PT  - JOURNAL ARTICLE
AU  - Shine-Gwo Shiah
AU  - Shuang-En Chuang
AU  - Min-Liang Kuo
TI  - Involvement of Asp-Glu-Val-Asp-Directed, Caspase-Mediated Mitogen-Activated Protein Kinase Kinase 1 Cleavage, c-Jun N-Terminal Kinase Activation, and Subsequent Bcl-2 Phosphorylation for Paclitaxel-Induced Apoptosis in HL-60 Cells
AID  - 10.1124/mol.59.2.254
DP  - 2001 Feb 01
TA  - Molecular Pharmacology
PG  - 254--262
VI  - 59
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/59/2/254.short
4100  - http://molpharm.aspetjournals.org/content/59/2/254.full
SO  - Mol Pharmacol2001 Feb 01; 59
AB  - Paclitaxel is a novel anticancer drug that has demonstrated efficacy toward treating several malignant tumor types. Here, we demonstrate that c-Jun NH2-terminal kinase (JNK), but not p38 mitogen-activated protein kinase or extracellular signal-regulated kinase 1/2, was persistently activated by paclitaxel or other microtubule-damaging agents within human leukemia HL-60 cells. Overexpression of a dominant-negative mutant, mitogen-activated protein kinase kinase 1 (MEKK1-DN) or treatment with JNK-specific antisense oligonucleotide prevented paclitaxel-induced JNK activation, Bcl-2 phosphorylation and apoptosis. Furthermore, we found that the full-length MEKK1 was cleaved to a 91-kDa carboxyl-terminal fragment at the earlier time of apoptosis induced by microtubule-damaging agents. This cleavage, however, occurred consistently with JNK activation and Bcl-2 phosphorylation, but preceded DNA fragmentation in cells in response to paclitaxel activity. The caspase inhibitor Ac-Asp-Glu-Val-Asp-CHO (DEVD-CHO), but not Ac-Tyr-Val-Ala-Asp-CHO (Ac-YVAD-CHO), effectively blocked MEKK1 cleavage, JNK activation, Bcl-2 phosphorylation, and subsequent apoptosis. Subcellular fractionation revealed that the 91-kDa C-terminal MEKK1 fragment was translocated to cytosol. Notably, the MEKK1 fragment could be coimmunoprecipitated with anti-JNK antibodies, suggesting that a signaling complex of C-terminal MEKK1/stress-activated protein kinase/extracellular-signal regulated kinase 1/JNK formed during apoptosis induced by microtubule-damaging agents. Taken together, our results suggest that disruption of cytoarchitecture by paclitaxel triggers a novel apoptosis-signaling pathway, wherein an active DEVD-directed caspase (DEVDase) initially cleaves MEKK1to generate a proapoptotic kinase fragment that is able to activate JNK and subsequent Bcl-2 phosphorylation, finally eliciting cell death.