Role of ceramide in membrane protein organization investigated by combined AFM and FCS.
Ceramide-induced alterations in the lateral organization of membrane proteins can be involved in several biological contexts, ranging from apoptosis to viral infections. In order to investigate such alterations in a simple model, we used a combined approach of atomic force microscopy, scanning fluorescence correlation spectroscopy and confocal fluorescence imaging to study the partitioning of different membrane components in sphingomyelin/dioleoyl-phosphatidylcholine/cholesterol/ceramide supported bilayers. Such model membranes exhibit coexistence of liquid-disordered, liquid-ordered (raft-like) and ceramide-rich lipid phases. Our results show that components with poor affinity toward the liquid-ordered phase, such as several fluorescent lipid analogues or the synaptic protein Synaptobrevin 2, are excluded from ceramide-rich domains. Conversely, we show for the first time that the raft-associated protein placental alkaline phosphatase (GPI-PLAP) and the ganglioside GM1 are enriched in such domains, while exhibiting a strong decrease in lateral diffusion. Analogue modulation of the local concentration and dynamics of membrane proteins/receptors by ceramide can be of crucial importance for the biological functions of cell membranes.
Chiantia
Salvatore
S
Biophysics Group, Biotechnologisches Zentrum (Biotec), Technische Universität Dresden, 01307, Germany.
Ries
Jonas
J
Chwastek
Grzegorz
G
Carrer
Dolores
D
Li
Zaiguo
Z
Bittman
Robert
R
Schwille
Petra
P
D000469:Alkaline Phosphatase / Q000378:metabolism; D002518:Ceramides / Q000502:physiology*; D004058:Diffusion; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D018625:Microscopy, Atomic Force / Q000379:methods*; D013050:Spectrometry, Fluorescence / Q000379:methods*
D002518:Ceramides; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D000469:Alkaline Phosphatase