Golgi dispersal during microtubule disruption: Regeneration of Golgi stacks at peripheral endoplasmic reticulum exit sites
Golgi dispersal during microtubule disruption: Regeneration of Golgi stacks at peripheral endoplasmic reticulum exit sites
复制标题
DOI：
10.1091/mbc.7.4.631
复制
发表时间：
1996-04-01
影响因子：
3.3
通讯作者：
LippincottSchwartz, J
中科院分区：
文献类型：
--
作者：
Cole, NB;Sciaky, N;LippincottSchwartz, J
微管断裂对高尔基体正常的中心体定位有显著影响，高尔基体元素仍然是有能力的功能单位，但在细胞质中经历了可逆的“断裂”和分散。在本研究中，我们使用数字荧光图像处理显微镜结合生化和超微结构方法分析了这一过程。微管解聚后，高尔基膜组分被重新分布到不同数量的外周位点，这些外周位点不是随机分布的，而是与蛋白质从内质网出口的位点相对应。虽然高尔基酶在几个小时内逐渐重新分布到这些外周部位，但ERGIC-53（一种在内质网和高尔基体之间循环的蛋白质）在首次通过内质网后迅速（在15分钟内）重新分布到这些部位。在重新分配之前，从内质网输出的蛋白质的高尔基酶加工被抑制，只有在高尔基酶重新分配到外周内质网出口位点后，高尔基酶才能恢复到正常水平。研究微管破坏对连接内质网和高尔基体的膜通路的影响的实验表明，它们在扩散过程中可能起作用。微管破坏后，外周前高尔基体元素未能聚集到中心体区域，高尔基体到内质网膜的再循环仅受到轻微抑制。此外，阻碍高尔基到er循环的条件完全阻止了高尔基破碎。基于这些发现，我们提出高尔基驻留蛋白通过与ERGIC-53相同的ER/高尔基循环途径缓慢但组成的通量是微管解聚时高尔基分散的基础。ERGIC-53和高尔基蛋白都会聚集在外周内质网出口位点，因为这些位点的膜无法聚集到中心体区域。这些外周部位的高尔基堆积再生将重建内质网进入高尔基复体的分泌流，并导致高尔基分散。
Microtubule disruption has dramatic effects on the normal centrosomal localization of the Golgi complex, with Golgi elements remaining as competent functional units but undergoing a reversible ''fragmentation'' and dispersal throughout the cytoplasm. In this study we have analyzed this process using digital fluorescence image processing microscopy combined with biochemical and ultrastructural approaches. After microtubule depolymerization, Golgi membrane components were found to redistribute to a distinct number of peripheral sites that were not randomly distributed, but corresponded to sites of protein exit from the ER. Whereas Golgi enzymes redistributed gradually over several hours to these peripheral sites, ERGIC-53 (a protein which constitutively cycles between the ER and Golgi) redistributed rapidly (within 15 minutes) to these sites after first moving through the ER. Prior to this redistribution, Golgi enzyme processing of proteins exported from the ER was inhibited and only returned to normal levels after Golgi enzymes redistributed to peripheral ER exit sites where Golgi stacks were regenerated. Experiments examining the effects of microtubule disruption on the membrane pathways connecting the ER and Golgi suggested their potential role in the dispersal process. Whereas clustering of peripheral pre-Golgi elements into the centrosomal region failed to occur after microtubule disruption, Golgi-to-ER membrane recycling was only slightly inhibited. Moreover, conditions that impeded Golgi-to-ER recycling completely blocked Golgi fragmentation. Based on these findings we propose that a slow but constitutive flux of Golgi resident proteins through the same ER/Golgi cycling pathways as ERGIC-53 underlies Golgi dispersal upon microtubule depolymerization. Both ERGIC-53 and Golgi proteins would accumulate at peripheral ER exit sites due to failure of membranes at these sites to cluster into the centrosomal region. Regeneration of Golgi stacks at these peripheral sites would re-establish secretory flow from the ER into the Golgi complex and result in Golgi dispersal.