Mechanisms of 4-hydroxy-2-nonenal induced pro- and anti-apoptotic signaling.
In recent years, 4-hydroxy-2-nonenal (4-HNE) has emerged as an important second messenger in cell cycle signaling. Here, we demonstrate that 4-HNE induces signaling for apoptosis via both the Fas-mediated extrinsic and the p53-mediated intrinsic pathways in HepG2 cells. 4-HNE induces a Fas-mediated DISC independent apoptosis pathway by activating ASK1, JNK, and caspase-3. Parallel treatment of 4-HNE to HepG2 cells also induces apoptosis by the p53 pathway through activation of Bax, p21, JNK, and caspase-3. Exposure of HepG2 cells to 4-HNE leads to the activation of both Fas and Daxx, promotes the export of Daxx from the nucleus to cytoplasm, and facilitates Fas-Daxx binding. Depletion of Daxx by siRNA results in the potentiation of apoptosis, indicating that Fas-Daxx binding in fact is inhibitory to Fas-mediated apoptosis in cells. 4-HNE-induced translocation of Daxx is also accompanied by the activation and nuclear accumulation of HSF1 and up-regulation of heat shock protein Hsp70. All these effects of 4-HNE in cells can be attenuated by ectopic expression of hGSTA4-4, the isozyme of glutathione S-transferase with high activity for 4-HNE. Through immunoprecipitation and liquid chromatography-tandem mass spectrometry, we have demonstrated the covalent binding of 4-HNE to Daxx. We also demonstrate that 4-HNE modification induces phosphorylation of Daxx at Ser668 and Ser671 to facilitate its cytoplasmic export. These results indicate that while 4-HNE exhibits toxicity through several mechanisms, in parallel it evokes signaling for defense mechanisms to self-regulate its toxicity and can simultaneously affect multiple signaling pathways through its interactions with membrane receptors and transcription factors/repressors.
Chaudhary
Pankaj
P
Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA.
Sharma
Rajendra
R
Sharma
Abha
A
Vatsyayan
Rit
R
Yadav
Sushma
S
Singhal
Sharad S
SS
Rauniyar
Navin
N
Prokai
Laszlo
L
Awasthi
Sanjay
S
Awasthi
Yogesh C
YC
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000447:Aldehydes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D056970:Co-Repressor Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D019014:fas Receptor / Q000819:agonists / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000447:Aldehydes; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D053418:Death Domain Receptor Signaling Adaptor Proteins; C491901:FAS protein, human; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D019014:fas Receptor; D048848:MAP Kinase Kinase Kinase 5; D048670:MAP Kinase Kinase 4; D053148:Caspase 3; C027576:4-hydroxy-2-nonenal