Eg5 Inhibitors Have Contrasting Effects on Microtubule Stability and Metaphase Spindle Integrity

Geng Yuan Chen, You Jung Kang, A. Sophia Gayek, Wiphu Youyen, Erkan Tüzel, Ryoma Ohi, William O. Hancock

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


To uncover their contrasting mechanisms, antimitotic drugs that inhibit Eg5 (kinesin-5) were analyzed in mixed-motor gliding assays of kinesin-1 and Eg5 motors in which Eg5 "braking" dominates motility. Loop-5 inhibitors (monastrol, STLC, ispinesib, and filanesib) increased gliding speeds, consistent with inducing a weak-binding state in Eg5, whereas BRD9876 slowed gliding, consistent with locking Eg5 in a rigor state. Biochemical and single-molecule assays demonstrated that BRD9876 acts as an ATP- and ADP-competitive inhibitor with 4 nM KI. Consistent with its microtubule polymerase activity, Eg5 was shown to stabilize microtubules against depolymerization. This stabilization activity was eliminated in monastrol but was enhanced by BRD9876. Finally, in metaphase-arrested RPE-1 cells, STLC promoted spindle collapse, whereas BRD9876 did not. Thus, different Eg5 inhibitors impact spindle assembly and architecture through contrasting mechanisms, and rigor inhibitors may paradoxically have the capacity to stabilize microtubule arrays in cells.

Original languageEnglish (US)
Pages (from-to)1038-1046
Number of pages9
JournalACS chemical biology
Issue number4
StatePublished - Apr 21 2017

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Medicine


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