Products of endocytosis and autophagy are retrieved from axons by regulated retrograde organelle transport.-猫眼课题宝

DOI：

10.1083/jcb.121.2.305

发表时间：

1993-04

期刊：

The Journal of cell biology

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Hollenbeck PJ

来源链接：

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2200099/?report=classic

神经元的细胞内稳态要求蛋白质和膜的合成和顺行轴突运输通过它们的降解和逆行运输来平衡。为了解决培养的交感神经元中逆行运输的性质和调节，我分析了一类大的相致密细胞器的行为、组成和超微结构，其运动已被证明受到轴突生长的影响（Hollenbeck，P. J.，和D.布雷1987. 105：2827-2835）。在积极延长轴突这些细胞器进行顺行和逆行运动，引起无效的净逆行运输。这可能会转移到更有效的，更高的体积逆行运输停止轴突生长，或相反地转移到更大的顺行组件通过增加细胞内的环AMP浓度的效率较低的逆行运输。当神经元通过研磨加载德克萨斯红-葡聚糖时，自噬在72小时内将标记从整个神经元胞质溶胶的均匀分布清除为细胞体中的点状（推测为溶酶体）分布。在这个过程中，100%的相密细胞器是荧光的，表明它们含有从胞质溶胶中分离出来的物质，并表明它们将这种物质输送到细胞体。当这类细胞器的29个例子，通过光学显微镜，然后重新定位使用相关的电子显微镜，他们有一个相对恒定的超微结构组成的双层或多层界膜和细胞质内容物，自噬空泡的特点。当神经元通过生长锥的内吞作用从培养基中摄取荧光黄、FITC-葡聚糖或德克萨斯红-卵清蛋白时，100%的相致密细胞器变成荧光的，表明它们也含有内吞作用的产物。此外，用荧光内吞示踪剂进行的脉冲追踪实验证实，这些细胞器形成于轴突的最远端区域，并进行净逆行运输。定量比率成像与内吞的8-羟基芘-1，3，6-三磺酸显示，其内腔的平均pH值为7.05。这些结果表明，内吞和自噬途径合并在远端轴突，导致一类predegradative细胞器进行调节运输回细胞体。

Cellular homeostasis in neurons requires that the synthesis and anterograde axonal transport of protein and membrane be balanced by their degradation and retrograde transport. To address the nature and regulation of retrograde transport in cultured sympathetic neurons, I analyzed the behavior, composition, and ultrastructure of a class of large, phase-dense organelles whose movement has been shown to be influenced by axonal growth (Hollenbeck, P. J., and D. Bray. 1987. J. Cell Biol. 105:2827-2835). In actively elongating axons these organelles underwent both anterograde and retrograde movements, giving rise to inefficient net retrograde transport. This could be shifted to more efficient, higher volume retrograde transport by halting axonal outgrowth, or conversely shifted to less efficient retrograde transport with a larger anterograde component by increasing the intracellular cyclic AMP concentration. When neurons were loaded with Texas red- dextran by trituration, autophagy cleared the label from an even distribution throughout the neuronal cytosol to a punctate, presumably lysosomal, distribution in the cell body within 72 h. During this process, 100% of the phase-dense organelles were fluorescent, showing that they contained material sequestered from the cytosol and indicating that they conveyed this material to the cell body. When 29 examples of this class of organelle were identified by light microscopy and then relocated using correlative electron microscopy, they had a relatively constant ultrastructure consisting of a bilamellar or multilamellar boundary membrane and cytoplasmic contents, characteristic of autophagic vacuoles. When neurons took up Lucifer yellow, FITC-dextran, or Texas red-ovalbumin from the medium via endocytosis at the growth cone, 100% of the phase-dense organelles became fluorescent, demonstrating that they also contain products of endocytosis. Furthermore, pulse-chase experiments with fluorescent endocytic tracers confirmed that these organelles are formed in the most distal region of the axon and undergo net retrograde transport. Quantitative ratiometric imaging with endocytosed 8-hydroxypyrene-1,3,6- trisulfonic acid showed that the mean pH of their lumena was 7.05. These results indicate that the endocytic and autophagic pathways merge in the distal axon, resulting in a class of predegradative organelles that undergo regulated transport back to the cell body.