title: Adaptive changes in autophagy after UPS impairment in Parkinson's disease.
abstract: OBJECTIVE
  Ubiquitin-proteasome system (UPS) and autophagosome-lysosome pathway (ALP) are the most important machineries responsible for protein degradation in Parkinson's disease (PD). The aim of this study is to investigate the adaptive alterations in autophagy upon proteasome inhibition in dopaminergic neurons in vitro and in vivo.
  
  
  METHODS
  Human dopaminergic neuroblastoma SH-SY5Y cells were treated with the proteasome inhibitor lactacystin (5 μmol/L) for 5, 12, or 24 h. The expression of autophagy-related proteins in the cells was detected with immunoblotting. UPS-impaired mouse model of PD was established by microinjection of lactacystin (2 μg) into the left hemisphere of C57BL/6 mice that were sacrificed 2 or 4 weeks later. The midbrain tissues were dissected to assess alterations in autophagy using immunofluorescence, immunoblotting and electron microscopy assays.
  
  
  RESULTS
  Both in SH-SY5Y cells and in the midbrain of UPS-impaired mouse model of PD, treatment with lactacystin significantly increased the expression levels of LC3-I/II and Beclin 1, and reduced the levels of p-mTOR, mTOR and p62/SQSTM1. Furthermore, lactacystin treatment in UPS-impaired mouse model of PD caused significant loss of TH-positive neurons in the substantia nigra, and dramatically increased the number of autophagosomes in the left TH-positive neurons.
  
  
  CONCLUSIONS
  Inhibition of UPS by lactacystin in dopaminergic neurons activates another protein degradation system, the ALP, which includes both the mTOR signaling pathway and Beclin 1-associated pathway.
authors.affiliation: Institute of Neurology, Ruijin Hospital, Jiao Tong University School of Medicine, Shanghai 200025, China.
authors.forename: Yu-fei
authors.initials: YF
authors.lastname: Shen
authors.forename: Yu
authors.initials: Y
authors.lastname: Tang
authors.forename: Xiao-jie
authors.initials: XJ
authors.lastname: Zhang
authors.forename: Kai-xing
authors.initials: KX
authors.lastname: Huang
authors.forename: Wei-dong
authors.initials: WD
authors.lastname: Le
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071186:Beclin-1; D045744:Cell Line, Tumor; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D008565:Membrane Proteins; D061988:Proteasome Inhibitors; D025801:Ubiquitin; C067713:lactacystin; D058570:TOR Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine