title: Heat shock prevents alpha-synuclein-induced apoptosis in a yeast model of Parkinson's disease.
abstract: We show that human wild-type alpha synuclein (WT alpha-syn), and the inherited mutants A53T or A30P, when expressed in the yeast Saccharomyces cerevisiae triggers events that are diagnostic of apoptosis: loss of membrane asymmetry due to the externalization of phosphatidylserine, accumulation of reactive oxygen species (ROS), and the release of cytochrome c from mitochondria. A brief heat shock was strikingly protective in that alpha-syn-expressing cells receiving a heat shock exhibited none of these apoptotic markers. Because the heat shock did not decrease the expression level of alpha-syn, a protective protein or proteins, induced by the heat shock, must be responsible for inhibition of alpha-syn-induced apoptosis. Using ROS accumulation as a marker of apoptosis, the role of various genes and various drugs in controlling alpha-syn-induced apoptosis was investigated. Treatment with geldanamycin or glutathione, overexpression of Ssa3 (Hsp70), or deletion of the yeast metacaspase gene YCA1 abolishes the ability of alpha-syn to induce ROS accumulation. Deletion of YCA1 also promotes vigorous growth of alpha-syn-expressing cells compared to cells that contain a functional copy of YCA1. These findings indicate that alpha-syn-induced ROS generation is mediated by the caspase, according to alpha-syn-->caspase-->ROS-->apoptosis. It is shown by co-immunoprecipitation that Ssa3 binds to alpha-syn in a nucleotide-dependent manner. Thus, we propose that Hsp70 chaperones inhibit this sequence of events by binding and sequestering alpha-syn.
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA.
authors.forename: Todd R
authors.initials: TR
authors.lastname: Flower
authors.forename: Liudmila S
authors.initials: LS
authors.lastname: Chesnokova
authors.forename: Clifford A
authors.initials: CA
authors.lastname: Froelich
authors.forename: Cheryl
authors.initials: C
authors.lastname: Dixon
authors.forename: Stephan N
authors.initials: SN
authors.lastname: Witt
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000737:chemistry; D017209:Apoptosis; D016227:Benzoquinones; D015153:Blotting, Western; D020169:Caspases / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D005434:Flow Cytometry; D017353:Gene Deletion; D005838:Genotype; D005978:Glutathione / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D047029:Lactams, Macrocyclic; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010300:Parkinson Disease / Q000378:metabolism* / Q000473:pathology*; D010957:Plasmids / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D017382:Reactive Oxygen Species; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D051843:Synucleins; D013997:Time Factors; D051844:alpha-Synuclein
chemical_list: D017304:Annexin A5; D016227:Benzoquinones; D015853:Cysteine Proteinase Inhibitors; D018840:HSP70 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D009419:Nerve Tissue Proteins; D011809:Quinones; D017382:Reactive Oxygen Species; C497604:SNCA protein, human; C090869:SSA3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D051843:Synucleins; D051844:alpha-Synuclein; D049452:Green Fluorescent Proteins; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D020169:Caspases; C456272:MCA1 protein, S cerevisiae; D005978:Glutathione; C001277:geldanamycin