NF-kappaB inhibition enhances caspase-3 degradation of Akt1 and apoptosis in response to camptothecin.
DNA damaging agents, such as camptothecin, and ionizing radiation (IR), can induce both NF-kappaB activation and apoptosis, however, the mechanism of their inter-regulation is not yet clear. In the present study, we discovered that Akt1 is degraded when cells deficient in Ataxia Telangiectasia mutated (ATM) were treated to CPT for apoptosis induction. While CPT-induced NF-kappaB activation could not be detected in ATM-deficient AT5BIVA cells, caspase-3 activation occurred and was even further enhanced by pretreatment with proteasome inhibitor-1 (Pro1), a NF-kappaB inhibitor. In contrast, activation of NF-kappaB but not of caspase-3 by CPT could be found in normal MRC5CV1 cells. NF-kappaB inhibition by Pro1, dominant negative mutant IkappaBalpha (S32/36) or p65 (N250), however, induced the caspase-3 activation in the normal cells, indicating the role of ATM-mediated NF-kappaB activation against cell apoptosis. On the other hand, interestingly, CPT significantly reduced the level of Akt1, this effect further enhanced by Pro1 pretreatment in AT5BIVA cells. In MRC5CV1 cells, however, Akt1 level could be reduced only when CPT and NF-kappaB inhibitors were co-treated to the cells, and this reversed by DEVD-cho treatment, demonstrating the caspase-3-mediated Akt1 degradation. Moreover, although MRC5CV1 cells were much more resistant to CPT compared with AT5BIVA, wortmannin and LY294002 significantly increased the chemosensitivity of MRC5CV1 cells to CPT. Given the accumulating evidences demonstrating Akt as a promising anticancer therapeutic target, all these results suggest that DNA damage induced apoptosis could be regulated by ATM-mediated NF-kappaB activation, and that Akt1 degradation be necessarily required for this apoptotic process.
He
Long
L
Functional Metabolomics Research Center, KRIBB, Daejeon, Yuseong, 305-806, Korea.
Kim
Bo Yeon
BY
Kim
Kyoung A
KA
Kwon
Osong
O
Kim
Sun Ok
SO
Bae
Eun Young
EY
Lee
Myung Sun
MS
Kim
Min Soo
MS
Jung
Mira
M
Moon
A
A
Bae
Kihwan
K
Ahn
Jong Seog
JS
D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*
D004791:Enzyme Inhibitors; D016328:NF-kappa B; D008156:Luciferases; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D002166:Camptothecin