Spectroscopic Analysis of Lateral and
Transbilayer Fluidity of Exosome Membranes
Posted on 24.11.2022 - 13:33
Exosomes are small extracellular vesicles (sEVs) involved in distal cell–cell communication and cancer migration by transferring functional cargo molecules. Membrane domains similar to lipid rafts are assumed to occur in exosome membranes and are involved in interactions with target cells. However, the bilayer membrane properties of these small vesicles have not been fully investigated. Therefore, we examined the fluidity, lateral domain separation, and transbilayer asymmetry of exosome membranes using fluorescence spectroscopy. Although there were some differences between the exosomes, TMA-DPH anisotropy showing moderate lipid chain order indicated that ordered phases comprised a significant proportion of exosome membranes. Selective TEMPO quenching of the TMA-DPH fluorescence in the liquid-disordered phase indicated that 40–50% of the exosome membrane area belonged to the ordered phase based on a phase-separated model. Furthermore, NBD-PC in the outer leaflet showed longer fluorescence lifetimes than those in the inner leaflets. Therefore, the exosome membranes maintained transbilayer asymmetry with a topology similar to that of the plasma membranes. In addition, the lateral and transbilayer orders of exosome membranes obtained from different cell lines varied, probably depending on the different membrane lipid components and compositions partially derived from donor cells. As these higher membrane orders and asymmetric topologies are similar to those of cell membranes with lipid rafts, raft-like functional domains are possibly enriched on exosome membranes. These domains likely play key roles in the biological functions and cellular uptake of exosomes by facilitating selective membrane interactions with target organs.
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Yasuda, Tomokazu; Watanabe, Hirofumi; Hirosawa, Koichiro M.; Suzuki, Kenichi G. N.; Suga, Keishi; Hanashima, Shinya (2022): Fluorescence Spectroscopic Analysis of Lateral and Transbilayer Fluidity of Exosome Membranes. ACS Publications. Collection. https://doi.org/10.1021/acs.langmuir.2c02258
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Koichiro M. Hirosawa
Kenichi G. N. Suzuki
selective tempo quenchingordered phases comprisedlike functional domainscompositions partially derivedbilayer membrane properties40 – 50higher membrane ordersfluorescence spectroscopic analysisordered phase baseddisordered phase indicatedexosome membranes obtainedsmall extracellular vesiclesmembrane domains similarlateral domain separationexosome membranes exosomesexosome membranessmall vesiclestransbilayer ordersdph fluorescenceplasma membranescell membranestransbilayer asymmetrytopology similartarget organstarget cellssignificant proportionseparated modelprobably dependingpossibly enrichedlipid raftsinner leafletsfully investigateddonor cellscellular uptakecancer migrationbiological functionsasymmetric topologies