MECHANISMS OF OBESITY AND THE AGOUTI SIGNALING PROTEIN

肥胖机制和 AGOUTI 信号蛋白

• 批准号: 2148856
• 负责人: Gregory Stefan Barsh
• 金额: $ 12.42万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-25 至 1998-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2148856
• 关键词: 3T3 cells; biological signal transduction; embryonic stem cell; gene expression; gene mutation; genetic disorder; genetically modified animals; laboratory mouse; molecular pathology; obesity; polymerase chain reaction; protein biosynthesis; western blottings

DESCRIPTION (Adapted from applicant's abstract): Genetic obesity in animal models is an invaluable tool for deciphering cause from effect in the complex series of behavioral, hormonal and metabolic changes that accompany disturbances in the regulation of body weight. Recent experiments from the applicant's laboratory have demonstrated that the first recognized obesity mutation, "the yellow mouse", is caused by ectopic expression of the agouti protein, a novel signaling molecule that normally controls the synthesis of pure yellow pigment in hair follicles. In mice that carry the lethal yellow (Ay) or the viable yellow (Avy) mutations, hyperphagia, hyperinsulinemia, and altered adipocyte metabolism are associated with expression of the agouti gene product in nearly every tissue of the body. However, the mechansim of agouti signaling in the hair follicle has not been determined, and it is not clear whether the initiating events in agouti-induced obesity occur at the level of the central nervous system, the pancreas, or the adipocyte. The biology and amino acid sequence of the agouti protein suggest that it acts locally in a paracrine fashion, and that proteolytic processing occurs during or shortly after secretion. As a first step towards understanding the normal agouti signaling pathway, antisera directed to specific regions of the agouti protein will be used to characterize its biosynthesis in vitro and to define its biologically active form in vivo. To determine if expression of agouti in a particular target tissue is either necessary or sufficient to cause obesity, transgenic mice will be constructed in which agouti expression is directed to the brain, to the integument, to the pancreas, or to adipocytes. At the cellular level, there are two hypotheses for agouti signaling. One postulates that agouti blocks the actions of alpha-melanocyte stimulating hormone (alpha-MSH) and related molecules at central nervous system receptors, in which case abnormalities in nutrient intake and the autonomic nervous system are likely to be primary events in the development of obesity. Alternatively, the agouti protein may bind to its own, as yet unidentified, receptor, in which case abnormalities in energy balance are likely to be primary events. These possibilities will be distinguished by determining the effects of agouti expression on melanocortin receptor binding and activation in cell culture. Finally, a potential role for agouti signaling in the normal regulation of body weight will be investigated by identifying and isolating agouti homologs in humans and in mice. The function of selected homologs in mice will be assessed in the whole animal by gene disruption in embryonic stem cells.

描述（改编自申请人的摘要）：动物中的遗传肥胖 模型是从效果中解密原因的宝贵工具 随之而来的一系列行为，荷尔蒙和代谢变化 体重调节的干扰。 最近的实验 申请人的实验室证明了第一个认可的肥胖症 突变，“黄小鼠”是由Agouti异位表达引起的 蛋白质是一种新型信号分子，通常控制合成 毛囊中的纯黄色颜料。 在携带致命的老鼠中 黄色（AY）或可行的黄色（AVY）突变，倍形， 高胰岛素血症和脂肪细胞代谢改变与 几乎每个组织中的Agouti基因产物的表达。 但是，毛囊中的Agouti信号的机制尚未 已经确定，目前尚不清楚是否在 Agouti诱导的肥胖症发生在中枢神经系统的水平， 胰腺或脂肪细胞。 Agouti蛋白的生物学和氨基酸序列表明 以旁分泌方式在本地作用，并且发生蛋白水解处理 在分泌后不久或不久。 作为理解的第一步 正常的Agouti信号通路，抗血清针对特定区域 Agouti蛋白的生物合成将用于表征 体外定义其生物活性形式。 确定是否 在特定目标组织中的Agouti表达是必要的或 足以引起肥胖症，将建造转基因小鼠 agouti表达直接直接直接向大脑，外皮和 胰腺或脂肪细胞。 在细胞级别，有两个 假设Agouti信号传导。 一个假设Agouti阻止了 α-甲状腺细胞刺激激素（Alpha-MSH）和相关的作用 中枢神经系统受体的分子，在这种情况下异常 在营养摄入量和自主神经系统中可能是 肥胖发展的主要事件。 或者，Agouti 蛋白质可能与蛋白质结合，但尚未确定的受体，在这种情况下 能量平衡异常可能是主要事件。 这些 通过确定Agouti的影响来区分可能性 在细胞培养物中黑色皮质素受体结合和激活上的表达。 最后，Agouti信号在正常调节中的潜在作用 体重将通过识别和隔离Agouti来研究 人类和小鼠的同源物。 小鼠选定同源物的功能 将通过胚胎茎中的基因破坏在整个动物中评估 细胞。