CD43 Regulation of Immune Responses

描述(申请人提供)：CD43无疑是T细胞表面最丰富的蛋白质之一。最近，它与P53调控和肿瘤存活有关(1)，与微生物与炎性细胞的黏附有关(2-6)，与HIV的发病有关(7-10)，与CDS效应T细胞的凋亡有关(11)。然而，我们对CD43功能的基础知识仍然非常缺乏。事实上，关于这种分子的功能，文献中充斥着看似相互矛盾的发现。在多年来的各种研究中，CD43被定义为共刺激分子、死亡受体、黏附受体、抗黏附分子和T细胞激活和IL-2产生的负调节因子[12]。在过去的授权期内，我们使用结构/功能技术在明确定义的系统中表征CD43功能的参数。在目前的应用中，我们建议确定CD43在这些系统中发挥作用的细胞内机制，从而阐明广泛表达的表面分子的真实功能。这些基础知识对于最终开始了解这种分子在上述病理和正常免疫反应中的作用是必不可少的。尽管我们以前的发现表明CD43的胞外区没有作用，但我们现在提出了一种可能依赖于ECD的CD43作用的新功能：调节T细胞的运输。我们现在已经确定了CD43-ICD中的两个磷酸化位点，其中一个调节T细胞向淋巴结的运输。我们还开发了一种抗体，可以特异性地检测这些位点的磷酸化。此外，我们已经确定PKD和PKA是在体外免疫共沉淀和/或在这些特定位置磷酸化CD43-ICD的激酶。这一提议的总体假设是CD43通过其胞浆尾部的独特位点的磷酸化来调节T细胞的功能。因此，这项资助的目标是确定CD43的磷酸化调节T细胞的运输、黏附和激活的分子相互作用和信号转导事件。

DESCRIPTION (provided by applicant): CD43 is unarguably one of the most abundant proteins on the T cell surface. Recently, it has been implicated in p53 regulation and tumor survival (1), in microbial adhesion to inflammatory cells (2-6), in HIV pathogenesis (7-10) and in CDS effector T cell apoptosis (11). Yet our fundamental knowledge about the function of CD43 is still sorely lacking. In fact, the literature is full of seemingly contradictory findings on the function of this molecule. In various studies over the years, CD43 has been defined as a costimulatory molecule, a death receptor, an adhesion receptor, an anti-adhesion molecule, and a negative regulator of T cell activation and IL-2 production (12). In the past granting period, we have used structure/function techniques to characterize the parameters of CD43 function in clearly defined systems. In the current application, we propose to determine the intracellular mechanisms by which CD43 functions in these systems, and thereby elucidate the true functions of the widely expressed surface molecule. This fundamental knowledge is essential to finally begin to understand the role of this molecule in the above pathologies as well as normal immune responses. Although our previous findings showed no role for the extracellular domain of CD43, we now propose a novel function for the role of CD43 that may depend on the ECD: regulation of T cell trafficking. We have now identified two phosphorylation sites within the CD43-ICD one of which regulates T cell trafficking to the lymph node. We have also developed an antibody that specifically detects phosphorylation at these sites. Further, we have identified PKD and PKA as kinases that either co-immunoprecipitates and/or phosphorylates CD43-ICD in vitro at these specific sites. The overall hypothesis of this proposal is that CD43 regulates T cell function through phosphorylation of unique sites in its cytoplasmic tail. Therefore, the goal of this grant is to determine the molecular interactions and signal transduction events by which phosphorylation of CD43 regulates T cell trafficking, adhesion, and activation.