TGF-beta inhibits IL-2 production and promotes cell cycle arrest in TCR-activated effector/memory T cells in the presence of sustained TCR signal transduction.
TGF-beta signaling is critical for controlling naive T cell homeostasis and differentiation; however, the biological and biochemical changes induced by TGF-beta in effector/memory T cells are poorly defined. We show that although TGF-beta inhibits effector/memory peripheral blood T lymphoblast proliferation and IL-2 production, the intensity and kinetics for TCR-induced global tyrosine phosphorylation are markedly increased compared with that in untreated cells or naive T cells. After TCR ligation, tyrosine phosphorylation of proximal tyrosine kinases and docking proteins like linker for activation of T cells is maintained for >30 min in TGF-beta-primed cells compared with untreated cells where phosphorylation of these targets returned to basal levels by 10 min. Extended phosphorylation of linker for activation of T cells in treated peripheral blood T selectively prolongs ERK 1/2 signaling and phospholipase C-gamma1 activation leading to increased Ca(2+) flux. A kinase/phosphatase imbalance could not account for extended phosphorylation as CD45R, SHP-1, and SHP-2 expression remains unaltered. The contradiction between prolonged signal transduction and inhibition of proliferation is partially explained by the observation that TGF-beta priming results in ERK 1/2-independent p21 induction and decreased cyclin D1 expression leading to accumulation of T cells in G(0)/G(1) phases of the cell cycle and cell cycle arrest. Despite inhibition of T cell function by TGF-beta priming, TCR and cytokine signaling pathways are intact and selectively extended, suggesting that suppression in the effector/memory T cell is mediated by reprogramming signal transduction, rather than its inhibition as in the naive T cell.
Das
Lopamudra
L
Department of Medicine, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
Levine
Alan D
AD
D002118:Calcium / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007156:Immunologic Memory; D007376:Interleukin-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D051966:Phospholipase C gamma / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation
D016207:Cytokines; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D016212:Transforming Growth Factor beta; D014443:Tyrosine; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D017027:Protein Tyrosine Phosphatases; D051966:Phospholipase C gamma; D002118:Calcium