title: Aurora B inhibits MCAK activity through a phosphoconformational switch that reduces microtubule association.
abstract: BACKGROUND
  Proper spindle assembly and chromosome segregation rely on precise microtubule dynamics, which are governed in part by the kinesin-13 MCAK. MCAK microtubule depolymerization activity is inhibited by Aurora B-dependent phosphorylation, but the mechanism of this inhibition is not understood.
  
  
  RESULTS
  Here, we develop the first Förster resonance energy transfer (FRET)-based biosensor for MCAK and show that MCAK in solution exists in a closed conformation mediated by an interaction between the C-terminal domain (CT) and the neck. Using fluorescence lifetime imaging (FLIM) we show that MCAK bound to microtubule ends is closed relative to MCAK associated with the microtubule lattice. Aurora B phosphorylation at S196 in the neck opens MCAK conformation and diminishes the interaction between the CT and the neck. Using FLIM and TIRF imaging, we find that changes in MCAK conformation are associated with a decrease in MCAK affinity for the microtubule.
  
  
  CONCLUSIONS
  Unlike motile kinesins, which are open when doing work, the high-affinity binding state for microtubule-depolymerizing kinesins is in a closed conformation. Phosphorylation switches MCAK conformation, which inhibits its ability to interact with microtubules and reduces its microtubule depolymerization activity. This work shows that the conformational model proposed for regulating kinesin activity is not universal and that microtubule-depolymerizing kinesins utilize a distinct conformational mode to regulate affinity for the microtubule, thus controlling their catalytic efficiency. Furthermore, our work provides a mechanism by which the robust microtubule depolymerization activity of kinesin-13s can be rapidly modulated to control cellular microtubule dynamics.
authors.affiliation: Medical Sciences, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Stephanie C
authors.initials: SC
authors.lastname: Ems-McClung
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Hainline
authors.affiliation: Department of Cellular and Molecular Biochemistry, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Jenna
authors.initials: J
authors.lastname: Devare
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Hailing
authors.initials: H
authors.lastname: Zong
authors.affiliation: Department of Cellular and Molecular Biochemistry, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Shang
authors.initials: S
authors.lastname: Cai
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Carnes
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Sidney L
authors.initials: SL
authors.lastname: Shaw
authors.affiliation: Medical Sciences, Indiana University, Bloomington, IN 47405, USA. Electronic address: cwalczak@indiana.edu.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Walczak
mesh_terms: D000818:Animals; D064107:Aurora Kinase B / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015374:Biosensing Techniques; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D016547:Kinesins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D064107:Aurora Kinase B; D016547:Kinesins