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 细胞向浆细胞的分化是细胞中最显着的变化之一。 建筑已知。分泌途径的大量增加对于允许 浆细胞成为致力于合成、组装和运输免疫球蛋白（Ig）的工厂 分子。内质网 (ER) 中这些异聚蛋白的产生既是辅助的，也是 由一组称为分子伴侣的驻留 ER 蛋白进行监测。如果 Ig 蛋白未能成熟 正确地，它被识别并穿过 ER 膜转移回细胞质，并被 26S蛋白酶体。除了每分钟处理的大量 Ig 分子外， 浆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要求 B 谱系细胞中的系统。因此，该系统的许多组件首次在 免疫细胞，并且 ER 质量控制装置的独特元件可能存在于这些细胞中 细胞。为了更好地定义控制 Ig 蛋白生物合成的机制，我们继续研究 分子伴侣 BiP，它与游离 Ig 重链 (HC) 结合并阻止其运输，直到它们 用轻链（LC）组装。我们假设 BiP 及其辅助因子以一种仔细的方式共同作用。 精心策划的时尚来帮助 Ig 组装，监控该操作的成功，并最终瞄准不正确的目标 折叠或组装 Ig 亚基以进行降解。此外，我们假设 ER 的不同区域 存在是为了适应蛋白质折叠和降解的看似对立的功能，并且 个别 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 被执行。为此，我们将确定三个 ER 定位的 DnaJ 同源物在 Ig 折叠中的功能， 组装和周转，定义核苷酸交换因子从未折叠状态释放 BiP 的特异性 蛋白质，最后描述用于识别未组装的 Ig 分子并将其靶向的机制 降解。