ANALYSIS OF BIDIRECTIONAL SIGNALING MECHANISMS FOR BTLA AND HVEM IN AUTOIMMUNITY

描述(申请人提供)：我们在本计划项目资助的前一个周期中克隆了新型抑制性受体B和T淋巴细胞衰减器(BTLA)，并证实它是免疫反应的重要一般调节因子。通过建立和检测BTLA基因敲除小鼠，我们发现BTLA在几个模型系统中调节免疫反应，包括几个自身免疫模型。我们还识别和描述了影响小鼠BTLA表达和分布的多态。重要的是，BTLA在人类中的多态性最近被认为与类风湿性关节炎的易感性有关，这突显了充分了解BTLA作用机制的重要性。 免疫反应的强度和持续时间的调节对于平衡对病原体的保护性反应和作为其结果的组织损伤至关重要。抑制性受体，如CTLA-4、PD-1和BTLA，可以通过确保存在激活免疫反应的适当阈值，以及通过限制启动反应的强度和持续时间来促进这种平衡。 然而，关于BTLA，仍有许多基本问题尚未解决。我们实验室最近的发现发现，CD28/B7 Ig受体超家族成员BTLA与肿瘤坏死因子受体家族成员疱疹病毒进入介体(HVEM)之间存在着一种完全意想不到的、前所未有的相互作用。我们将hvem确定为BTLA配体是我们先前克隆BTLA配体的目标的一部分，这一发现现在已得到其他人的证实。重要的是要注意，BTLA和HVEM之间的结合发生在小鼠和人类系统中。虽然BTLA可能是抑制性的，但HVEM可以提供激活的、有利于生存的信号。事实上，我们最近的发现和初步数据表明，有证据表明存在双向信号，这种信号有可能同时传递抑制和促进生存的信号。因此，目前的应用旨在剖析BTLA-HVEM相互作用的两个方向，以便在基础水平上了解其对人类自身免疫(如类风湿关节炎)的贡献。我们的目标是：目的1.区分BTLA在不同的免疫反应和自身免疫模型中的细胞内和细胞外作用。目的2.分析BTLA的胞质信号模体。目的3.确定BTLA、LIGH和HVEM之间的双向信号相互作用。 项目简介：自身免疫是健康和人类疾病的一个主要问题，它是由免疫系统的耐受机制的各种失效模式引起的。自身免疫性疾病有多种表现，如针对关节(关节炎)、胰腺内分泌细胞(糖尿病)或肾脏过滤机制(狼疮)的免疫反应。我们的研究旨在分析控制免疫反应正常激活和抑制的基本机制，并将重点放在一个新的基因--B和T淋巴细胞衰减器(BTLA)上，该基因是我们发现并克隆的，是同一资助的前几个周期的一部分。重要的是，BTLA最近被报道与人类对类风湿性关节炎的易感性有关。因此，我们提出的对这种新发现但知之甚少的分子的研究尤其及时。

DESCRIPTION (provided by applicant): We cloned the novel inhibitory receptor B and T Lymphocyte Attenuator (BTLA) in a previous cycle of this Program Project grant, and established that it is an important general regulator of immune responses. By generating and examining BTLA knockout mice, we found that BTLA regulates immune responses in several model systems, including several models of autoimmunity. We also recognized and described polymorphisms in BTLA in the mouse that influence its expression and distribution. Importantly, polymorphisms of BTLA in humans were recently linked to susceptibility to Rheumatoid arthritis, highlighting the importance of fully understanding the mechanism of BTLA action. Regulation of the intensity and the duration of immune responses is a critical for balancing the protective responses against pathogens with damage to tissues that are their result. Inhibitory receptors such as CTLA- 4, PD-1 and BTLA can contribute to this balance by ensuring that appropriate thresholds exist for activating the immune response, and by limiting the intensity and duration of responses that are initiated. However, there are still many basic issues about BTLA that are unresolved. Recent findings by our lab have identified a wholly unexpected and unprecedented interaction between BTLA, a member of the CD28/B7 Ig super family of receptors, with Herpesvirus entry mediator (HVEM), a TNF receptor family member. Our identification of HVEM as the BTLA ligand arose as part of our previous Aims to clone the ligand for BTLA, and this finding has now been confirmed by others. It is important to note that the binding between BTLA and HVEM occurs in the mouse and the human systems. While BTLA may be inhibitory, HVEM can provide activating, pro-survival signals. In fact, our recent findings and preliminary data indicate evidence for a bi- directional signaling, which has potential for delivering both inhibitory and pro-survival signals. Thus, the current application is aimed at dissecting both directions of the BTLA-HVEM interaction so that its contribution to human autoimmunity such as Rheumatoid arthritis can be understood at the basic level. Our aims are: Aim 1. Discriminate cell-intrinsic from cell-extrinsic actions of BTLA in distinct models of immune response and autoimmunity. Aim 2. Analyze the cytoplasmic signaling motifs in BTLA. Aim 3. Determine the bidirectional interactions between BTLA, LIGHT, and HVEM for signaling. Project Narrative: Autoimmunity is a major problem of health and human disease, which result from various modes of failure of the tolerance mechanisms of the immune system. Autoimmune diseases have many kinds of manifestations, such as immune responses that target the joints (arthritis), the endocrine cells of the pancreas (diabetes) or the filtering mechanism of the kidney (Lupus). Our study is directed at analyzing the basic mechanisms that control the normal activation and inhibition of the immune response, and are focused on a new gene, B and T Lymphocyte Attenuator (BTLA), that we discovered and cloned as a part of previous cycles of this same grant. Importantly, BTLA has recently been reported to be involved in the susceptibility in humans to rheumatoid arthritis. Thus, our proposed studies into this newly identified but poorly understood molecule are particularly timely.