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See detailTransgenic overexpression of the alpha-synuclein interacting protein synphilin-1 leads to behavioral and neuropathological alterations in mice.
Nuber, Silke; Franck, Thomas; Wolburg, Hartwig et al

in Neurogenetics (2010), 11(1), 107-20

Synphilin-1 has been identified as an interacting protein of alpha-synuclein, Parkin, and LRRK2, proteins which are mutated in familial forms of Parkinson disease (PD). Subsequently, synphilin-1 has also ... [more ▼]

Synphilin-1 has been identified as an interacting protein of alpha-synuclein, Parkin, and LRRK2, proteins which are mutated in familial forms of Parkinson disease (PD). Subsequently, synphilin-1 has also been shown to be an intrinsic component of Lewy bodies in sporadic PD. In order to elucidate the role of synphilin-1 in the pathogenesis of PD, we generated transgenic mice overexpressing wild-type and mutant (R621C) synphilin-1 driven by a mouse prion protein promoter. Transgenic expression of both wild-type and the R621C variant synphilin-1 resulted in increased dopamine levels of the nigrostriatal system in 3-month-old mice. Furthermore, we found pathological ubiquitin-positive inclusions in cerebellar sections and dark-cell degeneration of Purkinje cells. Both transgenic mouse lines showed significant reduction of motor skill learning and motor performance. These findings suggest a pathological role of overexpressed synphilin-1 in vivo and will help to further elucidate the mechanisms of protein aggregation and neuronal cell death. [less ▲]

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See detailMitochondrial protein quality control by the proteasome involves ubiquitination and the protease Omi.
Radke, Susanne; Chander, Harish; Schafer, Patrick et al

in The Journal of biological chemistry (2008), 283(19), 12681-5

We report here that blocking the activity of the 26 S proteasome results in drastic changes in the morphology of the mitochondria and accumulation of intermembrane space (IMS) proteins. Using endonuclease ... [more ▼]

We report here that blocking the activity of the 26 S proteasome results in drastic changes in the morphology of the mitochondria and accumulation of intermembrane space (IMS) proteins. Using endonuclease G (endoG) as a model IMS protein, we found that accumulation of wild-type but to a greater extent mutant endoG leads to changes in the morphology of the mitochondria similar to those observed following proteasomal inhibition. Further, we show that wild-type but to a greater extent mutant endoG is a substrate for ubiquitination, suggesting the presence of a protein quality control. Conversely, we also report that wild-type but not mutant endoG is a substrate for the mitochondrial protease Omi but only upon inhibition of the proteasome. These findings suggest that although elimination of mutant IMS proteins is strictly dependent on ubiquitination, elimination of excess or spontaneously misfolded wild-type IMS proteins is monitored by ubiquitination and as a second checkpoint by Omi cleavage when the proteasome function is deficient. One implication of our finding is that in the context of attenuated proteasomal function, accumulation of IMS proteins would contribute to the collapse of the mitochondrial network such as that observed in neurodegenerative diseases. Another implication is that such collapse could be accelerated either by mutations in IMS proteins or by mutations in Omi itself. [less ▲]

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See detailLoss of function mutations in the gene encoding Omi/HtrA2 in Parkinson's disease.
Strauss, Karsten M.; Martins, Luisa UL; Plun-Favreau, Helene et al

in Human molecular genetics (2005), 14(15), 2099-111

Recently targeted disruption of Omi/HtrA2 has been found to cause neurodegeneration and a parkinsonian phenotype in mice. Using a candidate gene approach, we performed a mutation screening of the Omi ... [more ▼]

Recently targeted disruption of Omi/HtrA2 has been found to cause neurodegeneration and a parkinsonian phenotype in mice. Using a candidate gene approach, we performed a mutation screening of the Omi/HtrA2 gene in German Parkinson's disease (PD) patients. In four patients, we identified a novel heterozygous G399S mutation, which was absent in healthy controls. Moreover, we identified a novel A141S polymorphism that was associated with PD (P<0.05). Both mutations resulted in defective activation of the protease activity of Omi/HtrA2. Immunohistochemistry and functional analysis in stably transfected cells revealed that S399 mutant Omi/HtrA2 and to a lesser extent, the risk allele of the A141S polymorphism induced mitochondrial dysfunction associated with altered mitochondrial morphology. Cells overexpressing S399 mutant Omi/HtrA2 were more susceptible to stress-induced cell death than wild-type. On the basis of functional genomics, our results provide a novel link between mitochondrial dysfunction and neurodegeneration in PD. [less ▲]

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See detailNew developments in diagnosis and treatment of Parkinson's disease--from basic science to clinical applications.
Storch, Alexander; Hofer, Anne; Krüger, Rejko UL et al

in Journal of neurology (2004), 251 Suppl 6

In this review we summarize new developments in early diagnosis, establishing surrogate markers, genetics, neuroprotection and cell replacement in Parkinson's disease. Furthermore, we discuss the major ... [more ▼]

In this review we summarize new developments in early diagnosis, establishing surrogate markers, genetics, neuroprotection and cell replacement in Parkinson's disease. Furthermore, we discuss the major problems in the translation of results from preclinical research into successful clinical trials. [less ▲]

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See detailNovel homozygous p.E64D mutation in DJ1 in early onset Parkinson disease (PARK7).
Hering, Robert; Strauss, Karsten M.; Tao, Xiao et al

in Human mutation (2004), 24(4), 321-9

Mutations in the parkin gene have been identified as a common cause of autosomal recessive inherited Parkinson disease (PD) associated with early disease manifestation. However, based on linkage data ... [more ▼]

Mutations in the parkin gene have been identified as a common cause of autosomal recessive inherited Parkinson disease (PD) associated with early disease manifestation. However, based on linkage data, mutations in other genes contribute to the genetic heterogeneity of early-onset PD (EOPD). Recently, two mutations in the DJ1 gene were described as a second cause of autosomal recessive EOPD (PARK7). Analyzing the PARK7/DJ1 gene in 104 EOPD patients, we identified a third mutation, c.192G>C (p.E64D), associated with EOPD in a patient of Turkish ancestry and characterized the functional significance of this amino acid substitution. In the patient, a substantial reduction of dopamine uptake transporter (DAT) binding was found in the striatum using [(18)F]FP-CIT and PET, indicating a serious loss of presynaptic dopaminergic afferents. His sister, homozygous for E64D, was clinically unaffected but showed reduced dopamine uptake when compared with a clinically unaffected brother, who is heterozygous for E64D. We demonstrate by crystallography that the E64D mutation does not alter the structure of the DJ1 protein, however we observe a tendency towards decreased levels of the mutant protein when overexpressed in HEK293 or COS7 cells. Using immunocytochemistry in contrast to the homogenous nuclear and cytoplasmic staining in HEK293 cells overexpressing wild-type DJ1, about 5% of the cells expressing E64D and up to 80% of the cells expressing the recently described L166P mutation displayed a predominant nuclear localization of the mutant DJ1 protein. [less ▲]

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See detailIdentification and functional characterization of a novel R621C mutation in the synphilin-1 gene in Parkinson's disease.
Marx, Frank P.; Holzmann, Carsten; Strauss, Karsten M. et al

in Human molecular genetics (2003), 12(11), 1223-31

Synphilin-1 is linked to the pathogenesis of Parkinson's disease (PD) based on its identification as an alpha-synuclein (PARK1) and parkin (PARK2) interacting protein. Moreover, synphilin-1 is a component ... [more ▼]

Synphilin-1 is linked to the pathogenesis of Parkinson's disease (PD) based on its identification as an alpha-synuclein (PARK1) and parkin (PARK2) interacting protein. Moreover, synphilin-1 is a component of Lewy bodies (LB) in brains of sporadic PD patients. Therefore, we performed a detailed mutation analysis of the synphilin-1 gene in 328 German familial and sporadic PD patients. In two apparently sporadic PD patients we deciphered a novel C to T transition in position 1861 of the coding sequence leading to an amino acid substitution from arginine to cysteine in position 621 (R621C). This mutation was absent in a total of 702 chromosomes of healthy German controls. To define a possible role of mutant synphilin-1 in the pathogenesis of PD we performed functional analyses in SH-SY5Y cells. We found synphilin-1 capable of producing cytoplasmic inclusions in transfected cells. Moreover we observed a significantly reduced number of inclusions in cells expressing C621 synphilin-1 compared with cells expressing wild-type (wt) synphilin-1, when subjected to proteasomal inhibition. C621 synphilin-1 transfected cells were more susceptible to staurosporine-induced cell death than cells expressing wt synphilin-1. Our findings argue in favour of a causative role of the R621C mutation in the synphilin-1 gene in PD and suggest that the formation of intracellular inclusions may be beneficial to cells and that a mutation in synphilin-1 that reduces this ability may sensitize neurons to cellular stress. [less ▲]

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See detailTherapeutic strategies for Parkinson's disease based on data derived from genetic research.
Riess, Olaf; Berg, Daniela; Krüger, Rejko UL et al

in Journal of neurology (2003), 250 Suppl 1

Following the identification of mutations in alpha-synuclein as the cause of some rare forms of familial Parkinson's disease (PD), genetic research has uncovered numerous gene loci of PD. Meanwhile ... [more ▼]

Following the identification of mutations in alpha-synuclein as the cause of some rare forms of familial Parkinson's disease (PD), genetic research has uncovered numerous gene loci of PD. Meanwhile, several neurodegenerative diseases have been shown to accumulate a-synuclein in neuronal and glial cells summarizing this group of diseases as synucleinopathies. All currently known gene defects causing PD alter the ubiquitin-proteasomal pathway of protein degradation. Identification of these disease mutations allows studying the functional consequences which lead to cellular dysfunction and cell death in cell culture and transgenic animal models, to identify therapeutic targets and to test potential protective strategies in these models. [less ▲]

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See detailSpectrum of phenotypes and genotypes in Parkinson's disease.
Riess, Olaf; Krüger, Rejko UL; Schulz, Jorg B.

in Journal of neurology (2002), 249 Suppl 3

The pathogenesis of Parkinsons disease (PD) is currently unknown. Environmental and genetic factors might contribute to the neurodegenerative process. Genetic mapping approaches in rare familial cases ... [more ▼]

The pathogenesis of Parkinsons disease (PD) is currently unknown. Environmental and genetic factors might contribute to the neurodegenerative process. Genetic mapping approaches in rare familial cases with autosomal recessive and autosomal dominant inheritance of PD suggest wide genetic heterogeneity of the disease. These gene loci in turn allow now a more specific clinical investigation of affected families to study the clinical heterogeneity of PD. The recent identification of mutations in three genes involved in protein degradation and aggregation in familial PD does now facilitate the deciphering of other genes involved in the pathogenesis of the disease. [less ▲]

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See detailParkinson's disease: one biochemical pathway to fit all genes?
Krüger, Rejko UL; Eberhardt, Olaf; Riess, Olaf et al

in Trends in molecular medicine (2002), 8(5), 236-40

Although originally discounted, hereditary factors have emerged as the focus of research in Parkinson's disease (PD). Genetic studies have identified mutations in alpha-synuclein and ubiquitin C-terminal ... [more ▼]

Although originally discounted, hereditary factors have emerged as the focus of research in Parkinson's disease (PD). Genetic studies have identified mutations in alpha-synuclein and ubiquitin C-terminal hydrolase as rare causes of autosomal dominant PD and mutations in parkin as a cause of autosomal recessive PD. Functional characterization of the identified disease genes implicates the ubiquitin-mediated protein degradation pathway in these hereditary forms of PD and also in the more common sporadic forms of PD. Subsequent identification of further loci in familial PD and diverse genetic factors modulating the risk for sporadic PD point to substantial genetic heterogeneity in the disease. Thus, new candidate genes are expected to encode proteins either involved in ubiquitin-mediated protein degradation or sequestrated in intracytoplasmic protein aggregations. Future identification of disease genes is required to confirm this hypothesis, thereby unifying the clinical and genetic heterogeneity of PD, including the common sporadic form of the disease, by one biochemical pathway. [less ▲]

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