title: A sporadic Parkinson disease model via silencing of the ubiquitin-proteasome/E3 ligase component SKP1A.
abstract: The aim of this study was to develop a new model of sporadic Parkinson disease (PD) based on silencing of the SKP1A gene, a component of the ubiquitin-proteasome/E3 ligase complex, Skp1, Cullin 1, F-box protein, which was found to be highly decreased in the substantia nigra of sporadic PD patients. Initially, an embryonic mouse substantia nigra-derived cell line (SN4741 cells) was infected with short hairpin RNA lentiviruses encoding the murine transcript of the SKP1A gene or with scrambled vector. SKP1A silencing resulted in increased susceptibility to neuronal damages induced by the parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium ion and serum starvation, in parallel with a decline in the expression of the dopaminergic markers, dopamine transporter and vesicular monoamine transporter-2. SKP1A-deficient cells presented a delay in completion of the cell cycle and the inability to arrest at the G(0)/G(1) phase when induced to differentiate. Instead, the cells progressed through S phase, developing rounded aggregates with characteristics of aggresomes including immunoreactivity for gamma-tubulin, alpha-synuclein, ubiquitin, tyrosine hydroxylase, Hsc-70 (70-kDa heat shock cognate protein), and proteasome subunit, and culminating in a lethal phenotype. Conversely, stably enforced expression of wild type SKP1A duplicated the survival index of naïve SN4741 cells under proteasomal inhibition injury, suggesting a new structural role of SKP1 in dopaminergic neuronal function, besides its E3 ligase activity. These results link, for the first time, SKP1 to dopamine neuronal function and survival, suggesting an essential role in sporadic PD. In summary, this new model has reproduced to a significant extent the molecular alterations described in sporadic PD at the cellular level, implicating Skp1 as a potential modifier in sporadic PD neurodegeneration.
authors.affiliation: Eve Topf and National Parkinson Foundation Centers for Neurodegenerative Diseases and the Department of Molecular Pharmacology, Faculty of Medicine, Technion, 31096 Haifa, Israel.
authors.forename: Tali
authors.initials: T
authors.lastname: Fishman-Jacob
authors.forename: Lydia
authors.initials: L
authors.lastname: Reznichenko
authors.forename: Moussa B H
authors.initials: MB
authors.lastname: Youdim
authors.forename: Silvia A
authors.initials: SA
authors.lastname: Mandel
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D020868:Gene Silencing; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019636:Neurodegenerative Diseases / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D009498:Neurotoxins / Q000737:chemistry; D010300:Parkinson Disease / Q000235:genetics* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics* / Q000502:physiology; D025801:Ubiquitin / Q000737:chemistry*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D050883:HSC70 Heat-Shock Proteins; D009498:Neurotoxins; D044786:S-Phase Kinase-Associated Proteins; C545448:SKP1A protein, mouse; D025801:Ubiquitin; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex