Valtersson C, Dutton A H, Singer S J
Department of Biology, University of California, San Diego, La Jolla 92093.
Proc Natl Acad Sci U S A. 1990 Oct;87(20):8175-9. doi: 10.1073/pnas.87.20.8175.
To examine aspects of the transfer of secretory proteins from the endoplasmic reticulum to the Golgi apparatus in situ, heterokaryons were formed between Hep G2 human hepatoma cells and WI-38 human fibroblasts. The cells were appropriately treated with cycloheximide before fusion, which emptied them of their respective secretory proteins, serum albumin for the Hep G2 cells and procollagen I for the WI-38 cells. After fusion was complete, the cycloheximide was washed out, protein synthesis was resumed, and the rates of reappearance of serum albumin and procollagen I in the two separated Golgi apparatuses within each heterokaryon were followed by immunofluorescence microscopy. Serum albumin was found to always reappear first in the Golgi apparatus contributed by the Hep G2 half of the heterokaryon, and procollagen I in the Golgi apparatus of the WI-38 half. These results suggest that the endoplasmic reticulum-to-Golgi apparatus transfer in situ is not simply a stochastic process but is either spatially restricted or exhibits cell-type specificity or both.
为了在原位研究分泌蛋白从内质网到高尔基体的转运过程，在人肝癌细胞Hep G2和人成纤维细胞WI-38之间形成了异核体。在融合前用环己酰亚胺对细胞进行适当处理，使它们各自的分泌蛋白排空，Hep G2细胞的分泌蛋白是血清白蛋白，WI-38细胞的是原胶原蛋白I。融合完成后，洗去环己酰亚胺，恢复蛋白质合成，通过免疫荧光显微镜观察每个异核体内两个分离的高尔基体中血清白蛋白和原胶原蛋白I重新出现的速率。发现血清白蛋白总是首先在异核体中来自Hep G2一半的高尔基体中重新出现，而原胶原蛋白I则在WI-38一半的高尔基体中重新出现。这些结果表明，原位内质网到高尔基体的转运不是一个简单的随机过程，而是要么在空间上受到限制，要么表现出细胞类型特异性，或者两者兼而有之。
