Matsuoka Y, Chen S Y, Compans R W
Department of Microbiology and Immunology, Emory University, Atlanta, Georgia 30322.
J Biol Chem. 1994 Sep 9;269(36):22565-73.
The G1 and G2 glycoproteins of Punta Toro virus, a member of the bunyaviruses, are targeted to the Golgi complex, where viral budding occurs. We found that the G1 protein, when expressed in the absence of G2, is also targeted to the Golgi complex. A series of G1 proteins truncated at the carboxyl-terminal region was constructed, and the localization of the expressed proteins was examined. It was found that the proteins expressed from constructs with partial deletions in the cytoplasmic domain were transported to the Golgi complex at a significantly slower rate than G1. Although a major fraction of these proteins was eventually transported to the Golgi complex, they did not exhibit as clearly defined a pattern of accumulation as G1, but rather appeared to be distributed throughout the endoplasmic reticulum as well as the Golgi complex. The proteins expressed from constructs lacking most of the cytoplasmic domain and, in some cases, part of the transmembrane domain sequences as well were transported to the cell surface. We have also constructed chimeric proteins with the envelope protein of a murine leukemia virus (MCFenv), which is efficiently transported to the plasma membrane. A MCF-G1 chimera that contained the G1 transmembrane and cytoplasmic domains was found to be efficiently retained in the Golgi complex, and a construct that contained only the G1 transmembrane domain was also partially retained in the Golgi complex. Thus, the transmembrane domain as well as a portion of the cytoplasmic domain adjacent to the transmembrane domain are apparently crucial for Golgi retention of the G1 protein.
蓬塔托罗病毒是布尼亚病毒的一种，其G1和G2糖蛋白定位于高尔基体复合体，病毒在此出芽。我们发现，在没有G2的情况下表达的G1蛋白也定位于高尔基体复合体。构建了一系列在羧基末端区域截短的G1蛋白，并检测了所表达蛋白的定位。结果发现，在细胞质结构域有部分缺失的构建体所表达的蛋白转运至高尔基体复合体的速度明显慢于G1。尽管这些蛋白中的大部分最终被转运至高尔基体复合体，但它们没有表现出与G1一样明确的积累模式，而是似乎分布于整个内质网以及高尔基体复合体中。缺乏大部分细胞质结构域以及在某些情况下还缺乏部分跨膜结构域序列的构建体所表达的蛋白被转运至细胞表面。我们还构建了与鼠白血病病毒包膜蛋白（MCFenv）的嵌合蛋白，该蛋白能有效地转运至质膜。发现含有G1跨膜和细胞质结构域的MCF-G1嵌合体有效地滞留于高尔基体复合体中，而仅含有G1跨膜结构域的构建体也部分滞留于高尔基体复合体中。因此，跨膜结构域以及与跨膜结构域相邻的部分细胞质结构域显然对G1蛋白滞留于高尔基体至关重要。
