Mechanisms of a Novel Combined Immunodeficiency Caused by a Homozygous Mutation in COPG1

COPG1 纯合突变引起的新型联合免疫缺陷的机制

• 批准号: 10265627
• 负责人: RAIF SALIM GEHA
• 金额: $ 44.25万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-10 至 2023-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10265627
• 关键词: ADP-Ribosylation Factors; Age; Antibody Response; Apoptosis; Arginine; B cell differentiation; B-Lymphocytes; Bacteria; Bacterial Infections; Binding; Birth; CD4 Positive T Lymphocytes; CDC42 gene; Capsid Proteins; Cell Count; Cell Survival; Cell physiology; Cells; Coat Protein Complex I; Complex; Coupling; Cytomegalovirus; Cytosol; Data; Defect; Disease; Disease model; Encapsulated; Endoplasmic Reticulum; Ensure; Family; Fibroblasts; GTPase-Activating Proteins; Golgi Apparatus; Guanine Nucleotide Exchange Factors; Guanosine Triphosphate Phosphohydrolases; Human Herpesvirus 4; Immunity; Immunoglobulin G; Immunoglobulins; Immunologic Deficiency Syndromes; Impairment; In Vitro; Integral Membrane Protein; Interleukin-4; KDEL receptor; Link; Lung infections; Lymphocytic choriomeningitis virus; Lymphopenia; Lysine; Mediating; Membrane; Molecular Chaperones; Monomeric GTP-Binding Proteins; Mus; Mutant Strains Mice; Mutation; Outcome Study; Patients; Pharmaceutical Preparations; Pneumococcal Infections; Preclinical Testing; Predisposition; Production; Proteins; Recurrence; Retrieval; Role; Secondary to; Siblings; Side; System; T-Lymphocyte; Testing; Transcript; Treatment Efficacy; Vesicle; Viremia; Virus Diseases; chronic infection; consanguineous family; endoplasmic reticulum stress; hypogammaglobulinemia; in vivo; inhibitor/antagonist; lysyl-aspartyl-glutamyl-leucine; man; mutant; mutant mouse model; novel; preclinical efficacy; protein folding; protein transport; receptor; receptor binding; recruit; response; retrograde transport; tauroursodeoxycholic acid; trafficking; vesicle transport

We identified a biallelic K652E mutation in the γ1-COP subunit of the heptameric coat protein I (COPI) complex in 5 Omani siblings, suffering from recurrent pulmonary infections with encapsulated bacteria, CMV and EBV viremia. The four older siblings presented with severe CD4+ T cell lymphopenia and increased T cell apoptosis; the youngest had normal T cell numbers shortly after birth, but developed CMV viremia and CD4+ T cell lymphopenia at 6 mo. Coat proteins deform membranes to generate transport vesicles. They also bind to cargo proteins to properly sort them into these vesicles, and ensure their transport to specific intracellular compartments. In the early secretory system, the COPII complex transports cargo from the endoplasmic reticulum (ER) to the Golgi, while the COPI complex transports select cargo in the other direction, from the Golgi to the ER, and additionally mediates CDC42-dependent transport through the Golgi. Specific sequences on cargo proteins recognized by COPI include the di-lysine and the di-arginine motifs. Coat proteins can also bind indirectly to COPI through transmembrane proteins that act as cargo receptors. These include the KDEL receptor (KDELR), which links COPI (residing on the cytosolic side of Golgi membrane) to soluble proteins within the Golgi (lumenal side) that have a KDEL sequence. KDEL proteins are abundant ER proteins involved in protein folding (chaperones). A fraction of KDEL proteins leak from the ER, and are retrieved from the Golgi to the ER through the KDELR and COPI. Defect in this retrieval leads to the loss of ER chaperones, which has been found to induce ER stress. Preliminary data show that fibroblasts from patients, and mice homozygous for the K652E γ1-COP mutation, express the mutant protein, but demonstrate defective COPI-mediated trafficking, and that the mutation disrupts the binding of the mutant COPI complex to KDELR. Mutant mice have severe hypogammaglobulinemia and poor antibody responses. Their B cells had increased ER stress and impaired immunoglobulin (Ig) secretion that was rescued by the ER stress inhibitor TUDCA. T cells from the mutant were normal in numbers, but had increased ER stress, and displayed increased apoptosis and diminished IL-4 production following sustained activation in vitro. We propose to test the hypothesis that the γ1-COP mutation disrupts COPI-mediated trafficking causing increased ER stress that impairs B and T cell function, increases susceptibility to bacterial and viral infection, and results in CD4+ T cell lymphopenia secondary to persistent viral infection. The studies proposed will elucidate the mechanisms by which a novel monogenic defect that impairs COPI-mediated trafficking leads to CID with CD4+ T cell lymphopenia, and will test pre-clinically the therapeutic efficacy of ER stress relieving drugs in this disease.

我们确定了在肝脏外套I I（COPI）的γ1-COP亚基中的Biolelic K652E突变（COPI） 复合物中的5个阿曼兄弟姐妹，患有复发性肺部感染，封装细菌，CMV 和EBV病毒血症。具有严重CD4+ T细胞淋巴细胞减少症并增加T细胞的四个较老的兄弟姐妹 凋亡；出生后不久，最小的T细胞数正常，但患有CMV病毒血症和CD4+ T 细胞淋巴细胞减少症在6个月。 涂上蛋白质变形的机制以生成运输蔬菜。它们还将货物蛋白结合到 将它们正确分类到这些蔬菜中，并确保它们运输到特定的细胞内室。在 早期的秘书系统，COPII综合体将货物从内质网（ER）运送到高尔基 当COPI综合体从Golgi到ER的另一个方向运输选择货物，然后 另外，通过高尔基体介导Cdc42依赖性转运。货物蛋白上的特定序列 被COPI识别的包括二赖氨酸和Di-精氨酸基序。外套蛋白也可以间接结合到 通过跨膜蛋白充当货物接收器的COPI。这些包括KDEL接收器 （Kdelr），将COPI（位于高尔基膜的胞质侧）连接到内部的固体蛋白 具有KDEL序列的高尔基（Lumenal侧）。 KDEL蛋白是参与蛋白质的丰富ER蛋白 折叠（伴侣）。 KDEL蛋白的一部分从ER泄漏，并从高尔基体检索到ER 通过Kdelr和Copi。此检索中的缺陷导致ER伴侣的丧失， 发现会诱导急诊应力。 初步数据表明，来自患者的成纤维细胞和K652Eγ1-COP纯合的小鼠 突变，表达突变蛋白，但表现出copi介导的贩运缺陷，并且 突变破坏了突变型复合物与KDELR的结合。突变小鼠严重 低磁性血症和抗体反应不良。他们的B细胞增加了ER应力并受损 由ER应力抑制剂TUDCA反应的免疫球蛋白（IG）分泌。突变体的T细胞 数量正常，但ER应力增加，显示出凋亡增加并减少IL-4 体外持续激活后产生。 我们建议检验以下假设，即γ1-COP突变破坏了COPI介导的贩运 导致损害B和T细胞功能的ER应力增加，增加了对细菌的敏感性 和病毒感染，并导致继发于持续病毒感染的CD4+ T细胞淋巴细胞减少症。 提出的研究将阐明一种损害的新型单基因缺陷的机制 COPI介导的运输导致CD4+ T细胞淋巴细胞减少症CID，并将在临时治疗前测试 ER应力减轻药物在该疾病中的功效。