内质网中ppGalNAc-T18的功能机制研究

From our traditional understanding, mucin type O-glycosylation is regulated by ppGalNAc-Ts located in Golgi. Changes of O-glycosylation are closely related to many diseases, and its regulation mechanism is popular in current international research. We have recently discovered a new subfamily of ppGalNAc-Ts, including ppGalNAc-T18, which was only expressed in vertebrates and had no catalytic activity. The ppGalNAc-T18 is located in endoplasmic reticulum (ER), it was found up-regulated expressed in mice inflammatory model, involved in apoptosis, and obviously influenced the O-glycosylation level. These phenomenons showed that ppGalNAc-T18 might have a significantly different function from other ppGalNAc-Ts. In this project, we will focus on functional study of ppGalNAc-T18 in ER. Based on the phenomenon that we had found in inflammatory stress, apoptotic pathway and O-glycosylation change, we plan to systematically study the O-glycosylation mechanism of ppGalNAc-T18 in ER using methods of glycobiology, biochemistry and cell biology. We hope our research could provide new ideas for comprehensive understanding the role of mucin type O-glycosylation in life.

目前教科书上经典蛋白质O-GalNAc初始糖基化修饰是由定位于高尔基体的ppGalNAc-T糖基转移酶调控形成的。蛋白质O-糖基化变化与众多复杂性疾病的发生密切相关，其调控机制研究是目前国际关注的研究热点。我们发现了一组起源于脊椎动物，没有经典酶活的新亚型基因。其中的ppGalNAc-T18定位于内质网，在炎症小鼠模型中呈现应激表达上调，参与细胞凋亡并影响细胞糖基化等功能现象。提示该分子具有与已知的ppGalNAc-T成员不同的新功能。本课题将以解析ppGalNAc-T18在细胞内质网的生物学功能为研究目的，从其在炎症应激反应，细胞凋亡通路和O-糖基化调控的研究角度出发，通过运用糖生物学，生物化学，细胞生物学等研究手段，系统研究内质网中ppGalNAc-T18对蛋白质O-GalNAc糖基化调控机制，为进一步全面理解蛋白质O-GalNAc糖基化在生命活动中的作用提供新见解。

粘蛋白型O-糖基化是重要的蛋白质翻译后修饰，参与了众多生理过程。粘蛋白型O-糖基化是由N-乙酰氨基半乳糖基转移酶（ppGalNAc-Ts）催化起始反应形成Tn糖链结构。ppGalNAc-Ts家族有20个成员，其中ppGalNAc-T18是仅存在于脊椎动物中，在组织中广泛表达且在以脑肺组织呈现高表达。ppGalNAc-T18主要定位于细胞内质网中，不具有经典的糖基转移酶活性。因此揭示ppGAlNAc-T18的分子功能机制，对深刻理解粘蛋白型O-糖基化在生命活动中的功能具有重要意义。本项目通过分子细胞学和糖生物学研究手段围绕ppGalNAc-T18的生物学功能机制展开研究。我们发现ppGalNAc-T18在炎症刺激下发生应激性上调表达，细胞学和炎症小鼠的模型研究表明ppGalNAc-T18对内质网应激反应、细胞存活和细胞的O-糖基化水平均具有明显的调节作用。这种调控作用是通过ppGalNAc-T18的非酶活性分子机制调控发生的。本研究首次揭示了炎症过程中ppGalNAc-T18和O-糖基化修饰对内质网应激反应的调控作用，确定ppGalNAc-T18的非酶活功能，及其与内质网应激反应调节分子间的相互作用，提出了一种糖基化介导的新的炎症与内质网应激反应调控模式。