Regulation of Macropinocytosis by Hssh3bp1

Hssh3bp1 对巨胞饮作用的调节

基本信息

批准号：
6685044
负责人：
LESZEK KOTULA
金额：
$ 28.9万
依托单位：
INSTITUTE FOR BASIC RES IN DEV DISABIL
依托单位国家：
美国
项目类别：
财政年份：
2003
资助国家：
美国
起止时间：
2003-05-15 至 2004-04-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to understand the structure, function and regulatory processes of the cell membrane skeleton and its involvement in human diseases and particularly in brain tumorigenesis. Recent studies also implicate membrane cytoskeletal proteins in normal brain development and behavior, and proper electrophysiological activity of neurons. Therefore, it is critical to develop a detailed understanding of molecular and cellular processes regulated by membrane cytoskeletal proteins. Membrane skeleton is a multiprotein structure in which spectrin plays a major structural role. Based on its binding properties to alpha spectrin Src homology 3 domain (SH3) we identified a novel protein designated human spectrin S H 3 domain-binding protein 1, or Hssh3bp1. Our recent work suggest that a spectrin-like protein and Hssh3bp1 participate in regulation of macropinocytosis. Macropinocytosis is a type of endocytosis that occurs through vesicles larger than 200 nm and is critical for cellular uptake of fluid and macromolecules. Physiological significance of macropinocytosis is largely unknown but is has been postulated to be involved in immunological responses and cellular uptake of some pathogens. Significantly, cancer cell lines have been demonstrated to up-regulate macropinocytosis in response to growth factor stimulation. Our data indicate that increased Hssh3bp1 expression inhibits macropinocytosis and that Hssh3bp1 expression is abnormally regulated in glioma tumor cell lines. These data support our working hypothesis that Hssh3bp1 inhibits macropinocytosis by opposing growth factor receptor stimulation. The proposed studies focus on determining mechanism of regulatory function of Hssh3bp1 in macropinocytosis using human glioma cell lines as a model system. The function of Hssh3bp1 in macropinocytosis and in cell growth may involve its binding partner, Abl tyrosine kinase. Our mechanistic hypothesis of this research proposal is that tyrosine-phosphorylated Hssh3bp1 inhibits Abl kinase resulting in decreased cell growth due to reduced phosphorylation of multiple mitogenic targets of Abl kinase. Alternatively, Hssh3bp1 binding to Abl in macropinosomes sequesters Abl in cytoplasm, consequently, Abl kinase cannot translocate to the nucleus, a process known to control cell growth. In addition to testing this hypothesis, we will determine whether other proteins known to affect macropinocytosis also regulate Hssh3bp1 phosphorylation and control the Hssh3bp1 function. These studies are likely to lead to novel information regarding molecular regulation of macropinocytosis at the cellular level.

描述（由申请人提供）：该提案的长期目标是了解细胞膜骨架的结构、功能和调节过程及其与人类疾病，特别是脑肿瘤发生的关系。最近的研究还表明膜细胞骨架蛋白与正常的大脑发育和行为以及神经元的适当电生理活动有关。因此，详细了解膜细胞骨架蛋白调节的分子和细胞过程至关重要。膜骨架是一种多蛋白结构，其中血影蛋白起主要结构作用。基于其与 α 血影蛋白 Src 同源 3 结构域 (SH3) 的结合特性，我们鉴定了一种新蛋白，命名为人血影蛋白 SH 3 结构域结合蛋白 1，或 Hssh3bp1。我们最近的工作表明血影蛋白样蛋白和 Hssh3bp1 参与巨胞饮作用的调节。巨胞饮作用是一种内吞作用，通过大于 200 nm 的囊泡发生，对于细胞摄取液体和大分子至关重要。巨胞饮作用的生理意义很大程度上未知，但据推测与免疫反应和某些病原体的细胞摄取有关。值得注意的是，癌细胞系已被证明可以响应生长因子刺激而上调巨胞饮作用。我们的数据表明，Hssh3bp1 表达增加会抑制巨胞饮作用，并且 Hssh3bp1 表达在神经胶质瘤肿瘤细胞系中受到异常调节。这些数据支持我们的工作假设，即 Hssh3bp1 通过对抗生长因子受体刺激来抑制巨胞饮作用。拟议的研究重点是使用人胶质瘤细胞系作为模型系统确定 Hssh3bp1 在巨胞饮作用中的调节功能机制。 Hssh3bp1 在巨胞饮作用和细胞生长中的功能可能涉及其结合伴侣 Abl 酪氨酸激酶。我们对该研究提案的机制假设是，酪氨酸磷酸化的 Hssh3bp1 抑制 Abl 激酶，由于 Abl 激酶的多个有丝分裂靶标的磷酸化减少，导致细胞生长减少。或者，Hssh3bp1 与大胞质体中的 Abl 结合，将 Abl 隔离在细胞质中，因此，Abl 激酶不能转位至细胞核，这是已知控制细胞生长的过程。除了检验这一假设之外，我们还将确定已知影响巨胞饮作用的其他蛋白质是否也调节 Hssh3bp1 磷酸化并控制 Hssh3bp1 功能。这些研究可能会带来有关细胞水平巨胞饮作用分子调节的新信息。