Integration of innate immune function and metabolism by the TBK1-mTOR axis

项目摘要 肥胖相关的糖尿病是一种复杂的代谢紊乱，在全球范围内发病率不断上升。 保守的激酶mTOR(雷帕霉素的机制靶点)，它由两个催化核心组成 功能不同的多蛋白复合体(含Raptor的mTORC1和含Rictor的mTORC2)， 促进体内葡萄糖和脂肪的动态平衡。MTOR是一种保守的营养传感器，它集成了 一系列不同的局部和系统信号来控制细胞代谢和细胞生长。反常mTOR函数 导致II型糖尿病和各种免疫紊乱(以及其他疾病)。尽管生理学上 关于mTOR的重要性，我们对mTOR的规定和功能以及如何 MTOR与其他信号系统协同控制综合生理。我们实验室最近的工作 (Bodur等人)EMBO J 2018)为这一提议提供了科学前提，证明了天生的 免疫激酶TBK1直接磷酸化mTOR(位于S2159)，激活mTORC1和mTORC2信号。 此外，TBK1促进IFNb的产生的能力，IFNb是一种启动一线宿主防御的I型干扰素 抗感染微生物，需要mTOR S2159磷酸化和mTORC1活性。这项工作直接进行 连接了两个以前未知的信号系统，它们在功能上相互作用。正如之前的研究报告的那样，脂肪细胞- 特异性的TBK1基因敲除(KO)导致小鼠的全身性胰岛素抵抗(与脂肪细胞特异性的mTOR的KO一样， Raptor(MTORC1)，或Rictor(MTORC2))，我们决定研究TBK1-mTOR信号在 产生含有非磷酸化的“抗TBK1”mTOR敲入小鼠等位基因的代谢控制 ALA位于S2159(MtorA)。我们的初步结果表明，饮食诱导肥胖(DIO)MtorA/A小鼠表现出胰岛素 抵抗、高胰岛素血症和高血糖，尽管体重和肥胖相对于DIO没有变化 控制。我们的中心假设是，TBK1-mTOR信号对胰岛素抵抗和 肥胖期间的高血糖。具体地说，我们假设脂肪组织中TBK1-mTOR信号 促进脂肪细胞中营养物质的储存，防止异位脂肪沉积和胰岛素抵抗 肥胖。因此，我们进一步推测，脂肪细胞和巨噬细胞中的TBK1-mTORC1信号介导了抗- 在DIO期间促进全身胰岛素敏感性和血糖控制的炎症反应。要定义 脂肪细胞和巨噬细胞特异性的TBK1-mTOR信号在代谢控制中的作用，我们将确定 肥胖时脂肪细胞TBK1-mTOR信号促进血糖稳态的机制(目标1) 并明确了巨噬细胞中TBK1-mTOR信号在控制天然免疫功能和血糖中的作用 肥胖期间的控制(目标2)。除了定义体内TBK1-mTOR信号的生理作用外，这 该项目将加强我们对整合先天免疫和代谢反应的机制的理解 并预防肥胖相关的II型糖尿病-揭示潜在的新的治疗机会。

Project Summary Obesity-linked diabetes represents a complex metabolic disorder with increasing prevalence worldwide. The conserved kinase mTOR (mechanistic target of rapamycin), which comprises the catalytic core of two functionally distinct multiprotein complexes (raptor-containing mTORC1 and rictor-containing mTORC2), promotes glucose and lipid homeostasis in vivo. mTOR functions as a conserved nutrient sensor that integrates a diverse array of local and systemic signals to control cell metabolism and cell growth. Aberrant mTOR function contributes to type II diabetes and a variety of immune disorders (among other diseases). Despite the physiologic importance of mTOR, major gaps exist in our basic understanding of mTOR regulation and function and how mTOR cooperates with other signaling systems to control integrative physiology. Recent work from our lab (Bodur et al. EMBO J 2018) provides the scientific premise for this proposal, demonstrating that the innate immune kinase TBK1 phosphorylates mTOR (on S2159) directly to activate mTORC1 and mTORC2 signaling. Moreover, the ability of TBK1 to promote production of IFNb, a type I interferon that initiates first-line host defense against infectious microbes, requires mTOR S2159 phosphorylation and mTORC1 activity. This work directly linked two signaling systems not previously known to functionally interact. As prior work reported that adipocyte- specific Tbk1 knockout (KO) causes systemic insulin resistance in mice (as does adipocyte-specific KO of Mtor, Raptor (mTORC1), or Rictor (mTORC2)), we decided to investigate a potential role for TBK1-mTOR signaling in metabolic control by generating a “TBK1 resistant” mTOR knock-in mouse allele bearing non-phosphorylatable Ala at S2159 (MtorA). Our preliminary results indicate that diet-induced obese (DIO) MtorA/A mice exhibit insulin resistance, hyperinsulinemia, and hyperglycemia despite unchanged body weight and adiposity relative to DIO controls. Our central hypothesis posits that TBK1-mTOR signaling protects against insulin resistance and hyperglycemia during obesity. Specifically, we hypothesize that that TBK1-mTOR signaling in adipose tissue promotes nutrient storage in adipocytes and protects from ectopic lipid deposition and insulin resistance during obesity. We thus further postulate that TBK1-mTORC1 signaling in adipocytes and macrophages mediates anti- inflammatory responses that promote systemic insulin sensitivity and glycemic control during DIO. To define roles for adipocyte and macrophage-specific TBK1-mTOR signaling in metabolic control, we will determine the mechanisms by which adipocyte TBK1-mTOR signaling promotes glucose homeostasis during obesity (Aim 1) and define the role of TBK1-mTOR signaling in macrophages for control of innate immune function and glycemic control during obesity (Aim 2). In addition to defining physiologic roles for TBK1-mTOR signaling in vivo, this project will enhance our understanding of mechanisms that integrate innate immune and metabolic responses and protect against obesity-linked type II diabetes- revealing potential new therapeutic opportunities.