REGULATION OF FGF ACTIVITY BY FGF RECEPTOR SIGNALING

成纤维细胞生长因子（FGF）是肝素家族的一员。 结合多肽，其在广泛的 包括细胞生长、分化 血管生成、组织修复和转化FGF介导其 通过与高亲和力细胞表面受体结合而产生生物学效应。 FGF受体家族包含四个成员，每个成员 受体能够结合并响应多个 FGF的类型 与其他生长因子受体类似，FGF 受体具有固有的酪氨酸激酶活性。 因此，FGF 与受体的细胞外结构域结合导致受体 自磷酸化和底物酪氨酸磷酸化。 虽然许多其他酪氨酸激酶生长的底物 已经鉴定了FGF受体，FGF的底物 受体仍有待鉴定。 因此， 从而FGF受体与配体结合成特异性的 对靶细胞的反应仍然知之甚少。 此外，委员会认为， 目前还不清楚为什么不同的细胞类型对 FGFs。 为了解决这些问题， FGF受体存在于细胞表面， 对FGF（PC 12细胞）反应与本发明的比较 在响应FGF而增殖的细胞表面上 （Swiss 3 T3成纤维细胞）。 两种细胞类型都具有FGFR-1特异性。 在它们的表面，这表明有细胞类型特异性FGF 受体底物，其将受体活化与多种 不同的路径。 这项资助申请中提出的研究 旨在表征这些细胞类型特异性FGFR-1中的两种 信号通路 作为描述这些特征的第一种方法， 信号通路，我们进行了双杂交筛选 利用FGFR-1的胞质结构域作为诱饵， 以PC 12 cDNA文库为目标。 大量的阳性克隆被 获得，我们建议使用免疫学， 分子和生物学技术来研究这些 FGF受体信号传导中的假定受体底物 PC 12细胞和Swiss 3 T3成纤维细胞。 此外，我们计划使用一个 各种不同的酶抑制剂，以进一步表征 增殖和分化途径启动的激活 FGFR-1。 这样，我们应该能够确定关键因素 参与FGF对细胞类型特异性信号传导的调节。 此外，所确定的每一种基质将提供一种可能的 可以调节细胞上FGF活性的位点， 也许可以开发新的治疗策略 用于治疗FGF依赖性疾病。

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.