Processing of HBsAg expressed by variceela-zosten virus

用水痘-带状疱疹病毒(VZV)表达乙肝表面抗原(HBs-Ag)，并用代谢抑制剂研究了表达的HBs-Ag颗粒的形态发生。通过N-连接、O-连接的糖基化和唾液酸化修饰乙肝表面抗原，并将其作为乙肝表面抗原形态发生过程中糖基化过程的标志物。用透射和免疫电子显微镜观察表面抗原的亚细胞定位和表面抗原颗粒形成。根据生化和形态结果，构建了乙肝表面抗原颗粒形态发生的模型。在粗面内质网(ER)中将乙肝表面抗原合成为26K蛋白，然后加入高甘露糖形成30K蛋白。具有26K-26K、26K-30K和30K-30K三种二硫键的二聚体被运输到顺式高尔基体区域的细胞质液泡中。表面抗原颗粒是由细胞质空泡中的表面抗原组装而成，而不是由含有表面抗原的跨膜前体萌发或挤出到内质网的管腔中形成的。空泡中的表面抗原颗粒在细胞质空泡流的运输过程中被高尔基器中的糖基化酶进一步加工，从高甘露糖转化为复合型糖，O-连接糖基化和唾液酸化在两个糖链中。然后，由30K-30K、30K-35K和35K-35K二聚体组成的完全加工的乙肝表面抗原颗粒可能通过胞吐作用分泌到细胞外空间。因此，VZV表达的乙肝表面抗原颗粒在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.