Molecular Membrane Biology Laboratory, RIKEN Advanced Science Institute, Wako, Saitama, Japan.
J Cell Sci. 2012 Jul 15;125(Pt 14):3412-20. doi: 10.1242/jcs.100065. Epub 2012 Mar 30.
Protein export from the endoplasmic reticulum (ER) to the Golgi apparatus occurs at specialized regions known as the ER exit sites (ERES). In Saccharomyces cerevisiae, ERES appear as numerous scattered puncta throughout the ER. We examined ERES within the peripheral ER, finding that the proteins comprising the ERES localize on high-curvature ER domains where curvature-stabilizing protein Rtn1 is present. Δrtn1 Δrtn2 Δyop1 cells have fewer high-curvature ER domains, but ERES accumulate at the remaining high-curvature ER domains on the edge of expanded ER sheets. We propose that membrane curvature is a key geometric feature for the regulation of ERES localization. We also investigated a spatial relationship between ERES and Golgi cisternae. Golgi cisternae in S. cerevisiae are unstacked, dispersed, and moving in the cytoplasm with cis-cisternae positioned adjacent to ERES, whereas trans-cisternae are not. Morphological changes in the ER of Δrtn1 Δrtn2 Δyop1 cells resulted in aberrant Golgi structures, including cis- and trans-markers, and there was reduced movement at ERES between expanded ER sheets and the plasma membrane.
蛋白质从内质网（ER）输出到高尔基体发生在称为内质网出口部位（ERES）的特化区域。在酿酒酵母中，ERES 表现为内质网中许多分散的小点。我们在内质网的外周检查了 ERES，发现构成 ERES 的蛋白质定位于存在曲率稳定蛋白 Rtn1 的高曲率内质网域上。Δrtn1 Δrtn2 Δyop1 细胞的高曲率内质网域较少，但 ERES 在扩展内质网片边缘的剩余高曲率内质网域上聚集。我们提出，膜曲率是调节 ERES 定位的关键几何特征。我们还研究了 ERES 和高尔基体潴泡之间的空间关系。酿酒酵母中的高尔基体潴泡未堆叠、分散并在细胞质中移动，顺面潴泡位于 ERES 附近，而反面潴泡则不位于附近。Δrtn1 Δrtn2 Δyop1 细胞内质网的形态变化导致高尔基体结构异常，包括顺面和反面标记物，并且在扩展内质网片和质膜之间的 ERES 之间的运动减少。
