Exosomes, new players in cell-cell communication, are extracellular vesicles of endocytic origin. Although single cells are known to release various kinds of exosomes (referred to as exosomal heterogeneity), very little is known about the mechanisms by which they are produced and released. Here, we established methods for studying exosomal heterogeneity by using polarized epithelial cells and showed that distinct types of exosomes are differentially secreted from the apical and basolateral sides. We also identified GPRC5C (G protein-coupled receptor class C group 5 member C) as an apical-exosome-specific protein. We further demonstrated that basolateral exosome release depends on ceramide, whereas ALIX, an ESCRT (endosomal sorting complexes required for transport)-related protein, not the ESCRT machinery itself, is required for apical exosome secretion. Thus, two independent machineries, the ALIX-Syntenin1-Syndecan1 machinery (apical side) and the sphingomyelinase-dependent ceramide production machinery (basolateral side), are likely to be responsible for the polarized exosome release from epithelial cells.

中文翻译：

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ALIX和神经酰胺差异控制极化外泌体从上皮细胞释放

外来体是细胞间通讯的新参与者，是内吞起源的细胞外囊泡。尽管已知单细胞释放各种外泌体（称为外泌体异质性），但对其产生和释放的机理了解甚少。在这里，我们建立了利用极化的上皮细胞研究外泌体异质性的方法，并显示出不同类型的外泌体从顶侧和基底外侧不同地分泌。我们还确定了GPRC5C（G蛋白偶联受体C类C组5成员C）为根尖外来体特异性蛋白。我们进一步证明了基底外侧外泌体的释放取决于神经酰胺，而ALIX是一种与ESCRT（运输所需的内体分拣复合体）相关的蛋白质，而不是ESCRT机制本身，顶端外泌体分泌是必需的。因此，两个独立的机器，ALIX-Syntenin1-Syndecan1机器（顶侧）和鞘磷脂酶依赖性神经酰胺生产机器（基底外侧），可能是极化外泌体从上皮细胞释放的原因。