Cisplatin induces the proapoptotic conformation of Bak in a deltaMEKK1-dependent manner.

Abstract

In a panel of four human melanoma cell lines, equitoxic doses of cisplatin induced the proapoptotic conformation of the Bcl-2 family protein Bak prior to the execution phase of apoptosis. Because cisplatin-induced modulation of the related Bax protein was seen in only one cell line, a degree of specificity in the signal to Bak is indicated. Little is known about upstream regulation of Bak activity. In this study, we examined whether the apoptosis-specific pathway mediated by a kinase fragment of MEKK1 (DeltaMEKK1) is involved in the observed Bak modulation. We report that expression of a kinase-inactive fragment of MEKK1 (dominant negative MEKK [dnMEKK]) efficiently blocked cisplatin-induced modulation of Bak and cytochrome c release and consequently also reduced DEVDase activation and nuclear fragmentation. Accordingly, expression of a kinase-active MEKK1 fragment (dominant positive MEKK) was sufficient to induce modulation of Bak in three cell lines and to induce apoptosis in two of these. dnMEKK did not block cisplatin-induced c-Jun N-terminal kinase (JNK) activation, in agreement with a specifically proapoptotic role for the DeltaMEKK1 pathway. Finally, we show that reduction of Bak expression by antisense Bak reduced cisplatin-induced loss of mitochondrial integrity and caspase cleavage activity in breast cancer cell lines. In summary, we have identified Bak as a cisplatin-regulated component downstream in a proapoptotic, JNK-independent DeltaMEKK1 pathway.

• Authors: A Mandic, K Viktorsson, M Molin, G Akusjärvi, H Eguchi, S I Hayashi, M Toi, J Hansson, S Linder, M C Shoshan
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 21 Issue 11 Pg. 3684-91 (Jun 2001) ISSN: 0270-7306 [Print] United States
• PMID: 11340162 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• BAK1 protein, human
• BAX protein, human
• Cytochrome c Group
• Membrane Proteins
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-bcl-2
• bcl-2 Homologous Antagonist-Killer Protein
• bcl-2-Associated X Protein
• Mitogen-Activated Protein Kinase 9
• Protein Serine-Threonine Kinases
• Mitogen-Activated Protein Kinase 8
• Mitogen-Activated Protein Kinases
• MAP Kinase Kinase Kinase 1
• MAP3K1 protein, human
• Cisplatin

Topics

• Antineoplastic Agents (metabolism, pharmacology)
• Apoptosis
• Cisplatin (metabolism, pharmacology)
• Cytochrome c Group (metabolism)
• Enzyme Activation
• Humans
• MAP Kinase Kinase Kinase 1
• Membrane Proteins (metabolism)
• Mitogen-Activated Protein Kinase 8
• Mitogen-Activated Protein Kinase 9
• Mitogen-Activated Protein Kinases (metabolism)
• Protein Serine-Threonine Kinases (metabolism)
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-bcl-2 (metabolism)
• Tumor Cells, Cultured
• bcl-2 Homologous Antagonist-Killer Protein
• bcl-2-Associated X Protein