Dynamics of Wnt receptor activation, signal initiation and signal termination in vivo

发育中的胚胎和成体组织内细胞中Wnt受体激活、信号起始和信号终止的动力学过程必须接受并精确地解释特定的信号才能正常生长。Wnt家族的分泌蛋白就是这样一个信号。wnt通过增加蛋白-连环蛋白水平介导基因表达的精确变化。信号过多或过少都会导致组织缺陷和疾病。虽然已知wnt激活细胞表面受体，但尚不清楚配体激活受体在细胞膜或细胞内的什么位置起作用，它如何通过蛋白质disheveled激活细胞内信号级联，以及受体如何被关闭。本研究提出了一种新颖的体内方法，直接解决了这些问题。此外，它将确定disheveled如何阻断该途径中的中心调节因子（一种组装在支架蛋白轴蛋白周围的蛋白质复合物），并有望在体内确定受体启动信号如何导致轴蛋白复合物的抑制并诱导β -连环蛋白信号传导，这一过程仍然存在争议。近年来，对Wnt/ β -连环蛋白通路的更广泛的理解急剧增加。然而，许多发现来自体外实验，其功能意义有限。Wnt/ β -catenin通路的信号事件可以在果蝇模型系统的正常细胞背景下进行研究，强调了本文提出的研究的重要性。这些研究有望识别信号转导时动态变化的相互作用，从而大大增加我们对这一重要信号传导机制的理解。该提案将为一名研究生和三名本科生提供从事前沿研究的机会。此外，它将允许PI向K-12学生介绍基本发展和遗传学，并在当地学校推广以科学为基础的课程。

NSF Proposal IOS-1353799Marcel Wehrli, Ph.D.Dynamics of Wnt receptor activation, signal initiation and signal termination in vivoCells of developing embryos and adult tissues must receive and precisely interpret specific signals for proper growth. Secreted proteins of the Wnt family represent one such signal. Wnts elicit precise changes in gene expression mediated by increased levels of the protein ?beta-catenin. Too much or too little signal leads to tissue defects and disease. While it is known that Wnts activate cell surface receptors, it remains unclear where on the cell membrane or inside the cell the ligand-activated receptor functions, how it activates the intracellular signaling cascade via the protein Dishevelled and how the receptor is turned off. This proposal addresses these questions directly with a novel in vivo approach. In addition, it will identify how Dishevelled blocks the central regulator in the pathway, a protein complex assembled around the scaffold protein Axin, and is expected to identify in vivo how the receptor-initiated signal leads to the inhibition of the Axin complex and induces beta-catenin signaling, a process that remains controversial. Broader ImpactOur understanding of the Wnt/beta-catenin pathway has increased dramatically in recent years. However, many findings are derived from in vitro experiments and their functional significance is limited. The signaling events of the Wnt/beta-catenin pathway are amenable to investigation in their normal cellular context using the Drosophila model system, underscoring the significance of the studies proposed here. These investigations are expected to identify dynamically changing interactions as the signal is transduced, thereby greatly increasing our understanding of this important signaling mechanism.This proposal will provide an opportunity for one graduate student and three undergraduates to engage in cutting edge research. In addition, it will allow the PI to introduce K-12 students to basic development and genetics and to promote a science-based curriculum in local schools.