Protein homeostasis in hematopoietic stem cells

造血干细胞中的蛋白质稳态

• 批准号: 10660341
• 负责人: Robert A.J. Signer
• 金额: $ 23.7万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10660341
• 关键词: Adult; Age; Aging; Anemia; Autophagocytosis; BAG3 gene; Biogenesis; Blood; Blood Cells; Bone Marrow; Bone marrow failure; Cell Differentiation process; Cell Maintenance; Cells; Data; Defect; Degradation Pathway; Disease; Elderly; Exhibits; Functional disorder; Gene Expression; Genetic; Goals; Hematological Disease; Hematopoiesis; Hematopoietic Neoplasms; Hematopoietic stem cells; Human; Immune; Immunity; Impairment; Inclusion Bodies; Injury; Knockout Mice; Lead; Life; Longevity; Malignant - descriptor; Malignant Neoplasms; Molecular Chaperones; Mus; Natural regeneration; Non-Malignant; Outcomes Research; Pathology; Pathway interactions; Proliferating; Protein Biosynthesis; Resources; Stress; System; TAL1 gene; Testing; Tissues; Ubiquitin; age related; biological adaptation to stress; fitness; fluorescence imaging; healthspan; hematopoietic stem cell aging; hematopoietic stem cell quiescence; hematopoietic stem cell self-renewal; in vivo; leukemia; misfolded protein; mouse model; multicatalytic endopeptidase complex; preservation; prevent; progenitor; programs; protein aggregation; protein degradation; proteostasis; proteotoxicity; regenerative; response; self-renewal; sensor; stem cell function; stem cells

ABSTRACT Hematopoietic stem cells (HSCs) regenerate blood and immune cells throughout life. Unfortunately, HSC function declines with age. Age-related defects in HSCs lead to anemia, impaired immunity, bone marrow failure and cancer. Thus, understanding mechanisms that contribute to HSC aging is critical for developing strategies to enhance regeneration and tissue function in older adults. Protein homeostasis (proteostasis) dysfunction contributes to several age-associated pathologies, but diminished proteostasis has not been examined as a mechanism of HSC aging. We recently discovered that HSCs are particularly dependent on proteostasis to preserve their self-renewal capacity. However, misfolded proteins arise in HSCs and therefore must be eliminated to preserve HSC fitness. Canonically, the proteasome serves as the primary pathway for degradation of misfolded proteins, but we found that proteasome activity is low within HSCs. This raises a fundamental paradox: if HSCs are highly dependent on proteostasis, why do they have such limited proteasome capacity to degrade misfolded proteins? In preliminary studies, we found that mouse and human HSCs preferentially express the co-chaperone Bag3, which can promote delivery of misfolded proteins to aggresomes. Aggresomes are inclusion bodies containing misfolded and aggregated proteins that typically form in response to stress and are substrates for a selective form of autophagy (aggrephagy). We determined that HSCs form aggresomes, even under steady state conditions, and they depend on autophagy to degrade protein aggregates in vivo. Furthermore, we generated data demonstrating that protein aggregates accumulate in aging HSCs and that old adult HSCs activate Hsf1, key proteostasis sensor that helps preserve HSC fitness. Based on these data, our central hypothesis is that HSCs preferentially shuttle misfolded proteins to aggresomes and depend on aggrephagy to maintain proteostasis, fitness and longevity. Furthermore, we propose that accumulation of aggregated proteins contributes to age-related declines in HSC function. In Aim 1, we will test if mouse and human HSCs preferentially form aggresomes. Using conditional Bag3 knockout mice, we will test if disrupting transport of misfolded proteins to aggresomes impairs HSC function, proteostasis and aging. In Aim 2, we will use genetic mouse models to express disease-associated protein aggregates in HSCs to test the effects of protein aggregation on HSC function. We will also determine if aggrephagy regulates HSC fitness, protein synthesis and quiescence. In Aim 3, we will quantify protein aggregates in aging mouse and human HSCs, and test if protein aggregation induces Hsf1 activation. Finally, we will test if enhancing Hsf1 activity rescues age- related declines in HSC function. Research outcomes will uncover how misfolded proteins are eliminated in HSCs and if accumulation of aggregated proteins contributes to HSC aging. These studies will identify strategies to manipulate proteostasis to enhance HSC fitness and delay/prevent hematological disease in older adults.

抽象的 造血干细胞（HSC）一生都会再生血液和免疫细胞。不幸的是，HSC 功能随着年龄的增长而下降。 HSC中与年龄相关的缺陷导致贫血，免疫力受损，骨髓衰竭 和癌症。因此，了解有助于HSC衰老的机制对于制定策略至关重要 增强老年人的再生和组织功能。蛋白质稳态（蛋白抑制）功能障碍 有助于几种与年龄相关的病理学，但尚未将蛋白质静脉曲张降低为 HSC衰老的机制。我们最近发现，HSC特别依赖于蛋白质的 保持自己的自我更新能力。但是，HSC中出现了错误折叠的蛋白质，因此必须是 被淘汰以保持HSC健身。从规范上讲，蛋白酶体是降解的主要途径 错误折叠的蛋白质，但我们发现蛋白酶体活性在HSC中很低。这提出了基本 悖论：如果HSC高度依赖于蛋白质，为什么它们具有如此有限的蛋白酶体能力 降解错误折叠的蛋白质？在初步研究中，我们发现小鼠和人类HSC优先 表达共伴酮Bag3，可以促进将错误折叠的蛋白质递送到脂肪组中。 Aggresomes 是含有错误折叠和汇总蛋白质的包含体，这些蛋白通常是响应压力和 是选择性形式的自噬（Acgrephagy）的底物。我们确定HSC会形成aggresomes， 即使在稳态条件下，它们依靠自噬来降解体内蛋白质聚集体。 此外，我们生成的数据表明，蛋白质聚集物积累在老化的HSC中，该蛋白质聚集 成人HSC激活HSF1，有助于保留HSC健身的关键蛋白质量传感器。基于这些数据，我们 中心假设是，HSC优先将蛋白质错误折叠的蛋白质脱落到脂肪组中，并依赖 敏锐的蛋白质，健身和寿命。此外，我们建议 聚集的蛋白质有助于与年龄相关的HSC功能下降。在AIM 1中，我们将测试鼠标和是否 人类HSC优先形成细胞组。使用有条件的Bag3淘汰小鼠，我们将测试是否破坏 错误折叠的蛋白质转运到脂肪组中会损害HSC功能，蛋白质和衰老。在AIM 2中，我们将 使用遗传小鼠模型表达HSC中与疾病相关的蛋白质聚集体，以测试 HSC功能上的蛋白质聚集。我们还将确定Acgrephagy是否调节HSC健身，蛋白质 合成和静止。在AIM 3中，我们将量化老化小鼠和人HSC中的蛋白质聚集体，以及 测试蛋白质聚集是否诱导HSF1激活。最后，我们将测试是否增强HSF1活动会挽救年龄 - 相关的HSC功能下降。研究结果将发现如何消除错误折叠的蛋白 HSC和聚合蛋白的积累是否有助于HSC衰老。这些研究将确定策略 操纵蛋白质的蛋白质以增强HSC健身并延迟/预防老年人血液学疾病。