Martin Hof (Heyrovský Institute, Prague), Lipid driven nanodomains are fluid and interleaflet coupled

It is a fundamental question whether sphingomyelin (SM)- and cholesterol (Chol)- driven nanodomains exist in cells and in model membranes. Studies on model membranes revealed SM and Chol driven micrometer-sized liquid-ordered domains. Although the existence of such microdomains has not been proven for the plasma membrane, such lipid mixtures have been used as a model system for ‘rafts’ [7]. On the other hand, super resolution results indicate that the plasma membrane might organize into nanocompartments. However, due to the limited resolution of those techniques their unambiguous characterization is still missing. In this lecture, a combination of Förster resonance energy transfer and Monte Carlo simulations (MC-FRET) [1] identifies directly 10 nm large nanodomains in liquid-disordered model membranes composed of lipid mixtures containing SM and Chol [2]. Our MC-FRET approach can determine the sizes and concentrations of nanodomains down to 2 nm and enables studying the nanodomain inter-leaflet coupling [3]. Combining MC-FRET with solid-state wide-line and high resolution magic angle spinning NMR as well as with fluorescence correlation spectroscopy [3] we demonstrate that these nanodomains containing hundreds of lipid molecules are fluid [2]. Addition of GM1 ganglioside, a molecule which forms already fluid 6 nm sized clusters in fluid phosphatidylcholine bilayers [5,6], leads to growth of those nanodomains while preserving the fluidity.

[1]  R. Šachl et al. Biophys. J., 101, L60-L62, 2011

[2]  A. Koukalová et al. Scientific Rep. vol. 7 p. 5460, 2017.

[3]  I. Vinklarek et al, J Phys Chem. Lett 10, 2024–2030, 2019

[4]  R. Šachl et al. J. Phys. D 49 189601, 2016

[5]  R. Šachl et al. BBA- Mol. Cell Res. 1853, 850-857, 2015.

[6]  M. Amaro et al. Angew. Chem. vol. 55 p. 9411-9415, 2016.

[7]  M. Cebecauer et al. Chem Rev, 118, (23), 11259-11297, 2018