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）：B细胞抗原受体（BCR）复合物的变异信号强度如何转化为生化信号尚不清楚。越来越多的证据表明，脂筏作为平台，通过BCR信号。Bright是一种B细胞限制性转录因子，通过结合IgH内含子增强子侧翼的核基质附着区，反式激活免疫球蛋白重链（IgH）基因座。 Bright的DNA结合和转录活性通过其与布鲁顿酪氨酸激酶（Btk）的直接缔合而被刺激，所述酪氨酸激酶（Btk）是XLA/xid中的牵连分子。Bright在细胞核和细胞质之间进行细胞周期依赖性穿梭，并参与G1/S细胞周期进程。我们发现，一个小的（1-2%）池的光明居住组成内的脂筏。在那里，它与Btk和BCR信号复合物相关联。BCR刺激后的替代抗原，明亮的是从筏放电率成正比的信号强度。Bright与sumoylation E2和E3组分的可诱导关联导致Bright的Sumo-I-修饰及其随后从筏到质膜的放电。BCR刺激诱导Bright和F-肌动蛋白连接蛋白Ezrin的瞬时、筏特异性缔合和随后的共放电，表明Bright在微丝解聚中的潜在作用-这是BCR信号传导中的关键事件。这是第一次在脂筏转录因子的功能演示。我们假设Bright的作用是减弱BCR信号传导;即，耗尽的信号体比含有的信号体更活跃。在该R21应用中，我们建议（1）定义Bright对脂筏的规格要求;（2）构建并启动对脂筏定位Bright特异性改变的小鼠的分析;（3）确定脂筏定位Bright参与调节BCR信号强度的途径。这些研究提出了在细胞膜和细胞核之间转运货物的另一种途径。它们为免疫耐受、自身免疫和免疫缺陷提供了长期意义。 转录因子是与细胞核内的DNA结合以启动基因表达的蛋白质。我们发现，已知具有这种性质的转录因子（Bright）也具有位于细胞膜特定结构（脂筏）内的意想不到的性质。Bright以一种未知的方式调节B淋巴细胞对抗原应答的能力。了解脂筏定位的Bright如何调节免疫反应将影响我们对免疫耐受性的理解，免疫耐受性是防止免疫系统对自身产生反应的免疫机制;即，自身免疫