信号锚定蛋白Gab1调控肠上皮稳态与炎症性肠病的作用机制研究

Intestinal barrier dysfunction plays critical roles in the development and exacerbation of inflammatory bowel disease (IBD), indicating the importance in elucidating molecular targets shaping the function of intestinal epithelial cells (IECs) for understanding the IBD pathogenesis. Docking protein Gab1 integrates multiple signals, serving pivotal roles in the precise regulation of cell functions through the complex formed with protein kinase or phosphatase. Our recent study reveals that Gab1 protects mice from epithelial cell-mediated acute injury and abnormal repair. However, the role of Gab1 in intestine remains unclear. Our preliminary findings showed that Gab1 expression was decreased in intestinal tissues from IBD patients and DSS-treated mice compared with controls. Furthermore, Gab1 knockdown resulted in impaired tight junction expression in IECs, suggesting a potential role of Gab1 in regulating IEC function involved in IBD pathophysiology. Therefore, we generated IEC specific Gab1 knockout mice (Villin-Cre: Gab1flox/flox). Next, we will use colitis model based on genetic mice to further unveil the mechanism of Gab1-regulated IEC functions in IBD. The prospective results will be helpful to understand the pathogenesis of IBD, and also provide potential new perspective for the IBD diagnosis and treatments.

炎症性肠病（IBD）的发生与肠上皮屏障功能障碍引起的稳态失调密切相关，解析调控肠上皮细胞功能的分子靶点对于阐明IBD发病机制具有重要意义。Gab1是胞内关键锚定蛋白，与蛋白激酶/磷酸酶形成信号复合体参与精细的分子调控。本团队研究发现Gab1对于上皮细胞介导的损伤及异常修复具有保护作用，然而其是否参与生理及病理条件下对肠上皮细胞功能的调控目前尚无报道。预实验结果显示，Gab1在IBD患者肠粘膜以及结肠炎小鼠模型中表达明显下降；此外，敲降Gab1显著下调肠上皮细胞紧密连接蛋白的表达，提示Gab1可能通过调控肠上皮细胞功能参与IBD进程。因此本研究构建了肠上皮细胞Gab1条件性敲除小鼠（Villin-Cre: Gab1flox/flox），拟利用该遗传学模型深入解析Gab1调控肠上皮细胞的具体功能、信号通路及其介导IBD病理生理过程的作用机制。预期结果将有助于为临床诊疗策略提供新思路和理论依据。

肠上皮屏障功能障碍是炎症性肠病（IBD）疾病进程中的核心环节，因此解析调控肠上皮细胞功能的分子靶点对于阐明IBD发病机制具有重要意义。胞内关键锚定蛋白Gab1，能够响应多种细胞因子刺激，招募蛋白激酶/磷酸酶形成信号复合体参与精细的分子调控。本团队研究发现Gab1在IBD患者肠粘膜以及结肠炎小鼠模型中表达明显下降；在DSS诱导的小鼠肠炎模型中，肠上皮细胞Gab1条件性敲除小鼠（VillinCre-Gab1flox/flox）更为易感，而髓系细胞Gab1条件性敲除小鼠（LysMCre-Gab1flox/flox）则无明显差异。我们发现，肠上皮细胞Gab1敲除小鼠肠道屏障通透性增加，炎症浸润加剧。进一步研究显示，Gab1是维持肠上皮细胞稳态的重要分子：Gab1通过与RIPK3结合，抑制RIPK1/RIPK3/MLKL信号的过度活化，而当Gab1敲降/缺失时，T/S/Z刺激下则会引起RIPK1/RIPK3/MLKL高度磷酸化，肠上皮细胞继而发生坏死性凋亡，加重屏障破坏及肠道炎症。最后，利用RIPK3的酶活抑制剂GSK872给药能够显著地缓解DSS诱导的Gab1缺失小鼠的结肠炎表型，进一步验证了Gab1通过抑制肠上皮细胞坏死性凋亡进而维持肠道稳态的关键作用，有助于为临床诊疗策略提供新思路和理论依据。