Endosome fission is essential for cargo sorting and targeting in the endosomal system. However, whether organelles other than the endoplasmic reticulum (ER) participate in endosome fission through membrane contacts is unknown. Here, we characterize a Golgi-derived vesicle, the SEC14L2 compartment, that plays a unique role in facilitating endosome fission through ternary contacts with endosomes and the ER. Localized to the ER-mediated endosome fission site, the phosphatidylinositol transfer protein SEC14L2 promotes phosphatidylinositol 4-phosphate (PtdIns4P) to phosphatidylinositol 3-phosphate (PtdIns3P) conversion before endosome fission. In the absence of SEC14L2, endosome fission is attenuated and more enlarged endosomes arise due to endosomal accumulation of PtdIns4P and reduction in PtdIns3P. Collectively, our data suggest roles of the Golgi network in ER-associated endosome fission and a mechanism involving ER–endosome contacts in the regulation of endosomal phosphoinositide conversion.

内体裂变对于内体系统中的货物分类和靶向至关重要。然而，内质网（ER）以外的细胞器是否通过膜接触参与内体裂变尚不清楚。在这里，我们描述了高尔基体衍生的囊泡，即 SEC14L2 区室，它通过与内体和 ER 的三元接触，在促进内体裂变方面发挥着独特的作用。磷脂酰肌醇转移蛋白 SEC14L2 位于 ER 介导的内体裂变位点，在内体裂变前促进 4-磷酸磷脂酰肌醇 (PtdIns4P) 转化为 3-磷酸磷脂酰肌醇 (PtdIns3P)。在缺乏 SEC14L2 的情况下，由于 PtdIns4P 的内体积累和 PtdIns3P 的减少，内体裂变减弱，并且出现更多增大的内体。总的来说，我们的数据表明高尔基体网络在 ER 相关内体裂变中的作用以及内质网磷酸肌醇转化调节中涉及 ER-内体接触的机制。