Targeting Daxx-mediated complex for autoimmune diseases

靶向 Daxx 介导的复合物治疗自身免疫性疾病

• 批准号: 8493108
• 负责人: JIANKE ZHANG
• 金额: $ 18.21万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8493108
• 关键词: Ablation; Affect; Apoptosis; Apoptotic; Autoimmune Diseases; Autoimmune Process; Binding; Binding Proteins; CD95 Antigens; Cell Death; Cell Nucleus; Cell Proliferation; Cells; Cessation of life; Complex; Cytoplasm; Data; Death Domain; Defect; Development; Disease; Disease model; Embryo; Family; Family member; Genes; Genetic; Germ Cells; Homeostasis; Human; Immune; Immune system; In Vitro; Knockout Mice; Lead; Lymphocyte; Lymphoproliferative Disorders; MDM2 gene; Mature T-Lymphocyte; Mediating; Mediator of activation protein; Membrane; Modeling; Molecular; Mus; Mutant Strains Mice; Mutation; Nature; Necrosis; Oncogene Proteins; Pathway interactions; Play; Prevention Measures; Process; Protein Binding; Protein p53; Proteins; RIPK3 gene; Recruitment Activity; Resistance; Role; Signal Transduction; Stimulus; T-Cell Receptor; T-Lymphocyte; TNFRSF6 gene; Testing; Therapeutic; Transactivation; Tumor Cell Line; Yeasts; apoptosis in lymphocytes; autoimmune lymphoproliferative syndrome; caspase-10; caspase-8; design; in vivo; insight; knock-down; member; mutant; novel; public health relevance; response; yeast two hybrid system

DESCRIPTION (provided by applicant): The focus of this project is to investigate the molecular mechanism involved in a novel function of Daxx, which can be explored in developing strategies for autoimmune diseases. The multifunctional protein Daxx was originally identified as a potential mediator of Fas-induced apoptosis. Mutations in the Fas gene lead to an autoimmune-lymphoproliferative syndrome (ALPS), due to impaired apoptosis in lymphocytes and other immune cells. While Fas-induced cell death is initiated at the membrane, Daxx is present not only in the cytoplasm but also in the nucleus. Many potential Daxx-binding proteins have been identified, including the tumor suppressor p53 family members as well as the oncoprotein MDM2. However, the in vivo function of Daxx is poorly defined, as deletion of Daxx in germ cells leads to early embryonic lethality. During lymphocyte development and function, cell proliferation, survival and death are tightly regulated by various genes. Dysregulation in these processes may lead to autoimmune diseases. We and others identified the Fas- associated death domain (FADD) protein as a critical adaptor for Fas to recruit and activate the initiator caspase 8 during apoptotic signaling. Interestingly, FADD deficiency also has an embryonic lethal effect. Whereas lymphocytes in lymphocyte-specific FADD-deficient mice are resistant to Fas-induced apoptosis, these conditional FADD knockout mice do not develop autoimmune diseases, unlike that in Fas mutant mice. This paradox is explained by our recent study which reveals a potent, RIP1-dependent necrotic pathway unleashed in the absence of FADD. Our preliminary data show that deletion of RIP3, a member of the RIP1 family, restores normal development in FADD-deficient mice. Importantly, the resulting RIP3-/- FADD-/- double knockout (DKO) mice develop progressive autoimmune diseases, similar to that in Fas mutant mice. These data contrast a model suggesting that Daxx promotes FADD-independent apoptosis in the Fas pathway. Indeed, our preliminary data shows that Daxx-deficient T cells from conditional Daxx knockout mice have no defect in Fas-induced apoptosis. Unexpectedly, Daxx-/- T cells are hypersensitive to activation-induced cell death (AICD) when stimulated through the T cell antigen receptor (TCR). We hypothesize that in primary lymphocytes, there is an additional death pathway which is independent of the Fas-FADD-Caspase 8 axis, and is suppressed by Daxx. Therefore, targeting Daxx would promote cell death and serves as a strategy for autoimmune disease therapy. However, the molecular mechanism of this novel function of Daxx in the immune system is unclear. Therefore, we propose: 1) to elucidate the cell death pathway(s) in primary lymphocytes that is inhibited by Daxx; 2) to test for the effect o genetic and pharmacological ablation of Daxx function on suppressing autoimmune diseases. Successful completion of these specific aims will provide new insight into the mechanisms of the action by Daxx and lead to better design of measures for prevention and treatment of autoimmune and related diseases.

描述（由申请人提供）：该项目的重点是研究DAXX新功能所涉及的分子机制，可以在制定自身免疫性疾病的策略中探索。多功能蛋白DAXX最初被鉴定为FAS诱导凋亡的潜在介体。由于淋巴细胞和其他免疫细胞的凋亡受损，FAS基因中的突变导致自身免疫 - 淋巴增生综合征（ALP）。尽管FAS诱导的细胞死亡是在膜上启动的，但DAXX不仅存在于细胞质中，而且存在于细胞核中。已经确定了许多潜在的DAXX结合蛋白，包括抑制肿瘤p53家族成员以及癌蛋白MDM2。然而，DAXX的体内功能的定义很差，因为DAXX在生殖细胞中的缺失导致早期胚胎致死性。在淋巴细胞发育和功能期间，细胞增殖，存活和死亡受各种基因的严格调节。这些过程中的失调可能导致自身免疫性疾病。我们和其他人确定了FAS相关的死亡结构域（FADD）蛋白是FAS在凋亡信号传导过程中募集和激活引发剂caspase 8的关键适配器。有趣的是，FADD缺乏症也具有胚胎致死作用。尽管淋巴细胞特异性FADD缺陷小鼠的淋巴细胞对FAS诱导的凋亡具有抗性，但这些条件FADD敲除小鼠不会患上自身免疫性疾病，与FAS突变小鼠不同。我们最近的研究揭示了在没有FADD的情况下释放出的有效的RIP1依赖性坏死途径来解释这一悖论。我们的初步数据表明，RIP1家族成员RIP3的删除恢复了FADD缺陷小鼠的正常发育。重要的是，所得的RIP3 - / - FADD - / - 双敲除（DKO）小鼠患有渐进性自身免疫性疾病，类似于FAS突变小鼠中的疾病。这些数据对比了一个模型，表明DAXX促进了FAS途径中非FADD非依赖性的凋亡。实际上，我们的初步数据表明，有条件DAXX敲除小鼠的DAXX缺陷T细胞在FAS诱导的凋亡中没有缺陷。出乎意料的是，当通过T细胞抗原受体（TCR）刺激时，DAXX - / - T细胞对激活诱导的细胞死亡（AICD）非常敏感。我们假设在原发性淋巴细胞中，还有一个额外的死亡途径，它与FAS-FADD-Caspase 8轴无关，并被DAXX抑制。因此，靶向DAXX将促进细胞死亡，并作为自身免疫性疾病疗法的策略。但是，DAXX在免疫系统中这种新功能的分子机制尚不清楚。因此，我们提出：1）阐明DAXX抑制的原代淋巴细胞中的细胞死亡途径； 2）测试DAXX功能对抑制自身免疫性疾病的遗传和药理消融的影响。这些特定目标的成功完成将为DAXX的动作机制提供新的见解，并为预防和治疗自身免疫和相关疾病的预防和治疗提供更好的设计。