Mechanisms of NF-kappaB Activation in T Lymphocytes

描述(由申请人提供)： 在免疫应答过程中，核因子-kappaB在T淋巴细胞活化中起着关键作用。当T细胞受体(TCR)与外来抗原结合时，信号转导通路被激活，最终激活NFKB，控制T细胞增殖和功能所必需的基因的表达。虽然关于促炎症细胞因子激活核因子-kB的途径已知很多，但TCR激活核因子-kappaB的机制还不是很清楚。核因子-kappaB途径的关键调节因子是IKK复合体，它使核因子-kappaB抑制物IKappaB磷酸化，并通过泛素-蛋白酶体途径靶向降解该抑制物，从而允许核因子-kappaB进入细胞核控制基因表达。 Bcl10是一种与MALT淋巴瘤有关的卡片结构域蛋白，最近被证明在T淋巴细胞中TCR激活IKK的过程中发挥重要作用。然而，BCLI0并不直接激活IKK，这给我们对TCR下游的信号通路的理解留下了很大的空白。这项提案的主要目标是了解BCL10如何一方面与IKK联系起来，另一方面与TCR联系起来。为了了解Bcl10是如何激活IKK的，我们建立了一个无细胞系统，该系统可以在加入Bcl10蛋白的情况下激活IKK。细胞提取物的分级导致了几个在操作上被定义为IKABs(Bcl10下游的IKK激活剂)的蛋白质的鉴定，它们在体外介导了Bcl10对IKK的激活。值得注意的是，我们发现Bcl10通过泛素依赖但不依赖蛋白酶体的机制激活T细胞中的IKK。这些结果表明，泛素化不仅在先天免疫中发挥调节作用，而且在获得性免疫中也发挥调节作用。我们的下一步是确定IKAB是否以及如何参与T淋巴细胞中IKK的激活(目标1)。我们还将研究Bcl10激活IKAB的机制(目标2)。最后，我们将研究Bcl10是如何被TCR途径中的上游信号分子调节的(目标3)。总而言之，这些研究路线应该有助于更好地理解T细胞中的核因子-kappaB信号通路。这些知识对于理解和治疗各种人类疾病至关重要，包括MALT淋巴瘤和其他免疫疾病。

DESCRIPTION (provided by applicant): NF-KappaB plays a pivotal role in the activation of T lymphocytes during immune responses. Upon engagement of T cell receptor (TCR) with a foreign antigen, a signal transduction cascade is activated, culminating in the activation of NFKB, which controls the expression of genes essential for the proliferation and function of T cells. While much is known about the pathways of NF-KB activation by proinflammatory cytokines, the mechanism by which NF-kappaB is activated by TCR is not well understood. A key regulator of NF-KappaB pathway is the IKappaB kinase (IKK) complex, which phosphorylates the NF-kappaB inhibitor IKappaB and targets this inhibitor for degradation by the ubiquitin-proteasome pathway, thus allowing NF-KappaB to enter the nucleus to control gene expression. BCL10, a CARD domain protein implicated in MALT lymphoma, has recently been shown to play an essential role in IKK activation by TCR in T lymphocytes. However, BCLI0 does not activate IKK directly, leaving a large gap in our understanding of the signaling pathways downstream of TCR. The major goal of this proposal is to understand how BCL10 is linked to IKK on the one hand, and to TCR on the other hand. In an effort to understand how BCL10 activates IKK, we have established a cell free system that activates IKK in response to addition of BCL10 protein. Fractionation of cell extracts led to the identification of several proteins operationally defined as IKABs (IKK Activators downstream of BCL10) that mediate IKK activation by BCL10 in vitro. Significantly, we find that IKK in T cells is activated by BCL10 through a ubiquitin-dependent but proteasome-independent mechanism. These results suggest that ubiquitination plays a regulatory role not only in innate immunity, but also in adaptive immunity. Our next step is to determine whether and how IKABs are involved in IKK activation in T lymphocytes (Aim 1). We will also investigate the mechanisms by which BCL10 activates IKABs (Aim 2). Finally, we will study how BCL10 is regulated by upstream signaling molecules in the TCR pathway (Aim 3). Collectively, these lines of investigation should lead to a better understanding of the NF-KappaB signaling pathways in T cells. Such knowledge is crucial to understanding and treating various human diseases, including MALT lymphoma and other immune disorders.