Linstedt A D, Kelly R B
Division of Neuroscience, University of California, San Francisco 94143-0534.
Neuron. 1991 Aug;7(2):309-17. doi: 10.1016/0896-6273(91)90269-6.
The targeting of synaptophysin, a major synaptic vesicle protein, in transfected nonneuronal cells has important implications for synaptic vesicle biogenesis, but has proved controversial. We have analyzed four transfected cell types by differential centrifugation and velocity gradient sedimentation to determine whether synaptophysin is targeted to endosomes or to synaptic vesicle-like structures. Synaptophysin was recovered only in vesicles that sedimented more rapidly than synaptic vesicles. The synaptophysin-containing vesicles were labeled if a surface-labeled cell was warmed to 37 degrees C, comigrated with transferrin receptor-containing vesicles on velocity and density gradients, and could be completely immunoadsorbed by anti-LDL receptor tail antibodies. These data demonstrate that synaptophysin was targeted to the early endocytotic pathway in the transfected cells and are inconsistent with the suggestion that synaptophysin expression induces a novel population of vesicles. Targeting of synaptophysin to early endosomes implicates their role in synaptic vesicle biogenesis.
在转染的非神经元细胞中，主要突触囊泡蛋白突触素的靶向作用对突触囊泡生物发生具有重要意义，但已证明存在争议。我们通过差速离心和速度梯度沉降分析了四种转染细胞类型，以确定突触素是否靶向内体或突触囊泡样结构。突触素仅在沉降速度比突触囊泡更快的囊泡中回收。如果将表面标记的细胞加热到37摄氏度，含突触素的囊泡会被标记，在速度和密度梯度上与含转铁蛋白受体的囊泡共同迁移，并且可以被抗低密度脂蛋白受体尾部抗体完全免疫吸附。这些数据表明，突触素在转染细胞中靶向早期内吞途径，这与突触素表达诱导新的囊泡群体的观点不一致。突触素靶向早期内体暗示了它们在突触囊泡生物发生中的作用。
