Sfakianos Jeffrey N, Hunter Eric
Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Traffic. 2003 Oct;4(10):671-80. doi: 10.1034/j.1600-0854.2003.00126.x.
Cytoplasmic transport of Gag molecules to the site of budding is an important but poorly understand process in retroviral assembly. Our previous studies of Mason-Pfizer monkey virus showed that, for this retrovirus, Gag is assembled into capsids at a pericentriolar region and that Env is necessary for efficient transport out of the site. An Env requirement for cytoplasmic transport implicates vesicular trafficking in this process even though the capsids remain cytoplasmic and do not bud into intracellular compartments in the cells studied to date. We show here that the secretory pathway of the cell is not directly involved in Gag transport since the latter was not inhibited by BFA, nor did Gag colocalize with markers of the ER, Golgi, or TGN. Instead, colocalization was observed between Gag and endocytosed transferrin and with Rab11, suggesting that pericentriolar recycling endosomes play a critical role in this process. Mutants of Rab11 that inhibit efflux of transferrin from the recycling endosome also inhibited Gag transport. Our studies show that Env colocalizes with Gag at the pericentriolar assembly site, and provide evidence that Env must travel through this compartment in order to initiate export of the capsids from the site of assembly. Thus, for the first time, endocytic trafficking of a retroviral Env glycoprotein is linked to the efficient cytoplasmic transport of Gag.
在逆转录病毒组装过程中,Gag分子向出芽位点的细胞质运输是一个重要但却了解甚少的过程。我们之前对梅森 - 菲泽猴病毒的研究表明,对于这种逆转录病毒,Gag在中心粒周围区域组装成衣壳,并且Env对于从该位点有效运输出去是必需的。尽管在迄今为止所研究的细胞中衣壳仍保留在细胞质中且不会芽生到细胞内区室中,但Env对细胞质运输的需求暗示了在此过程中存在囊泡运输。我们在此表明细胞的分泌途径并不直接参与Gag运输,因为后者不受BFA抑制,Gag也不与内质网、高尔基体或反式高尔基体网络的标志物共定位。相反,观察到Gag与内吞的转铁蛋白以及Rab11共定位,这表明中心粒周围回收型内体在这个过程中起关键作用。抑制转铁蛋白从回收型内体流出的Rab11突变体也抑制了Gag运输。我们的研究表明Env在中心粒周围组装位点与Gag共定位,并提供证据表明Env必须穿过这个区室才能启动衣壳从组装位点输出。因此,首次将逆转录病毒Env糖蛋白的内吞运输与Gag的有效细胞质运输联系起来。