Proteoglycans in Growth Factor Signaling and Development

描述（由申请人提供）：硫酸乙酰肝素蛋白聚糖（HSPGs）是在细胞表面和细胞外基质中发现的丰富分子。在过去的十年中，这些分子已被证明在控制细胞对分泌生长因子的反应和信号分子在基质中的分布中发挥关键作用。我们的长期目标是了解这些分子在发育过程中如何影响细胞行为和组织组装。最近在我的实验室中，使用模式生物果蝇的工作已经证明了HSPGs在塑造无翼（Wg）形态原的梯度，控制视觉系统中的轴突引导以及影响神经肌肉突触的形式和功能方面的作用。我们提出的研究有三个广泛但相关的目标：1)确定HSPGs是否通过调节内吞作用和细胞内运输来控制Wg的分布；2)确定HSPGs是否通过控制内吞作用和生长因子信号传导来影响突触组装；3)确定HSPGs是否控制生长锥对引导信号的反应，或指导信号在脑细胞外基质中的分布。使用针对Wg的抗体和不同内体区室的标记，我们将评估突变体中Wg的运输，影响特定的HSPG， dally样和分泌酶Notum，从细胞表面去除Dip。我们认为，通过发育翼的Dip和Notum活动的结合，可以实现对梯度的区域控制。我们对突触的研究采用直接测量内吞作用的方法，使用荧光染料将其纳入内吞囊泡中，可视化对突触发育至关重要的生长因子，并通过遗传学研究确定突触中受HSPGs影响的信号系统。最后，我们将使用遗传策略来确定HSPG必须在哪些细胞类型中表达才能允许视觉系统中正常的轴突引导，以及轴突引导系统需要这些分子。HSPGs控制多种生长因子介导的信号传导，影响肿瘤发展、血管生成、组织修复和免疫系统功能中的趋化因子反应。硫酸乙酰肝素的生物合成是正常骨发育所必需的，特定的HSPGs影响人类的生长调节。因此，对这些不同分子的细胞和分子的详细了解对于影响人类疾病的一些基本过程具有根本的重要性。

DESCRIPTION (provided by applicant): Heparan sulfate proteoglycans (HSPGs) are abundant molecules found on cell surfaces and in the extracellular matrix. In the last decade these molecules have been shown to play critical roles in controlling responses of cells to secreted growth factors, and the distributions of signaling molecules in the matrix. Our long-term objectives are to understand how these molecules affect cellular behavior and the assembly of tissues during development. Recent work in my lab using the model organism Drosophila has demonstrated roles for HSPGs in shaping the gradient of the Wingless (Wg) morphogen, controlling axon guidance in the visual system, and influencing the form and function of the neuromuscular synapse. The research we propose has three broad but related aims, 1) determine if HSPGs control the distribution of Wg by regulating endocytosis and intracellular trafficking, 2) establish if HSPGs affect synapse assembly by controlling endocytosis and growth factor signaling, and 3) determine if HSPGs govern responses of growth cones to guidance cues, or the distributions of guidance cues in the extracellular matrix of the brain. Using antibodies directed against Wg and markers for different endosomal compartments, we will assess the trafficking of Wg in mutants affecting a specific HSPG, Dally-like, and a secreted enzyme, Notum, that removes Dip from cell surfaces. We propose that regional control of Wg gradients are achieved by a combination of Dip and Notum activity in the developing wing. Our studies of the synapse employ direct measures of endocytosis using fluorescent dyes that are incorporated into endocytosed vesicles, visualization of growth factors critical for synapse development, and genetic studies to identify the signaling systems affected by HSPGs in the synapse. Finally, we will use genetic strategies to determine in what cell types HSPG must be expressed to permit normal axon guidance in the visual system, and what axon guidance systems require these molecules. HSPGs control signaling mediated by numerous growth factors that affect tumor development, angiogenesis, tissue repair, and chemokine responses in immune system function. Heparan sulfate biosynthesis is required for normal bone development and specific HSPGs affect growth regulation in humans. A detailed cellular and molecular understanding of these diverse molecules is therefore of fundamental importance in a number of fundamental processes affecting human disease.