Differential activation of JNK1 isoforms by TRAIL receptors modulate apoptosis of colon cancer cell lines.
Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis on binding to its receptors, death receptor 4 and 5 (DR4, DR5). TRAIL can also activate c-Jun N-terminal kinase (JNK) through the adaptor molecules, TNF receptor-associated factor 2 (TRAF2) and receptor-interacting protein (RIP). The role of JNK in TRAIL-induced tumour cell apoptosis is unclear. In this study, we demonstrate that JNK is activated by TRAIL in colon cancer cells. Inhibition of JNK with L-JNKI reduced rhTRAIL-induced cell death but enhanced cell death induced by selective activation of DR4 or DR5. This difference was unrelated to receptor internalisation or differential activation of c-Jun, but activation of different JNK isoforms. Our data demonstrate that JNK1, but not JNK2 is activated by rhTRAIL in the examined colon cancer cell lines. Although rhTRAIL activated both the long and short isoforms of JNK1, selective activation of DR4 or DR5 led to predominant activation of the short JNK1 isoforms (JNK1alpha1 and/or JNK1beta1). Knockdown of JNK1alpha1 by shRNA enhanced apoptosis induced by TRAIL, agonistic DR4 or DR5 antibodies. On the other hand, knockdown of the long JNK1 isoforms (JNK1alpha2 and JNK1beta2) had the opposite effect; it reduced TRAIL-induced cell death. These data indicate that the short JNK1 isoforms transmit an antiapoptotic signal, whereas the long isoforms (JNK1alpha2 or JNK1beta2) act in a proapoptotic manner.
Cell Stress and Apoptosis Research Group, Department of Biochemistry and National Centre of Biomedical Engineering Science, National University of Ireland, University Road, Galway, Ireland.
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D
Mahalingam
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M
Keane
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Pirianov
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H
Mehmet
A
A
Samali
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Szegezdi
D017209:Apoptosis / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017931:DNA Primers; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D048055:Mitogen-Activated Protein Kinase 8 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism* / Q000627:therapeutic use*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D017931:DNA Primers; D007527:Isoenzymes; D012334:RNA, Neoplasm; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D048055:Mitogen-Activated Protein Kinase 8