Activation of the c-Jun N-terminal kinase (JNK) signaling pathway is essential during PBOX-6-induced apoptosis in chronic myelogenous leukemia (CML) cells.
The mitogen-activated protein (MAP) kinase family is activated in response to a wide variety of external stress signals such as UV irradiation, heat shock, and many chemotherapeutic drugs and leads to the induction of apoptosis. A novel series of pyrrolo-1,5-benzoxazepines have been shown to potently induce apoptosis in chronic myelogenous leukemia (CML) cells, which are resistant to many chemotherapeutic agents. In this study we have delineated part of the mechanism by which a representative compound known as PBOX-6 induces apoptosis. We have investigated whether PBOX-6 induces activation of MAP kinase signaling pathways in CML cells. Treatment of K562 cells with PBOX-6 resulted in the transient activation of two JNK isoforms, JNK1 and JNK2. In contrast, PBOX-6 did not activate the extracellular signal-regulated kinase (ERK) or p38. Apoptosis was found to occur independently of the small GTPases Ras, Rac, and Cdc42 but involved phosphorylation of the JNK substrates, c-Jun and ATF-2. Pretreatment of K562 cells with the JNK inhibitor, dicoumarol, abolished PBOX-6-induced phosphorylation of c-Jun and ATF-2 and inhibited the induced apoptosis, suggesting that JNK activation is an essential component of the apoptotic pathway induced by PBOX-6. Consistent with this finding, transfection of K562 cells with the JNK scaffold protein, JIP-1, inhibited JNK activity and apoptosis induced by PBOX-6. JIP-1 specifically scaffolds JNK, MKK7, and members of the mixed-lineage kinase (MLK) family, implicating these kinases upstream of JNK in the apoptotic pathway induced by PBOX-6 in K562 cells.
Mc Gee
Margaret M
MM
Department of Biochemistry, Trinity College, Dublin 2, Ireland.
Campiani
Giuseppe
G
Ramunno
Anna
A
Nacci
Vito
V
Lawler
Mark
M
Williams
D Clive
DC
Zisterer
Daniela M
DM
D051698:Activating Transcription Factor 2; D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D001728:Dicumarol / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000201:enzymology* / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010077:Oxazepines / Q000494:pharmacology*; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D015398:Signal Transduction; D013379:Substrate Specificity; D014157:Transcription Factors / Q000378:metabolism
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D002352:Carrier Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; C490666:MAPK8IP1 protein, human; D010077:Oxazepines; D016755:Proto-Oncogene Proteins c-jun; D011758:Pyrroles; D014157:Transcription Factors; D001728:Dicumarol; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C418868:PBOX-6