PLC?s in B cell biology and autoimmunity

描述(申请人提供)：早期B细胞发育和晚期B细胞成熟分别由前B细胞受体(BCR)和BCR发出的信号调节。在成熟过程中，B细胞对自身抗原的耐受性是通过克隆缺失、受体编辑和无能来建立的，这些过程由BCR发出的信号控制。Pre-bcr/bcr信号的扭曲常常导致B细胞发育缺陷、B细胞耐受性下降以及免疫缺陷和自身免疫性疾病的发生。调节B细胞发育和耐受性的BCR前/BCR信号尚不完全清楚。磷脂酶C3(PLC3)是参与Pre-bcr/bcr信号转导的重要脂酶。PLC3有两种亚型，即PLC31和PLC32。PLC32基因缺陷的小鼠是存活的，并损害了B蛋白的早期和晚期发育。我们最近的数据发现，PLC32在激活轻链基因、编辑自身反应性受体和诱导B细胞无能方面发挥着重要作用。PLC31缺乏会导致妊娠中期早期胚胎死亡，这排除了对其在B细胞发育中的作用的分析。然而，我们对PLC31缺乏杂合子的PLC32缺陷小鼠(PLC31PLC32-/-)的研究表明，PLC31在B的发育中也起着重要的作用。我们最近培育出了PLC31基因可以有条件失活的小鼠。对于具有PLC31和PLC32基因的小鼠，我们处于有利地位，可以进一步研究PLC31/PLC32在B淋巴细胞生成中的单独和联合作用，包括耐受性的建立，以及这两种PLC3调节这一过程的机制。我们推测，PLC31和PLC32在BCR前/BCR介导的功能和建立B细胞耐受中都起着重要作用。为了检验我们的假设，我们提出了三个具体目标。我们将1)确定PLC31以及PLC31和PLC32在BCR前介导的早期B细胞发育、IgH链等位基因排斥、IGL链基因座激活和B细胞库形成中的作用；2)确定PLC31和PLC32在BCR介导的B细胞成熟、受体编辑和诱导B细胞无能中的单独和联合作用；以及3)研究PLC31和PLC32在BCR前/BCR信号转导过程中的上下游通路。这项研究旨在了解两种PLC3亚型在B淋巴细胞生成中的作用，特别是耐受性的建立，以及它们传递来自前BCR/BCR的信号的机制。这项研究可能为自身免疫性疾病的分子发病机制提供新的线索，并有助于确定特定治疗的靶点。

DESCRIPTION (provided by applicant): Early B cell development and late B cell maturation are regulated by signals emanating from the pre-B cell receptor (BCR) and BCR, respectively. During maturation, B cell tolerance to self-antigens is established through clonal deletion, receptor editing and anergy, which are controlled by signals emanating from the BCR. Distorted pre-BCR/BCR signaling often results in defective B cell development, breakdown of B cell tolerance and development of immunodeficiency and autoimmune diseases. Signals from the pre-BCR/BCR that regulate B cell development and tolerance are not fully understood. Phospholipase C3 (PLC3) is an important lipid enzyme involved in pre-BCR/BCR signaling. PLC3 has two isoforms, PLC31 and PLC32. PLC32-deficient mice are viable and have impaired early and late B development. Our recent data find that PLC32 plays an important role in activation of light chain loci, editing of self-reactive receptors and induction of B cell anergy. PLC31 deficiency results in early embryonic death at midgestation, precluding analysis of its role in B cell development. However, our studies of PLC32-deficient mice that are heterozygous for PLC31-deficiency (PLC31PLC32-/-) indicate that PLC31 also plays an important role in B development. We have recently generated mice in which the PLC31 gene can be conditionally inactivated. With the mice that have genetically modified PLC31 and PLC32 genes, we are well-positioned to further study the individual and combined roles of PLC31/PLC32 in B lymphopoiesis, including tolerance establishment, and the mechanism by which both PLC3s regulate the process. We hypothesize that both PLC31 and PLC32 play an important role in pre- BCR/BCR-mediated functions and in establishing B cell tolerance. To test our hypothesis, we propose three specific aims. We will 1) determine the role of PLC31 and combined roles of PLC31 and PLC32 in pre- BCR-mediated early B cell development, allelic exclusion of IgH chain, activation of the IgL chain loci, and formation of the B cell repertoire, 2) determine the individual and combined roles of PLC31 and PLC32 in BCR- mediated B cell maturation, receptor editing and induction of anergy in B cells, and 3) study the upstream and downstream pathways of PLC31 and PLC32 during pre-BCR/BCR signaling. The proposed research seeks to understand the roles for the two PLC3 isoforms in B lymphopoiesis, especially tolerance establishment, and the mechanism by which they relay the signals from the pre-BCR/BCR. The study may provide new clues to the molecular pathogenesis of autoimmune diseases and help identify targets for specific therapies.