Identification of Specific Roles for Ets-1 in B Cell Tolerance

描述（由申请方提供）：抗体分泌细胞（ASC）产生抗体对于针对许多不同病原体的免疫应答至关重要。然而，在B细胞耐受性被破坏的自身免疫性疾病中，许多ASC分泌自身抗体并以主要方式促成器官病理学。B细胞向ASC的分化由一组关键转录因子控制，包括Ets-1，其作为该过程的负调节因子。在不存在Ets-1的情况下，B细胞经历增强的分化成ASC，其中许多ASC分泌自身抗体，如血清中IgM和IgG自身抗体的高滴度所证明的。最近，Toll样受体（TLR）信号传导，特别是通过TLR 7和TLR 9，已经涉及自身反应性B细胞的活化以分化成ASC.有趣的是，Ets-1缺陷型B细胞在体外表现出对TLR 7和TLR 9配体的增强的应答，并且缺乏TLR衔接蛋白Myd 88的Ets-1敲除小鼠具有减少的自身抗体产生。Toll样受体信号传导是Blimp-1表达的有效诱导剂，Blimp-1是驱动ASC分化的关键转录因子。Ets-1与Blimp-1物理相互作用以抑制Blimp-1结合靶DNA序列的能力。相反，一个密切相关的转录因子Ets-2不能阻断Blimp-1结合或抑制ASC分化。Ets-1也被认为调节控制ASC形成的关键靶基因的表达，但这些靶基因中的大多数的身份仍不清楚。在本申请中，我们提出了多种测定法来进一步确定Ets-1在调节靶基因表达、Blimp-1活性和ASC分化中的作用。这些研究将通过比较Ets-1的生物活性来帮助，Ets-1可以阻断ASC分化，而Ets-2蛋白缺乏这种活性。该建议的具体目的是（1）确定哪些细胞类型需要Ets-1活性以限制ASC形成、自身抗体分泌和自身免疫疾病，（2）检查TLR 7和9配体在激活Ets-1缺陷型B细胞中的体内作用，（3）鉴定调节ASC形成的Ets-1依赖性基因表达途径和（4）鉴定Ets-1依赖性基因表达途径的结构特征。1，其赋予调节ASC发育的独特能力。我们的研究将为B细胞分化的转录调控提供新的见解，特别是在自身抗体分泌的情况下。

DESCRIPTION (provided by applicant): The production of antibodies by antibody-secreting cells (ASCs) is critically important for immune responses to many different pathogens. However, in autoimmune diseases where B cell tolerance is broken, many ASCs secrete autoantibodies and contribute in a major way to organ pathology. The differentiation of B cells into ASCs is controlled by a cohort of key transcription factors including Ets-1, which serves as a negative regulator of this process. In the absence of Ets-1, B cells undergo enhanced differentiation into ASCs many of which secrete autoantibodies as demonstrated by high titers of IgM and IgG autoantibodies in the serum. Recently Toll- like receptor (TLR) signaling, particularly via TLR7 and TLR9, has been implicated in the activation of autoreactive B cells to differentiate into ASCs. Interestingly, Ets-1 deficient B cells exhibit enhanced responses to TLR7 and TLR9 ligands in vitro and Ets-1 knockout mice lacking the TLR adaptor protein Myd88 have reduced autoantibody production. Toll-like receptor signaling is a potent inducer of the expression of Blimp-1, a key transcription factor that drives ASC differentiation. Ets-1 physically interacts with Blimp-1 to inhibit the ability of Blimp-1 to bind target DNA sequences. In contrast, a closely related transcription factor Ets-2 is unable to block Blimp-1 binding or to inhibit ASC differentiation. Ets-1 also is thought to regulate the expression of critical target genes controlling ASC formation, but the identity of most of these targets remains unclear. In this application we propose a variety of assays to further define the role of Ets-1 in regulating target gene expression, Blimp-1 activity and ASC differentiation. These studies will be aided by comparing biological activities of Ets-1, which can block ASC differentiation, with the closely related Ets-2 protein, which lacks this activity. The specific aims of the proposal are (1) to determine which cell types require Ets-1 activity to limit ASC formation, autoantibody secretion and autoimmune disease, (2) to examine the in vivo role of TLR7 and 9 ligands in activating Ets-1 deficient B cells, (3) to identify Ets-1 dependent gene expression pathways regulating ASC formation and (4) to identify structural features of Ets-1 that impart a unique ability to regulate ASC development. Together our studies will provide novel insights into the transcriptional regulation of B cell differentiation particularly in situations of autoantibody secretion.