TY - JOUR
T1 - Cisplatin induces the proapoptotic conformation of Bak in a ΔMEKK1-dependent manner
AU - Mandic, Aleksandra
AU - Viktorsson, Kristina
AU - Molin, Magnus
AU - Akusjärvi, GÖRAN
AU - Eguchi, Hidetaka
AU - Hayashi, Shin Ichi
AU - Toi, Masakazu
AU - Hansson, Johan
AU - Linder, Stig
AU - Shoshan, Maria C.
PY - 2001/6
Y1 - 2001/6
N2 - 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 (ΔMEKK1) 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 ΔMEKK1 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 ΔMEKK1 pathway.
AB - 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 (ΔMEKK1) 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 ΔMEKK1 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 ΔMEKK1 pathway.
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U2 - 10.1128/MCB.21.11.3684-3691.2001
DO - 10.1128/MCB.21.11.3684-3691.2001
M3 - Article
C2 - 11340162
AN - SCOPUS:0034999880
VL - 21
SP - 3684
EP - 3691
JO - Molecular and Cellular Biology
JF - Molecular and Cellular Biology
SN - 0270-7306
IS - 11
ER -