A live cell reporter of exosome secretion and uptake reveals pathfinding behavior of migrating cells

• Published in: Nature communications 2020-04, Vol.11 (1), p.2092-15, Article 2092
• Main Authors: Sung, Bong Hwan, von Lersner, Ariana, Guerrero, Jorge, Krystofiak, Evan S., Inman, David, Pelletier, Roxanne, Zijlstra, Andries, Ponik, Suzanne M., Weaver, Alissa M.
• Format: Article
• Language: English
• Subjects: 13/31; 14; 14/19; 14/28; 14/35; 14/63; 14/69; 631/1647/245/2225; 631/80/313; 631/80/84; 64/60; Acidification; Amino Acid Sequence; Autocrine signalling; Biology; Biosynthesis; CD63 antigen; Cell culture; Cell Line, Tumor; Cell lines; Cell migration; Cell Movement; Cell Survival; Exosomes; Exosomes - metabolism; Exosomes - ultrastructure; Extracellular Space - metabolism; Extracellular vesicles; Fluorescence; Green Fluorescent Proteins - metabolism; Humanities and Social Sciences; Humans; Life cycle analysis; Monitoring; multidisciplinary; Multivesicular Bodies - metabolism; Multivesicular Bodies - ultrastructure; Mutagenesis; Mutation; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Paracrine signalling; pH effects; Phenotypes; Plasma; Proteins; Science; Science (multidisciplinary); Secretion; Tetraspanin 30 - chemistry; Tetraspanin 30 - metabolism; Time Factors
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-15747-2

Small extracellular vesicles called exosomes affect multiple autocrine and paracrine cellular phenotypes. Understanding the function of exosomes requires a variety of tools, including live imaging. Our previous live-cell reporter, pHluorin-CD63, allows dynamic subcellular monitoring of exosome secretion in migrating and spreading cells. However, dim fluorescence and the inability to make stably-expressing cell lines limit its use. We incorporated a stabilizing mutation in the pHluorin moiety, M153R, which now exhibits higher, stable expression in cells and superior monitoring of exosome secretion. Using this improved construct, we visualize secreted exosomes in 3D culture and in vivo and identify a role for exosomes in promoting leader–follower behavior in 2D and 3D migration. Incorporating an additional non-pH-sensitive red fluorescent tag allows visualization of the exosome lifecycle, including multivesicular body (MVB) trafficking, MVB fusion, exosome uptake and endosome acidification. This reporter will be a useful tool for understanding both autocrine and paracrine roles of exosomes. A prior live-cell exosome reporter showed dim fluorescence and could not be expressed stably, limiting its usefulness. Here the authors stabilise the reporter to allow long-term tracking of exosomes, and incorporate a second fluorophore to visualise the entire exosome lifecycle.