Analysis of a mutant exhibiting conditional sorting to dense core secretory granules in Tetrahymena thermophila.
Analysis of a mutant exhibiting conditional sorting to dense core secretory granules in Tetrahymena thermophila.
复制标题
对嗜热四膜虫致密核心分泌颗粒表现出条件分选的突变体的分析。
DOI：
10.1093/genetics/159.4.1605
复制
发表时间：
2001
期刊：
影响因子：
3.3
通讯作者：
Turkewitz,AP
中科院分区：
文献类型：
--
作者：
Bowman,GR;Turkewitz,AP
致密核颗粒（DCGs）的形成既需要从其他分泌蛋白中分选颗粒内容物，也需要分选后的成熟过程。四膜虫嗜热菌株SB281不能合成DCGs，先前的分析表明缺陷存在于分选步骤或分选步骤附近。由于该菌株是该途径中极少数突变体之一，因此我们对其表型进行了更完整的研究。遗传上位分析将该缺陷置于另外两个四膜虫突变体的上游。利用免疫荧光检测颗粒含量蛋白，以及GFP标记，我们描述了一个新的细胞质室，颗粒含量可以在生长的SB281细胞中进行分类。细胞融合实验表明，该隔室不是DCG合成的生物合成中间体。SB281中的排序与生长有很强的条件关系。当细胞处于饥饿状态时，储存室被降解，新合成的颗粒蛋白被迅速分泌。因此，SB281突变似乎在分选和成熟水平上影响DCG合成。
The formation of dense core granules (DCGs) requires both the sorting of granule contents from other secretory proteins and a postsorting maturation process. TheTetrahymena thermophilastrain SB281 fails to synthesize DCGs, and previous analysis suggested that the defect lay at or near the sorting step. Because this strain represents one of the very few mutants in this pathway, we have undertaken a more complete study of the phenotype. Genetic epistasis analysis places the defect upstream of those in two other characterized Tetrahymena mutants. Using immunofluorescent detection of granule content proteins, as well as GFP tagging, we describe a novel cytoplasmic compartment to which granule contents can be sorted in growing SB281 cells. Cell fusion experiments indicate that this compartment is not a biosynthetic intermediate in DCG synthesis. Sorting in SB281 is strongly conditional with respect to growth. When cells are starved, the storage compartment is degraded andde novosynthesized granule proteins are rapidly secreted. The mutation in SB281 therefore appears to affect DCG synthesis at the level of both sorting and maturation.