Receptor Trafficking and the Response to Shh

受体贩运和对嘘的反应

• 批准号: 6867845
• 负责人: HENK ROELINK
• 金额: $ 29.29万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6867845
• 关键词: acidity /alkalinity; biological signal transduction; cell line; chick embryo; dynamin; embryogenesis; endocytosis; genetically modified animals; histogenesis; intermolecular interaction; intracellular transport; laboratory mouse; pancreas neoplasms; protein binding; protein localization; protein transport; receptor expression; transcytosis; vesicle /vacuole

DESCRIPTION (provided by applicant): Sonic Hedgehog is a morphogen. To fulfill this role, it is necessary that it is able to travel many cell diameters away from its source of synthesis through the responding tissue. This requirement appears to be in conflict with the biological properties of Shh; it both contains an Acyl and a cholesterol moiety, which severely curtail its solubility in a hydrophilic intercellular environment. Although a functional, soluble hexameric form of Shh has been identified, medium conditioned by Shh expressing cells do not accumulate Shh to levels high enough to elicit a response in neural plate explants. However, when such responsive tissue is in contact with Shh producing cells, long-range Shh signaling can be observed in the explant, indicating that Shh is actively transported in the plane of the responding tissue. It is hypothesized that this long-range transport is mediated in part by transcytosis, which is supported by observation in Drosophila that export of cholesterol-associated Shh homolog Hedgehog (Hh) requires the activity of a dedicated molecule, Dispatched (Disp), while the uptake of Shh and Hh is mediated by the Disp homolog Patched (Ptc). In addition, the Ptc1-mediated trafficking of Shh into late endosomes is required to initiate the Shh response. To complete transcytosis in these responding cell it is necessary that Shh is transported from the late endosomes to the cell surface and made available to neighboring cells, and it is hypothesized that this is mediated by Disp. The hypotheses will be tested determining if Ptc1-mediated and Disp1-mediated trafficking of Shh are required in concert for long-range signaling. Determine the long-range signaling efficacy of alternatively anchored forms of Shh. It will be determined if the acidic environment in late endosomes favors Shh binding to Dispatched, while the neutral environment in the intercellular space allows Shh to bind to Ptc1, creating a continuous chain of events resulting in transcytosis. The requirement for intracellular transport in generating a long-range signal will be tested by blocking the function of Rabs and Dynamin. The Shh response coupled to transcytosis allows the generation of a graded Shh response, in a tissue actively responding to Shh, without the requirement for long-range transport in the intercellular space, and provides an explanation for the unusual activities of Ptc1 and Disp1. Better understanding of the mechanism by which the long-range Shh signal forms is important. Inappropriate activation of the Shh response is the cause of a wide variety of cancers, including a high fraction of pancreatic tumors, while normal Shh signaling is required for the development of many organ systems.

描述（由申请人提供）：Sonic Hedgehog 是一种形态发生素。为了发挥这一作用，它必须能够通过响应组织远离其合成源许多细胞直径。这一要求似乎与“嘘”的生物学特性相冲突；它都含有酰基和胆固醇部分，这严重降低了其在亲水性细胞间环境中的溶解度。尽管已鉴定出功能性、可溶性六聚体形式的Shh，但用Shh 表达细胞调节的培养基不会将Shh 积累到足以在神经板外植体中引发反应的水平。然而，当这种响应组织与产生Shh的细胞接触时，可以在外植体中观察到长程Shh信号传导，表明Shh在响应组织的平面中活跃地运输。据推测，这种长程运输部分是由转胞吞作用介导的，果蝇中观察到胆固醇相关的Shh同源物Hedgehog (Hh)的输出需要专用分子Dispatched (Disp)的活性，而Shh和Hh的摄取是由Disp同源物Patched (Ptc)介导的。此外，启动Shh反应需要Ptc1介导的Shh转运至晚期内体。为了在这些响应细胞中完成转胞吞作用，Shh 必须从晚期内体转运到细胞表面并提供给邻近细胞，并且假设这是由 Disp 介导的。将测试这些假设，以确定长距离信号传导是否需要 Ptc1 介导和 Disp1 介导的 Shh 运输协同作用。确定替代锚定形式的“Shh”的远程信号传导功效。将确定晚期内体中的酸性环境是否有利于Shh与Dispatched结合，而细胞间隙中的中性环境是否允许Shh与Ptc1结合，从而产生导致转胞吞作用的连续事件链。通过阻断 Rabs 和 Dynamin 的功能来测试产生长距离信号对细胞内运输的要求。与转胞吞作用相结合的Shh反应允许在主动响应Shh的组织中产生分级Shh反应，而不需要在细胞间隙中进行长距离运输，并为Ptc1和Disp1的异常活动提供了解释。更好地理解长程“Shh”信号形成的机制非常重要。 Shh 反应的不当激活是多种癌症的病因，包括大部分胰腺肿瘤，而正常的 Shh 信号传导是许多器官系统发育所必需的。