title: Effect of ceramide on nonraft proteins.
abstract: The currently accepted model of biological membranes involves a heterogeneous, highly dynamic organization, where certain lipids and proteins associate to form cooperative platforms ("rafts") for cellular signaling or transport processes. Ceramides, a lipid species occurring under conditions of cellular stress and apoptosis, are considered to stabilize these platforms, thus modulating cellular function. The present study focuses on a previously unrecognized effect of ceramide generation. In agreement with previous studies, we find that ceramide leads to a depletion of sphingomyelin from mixtures with palmitoyl oleoyl phosphatidylcholine bilayers, forming a ceramide-sphingomyelin-rich gel phase that coexists with a fluid phase rich in palmitoyl oleoyl phosphatidylcholine. Interestingly, however, this latter phase has an almost fourfold smaller bending rigidity compared to a sphingomyelin-palmitoyl oleoyl phosphatidylcholine mixture lacking ceramide. The significant change of membrane bulk properties can have severe consequences for conformational equilibria of membrane proteins. We discuss these effects in terms of the lateral pressure profile concept for a simple geometric model of an ion channel and find a significant inhibition of its activity.
authors.affiliation: Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Schmiedlstr. 6, 8042, Graz, Austria. Georg.Pabst@oeaw.ac.at
authors.forename: Georg
authors.initials: G
authors.lastname: Pabst
authors.forename: Beate
authors.initials: B
authors.lastname: Boulgaropoulos
authors.forename: Edgar
authors.initials: E
authors.lastname: Gander
authors.forename: Bibhu R
authors.initials: BR
authors.lastname: Sarangi
authors.forename: Heinz
authors.initials: H
authors.lastname: Amenitsch
authors.forename: Velayudhan A
authors.initials: VA
authors.lastname: Raghunathan
authors.forename: Peter
authors.initials: P
authors.lastname: Laggner
mesh_terms: D002518:Ceramides / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D013109:Sphingomyelins / Q000737:chemistry / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D002518:Ceramides; D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C028694:1-palmitoyl-2-oleoylphosphatidylcholine