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。公共卫生相关性这项建议试图了解两个重要的信号分子PLC31和PLC32在B淋巴细胞发育中的作用，包括自身反应性B细胞的去除，以及PLC3调节这些过程的分子机制。这项研究可能为自身免疫和免疫缺陷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新靶点。

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. PUBLIC HEALTH RELEVANCE This proposal seeks to understand the roles of two important signaling molecules PLC31 and PLC32 in the development of B lymphocytes, including the removal of autoreactive B cells, and the molecular mechanism by which PLC3s regulate these processes. The study may provide new clues to the molecular pathogenesis of autoimmune and immunodeficiency diseases, and help identify novel targets for specific therapies.