title: The co-chaperone carboxyl terminus of Hsp70-interacting protein (CHIP) mediates alpha-synuclein degradation decisions between proteasomal and lysosomal pathways.
abstract: Alpha-synuclein is a major component of Lewy bodies, the pathological hallmark of Parkinson disease, dementia with Lewy bodies, and related disorders. Misfolding and aggregation of alpha-synuclein is thought to be a critical cofactor in the pathogenesis of certain neurodegenerative diseases. In the current study, we investigate the role of the carboxyl terminus of Hsp70-interacting protein (CHIP) in alpha-synuclein aggregation. We demonstrate that CHIP is a component of Lewy bodies in the human brain, where it colocalizes with alpha-synuclein and Hsp70. In a cell culture model, endogenous CHIP colocalizes with alpha-synuclein and Hsp70 in intracellular inclusions, and overexpression of CHIP inhibits alpha-synuclein inclusion formation and reduces alpha-synuclein protein levels. We demonstrate that CHIP can mediate alpha-synuclein degradation by two discrete mechanisms that can be dissected using deletion mutants; the tetratricopeptide repeat domain is critical for proteasomal degradation, whereas the U-box domain is sufficient to direct alpha-synuclein toward the lysosomal degradation pathway. Furthermore, alpha-synuclein, synphilin-1, and Hsp70 all coimmunoprecipitate with CHIP, raising the possibility of a direct alpha-synuclein-CHIP interaction. The fact that the tetratricopeptide repeat domain is required for the effects of CHIP on alpha-synuclein inclusion morphology, number of inclusions, and proteasomal degradation as well as the direct interaction of CHIP with Hsp70 implicates a cooperation of CHIP and Hsp70 in these processes. Taken together, these data suggest that CHIP acts a molecular switch between proteasomal and lysosomal degradation pathways.
authors.affiliation: Alzheimer Disease Research Unit, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
authors.forename: Youngah
authors.initials: Y
authors.lastname: Shin
authors.forename: Jochen
authors.initials: J
authors.lastname: Klucken
authors.forename: Cam
authors.initials: C
authors.lastname: Patterson
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Hyman
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: McLean
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D006868:Hydrolysis; D016631:Lewy Bodies / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051843:Synucleins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism / Q000502:physiology*; D051844:alpha-Synuclein
chemical_list: D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex