DEK Regulation of Hematopoietic Stem Cell Renewal, Fate, and Hematopoiesis

 描述(由申请人提供)：阐明控制造血干细胞更新和谱系分化的机制对于促进应激和造血细胞移植后的造血恢复至关重要。最近，我们发现具有独特生物化学特性的DEK蛋白通过与CXCR2趋化因子受体的相互作用，促进造血干细胞(HSC)的体外扩增和植入，同时调节造血祖细胞(HPC)的增殖和周期。虽然DEK与多种核内活动有关，但我们最近发现，这种没有酶活性的非组蛋白蛋白可以调节全球异染色质的完整性，从而调节基因表达。有趣的是，除了其核内功能外，我们还发现DEK可以由单核细胞分泌并由凋亡的T细胞释放，并通过涉及CXCR2的机制作为中性粒细胞以及HSCs和HPC的趋化因子，该机制也至少介导了DEK对HPC循环的部分影响。值得注意的是，我们现在还发现DEK的核内和细胞外功能可以统一，因为细胞外的DEK可以被几种不同类型的造血细胞和其他细胞以生物活性的形式摄取，调节染色质结构和DNA修复。因此，DEK是一种调节造血的核蛋白，参与了一个非常不寻常的循环，涉及分泌、受体参与、摄取以及随后对异染色质生物学、基因表达和HSC/HPC功能的调节。值得注意的是，这个环在体内是活跃的，因为皮下注射重组DEK会导致小鼠HSC表型显著增加，HPC数量减少，细胞周期减少。因此，我们建议使用多学科的方法来检验这一假说，即这个涉及DEK的核内/细胞外环路通过影响染色质平衡和CXCR2介导的信号在造血生长和分化以及干细胞植入中发挥重要作用。利用小鼠和人类造血细胞的未成熟亚群、小鼠体内稳态和应激造血的模型、细胞信号研究、表观遗传学分析以及全基因组染色质结构和基因表达的研究，我们将进一步阐明DEK调节HSC增殖、存活、自我更新和分化之间的命运决定并促进HSC体内植入的机制。拟议的实验将阐明DEK是如何通过CXCR2信号和非常不寻常的细胞外/细胞内染色质环影响HSC命运决定和造血的。这将在二肽基肽酶(DPP)4修饰DEK的背景下进行，以及额外的生理性氧休克/应激对体内和体外DEK功能的影响。这些研究有可能产生治疗造血障碍和其他需要造血细胞移植的疾病的新方法。

 DESCRIPTION (provided by applicant): Elucidating the mechanisms by which hematopoietic stem cell renewal and lineage differentiation are controlled is crucial to improving hematopoietic recovery after stress and hematopoietic cell transplantation. Recently, we discovered that the biochemically distinct and unique DEK protein is a factor that enhances ex-vivo expansion of hematopoietic stem cells (HSCs) and HSC engraftment, while regulating hematopoietic progenitor cell (HPC) proliferation and cycling though its interaction with the CXCR2 chemokine receptor. While DEK has been implicated in multiple intranuclear activities, we have recently found that this non-histone protein with no enzymatic activity modulates global heterochromatin integrity and hence gene expression. Interestingly, in addition to its intranuclear functions, we have found that DEK can be secreted by monocytic cells and released by apoptotic T cells, and act as a chemotactic factor for neutrophils, as well as for HSCs and HPCs, through a mechanism involving CXCR2, which also mediates at least some of DEK's effects on the cycling of HPCs. Remarkably, we have now also discovered that the intranuclear and extracellular functions of DEK can be unified, as extracellular DEK can be taken up by several different types of hematopoietic and other cells in a bioactive form that modulates chromatin structure and DNA repair. Thus, DEK is a nuclear protein that regulates hematopoiesis and participates in a highly unusual loop involving secretion, receptor engagement, uptake, and subsequent modulation of heterochromatin biology, gene expression and HSC/HPC functions. Strikingly, this loop is active in vivo, as subcutaneous administration of recombinant DEK to mice leads to significant increases in phenotyped HSCs and lower numbers and decreased cycling of HPCs. Therefore, we propose to use a multidisciplinary approach to test the hypothesis that this intranuclear/extracellular loop involving DEK plays a significant role in hematopoietic growth and differentiation and stem engraftment by affecting chromatin balance and CXCR2-mediated signaling. Using immature subsets of mouse and human hematopoietic cells, mouse models of homeostasis and stressed hematopoiesis, cell signaling studies, epigenetic analysis, and genome-wide studies of chromatin structure and gene expression, we will further delineate the mechanisms by which DEK modulates the fate decisions between HSC proliferation, survival, self-renewal and differentiation and promotes HSC engraftment in vivo. The proposed experiments will elucidate how DEK works through CXCR2 signaling and the highly unusual extracellular/intracellular chromatin loop to affect HSC fate decisions and hematopoiesis. This will be done in context of Dipeptidylpeptidase (DPP) 4 modification of DEK, and the influence of extra physiologic oxygen shock/stress on DEK functions in vivo and in vitro. These studies have the potential to generate new approaches to the treatment of hematopoietic disorders and other diseases in which hematopoietic cell transplantation is required.