Phosphatidylinositide 3-kinase priming couples c-FLIP to T cell activation.
Cellular FLICE (FADD-like interleukin-1-beta-converting enzyme)-inhibitory protein (c-FLIP) inhibits death receptor-induced apoptosis by binding to FADD (Fas-associated death domain protein) and pro-caspase-8. c-FLIP has also been shown to transmit activation signals and to enhance interleukin (IL)-2 production. However, c-FLIP-mediated T cell activation is difficult to detect in most cells. We found that in DO11.10 T cells, c-FLIP expression led to inhibition of IL-2 production, in contrast to the readily detectable c-FLIP-induced activation in Jurkat cells. A direct comparison revealed that distinct signal pathways were regulated by c-FLIP in Jurkat cells and DO11.10 cells. We investigated whether constitutively activated phosphatidylinositide 3-kinase (PI3K) in Jurkat cells stimulated c-FLIP. Inhibition of PI3K in Jurkat cells abrogated a c-FLIP-mediated increase in IL-2 production. In addition, c-FLIP coordinated with active PI3K for ERK activation. Furthermore, introduction of PTEN back into Jurkat cells eliminated the stimulatory effect of c-FLIP on IL-2 production and ERK activation. Our results suggest that priming with PI3K promotes the coupling of c-FLIP to T cell activation.
Fang
Li-Wen
LW
Graduate Institute of Life Science, National Defense Medical Center, Taipei 11472, Taiwan.
Tai
Tzong-Shyuang
TS
Yu
Wan-Ni
WN
Liao
Fang
F
Lai
Ming-Zong
MZ
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human