PIP3-INDEPENDENT REGULATION OF AKT1 ACTIVITY IN T CELLS

描述(申请人提供)：IP4是一种新发现的第二信使，我们发现它对T细胞的发育和激活至关重要。IP4如何传递T细胞受体信号以诱导胸腺细胞成熟尚不清楚。它与膜脂PIP3的化学相似性表明，它共同调节PIP3的效应物，包括丝氨酸/苏氨酸激酶AKT。在这项授权中，我们认为AKT是IP4下游的一个重要的效应通路，有助于成熟的CD4或CD8T细胞和调节性T细胞的发育。我们推测，IP4通过释放膜上活性的AKT，并促进AKT与钙调素的结合来促进AKT的活性。钙调素是一种蛋白质功能的钙敏感调节因子。为了检验这一假设，我们提出了三个具体目标。首先，我们将分别通过竞争抑制分析来表征AKT与IP4和PIP3的结合。其次，我们将确定IP4如何调节AKT的定位、激活和下游效应器的磷酸化。最后，我们将在体内检测钙调蛋白结合对AKT功能的重要性，并确定其对IP4的依赖性。我们希望，阐明IP4调节AKT活性的机制将有助于更好地理解发育信号如何准确和差异地诱导AKT激活，以促进不同T细胞亚群的成熟。我们的长期目标是研究IP4如何传递来自T细胞表面受体的信号来指导特异性和保护性免疫反应。 公共卫生相关性：Itpks产生IP4，这是T细胞发育和激活所需的一种新的第二信使，也与自身免疫有关。这项建议试图了解原癌基因AKT的IP4调控如何控制T细胞功能。

DESCRIPTION (provided by applicant): IP4 is a newly discovered second messenger that we identified to be critical for T cell development and activation. How IP4 transmits T cell receptor signals to induce thymocyte maturation remains unclear. Its chemical similarity to the membrane lipid PIP3 suggests that it co-regulates PIP3-effectors, including the serine/threonine kinase AKT. In this grant, we propose that AKT is an important effector pathway downstream of IP4 that contributes to the development of mature CD4 or CD8 T cells and regulatory T cells. We hypothesize that IP4 promotes AKT activity through release of active AKT from the membrane and by facilitating AKT binding to Calmodulin, a Ca2+ sensing regulator of protein function. To test this hypothesis, we present three specific aims. In the first, we will characterize AKT binding to IP4 and PIP3 individually and by competitive inhibition analysis. Second, we will determine how IP4 regulates AKT localization, activation and phosphorylation of downstream effectors. Lastly, we will examine the importance of Calmodulin binding on AKT function in vivo and determine its dependence on IP4. We hope that elucidating the mechanism by which IP4 regulates AKT activity will allow a better understanding of how developmental signals precisely and differentially induce AKT activation to promote the maturation of different T cell subsets. Our long term objective is to characterize how IP4 relays signals from T cell surface receptors to direct specific and protective immune responses. PUBLIC HEALTH RELEVANCE: Itpks generate IP4, a novel second messenger that is required for T cell development and activation, and has also been genetically linked to autoimmunity. This proposal seeks to understand how IP4 regulation of the proto-oncogene AKT controls T cell function.