Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104.
Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
J Neurosci. 2022 Nov 9;42(45):8524-8541. doi: 10.1523/JNEUROSCI.1292-22.2022. Epub 2022 Sep 27.
Autophagy and endocytic trafficking are two key pathways that regulate the composition and integrity of the neuronal proteome. Alterations in these pathways are sufficient to cause neurodevelopmental and neurodegenerative disorders. Thus, defining how autophagy and endocytic pathways are organized in neurons remains a key area of investigation. These pathways share many features and converge on lysosomes for cargo degradation, but what remains unclear is the degree to which the identity of each pathway is preserved in each compartment of the neuron. Here, we elucidate the degree of intersection between autophagic and endocytic pathways in axons of primary mouse cortical neurons of both sexes. Using microfluidic chambers, we labeled newly-generated bulk endosomes and signaling endosomes in the distal axon, and systematically tracked their trajectories, molecular composition, and functional characteristics relative to autophagosomes. We find that newly-formed endosomes and autophagosomes both undergo retrograde transport in the axon, but as distinct organelle populations. Moreover, these pathways differ in their degree of acidification and association with molecular determinants of organelle maturation. These results suggest that the identity of autophagic and newly endocytosed organelles is preserved for the length of the axon. Lastly, we find that expression of a pathogenic form of α-synuclein, a protein enriched in presynaptic terminals, increases merging between autophagic and endocytic pathways. Thus, aberrant merging of these pathways may represent a mechanism contributing to neuronal dysfunction in Parkinson's disease (PD) and related α-synucleinopathies. Autophagy and endocytic trafficking are retrograde pathways in neuronal axons that fulfill critical degradative and signaling functions. These pathways share many features and converge on lysosomes for cargo degradation, but the extent to which the identity of each pathway is preserved in axons is unclear. We find that autophagosomes and endosomes formed in the distal axon undergo retrograde transport to the soma in parallel and separate pathways. These pathways also have distinct maturation profiles along the mid-axon, further highlighting differences in the potential fate of transported cargo. Strikingly, expression of a pathogenic variant of α-synuclein increases merging between autophagic and endocytic pathways, suggesting that mis-sorting of axonal cargo may contribute to neuronal dysfunction in Parkinson's disease (PD) and related α-synucleinopathies.
自噬和内吞作用是两种调节神经元蛋白质组组成和完整性的关键途径。这些途径的改变足以导致神经发育和神经退行性疾病。因此，确定自噬和内吞作用途径在神经元中是如何组织的仍然是一个关键的研究领域。这些途径有许多共同的特征，并在溶酶体中融合以降解货物，但仍不清楚每种途径在神经元的每个隔室中保持其身份的程度。在这里，我们阐明了雄性和雌性原代小鼠皮质神经元轴突中自噬和内吞途径之间的交叉程度。使用微流控室，我们标记了新生成的大体积内体和信号内体在轴突的远端，并系统地跟踪了它们相对于自噬体的轨迹、分子组成和功能特征。我们发现新形成的内体和自噬体都在轴突中逆行运输，但作为不同的细胞器群体。此外，这些途径在酸化程度和与细胞器成熟的分子决定因素的关联方面存在差异。这些结果表明，自噬体和新内吞的细胞器的身份在轴突的长度上得以保持。最后，我们发现一种致病性形式的α-突触核蛋白（一种富含突触前末端的蛋白质）的表达增加了自噬和内吞途径之间的融合。因此，这些途径的异常融合可能代表导致帕金森病 (PD) 和相关α-突触核蛋白病中神经元功能障碍的一种机制。自噬和内吞作用是神经元轴突中的逆行途径，它们具有重要的降解和信号功能。这些途径有许多共同的特征，并在溶酶体中融合以降解货物，但每种途径在轴突中的身份保持程度尚不清楚。我们发现，在远端轴突中形成的自噬体和内体以平行和独立的途径进行逆行运输到胞体。这些途径在轴突的中部也有不同的成熟特征，进一步突出了运输货物潜在命运的差异。引人注目的是，一种致病性α-突触核蛋白变体的表达增加了自噬和内吞途径之间的融合，表明轴突货物的错误分拣可能导致帕金森病 (PD) 和相关α-突触核蛋白病中的神经元功能障碍。
