Role of Molecular Chaperones in Ig Biosynthesis 11-2008

分子伴侣在 Ig 生物合成中的作用 11-2008

• 批准号: 8291321
• 负责人: Linda M Hendershot
• 金额: $ 38.69万
• 依托单位: ST. JUDE CHILDREN'S RESEARCH HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-04-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8291321
• 关键词: 26S proteasome; Alzheimer' s Disease; Antibodies; Antibody Diversity; Antibody Formation; Architecture; B-Lymphocytes; Back; Binding; Binding Sites; Biochemical; Calnexin; Cell Culture Techniques; Cell Lineage; Cell physiology; Cell surface; Cells; Complex; Cystic Fibrosis; Cytosol; Development; Disease; Elements; Endoplasmic Reticulum; Ensure; Environment; Evaluation; Family member; Funding; Genetic; Genetic Transcription; Government; Guanine Nucleotide Exchange Factors; Heavy-Chain Immunoglobulins; Homologous Gene; Immune; Immune system; Immunoglobulin Isotypes; Immunoglobulins; Individual; Knockout Mice; Life; Light; Link; Lymphocyte; Measures; Membrane; Messenger RNA; Molecular Chaperones; Monitor; Mutation; Nucleotides; Pathway interactions; Patients; Persons; Plasma Cells; Play; Prion Diseases; Process; Production; Protein Binding; Proteins; Quality Control; Recruitment Activity; Role; Specificity; Splenocyte; Substrate Specificity; Syndrome; System; Testing; Tissues; Work; arm; cellular imaging; cofactor; glucose-regulated protein 170; insight; loss of function; lymphoblastoid cell line; molecular chaperone GRP78; novel; operation; plasma cell differentiation; prevent; protein complex; protein degradation; protein folding; protein misfolding; research study; response; secretory protein; success; ubiquitin-protein ligase

The differentiation of a B cell to a plasma cell represents one of the most dramatic changes in cellular architecture known. The massive increase in the secretory pathway that occurs is necessary to allow the plasma cell to become a factory dedicated to the synthesis, assembly and transport of immunoglobulin (Ig) molecules. The production of these heteromeric proteins in the endoplasmic reticulum (ER) is both aided and monitored by a group of resident ER proteins known as molecular chaperones. If the Ig protein fails to mature properly, it is identified and transferred back across the ER membrane to the cytosol for degradation by the 26S proteasome. In addition to the massive number of Ig molecules that are processed each minute in a plasma cell, the mechanisms for generating antibody diversity put further demands on ER quality control systems in B lineage cells. Thus it is not surprising that many components of this system were first identified in immune cells, and it is possible that unique elements of the ER quality control apparatus could exist in these cells. To better define the mechanisms governing the biosynthesis of Ig proteins, we continue our studies on the molecular chaperone BiP, which binds to free Ig heavy chains (HC) and prevents their transport until they assemble with light chains (LC). We hypothesize that BiP and its co-factors work together in a carefully orchestrated fashion to aid Ig assembly, monitor the success of this operation, and finally to target improperly folded or assembled Ig subunits for degradation. Furthermore, we hypothesize that distinct regions of the ER exist to accommodate the seemingly antagonistic functions of protein folding and degradation and that individual ERdj family members allow BiP to participate in these different functions. In the present proposal we wish to further delineate critical checkpoints in Ig assembly and determine the mechanisms by which they are executed. To do so, we will determine the function of three ER localized DnaJ homologues in Ig folding, assembly and turnover, define the specificity of nucleotide exchange factors in releasing BiP from unfolded proteins, and finally delineate mechanisms used to identify unassembled Ig molecules and target them for degradation.

B细胞与浆细胞的分化代表了细胞中最大的变化之一 已知的建筑。需要发生的分泌途径的巨大增加是必要的 血浆细胞成为专门用于免疫球蛋白（IG）合成，组装和运输的工厂 分子。这些异质蛋白在内质网（ER）中的产生均得到辅助和 由一组被称为分子伴侣的常驻ER蛋白监测。如果Ig蛋白无法成熟 正确地，将其识别并在ER膜上转移到细胞质中，以通过 26S蛋白酶体。除了每分钟在A中处理的大量IG分子外 等离子体细胞，产生抗体多样性的机制对ER质量控制提出了进一步的需求 B谱系细胞中的系统。因此，首先确定了该系统的许多组件，这并不奇怪 免疫细胞，ER质量控制设备的独特元素可能存在 细胞。为了更好地定义管理IG蛋白生物合成的机制，我们继续研究 分子伴侣BIP结合了自由Ig重链（HC），并防止其运输直到它们 用轻链组装（LC）。我们假设Bip及其副因素在仔细的 精心策划的时尚以帮助IG组装，监视此操作的成功，最后针对不当的目标 折叠或组装的Ig亚基以降解。此外，我们假设ER的不同区域 存在以适应蛋白质折叠和降解的看似对立的功能 单个ERDJ家庭成员允许BIP参与这些不同的功能。在本提案中，我们 希望进一步描述IG组装中的关键检查点，并确定它们的机制 执行。为此，我们将确定IG折叠中三个ER局部DNAJ同源物的功能， 组装和周转，定义核苷酸交换因子的特异性，从展开的bip释放BIP 蛋白质，最后描述用于识别未组装的Ig分子的机制，并将其靶向 降解。