Endolysosomes are acidic organelles formed by the fusion of endosomes with lysosomes. In the presynaptic compartment they contribute to protein homeostasis, the maintenance of vesicle pools and synaptic stability. Here, we evaluated the mobility of endolysosomes found in axon terminals of olfactory sensory neurons of Xenopus tropicalis tadpoles. F-actin restricts the motion of these presynaptic acidic organelles which is characterized by a diffusion coefficient of 6.7 × 10^-3 μm²·s^-1 Local injection of secreted protein acidic and rich in cysteine (SPARC) in the glomerular layer of the olfactory bulb disrupts the structure of synaptic F-actin patches and increases the presence and mobility of endolysosomal organelles found in axon terminals. The increased motion of endolysosomes is localized to the presynaptic compartment and does not promote their access to axonal regions for retrograde transportation to the cell body. Local activation of synaptic degradation mechanisms mediated by SPARC coincides with a loss of the ability of tadpoles to detect waterborne odorants. Together, these observations show that the diffusion of presynaptic endolysosomes increases during conditions of synaptic remodelling to support their local degradative activity.

中文翻译：

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轴突末端控制内溶酶体扩散以支持突触重塑。

内溶酶体是由内体与溶酶体融合形成的酸性细胞器。在突触前区室中，它们有助于蛋白质稳态、囊泡池的维持和突触稳定性。在这里，我们评估了在热带非洲爪蟾蝌蚪的嗅觉感觉神经元的轴突末端中发现的内溶酶体的流动性。F-肌动蛋白限制这些突触前酸性细胞器的运动，其特征在于扩散系数为6.7 × 10 ^-3 μm ² ·s ^-1在嗅球的肾小球层局部注射酸性和富含半胱氨酸的分泌蛋白 (SPARC) 会破坏突触 F-肌动蛋白斑块的结构，并增加在轴突末端发现的内溶酶体细胞器的存在和流动性。内溶酶体的运动增加位于突触前区室，并不会促进它们进入轴突区域以逆行运输到细胞体。由 SPARC 介导的突触降解机制的局部激活与蝌蚪检测水性气味的能力的丧失相吻合。总之，这些观察表明突触前内溶酶体的扩散在突触重塑的条件下增加以支持它们的局部降解活性。