Hypothalamic regulation by thyroid hormone receptor phosphorylation

甲状腺激素受体磷酸化对下丘脑的调节

• 批准号: 10717820
• 负责人: ANTHONY N HOLLENBERG
• 金额: --
• 依托单位: RUTGERS BIOMEDICAL AND HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-17 至 2023-10-01
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10717820
• 关键词: Affect; Body Weight decreased; Cell Nucleus; Cells; Cre driver; Eating; Energy Metabolism; Fasting; Feedback; Female; Functional disorder; Human; Hyperphagia; Hyperthyroidism; Hypothalamic structure; Hypothyroidism; Knock-in Mouse; Knock-out; Laboratories; Labyrinth; Left; Leptin; Leptin resistance; LoxP-flanked allele; Malnutrition; Mammals; Mediating; Mediator; Metabolism; Mus; Mutation; N-terminal; Neurons; Nuclear Hormone Receptors; Nutritional; Obesity; Overnutrition; Pathway interactions; Pattern; Phospho-Specific Antibodies; Phosphorylation; Phosphorylation Site; Pituitary Gland; Protein Isoforms; Regulation; Resistance; Retina; Role; SF1; Seminal; Serine; Signal Pathway; Signal Transduction; Site; Structure of nucleus infundibularis hypothalami; THRA gene; THRB gene; Thyroid Gland; Thyroid Hormone Receptor; Thyroid Hormone Resistance Syndrome; Thyroid Hormones; Time; adenylate kinase; diet-induced obesity; feeding; genomic locus; hypothalamic-pituitary-thyroid axis; interest; knockout animal; male; man; mimetics; mouse model; novel; nutrient deprivation; nutrition; paraventricular nucleus; reduced food intake

Three major thyroid hormone receptor (THR) isoforms, expressed from two genetic loci (Thra and Thrb), are present in mammals: THRA1, THRB1, and THRB2. Thyroid hormone (TH) acting through THRs regulate food intake metabolism and the hypothalamic-pituitary-thyroid (HPT) axis in man. Our laboratories have long been interested in the THRB2 isoform as a central regulator of the hypothalamic-pituitary-thyroid (HPT) axis, given its unique and limited-expression pattern. We recently found that THRB2 is heavily phosphorylated by both TH and AMP kinase (AMPK) at an N-terminal serine site (S101-mouse, S102-human), not found in other THRs. Based on increased food intake, obesity, and TH resistance in mice carrying a mutation of this phosphorylation site (S101A), we hypothesize that an AMPK-dependent THRB2 S101 phosphorylation pathway in the hypothalamus suppresses food intake and the HPT axis. We also hypothesize that dysfunction of this pathway results in leptin resistance, increased food intake, and obesity (Fig. 1). Three closely related aims are proposed: Specific Aim 1: Functionally co-localize hypothalamic THRB2 and AMPK action on feeding. Both the arcuate (ARC) and ventromedial nucleus (VMN) regulate feeding in a THRB- and AMPK-dependent manner. To begin to functionally localize THRB2 action in the hypothalamus, THRB2 will be removed from the POMC neurons in the ARC and SF-1 neurons in the VMN using Thrb2 floxed mice and cell-specific Cre drivers. Cell- specific KO of AMPKa2 in the same neurons will also be performed to understand AMPKa2’s role in feeding and in the p-THRB2 pathway. Both male and female mice will be studied, given higher THRB2 expression in female HA-tagged THRB2 mice. Specific Aim 2: Determine the role of THRB2 phosphorylation in feeding and mediating hypothalamic leptin signaling. Previous studies have clearly demonstrated that leptin regulates both the HPT axis and feeding. A potential mediator of leptin action is p-THRB2, given that S101A mice demonstrate leptin resistance. A phospho-specific antibody was developed to probe this pathway further and will be used in a time- course study of THRB2 phosphorylation during the fed-fasting transition. Furthermore, a phosphomimetic S101D KI mouse model was generated to determine if this change protects against diet-induced obesity. Specific Aim 3: Define the locus of TRH regulation by THRB2 during fasting. While fasting-induced suppression of the HPT axis is mediated by reduced TRH expression in the paraventricular nucleus (PVN), it remains unknown how HPT axis suppression is maintained in the setting of low TH levels. Strikingly, S101A mice display resistance to fasting-induced TRH suppression, suggesting that THRB2 S101 phosphorylation is critical in the sensing of low TH levels. This aim will determine the locus of fasting-induced and TH-dependent TRH suppression by targeting neurons in the ARC and PVN. The mechanism of suppression will be explored further by studying if THRB2 phosphorylation is a common mechanism regulating the HPT axis and food intake.

由两个基因位点（Thra 和 Thrb）表达的三种主要甲状腺激素受体 (THR) 亚型是 存在于哺乳动物中：THRA1、THRB1 和 THRB2 通过 THR 发挥作用来调节食物。 我们的实验室长期以来一直致力于研究人类的摄入代谢和下丘脑-垂体-甲状腺（HPT）轴。 鉴于 THRB2 亚型作为下丘脑-垂体-甲状腺 (HPT) 轴的中央调节剂，人们对它感兴趣 我们最近发现 THRB2 被 TH 和 TH 严重磷酸化。 位于 N 末端丝氨酸位点的 AMP 激酶 (AMPK)（S101-小鼠，S102-人），在其他基于 THR 中未发现。 携带这种磷酸化突变的小鼠的食物摄入量增加、肥胖和 TH 抵抗 位点（S101A），我们认为 AMPK 依赖性 THRB2 S101 磷酸化途径 我们还追踪到了下丘脑抑制食物摄入和 HPT 轴的功能障碍。 途径导致瘦素抵抗、食物摄入增加和肥胖（图 1）。 建议： 具体目标 1：在功能上使下丘脑 THRB2 和 AMPK 对进食的作用共定位。 弓状核 (ARC) 和腹内侧核 (VMN) 以 THRB 和 AMPK 依赖性方式调节摄食。 为了开始在下丘脑中功能定位 THRB2 的作用，THRB2 将从 POMC 中移除 使用 Thrb2 floxed 小鼠和细胞特异性 Cre Cell- 驱动程序对 ARC 中的神经元和 VMN 中的 SF-1 神经元进行研究。 还将对同一神经元中的 AMPKa2 进行特异性敲除，以了解 AMPKa2 在进食和进食中的作用 鉴于雌性小鼠中的 THRB2 表达较高，因此将对雄性和雌性小鼠进行研究。 HA 标记的 THRB2 小鼠具体目标 2：确定 THRB2 磷酸化在进食和介导中的作用。 先前的研究已经清楚地表明，下丘脑瘦素信号传导可以调节 HPT。 鉴于 S101A 小鼠表现出瘦素，瘦素作用的潜在介质是 p-THRB2。 开发了一种磷酸化特异性抗体来进一步探测该途径，并将在一段时间内使用。 进食-禁食过渡期间 THRB2 磷酸化的课程研究此外，磷酸盐模拟物。 生成 S101D KI 小鼠模型是为了确定这种变化是否可以预防饮食诱导的肥胖。 目标 3：确定禁食期间 THRB2 调节 TRH 的位点。 HPT 轴是由室旁核 (PVN) 中 TRH 表达减少介导的，但目前尚不清楚如何 在低 TH 水平的情况下，HPT 轴抑制得以维持，令人惊讶的是，S101A 小鼠表现出对 TH 的抵抗力。 禁食诱导的 TRH 抑制，表明 THRB2 S101 磷酸化对于感知低水平至关重要 TH 水平将通过靶向确定禁食诱导的和 TH 依赖性 TRH 抑制的位点。 通过研究 THRB2 是否可以进一步探讨 ARC 和 PVN 神经元的抑制机制。 磷酸化是调节 HPT 轴和食物摄入的常见机制。