Fluorescence Correlation Spectroscopy Reveals Interaction of Some Microdomain-Associated Lipids with Cellular Focal Adhesion Sites

• Published in: International journal of molecular sciences 2020-10, Vol.21 (21), p.8149
• Main Authors: Kleusch, Christian, Monzel, Cornelia, Sridhar, Krishna Chander, Hoffmann, Bernd, Csiszár, Agnes, Merkel, Rudolf
• Format: Article
• Language: English
• Subjects: Animals; Cell Membrane - metabolism; Cells, Cultured; Cholesterol - metabolism; Embryo, Mammalian - cytology; Embryo, Mammalian - metabolism; Fluorescence; fluorescence correlation spectroscopy (FCS); focal adhesion site; Focal Adhesions; Lipid Bilayers - metabolism; lipid diffusion; Lipids - chemistry; liquid ordered and disordered phases; membrane microdomains; Membrane Microdomains - metabolism; model membrane; Myofibroblasts - cytology; Myofibroblasts - metabolism; Rats; Rats, Wistar; Spectrometry, Fluorescence - methods
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21218149

Cells adhere to the extracellular matrix at distinct anchoring points, mostly focal adhesions. These are rich in immobile transmembrane- and cytoskeletal-associated proteins, some of which are known to interact with lipids of the plasma membrane. To investigate their effect on lipid mobility and molecular interactions, fluorescently labeled lipids were incorporated into the plasma membranes of primary myofibroblasts using fusogenic liposomes. With fluorescence correlation spectroscopy, we tested mobilities of labeled microdomain-associated lipids such as sphingomyelin (SM), ganglioside (GM1), and cholesterol as well as of a microdomain-excluded phospholipid (PC) and a lipid-like molecule (DiIC (7)) in focal adhesions (FAs) and in neighboring non-adherent membrane areas. We found significantly slower diffusion of SM and GM1 inside FAs but no effect on cholesterol, PC, and DiIC (7). These data were compared to the molecular behavior in L /L -phase separated giant unilamellar vesicles, which served as a model system for microdomain containing lipid membranes. In contrast to the model system, lipid mobility changes in FAs were molecularly selective, and no particle enrichment occurred. Our findings suggest that lipid behavior in FAs cannot be described by L /L -phase separation. The observed slow-down of some molecules in FAs is potentially due to transient binding between lipids and some molecular constituent(s).