RESUMO
Constitutively active PI3K catalytic subunit alpha (PIK3CA) interfered with apoptosis induction downstream of death receptor-signaling complex formation allowing robust caspase-8 activation without triggering the execution steps of apoptosis. In mutant PIK3CA-expressing cells, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95L stimulated nuclear factor kappaB (NFkappaB) activation, invasion, and transition to an amoeboid-like morphology. NFkappaB activation and adoption of amoeboid shape were inhibited by caspase-8 knockdown or FLIP-S expression, but only the cell morphology alterations required caspase-8 activity. Furthermore, we identified caspase-8-mediated, caspase-3-independent cleavage of the protein kinase rho-associated, coiled-coil containing protein kinase 1 as a novel mechanism for acquiring amoeboid shape and enhanced invasiveness in response to TRAIL and CD95L. Taken together, we provide evidence that mutated PIK3CA converts the 'tumor surveillance' activity of cancer cell-expressed death receptors and caspase-8 toward tumor promotion.
Assuntos
Apoptose/genética , Caspase 8/metabolismo , Proteína Ligante Fas/farmacologia , Mutação de Sentido Incorreto/fisiologia , Fosfatidilinositol 3-Quinases/genética , Ligante Indutor de Apoptose Relacionado a TNF/farmacologia , Quinases Associadas a rho/metabolismo , Clorometilcetonas de Aminoácidos/farmacologia , Apoptose/efeitos dos fármacos , Proteína Reguladora de Apoptosis Semelhante a CASP8 e FADD/genética , Caspase 8/genética , Inibidores de Caspase , Forma Celular/efeitos dos fármacos , Forma Celular/genética , Classe I de Fosfatidilinositol 3-Quinases , Inibidores de Cisteína Proteinase/farmacologia , Células HCT116 , Humanos , Quinase I-kappa B/metabolismo , Interleucina-8/metabolismo , Invasividade Neoplásica/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Proteína X Associada a bcl-2/genética , Receptor fas/metabolismo , Quinases Associadas a rho/antagonistas & inibidores , Quinases Associadas a rho/genéticaRESUMO
Soluble TNF-like weak inducer of apoptosis (TWEAK) trimers induce, in a variety of cell lines, translocation of cytosolic tumor necrosis factor (TNF) receptor-associated factor-2 (TRAF2) to a triton X-100-insoluble compartment without changes in the total cellular TRAF2 content. TWEAK-induced TRAF2 translocation is paralleled by a strong increase in nuclear factor kappaB 2 (NFkappaB2)/p100 processing to p52, indicating that TRAF2 redistribution is sufficient for activation of the alternative NFkappaB pathway. In accordance with the crucial role of TRAF2 in proinflammatory, anti-apoptotic TNF receptor-1 (TNFR1) signaling, we observed that TWEAK-primed cells have a reduced capacity to activate the classical NFkappaB pathway or JNK (cJun N-terminal kinase) in response to TNF. Furthermore, TWEAK-primed cells are sensitized for the TNFR1-mediated induction of apoptotic and necrotic cell death. Notably, the expression of the NFkappaB-regulated, TRAF2-interacting TRAF1 protein can attenuate TWEAK-induced depletion of the triton X-100-soluble TRAF2 fraction and improve TNFR1-induced NFkappaB signaling in TWEAK-primed cells. Taken together, we demonstrate that soluble TWEAK desensitizes cells for proinflammatory TNFR1 signaling and thus identify TWEAK as a modifier of TNF signaling.
Assuntos
Apoptose , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Transdução de Sinais , Fatores de Necrose Tumoral/farmacologia , Animais , Linhagem Celular Tumoral , Citocina TWEAK , Fibroblastos/metabolismo , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Camundongos , NF-kappa B/metabolismo , Octoxinol/farmacologia , Fator 1 Associado a Receptor de TNF/metabolismo , Fator 2 Associado a Receptor de TNF/metabolismoRESUMO
It has been shown that tumor necrosis factor receptor-2 (TNFR2) stimulation leads to degradation of TNF receptor associated factor-2 (TRAF2) and inhibition of TNFR1-induced activation of NFkappaB and JNK. Here, we show that TRAF1 inhibits TNFR2-induced proteasomal degradation of TRAF2 and relieves TNFR1-induced activation of NFkappaB from the inhibitory effect of TNFR2. TRAF1 co-recruited with TRAF2 to both TNF receptors. Despite lacking an amino-terminal RING/zinc-finger domain, TRAF1 did not interfere with TNFR1-induced activation of JNK and NFkappaB. It is noted that physiological expression levels of TRAF1 enhanced NFkappaB activation and interleukin-8 (IL8) production induced by TNFR2. Thus, TRAF1 shifts the quality of integrated TNFR1-TNFR2 signaling from apoptosis induction to proinflammatory NFkappaB signaling.
