Mechanisms of tunable posttranslational control of T-cell homeostasis and tolerance

总结 在严格监管的过程中产生和维持多样性和自我宽容的池的缺陷 负责免疫的T细胞导致非常衰弱的人类自身免疫和免疫缺陷疾病。 尽管几十年来不断发展的治疗方法，自身免疫性疾病仍然是死亡的主要原因之一 特别是在美国，有超过2300万人受到影响的妇女和儿童， 每年给经济带来超过1000亿美元的损失由于T细胞发育和体内平衡失调 经常是自身免疫性疾病状态的基础，开发针对这些疾病的更有效的治疗方法， 疾病将受益于解决主要的知识差距的细胞因子和途径，使T- 细胞内稳态例如，蛋白酶体依赖性机制控制蛋白质的活性， 介导T细胞的存活，代谢和信号转导，但如何从T细胞的关键稳态信号 受体（TCR）和白细胞介素（IL）-7与泛素化机制的偶联仍然知之甚少。我们 最近发现，带电多泡体蛋白-5（CHMP 5）作为一种“适配器”， T细胞的发展，以招募去泛素化酶，促进客户蛋白质的稳定性。的新证据 我们的实验室表明，CHMP 5的表达受到TCR和IL-7信号的严格控制， 外周T细胞CHMP 5的缺失损害了它们的稳态，并与完全渗透有关。 多器官自身免疫性疾病因此，利用动物模型可以精确跟踪CHMP 5 突变的T细胞，在这个建议中，我们将测试的假设，CHMP 5核的关键翻译后 稳态信号整合到T细胞存活的蛋白质介质稳定性的节点 和耐受性，将其定位为调节疾病中T细胞的可调和潜在靶点。在Aim I中， 我们将确定CHMP 5如何控制能量代谢和促生存蛋白，这些蛋白是外周T细胞的组成部分， 生存和功能。在目标2中，我们将阐明TCR和CD 44介导的差异CHMP 5稳定化的机制。 IL-7信号，特别是它们诱导稳定CHMP 5蛋白的丝氨酸磷酸化的能力。 此外，由于去泛素化酶USP 8的缺失耗尽了T细胞中的CHMP 5蛋白，我们将定义T细胞中的CHMP 5蛋白。 USP 8-CHMP 5相互作用的基础。破坏这种相互作用可以潜在地用于治疗 耗尽T细胞CHMP 5。到目前为止，TCR信号阈值如何转化为胸腺细胞阳性和阴性， 选择仍不清楚。因此，基于CHMP 5被低亲和力TCR配体稳定，但 在目标3中，我们将测试差异CHMP 5蛋白被高亲和力信号降解的新范例， 稳定是胸腺细胞建立中枢耐受的机制。这些研究将有助于了解 长期存在的T细胞稳态问题，并有可能发现新的翻译后 可以利用这些弱点来治疗性地调节疾病中的T细胞，特别是调节异常 CHMP 5基因在人类9p13.3染色体区域的定位与多种组织疾病有关。

Summary Defects in the stringently regulated processes that generate and maintain the diverse and self-tolerant pool of T-cells responsible for immunity cause very debilitating human autoimmune and immunodeficiency diseases. Despite decades of evolving therapies, autoimmune diseases still rank among the leading causes of death especially in women and children in the US alone where more than 23 million people are afflicted, at a cost that exceeds $100 billion annually to the economy. As dysfunctional T-cell development and homeostasis frequently underlie autoimmune disease states, development of more effective therapies against these diseases will benefit from resolving major knowledge gaps of the cellular factors and pathways that enable T- cell homeostasis. For example, proteasome-dependent mechanisms control the activity of proteins that mediate survival, metabolism and signal transduction in T-cells but how key homeostatic signals from the T-cell receptor (TCR) and interleukin (IL)-7 are coupled to the ubiquitination machinery is still poorly understood. We recently discovered that the Charged Multivesicular Body Protein-5 (CHMP5) functions as an “adaptor” during T-cell development to recruit deubiquitinating enzymes that promote client protein stability. New evidence from our laboratory shows that CHMP5 expression is stringently controlled by TCR and IL-7 signals, and that deletion of CHMP5 in peripheral T-cells impaired their homeostasis and was associated with a fully penetrant multi-organ autoimmune condition. Thus, leveraging animal models that allow precise tracking of CHMP5 mutant T-cells, in this proposal we will test the hypothesis that CHMP5 nucleates a critical posttranslational node by which homeostatic signals are integrated to the stability of protein mediators of T-cell survival and tolerance, situating it as a tunable and potential target for modulating T-cells in disease. In Aim I, we will determine how CHMP5 controls energy metabolism and prosurvival proteins integral to peripheral T-cell survival and function. In Aim 2, we will elucidate the mechanism of differential CHMP5 stabilization by TCR and IL-7 signals, especially their ability to induce serine phosphorylations that stabilize CHMP5 protein. Additionally, as deletion of the deubiquitinase USP8 depletes CHMP5 proteins in T-cells, we will define the basis of the USP8-CHMP5 interaction. Disrupting this interaction can potentially be utilized to therapeutically deplete T-cell CHMP5. To date, how TCR signal thresholds are translated into thymocyte positive and negative selection remains unclear. Thus, building on evidence that CHMP5 is stabilized by low affinity TCR ligands but degraded by high affinity signals, in Aim 3, we will test the novel paradigm that differential CHMP5 protein stabilization is a thymocyte mechanism to establish central tolerance. These studies will yield insights into long-standing questions on T-cell homeostasis and have the potential to uncover new posttranslational vulnerabilities that can be exploited to therapeutically modulate T-cells in disease especially as dysregulation of the human 9p13.3 chromosomal region location of CHMP5 gene is linked with diseases in multiple tissues.