Individual and Collaborative Roles in T Cell Activation

T 细胞激活中的个体和协作作用

• 批准号: 6653204
• 负责人: Renren Wen
• 金额: $ 29.95万
• 依托单位: VERSITI WISCONSIN, INC.
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6653204
• 关键词: T cell receptor; T lymphocyte; autoimmunity; biological signal transduction; cell differentiation; enzyme activity; genetically modified animals; laboratory mouse; phospholipase C

DESCRIPTION (provided by the applicant): Development of T cells is an ordered process tightly controlled by signals emanating from the T cell receptor (TCR) or pre-TCR. The transition of CD4-CD8- double negative (DN) to CD4-CD8+ double positive (DP) thymocytes is governed by the pre-TCR. At the DP stage, thymocytes that have successfully rearranged their TCR undergo a selection process that allows self MHC-restricted and functionally competent but not autoreactive T cells to survive and mature. The current accepted hypothesis proposes that the avidity of TCR engagement determines the outcome of the selection. It is presumed that the degrees of affinity of TCR/MHC interaction determine the levels of TCR signaling strength, which consequently result in thymic selection. However, it is not clear what signaling molecules are involved in regulating the distal TCR signaling pathways linked to cellular responses. One of the early events in T cell activation is stimulation of phospholipid-specific phospholipase C (PLC)-gamma, which mediates calcium mobilization, PKC activation and activation of the Ras pathway, all of which are important for TCR signaling. PLCgamma has two isoforms, PLC-gamma1 and PLC-gamma2. It is believed that PLC-gamma1 accounts for all the PLC-gamma activity in T cells. However, our preliminary data suggest that PLC-gamma2 is also involved in TCR signaling, but its role is only revealed when PLC-gamma1 expression is reduced. Although previous cell line studies indicated an important role of PLC-gamma1 in TCR signaling, the function of PLC-gamma1 in T cell development has not been directly examined in vivo. Here, we propose that PLC-gamma activity is crucial for T cell development at both the pre-TCR and TCR signaling stages. We believe PLC-gamma activity is important for T cell positive and negative selection, and quantitative stimulation of PLC-gamma results in differential activation of the downstream signaling pathways relevant to thymic selection. The finding that both PLC-gamma1 and PLC-gamma2 are involved in TCR signaling provides us a model to analyze the influence of progressive reduction of PLC-gamma on T cell development and TCR activation. We propose to study the role of PLC-gamma in T cell positive and negative selection in Aim 1. The influence of quantitative PLC-gamma activation on the distal TCR signaling events related to T cell selection will be examined in Aim 2. In Aim 3 we will examine the role of PLC-gamma1 and PLCgamma2 in pre-TCR and TCR signaling by examining T cell development in mice null for PLC-gamma1 alone or for both PLC-gamma1 and PLC-gamma2 in the T cell lineage. Overall, these studies should define the role of PLC-gamma1 as well as PLC-gamma2 in TCR signaling and T cell development, and may provide the basis for the design of drugs that can selectively inhibit PLC-gamma downstream pathways and thus manipulate T cell activation.

描述（由申请人提供）：T细胞的发育是一个有序的过程，由T细胞受体（TCR）或前TCR发出的信号严格控制。CD4-CD8-双阴性（DN）胸腺细胞向CD4-CD8+双阳性（DP）胸腺细胞的转变是由tcr前调控的。在DP阶段，成功重排TCR的胸腺细胞经历了一个选择过程，允许自身mhc限制和功能胜任但不具有自身反应性的T细胞存活和成熟。目前公认的假设认为，企业高管参与的热情程度决定了选择的结果。据推测，TCR/MHC相互作用的亲和程度决定了TCR信号强度的水平，从而导致胸腺选择。然而，目前尚不清楚哪些信号分子参与调节与细胞反应相关的远端TCR信号通路。T细胞激活的早期事件之一是磷脂特异性磷脂酶C (PLC)- γ的刺激，它介导钙动员、PKC激活和Ras通路的激活，所有这些对TCR信号传导都很重要。PLCgamma有两个异构体，PLC-gamma1和PLC-gamma2。我们认为，在T细胞中所有的plc - γ活性都是由plc - γ - 1引起的。然而，我们的初步数据表明PLC-gamma2也参与TCR信号传导，但其作用仅在PLC-gamma1表达减少时才被揭示。尽管之前的细胞系研究表明PLC-gamma1在TCR信号传导中起重要作用，但PLC-gamma1在T细胞发育中的功能尚未在体内直接研究。在这里，我们提出plc - γ活性在TCR前和TCR信号传导阶段对T细胞发育至关重要。我们认为plc - γ活性对T细胞的阳性和阴性选择很重要，定量刺激plc - γ会导致与胸腺选择相关的下游信号通路的差异激活。发现PLC-gamma1和PLC-gamma2都参与TCR信号传导，为我们分析PLC-gamma逐渐减少对T细胞发育和TCR激活的影响提供了一个模型。我们建议在Aim 1中研究plc - γ在T细胞阳性和阴性选择中的作用。定量plc - γ激活对与T细胞选择相关的远端TCR信号事件的影响将在Aim 2中进行研究。在Aim 3中，我们将检查PLC-gamma1和PLCgamma2在TCR前和TCR信号传导中的作用，方法是检查T细胞谱系中PLC-gamma1单独或PLC-gamma1和PLC-gamma2均不存在的小鼠的T细胞发育。总的来说，这些研究应该明确PLC-gamma1和PLC-gamma2在TCR信号传导和T细胞发育中的作用，并可能为设计能够选择性抑制PLC-gamma下游通路从而操纵T细胞激活的药物提供基础。