Opposing roles of c-Jun NH2-terminal kinase and p38 mitogen-activated protein kinase in the cellular response to ionizing radiation in human cervical cancer cells.
Exposure of cells to ionizing radiation induces activation of multiple signaling pathways that play critical roles in determining cell fate. However, the molecular basis for cell death or survival signaling in response to radiation is unclear at present. Here, we show opposing roles of the c-jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) pathways in the mitochondrial cell death in response to ionizing radiation in human cervical cancer cells. Ionizing radiation triggered Bax and Bak activation, Bcl-2 down-regulation, and subsequent mitochondrial cell death. Inhibition of JNK completely suppressed radiation-induced Bax and Bak activation and Bcl-2 down-regulation. Dominant-negative forms of stress-activated protein kinase/extracellular signal-regulated kinase kinase 1 (SEK-1)/mitogen-activated protein kinase kinase-4 (MKK-4) inhibited JNK activation. Radiation also induced phosphoinositide 3-kinase (PI3K) activation. Interestingly, inhibition of PI3K effectively attenuated radiation-induced mitochondrial cell death and increased clonogenic survival. Inhibition of PI3K also suppressed SEK-1/MKK-4 and JNK activation, Bax and Bak activation, and Bcl-2 down-regulation. In contrast, inhibition of p38 MAPK led to enhanced Bax and Bak activation and mitochondrial cell death. RacN17, a dominant-negative form of Rac1, inhibited p38 MAPK activation and increased Bax and Bak activation. Exposure of cells to radiation also induced selective activation of c-Src among Src family kinases. Inhibition of c-Src by pretreatment with Src family kinase inhibitor PP2 or small interfering RNA targeting of c-Src attenuated radiation-induced p38 MAPK and Rac1 activation and enhanced Bax and Bak activation and cell death. Our results support the notion that the PI3K-SEK-1/MKK-4-JNK pathway is required for the mitochondrial cell death in response to radiation, whereas the c-Src-Rac1-p38 MAPK pathway plays a cytoprotective role against mitochondrial cell death.
Kim
Min-Jung
MJ
Laboratory of Molecular Biochemistry, Department of Chemistry, Hanyang University, Seoul, Korea.
Choi
Soon-Young
SY
Park
In-Chul
IC
Hwang
Sang-Gu
SG
Kim
Changil
C
Choi
Young-Hyun
YH
Kim
Haekwon
H
Lee
Kee-Ho
KH
Lee
Su-Jae
SJ
D017209:Apoptosis / Q000528:radiation effects*; D045744:Cell Line, Tumor; D005260:Female; D005720:Gamma Rays; D019254:Genes, bcl-2; D016391:Genes, src; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008928:Mitochondria / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000473:pathology*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
C494772:BAK1 protein, human; C494826:BAX protein, human; C107953:RAC1 protein, human; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020830:rac1 GTP-Binding Protein