title: A Golgi-localized pool of the mitotic checkpoint component Mad1 controls integrin secretion and cell migration.
abstract: Mitotic arrest deficient 1 (Mad1) plays a well-characterized role in the major cell-cycle checkpoint that regulates chromosome segregation during mitosis, the mitotic checkpoint (also known as the spindle assembly checkpoint). During mitosis, Mad1 recruits Mad2 to unattached kinetochores, where Mad2 is converted into an inhibitor of the anaphase-promoting complex/cyclosome bound to its specificity factor, Cdc20. During interphase, Mad1 remains tightly bound to Mad2, and both proteins localize to the nucleus and nuclear pores, where they interact with Tpr (translocated promoter region). Recently, it has been shown that interaction with Tpr stabilizes both proteins and that Mad1 binding to Tpr permits Mad2 to associate with Cdc20. However, interphase functions of Mad1 that do not directly affect the mitotic checkpoint have remained largely undefined. Here we identify a previously unrecognized interphase distribution of Mad1 at the Golgi apparatus. Mad1 colocalizes with multiple Golgi markers and cosediments with Golgi membranes. Although Mad1 has previously been thought to constitutively bind Mad2, Golgi-associated Mad1 is Mad2 independent. Depletion of Mad1 impairs secretion of α5 integrin and results in defects in cellular attachment, adhesion, and FAK activation. Additionally, reduction of Mad1 impedes cell motility, while its overexpression accelerates directed cell migration. These results reveal an unexpected role for a mitotic checkpoint protein in secretion, adhesion, and motility. More generally, they demonstrate that, in addition to generating aneuploidy, manipulation of mitotic checkpoint genes can have unexpected interphase effects that influence tumor phenotypes.
authors.affiliation: Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA; Physiology Training Program, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Wan
authors.affiliation: Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Fen
authors.initials: F
authors.lastname: Zhu
authors.affiliation: Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA; Molecular and Cellular Pharmacology Training Program, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Zasadil
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Jiaquan
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Johnson
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Erwin
authors.initials: E
authors.lastname: Berthier
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53705, USA; Carbone Cancer Center, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beebe
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53705, USA; Carbone Cancer Center, University of Wisconsin, Madison, WI 53705, USA.
authors.forename: Anjon
authors.initials: A
authors.lastname: Audhya
authors.affiliation: Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA; Carbone Cancer Center, University of Wisconsin, Madison, WI 53705, USA. Electronic address: baweaver@wisc.edu.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Weaver
mesh_terms: D059447:Cell Cycle Checkpoints; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D002465:Cell Movement / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D064246:Mad2 Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D018797:Cell Cycle Proteins; D016023:Integrins; C501384:MAD1L1 protein, human; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D009687:Nuclear Proteins