选择性激活FGFR1发挥代谢调控作用FGF1改构体的分子设计与功能验证

Due to the metabolic regulation activity via activation of FGFR1, fibroblast growth factor 1 (FGF1) has emerged as a promising drug for diabetes mellitus and other metabolic disease. However, the innate characteristic of mitogenic activity became the primary obstacle to clinical application. Previously, we generated a FGF1 variant preserved the capacity of metabolic regulation and displayed a major loss in mitogenic activity. To test the potential clinical utility, we did toxicology study in both cynomolgus monkeys and C57BL/6J mice and found bladder lesions in both animal models. Lots of evidences revealed that the abnormal activation of FGFR2-FGFR4 lead to bladder lesions, even cancer. Thus, the side effect of FGF1 variant on bladder which observed in monkeys and mouse might due to the non-selective activation of FGFRs. Since the N termini determined the receptor binding specificity of FGFR2-FGFR4 instead of FGFR1, we supposed that selective activation of FGFR1 could be achieved by molecular design in which FGF1 variant only retained metabolic regulation. This project will testify the selective receptor binding characteristic and safety at molecular level and combined with in vivo and in vitro studies. Then, we will explore the precise mechanism of FGF1 on metabolic regulation. Our research aims to provide new strategies and theoretical insight for clinical translation of FGF1 variant target on diabetes and drug design of other growth factors with potential therapeutic value.

FGF1通过FGFR1发挥的代谢调控作用使其成为糖尿病等代谢性疾病的候选治疗药物，但潜在的促增殖活性限制了进一步临床转化。我们前期构建的非促分裂型FGF1在保留代谢调控能力的同时基本丧失了促增殖活性，然而在食蟹猴和小鼠毒理学实验中发现其会导致膀胱组织病变。大量研究表明FGFR2-FGFR4的异常激活是膀胱病变的重要内因，因此我们猜想FGF1及其改构体的膀胱毒副作用与其无选择性激活FGFRs相关。鉴于FGF1的N端是其与FGFR2-FGFR4而非FGFR1结合的决定性区域，本课题拟基于配体结构决定受体选择性这一特征，通过分子设计获得特异性激活FGFR1的非促分裂型FGF1改构体。多层面系统研究该改构体的受体选择性及安全性；并以该改构体为抓手，探索FGF1代谢调控的精准机制。通过本课题的实施，有望为糖尿病治疗候选新药的获得提供理论依据，并为其他生长因子类蛋白药物的设计改良提供新思路和新策略。

FGF1作为一种新近发现的代谢调控因子，具有胰岛素增敏、降低血糖和缓解代谢性疾病等多种作用。FGF1发挥其生物学活性依赖于FGFR二聚化进而激活的下游级联网络，特别是FGFR1是其发挥代谢调控功能的关键受体。然而，非选择性激活FGFR2、FGFR3和FGFR4导致的膀胱毒性成为其在长期应用过程中的安全隐患。因此，如何通过分子设计获得更具安全性且保留全部代谢调控功能的FGF1改构体成为加速其临床转化的关键节点。根据课题组前期提出的FGFR受体二聚化理论，本项目基于结构分析并结合FGF1-FGFR-肝素三元复合物结构，构建出选择性激活FGFR1的FGF1ΔHBSΔNT。通过表面等离子共振、PLA邻位连接技术和免疫印记等实验表明FGF1ΔHBSΔNT对FGFR1的选择性激活。进一步的体内实验表明，相较于野生型、N末端截短和肝素结合位点突变的FGF1改构体，FGF1ΔHBSΔNT不会促进膀胱组织的异常增殖。进一步的研究表明肌肉和脂肪组织共同介导了FGF1ΔHBSΔNT对血糖的调控作用。在肌肉组织中，FGF1ΔHBSΔNT通过激活AMPK促进Glut4的细胞膜转位进而发挥降糖租用；而在脂肪组织中，FGF1ΔHBSΔNT通过抑制CCL2的表达减少巨噬细胞浸润进而缓解脂肪组织的胰岛素抵抗。本项目不仅为生长因子类配体改造和药物设计提供了新的思路，也为糖尿病等代谢性疾病的治疗提供了新的候选药物。