PIP3-INDEPENDENT REGULATION OF AKT1 ACTIVITY IN T CELLS

描述（由申请人提供）：IP 4是一种新发现的第二信使，我们确定其对T细胞发育和活化至关重要。IP 4如何传递T细胞受体信号以诱导胸腺细胞成熟仍不清楚。其与膜脂质PIP 3的化学相似性表明其共调节PIP 3效应物，包括丝氨酸/苏氨酸激酶AKT。在这项研究中，我们提出AKT是IP 4下游的一个重要效应子通路，有助于成熟CD 4或CD 8 T细胞和调节性T细胞的发育。我们假设IP 4通过从膜释放活性AKT和促进AKT与钙调蛋白（一种Ca 2+传感蛋白质功能调节剂）结合来促进AKT活性。为了验证这一假设，我们提出了三个具体目标。首先，我们将通过竞争性抑制分析来表征AKT与IP 4和PIP 3的结合。其次，我们将确定IP 4如何调节AKT定位，激活和下游效应的磷酸化。最后，我们将研究钙调素结合对体内AKT功能的重要性，并确定其对IP 4的依赖性。 我们希望阐明IP 4调节AKT活性的机制将有助于更好地理解发育信号如何精确和差异地诱导AKT激活，以促进不同T细胞亚群的成熟。我们的长期目标是表征IP 4如何从T细胞表面受体传递信号，以指导特异性和保护性免疫反应。 公共卫生相关性：ITPKs产生IP 4，这是T细胞发育和激活所需的一种新的第二信使，也与自身免疫性有遗传联系。该提案旨在了解原癌基因AKT的IP 4调节如何控制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.