title: Mechanism of inhibition of human KSP by ispinesib.
abstract: KSP, also known as HsEg5, is a kinesin that plays an essential role in the formation of a bipolar mitotic spindle and is required for cell cycle progression through mitosis. Ispinesib is the first potent, highly specific small-molecule inhibitor of KSP tested for the treatment of human disease. This novel anticancer agent causes mitotic arrest and growth inhibition in several human tumor cell lines and is currently being tested in multiple phase II clinical trials. In this study we have used steady-state and pre-steady-state kinetic assays to define the mechanism of KSP inhibition by ispinesib. Our data show that ispinesib alters the ability of KSP to bind to microtubules and inhibits its movement by preventing the release of ADP without preventing the release of the KSP-ADP complex from the microtubule. This type of inhibition is consistent with the physiological effect of ispinesib on cells, which is to prevent KSP-driven mitotic spindle pole separation. A comparison of ispinesib to monastrol, another small-molecule inhibitor of KSP, reveals that both inhibitors share a common mode of inhibition.
authors.affiliation: Cytokinetics Inc., 280 East Grand Avenue, South San Francisco, California 94080, USA. llad@cytokinetics.com
authors.forename: Latesh
authors.initials: L
authors.lastname: Lad
authors.forename: Lusong
authors.initials: L
authors.lastname: Luo
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Carson
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Wood
authors.forename: James J
authors.initials: JJ
authors.lastname: Hartman
authors.forename: Robert A
authors.initials: RA
authors.lastname: Copeland
authors.forename: Roman
authors.initials: R
authors.lastname: Sakowicz
mesh_terms: D000244:Adenosine Diphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000255:Adenosine Triphosphate / Q000502:physiology; D000494:Allosteric Regulation / Q000235:genetics; D001549:Benzamides / Q000737:chemistry* / Q000378:metabolism; D001667:Binding, Competitive / Q000235:genetics; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D016547:Kinesins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011799:Quinazolines / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001549:Benzamides; D004791:Enzyme Inhibitors; C470243:KIF11 protein, human; D011799:Quinazolines; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C508757:ispinesib; D000251:Adenosine Triphosphatases; D016547:Kinesins