Activation of the PI3K-Akt-mTOR signaling pathway promotes necrotic cell death via suppression of autophagy.
Our previous work has shown that autophagy plays a pro-survival function in two necrotic cell death models: zVAD-treated L929 cells as well as H(2)O(2)-treated Bax(-/-)Bak(-/-) mouse embryonic fibroblasts (DKO MEF). This study aims to further explore the regulatory role of autophagy in necrosis by examining the functional role of the phosphoinositide-3 kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) signaling pathway. Our initial intriguing finding was that insulin is able to promote necrotic cell death induced by zVAD and MNNG in L929 cells or by H(2)O(2) in DKO MEF cells cultured in full-growth medium. The pro-necrosis function of insulin was further supported by the observations that insulin is capable of abolishing the protective effect of starvation on necrotic cell death induced by zVAD in L929 cells. Next, we demonstrated that insulin acts on the PI3K-Akt-mTOR pathway to promote necrosis as the suppression of the above pathway by either chemical inhibitors (LY294002 and rapamycin) or mTOR knockdown is able to mitigate the pro-death function of insulin. Finally, we provided evidence that the pro-death function of insulin is dependent on its inhibitory effect on autophagy, which serves as an important pro-survival function in necrosis. Taken together, here we provide compelling evidence to show that activation of the PI3K-Akt-mTOR signaling pathway can promote necrotic cell death via suppression of autophagy, at least in the necrosis models defined in our study in which autophagy serves as a pro-survival function. Data from this study not only further underscore the pro-survival function of autophagy in necrotic cell death, but also provide a novel insight into the intricate connections linking the PI3K-Akt-mTOR signaling pathway with cell death via modulation of autophagy.
Wu
You-Tong
YT
Department of Epidemiology and Public Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Tan
Hui-Ling
HL
Huang
Qing
Q
Ong
Choon-Nam
CN
Shen
Han-Ming
HM
D000818:Animals; D001343:Autophagy / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D009336:Necrosis / Q000201:enzymology* / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases
D004815:Epidermal Growth Factor; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C546843:mTOR protein, mouse