Takatsu Hiroyuki, Katoh Yohei, Ueda Tomoko, Waguri Satoshi, Murayama Takashi, Takahashi Senye, Shin Hye-Won, Nakayama Kazuhisa
Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Cell Struct Funct. 2013;38(1):31-41. doi: 10.1247/csf.12028. Epub 2013 Jan 16.
Upon cell division, not only cells themselves but also their organelles undergo drastic shape changes, although the behaviors of organelles other than the Golgi apparatus remain poorly understood. We followed the spatiotemporal changes in the localization of transferrin receptor (TfnR) and other proteins. In early mitotic phases, a population of proteins cycling through the endocytic recycling compartment (ERC) exhibits a distinct spatiotemporal change from that of Golgi proteins. In prophase/prometaphase, when the cell surface-to-volume ratio is reaching its minimum, the ERC proteins are transiently assembled around the centrated centrosome in a microtubule- and dynein-dependent manner, and soon separated polewards into two clusters concomitant with separation of duplicated centrosomes. Electron microscopic analysis revealed that endosomal vesicles containing endocytosed transferrin cluster tightly around centrosomes without fusing with one another. As cytokinesis proceeds, the clusters gradually collapse, and the ERC proteins reassemble around the furrowing equatorial region. FRAP (fluorescence recovery after photobleaching) analyses of EGFP-TfnR-expressing cells revealed minimal membrane exchange between the endosomal clusters and other cellular compartments until anaphase/telophase, when membrane traffic resumes. Our observations indicate that ERC clustering around centrosomes plays a fundamental role in restricting membrane delivery to the plasma membrane during early mitotic phases, when the cell surface-to-volume ratio reaches its minimum.
在细胞分裂时，不仅细胞自身，其细胞器也会发生剧烈的形态变化，尽管除高尔基体之外的细胞器行为仍知之甚少。我们追踪了转铁蛋白受体（TfnR）和其他蛋白质定位的时空变化。在有丝分裂早期阶段，一群穿梭于内吞循环区室（ERC）的蛋白质呈现出与高尔基体蛋白质不同的独特时空变化。在前期/前中期，当细胞表面与体积之比达到最小值时，ERC蛋白质以微管和动力蛋白依赖的方式短暂地聚集在集中的中心体周围，并随着复制的中心体分离而很快向两极分离成两个簇。电子显微镜分析显示，含有内吞转铁蛋白的内体小泡紧密聚集在中心体周围，彼此不融合。随着胞质分裂的进行，这些簇逐渐解体，ERC蛋白质在正在缢缩的赤道区域周围重新聚集。对表达EGFP-TfnR的细胞进行的荧光漂白后恢复（FRAP）分析表明，直到后期/末期膜运输恢复之前，内体簇与其他细胞区室之间的膜交换极少。我们的观察结果表明，在细胞表面与体积之比达到最小值的有丝分裂早期阶段，中心体周围的ERC聚集在限制膜向质膜的递送中起基本作用。
