Locker J K, Opstelten D J, Ericsson M, Horzinek M C, Rottier P J
Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
J Biol Chem. 1995 Apr 14;270(15):8815-21. doi: 10.1074/jbc.270.15.8815.
The mouse hepatitis virus M protein is a triple spanning membrane glycoprotein that, when expressed independently, localizes to trans-Golgi as well as to the trans-Golgi network (TGN). Passage of this protein from the endoplasmic reticulum through the intermediate compartment to the late Golgi and TGN can be conveniently followed by analyzing its O-linked sugars. Using pulse-chase analyses we studied the oligomerization of the M protein in sucrose gradients. The Golgi and TGN forms migrated as large heterogeneous complexes, whereas the endoplasmic reticulum and intermediate compartment forms of the protein appeared to migrate as monomer. Moreover, a mutant of the M protein lacking the 22 COOH-terminal amino acids, that is transported to the plasma membrane, gave rise to similar complexes, albeit smaller in size, that persisted at the plasma membrane. We propose that the trans-Golgi/TGN retention of the MHV-M protein is governed by two mechanisms: oligomerization possibly mediated by the transmembrane domains and binding of its cytoplasmic tail to cellular factors in trans Golgi/TGN.
小鼠肝炎病毒M蛋白是一种跨膜三次的糖蛋白，当它独立表达时，定位于反式高尔基体以及反式高尔基体网络（TGN）。通过分析其O-连接糖，可以方便地追踪该蛋白从内质网经中间区室到晚期高尔基体和TGN的转运过程。我们使用脉冲追踪分析在蔗糖梯度中研究了M蛋白的寡聚化。高尔基体和TGN形式的M蛋白以大型异质复合物形式迁移，而内质网和中间区室形式的该蛋白似乎以单体形式迁移。此外，缺少22个COOH末端氨基酸且被转运到质膜的M蛋白突变体，产生了类似的复合物，尽管尺寸较小，且在质膜上持续存在。我们提出，MHV-M蛋白在反式高尔基体/TGN的滞留受两种机制控制：可能由跨膜结构域介导的寡聚化及其胞质尾巴与反式高尔基体/TGN中细胞因子的结合。
