Specificities of exosome versus small ectosome secretion revealed by live intracellular tracking of CD63 and CD9

Abstract Despite their roles in intercellular communications, the different populations of extracellular vesicles (EVs) and secretion mechanisms are not fully characterized: how to what extent EVs form as intraluminal endocytic compartments (exosomes), or at plasma membrane (PM) (ectosomes) remains unclear. Here we follow intracellular trafficking EV markers CD9 CD63 from endoplasmic reticulum residency compartment, respectively PM late endosomes. We observe transient co-localization both places, before they finally segregate. a mutant stabilized more abundantly released than CD63. Thus, HeLa cells, ectosomes prominent exosomes. By comparative proteomic analysis differential response neutralization endosomal pH, identify few surface proteins likely specific either exosomes (LAMP1) (BSG, SLC3A2). Our work sets path for molecular functional discrimination small any cell type.