COMBINATORIAL SIGNALING THROUGH MEK1

描述(申请人提供)：许多类型的细胞需要附着在细胞外基质上，以便对可溶性生长因子做出反应而增殖，甚至生存。癌细胞的显著特征是它们减少或改变了对黏附的依赖以促进增殖和生存，从而导致动物不适当的生长。此外，黏附和可溶性因子信号的整合缺陷可能会导致转移过程中不适当的运动，或者导致免疫细胞功能的缺陷。ERK与这些疾病状态中的每一种都有关联，黏附信号被发现在组织培养中的增殖和迁移反应中都起着重要的作用。因此，在这些关键的正常和病理过程中，黏附和生长因子信号整合以改变ERK信号的持续时间和定位的机制知之甚少，这在理论上和临床上都有相当大的兴趣。我建议通过两个特定的目标来研究这些机制：1.通过分子支架整合黏附和生长因子信号。MEK可以作为生长因子信号转导ERK的锚定感受器，尽管它导致锚定依赖的机制尚不清楚。我们将专注于MEK1的磷酸化和MEK1特异性信号复合体的组装，作为黏附和生长因子信号的整合点。MP1是一种MEK1特异性结合伙伴，其性质表明它在这种信号复合体的组装中发挥着关键作用。我们还将确定新的依赖于磷酸化的结合伙伴，通过将MEK1与相关的激酶和小的GTP酶结合起来，预计将整合黏附和生长因子信号。将评估MEK1磷酸化和结合伙伴对锚定非依赖性ERK信号转导的贡献。2.趋化过程中MEK1的信号整合。我们的数据揭示了片状脂膜中局部ERK激活的MEK1特异性机制。由于MEK1-，而不是MEK2-nulI，成纤维细胞显示迁移缺陷，我们将使用重建实验来定量MEK1结合伙伴和磷酸化位点对趋化所需的形态和梯度传感过程的贡献。为了补充这些研究，我们将研究MEK1的磷酸型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感知黏附和生长因子信号以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.