Cyclic AMP inhibits JNK activation by CREB-mediated induction of c-FLIP(L) and MKP-1, thereby antagonizing UV-induced apoptosis.
The cyclic AMP (cAMP) signaling pathway has been reported to either promote or suppress apoptosis, in a cell context-dependent manner. Our previous study has shown that cAMP, by protein kinase A (PKA)-cAMP response element-binding protein (CREB)-dynein light chain (DLC) pathway, negatively regulates mitogen-activated protein kinase p38 activation, thereby contributing to tumor necrosis factor (TNF)-alpha-induced apoptosis in certain types of cells. However, it remains largely unknown how cAMP suppresses apoptosis. Here we report that cAMP antagonized UV-induced apoptosis in Rat-1 and NIH 3T3 cells. Despite that cAMP significantly suppressed UV-induced p38 activation, inhibition of p38 activity showed no significant effect on UV-induced cell death in both cell lines. Further studies revealed that cAMP antagonized UV-induced apoptosis by inhibition of c-Jun N-terminal protein kinase (JNK) activation. The induction of the long form of cellular FLICE-inhibitory protein (c-FLIP(L)) and mitogen-activated protein kinase phosphatase-1 (MKP-1), but not DLC and p21(WAF1) by CREB was required for cAMP-mediated inhibition of JNK activation. The suppression by cAMP of UV-induced apoptosis was reversed by c-FLIP(L) small-interfering RNA (siRNA) or MKP-1 siRNA, which released the inhibition of JNK activation by cAMP. Thus, our results provide a molecular mechanism by which cAMP suppresses JNK activation and antagonizes apoptosis.
Department of Molecular Immunology, Institute of Basic Medical Sciences, 27 Taiping Road, Beijing 100850, PR China. zhangjy@nic.bmi.ac.cn
J
J
Zhang
Q
Q
Wang
N
N
Zhu
M
M
Yu
B
B
Shen
J
J
Xiang
A
A
Lin
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004790:Enzyme Induction; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015290:Second Messenger Systems / Q000502:physiology; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C493957:Cdkn1a protein, mouse; C506387:Cflar protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D050759:Cyclin-Dependent Kinase Inhibitor p21; C430864:DLC-1 (deleted in liver cancer) protein, mouse; D020690:GTPase-Activating Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D000242:Cyclic AMP; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D054638:Dual Specificity Phosphatase 1