Sorbonne Université, Paris, France.
Paris Brain Institute, ICM, Paris, France.
PLoS Biol. 2023 Oct 23;21(10):e3002337. doi: 10.1371/journal.pbio.3002337. eCollection 2023 Oct.
The endoplasmic reticulum (ER) forms contacts with the lysosomal compartment, regulating lysosome positioning and motility. The movements of lysosomes are controlled by the attachment of molecular motors to their surface. However, the molecular mechanisms by which ER controls lysosome dynamics are still elusive. Here, using mouse brain extracts and mouse embryonic fibroblasts, we demonstrate that spatacsin is an ER-resident protein regulating the formation of tubular lysosomes, which are highly dynamic. Screening for spatacsin partners required for tubular lysosome formation showed spatacsin to act by regulating protein degradation. We demonstrate that spatacsin promotes the degradation of its partner AP5Z1, which regulates the relative amount of spastizin and AP5Z1 at lysosomes. Spastizin and AP5Z1 contribute to regulate tubular lysosome formation, as well as their trafficking by interacting with anterograde and retrograde motor proteins, kinesin KIF13A and dynein/dynactin subunit p150Glued, respectively. Ultimately, investigations in polarized mouse cortical neurons in culture demonstrated that spatacsin-regulated degradation of AP5Z1 controls the directionality of lysosomes trafficking. Collectively, our results identify spatacsin as a protein regulating the directionality of lysosome trafficking.
内质网（ER）与溶酶体隔室形成接触，调节溶酶体的定位和运动。溶酶体的运动受其表面附着的分子马达的控制。然而，内质网控制溶酶体动力学的分子机制仍不清楚。在这里，我们使用小鼠脑提取物和小鼠胚胎成纤维细胞证明了 spataxin 是一种内质网驻留蛋白，可调节管状溶酶体的形成，管状溶酶体具有高度动态性。筛选用于管状溶酶体形成的 spataxin 伴侣表明 spataxin 通过调节蛋白降解起作用。我们证明 spataxin 促进其伴侣 AP5Z1 的降解，从而调节溶酶体上 spastizin 和 AP5Z1 的相对含量。Spastizin 和 AP5Z1 通过与正向和反向运动蛋白 kinesin KIF13A 和 dynein/dynactin 亚基 p150Glued 相互作用，分别有助于调节管状溶酶体的形成及其运输。最终，在体外培养的极化小鼠皮质神经元中的研究表明，spataxin 调节的 AP5Z1 降解控制了溶酶体运输的方向性。总之，我们的研究结果确定了 spataxin 是一种调节溶酶体运输方向性的蛋白质。
