RESUMO
Systemic lupus erythematosus (SLE) is characterized by abnormal signal transduction mechanisms in T lymphocytes. Linker for activation of T cells (LAT) couples TCR/CD3 activation with downstream signaling pathways. We reported diminished ERK 1/2 kinase activity in TCR/CD3 stimulated lupus T cells. In this study we evaluated the expression, phosphorylation, lipid raft and immunological synapse (IS) localization and colocalization of LAT with key signalosome molecules. We observed a diminished expression and an abnormal localization of LAT in lipid rafts and at the IS in activated lupus T cells. LAT phosphorylation, capture by GST-Grb2 fusion protein, and coupling to Grb2 and PLCγ1, was similar in healthy control and lupus T cells. Our results suggest that an abnormal localization of LAT within lipid rafts and its accelerated degradation after TCR/CD3 activation may compromise the assembly of the LAT signalosome and downstream signaling pathways required for full MAPK activation in lupus T cells.
Assuntos
Lúpus Eritematoso Sistêmico/imunologia , Ativação Linfocitária , Microdomínios da Membrana/imunologia , Transdução de Sinais , Linfócitos T/imunologia , Adolescente , Adulto , Criança , Humanos , Lúpus Eritematoso Sistêmico/metabolismo , Microdomínios da Membrana/metabolismo , Pessoa de Meia-Idade , Fosforilação , Complexo Receptor-CD3 de Antígeno de Linfócitos T/imunologia , Complexo Receptor-CD3 de Antígeno de Linfócitos T/metabolismo , Linfócitos T/metabolismo , Adulto JovemRESUMO
Some of the signaling phenotypic abnormalities observed in peripheral blood T cells from patients with systemic lupus erythematosus resemble those seen in cells anergized by stimulation through the TCR/CD3 complex, in the absence of costimulatory signals, or by stimulation with altered ligands. The potential association of this "anergic" phenotype and the triggering of autoimmune responses in human lupus is discussed.
Assuntos
Lúpus Eritematoso Sistêmico/imunologia , Complexo Receptor-CD3 de Antígeno de Linfócitos T/metabolismo , Linfócitos T/imunologia , Autoimunidade , Anergia Clonal , Humanos , Microdomínios da Membrana/fisiologia , Transdução de Sinais , Linfócitos T/químicaRESUMO
The integrity of the Ras/Raf/mitogen-activated protein kinase (MAPK) cascade is critical for maintenance of T cell tolerance, a process that fails in patients with systemic lupus erythematosus (SLE). In this study we have examined the activity of mitogen-activated protein kinases ERK-1 and ERK-2 in resting and TCR-activated peripheral blood T lymphocytes from patients with SLE. We also examined the binding of Ras guanine nucleotide exchange factor, human Son of Sevenless (hSos), to cytosolic adapter protein growth factor receptor-bound protein 2. T cells from lupus patients showed diminished catalytic activity and TCR-driven dual phosphorylation of ERK-1 and ERK-2 upon stimulation through the TCR/CD3 receptor, a defect that may be related to altered translocation of hSos to the Ras/Raf membrane complex and diminished nuclear translocation of trans-acting factor AP-1. Defective MAPK activity triggered by TCR/ CD3 activation may alter the coordination of signals needed for normal interleukin-2 production and maintenance of tolerance in lupus T cells.