Oncogenic Ras signals through activation of both phosphoinositide 3-kinase and Rac1 to induce c-Jun NH2-terminal kinase-mediated, caspase-independent cell death.
Cells avert the development of malignancy in response to deregulated oncogene expression by activating a regulated cell death pathway. However, the molecular mechanism underlying this oncogene-induced cellular death process remains unclear. Here, we show that retroviral expression of oncogenic H-ras induced cell death in a caspase-independent manner in normal cells. Inhibition of c-Jun NH2-terminal kinase (JNK) by pretreatment with SP600125 or a dominant-negative form of JNK blocked cell death. Rac1 and phosphoinositide 3-kinase (PI3K) were activated in cells overexpressing oncogenic H-ras. Inhibition of Rac1 with RacN17, a dominant-negative form of Rac1, attenuated oncogenic H-ras-induced JNK activation and subsequent cell death. Interestingly, inhibition of PI3K with LY294002 or by small interfering RNA-mediated knockdown of PI3K p85 or p110 subunits also clearly attenuated JNK activation and cell death. No cross talk was observed between Rac1 and PI3K, indicating that these pathways operate in parallel. Our findings show that JNK is necessary for oncogenic H-ras-induced, caspase-independent cell death, and that both PI3K and Rac1 activities are required for JNK activation and cell death. Determining the molecular mechanisms that mediate cell death responses to deregulated oncogenes provides a more refined understanding of cellular disposal processes in normal cells and increases our appreciation of these events as a mechanism for protecting against malignant progression.
Byun
Joo-Yun
JY
Laboratory of Molecular Biochemistry, Department of Chemistry, Hanyang University, Seoul 133-791, Korea.
Kim
Min-Jung
MJ
Yoon
Chang-Hwan
CH
Cha
Hyukjin
H
Yoon
Gyesoon
G
Lee
Su-Jae
SJ
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D004789:Enzyme Activation; D005434:Flow Cytometry; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D018709:Statistics, Nonparametric; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D000873:Anthracenes; D034741:RNA, Small Interfering; C432165:pyrazolanthrone; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins