Regulation of hematopoietic stem cell self-renewal by GTPase activating protein signaling

 描述(由申请者提供)：本次资助申请的总体目标是了解在应激性造血过程中控制造血干细胞(HSCs)再生能力的调控途径。对于如何利用信号通路来平衡HSC的自我更新和分化以实现有效的造血再生，目前仍缺乏明确的认识。目前尚不清楚信号通路如何与其他调控元件一起控制HSC的自我更新。这种知识的缺乏阻碍了我们防止应激性造血相关的HSC再生能力下降的能力，从而限制了需要大量HSC的基于HSC的治疗的成功。我们最近发现了一个新的和临床上重要的HSC自我更新调控网络，涉及Rho GTPase信号通路和限制HSC再生能力的线粒体功能之间的串扰。我们报道了p190-B Rho GTPase激活蛋白(p190-B RhoGAP[p190-B])的基因缺失(p190-B RhoGAP[p190-B])在小鼠体内抑制Rho GTP酶活性，促进了长期的HSC植入，并防止了HSC在一系列竞争性再种群中的枯竭。P190-B基因敲除的人CD34+细胞在体外培养中保留了huCD34+的功能。单细胞分析表明，p190-B缺失促进了HSC在分裂过程中的自我更新决策而不是分化，但不影响HSC的静止和血系发育。在机制上，p190-B缺失通过限制线粒体氧化应激和随后自分泌的转化生长因子/p38MAPK应激信号通路的异常激活来促进HSC的自我更新。我们认为p190-B通过线粒体将氧化应激转化为自分泌细胞因子信号，从而指导HSC再生过程中的命运决定。目的1研究p190-B和Rho信号与自分泌转化生长因子1途径之间的联系机制。AIM 2将定义p190-B如何利用线粒体和氧化能量来调节转化生长因子？介导的肝星状细胞自我更新。AIM3将在异种移植模型中测试这些通路的药物抑制对人类CD34+适合性的影响。拟议的研究具有创新性，因为它探索了主要应激途径在未被探索的HSC生物学基本方面的作用-即HSC决定自我更新或分化，独立于成熟谱系分化或HSC静止。这项工作有望对HSC通过信号和线粒体代谢之间的串扰进行自我更新的机制产生新的见解。这项研究可能最终导致确定再生医学药物干预的新靶点。

 DESCRIPTION (provided by applicant): The overall goal of this grant application is to understand the regulatory pathways that control the regenerative capacity of hematopoietic stem cells (HSCs) during stress hematopoiesis. A clear understanding of how signaling pathways are used to balance HSC self-renewal and differentiation for efficient hematopoietic regeneration is still lacking. It is unclear how signaling pathways control HSC self-renewal in concert with other regulatory elements. This lack of knowledge has hampered our ability to prevent the decline in HSC regenerative capacity associated with stress hematopoiesis and, consequently, has limited the success of HSC-based therapies that require high numbers of HSC. We have recently discovered a novel and clinically important regulatory network of HSC self-renewal, involving crosstalk between Rho GTPase signaling pathways and mitochondria functions that limit HSC regenerative capacity. We reported that genetic deletion of p190-B Rho GTPase Activating Protein (p190-B RhoGAP [p190-B]); a suppressor of Rho GTPase activity, in mice enhanced long-term HSC engraftment and prevented HSC depletion over serial competitive repopulation. P190-B knock-down in human CD34+ cells preserved huCD34+ functions during ex vivo culture. Single cell assays revealed that p190-B loss promoted HSC self-renewal decision over differentiation during divisions; but HSC quiescence and blood lineage development were not affected. Mechanistically, p190-B loss enhanced HSC self-renewal by limiting mitochondrial oxidative stress and subsequent abnormal activation of an autocrine TGFß/p38MAPK stress signaling pathway. We propose that p190-B uses mitochondria to convert oxidative stress into autocrine cytokine signals to instruct HSC fate decision during HSC regeneration. Aim 1 will determine mechanism linking p190-B and Rho signaling to autocrine TGFß1 pathway for HSC self-renewal via. Aim 2 will define how p190-B uses mitochondria and oxidative energy to modulate TGFß - mediated HSC self-renewal. Aim3 will test the effects of pharmacological inhibition of these pathways on human CD34+ fitness in xeno-transplant models. The proposed studies are innovative because it explores the role of major stress pathways in an underexplored fundamental aspect of HSC biology - i.e. a HSC decision to self-renew or to differentiate independent on mature lineage differentiation or HSC quiescence. The work is expected to yield novel insights in mechanism of HSC self-renewal by crosstalk between signaling and mitochondrial metabolism. This study may ultimately lead to the identification of novel targets for pharmacological intervention in regenerative medicine.