4-1BB Signaling Activates the T Cell Factor 1 Effector/β-Catenin Pathway with Delayed Kinetics via ERK Signaling and Delayed PI3K/AKT Activation to Promote the Proliferation of CD8+ T Cells
Figure 4
4-1BB signaling induces the delayed activation of β-catenin/TCF1 pathway under the control of PI3K-ERK pathway.
(A–C) Anti-CD3-activated CD8+ T cells were stimulated with 5 µg/ml anti-4-1BB or rat IgG for the indicated times. Western blotting was performed with antibodies against β-catenin, TCF1, FOXO1 and β-actin. (A) Expression levels of FOXO1, TCF1 and β-catenin 0, 15, 30, or 60 min after 4-1BB triggering. (B) Expression levels of FOXO1, TCF1 and β-catenin 1 or 2 days after 4-1BB triggering. (C) The relative expression levels of FOXO1 and TCF1 on days 1 and 2 were calculated. (D–E) Activated CD8+ T cells were pre-incubated with or without 10 µM LY294002 or 10 µM PD98509 for 1 h and then stimulated with anti-4-1BB or rat IgG for 24 h. Western blotting was performed with β-catenin, FOXO1, TCF1, and β-actin antibodies (D), and the relative expression levels of β-catenin, FOXO1 and TCF1 were calculated (E). Naïve indicates CD8+ T cells that were cultured in complete medium for 16 h without anti-CD3. Results in C and E are mean ±SD of three separate experiments (*p<0.05; **p<0.01).