Regulation of emergency hematopoiesis by the ubiquitin-proteasome system

项目摘要 对全身感染和组织损伤的反应需要造血干细胞的快速适应。 骨髓中的干细胞(HSCs)，增殖并将其分化为髓系。 人们对了解触发这种紧急造血的信号产生了浓厚的兴趣 程序。然而，终止造血干细胞这种反应并恢复组织的机制 动态平衡仍然未知。蛋白酶体抑制剂Bortezomib和E3泛素的临床成功 用于治疗血液病的连接酶胶使泛素途径成为真正的靶点 癌症治疗学。因此，定义新的E3连接酶在骨髓中的功能并研究它们的 在正常和紧急造血中的特殊作用可以导致新的治疗干预措施。我们有 证明E3泛素连接酶SPOP抑制HSCs的炎症激活。在缺席时 在SPOP中，全身性炎症以未解决的方式进行，HSCs的持续反应 结果导致一种致命的表型，使人联想到高炎症综合征。我们的蛋白质组学/生物化学 研究表明，SPOP通过靶向MyD88信号转导通路来抑制炎症 依赖蛋白酶体的降解。MyD88积聚与炎症刺激相结合导致 对肌小体的形成，IRAK4激酶的过度磷酸化和一些 转录因子途径(核因子-kB、Jun、PU.1、CEBPB)。该提案界定：(A)抄本和 急诊造血启动和终止过程中染色质景观的变化 骨髓HSC和祖细胞，(B)肌小体组装、信号传递和终止的作用 在紧急造血和基因调控中的作用以及(C)myddosome组装和 终止。这项赠款提案的发现将揭示HSC的内在机制 在紧急造血后重建内环境平衡。

Project Summary The response to systemic infection and tissue injury requires the rapid adaptation of hematopoietic stem cells (HSCs) in the bone marrow, which proliferate and divert their differentiation towards the myeloid lineage. Significant interest has emerged in understanding the signals that trigger this emergency hematopoietic program. However, the mechanisms that terminate this response of the HSCs and restore tissue homeostasis remain unknown. The clinical success of proteasome inhibitors, bortezomib, and E3 ubiquitin ligase glues for the treatment of hematologic diseases has made the Ubiquitin pathway a bona fide target for cancer therapeutics. Thus, defining how novel E3 ligases function in the bone marrow and investigating their specific roles in normal and emergency hematopoiesis can lead to novel therapeutic interventions. We have demonstrated that the E3 ubiquitin ligase Spop restrains the inflammatory activation of HSCs. In the absence of Spop, systemic inflammation proceeds in an unresolved manner and the sustained response in the HSCs results in a lethal phenotype reminiscent of hyper-inflammatory syndrome. Our proteomic/biochemical studies demonstrated that Spop restricts inflammation by targeting the signal transducer Myd88 for proteasome-dependent degradation. Myd88 accumulation in conjunction with an inflammatory stimulus leads to Myddosome formation, the hyper-phosphorylation of the Irak4 kinase and activation of a number of transcription factor pathways (NF-kB, Jun, Pu.1, Cebpb). This proposal defines: (a) the transcriptional and chromatin landscape changes imposed during initiation and termination of emergency hematopoiesis in the bone marrow HSC and progenitor cells, (b) the role of the myddosome assembly, signaling and termination in emergency hematopoiesis and gene regulation and (c) the structural details of myddosome assembly and termination. The findings of this grant proposal will uncover HSC-intrinsic mechanisms essential for reestablishing homeostasis following emergency hematopoiesis.