Mechanism of T Cell Receptor Mediated Activation of NFkappaB

描述(由申请人提供)：T细胞受体(TCR)结合后转录因子NF-kappaB的激活对T细胞在适应性免疫反应中的增殖和激活非常重要。最近的报道描述了一种信号通路，它涉及PKCtheta、支架蛋白CARD11(也称为CARMA-1)、含有卡域的蛋白BcMO和副半胱氨酸酶(与半胱氨酸酶相关的蛋白酶)MALT1作为连接TCR和IkappaB激酶(IKK)复合体的关键中间体。然而，这一信号通路激活后发生的确切事件序列仍不清楚。我们最近证实，3-磷酸肌醇依赖的激酶1(PDK1)通过调节PKCtheta的激活，以及通过信号依赖的PKCtheta和CARD11向脂筏募集，在这一途径中发挥着重要作用。与PDK1相关的PKCq招募IKK复合体，而与PDK1相关的CARD11招募Bcl10-MALT1复合体，从而允许通过依赖于Bcl10-MALT1的IKK复合体亚基泛素化激活IKK复合体。因此，PDK1通过核化TCR诱导的T细胞中的NF-kappaB活化途径发挥关键作用。在这项提议中，我们将进一步扩大我们的观察范围，以更准确地了解人阵-1是如何招募PKCtheta和CARD11的。我们将确定参与这些相互作用的区域，并利用这些研究的知识来设计抑制T细胞激活的新方法。此外，我们还发现，PKCtheta通过一条由内向外的途径参与了TCR参与后LFA1的激活。我们将通过建立新的遗传模型来确定这一途径的重要性，我们相信这些模型将分离PKCtheta作为IKK招募适配器的能力，以及它通过对LFA1的影响促进稳定的结合和免疫突触的能力。我们相信，这些研究将提供对关键细胞途径的更全面的了解，并提供开发新的免疫抑制方法的机会。

DESCRIPTION (provided by applicant): Activation of the transcription factor NF-kappaB after engagement of the T cell receptor (TCR) is important for T cell proliferation and activation during the adaptive immune response. Recent reports have described a signaling pathway that involves the kinase PKCtheta, the scaffold protein CARD11 (also called CARMA-1), the CARD-domain containing protein BcMO, and the paracaspase (protease related to caspases) MALT1 as critical intermediates linking the TCR to the IkappaB kinase (IKK) complex. However, the exact sequence of events that occurs following the activation of this signaling pathway remains poorly defined. We have recently demonstrated that 3-phosphoinositide-dependent kinase 1 (PDK1) has an essential role in this pathway by regulating the activation of PKCtheta and through signal-dependent recruiting of both PKCtheta and CARD11 to lipid rafts. PDK1-associated PKCq recruits the IKK complex, whereas PDK1-associated CARD11 recruits the Bcl10-MALT1 complex, thereby allowing activation of the IKK complex through Bcl10-MALT1-dependent ubiquitination of the IKK complex subunit known as NEMO. Hence, PDK1 plays a critical role by nucleating the TCR-induced NF-kappaB activation pathway in T cells. In this proposal we will further extend our observations to better understand exactly how PDK-1 recruits PKCtheta and CARD11. We will identify the domains involved in these interactions and use the knowledge from these studies to devise novel approaches for suppressing T-cell activation. In addition we have also found that PKCtheta is involved in the activation of LFA1 following TCR-engagement through an inside-out pathway. We will establish the importance of this pathway by generating novel genetic models that we believe will dissociate the ability of PKCtheta to function as an adapter for recruitment of IKK, from its ability to promote stable conjugation and immunological synapses through its effect on LFA1. We believe that these studies will both provide a fuller understanding of a key cellular pathway, and the opportunity to develop novel approaches for immunosuppression.