title: Misfolded polyglutamine, polyalanine, and superoxide dismutase 1 aggregate via distinct pathways in the cell.
abstract: Protein aggregation into intracellular inclusions is a key feature of many neurodegenerative disorders. A common theme has emerged that inappropriate self-aggregation of misfolded or mutant polypeptide sequences is detrimental to cell health. Yet protein quality control mechanisms may also deliberately cluster them together into distinct inclusion subtypes, including the insoluble protein deposit (IPOD) and the juxtanuclear quality control (JUNQ). Here we investigated how the intrinsic oligomeric state of three model systems of disease-relevant mutant protein and peptide sequences relates to the IPOD and JUNQ patterns of aggregation using sedimentation velocity analysis. Two of the models (polyalanine (37A) and superoxide dismutase 1 (SOD1) mutants A4V and G85R) accumulated into the same JUNQ-like inclusion whereas the other, polyglutamine (72Q), formed spatially distinct IPOD-like inclusions. Using flow cytometry pulse shape analysis (PulSA) to separate cells with inclusions from those without revealed the SOD1 mutants and 37A to have abruptly altered oligomeric states with respect to the nonaggregating forms, regardless of whether cells had inclusions or not, whereas 72Q was almost exclusively monomeric until inclusions formed. We propose that mutations leading to JUNQ inclusions induce a constitutively "misfolded" state exposing hydrophobic side chains that attract and ultimately overextend protein quality capacity, which leads to aggregation into JUNQ inclusions. Poly(Q) is not misfolded in this same sense due to universal polar side chains, but is highly prone to forming amyloid fibrils that we propose invoke a different engagement mechanism with quality control.
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Saskia
authors.initials: S
authors.lastname: Polling
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Yee-Foong
authors.initials: YF
authors.lastname: Mok
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Yasmin M
authors.initials: YM
authors.lastname: Ramdzan
authors.affiliation: Florey Institute of Neuroscience and Mental Health and Centre for Neuroscience, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Turner
authors.affiliation: School of Biological Sciences, Faculty of Science and Illawarra Health and Medical Institute, University of Wollongong, Wollongong, New South Wales 2522, Australia.
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Yerbury
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Hill
authors.affiliation: Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia. Electronic address: dhatters@unimelb.edu.au.
authors.forename: Danny M
authors.initials: DM
authors.lastname: Hatters
mesh_terms: D000682:Amyloid / Q000737:chemistry; D006801:Humans; D002479:Inclusion Bodies / Q000737:chemistry; D009154:Mutation; D019636:Neurodegenerative Diseases / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics; D000072105:Superoxide Dismutase-1
chemical_list: D000682:Amyloid; D010455:Peptides; C000606290:SOD1 protein, human; C019529:polyalanine; C097188:polyglutamine; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: Amyotrophic Lateral Sclerosis (Lou Gehrig's Disease); Analytical Ultracentrifugation; Flow Cytometry; Inclusion; Polyalanine; Polyglutamine; Protein Aggregation; Superoxide Dismutase (SOD)