title: alpha-Synuclein protects against oxidative stress via inactivation of the c-Jun N-terminal kinase stress-signaling pathway in neuronal cells.
abstract: The expression of alpha-synuclein, a synaptic molecule implicated in the pathogenesis of neurodegenerative disorders such as Parkinson's disease and Lewy body disease is increased upon injury to the nervous system, indicating that it might play a role in regeneration and plasticity; however, the mechanisms are unclear. Because c-Jun N-terminal kinase (JNK), a member of the mitogen-activated protein kinase family, plays an important role in stress response, the main objective of the present study was to better understand the involvement of this pathway in the signaling responses associated with resistance to injury in cells expressing alpha-synuclein. For this purpose, the JNK-signaling pathway was investigated in alpha-synuclein-transfected neuronal cell line glucose transporter (GT) 1-7 under oxidative stress conditions. Although hydrogen peroxide challenge resulted in JNK activation and cell death in cells transfected with vector control or beta-synuclein, alpha-synuclein-transfected cells were resistant to hydrogen peroxide, and JNK was not activated. The inactivation of JNK in the alpha-synuclein-transfected cells was associated with increased expression and activity of JNK-interacting protein (JIP)-1b/islet-brain (IB)1, the scaffold protein for the JNK pathway. Similarly, cells transfected with JIP-1b/IB1 were resistant to hydrogen peroxide associated with inactivation of the JNK pathway. In these cells, expression of endogenous alpha-synuclein was significantly increased at the protein level. Furthermore, alpha-synuclein was co-localized with JIP-1b/IB1 in the growth cones. Taken together, these results suggest that increased alpha-synuclein expression might protect cells from oxidative stress by inactivation of JNK via increased expression of JIP-1b/IB1. Furthermore, interactions between alpha-synuclein and JIP-1b/IB1 may play a mutual role in the neuronal response to injury and neurodegeneration.
authors.affiliation: Department of Neurosciences, University of California San Diego, School of Medicine, La Jolla, California 92093-0624, USA.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Leigh J
authors.initials: LJ
authors.lastname: Hsu
authors.forename: Edward
authors.initials: E
authors.lastname: Rockenstein
authors.forename: Takato
authors.initials: T
authors.lastname: Takenouchi
authors.forename: Margaret
authors.initials: M
authors.lastname: Mallory
authors.forename: Eliezer
authors.initials: E
authors.lastname: Masliah
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D007150:Immunohistochemistry; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D018384:Oxidative Stress; D015398:Signal Transduction / Q000502:physiology*; D051843:Synucleins; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D051844:alpha-Synuclein; D051846:beta-Synuclein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C490665:Mapk8ip protein, mouse; D009004:Monosaccharide Transport Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C497605:Snca protein, mouse; C497608:Sncb protein, mouse; D051843:Synucleins; D015534:Trans-Activators; D051844:alpha-Synuclein; D051846:beta-Synuclein; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases