PIK3IP1 in B Cell Development and Function

与多种外源抗原反应但仍保持自身免疫的B细胞库的开发 耐受对于针对病原体的有效免疫应答和自身免疫的预防是至关重要的。 这一过程的中断会导致免疫缺陷、自身免疫性疾病如系统性狼疮 红斑狼疮（SLE）和B细胞恶性肿瘤。对介导正常B细胞信号的理解 开发和功能将可能导致开发用于这些病症的新治疗剂。 几种B细胞信号传导途径的一种重要组分，包括但不限于B细胞抗原 在BCR途径中，PI3激酶（PI3K）是一个重要的信号通路。PI3K的产物PIP3结合到一个人细胞膜的PH结构域。 许多关键的B细胞信号分子，包括Akt和Btk，将它们募集到质膜 在那里它们可以形成信号复合物，被激活，获得底物， 下游信号PI3 K信号传导对于B细胞发育和活化的许多方面是至关重要的。的 在骨髓中B细胞发育过程中，PI3 K信号的受控波动促进了 通过调节Rag蛋白所处的阶段， 或者没有表达出来。在外周，PI3 K促进B细胞的活化和增殖，控制选择性免疫应答， 在浆细胞分化和类别转换之间，并调节B细胞亚群分布。一致 由于其在B细胞的整个生命周期中的关键作用，PI 3 K信号传导受到严格调节。绝大多数 对B细胞中PI3 K信号负调节的研究集中在两种肌醇磷酸酶， PTEN和SHIP，其作用于PI3K下游以使其产物去磷酸化。很少有人关注 支付给调节其催化活性的PI3K上游调节因子。PIK3IP1是一种跨膜蛋白， 与PI3K的p110催化亚基相互作用，最近已显示下调PI3K的活性 几种细胞类型。虽然其在B细胞中的作用尚不清楚，但其在B细胞发育过程中的表达模式 强烈表明PIK3 IP 1控制B谱系中至少一些PI3 K介导的功能，这是一种假设， 我们将测试如下。在目标1中，我们将在B细胞系中过表达和敲低PI3 KIP 1，原代 脾B细胞和原代前B细胞，并测量PI3 K介导的事件如BCR 信号传导，浆细胞分化和类别转换之间的选择，以及Rag表达。在目标2中， 我们将产生B细胞特异性缺失PI3 KIP 1的小鼠，并进行与目的1中类似的测定。我们将 还测量了PI3 KIP 1缺乏对B细胞发育和亚群分布、体液免疫和免疫功能的影响。 反应，自身抗体和受体编辑的发展。这些研究的结果将提供 关于PI3K活性的新型调节剂的重要信息，并可能揭示新的治疗方法 免疫缺陷、自身免疫或B细胞恶性肿瘤。

Development of a B cell repertoire that reacts with a diverse range of foreign antigens and yet remains self- tolerant is critical for effective immune responses against pathogens and the prevention of autoimmunity. Disruptions in this process can lead to immunodeficiency, autoimmune diseases such as systemic lupus erythematosus (SLE), and B cell malignancy. An understanding of the signals that mediate proper B cell development and function will likely lead to the development of novel therapeutic agents for these disorders. One important component of several B cell signaling pathways, including but not limited to the B cell antigen receptor (BCR) pathway, is PI3 kinase (PI3K). The product of PI3K, PIP3, binds to the PH domains of a number of critical B cell signaling molecules including Akt and Btk, recruiting them to the plasma membrane where they can form signaling complexes, become activated, gain access to substrates, and transduce downstream signals. PI3K signaling is critical for many aspects of B cell development and activation. The controlled fluctuation of PI3K signaling throughout B cell development in the bone marrow promotes a repertoire enriched in functional but non-autoreactive BCRs by regulating the stages at which Rag proteins are, or are not, expressed. In the periphery, PI3K promotes B cell activation and proliferation, controls the choice between plasma cell differentiation and class switching, and regulates B cell subset distribution. Consistent with its critical role throughout the life of a B cell, PI3K signaling is tightly regulated. The vast majority of research on the negative regulation of PI3K signaling in B cells has focused on two inositol phosphatases, PTEN and SHIP, that act downstream of PI3K to dephosphorylate its product. Much less attention has been paid to upstream regulators of PI3K that modulate its catalytic activity. PIK3IP1, a transmembrane protein that interacts with the p110 catalytic subunit of PI3K, has recently been shown to downregulate the activity of PI3K in several cell types. While its role in B cells is unknown, its expression pattern during B cell development strongly suggests that PIK3IP1 controls at least some PI3K mediated functions in the B lineage, a hypothesis which we will test as follows. In Aim 1, we will overexpress and knockdown PI3KIP1 in B cell lines, primary splenic B cells, and primary pre-B cells in IL-7 cultures and measure PI3K mediated events such as BCR signaling, the choice between plasma cell differentiation and class switching, and Rag expression. In Aim 2, we will generate mice with B cell specific deletion of PI3KIP1 and perform similar assays as in Aim 1. We will also measure effects of PI3KIP1 deficiency on B cell development and subset distribution, humoral immune responses, the development of autoantibodies and receptor editing. These results of these studies will provide important information on a novel regulator of PI3K activity and may shed light on new therapeutic approaches for immunodeficiency, autoimmunity, or B cell malignancy.