Regulation of Intestinal PYY cell function

描述（申请人提供）：肠内分泌细胞在营养物质的消化和吸收中发挥着关键作用，是正常生命所必需的。肠内分泌L细胞特别令人感兴趣，因为它有能力感知肠腔内容物，并根据反应分泌多种激素。其中两种激素处于糖尿病和肥胖研究的前沿：1) 胰岛素刺激胰高血糖素样肽 1 (GLP-1)； 2) 饱腹感肽酪氨酸 (PYY)。为了研究L细胞，申请人的实验室开发了一种转基因小鼠模型，其中PYY启动子驱动增强型绿色荧光蛋白（GFP）的表达。使用 PYY-GFP 模型和共焦激光扫描显微镜 (LSCM)，申请人和他的团队已经表征了 L 细胞中存在类似于轴突的长（超过 50 × 5m）基底细胞质过程。申请人的长期目标是了解肠内分泌细胞，特别是L细胞，如何与肠神经元交换分子信息以诱导饱腹感并调节食欲。该提案的目的是通过评估 L 细胞基础过程在 PYY 分泌中的作用以及表征调节其生长和维持的因素，确定 L 细胞基础过程在 L 细胞功能中的重要性。核心假设是，L 细胞基底突是由肠神经胶质细胞产生的特定信号培育的，并起到伪轴突的作用。该假设是根据申请人开发的初步数据提出的，这些数据表明L细胞与肠神经系统的元件具有密切的关系。其基本原理是，通过定义基础过程的功能和调节，可以开发新的方法来调节 L 细胞的激素分泌。中心假设将在两个具体目标上进行检验：目标 1 是确定神经营养因子对 L 细胞中轴突样延伸的影响。申请人将检查培养的原代 L 细胞和含有 L 细胞的肠道类器官模型中的轴突伸长。目标 2 是表征 L 细胞基底过程中的神经丝并确定它们在 PYY 分泌中的作用。申请人将使用RNAi技术在体外和体内研究L细胞中发现的神经丝。由于 PYY 是一种主要的饱腹感信号，因此 L 细胞和肠神经元之间的物理连接预计会对食欲的调节产生重要影响。拟议的项目将为申请人提供成为胃肠道内分泌学领域的独立研究者所需的培训。

DESCRIPTION (provided by applicant): Enteroendocrine cells play a key role in nutrient digestion and absorption, and are essential for normal life. The enteroendocrine L cell is of particular interest because it has the capacity to sense contents of the gut lumen and, in response, secretes several hormones. Two of those hormones are at the forefront of diabetes and obe- sity research: 1) the insulin-stimulating glucagon-like peptide 1 (GLP-1); and, 2) the satiety-inducing peptide tyrosine tyrosine (PYY). To study L cells, the applicant's laboratory has developed a transgenic mouse model in which the PYY promoter drives the expression of enhanced green fluorescent protein (GFP). Using the PYY- GFP model along with confocal laser scanning microscopy (LSCM), the applicant and his team have characterized the existence in L cells of a long (more than 50 5m) basal cytoplasmic process that resembles an axon. The long-term goal of the applicant is to understand how enteroendocrine cells, in particular the L cell, ex- change molecular information with enteric neurons to induce satiety and regulate appetite. The objective of this proposal is to determine the importance of the L cell basal process in the function of L cells, by assessing its role in PYY secretion and by characterizing the factors that regulate its growth and maintenance. The central hypothesis is that the L cell basal process is nurtured by specific signals derived from enteric glia, and functions as a pseudo-axon. The hypothesis has been formulated based on preliminary data developed by the applicant that show that L cells have an intimate relationship with elements of the enteric nervous system. The rationale is that by defining the function and regulation of basal processes new approaches can be developed to modulate hormone secretion from L cells. The central hypothesis will be tested in two specific aims: Aim 1 is to determine the effects of neurotrophic factors on the axon-like extension in L cells. The applicant will examine axonal process elongation in cultured primary L cells and in an intestinal organoid model that contains L cells. Aim 2 is to characterize the neurofilaments in L cell basal processes and define their role in PYY secretion. The applicant will use RNAi techniques to study in vitro and in vivo the neurofilaments found in L cells. Because PYY is a major satiety signal, the physical connection between the L cell and enteric neurons is ex- pected to carry important consequences for the regulation of appetite. The proposed project will provide the applicant with the required training to become an independent investigator in the field of gastrointestinal endocrinology.