title: Huntingtin protein interactions altered by polyglutamine expansion as determined by quantitative proteomic analysis.
abstract: Huntington disease (HD) is a neurodegenerative disorder caused by an expansion of a polyglutamine repeat within the HD gene product, huntingtin. Huntingtin, a large (347 kDa) protein containing multiple HEAT repeats, acts as a scaffold for protein-protein interactions. Huntingtin-induced toxicity is believed to be mediated by a conformational change in expanded huntingtin, leading to protein misfolding and aggregation, aberrant protein interactions and neuronal cell death. While many non-systematic studies of huntingtin interactions have been reported, they were not designed to identify and quantify the changes in the huntingtin interactome induced by polyglutamine expansion. We used tandem affinity purification and quantitative proteomics to compare and quantify interactions of normal or expanded huntingtin isolated from a striatal cell line. We found that proteins preferentially interacting with expanded huntingtin are enriched for intrinsically disordered proteins, consistent with previously suggested roles of such proteins in neurodegenerative disorders. Our functional analysis indicates that proteins related to energy production, protein trafficking, RNA post-transcriptional modifications and cell death were significantly enriched among preferential interactors of expanded huntingtin. Expanded huntingtin interacted with many mitochondrial proteins, including AIFM1, consistent with a role for mitochondrial dysfunction in HD. Furthermore, expanded huntingtin interacted with the stress granule-associated proteins Caprin-1 and G3BP and redistributed to RNA stress granules under ER-stress conditions. These data demonstrate that a number of key cellular functions and networks may be disrupted by abnormal interactions of expanded huntingtin and highlight proteins and pathways that may be involved in HD cellular pathogenesis and that may serve as therapeutic targets.
authors.affiliation: Division of Neurobiology, Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD, USA. tratovi1@jhmi.edu
authors.forename: Tamara
authors.initials: T
authors.lastname: Ratovitski
authors.forename: Ekaterine
authors.initials: E
authors.lastname: Chighladze
authors.forename: Nicolas
authors.initials: N
authors.lastname: Arbez
authors.forename: Tatiana
authors.initials: T
authors.lastname: Boronina
authors.forename: Shelley
authors.initials: S
authors.lastname: Herbrich
authors.forename: Robert N
authors.initials: RN
authors.lastname: Cole
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Ross
mesh_terms: D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D004265:DNA Helicases; D057809:HEK293 Cells; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D000075223:Poly-ADP-Ribose Binding Proteins; D011485:Protein Binding; D040901:Proteomics; D012313:RNA / Q000378:metabolism; D020365:RNA Helicases; D000067776:RNA Recognition Motif Proteins
chemical_list: C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; C486562:CAPRIN1 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D010455:Peptides; D000075223:Poly-ADP-Ribose Binding Proteins; D000067776:RNA Recognition Motif Proteins; C097188:polyglutamine; D012313:RNA; D004265:DNA Helicases; C116070:G3BP1 protein, human; D020365:RNA Helicases