Understanding the mechanisms that govern Bst-1 induction upon caloric restriction

了解热量限制下控制 Bst-1 诱导的机制

• 批准号: 8456245
• 负责人: Shuyu Wang
• 金额: $ 4.22万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-12-01 至 2014-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8456245
• 关键词: Acute; Aging; Aging-Related Process; Binding; Biochemical; Biological Assay; Blood Circulation; Caloric Restriction; Candidate Disease Gene; Categories; Cells; Chromatin; Chronic; Coculture Techniques; Complex; Computer Simulation; Culture Media; Data; Diabetes Mellitus; Diet; Disease; Energy Intake; Engineering; Environment; Epigenetic Process; Event; Fluorescence Microscopy; Gene Expression; Gene Expression Profile; Genes; Goals; Growth; Histocompatibility Testing; Intervention; Intestines; Light; Link; Longevity; Malignant Neoplasms; Mediating; Mediator of activation protein; Messenger RNA; Metabolic; Metabolism; Methods; Molecular; Mus; Nutrient; Nutritional; Organism; Organoids; Paneth Cells; Pathway interactions; Phenotype; Phosphorylation; Physiological; Population; Regulation; Role; Signal Transduction; Sirolimus; Small Interfering RNA; Specificity; Stem cells; Supplementation; System; Testing; Tissues; Tube; Up-Regulation; base; cell type; cellular transduction; combat; functional decline; genetic manipulation; human FRAP1 protein; in vivo; insight; intestinal crypt; mTOR inhibition; novel; promoter; response; self-renewal; small hairpin RNA; small molecule; transcription factor; tumor growth

DESCRIPTION (provided by applicant): The mTOR pathway is a major signaling hub that coordinates growth and metabolism in response to the nutritional state of the organism. Its dysregulation has been implicated in a broad spectrum of common disease states, including cancer, diabetes, and aging. Interestingly, two interventions that suppress mTOR signaling - rapamycin and caloric restriction (a reduction in caloric intake to a fraction of ad libitum levels - have both been robustly linked to diminished tumor growth and augmented lifespan in mice. Little is known, however, about the molecular mechanisms responsible for these physiological and pathophysiological phenomena. Organismal aging is thought to be due, in part, to the progressive functional decline in stem cell compartments. We have chosen to focus on the intestine, and, in particular, on understanding the effects of caloric restriction (CR) and mTOR inhibition on intestinal stem cells (ISCs) and their niche. We find that CR strongly augments the self-renewal capacity of ISCs through a non-cell autonomous mechanism requiring the inhibition of mTORC1 and the upregulation of Bst1 in Paneth cells. Surprisingly, Paneth cells transitioned from CR conditions to nutrient-rich conditions maintained the CR phenotypes for at least 3 days, suggesting that the CR state itself is not simply the consequence of an acute signaling event. The goal of this project is to understand how CR, via mTORC1 inhibition, upregulates Bst1 expression, a necessary and sufficient event for the CR phenotype. One hypothesis we are entertaining is that mTORC1 inhibition stably modulates Bst1 expression by remodeling the epigenome. We are using computational and experimental methods in tandem to identify candidate genes that may mediate the signaling cascade between mTORC1 and the Bst1 gene. We will then systematically test the necessity and sufficiency of each candidate gene, first in test tube-based organoid co-culture and then in mice engineered to afford genetic manipulations specifically in the Paneth cell population. A clearer understanding of this pathway may shed light on new ways of mimicking the beneficial CR state. To determine the mechanisms by which long-term CR regulates gene expression, I propose the following specific aims: I: Elucidate the molecular mechanisms that modulate Bst1 mRNA levels in response to CR or mTORC1 inhibition by rapamycin. II: Determine the role(s) of the regulatory factor(s) identified in Specifc Aim I on the in vivo effects of CR and rapamycin on ISC self-renewal. PUBLIC HEALTH RELEVANCE: This project will shed light on how the chronic inhibition of mTORC1, a master regulator of growth and viability, alters the gene expression profile of intestinal Paneth niche cells. Paneth niche cells transduce signals from the nutrient environment to neighboring intestinal stem cells, thereby augmenting the latter's capacity for self- renewal. Elucidation of these mechanisms may lend insights on how mTOR controls the aging process and may further reveal novel targets to combat aging.

描述（由申请人提供）：mTOR 通路是一个主要的信号传导中枢，可根据生物体的营养状态协调生长和代谢。它的失调与多种常见疾病有关，包括癌症、糖尿病和衰老。有趣的是，两种抑制 mTOR 信号传导的干预措施——雷帕霉素和热量限制（将热量摄入减少到随意水平的一小部分）都与小鼠肿瘤生长的减少和寿命的延长密切相关。然而，人们对这些生理和病理生理现象的分子机制知之甚少。生物体衰老被认为部分是由于 干细胞区室的功能进行性衰退。我们选择关注肠道，特别是了解热量限制 (CR) 和 mTOR 抑制对肠道干细胞 (ISC) 及其生态位的影响。我们发现 CR 通过非细胞自主机制强烈增强 ISC 的自我更新能力，这种机制需要抑制 mTORC1 和上调 Paneth 中的 Bst1 细胞。令人惊讶的是，潘氏细胞从 CR 条件转变为营养丰富的条件，并保持 CR 表型至少 3 天，这表明 CR 状态本身不仅仅是急性信号传导事件的结果。 该项目的目标是了解 CR 如何通过 mTORC1 抑制上调 Bst1 表达，这是 CR 表型的必要且充分的事件。我们感兴趣的一个假设是 mTORC1 抑制 通过重塑表观基因组稳定调节 Bst1 表达。我们正在同时使用计算和实验方法来识别可能介导 mTORC1 和 Bst1 基因之间信号级联的候选基因。然后，我们将系统地测试每个候选基因的必要性和充分性，首先在基于试管的类器官共培养中，然后在经过改造的小鼠中，专门在潘氏细胞中进行基因操作 人口。更清楚地了解这一途径可能有助于揭示模仿有益 CR 状态的新方法。为了确定长期 CR 调节基因表达的机制，我提出以下具体目标： I：阐明响应雷帕霉素 CR 或 mTORC1 抑制而调节 Bst1 mRNA 水平的分子机制。 II：确定监管因素的作用 具体目标 I 关于 CR 和雷帕霉素对 ISC 自我更新的体内影响。 公共健康相关性：该项目将揭示 mTORC1（生长和活力的主要调节因子）的长期抑制如何改变肠道潘氏利基细胞的基因表达谱。潘氏生态位细胞将信号从营养环境转导至邻近的肠道干细胞，从而增强后者的自我更新能力。对这些机制的阐明可能有助于了解 mTOR 如何控制衰老过程，并可能进一步揭示对抗衰老的新靶标。