Differential requirement for the stress-activated protein kinase/c-Jun NH(2)-terminal kinase in RNAdamage-induced apoptosis in primary and in immortalized fibroblasts.
Onconase, an anticancer ribonuclease, damages cellular tRNA and causes caspase-dependent apoptosis in targeted cells (M. S. Iordanov, O. P. Ryabinina, J. Wong, T. H. Dinh, D. L. Newton, S. M. Rybak, and B. E. Magun. Cancer Res. 60, 1983-1994, 2000). The proapoptotic action of onconase depends on its RNase activity, but the molecular mechanisms leading to RNA damage-induced caspase activation are completely unknown. In this study, we have investigated whether onconase activates two signal-transduction pathways commonly stimulated by conventional chemo- and radiotherapy, namely the stress-activated protein kinase (SAPK) cascade and the pathway leading to the activation of nuclear factor-kappa B (NF-kappaB). We found that, in all cell types tested, onconase is a potent activator of SAPK1 (JNK1 and JNK2) and SAPK2 (p38 MAP kinase), but that it is incapable of activating NF-kappaB. Inhibition of p38 MAP kinase activity with a pharmacological inhibitor, SB203580, demonstrated that p38 MAP kinase is not required for onconase cytotoxicity. Using explanted fibroblasts from mice that contain targeted disruption of both jnk1 and jnk2 alleles, we found that JNKs are important mediators of onconase-induced cytotoxicity. Surprisingly, following the immortalization of these same cells with human papilloma virus (HPV16) gene products E6 and E7, additional proapoptotic pathways (exclusive of JNK) were provoked by onconase. Our results demonstrate that onconase may activate proapoptotic pathways in tumor cells that are not able to be accessed in normal cells. These results present the possibility that the cytotoxic activity of onconase in normal cells may be reduced by blocking the activity of JNKs.
Iordanov
M S
MS
Department of Cell and Developmental Biology, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Portland, Oregon 97201, USA.
Wong
J
J
Newton
D L
DL
Rybak
S M
SM
Bright
R K
RK
Flavell
R A
RA
Davis
R J
RJ
Magun
B E
BE
D017209:Apoptosis / Q000187:drug effects*; D002135:Calcium-Binding Proteins; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D004801:Eosine Yellowish-(YS); D006367:HeLa Cells / Q000187:drug effects; D006416:Hematoxylin; D006801:Humans; D015151:Immunoblotting; D008025:Ligases / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D010766:Phosphorylation; D012313:RNA / Q000378:metabolism*; D050857:Synaptotagmins; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000821:virology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D014409:Tumor Necrosis Factor-alpha; C059731:oncogene protein E7, Human papillomavirus type 16; D050857:Synaptotagmins; D012313:RNA; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases; D004801:Eosine Yellowish-(YS); D006416:Hematoxylin