Up-regulation of cdc2 protein during paclitaxel-induced apoptosis.
Microtubule damages induced by paclitaxel inhibit proteasome-dependent degradation of cyclin B, resulting in a sustained activation of cyclin B/cdc2 kinase and a cell cycle arrest in mitosis. It has been previously shown that this kinase activity is also required for paclitaxel-induced apoptosis. We found here that paclitaxel increased cdc2 mRNA and protein levels and led to an accumulation of cdc2 in the active dephosphorylated form in NIH-OVCAR-3 cells. The addition of cycloheximide inhibited the paclitaxel-induced increase in cdc2 protein level, further indicating that paclitaxel stimulates cdc2 synthesis. This increase in cdc2 synthesis is a consequence of paclitaxel-induced arrest in mitosis. Indeed, dual analysis of DNA and cdc2 protein contents indicated that cdc2 up-regulation occurred in cells arrested with a G2/M DNA content. Furthermore, no up-regulation of cdc2 protein was observed when paclitaxel-treated cells were prevented from entering mitosis by treatment with purvalanol A, a cyclin-dependent kinase (CDK) inhibitor, or stimulated to exit mitosis with 2-AP, a non-specific kinase inhibitor. In addition, when paclitaxel-induced apoptosis was inhibited by Bcl-2 over-expression, cdc2 up-regulation did not occur, leading to a lower level of activation of the cyclin B/cdc2 complex. Taken together, these results indicated that paclitaxel-induced cdc2 protein synthesis participates in a positive feedback loop designed to increase the activity of cyclin B/cdc2 kinase and thus may play a role in paclitaxel-induced apoptosis.
Chadebech
P
P
Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, Université Paul Sabatier, CNRS, Toulouse, France.
Truchet
I
I
Brichese
L
L
Valette
A
A
D015075:2-Aminopurine / Q000494:pharmacology; D000963:Antimetabolites / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology*; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D016195:G2 Phase / Q000187:drug effects / Q000235:genetics; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects; D015854:Up-Regulation
D000963:Antimetabolites; D000972:Antineoplastic Agents, Phytogenic; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D015075:2-Aminopurine; D004247:DNA; D003513:Cycloheximide; D016203:CDC2 Protein Kinase; D017239:Paclitaxel