Amsterdam University Medical Centers, university of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Amsterdam, The Netherlands.
Laboratory of Experimental Clinical Chemistry, Vesicle Observation Centre, Amsterdam University Medical Centers, Academic Medical Center at the University of Amsterdam, Amsterdam, The Netherlands.
PLoS One. 2019 Apr 4;14(4):e0213069. doi: 10.1371/journal.pone.0213069. eCollection 2019.
Extracellular vesicles (EVs) released by cells have a role in intercellular communication to regulate a wide range of biological processes. Two types of EVs can be recognized. Exosomes, which are released from multi-vesicular bodies upon fusion with the plasma membrane, and ectosomes, which directly bud from the plasma membrane. How cells regulate the quantity of EV release is largely unknown. One of the initiating events in vesicle biogenesis is the regulated transport of phospholipids from the exoplasmic to the cytosolic leaflet of biological membranes. This process is catalyzed by P4-ATPases. The role of these phospholipid transporters in intracellular vesicle transport has been established in lower eukaryotes and is slowly emerging in mammalian cells. In Caenorhabditis elegans (C. elegans), deficiency of the P4-ATPase member TAT-5 resulted in enhanced EV shedding, indicating a role in the regulation of EV release. In this study, we investigated whether the mammalian ortholog of TAT-5, ATP9A, has a similar function in mammalian cells. We show that knockdown of ATP9A expression in human hepatoma cells resulted in a significant increase in EV release that was independent of caspase-3 activation. Pharmacological blocking of exosome release in ATP9A knockdown cells did significantly reduce the total number of EVs. Our data support a role for ATP9A in the regulation of exosome release from human cells.
细胞释放的细胞外囊泡 (EV) 在细胞间通讯中发挥作用，可调节广泛的生物学过程。可以识别两种类型的 EV。外泌体是在多泡体与质膜融合时从多泡体中释放出来的，而ectosomes 则直接从质膜出芽。细胞如何调节 EV 释放的数量在很大程度上是未知的。囊泡生物发生的起始事件之一是磷脂从质膜的胞质小叶到质膜外小叶的受调控运输。这个过程由 P4-ATP 酶催化。这些磷脂转运蛋白在低等真核生物的细胞内囊泡运输中的作用已经确立，并且在哺乳动物细胞中正在缓慢出现。在秀丽隐杆线虫 (C. elegans) 中，P4-ATP 酶成员 TAT-5 的缺失导致 EV 脱落增加，表明其在 EV 释放的调节中发挥作用。在这项研究中，我们研究了哺乳动物 TAT-5 同源物 ATP9A 是否在哺乳动物细胞中具有类似的功能。我们发现，人肝癌细胞中 ATP9A 表达的敲低导致 EV 释放显著增加，这与 caspase-3 激活无关。在 ATP9A 敲低细胞中用药物阻断外泌体释放可显著减少 EV 的总数。我们的数据支持 ATP9A 在调节人细胞中外泌体释放中的作用。
