title: SPG20 protein spartin is recruited to midbodies by ESCRT-III protein Ist1 and participates in cytokinesis.
abstract: Hereditary spastic paraplegias (HSPs, SPG1-46) are inherited neurological disorders characterized by lower extremity spastic weakness. Loss-of-function SPG20 gene mutations cause an autosomal recessive HSP known as Troyer syndrome. The SPG20 protein spartin localizes to lipid droplets and endosomes, and it interacts with tail interacting protein 47 (TIP47) as well as the ubiquitin E3 ligases atrophin-1-interacting protein (AIP)4 and AIP5. Spartin harbors a domain contained within microtubule-interacting and trafficking molecules (MIT) at its N-terminus, and most proteins with MIT domains interact with specific ESCRT-III proteins. Using yeast two-hybrid and in vitro surface plasmon resonance assays, we demonstrate that the spartin MIT domain binds with micromolar affinity to the endosomal sorting complex required for transport (ESCRT)-III protein increased sodium tolerance (Ist)1 but not to ESCRT-III proteins charged multivesicular body proteins 1-7. Spartin colocalizes with Ist1 at the midbody, and depletion of Ist1 in cells by small interfering RNA significantly decreases the number of cells where spartin is present at midbodies. Depletion of spartin does not affect Ist1 localization to midbodies but markedly impairs cytokinesis. A structure-based amino acid substitution in the spartin MIT domain (F24D) blocks the spartin-Ist1 interaction. Spartin F24D does not localize to the midbody and acts in a dominant-negative manner to impair cytokinesis. These data suggest that Ist1 interaction is important for spartin recruitment to the midbody and that spartin participates in cytokinesis.
authors: Cellular Neurology Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke and Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Benoît
authors: B
authors: Renvoisé
authors: Rell L
authors: RL
authors: Parker
authors: Dong
authors: D
authors: Yang
authors: Joanna C
authors: JC
authors: Bakowska
authors: James H
authors: JH
authors: Hurley
authors: Craig
authors: C
authors: Blackstone
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D018385:Centrosome / Q000378:metabolism; D048749:Cytokinesis; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D005799:Genes, Dominant / Q000235:genetics; D006801:Humans; D008938:Mitosis; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D015513:Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C533705:IST1 protein, human; D050505:Mutant Proteins; D015513:Oncogene Proteins; D011506:Proteins; C464787:SPART protein, human