kindreds with familial Parkinson's disease: a clinico-pathological and genetic study

We present the findings of a study of two large unrelated kindreds with autosomal dominant Parkinson's disease. The affected members were assessed clinically and with [(18)F]6-fluorodopa-PET and were indistinguishable from patients with the sporadic form of Parkinson's disease. In one kindred, an affected member was examined subsequently at autopsy and Lewy bodies were present in a distribution typical of sporadic Parkinson's disease. These kindreds are distinct from other Parkinsonian kindreds with identified genetic loci (PARK1-4) and provide further evidence for genetic heterogeneity in familial Parkinson's disease.

Cytosolic O-glycosylation is abundant in nerve terminals

Phosphorylation plays a key role in regulating growth cone migration and protein trafficking in nerve terminals. Here we show that nerve terminal proteins contain another abundant post-translational modification: beta-N-acetylglucosamine linked to hydroxyls of serines or threonines (O-GlcNAc(1)). O-GlcNAc modifications are essential for embryogenesis and mounting evidence suggests that O-GlcNAc is a regulatory modification that affects many phosphorylated proteins. We show that the activity and expression of O-GlcNAc transferase (OGT) and N-acetyl-beta-D-glucosaminidase (O-GlcNAcase), the two enzymes regulating O-GlcNAc modifications, are present in nerve terminal structures (synaptosomes) and are particularily abundant in the cytosol of synaptosomes. Numerous synaptosome proteins are highly modified with O-GlcNAc. Although most of these proteins are present in low abundance, we identified by proteomic analysis three neuron-specific O-GlcNAc modified proteins: collapsin response mediator protein-2 (CRMP-2), ubiquitin carboxyl hydrolase-L1 (UCH-L1) and beta-synuclein. CRMP-2, which is involved in growth cone collapse, is a major O-GlcNAc modified protein in synaptosomes. All three proteins are implicated in regulatory cascades that mediate intracellular signaling or neurodegenerative diseases. We propose that O-GlcNAc modifications in the nerve terminal help regulate the functions of these and other synaptosome proteins, and that O-GlcNAc may play a role in neurodegenerative disease.

The role of the ubiquitin-proteasomal pathway in Parkinson's disease and other neurodegenerative disorders

A unifying feature of neurodegenerative diseases is the abnormal accumulation and processing of mutant or damaged intra- and extracellular proteins; this leads to selective neuronal vulnerability and dysfunction. The ubiquitin-proteasomal pathway (UPP) is poised to play a central role in the processing of damaged and toxic proteins by ubiquitin-dependent proteolysis. The UPP can be overwhelmed in several neurodegenerative diseases. This results in the accumulation of toxic proteins and the formation of inclusions, and ultimately to neuronal dysfunction and cell death. Further analysis of the cellular and molecular mechanisms by which the UPP influences the detoxification of damaged and toxic proteins in neurodegenerative diseases could provide novel concepts and targets for the treatment and understanding of the pathogenesis of these devastating disorders.

Ubiquitin and the molecular pathology of neurodegenerative diseases

Ubiquitin plays a central role in normal cellular function as well as in disease. It is possible to group ubiquitin-immunostained structures into several main groups, the most distinctive being the ubiquitin/intermediate filament/alphaB crystallin family of inclusions that seem to represent a general cellular response to abnormal proteins recently termed the aggresomal response. While ubiquitin immunohistochemistry is a very useful technique for detecting pathological changes and inclusion bodies in the nervous system this alone is not enough to classify inclusions, and a panel of antibodies is recommended to clarify any findings made by screening tissues with anti-ubiquitin. Several mechanistic possibilities now exist to explain the accumulation of ubiquitinated proteins in cells of the nervous system, understanding of which should lead to new therapeutic advances in the group of chronic neurodegenerative diseases.

Alpha synuclein aggregation: is it the toxic gain of function responsible for neurodegeneration in Parkinson's disease?

Protein aggregation appears to be the common denominator in a series of distinct neurodegenerative diseases yet its role in the associated neuronal pathology in these various conditions remains elusive. In Parkinson's disease, localization of alpha synuclein aggregates within intracellular Lewy body occlusions represent a major hallmark of this disorder and suggest that such aggregation may play a causative role in the resulting dopaminergic cell loss. In this Viewpoint article, recent data is reviewed related to how alpha synuclein aggregation may occur, what cellular events might be responsible, and how this may interfere with normal cellular function(s). It appears likely that while aggregation of alpha synuclein may interfere with its normal function in the cell, this is not the primary cause of the related neurodegeneration.

A polymorphic variation of serine to tyrosine at codon 18 in the ubiquitin C-terminal hydrolase-L1 gene is associated with a reduced risk of sporadic Parkinson's disease in a Japanese population

Recent studies suggest that ubiquitin C-terminal hydrolase-L1 (UCH-L1), a neuronal deubiquitinating enzyme, represents a candidate gene responsible for either the development of familial Parkinson's disease (PD) or the protection against sporadic PD in Caucasian populations, although these findings are not fully verified in non-Caucasian populations. To determine an association of the variations in the UCH-L1 gene with development of sporadic PD in a Japanese population, a Ser18Tyr polymorphism and an Ile93Met mutation were studied by PCR-RFLP analysis in 74 Japanese patients with sporadic PD and 155 age-matched non-PD controls. The frequency of 18Tyr allele was significantly lower in PD patients than the controls (38.5% vs. 53.5%) (chi(2)=9.064, p=0.0026; the odds ratio=1.84, 95% confident interval=1.23-2.74). Furthermore, the frequency of 18Tyr/Tyr homozygotes was significantly lower in PD patients than the controls (14.9% vs. 33.5%), compared with that of two other genotypes combined (chi(2)=8.767, p=0.0031; the odds ratio=0.35, 95% confident interval=0.27-0.45). The Ile93Met substitution was not detected in any Japanese subjects examined. These results indicate that the presence of 18Tyr allele and 18Tyr/Tyr homozygosity in the UCH-L1 gene is associated with a reduced risk for development of sporadic PD in a Japanese population, supporting the previous observations on sporadic PD in Caucasian populations.

The ubiquitin carboxy-terminal hydrolase-L1 gene S18Y polymorphism does not confer protection against idiopathic Parkinson's disease

The ubiquitin carboxy-terminal hydrolase L1gene (UCH-L1) has been implicated in the aetiology of Parkinson's disease (PD). A rare Ile93Met mutation in UCH-L1 in a German PD sib-pair has been reported. Recently, a S18Y (C54A) polymorphism in exon 3 of UCH-L1 was found to be under-represented in PD patients compared to controls. To test the reproducibility of this negative association, we conducted an allele-association study of the S18Y polymorphism in an Australian case-control sample consisting of 142 PD cases and 142 closely matched control subjects. Genotypes were determined using polymerase chain reaction and RsaI restriction enzyme assay. Analysis revealed no significant difference between PD patients and controls for genotype or allele frequencies of the S18Y polymorphism. The frequency of the S18Y allele in Australian subjects is similar to that reported elsewhere. This study suggests that the S18Y polymorphism in UCH-L1 does not influence the risk for developing PD.

Nuclear magnetic relaxation dispersion profiles of substantia nigra pars compacta in Parkinson's disease patients are consistent with protein aggregation

Nuclear Magnetic Relaxation field-cycling relaxometry is a technique, able to report on water mobility in tissues. By means of this technique, post-mortem specimens from both controls and idiopathic Parkinson's disease patients have been investigated. Results show different relaxometric behavior between the groups, which is consistent with protein aggregation in Parkinson's disease specimens.

Oxidative stress and genetics in the pathogenesis of Parkinson's disease

Parkinson's Disease (PD) is the second most common chronic neurodegenerative disease characterized by the progressive loss of dopamine neurons, leading to rigidity, slowness of movement, rest tremor, gait disturbances, and imbalance. Although there is effective symptomatic treatment for PD, there is no proven preventative or regenerative therapy. The etiology of this disorder remains unknown. Recent genetic studies have identified mutations in alpha-synuclein as a rare cause of autosomal dominant familial PD and mutations in parkin as a cause of autosomal recessive familial PD. The more common sporadic form of PD is thought to be due to oxidative stress and derangements in mitochondrial complex I activity. Understanding the mechanism by which familial linked mutations and oxidative stress cause PD has tremendous potential for unraveling the mechanisms of dopamine cell death in PD. In this article, we review recent advances in the understanding of the role of genetics and oxidative stress in the pathogenesis of PD.

Sluggish auditory processing in dyslexics is not due to persistence in sensory memory

The hypothesis that dyslexics show prolonged audible persistence was tested by an event-related brain response technique and rejected in favour of an attentional explanation.

Deubiquitinating enzymes: their diversity and emerging roles

A growing number of important regulatory proteins within cells are modified by conjugation of ubiquitin, a well-conserved 76-amino-acid polypeptide. The ubiquitinated proteins are targeted to proteasome for degradation or alternative metabolic fates, such as triggering of plasma membrane endocytosis and trafficking to vacuoles or lysosomes. Deubiquitination, reversal of this modification, is being recognized as an important regulatory step. Deubiquitinating enzymes are cysteine proteases that specifically cleave off ubiquitin from ubiquitin-conjugated protein substrates as well as from its precursor proteins. Genome sequencing projects have identified more than 90 deubiquitinating enzymes, making them the largest family of enzymes in the ubiquitin system. This review will concentrate on recent important findings as well as new insights into the diversity and emerging roles of deubiquitinating enzymes in the ubiquitin-dependent pathway.