title: Dynamics and size of cross-linking-induced lipid nanodomains in model membranes.
abstract: Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin (CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Förster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of ~8 nm, which increases at higher Sph content. We observed two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation.
authors: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova, Prague, Czech Republic.
authors: Martin
authors: M
authors: Štefl
authors: Radek
authors: R
authors: Šachl
authors: Jana
authors: J
authors: Humpolíčková
authors: Marek
authors: M
authors: Cebecauer
authors: Radek
authors: R
authors: Macháň
authors: Marie
authors: M
authors: Kolářová
authors: Lennart B-Å
authors: LB
authors: Johansson
authors: Martin
authors: M
authors: Hof
mesh_terms: D002772:Cholera Toxin / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D005677:G(M1) Ganglioside / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D021962:Membrane Microdomains / Q000737:chemistry* / Q000648:ultrastructure*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition
chemical_list: D003432:Cross-Linking Reagents; D008051:Lipid Bilayers; D005677:G(M1) Ganglioside; D002772:Cholera Toxin