Regulation and Consequences of Ets1 Downregulation in B Cells

 描述(申请人提供)：B细胞可以被激活以分化为抗体分泌浆细胞(PC)，这是正常免疫功能的关键过程。然而，不受调控的B细胞分化可导致自身抗体的产生和自身免疫性疾病的发展，如系统性红斑狼疮(SLE)。因此，B细胞分化受到严格控制。通过B细胞受体(BCR)或Toll样受体(TLRs)刺激B细胞，通过影响 转录因子在B细胞胞核的表达和活性。平衡这些激活途径的是依赖于许多细胞表面受体(例如，CD22和Siglec-G)的抑制信号通路，这些受体被酪氨酸激酶Lyn磷酸化。这导致了磷酸酶的招募，如SHP1，它逆转了BCR和TLR级联中信号蛋白的激活。更好地了解控制B细胞分化的正负通路将为如何操纵它们来限制自身免疫性疾病中B细胞的激活提供新的线索。我们最近发现转录因子Ets1是一个关键的靶点，它被BCR或TLR阳性信号下调，其表达通过抑制信号级联来维持。因为Ets1阻止B细胞向浆细胞分化，所以它的调节是决定B细胞在刺激下命运的关键事件。在缺乏维持Ets1表达的Ets1或Lyn的情况下，小鼠会积聚浆细胞和自身抗体。因此，维持B细胞中适当的Ets1水平对于预防自身免疫是重要的。在这项提案中，我们将定义B细胞中Ets1下调的原因和后果。在目标1中，我们将进一步研究控制B细胞中Ets1表达的机制。在目标2中，我们将使用Ets1可在B细胞中诱导表达的小鼠来确定未能下调B细胞中Ets1对体液免疫反应和自身免疫发展的后果。在目标3中，我们将确定Ets1在原代人类B细胞中是否同样受到激活信号的下调，SLE相关的Ets1基因多态是否影响Ets1的表达控制，以及SLE患者的B细胞是否表现出Ets1表达减少或更有效的Ets1下调。综上所述，这些研究将进一步加深我们对B细胞分化的分子机制的理解，并可能揭示治疗SLE等疾病的新方法。

 DESCRIPTION (provided by applicant): B cells can be activated to differentiate into antibody-secreting plasma cells (PCs), a process crucial for normal immune function. However, unregulated B cell differentiation can lead to the production of autoantibodies and the development of autoimmune diseases such as systemic lupus erythematosus (SLE). Therefore, B cell differentiation is under tight control. Stimulation of B cells via the B cell receptor (BCR)or Toll-like receptors (TLRs) induces activation, proliferation and differentiation by influencing the expression and activity of transcription factors in the nucleus of the B cell. Counterbalancing these activation pathways are inhibitory signaling pathways dependent on a number of cell surface receptors (for example, CD22 and Siglec-G) that are phosphorylated by the tyrosine kinase Lyn. This results in the recruitment of phosphatases such as SHP1 that reverse activation of signaling proteins in the BCR and TLR cascades. Better understanding of the negative and positive pathways controlling B cell differentiation will provide new clues into how they might be manipulated to limit B cell activation in autoimmune diseases. We have recently identified the transcription factor Ets1 to be a crucial target that is downregulated by positive BCR or TLR signaling, and whose expression is maintained by inhibitory signaling cascades. Because Ets1 blocks B cell differentiation to plasma cells, its regulation is a key event in determining the fate of B cells upon stimulation. In the absence of Ets1 or Lyn, which maintains Ets1 expression, mice accumulate plasma cells and autoantibodies. Therefore maintenance of appropriate Ets1 levels in B cells is important to prevent autoimmunity. In this proposal we will define the causes and consequences of Ets1 downregulation in B cells. In Aim 1, we will further characterize the mechanisms controlling Ets1 expression in B cells. In Aim 2, we will determine the consequences of failure to downregulate Ets1 in B cells for both humoral immune responses and the development of autoimmunity using mice in which Ets1 can be inducibly expressed in B cells. In Aim 3, we will determine whether Ets1 is similarly downregulated by activating signals in primary human B cells, whether SLE- associated Ets1 polymorphisms affect control of Ets1 expression, and whether B cells from SLE patients demonstrate reduced Ets1 expression or more efficient Ets1 downregulation. Taken together, these studies will further our understanding of the molecular mechanisms of B cell differentiation and may reveal novel therapeutic approaches for diseases such as SLE.