Rack1调控Hh信号通路的机理研究

Hedgehog (Hh) pathway plays important roles in controlling embryonic development and adult tissue homeostasis. Aberrant activity of Hh pathway results in birth defect and tumorigenesis. When the pathway is closed, the transcription factor Ci is anchored in the cytoplasm by a microtubule-associated protein Cos2, culminating in ubiquitination-mediated Ci degradation. Contrarily, when the pathway is open, Ci translocates into the nucleus to activate target gene expression. To date, the mechanisms of Hh signal regulating the localization and stability of Ci protein is still unclear. We found that Rack1 inhibits Hh pathway activity through promoting Ci destabilization. Biochemical results show that Rack1 can interact with Ci and Cos2. Furthermore, the interactions between Rack1 and Ci or Cos2 are modulated by Hh signal. Since Rack1 is a scaffold protein, we propose that Hh regulates Ci localization and stability via modulating the association/dissociation of Ci-Rack1-Cos2 complex. In this study, we will study how Rack1 regulates Hh signaling transduction using Drosophila model, and try to illustrate the mechanisms by which Hh controls Ci localization and stability. This research will strengthen our understanding on Hh pathway. Meanwhile, it also provides theoretical basis for study of Hh-related organ development.

Hedgehog（Hh）信号通路在调控胚胎发育和成体组织稳态中起着重要作用，其活性的异常会导致发育缺陷及肿瘤发生。在通路关闭状态下，转录因子Ci被微管相关蛋白Cos2锚定在细胞质中被泛素化降解；反之，在通路开启状态下，Ci蛋白进入细胞核激活靶基因表达。目前，对Hh信号调控Ci蛋白定位及稳定性的机制，仍不清楚。我们发现Rack1促进Ci的降解，进而抑制Hh信号通路活性。生化实验结果证明，Rack1和Ci及Cos2存在相互作用，且它们之间的相互作用受到Hh信号的调控。鉴于Rack1作为支架蛋白，我们推测Hh信号通过调节Ci-Rack1-Cos2蛋白复合体的结合/解离，调控Ci蛋白的定位及稳定性。本项目以果蝇为模式生物，开展Rack1在Hh信号转导中的作用机理研究，以期阐明Hh信号调控Ci蛋白定位和稳定性的机制。该研究将加深对Hh信号通路的理解，也对研究Hh通路相关的昆虫器官发育提供理论基础。

Hedgehog（Hh）信号通路在调控胚胎发育和成体组织稳态中起着重要作用，其活性的异常会导致发育缺陷及肿瘤发生。在通路关闭状态下，转录因子Ci被微管相关蛋白Cos2锚定在细胞质中被泛素化降解；反之，在通路开启状态下，Ci蛋白进入细胞核激活靶基因表达。目前，对Hh信号调控Ci蛋白定位及稳定性的机制仍不清楚。我们发现Rack1促进Ci的降解，进而抑制Hh信号通路靶基因的活性。进一步通过生化实验结果证明，Rack1和Ci及Cos2存在相互作用，且它们之间的相互作用受到Hh信号的调控。此外，发现Rack1能促进Ci的泛素化及讲解。鉴于Rack1作为支架蛋白，我们推测Hh信号通过调节Ci-Rack1-Cos2蛋白复合体的结合/解离，调控Ci蛋白的定位及稳定性。本项目以果蝇为模式生物，开展了Rack1在Hh信号转导中的作用机理研究，阐明了Hh信号调控Ci蛋白定位和稳定性的机制。该研究将加深对Hh信号通路的理解，也对研究Hh通路相关的昆虫器官发育提供理论基础。