Distinct roles of septins in cytokinesis: SEPT9 mediates midbody abscission.
Septins are a family of GTP-binding proteins implicated in mammalian cell division. Most studies examining the role of septins in this process have treated the family as a whole, thus neglecting the possibility that individual members may have diverse functions. To address this, we individually depleted each septin family member expressed in HeLa cells by siRNA and assayed for defects in cell division by immunofluorescence and time-lapse microscopy. Depletion of SEPT2, SEPT7, and SEPT11 causes defects in the early stages of cytokinesis, ultimately resulting in binucleation. In sharp contrast, SEPT9 is dispensable for the early stages of cell division, but is critical for the final separation of daughter cells. Rescue experiments indicate that SEPT9 isoforms containing the N-terminal region are sufficient to drive cytokinesis. We demonstrate that SEPT9 mediates the localization of the vesicle-tethering exocyst complex to the midbody, providing mechanistic insight into the role of SEPT9 during abscission.
Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Mathew P
MP
Estey
Caterina
C
Di Ciano-Oliveira
Carol D
CD
Froese
Margaret T
MT
Bejide
William S
WS
Trimble
D002460:Cell Line; D048749:Cytokinesis / Q000502:physiology*; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D058112:Septins / Q000235:genetics / Q000378:metabolism*; D059008:Time-Lapse Imaging
D020033:Protein Isoforms; D034741:RNA, Small Interfering; C474315:SEPTIN9 protein, human; D058112:Septins