title: Centralspindlin links the mitotic spindle to the plasma membrane during cytokinesis.
abstract: At the end of cell division, cytokinesis splits the cytoplasm of nascent daughter cells and partitions segregated sister genomes. To coordinate cell division with chromosome segregation, the mitotic spindle controls cytokinetic events at the cell envelope. The spindle midzone stimulates the actomyosin-driven contraction of the cleavage furrow, which proceeds until the formation of a microtubule-rich intercellular bridge with the midbody at its centre. The midbody directs the final membrane abscission reaction and has been proposed to attach the cleavage furrow to the intercellular bridge. How the mitotic spindle is connected to the plasma membrane during cytokinesis is not understood. Here we identify a plasma membrane tethering activity in the centralspindlin protein complex, a conserved component of the spindle midzone and midbody. We demonstrate that the C1 domain of the centralspindlin subunit MgcRacGAP associates with the plasma membrane by interacting with polyanionic phosphoinositide lipids. Using X-ray crystallography we determine the structure of this atypical C1 domain. Mutations in the hydrophobic cap and in basic residues of the C1 domain of MgcRacGAP prevent association of the protein with the plasma membrane, and abrogate cytokinesis in human and chicken cells. Artificial membrane tethering of centralspindlin restores cell division in the absence of the C1 domain of MgcRacGAP. Although C1 domain function is dispensable for the formation of the midzone and midbody, it promotes contractility and is required for the attachment of the plasma membrane to the midbody, a long-postulated function of this organelle. Our analysis suggests that centralspindlin links the mitotic spindle to the plasma membrane to secure the final cut during cytokinesis in animal cells.
authors.affiliation: Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, Blanche Lane, South Mimms, Hertfordshire EN6 3LD, UK.
authors.forename: Sergey
authors.initials: S
authors.lastname: Lekomtsev
authors.forename: Kuan-Chung
authors.initials: KC
authors.lastname: Su
authors.forename: Valerie E
authors.initials: VE
authors.lastname: Pye
authors.forename: Ken
authors.initials: K
authors.lastname: Blight
authors.forename: Sriramkumar
authors.initials: S
authors.lastname: Sundaramoorthy
authors.forename: Tohru
authors.initials: T
authors.lastname: Takaki
authors.forename: Lucy M
authors.initials: LM
authors.lastname: Collinson
authors.forename: Peter
authors.initials: P
authors.lastname: Cherepanov
authors.forename: Nullin
authors.initials: N
authors.lastname: Divecha
authors.forename: Mark
authors.initials: M
authors.lastname: Petronczki
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D048749:Cytokinesis / Q000235:genetics / Q000528:radiation effects*; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D051571:Protein Kinase C-alpha / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D008941:Spindle Apparatus / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C554292:12-O-tetradecanoylphorbol-1,3-acetate; D020690:GTPase-Activating Proteins; D008869:Microtubule-Associated Proteins; C115995:mgcRacGAP; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate