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

基本信息

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
项目类别：
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

项目摘要

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 的新功能所涉及的分子机制，这可以在开发自身免疫性疾病的策略中进行探索。多功能蛋白 Daxx 最初被鉴定为 Fas 诱导细胞凋亡的潜在介质。 Fas 基因突变会导致淋巴细胞和其他免疫细胞凋亡受损，从而导致自身免疫性淋巴增殖综合征 (ALPS)。 Fas 诱导的细胞死亡是从细胞膜开始的，而 Daxx 不仅存在于细胞质中，还存在于细胞核中。许多潜在的 Daxx 结合蛋白已被鉴定，包括肿瘤抑制因子 p53 家族成员以及癌蛋白 MDM2。然而，Daxx 的体内功能尚不清楚，因为生殖细胞中 Daxx 的缺失会导致早期胚胎死亡。在淋巴细胞的发育和功能过程中，细胞增殖、存活和死亡受到各种基因的严格调控。这些过程的失调可能会导致自身免疫性疾病。我们和其他人发现 Fas 相关死亡结构域 (FADD) 蛋白是 Fas 在细胞凋亡信号传导过程中招募和激活起始 caspase 8 的关键适配器。有趣的是，FADD 缺陷也具有胚胎致死作用。尽管淋巴细胞特异性 FADD 缺陷小鼠中的淋巴细胞能够抵抗 Fas 诱导的细胞凋亡，但这些条件性 FADD 敲除小鼠不会患上自身免疫性疾病，这与 Fas 突变小鼠不同。我们最近的研究解释了这一悖论，该研究揭示了在 FADD 不存在的情况下释放的有效的 RIP1 依赖性坏死途径。我们的初步数据表明，删除 RIP1 家族成员 RIP3 可恢复 FADD 缺陷小鼠的正常发育。重要的是，由此产生的 RIP3-/- FADD-/- 双敲除 (DKO) 小鼠会出现进行性自身免疫性疾病，与 Fas 突变小鼠相似。这些数据与模型形成对比，表明 Daxx 促进 Fas 途径中不依赖于 FADD 的细胞凋亡。事实上，我们的初步数据表明，条件性 Daxx 敲除小鼠的 Daxx 缺陷 T 细胞在 Fas 诱导的细胞凋亡中没有缺陷。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) 高度敏感。我们假设在原代淋巴细胞中，存在一条独立于 Fas-FADD-Caspase 8 轴的额外死亡途径，并被 Daxx 抑制。因此，靶向 Daxx 将促进细胞死亡，并可作为自身免疫性疾病治疗的策略。然而，Daxx 在免疫系统中的这种新功能的分子机制尚不清楚。因此，我们建议：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功能的遗传和药理消除对抑制自身免疫性疾病的影响。这些具体目标的成功实现将为 Daxx 的作用机制提供新的见解，并导致更好地设计预防和治疗自身免疫及相关疾病的措施。