Mechanism of inhibition of human KSP by ispinesib.
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.
Lad
Latesh
L
Cytokinetics Inc., 280 East Grand Avenue, South San Francisco, California 94080, USA. llad@cytokinetics.com
Luo
Lusong
L
Carson
Jeffrey D
JD
Wood
Kenneth W
KW
Hartman
James J
JJ
Copeland
Robert A
RA
Sakowicz
Roman
R
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
D001549:Benzamides; D004791:Enzyme Inhibitors; C470243:KIF11 protein, human; D011799:Quinazolines; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C508757:ispinesib; D000251:Adenosine Triphosphatases; D016547:Kinesins