Autophagy-facilitated secretion in metabolic maintenance

自噬促进代谢维持中的分泌

• 批准号: 10490364
• 负责人: Congcong He
• 金额: $ 40万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-17 至 2025-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10490364
• 关键词: 5' -AMP-activated protein kinase; Adipocytes; Adipose tissue; Attention; Autophagocytosis; Binding; Biochemical; Biochemistry; Blood Circulation; Cellular biology; Complex; Cyclic AMP-Dependent Protein Kinases; Data; Endocrine Glands; Endoplasmic Reticulum; Genes; Genetic; Goals; High Fat Diet; Homeostasis; Hormonal; Hormones; Human; Hyperactivity; Image; Insulin Resistance; Knock-in Mouse; Knockout Mice; Link; LoxP-flanked allele; Lysosomes; Maintenance; Mediating; Metabolic; Metabolic dysfunction; Metabolic syndrome; Metabolism; Molecular; Mus; Mutant Strains Mice; Mutation; Non-Insulin-Dependent Diabetes Mellitus; Pathway interactions; Pharmacology; Phenocopy; Phenotype; Phosphotransferases; Play; Process; Proteins; Proteomics; Receptor Signaling; Regulation; Research; Role; Serum; Signal Transduction; System; Testing; Tissues; Vesicle; adipokines; adiponectin; feeding; glucose tolerance; improved; insulin sensitivity; insulin sensitizing drugs; mouse model; novel; prevent; response; tool

Project Summary/Abstract The goal of this proposal is to demonstrate a novel non-degradative, non-cell autonomous, mechanism by which the autophagy machinery regulates metabolism. Although emerging evidence suggests that autophagy abnormality is implicated in metabolic dysfunction, the mechanism by which autophagy regulates insulin sensitivity is largely unknown. Autophagy is generally considered as a destruction and degradation process via lysosomes. We recently discovered a new non-degradative function regulated by a ULK1-Vps34-Becn1 autophagy machinery in adipose tissue, which may play a pivotal role in systemic AMPK activation and insulin sensitization. Adiponectin is an adipose-derived hormone (adipokine), whose reduction in circulation is strongly associated with type 2 diabetes (T2D) and metabolic syndrome. Hypoadiponectinemia caused by SNPs or mutations in the Adiponectin gene in humans has been associated with insulin resistance and T2D, and adiponectin knockout mice phenocopy the human phenotypes and develop insulin resistance. However, despite the functional importance of adiponectin, the mechanism that regulates adiponectin secretion has received little research attention and remains obscure. We found that autophagy-hyperactive mutant mice harboring an active mutation in the essential autophagy protein Becn1 (Becn1F121A knock-in mice) have improved insulin sensitivity in response to high-fat diet feeding, which is caused by factors in the circulation. To identify the Becn1-regulated, insulin-sensitizing, circulating factors, we performed a hormonal screen and identified a higher level of adiponectin in the serum of autophagy-hyperactive Becn1F121A mice. We found that on one hand, adipose- specific Becn1F121A expression is sufficient to improve systemic insulin sensitivity and increase circulating adiponectin levels; on the other hand, depleting Becn1, or inhibiting two upstream autophagy kinases, ULK1 and Vps34, reduces circulating adiponectin in mice. Using proteomic and biochemical approaches, we discovered that the exocyst component Sec6/Exoc3 is a binding partner of Becn1, and preferentially binds to the hyperactive form, Becn1F121A. Motivated by the preliminary data, we propose our overall hypothesis that a ULK1-Vps34- Becn1 autophagy axis improves insulin sensitivity by promoting adiponectin secretion via Becn1-exocyst binding in adipocytes. We term this pathway as “autophagy-facilitated secretion”. To test the hypothesis, we propose the following aims, using a combination of genetic, imaging, cell biology, biochemistry, and metabolic approaches: Aim 1 is to determine whether active Becn1 activates AMPK and improves insulin sensitivity via adiponectin signaling; Aim 2 is to determine whether a ULK1-Vps34-Becn1 autophagy axis functions in adipose tissue to non-cell autonomously regulate systemic insulin sensitivity; and Aim 3 is to demonstrate the molecular mechanism by which the Becn1-centered autophagy machinery regulates adiponectin secretion via the crosstalk with the exocyst pathway. Overall, our study will establish a new mechanistic paradigm for the Becn1-centered autophagy pathway in adipose tissue to prevent T2D, beyond its role in self-degradation.

项目概要/摘要 该提案的目标是展示一种新颖的非降解、非细胞自主机制 尽管新的证据表明自噬机制调节新陈代谢。 异常与代谢功能障碍有关，这是自噬调节胰岛素的机​​制 敏感性很大程度上是未知的。自噬通常被认为是一种破坏和降解过程。 我们最近发现了一种由 ULK1-Vps34-Becn1 调节的新的非降解功能。 脂肪组织中的自噬机制，可能在全身 AMPK 激活和胰岛素中发挥关键作用 脂联素是一种脂肪源性激素（脂肪因子），其循环减少强烈。 与 2 型糖尿病 (T2D) 和 SNP 引起的低脂联素血症相关。 人类脂联素基因突变与胰岛素抵抗和 T2D 相关，并且 然而，脂联素敲除小鼠的表型与人类表型相似并出现胰岛素抵抗。 脂联素的功能重要性，调节脂联素分泌的机制很少受到关注 我们发现自噬过度活跃的突变小鼠具有活性。 必需自噬蛋白 Becn1 的突变（Becn1F121A 敲入小鼠）改善了胰岛素敏感性 响应高脂肪饮食喂养，这是由循环因素引起的。 胰岛素敏感性循环因素，我们进行了激素筛查并确定了更高水平的 自噬过度活跃的 Becn1F121A 小鼠血清中的脂联素我们发现，一方面，脂肪- 特定的 Becn1F121A 表达足以改善全身胰岛素敏感性并增加循环 另一方面，消耗 Becn1 或抑制两种上游自噬激酶 ULK1 和 我们发现，Vps34 可减少小鼠体内脂联素的循环。 外囊成分 Sec6/Exoc3 是 Becn1 的结合伴侣，并优先与过度活跃的细胞结合 受初步数据的启发，我们提出了 ULK1-Vps34- 的总体假设。 Becn1自噬轴通过Becn1-外囊结合促进脂联素分泌，从而提高胰岛素敏感性 在脂肪细胞中，我们将这种途径称为“自噬促进分泌”。 结合使用遗传、成像、细胞生物学、生物化学和代谢方法，实现以下目标： 目标 1 是确定活性 Becn1 是否激活 AMPK 并通过脂联素提高胰岛素敏感性 目标 2 是确定 ULK1-Vps34-Becn1 自噬轴是否在脂肪组织中发挥作用 非细胞自主调节全身胰岛素敏感性；目标3是证明分子机制 以Becn1为中心的自噬机制通过串扰调节脂联素分泌的机制 总的来说，我们的研究将为以 Becn1 为中心的机制建立一个新的范式。 脂肪组织中的自噬途径预防 T2D 的作用超出了其自身降解的作用。