4b6d
Structure of the atypical C1 domain of MgcRacGAPStructure of the atypical C1 domain of MgcRacGAP
Structural highlights
FunctionRGAP1_HUMAN Component of the centralspindlin complex that serves as a microtubule-dependent and Rho-mediated signaling required for the myosin contractile ring formation during the cell cycle cytokinesis. Plays key roles in controlling cell growth and differentiation of hematopoietic cells through mechanisms other than regulating Rac GTPase activity. Also involved in the regulation of growth-related processes in adipocytes and myoblasts. May be involved in regulating spermatogenesis and in the RACGAP1 pathway in neuronal proliferation. Shows strong GAP (GTPase activation) activity towards CDC42 and RAC1 and less towards RHOA. Essential for the early stages of embryogenesis. May play a role in regulating cortical activity through RHOA during cytokinesis. May participate in the regulation of sulfate transport in male germ cells.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] Publication Abstract from PubMedAt 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. Centralspindlin links the mitotic spindle to the plasma membrane during cytokinesis.,Lekomtsev S, Su KC, Pye VE, Blight K, Sundaramoorthy S, Takaki T, Collinson LM, Cherepanov P, Divecha N, Petronczki M Nature. 2012 Dec 13;492(7428):276-9. doi: 10.1038/nature11773. PMID:23235882[13] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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