极化上皮细胞定向转运在个体发育与器官稳态维系过程中起重要作用。上皮细胞转运涉及内质网、高尔基体、线粒体、囊泡及细胞质膜等一系列动态互作反应，但其分子调控机制至今不甚清晰。ACAP4是我们实验室发现与鉴定的ARF6小GTP酶的重要调控蛋白，其在胃壁细胞质子泵与内因子的定向转运过程中起重要作用。我们最新的研究提示：ACAP4调节含质子泵囊泡的形成、组胺刺激胃酸分泌过程中同源囊泡的融合、管状囊泡与壁细胞顶膜的互作及质子泵在顶膜的锚定与胃酸分泌。本项目拟综合利用生物化学、细胞生物学、高分辨细胞器动态光谱成像技术与类器官模型体系，系统研究MST4-ACAP4-Acapin信号轴调控管状囊泡形成、定向转运及其与质膜互作的机制，并阐明幽门螺旋杆菌介导ACAP4翻译后异常修饰在胃壁细胞退行性疾病如萎缩性胃炎发生与发展中的病理机制。

Directional membrane transportation in polarized epithelial cells plays an important role in development and organ homeostasis. Epithelial cellular transport involves dynamic interactions among endoplasmic reticulum, Golgi apparatus, mitochondria and plasma membranes. However, the molecular mechanisms underlying the aforementioned dynamics remain elusive. Our laboratory has been engaged in polarized secretion in gastric parietal cells over a long period of time and uncovered an important regulator underlying dynamic interactions between tubulovesicular membranes and plasma membrane. ACAP4 is a GTPase-activating protein of ARF6 and regulates apical trafficking of H,K-ATPase and intrinsic factor. Our latest study suggested that ACAP4 regulates biogenesis of tubulovesicle and its interaction with apical plasma membrane in addition to homotypic vesicle fusion. This application aims to consolidate biochemical characterization, cell biological phenotyping with high-resolution of spectral imaging technology to model tubulovesicular membrane dynamics and its interaction with plasma membrane. The specific aims include the evaluation of the role of MST4-ACAP4-Acapin signaling axis in apical trafficking of H,K-ATPase, role of Helicobacter pylori in the post-translational modifications of ACAP4 and its relation to pathogenesis of atrophic gastritis.