Partoens P, Slembrouck D, Quatacker J, Baudhuin P, Courtoy P J, De Potter W P
Department of Medicine, University of Antwerp, Antwerpen, Belgium.
J Cell Sci. 1998 Mar;111 ( Pt 6):681-9. doi: 10.1242/jcs.111.6.681.
Two storage compartments in cultured noradrenergic neurons derived from the superior cervical ganglion from fetal pig have been defined using sucrose density gradient centrifugation and electron microscopy: (1) large dense-cored vesicles (LDV) contain noradrenaline and dopamine-beta-hydroxylase (DbetaH); (2) small electron-lucent vesicles contain acetylcholine and p38 and represent the noradrenergic small synaptic vesicles (SSV); no small dense-cored vesicles (SDV) could be detected. Our results demonstrate that internalized LDV membrane constituents are retrieved into early endosomes, as shown by the colocalization of retrieved DbetaH with the endosomal markers Rab5 and HRP in sucrose density gradients and on confocal microscopical images. Recycling of the SSV membranes via an endosomal intermediate is also confirmed in noradrenergic neurons. Finally, colocalization of retrieved DbetaH and retrieved p38 in stimulated neurons indicates that the two sets of constituents intermix. These data provide the first experimental evidence for a common early endosome in which SSV and LDV membrane constituents are internalized after exocytosis and imply that endosomal sorting is an important process for the generation of different secretory vesicles in the noradrenergic nerve terminal.
利用蔗糖密度梯度离心法和电子显微镜，已确定来自胎猪颈上神经节的培养去甲肾上腺素能神经元中有两个储存区室：（1）大的致密核心囊泡（LDV）含有去甲肾上腺素和多巴胺-β-羟化酶（DβH）；（2）小的电子透明囊泡含有乙酰胆碱和p38，代表去甲肾上腺素能小突触囊泡（SSV）；未检测到小的致密核心囊泡（SDV）。我们的结果表明，内化的LDV膜成分被回收至早期内体，这在蔗糖密度梯度和共聚焦显微镜图像中，回收的DβH与内体标记物Rab5和辣根过氧化物酶（HRP）的共定位中得到了证实。去甲肾上腺素能神经元中也证实了SSV膜通过内体中间体进行循环利用。最后，在受刺激的神经元中回收的DβH和回收的p38的共定位表明这两组成分会混合。这些数据为共同的早期内体提供了首个实验证据，在该内体中，SSV和LDV膜成分在胞吐作用后被内化，这意味着内体分选是去甲肾上腺素能神经末梢中产生不同分泌囊泡的重要过程。
