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，以便响应可溶性生长因子而增殖，并且事实上，为了生存。癌细胞的标志性特征是它们对增殖和存活的粘附的依赖减少或改变，从而导致动物的不适当生长。此外，来自粘附和可溶性因子的信号整合缺陷可能导致转移过程中的不适当运动，或导致免疫细胞功能缺陷。 ERK 与这些疾病状态有关，并且发现粘附信号在组织培养中的增殖和迁移反应中发挥重要作用。因此，在这些关键的正常和病理过程中，粘附和生长因子信号整合以改变 ERK 信号传导的持续时间和定位的机制尚不清楚，这引起了相当大的学术和临床兴趣。我建议以两个具体目标来研究这些机制： 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传导至 ERK 的锚定传感器，尽管其赋予锚定依赖性的机制尚不清楚。我们将重点关注 MEK1 磷酸化和 MEK1 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。 MP1（MEK1 特异性结合伴侣）的特性表明它在此类信号复合物的组装中发挥着关键作用。我们还将鉴定新的磷酸化依赖性结合伴侣，预计通过将 MEK1 与相关激酶和小 GTP 酶结合起来，整合粘附和生长因子信号传导。将评估 MEK1 磷酸化和结合伴侣对锚定非依赖性 ERK 信号传导的贡献。 二.趋化过程中 MEK1 的信号整合。我们的数据揭示了板状伪足中局部 ERK 激活的 MEK1 特异性机制。由于成纤维细胞 MEK1-而非 MEK2-nulI 表现出迁移缺陷，因此我们将使用重构实验来定量 MEK1 结合配偶体和磷酸化位点对趋化性所需的形态和梯度感应过程的贡献。为了补充这些研究，我们将研究 MEK1 磷酸形式的亚细胞定位以及趋化细胞中相关的已知和新鉴定的结合配偶体。这些研究有可能揭示 MEK1 感知粘附和生长因子信号以调节定向细胞运动的通用机制。

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.