ezrin相关信号通路调控上皮细胞定向运输的分子机理研究

Gastric parietal cells undergo the translocation of intrinsic factor and proton pump and acid secretion which provides a great model system to illustrate the molecular mechanisms of polarized cells directional transportation. Significant progress has been made toward a better understanding of the activation process of the parietal cell, but many important issue remain to be resolved regarding the molecular mechanisms underlying proton pump directional translocation and apical membrane skeleton rearrangement. Our earlier research showed that ezrin and its post-translational modification plays an important role in directional transport of proton pump in the parietal cell activation process. Further analysis demonstrated ACAP4, a novel ARF6 specific GAP, associated with cell membrane and actin cytoskeleton through the interaction with ezrin. Our recent work suggests that the BAR domain and phosphorylation of ACAP4 play an important role in the regulation of cell plasma membrane plasticity. In order to elucidate the regulatory mechanism of the ezrin related signaling pathways during the directed transportation procedure of polarized epithelial cells, we will precisely explore the molecular and regulatory mechanisms of the interaction of ezrin and its interaction partners（including ACAP4 and ARF6）. Further studies of the Ezrin related signal pathway will help us enrich the theory of the regulatory mechanism of epithelial cell plasticity，which also provide a theoretical basis for the clinical related diseases such as stomach ulcer and gastric carcinoma.

哺乳动物的胃壁细胞具质子泵转位及泌酸功能，是经典研究极化细胞定向运输的模式体系。壁细胞酸分泌的生化过程已初见端倪，但质子泵定向移动及壁细胞顶膜骨架重排的分子机制及动态过程研究尚需进一步深入。我们已报道了ezrin及其翻译后修饰在壁细胞活化过程中质子泵定向运输有重要作用，并发现ARF6激活蛋白ACAP4通过其与ezrin的相互作用联接细胞质膜与微丝骨架，近期工作表明ACAP4的BAR结构域及其磷酸化修饰在细胞质膜可塑性调控中起着重要作用。为了阐明ezrin相关信号通路的调控机制，我们拟结合实验动物学、分子遗传学及生物光子学技术和手段，详尽研究ezrin翻译后修饰及其与ACAP4等蛋白相互作用的分子机理，并系统阐明这些蛋白相互作用在调控胃壁细胞极化定向运输过程中的功能。本课题的完成不仅在阐明上皮细胞定向转运调控分子机制上具有重要的理论价值，同时亦可为相关疾病(如：幽门螺杆菌感染乃至胃癌)的治疗提供理论依据。

胃壁细胞执行了内因子和质子泵向顶膜移动及分泌盐酸的功能，是经典的研究极化细胞定向运输的模式体系，但质子泵定向移动及壁细胞顶膜重排的调控分子机制尚需深入。我们的前期研究揭示了ezrin及其蛋白质翻译后修饰在壁细胞活化过程中质子泵定向运输的重要作用，为了进一步阐明ezrin相关信号通路在极化上皮细胞定向运输中的生物学功能和调节机制，我们结合先进的原子力显微镜技术及细胞生理学研究，详尽分析了Ser66磷酸化对ezrin分子构象的改变，证实了磷酸化ezrin与Stx3作用的结构基础，证明了ezrin与Stx3以构象依赖的方式结合，而且这种结合是管状囊泡向顶膜转运所必需的。我们还揭示了PKA蛋白激酶与MST4激酶协同作用，分别协调了组胺刺激胃酸分泌过程中ezrin的这两个不同位点-Ser66及Thr567的磷酸化作用，阐明了PKA-MST4-ezrin信号通路参与极化上皮细胞定向运输调控的分子机制。这不仅在阐明上皮细胞可塑性调控分子机制上具有重要的理论价值，同时亦可为纠正相关疾病(如：胃溃疡、幽门螺杆菌感染乃至胃癌)的治疗医药学提供理论依据。