Processing of HBsAg expressed by variceela-zosten virus

用水痘-带状疱疹病毒（VZV）表达B型肝炎表面抗原（HBsAg），并用代谢抑制剂研究了表达HBsAg颗粒的形态发生。通过N-连接和O-连接的糖基化和唾液酸化修饰HBsAg，并将其用作HBsAg形态发生中糖基化过程的标志物。透射和免疫电镜观察用于确定HBsAg的亚细胞定位和HBsAg颗粒形成。生化和形态学结果被用来构建HBsAg颗粒的形态发生模型。HBsAg在粗面内质网（ER）中合成为26 K蛋白，然后加入高甘露糖聚糖形成30 K蛋白。三种含二硫键的二聚体（26 K-26 K、26 K-30 K和30 K-30 K）被运输到顺式高尔基体的胞质液泡中。HBsAg颗粒是由HBsAg在胞质空泡中组装而成的，而不是由含HBsAg的transmemrane前体出芽或挤出到内质网腔中而形成的。空泡中的HBsAg颗粒在通过胞质空泡流转运到细胞表面的过程中，被高尔基体中的糖基化酶进一步加工;从高甘露糖聚糖到复合型聚糖的转化、O-连接糖基化和两种聚糖中的唾液酸化。然后，由30 K-30 K、30 K-35 K和35 K-35 K二聚体组成的完全加工的HBsAg颗粒可能通过胞吐分泌到细胞外空间。因此，VZV表达的HBsAg颗粒在其形态发生和糖基化方面具有新的特征。

Hepatitis B surface antigen (HBsAg) was expressed by varicella-zoster virus (VZV) and morphogenesis of expressed HBsAg particles was studied by using metabolic inhibitors. HBsAg was modified by N-linked and O-linked glycosylation, and sialylation, and these were used for the markers of glycosylation process in the morphogenesis of HBsAg. Transmission and immunoelectron microscopic observations were used to identify the subcellular localization of HBsAg and HBsAg particle formation. Biochemical and morphological results were used to construct a model for morphogenesis of HBsAg particles. HBsAg was synthesized as 26K protein in the rough endoplasmic reticulum (ER) and then the high mannose glycan was added to form 30K protein. Three kinds of dimers with disulfide bonds 26K-26K, 26K-30K, and 30K-30K, were transported into the cytoplasmic vacuoles of the cis Golgi area. HBsAg particles were formed by the assembly of HBsAg in the cytoplasmic vacuoles and were not formed by budding or extrusion of transmemrane precursor containing HBsAg into the lumen of the ER.HBsAg particles in the vacuoles were further processed by glycosylation enzymes in the Golgi apparatus during transport to the cell surface by the cytoplasmic vacuolar flow ; conversion from the high mannose glycan to the complex type glycan, O-linked glycosylation, and sialylation in both glycans. Then fully processed HBsAg particles composed of 30K-30K, 30K-35K, and 35K-35K dimers were secreted into extracellular space possibly by exocytosis. Thus HBsAg particles expressed by VZV had novel features in its morphogenesis and glycosylation.