Mechanism of T Cell Receptor Mediated Activation of NFkappaB

描述（由申请人提供）：在T细胞受体（TCR）接合后转录因子NF-κ B的活化对于适应性免疫应答期间的T细胞增殖和活化很重要。最近的报道已经描述了一种信号传导途径，其涉及激酶PKC θ、支架蛋白CARD 11（也称为CARMA-1）、含有CARD结构域的蛋白BcMO和paracaspase（与半胱天冬酶相关的蛋白酶）MALT 1作为连接TCR与IkappaB激酶（IKK）复合物的关键中间体。然而，该信号通路激活后发生的事件的确切顺序仍然不清楚。我们最近已经证明，3-磷酸肌醇依赖性激酶1（PDK 1）在这一途径中具有重要作用，通过调节PKC θ的激活，并通过信号依赖性招募PKC θ和CARD 11的脂筏。PDK 1相关的PKCq募集IKK复合物，而PDK 1相关的CARD 11募集Bcl 10-MALT 1复合物，从而允许通过称为NEMO的IKK复合物亚基的Bcl 10-MALT 1依赖性泛素化激活IKK复合物。因此，PDK 1通过使T细胞中TCR诱导的NF-κ B活化途径成核而发挥关键作用。在本提案中，我们将进一步扩展我们的观察，以更好地理解PDK-1如何招募PKC theta和CARD 11。我们将确定参与这些相互作用的领域，并利用这些研究的知识来设计抑制T细胞活化的新方法。此外，我们还发现PKC θ通过由内而外的途径参与TCR参与后LFA 1的激活。我们将通过产生新的遗传模型来确定这一途径的重要性，我们相信这一模型将使PKC θ作为IKK募集的适配器发挥作用的能力与其通过对LFA 1的作用促进稳定结合和免疫突触的能力分离。我们相信，这些研究将提供对关键细胞通路的更全面的理解，并有机会开发新的免疫抑制方法。

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.