Yabumoto Department of Intractable Disease Research, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, Japan.
Open Biol. 2020 Mar;10(3):190290. doi: 10.1098/rsob.190290. Epub 2020 Mar 11.
At least 150 human proteins are glycosylphosphatidylinositol-anchored proteins (GPI-APs). The protein moiety of GPI-APs lacking transmembrane domains is anchored to the plasma membrane with GPI covalently attached to the C-terminus. The GPI consists of the conserved core glycan, phosphatidylinositol and glycan side chains. The entire GPI-AP is anchored to the outer leaflet of the lipid bilayer by insertion of fatty chains of phosphatidylinositol. Because of GPI-dependent membrane anchoring, GPI-APs have some unique characteristics. The most prominent feature of GPI-APs is their association with membrane microdomains or membrane rafts. In the polarized cells such as epithelial cells, many GPI-APs are exclusively expressed in the apical surfaces, whereas some GPI-APs are preferentially expressed in the basolateral surfaces. Several GPI-APs act as transcytotic transporters carrying their ligands from one compartment to another. Some GPI-APs are shed from the membrane after cleavage within the GPI by a GPI-specific phospholipase or a glycosidase. In this review, I will summarize the current understanding of GPI-AP biosynthesis in mammalian cells and discuss examples of GPI-dependent functions of mammalian GPI-APs.
至少有 150 个人类蛋白质是糖基磷脂酰肌醇锚定蛋白（GPI-APs）。缺乏跨膜结构域的 GPI-AP 的蛋白质部分通过共价连接到 C 末端的 GPI 锚定到质膜上。GPI 由保守的核心聚糖、磷脂酰肌醇和聚糖侧链组成。整个 GPI-AP 通过插入磷脂酰肌醇的脂肪酸链插入脂质双层的外叶而锚定在脂质双层的外叶。由于 GPI 依赖性的膜锚定，GPI-APs 具有一些独特的特性。GPI-APs 的最突出特征是它们与膜微区或膜筏的关联。在极化细胞如上皮细胞中，许多 GPI-APs 仅在顶表面表达，而一些 GPI-APs 优先在基底外侧表面表达。一些 GPI-APs 作为转胞吞转运蛋白，将其配体从一个隔室携带到另一个隔室。一些 GPI-APs 在 GPI 内通过 GPI 特异性磷脂酶或糖苷酶切割后从膜上脱落。在这篇综述中，我将总结哺乳动物细胞中 GPI-AP 生物合成的当前理解，并讨论哺乳动物 GPI-AP 的 GPI 依赖性功能的例子。
