ALIX and ceramide differentially control polarized exosome release from epithelial cells

Abstract

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.

Molecular and functional profiling of apical versus basolateral small extracellular vesicles derived from primary human proximal tubular epithelial cells under inflammatory conditions

“…In this study, Matsui et al. provided evidence of distinct mechanisms of exosome production in polarized cells – that is, apical and basolateral exosome release mediated by ALIX‐Syntenin1‐Syndecan1 and ceramides respectively (Matsui et al., 2020). Further investigation of these mechanisms in human primary PTEC will enable the targeted modulation of sEV production within diseased kidneys.…”

“…Of note, we also identified significantly elevated numbers of apical sEV compared with basolateral sEV under both normal homeostatic and inflammatory conditions. These quantitative differences between apical and basolateral membranes may be reflective of independent pathways of sEV/exosome biogenesis, as proposed in a recent study of polarized exosome release from epithelial cells (Matsui et al., 2020). In this study, Matsui et al.…”