Regulation of Bax by c-Jun NH2-terminal kinase and Bcl-xL in vinblastine-induced apoptosis.
Microtubule inhibitors, such as vinblastine, are widely used in cancer chemotherapy. Vinblastine exerts its antitumor effect by inducing apoptosis. In KB-3 cells, we have shown previously that vinblastine activates c-Jun NH(2)-terminal protein kinase (JNK) and causes Bax mitochondrial translocation and activation. In this study, we sought to test the hypothesis that JNK and Bcl-xL act as positive and negative regulators, respectively, of Bax translocation. The JNK inhibitor SP600125 inhibited vinblastine-induced JNK activation and in concert inhibited Bax mitochondrial translocation, Bax oligomerization, and Bax activation. Furthermore, the JNK inhibitor blocked vinblastine-induced apoptosis. The ability of vinblastine to induce Bax translocation and the inhibitory effect of SP600125 were confirmed in cells stably expressing GFP-Bax. However, if transiently overexpressed, Bax localized to the mitochondria, and this was associated with loss of viability and subsequent cell death. If Bcl-xL was co-expressed with Bax, the cells readily tolerated Bax overexpression. Indeed, physical interaction between Bcl-xL and Bax but not Bak was demonstrated by co-immunoprecipitation. These findings provide novel insight into the role of Bax and its regulation in vinblastine-induced apoptosis.
Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
Rong
R
Chu
Meenakshi
M
Upreti
Wen-Xing
WX
Ding
Xiao-Ming
XM
Yin
Timothy C
TC
Chambers
D000873:Anthracenes / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000502:physiology*; D051020:bcl-X Protein / Q000502:physiology*
D000873:Anthracenes; D000972:Antineoplastic Agents, Phytogenic; D047428:Protein Kinase Inhibitors; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C432165:pyrazolanthrone; D014747:Vinblastine; D048031:JNK Mitogen-Activated Protein Kinases