c-FLIPL enhances anti-apoptotic Akt functions by modulation of Gsk3β activity.
Akt is a serine-threonine kinase that has an important role in transducing survival signals. Akt also regulates a number of proteins involved in the apoptotic process. To find new Akt interactors, we performed a two-hybrid screening in yeast using full-length Akt cDNA as bait and a human cDNA heart library as prey. Among 200 clones obtained, two of them were identified as coding for the c-FLIP(L) protein. c-FLIP(L) is an endogenous inhibitor of death receptor-induced apoptosis through the caspase-8 pathway. Using co-immunoprecipitation experiments of either transfected or endogenous proteins, we confirmed the interaction between Akt and c-FLIP(L). Furthermore, we observed that c-FLIP(L) overexpression interferes with Gsk3-β phosphorylation levels. Moreover, through its effects on Gsk3β, c-FLIP(L) overexpression in cancer cells induced resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). This effect was mediated by the regulation of p27(Kip1) and caspase-3 expression. These results indicate the existence of a new mechanism of resistance to TRAIL in cancer cells, and unexpected functions of c-FLIP(L).
Department of Cellular and Molecular Biology and Pathology, Federico II University of Naples, Naples, Italy.
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Quintavalle
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Incoronato
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Puca
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Acunzo
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Zanca
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Romano
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Garofalo
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Iaboni
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Croce
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Condorelli
D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002460:Cell Line; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053221:TNF-Related Apoptosis-Inducing Ligand; D050760:Cyclin-Dependent Kinase Inhibitor p27; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D053148:Caspase 3; D053181:Caspase 8; D018021:Lithium Chloride