REGULATION OF FGF ACTIVITY BY FGF RECEPTOR SIGNALING

成纤维细胞生长因子(FGFs)是肝素家族中的一员。 结合多肽，在广泛的一系列 包括细胞生长、分化在内的生物过程 血管生成、组织修复和转化的FGFs介导其 通过与高亲和力细胞表面受体结合而产生的生物学效应。 成纤维细胞生长因子受体家族包含四个成员，每个成员 受体能够与多种受体结合并对其作出反应。 成纤维细胞生长因子的类型。与其他生长因子受体类似，成纤维细胞生长因子 受体具有固有的酪氨酸激酶活性。因此，成纤维细胞生长因子 与受体的胞外区结合导致受体 自身磷酸化和底物酪氨酸磷酸化。 尽管一些其他酪氨酸激酶生长的底物 因子受体已被鉴定，成纤维细胞生长因子的底物 受体的特性还有待研究。因此，这些机制 从而使成纤维细胞生长因子受体将配体结合转化为特异性 对靶细胞的反应仍然知之甚少。此外， 目前尚不清楚为什么不同类型的细胞对 FGFs。为了解决这些问题，数组 成纤维细胞生长因子受体存在于分化细胞的表面 对成纤维细胞生长因子(PC12细胞)的反应与目前的进行比较 在对成纤维细胞生长因子作出反应而增殖的细胞表面 (瑞士3T3成纤维细胞)。这两种细胞都只有FGFR-1 在它们的表面上，表明存在细胞类型特异性的成纤维细胞生长因子 将受体激活与多种受体连接的受体底物 不同的路径。这项拨款申请中提出的研究 旨在表征其中两种特定细胞类型的FGFR-1 信号通路。作为描述这些特性的第一种方法 信号通路，我们已经进行了双杂交筛选 利用FGFR-1的胞质结构域作为诱饵和 以PC12cDNA文库为猎物。一些阳性克隆是 我们建议结合使用免疫学、 用分子和生物技术研究这些蛋白的作用 两者在成纤维细胞生长因子受体信号转导中可能的受体底物 PC12细胞和瑞士3T3成纤维细胞。此外，我们计划使用 各种不同的酶抑制剂以进一步表征 活化的细胞增殖和分化途径 FGFR-1。通过这种方式，我们应该能够确定关键因素 参与FGFs对细胞类型特异性信号的调节。 此外，确定的每一种底物都将提供可能的 FGFs在细胞上的活性可以被调节的位置， 或许可以开发出新的治疗策略 用于治疗成纤维细胞生长因子依赖型疾病。

The fibroblast growth factors (FGFs) are a family of heparin- binding polypeptides which have a role in a wide array of biological processes including cell growth, differentiation angiogenesis, tissue repair and transformation FGFs mediate their biological effects by binding to high affinity cell surface receptors. The FGF receptor family contains four members and each of these receptors is capable of binding and responding to more than one type of FGF. Similar to other growth factor receptors, the FGF receptors possess intrinsic tyrosine kinase activity. Thus, FGF binding to the extracellular domain of a receptor leads to receptor autophosphorylation and substrate tyrosine phosphorylation. Although a number of substrates of other tyrosine kinase growth factor receptors have been identified, the substrates of the FGF receptors remain to be characterized. Thus, the mechanisms whereby FGF receptors transduce ligand binding into specific responses in target cells are still poorly understood. Furthermore, it is unclear why different cell types show distinct responses to FGFs. In order to bing to address these questions, the array of FGF receptors present on the surface of a cell which differentiates in response to FGF (PC12 cells) was compared with that present on the surface of a cell which proliferates in response to FGF (Swiss 3T3 fibroblasts). Both cell types have exclusively FGFR-1 on their surfaces, suggesting that there are cell type-specific FGF receptor substrates which connect receptor activation to a varety of distinct pathways. The research proposed in this grant application is designed to characterize two of these cell type-specific FGFR-1 signaling pathways. As a first approach to characterizing these signaling pathways, we have carried out a two hybrid screen utilizing the cytoplasmic domain of FGFR-1 as the bait and a PC12 cDNA library as the prey. A number of positive clones were obtained and we propose to use a combination of immunological, molecular and biological techniques to study the role of these putative receptor substrates in FGF receptor signaling in both PC12 cells and Swiss 3T3 fibroblasts. In addition, we plan to use a variety of different enzyme inhibitors to further characterize the proliferation and differentiation pathways initiated by activation of FGFR-1. In this way, we should be able to identify key factors involved in the regulation of cell type-specific signaling by FGFs. In addition, each of the substrates identified will provide a possible site at which the activities of FGFs on cells could be modulated, perhaps allowing for the development of new therapeutic strategies for the treatment of FGF-dependent disease.