title: Detachment of breast tumor cells induces rapid secretion of exosomes which subsequently mediate cellular adhesion and spreading.
abstract: Exosomes are nano-vesicles secreted by a wide range of mammalian cell types. These vesicles are abundant in serum and other extracellular fluids and contain a large repertoire of proteins, mRNA and microRNA. Exosomes have been implicated in cell to cell communication, the transfer of infectious agents, and neurodegenerative diseases as well as tumor progression. However, the precise mechanisms by which they are internalized and/or secreted remain poorly understood. In order to follow their release and uptake in breast tumor cells in real time, cell-derived exosomes were tagged with green fluorescent protein (GFP)-CD63 while human serum exosomes were rhodamine isothiocynate-labeled. We show that detachment of adherent cells from various substrata induces a rapid and substantial secretion of exosomes, which then concentrate on the cell surfaces and mediate adhesion to various extracellular matrix proteins. We also demonstrate that disruption of lipid rafts with methyl-beta-cyclodextrin (MβCD) inhibits the internalization of exosomes and that annexins are essential for the exosomal uptake mechanisms. Taken together, these data suggest that cellular detachment is accompanied by significant release of exosomes while cellular adhesion and spreading are enhanced by rapid uptake and disposition of exosomes on the cell surface.
authors.affiliation: Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, Tennessee, United States of America.
authors.forename: Rainelli B
authors.initials: RB
authors.lastname: Koumangoye
authors.forename: Amos M
authors.initials: AM
authors.lastname: Sakwe
authors.forename: J Shawn
authors.initials: JS
authors.lastname: Goodwin
authors.forename: Tina
authors.initials: T
authors.lastname: Patel
authors.forename: Josiah
authors.initials: J
authors.lastname: Ochieng
mesh_terms: D017302:Annexins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D055354:Exosomes / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D017302:Annexins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin