Mechanisms of NF-kappaB Activation in T Lymphocytes

描述（由申请人提供）： NF-κ B在免疫应答期间T淋巴细胞的活化中起关键作用。在T细胞受体（TCR）与外源抗原接合时，信号转导级联被激活，最终导致NF κ B的激活，NF κ B控制T细胞增殖和功能所必需的基因的表达。虽然对促炎细胞因子激活NF-κ B的途径了解很多，但对TCR激活NF-κ B的机制还不清楚。NF-κ B途径的关键调节因子是IKappaB激酶（IKK）复合物，其磷酸化NF-κ B抑制剂IKappaB并靶向该抑制剂以通过泛素-蛋白酶体途径降解，从而允许NF-κ B进入细胞核以控制基因表达。 BCL 10是MALT淋巴瘤中涉及的CARD结构域蛋白，最近已显示在T淋巴细胞中TCR激活IKK中起重要作用。然而，BCLI0并不直接激活IKK，在我们对TCR下游信号通路的理解中留下了很大的空白。该提案的主要目标是了解BCL 10如何一方面与IKK联系，另一方面与TCR联系。为了了解BCL 10如何激活IKK，我们建立了一个无细胞系统，该系统响应于加入BCL 10蛋白而激活IKK。细胞提取物的分级导致鉴定出几种蛋白质，其在操作上被定义为IKAB（BCL 10下游的IKK激活剂），其在体外介导BCL 10对IKK的激活。值得注意的是，我们发现IKK在T细胞中被BCL 10通过泛素依赖性但不依赖于蛋白酶体的机制激活。这些结果表明，泛素化不仅在先天免疫中起调节作用，而且在获得性免疫中也起调节作用。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（目的1）。我们还将研究BCL 10激活IKAB的机制（目的2）。最后，我们将研究BCL 10如何受TCR通路上游信号分子的调控（Aim 3）。总的来说，这些研究路线应该导致更好地理解T细胞中的NF-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.