Control of ErbB Receptor Sorting in Endosomes

内体中 ErbB 受体分选的控制

基本信息

批准号：
6544872
负责人：
CATHLEEN R CARLIN
金额：
$ 28.92万
依托单位：
CASE WESTERN RESERVE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-09-05 至 2006-08-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The endosomal apparatus is a major site of membrane sorting in both endocytic and exocytic pathways. For ligand activated receptors it also provides a mechanism for achieving the proper balance of cell signaling from different membrane compartments. A main objective of this proposal is to understand how endocytosis controls cellular responses to the EGF receptor (EGFR), the prototype for the ErbB receptor family. The complexity of endocytic trafficking predicts that EGFRs use a multitude of distinct sorting signals at different locations in the cell. Characterization of these signals provides a framework for understanding regulation of EGFR transit in the endosomal apparatus. We have identified three non-overlapping sorting signals that control critical benchmarks in EGFR trafficking: 679-LL, which controls sorting in multivesicular endosome-to-lysosome transport intermediates or MVEs; 954-YLVI, which controls lysosomal sorting at a site intersecting the exocytic pathway; and 662-RxxxxPLTP, which controls sorting from endosomes to the plasma membrane. Completion of the proposed studies will provide new insights on the coordinated action of these signals during ligand-regulated EGFR trafficking. Since related ErbB receptors have divergent sorting signals compared to EGFR, we will also gain insight to how ErbB signaling in general is controlled by intracellular trafficking. This is particularly important for ErbB2, whose ligand-dependent activation by EGFR requires EGFR sequences that regulate post-endocytic trafficking and not intrinsic tyrosine kinase activity. The availability of dominant-inhibitory mutations that disrupt EGFR trafficking at defined steps also provides a unique set of reagents with which to study the temporal and spatial organization of signaling from endosomes. The following hypotheses will be tested: 1. Ligand-induced EGFR post-endocytic sorting to lysosomes is mediated by the concerted action of multiple sorting signals acting in a step-wise fashion. 2. The 679-LL MVE sorting signal is recognized as part of a larger motif whose physiological function is dependent on protein-protein interactions. 3. The 662-RxxxxPLTP sorting signal controls EGFR recycling to the plasma membrane, and is regulated by MAP kinase-mediated phosphorylation of Thr669. 4. The 679-LL sorting signal regulates EGFR signaling by controlling the balance of growth stimulatory pathways elicited during endocytosis. This hypothesis is based on new data suggesting that EGFRs with an inactivating L679A,L680A mutation selectively activate survival pathways compared to wild-type, and will be tested using both in vitro and in vivo experimental models.

描述（由申请人提供）：内体装置是胞吞和胞吐途径中膜分选的主要场所。对于配体激活的受体，它还提供了一种实现不同膜区室的细胞信号传导适当平衡的机制。该提案的主要目的是了解内吞作用如何控制细胞对 EGF 受体 (EGFR)（ErbB 受体家族的原型）的反应。内吞运输的复杂性预示着 EGFR 在细胞的不同位置使用多种不同的分选信号。这些信号的表征为理解内体装置中 EGFR 转运的调节提供了一个框架。我们已经确定了三个控制 EGFR 运输关键基准的非重叠分选信号： 679-LL，控制多囊泡内体到溶酶体转运中间体或 MVE 的分选； 954-YLVI，控制与胞吐途径交叉的位点的溶酶体分选； 662-RxxxxPLTP，控制从内体到质膜的分类。拟议研究的完成将为配体调节的 EGFR 运输过程中这些信号的协调作用提供新的见解。由于与 EGFR 相比，相关的 ErbB 受体具有不同的分选信号，因此我们还将深入了解 ErbB 信号传导通常如何受细胞内运输控制。这对于 ErbB2 来说尤其重要，因为 EGFR 的配体依赖性激活需要调节内吞后运输的 EGFR 序列，而不是调节内在酪氨酸激酶活性。在规定步骤破坏 EGFR 运输的显性抑制突变的可用性也提供了一套独特的试剂，用于研究内体信号传导的时间和空间组织。将测试以下假设： 1.配体诱导的 EGFR 内吞后分选至溶酶体是由以逐步方式起作用的多个分选信号的协同作用介导的。 2. 679-LL MVE 分选信号被认为是更大基序的一部分，其生理功能依赖于蛋白质-蛋白质相互作用。 3. 662-RxxxxPLTP 分选信号控制 EGFR 再循环至质膜，并受 MAP 激酶介导的 Thr669 磷酸化调节。 4. 679-LL 分选信号通过控制内吞过程中引发的生长刺激途径的平衡来调节 EGFR 信号传导。这一假设基于新数据，表明与野生型相比，具有失活 L679A、L680A 突变的 EGFR 选择性激活生存途径，并将使用体外和体内实验模型进行测试。