Contribution of caveolin-1 alpha and Akt to TNF-alpha-induced cell death.
We used retrovirus insertion-mediated random mutagenesis to generate tumor necrosis factor-alpha (TNF-alpha)-resistant lines from L929 cells. Using this approach, we discovered that caveolin-1 alpha is required for TNF-alpha-induced cell death in L929 cells. The need for caveolin-1 alpha in TNF-alpha-induced cell death was confirmed by the restoration of sensitivity to TNF-alpha after ectopic reconstitution of caveolin-1 alpha/beta expression. This caveolin-1 alpha-mutated line was also resistant to H(2)O(2) and staurosporine, but not to lonidamine. HepG2 cells are known to lack endogenous caveolins. HepG2 cells stably transfected with caveolin-1 alpha/beta were found to be much more sensitive to TNF-alpha than either parental cells transfected with caveolin-1 beta or parental cells transfected with an empty vector. In contrast to its extensively documented antiapoptotic effect, the elevated activity of Akt appears to be important in sensitizing caveolin-1-expressing cells to TNF-alpha, since pretreatment of cells with the phosphatidylinositide 3-kinase (PI3K) inhibitor LY-294002 or wortmannin completely blocked PI3K activation and markedly improved the survival of TNF-alpha-treated L929 cells. The survival rates of caveolin-1 alpha-normal and caveolin-1 alpha-deficient L929 cells were comparable after treatment with PI3K inhibitor and TNF-alpha. Similar results were obtained with HepG2 cells that stably expressed caveolin-1 alpha/beta or -beta and parental cells transfected with an empty vector. In summary, our results indicate that caveolin-1 alpha preferentially sensitizes L929 cells to TNF-alpha through the activation of a PI3K/Akt signaling pathway.
Ono
Koh
K
Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Kyoto 612-8555, Japan. kohono@kuhp.kyoto-u.ac.jp
Iwanaga
Yoshitaka
Y
Hirayama
Madoka
M
Kawamura
Teruhisa
T
Sowa
Naoya
N
Hasegawa
Koji
K
D000818:Animals; D051242:Caveolin 1; D022461:Caveolins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D004251:DNA Transposable Elements; D004351:Drug Resistance / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology*; D005822:Genetic Vectors; D006801:Humans; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering / Q000494:pharmacology; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
C495540:CAV1 protein, human; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D002867:Chromones; D004251:DNA Transposable Elements; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt