IGFBP-3是一种多功能蛋白，既有IGF依赖性和也有IGF非依赖性作用。申请人研究发现IGFBP-3的IGF非依赖性作用之一是通过结合BMP配体、抑制BMP信号的转导来实现。人体内存在两种天然的IGFBP-3的酶解片断1-98和1-212，它们与IGF结合能力有所减弱，但它们是否具有IGF非依赖性作用以及是否与BMP信号通路有关还不清楚。本项目将在PC-3细胞中研究两种IGFBP-3酶解片断的IGF非依赖性作用，用Ligand印迹确定这两种酶解片断与BMP配体的结合能力，在U2OS细胞以及模式动物斑马鱼中研究两种IGFBP-3酶解片断体外和体内对BMP信号转导的作用，比较IGFBP-3两种酶解片断与完整片断三者之间的功能异同。最终解析IGFBP-3酶解片断生理功能和作用机制。本项目的研究对我们进一步了解IGFBP-3的作用机制，以及IGFBP-3在临床上用于疾病的诊断和治疗具有指导意义。

Genetic and clinical research observations suggest that the insulin-like growth factor (IGF) signaling pathway plays a fundamental role in regulating animal growth and development as well as in maintaining adult homeostasis. IGF binding protein-3 (IGFBP-3) is the major binding protein of IGFs in the bloodstream. IGFBP-3 is a multiple functional protein that has IGF-dependent and -independent actions in cultured mammalian cells. It has become widely appreciated that IGF-independent actions of IGFPB-3 contribute to improving the pathophysiology of human desease, such as cancer, diabetes, and malnutritions. Previously, we found that IGFBP-3 exerts its IGF-independent function by antagonizing BMP signaling in vitro and in vivo. Interestingly, two IGFBP-3 fragments, 1-98 and 1-212, were isolated from human hemofiltrate, and found that they have reduced IGF binding activity. But whether they have IGF-independent action and whether the can antagonizing BMP signaling in vitro and in vivo are still unknown. In this study, the IGF bind domain of IGFBP-3 fragment 1-98 and 1-212 will be mutated. The IGF- - independent action of the two fragments will be studied on PC-3 cells by determining the pro-apoptotic activities. The BMP ligand binding activity of the two fragments will be tested by ligand blotting. The in vitro and in vivo effect of the two fragments on BMP signaling will be investigated in U2OS cells and zebrafish model system, respectively. Eventually, we are going to reveal the physiological function and the mechanistic action of IGFPB-3 fragments. A better understanding of the molecular basis underlying IGFBP-3's actions will not only further our knowledge of IGFBP-3 physiology but may also lead to future strategies for diagnosing and treating or circumventing human diseases.