PLCgammas in B Cell Biology and Autoimmunity

描述（由申请人提供）：B细胞受体（BCR）转导的信号通过控制克隆缺失、受体编辑和能量来调节B细胞对自身抗原的耐受性。介导B细胞耐受性的BCR信号尚不完全清楚，而引起B细胞耐受性破坏和随之而来的自身免疫性疾病的BCR信号改变则更不清楚。磷脂酶Cg（一种对BCR信号至关重要的脂质酶）的刺激产生二酰基甘油（DAG）和肌醇1,4,5-三磷酸（IP3），分别激活PKCb和Ca2+/钙调磷酸酶途径。PLCg有两个异构体，PLCg1和PLCg2。此前，我们报道了plcg2介导的PKCb/Bcl10/TAK1/IKK/NF-kB信号通路在B细胞成熟和激活、免疫球蛋白轻链位点激活和BCR受体编辑中的关键作用。由于PLCg1缺乏会导致早期胚胎死亡，我们产生了条件PLCg1敲除小鼠，并发现B细胞特异性缺失PLCg1会损害BCR信号并阻止这些小鼠B细胞能量的维持。这些新数据揭示了PLCg1在建立自我耐受性方面的关键但未被充分认识的作用。这些发现的临床相关性是PLCg2突变改变BCR信号并引发人类患者的免疫缺陷和自身免疫性疾病。因此，PLCg通路在控制小鼠和人类的B细胞耐受性中起着重要作用。这项更新应用的主要目的是研究plcg依赖途径将BCR信号的微小定量变化转化为B细胞的质变并使其进入能量状态的分子机制。具体而言，我们将1)确定PLCg1调节B细胞能量的分子机制，2)研究一个新分子如何控制PLCg1及其下游途径调节B细胞能量。这种基于机制的研究将从概念上推进我们对自身抗原调节B细胞能量的分子信号机制的理解。对人类自身免疫性疾病分子发病机制的新认识可能为某些疾病确定新的靶向治疗方法。

DESCRIPTION (provided by applicant): Signals transduced by the B cell receptor (BCR) regulate B cell tolerance to self-antigens by controlling clonal deletion, receptor editing and anergy. BCR signals that mediate B cell tolerance are not fully understood, and altered BCR signaling that elicits the breakdown of B cell tolerance and consequent autoimmune disease is even less well understood. Stimulation of phospholipase Cg (PLCg), a lipid enzyme critical for BCR signaling, generates diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) that activate the PKCb and Ca2+/ calcineurin pathways, respectively. PLCg has two isoforms, PLCg1 and PLCg2. Previously, we reported a key role for the PLCg2-mediated PKCb/Bcl10/TAK1/IKK/NF-kB signaling pathway in B cell maturation and activation, immunoglobulin light chain locus activation, and BCR receptor editing. As PLCg1 deficiency causes early embryonic death, we generated conditional PLCg1 knockout mice, and discovered that B cell-specific deletion of PLCg1 impairs BCR signaling and precludes the maintenance of B cell anergy in these mice. These new data reveal a pivotal yet under-appreciated role for PLCg1 in the establishment of self-tolerance. The clinical relevance of these findings is that PLCg2 mutations alter BCR signaling and elicit immunodeficiency and autoimmune diseases in human patients. Thus, the PLCg pathway plays an essential role in controlling B cell tolerance in both mice and humans. The primary objective of this renewal application is to study the molecular mechanism by which the PLCg-dependent pathway converts a small quantitative change in BCR signaling into qualitative changes in B cells that drives them into a state of anergy. Specifically, we will 1) determine the molecular mechanism by which PLCg1 regulates B cell anergy, and 2) study how a novel molecule controls PLCg and its downstream pathways to regulate B cell anergy. This mechanism-based research will conceptually advance our understanding of the molecular signaling mechanism by which self- antigens regulate B cell anergy. Novel insight into the molecular pathogenesis of human autoimmune disease may identify novel target therapeutics for certain of these diseases.