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Cell Research (2015) 25:412-428. 2015 IBCB, SIBS, CAS All rights reserved 1001-0602/15 www.nature.com/cr
ORIGINAL ARTICLE
Heparanase activates the syndecan-syntenin-ALIX exosome pathway
Bart Roucourt1, 2, Soe Meeussen1, 2, Jie Bao1, 2, Pascale Zimmermann2, 3, Guido David1
1Laboratory for Glycobiology and Developmental Genetics, Department of Human Genetics, KU Leuven, Leuven, B-3000, Belgium; 2Laboratory for Signal Integration in Cell Fate Decision, Department of Human Genetics, KU Leuven, Leuven, B-3000, Belgium; 3Centre de Recherche en Cancrologie de Marseille (CRCM), Aix-Marseille Universit, Marseille, F-13284, France; Inserm, U1068; Institut Paoli-Calmettes ; CNRS, UMR7258, Marseille, F-13009, France
Exosomes are secreted vesicles of endosomal origin involved in signaling processes. We recently showed that the syndecan heparan sulfate proteoglycans control the biogenesis of exosomes through their interaction with syntenin-1 and the endosomal-sorting complex required for transport accessory component ALIX. Here we investigated the role of heparanase, the only mammalian enzyme able to cleave heparan sulfate internally, in the syndecan-syntenin-ALIX exosome biogenesis pathway. We show that heparanase stimulates the exosomal secretion of syntenin-1, syndecan and certain other exosomal cargo, such as CD63, in a concentration-dependent manner. In contrast, exosomal CD9, CD81 and otillin-1 are not affected. Conversely, reduction of endogenous heparanase reduces the secretion of syntenin-1-containing exosomes. The ability of heparanase to stimulate exosome production depends on syntenin-1 and ALIX. Syndecans, but not glypicans, support exosome biogenesis in heparanase-exposed cells. Finally, heparanase stimulates intraluminal budding of syndecan and syntenin-1 in endosomes, depending on the syntenin-ALIX interaction. Taken together, our ndings identify heparanase as a modulator of the syndecan-syntenin-ALIX pathway, fostering endosomal membrane budding and the biogenesis of exosomes by trimming the heparan sulfate chains on syndecans. In addition, our data suggest that this mechanism controls the selection of specic cargo to exosomes.
Keywords: heparan sulfate; syndecan; heparanase; syntenin; exosome biogenesis; exosomal cargo Cell Research (2015) 25:412-428. doi:10.1038/cr.2015.29; published online 3 March 2015
Introduction
Exosomes are extracellular vesicles of endosomal origin, with a size ranging from 40 to 100 nm, secreted by cells. These vesicles contain various membrane and cytoplasmic components mRNA, miRNA, lipids, activated receptors, kinases and other proteins commonly designated as cargo. Transfer of cargo to recipient cells after the uptake of extracellular vesicles plays an important role in intercellular communication [1-3]. Although involved in many aspects of physiology and disease, the function...