GPI锚定蛋白的运输与细胞极性生长机制研究

Polarity is a common feature of various eukaryotic cells. One of the key factors that affect the polarized growth of cells is polarized transportation of the secretory proteins. Glycosylphosphatidylinositol (GPI) anchoring, a post-translational modification of proteins by glycolipid, plays an important role in the sorting and transportation of proteins. Many GPI-anchored proteins are transported to the apical side in several types of polarized epithelial cells and to the neuronal axon that corresponds to the apical side. Indeed, it has been reported that re-modeling of the GPI glycolipid and glycosylation of the GPI-anchored proteins are involved in sorting of these proteins in Golgi apparatus, however, its mechanism keeps unknown. We have found that Aspergillus fumigatus, a filamentous fungi that causes a severe infection in human, exhibited a failure in transportation of the GPI-anchor proteins and a severe defect in polarized growth when processing of the GPI sugar chain or protein N-glycan was blocked. In aim to reveal the role of the GPI anchoring and protein glycosylation in protein transportation and polarized growth, we plan to focus on the A. fumigatus GPI-anchored proteins to investigate the influence, mechanism, and regulation of their GPI-anchoring and glycosylation in sorting and transportation of these proteins..This proposed project will deepen our understanding of the mechanism of glycolipid-mediated protein transportation and polarized growth. Also, this research will provide new targets for the development of anti-fungal drugs. 8-10 research articles from this proposed project will be published and 5-8 Ph.D. students will be trained.

细胞极性是多种不同类型真核细胞的共同特征，其重要特征或影响因素之一，就是分泌蛋白在细胞内的定向运输。蛋白质的GPI糖脂修饰在蛋白质的分拣、运输中发挥重要的作用；在哺乳动物细胞中，许多GPI蛋白被运输到上皮细胞的顶端一侧和神经元触突。有研究表明，GPI糖脂的重构和糖基化修饰与GPI蛋白在高尔基体中的分拣相关，但具体机制还不清楚。本实验室前期对病原真菌烟曲霉的研究发现，当GPI糖脂中的糖链或蛋白质部分的N-糖链的加工发生缺陷时，突变株中GPI蛋白的运输发生缺陷，表现出显著的极性生长异常。为揭示蛋白质的GPI修饰和糖基化修饰调控蛋白质运输及细胞极性生长的分子机制，我们拟以烟曲霉GPI蛋白为研究核心，开展GPI糖脂和糖基化修饰对GPI-AP分拣与运输的影响、机制及调控研究。.本项目的开展将有助于我们深入理解蛋白质的糖脂修饰介导的蛋白质运输及细胞极性生长机制，同时为抗真菌感染新药的开发提供理论依据。

蛋白质的GPI修饰在蛋白质的分拣、运输及细胞极性生长过程中发挥重要的作用，本实验室前期对病原真菌烟曲霉的研究发现，当GPI糖脂中的糖链或蛋白质部分的N-糖链的加工发生缺陷时，突变株中GPI蛋白的运输发生缺陷，表现出显著的极性生长异常。本项目中我们对GPI修饰和糖基化修饰调控蛋白质运输及细胞极性生长的分子机制进行了研究，我们的研究发现：（1）糖蛋白在高尔基体中的分拣与分泌依赖于N-糖基化修饰，并且N-糖链依赖的糖蛋白分拣与分泌具有种属特异性，干扰高尔基体的N-糖链加工过程可提高真菌的蛋白分泌量。（2）发现Emp47负责蛋白酶、酯酶、糖苷酶等分泌糖蛋白从内质网到高尔基体的运输，而Vip36则负责将从内质网中泄漏到高尔基体的分子伴侣等糖蛋白反向运输到内质网，从而维持内质网的稳态。系统地鉴定了Emp47和Vip36所识别分拣的潜在货物蛋白，揭示了N-糖链依赖的细胞内糖蛋白分拣与运输机制。（3）证明GPI糖链的磷酸乙醇胺修饰是保证细胞壁糖蛋白正确分拣、运输及定位的关键步骤；GPI修饰可影响烟曲霉细胞壁结构，从而显著改变烟曲霉在宿主中的免疫应答。.通过本项目研究的实施，揭示了烟曲霉细胞极性生长所需要的功能糖蛋白的定向运输是通过N-糖基化修饰和GPI修饰来调控的。这些研究结果为真菌感染的诊断和治疗奠定了科学基础，同时也丰富了对真核生物细胞内糖蛋白运输和细胞极性生长机制的认识。.项目主要研究结果已发表SCI论文5篇、特邀综述1篇，在国际或地区学术会议上做特邀报告3次，全国会议上做报告4次，培养研究生5名。