Mechanisms of FGF Receptor Regulation and Signaling

描述（由申请人提供）：成纤维细胞生长因子（FGF）信号传导在哺乳动物发育和代谢以及疾病中发挥多效性作用。旁分泌FGF 1、FGF 4、FGF 7、FGF 8和FGF 9亚家族在精子发生、中胚层诱导、体节发生、器官发生和图案形成中起重要作用，而FGF 19亚家族以内分泌方式起作用以调节主要代谢过程，包括葡萄糖、脂质、胆固醇和胆汁酸代谢以及磷酸盐/维生素D稳态。FGF的多种活性通过受体酪氨酸激酶（RTK）的FGF受体（FGFR）亚家族传递。受干扰的FGF信号传导导致许多人类疾病，包括骨骼、生殖综合征、听力损失、肾磷酸盐消耗、神经退行性疾病和癌症。几种旁分泌FGF和所有内分泌FGF正在被用于药物开发。这一相互竞争的更新的四个具体目标是：表征上皮表达的FGF 4和FGF 9亚家族对间充质表达的FGFRc亚型具有特异性的结构基础。二.阐明a/bKlotho共受体通过内分泌FGF促进信号传导的结构基础。三.剖析A环酪氨酸磷酸化在致病性功能获得性突变引起的FGFR酪氨酸激酶过度活化中的作用。四.阐明FGFR募集和磷酸化FRS 2a的结构基础。重组蛋白表达和工程、X射线晶体学、表面等离子体共振（SPR）光谱、等温滴定量热法（ITC）、稳态动力学分析和时间分辨质谱将用于实现本提案的特定目的。获得的结构和生物物理/生化结果也将使用基于细胞和动物的试验进行验证。根据目标I获得的数据应提供旁分泌FGF在胚胎发育中的作用的分子见解，并且还促进用于组织修复和生物工程、促进用于细胞替代疗法的人胚胎干细胞的自我更新和分化的药物的发现。Aim II下生成的数据应增强我们对内分泌FGF在人体代谢中作用的理解，并为主要人类疾病（包括糖尿病，肥胖症，高胆固醇血症，结肠癌和慢性肾脏疾病）的药物发现提供蓝图，其中大多数代表了对公共卫生的巨大负担。目的III的结果将增强我们对FGFR和其他RTK中致病性突变的作用机制以及整个RTK超家族酪氨酸激酶活性调节的理解。由于底物募集和磷酸化的RTK是一个通用的事件在RTK信号，机制的见解下获得的目的IV也将直接适用于整个RTK超家族。

DESCRIPTION (provided by applicant): Fibroblast growth factor (FGF) signaling plays pleiotropic roles in mammalian development and metabolism, and disease. The paracrine FGF1, FGF4, FGF7, FGF8, and FGF9 subfamilies play essential roles in spermatogenesis, mesoderm induction, somitogenesis, organogenesis, and pattern formation, whereas the FGF19 subfamily acts in an endocrine fashion to regulate major metabolic processes including glucose, lipid, cholesterol, and bile acid metabolism, and phosphate/vitamin D homeostasis. The diverse activities of FGFs are transmitted by the FGF receptor (FGFR) subfamily of receptor tyrosine kinases (RTKs). Perturbed FGF signaling leads to numerous human diseases, including skeletal, reproductive syndromes, hearing loss, renal phosphate wasting, neurodegenerative disorders, and cancer. Several paracrine FGFs and all the endocrine FGFs are being pursued for drug development. The four specific aims of this competing renewal are: I. Characterize the structural basis by which epithelially-expressed FGF4 and FGF9 subfamilies attain their specificity towards mesenchymally-expressed FGFRc isoforms. II. Elucidate the structural basis by which a/bKlotho co-receptors promote signaling by the endocrine FGFs. III. Dissect the role of A-loop tyrosine phosphorylation in the hyperactivation of FGFR tyrosine kinase by pathogenic gain-of-function mutations. IV. Elucidate the structural basis by which FGFR recruits and phosphorylates FRS2a. Recombinant protein expression and engineering, x-ray crystallography, Surface Plasmon Resonance (SPR) spectroscopy, isothermal titration calorimetry (ITC), steady-state kinetics analysis, and time-resolved mass spectrometry will be used to accomplish the Specific Aims of this proposal. The structural and biophysical/biochemical results obtained will also be validated using cell- and animal-based assays. The data obtained under Aim I should provide molecular insights into the roles of paracrine FGFs in embryonic development and also facilitate the discovery of drugs for tissue repair and bioengineering, promotion of self- renewal and differentiation of human embryonic stem cells for cell-replacement therapy. The data generated under Aim II should enhance our understanding of the role of endocrine FGFs in human metabolism and provide blueprints for drug discovery for major human diseases including diabetes, obesity, hypercholesterolemia, colon cancer, and chronic kidney disease, most of which represent a huge burden on public health. The results of Aim III will enhance our understanding of the mechanism of action of pathogenic mutations in FGFRs and other RTKs as well as the regulation of tyrosine kinase activity of the entire RTK superfamily. Since substrate recruitment and phosphorylation by RTKs is a general event in RTK signaling, the mechanistic insights gained under Aim IV will also be directly applicable to the entire RTK superfamily.