Hyenne Vincent, Apaydin Ahmet, Rodriguez David, Spiegelhalter Coralie, Hoff-Yoessle Sarah, Diem Maxime, Tak Saurabh, Lefebvre Olivier, Schwab Yannick, Goetz Jacky G, Labouesse Michel
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Development and Stem Cells Program, Centre National de la Recherche Scientifique (UMR7104), Institut National de la Santé et de la Recherche Médicale (U964), Université de Strasbourg, 67400 Illkirch, France MN3T, Institut National de la Santé et de la Recherche Médicale (U1109), LabEx Medalis, Université de Strasbourg, 67200 Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg, 67200 Strasbourg, France
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Development and Stem Cells Program, Centre National de la Recherche Scientifique (UMR7104), Institut National de la Santé et de la Recherche Médicale (U964), Université de Strasbourg, 67400 Illkirch, France.
J Cell Biol. 2015 Oct 12;211(1):27-37. doi: 10.1083/jcb.201504136.
Exosomes are secreted vesicles arising from the fusion of multivesicular bodies (MVBs) with the plasma membrane. Despite their importance in various processes, the molecular mechanisms controlling their formation and release remain unclear. Using nematodes and mammary tumor cells, we show that Ral GTPases are involved in exosome biogenesis. In Caenorhabditis elegans, RAL-1 localizes at the surface of secretory MVBs. A quantitative electron microscopy analysis of RAL-1-deficient animals revealed that RAL-1 is involved in both MVB formation and their fusion with the plasma membrane. These functions do not involve the exocyst complex, a common Ral guanosine triphosphatase (GTPase) effector. Furthermore, we show that the target membrane SNARE protein SYX-5 colocalizes with a constitutively active form of RAL-1 at the plasma membrane, and MVBs accumulate under the plasma membrane when SYX-5 is absent. In mammals, RalA and RalB are both required for the secretion of exosome-like vesicles in cultured cells. Therefore, Ral GTPases represent new regulators of MVB formation and exosome release.
外泌体是由多泡体（MVBs）与质膜融合产生的分泌性囊泡。尽管它们在各种过程中都很重要，但控制其形成和释放的分子机制仍不清楚。利用线虫和乳腺肿瘤细胞，我们发现Ral GTP酶参与外泌体生物发生。在秀丽隐杆线虫中，RAL-1定位于分泌性MVBs的表面。对RAL-1缺陷动物的定量电子显微镜分析表明，RAL-1参与MVB的形成及其与质膜的融合。这些功能不涉及外被体复合物，一种常见的Ral鸟苷三磷酸酶（GTP酶）效应器。此外，我们发现靶膜SNARE蛋白SYX-5与组成型活性形式的RAL-1在质膜处共定位，并且当SYX-5缺失时，MVBs在质膜下积累。在哺乳动物中，RalA和RalB都是培养细胞中分泌外泌体样囊泡所必需的。因此，Ral GTP酶代表了MVB形成和外泌体释放的新调节因子。
