A TRANSCRIPTION FACTOR WITHIN LIPID RAFTS MODULATES B CELL SIGNALING VIA THE BCR

脂筏内的转录因子通过 BCR 调节 B 细胞信号传导

• 批准号: 7849906
• 负责人: HALEY O TUCKER
• 金额: $ 19万
• 依托单位: UNIVERSITY OF TEXAS AT AUSTIN
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7849906
• 关键词: Actins; Agammaglobulinaemia tyrosine kinase; Antigen Receptors; Antigens; Attenuated; Autoimmunity; B-Cell Activation; B-Lymphocytes; Binding; Biochemical; Cell Cycle; Cell Cycle Progression; Cell Line; Cell Nucleus; Cell membrane; Cell physiology; Complex; Cysteine; Cytoplasm; Cytoskeleton; DNA; DNA Binding; DNA Binding Domain; Dependence; Development; Dominant-Negative Mutation; Enhancers; Event; F-Actin; Fibroblasts; Gene Expression; Heavy-Chain Immunoglobulins; IGH@ gene cluster; Immune Tolerance; Immune response; Immune system; Immunoglobulins; Immunologic Deficiency Syndromes; Induction of Apoptosis; Maintenance; Matrix Attachment Regions; Membrane; Membrane Microdomains; Microfilaments; Modification; Mus; Nuclear; Nuclear Matrix; Pathway interactions; Post-Translational Protein Processing; Property; Protein Binding; Proteins; Receptor Signaling; Receptors, Antigen, B-Cell; Role; Signal Transduction; Structure; Transgenic Organisms; Tyrosine Phosphorylation; Variant; anti-IgM; base; depolymerization; ezrin; in vivo; mutant; prevent; transcription factor

DESCRIPTION (provided by applicant): How variant signaling strength of the B cell antigen receptor (BCR) complex is transformed into biochemical signals is not well understood. A growing body of evidence indicates that lipid rafts function as platforms for signalling through the BCR. Bright is a B cell-restricted transcription factor that transactivates the immunoglobulin heavy chain (IgH) locus by binding to nuclear matrix attachment regions flanking the IgH intronic enhancer. Bright's DNA binding and transcriptional activities are stimulated by its direct association with Bruton's tyrosine kinase (Btk), the implicated molecule in XLA/xid. Bright undergoes a cell cycle- dependent shuttle between the nucleus and the cytoplasm and is implicated in G1/S cell cycle progression. We discovered that a small (1-2%) pool of Bright resides constitutively within lipid rafts. There it associates with Btk and the BCR signaling complex. Following BCR stimulation by surrogate antigen, Bright is discharged from rafts at a rate proportional to signal strength. An inducible association of Bright with sumoylation E2 and E3 components leads to Sumo-I-modification of Bright and its subsequent discharge from rafts into plasma membranes. BCR stimulation induces a transient, rafts-specific association and subsequent co-discharge of Bright and the F-actin linker protein Ezrin, suggesting a potential role for Bright in microfilament depolymerization - a key event in BCR signaling. This is the first functional demonstration of a transcription factor in lipid rafts. We hypothesize that Bright functions to attenuate BCR signaling; i.e., Bright-depleted signalosomes are more active than Bright-containing signalosomes. In this R21 application, we propose (1) to define the requirements for specification of Bright to lipid rafts; (2) to construct and initiate analysis of mice specifically altered for lipid-rafts-localized Bright; and (3) to identify pathways engaged by lipid rafts-localized Bright to regulate BCR signaling strength. These studies suggest another avenue for the transport of cargo between the membrane and the nucleus. They provide long-term significance for immunological tolerance, autoimmunity and immunodeficiency. Transcription factors are proteins that bind to DNA within the nucleus to initiate gene expression. We discovered that a transcription factor (Bright), which is known to possess this property, also has the unexpected property of localizing within specific structures of the cell membrane (lipid rafts). There Bright functions in an unknown manner to regulate the ability of the B lymphocyte to respond to antigen. Understanding how lipid rafts-localized Bright modulates immune responses will impact on our understanding of immunological tolerance, the immune mechanism that prevents the immune system from reacting against self; i.e., autoimmunity.

描述（由申请人提供）：如何将B细胞抗原受体（BCR）复合物的变异信号强度转化为生化信号。越来越多的证据表明，脂质筏是通过BCR发出信号的平台。 BRIGH是B细胞限制的转录因子，通过与IGH内含子增强子两侧的核基质附着区域结合，通过与核基质附着区域结合来反式激活免疫球蛋白重链（IGH）基因座。 Brigh的DNA结合和转录活性与Bruton的酪氨酸激酶（BTK）的直接关联刺激，这是XLA/XID中所暗示的分子。 Brigh在细胞核和细胞质之间经历了细胞周期依赖性班车，并与G1/S细胞周期进程有关。我们发现，少量（1-2％）的明亮池在脂质筏中组成型。它与BTK和BCR信号复合物相关联。通过替代抗原刺激BCR后，明亮从筏子上以与信号强度成正比的速率排出。 Bright与Sumoylation E2和E3成分的诱导缔合导致Sumo-I修饰及其随后从筏子中排出到质膜中。 BCR刺激诱导瞬时，筏特异性关联以及随后的BRIGHT和F-肌动蛋白接头蛋白Ezrin的共同递送，这表明BRIGHT在微丝解去聚合中具有潜在的作用 - BCR信号传导中的关键事件。这是脂质筏中转录因子的第一个功能演示。我们假设明亮的功能减弱了BCR信号传导；即，鲜艳的信号体比含明亮的信号体更为活跃。在此R21应用程序中，我们建议（1）定义明亮至脂质筏规范的要求； （2）构建和启动分析特异性改变的小鼠，以呈脂质叶片定位的明亮； （3）识别脂质筏定位​​的亮点所带来的途径以调节BCR信号强度。这些研究表明，在膜和细胞核之间运输货物的另一道途径。它们为免疫耐受性，自身免疫性和免疫缺陷提供了长期意义。 转录因子是与核内与DNA结合以启动基因表达的蛋白质。我们发现，具有该特性的转录因子（明亮）也具有在细胞膜特定结构（脂质筏）中定位的意外特性。有未知方式的明亮功能调节B淋巴细胞对抗原反应的能力。了解脂质筏定位​​的明亮调节免疫反应将影响我们对免疫耐受性的理解，这种免疫机制阻止了免疫系统对自我的反应；即自身免疫。