The role of positive and negative regulation on ligand discrimination by the TCR signaling pathway

TCR信号通路正向和负向调节对配体辨别的作用

• 批准号: 10615822
• 负责人: Arup K. Chakraborty
• 金额: $ 51.7万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-15 至 2027-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10615822
• 关键词: Agonist; Alleles; Binding; Biochemistry; CD3 Antigens; Cells; Complex; Computer Models; Data; Dependence; Discrimination; Disease; Distal; Event; Feedback; Genetic; Genetic Transcription; Half-Life; Individual; Kinetics; Lead; Ligands; Malignant Neoplasms; Mediating; Membrane; Modeling; Molecular; Noise; Pathway interactions; Patients; Peptide/MHC Complex; Peptides; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphotransferases; Physical condensation; Physics; Play; Probability; Property; Protein Tyrosine Kinase; Proteins; Reagent; Receptor Signaling; Regulation; Rest; Role; Series; Signal Pathway; Signal Transduction; Source; Specificity; Study models; System; T-Cell Activation; T-Cell Receptor; T-Lymphocyte; Testing; Time; Titrations; Tyrosine Phosphorylation; Work; ZAP-70 Gene; adaptive immune response; cancer cell; computer studies; experimental study; immunopathology; in vivo; inhibitor; mouse model; mutant; pathogen; programs; receptor; reconstitution; recruit; response; single molecule; tool

ABSTRACT - PROJECT 2 T lymphocytes (T cells) play a key role in orchestrating an adaptive immune response to infectious pathogens as well as cancer cells. T cells express T cell antigen receptors (TCRs) that respond specifically to MHC- associated antigenic peptides (pMHC) derived from pathogens or mutant self-proteins of cancer cells. Upon TCR engagement with such agonist pMHC, intracellular signaling ensues, ultimately leading to new gene transcription programs required for T cell activation. In the homeostatic state in vivo, naïve T cells require shorter duration TCR engagement with self-pMHC to produce tonic signaling events that are required for their survival and homoeostasis. However, these tonic signals do not lead to cell activation as that would result in immunopathology. The half-life differences between ligands that induce tonic signals and agonists are not large. Kinetic proofreading is considered to be the conceptual framework for understanding the fine specificity with which the TCR signaling pathway discriminates between ligands. In spite of much progress in understanding membrane-proximal TCR signaling and ligand discrimination, how the tonic survival signals qualitatively or quantitatively differ from activation signals is not completely known. Based on preliminary data, we hypothesize that TCR signaling events resulting from interactions with self-pMHC and agonist-pMHC differ because of feedback regulatory mechanisms superimposed on kinetic proofreading both proximally and distally from the TCR. We propose to determine the mechanisms underlying such feedback regulation and their impact on ligand discrimination by bringing together computational modeling, biochemistry, mouse models, and single molecule experiments in live cells and reconstituted systems. We will focus on two specific aims. In Aim 1, we will define negative feedback loops and where they act to regulate ligand discrimination. Our preliminary modeling studies have predicted that that negative feedback, proximal but not distal to the TCR, is important for dampening noise and inappropriate responses to self-pMHC. We will explore the involvement of 3 proximal negative feedback loops. Synergistic computational and experimental studies are expected to identify the sources, nodes of action, and impact of these negative feedback loops on ligand discrimination. In Aim 2, we will determine the mechanisms underlying the formation of the LAT condensate and its role in positive regulatory feedback. Our modeling studies suggest that positive feedback regulation distal from the receptor, but still responsive to TCR-pMHC dwell time, is important for a robust response to stimulation by agonists. Our preliminary experimental data reveal that LAT, a key regulator of TCR signaling, forms discrete condensates in response to individual TCR-pMHC binding events. By combining statistical physics-based modeling with experiments, we will dissect the mechanism of LAT condensation nucleation and its dependence on TCR-pMHC binding dwell time, and the role of LAT condensation in mediating positive feedback regulation via SOS-catalyzed Ras activation. The work proposed in this project bridges studies to be conducted in Projects 1, 3 and 4.

摘要-项目2