COMBINATORIAL SIGNALING THROUGH MEK1

描述（由申请人提供）：许多细胞类型需要附着于细胞外基质，以响应可溶性生长因子而增殖，并且实际上存活。癌细胞的标志性特征是它们对增殖和存活的粘附的依赖性降低或改变，导致动物中的不适当生长。此外，来自粘附和可溶性因子的信号的有缺陷的整合可能导致转移期间的不适当的运动，或导致免疫细胞功能的缺陷。ERK已被牵连在这些疾病状态中的每一个，并且发现粘附信号传导在组织培养中的增殖和迁移反应中起重要作用。因此，很少了解的机制，粘附和生长因子信号被整合，以修改这些关键的正常和病理过程中的ERK信号传导的持续时间和本地化是相当大的智力和临床的兴趣。我建议在两个具体目标中研究这些机制：I.通过分子支架整合粘附和生长因子信号。MEK可以作为生长因子信号转导至ERK的锚定传感器，尽管其赋予锚定依赖性的机制尚不清楚。我们将专注于MEK 1磷酸化和MEK 1特异性信号复合物的组装，作为粘附和生长因子信号的整合点。MP 1是一种MEK 1特异性结合伴侣，其特性表明它在这种信号复合物的组装中起着关键作用。我们还将确定新的，磷酸化依赖的结合伙伴预测整合粘附和生长因子信号的支架MEK 1与相关的激酶和小GTP酶。将评估MEK 1磷酸化和结合伴侣对锚定非依赖性ERK信号传导的贡献。 二.趋化性过程中MEK 1的信号整合。我们的数据揭示了在板状伪足中局部ERK激活的MEK 1特异性机制。由于MEK 1-，而不是MEK 2-nulI，成纤维细胞显示迁移缺陷，我们将使用重建实验来定量的MEK 1结合伙伴和磷酸化位点的形态学和梯度感应过程所需的趋化性的贡献。为了补充这些研究，我们将研究亚细胞定位磷酸形式的MEK 1和相关的已知和新发现的结合伴侣在趋化细胞。这些研究有可能揭示一个普遍的机制，通过该机制MEK 1感知粘附和生长因子信号来调节定向细胞运动。

DESCRIPTION (provided by applicant): Many cell types require attachment to the extracellular matrix in order to proliferate in response to soluble growth factors, and indeed, to survive. Hallmark characteristics of cancer cells are their reduced or altered dependence upon adhesion for proliferation and survival, contributing to inappropriate growth in the animal. Furthermore, defective integration of signals from adhesion and soluble factors may contribute to inappropriate motility during metastasis, or to defects in immune cell function. ERK has been implicated in each of these disease states, and adhesion signaling is found to play essential roles in both proliferative and migratory responses in tissue culture. Consequently, the poorly understood mechanisms by which adhesion and growth factor signals are integrated to modify the duration and localization of ERK signaling during these key normal and pathologic processes are of considerable intellectual and clinical interest. I propose to investigate these mechanisms in two Specific Aims: I. Integration Of Adhesion And Growth Factor Signals Through Molecular Scaffolding. MEK can serve as an anchorage-sensor for growth factor signaling to ERK, although the mechanisms by which it confers anchorage dependence are unknown. We will focus on MEK1 phosphorylation and assembly of MEKl-specific signaling complexes as points of integration for adhesion and growth factor signals. The properties of MP1, a MEK1-specific binding partner, suggest it plays a key role in the assembly of such signaling complexes. We will also identify novel, phosphorylation-dependent binding partners predicted to integrate adhesion and growth factor signaling by scaffolding MEK1 with relevant kinases and small GTPases. The contribution of MEK1 phosphorylation and binding partners to anchorage-independent ERK signaling will be assessed. II. Signal Integration At MEK1 During Chemotaxis. Our data reveal MEKl-specific mechanisms for localized ERK activation in lamellipodia. Since MEK1-, but not MEK2-nulI, fibroblasts show migration defects, we will use reconstitution experiments to quantitate the contribution of MEK1 binding partners and phosphorylation sites to both the morphological and gradient-sensing processes necessary for chemotaxis. To complement these studies, we will investigate the subcellular localization of the phospho-forms of MEK1 and relevant known and newly identified binding partners in chemotaxing cells. These studies have the potential to reveal a universal mechanism by which MEK1 senses both adhesion and growth factor signals to regulate directional cell motility.