Novel lymphocyte-specific Rab GTPase in T cell differentiation

 描述（由申请人提供）：T细胞受体（TCR）连接诱导细胞内信号传导级联，包括在T细胞活化和分化中起关键作用的Ca 2 +-NFAT（活化T细胞核因子）和MAPK（促分裂原活化蛋白激酶）途径。这些途径的缺陷导致人类和小鼠的免疫缺陷或过敏性免疫反应。已知小GTP酶Ras、Rac和Rho在TCR信号传导途径的活化中起核心作用，并且是自身免疫性疾病的治疗靶标。这些小GTP酶通过与信号转导衔接子的相互作用被募集到免疫突触（IS）（抗原呈递细胞和T细胞之间的界面）中，并激活下游MAPK途径。然而，与Ras、Rac和Rho GTPases相反，Rab GTPases家族的60多个成员在T细胞活化中的作用知之甚少。我们的长期目标是揭示Rab GTP酶在TCR信号传导中的作用，以确定新的治疗靶点来减轻自身免疫。我们最近已经鉴定了一种新的Rab GT3，“CRACR 2A GT3”，其在TCR信号传导中起关键作用。我们的初步数据表明，CRACR 2A GTp 3是一种淋巴细胞特异性的大Rab GTp 3，与小GTP酶相比，具有许多功能结构域。我们发现CRACR 2A GT3转位到IS中以激活下游JNK（c-Jun N-末端激酶）MAPK途径。此外，它在TH 1细胞中高度表达，并在IFN-γ和T-bet的表达中起重要作用，从而在自身免疫中起重要作用。我们的中心假设是CRACR 2A GT3通过蛋白质相互作用被募集到IS中，并调节JNK通路以驱动TH 1分化。本提案的目的是使用高分辨率成像技术、基因组学和条件性靶向敲除小鼠来鉴定1）相互作用伴侣，2）GTP结合和异戊烯基化介导的调节，以及3）CRACR 2A GT3在T细胞中的生理作用。CRACR 2A GT3是含有小Rab GT3结构域的大分子的第一个例子。我们希望揭示一个迄今为止未知的JNK通路在T细胞分化中的调节机制。我们有信心，我们也将确定一个独特的信号转导功能的Rab GTP酶，这是否则已知介导的细胞内蛋白质运输。这些机制的研究将有显着的影响，这种新的GTdR治疗自身免疫性疾病的治疗开发。

 DESCRIPTION (provided by applicant): T cell receptor (TCR) ligation induces intracellular signaling cascades including the Ca2+-NFAT (nuclear factor of activated T cells) and MAPK (mitogen-activated protein kinase) pathways that play crucial roles in activation and differentiation of T cells. Defects in these pathways lead to immune deficiency or hypersensitive immune responses in humans and mice. The small GTPases, Ras, Rac and Rho are known to play a central role in activation of TCR signaling pathways and are therapeutic targets in autoimmune diseases. These small GTPases are recruited into the immunological synapse (IS), the interface between an antigen-presenting cell and a T cell via interactions with signaling adaptors and activate the downstream MAPK pathway. However, in contrast to Ras, Rac and Rho GTPases, little is known about the role of more than 60 members of the Rab GTPase family in T cell activation. Our long-term goal is to uncover the role of Rab GTPases in TCR signaling to identify novel therapeutic targets to alleviate autoimmunity. We have recently identified a novel Rab GTPase, "CRACR2A GTPase" that plays a key role in TCR signaling. Our preliminary data show that CRACR2A GTPase is a lymphocyte-specific large Rab GTPase with many functional domains in contrast to small GTPases. We found that CRACR2A GTPase translocates into the IS to activate the downstream JNK (c- Jun N-terminal kinase) MAPK pathway. Furthermore, it is highly expressed in TH1 cells and plays an important role in expression of IFN-γ and T-bet, and thus in autoimmunity. Our central hypothesis is that CRACR2A GTPase is recruited into the IS via protein interactions and regulates the JNK pathway to drive TH1 differentiation. The objective of this proposal is to identify 1) interacting partners, 2) GTP binding and prenylation-mediated regulation, and 3) the physiological role of CRACR2A GTPase in T cells using high resolution imaging techniques, genomics and conditionally targeted knockout mice. CRACR2A GTPase is the first example of a large molecule containing the small Rab GTPase domain. We expect to reveal a hitherto unknown mechanism of regulation of the JNK pathway in T cell differentiation. We are confident that we will also identify a unique signaling function of Rab GTPases, which are otherwise known to mediate only intracellular protein trafficking. These mechanistic studies will have significant impact on therapeutic exploitation of this novel GTPase to treat autoimmune diseases.