COMBINATORIAL SIGNALING THROUGH MEK1

描述（由申请人提供）：许多细胞类型需要附着在细胞外基质上，以便在可溶性生长因子的作用下增殖，甚至存活。癌细胞的标志性特征是它们对黏附增殖和存活的依赖减少或改变，从而导致动物体内的不适当生长。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不适当的运动或免疫细胞功能缺陷。ERK与这些疾病状态都有关系，并且发现粘附信号在组织培养中的增殖和迁移反应中都起着重要作用。因此，在这些关键的正常和病理过程中，粘附因子和生长因子信号如何整合以改变ERK信号的持续时间和定位，这一鲜为人知的机制具有相当大的智力和临床意义。我建议从两个方面研究这些机制：1 .通过分子支架整合粘附和生长因子信号。MEK可以作为生长因子向ERK发出信号的锚定传感器，尽管它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是mek1特异性结合伙伴，其特性表明它在这些信号复合物的组装中起关键作用。我们还将确定新的磷酸化依赖性结合伙伴，预计将通过支架MEK1与相关激酶和小gtpase整合粘附和生长因子信号。将评估MEK1磷酸化和结合伙伴对锚定非依赖性ERK信号的贡献。2。趋化过程中MEK1的信号整合。我们的数据揭示了mekl在板足中局部ERK激活的特异性机制。由于MEK1-（而非MEK2-nulI）成纤维细胞表现出迁移缺陷，我们将使用重构实验来量化MEK1结合伙伴和磷酸化位点对趋化性所需的形态学和梯度传感过程的贡献。为了补充这些研究，我们将研究磷酸化形式的MEK1和相关的已知和新发现的结合伙伴在趋化细胞中的亚细胞定位。这些研究有可能揭示MEK1通过感知粘附和生长因子信号来调节定向细胞运动的普遍机制。

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.