title: Identification of novel spartin-interactors shows spartin is a multifunctional protein.
abstract: Hereditary spastic paraplegia describes a group of neurodegenerative diseases characterized by lower limb progressive weakness and spasticity. Troyer syndrome is an autosomal recessive form of hereditary spastic paraplegia caused by a frameshift mutation (1110delA) in the SPG20 gene encoding spartin protein, the cellular function of which remains unknown. Knowledge about spartin-interactors is also very limited. In this study, we apply a broad spectrum of proteomics techniques to identify novel spartin-binding proteins. We used a Tandem Affinity Purification technique followed by HPLC-mass spectrometry to characterize potential spartin-binding partners. Selected putative interactions were confirmed by co-immunoprecipitation experiments. We identified 94 potential spartin-binding proteins which were grouped into functional categories. We performed co-immunoprecipitation experiments to confirm that spartin interacts with GRP78, GRP75 and nucleolin proteins. Additionally, our mass spectrometry results confirmed previously published information about spartin interaction with ubiquitin and the E3 ubiquitin-protein ligases, AIP4/Itch and AIP5/WWP1. Our studies suggest that spartin is a multifunctional protein and for the first time we suggest a role for spartin in protein folding and turnover both in mitochondria and endoplasmic reticulum. We also show for the first time interaction between spartin and a nucleolar protein, nucleolin.
authors.affiliation: School of Medicine and Medical Science, Conway Institute, University College Dublin, Ireland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Milewska
authors.forename: James
authors.initials: J
authors.lastname: McRedmond
authors.forename: Paula Catherine
authors.initials: PC
authors.lastname: Byrne
mesh_terms: D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed / Q000378:metabolism / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017510:Protein Folding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics; D016601:RNA-Binding Proteins / Q000378:metabolism; D014162:Transfection / Q000379:methods; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000097796:Nucleolin
chemical_list: D018797:Cell Cycle Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D011506:Proteins; D016601:RNA-Binding Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D000097796:Nucleolin; C000717247:HSPA5 protein, human; C464787:SPART protein, human; C018551:glucose-regulated proteins; C107762:tapasin