title: Ceramide-Induced Lamellar Gel Phases in Fluid Cell Lipid Extracts.
abstract: The effects of increasing amounts of palmitoylceramide (pCer) on human red blood cell lipid membranes have been studied using atomic force microscopy of supported lipid bilayers, in both imaging (bilayer thickness) and force-spectroscopy (nanomechanical resistance) modes. Membranes appeared homogeneous with pCer concentrations up to 10 mol % because of the high concentration of cholesterol (Chol) present in the membrane (∼45 mol %). However, the presence of pCer at 30 mol % gave rise to a clearly distinguishable segregated phase with a nanomechanical resistance 7-fold higher than the continuous phase. These experiments were validated using differential scanning calorimetry. Furthermore, Chol depletion of the bilayers caused lipid domain generation in the originally homogeneous samples, and Chol-depleted domain stiffness significantly increased with higher amounts of pCer. These results point to the possibility of different kinds of transient and noncompositionally constant, complex gel-like phases present in RBC lipid membranes rich in both pCer and Chol, in contrast to the widespread opinion about the displacements between pCer-enriched "gel-like" domains and liquid-ordered "raft-like" Chol-enriched phases. Changes in the biophysical properties of these complex gel-like phases governed by local modulation of pCer:Chol ratios could be a cell mechanism for fine-tuning the properties of membranes as required.
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.
authors.forename: Aritz B
authors.initials: AB
authors.lastname: García-Arribas
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.|Institut Supérieur Des Professions Infirmières Et Des Techniques De Santé Rabat, Km 4.5 route de Casa, Rabat, Morocco.
authors.forename: Hasna
authors.initials: H
authors.lastname: Ahyayauch
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Sot
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.
authors.forename: Pablo L
authors.initials: PL
authors.lastname: López-González
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Alonso
authors.affiliation: Biofisika Institute (CSIC, UPV/EHU) , 48940 Leioa, Spain.|Departamento de Bioquímica, University of the Basque Country (UPV/EHU) , 48940 Leioa, Spain.
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
mesh_terms: D002152:Calorimetry, Differential Scanning; D002518:Ceramides / Q000494:pharmacology*; D002784:Cholesterol / Q000737:chemistry* / Q000302:isolation & purification; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D018625:Microscopy, Atomic Force; D044367:Phase Transition / Q000187:drug effects*; D047392:beta-Cyclodextrins / Q000737:chemistry / Q000494:pharmacology
chemical_list: D002518:Ceramides; D008051:Lipid Bilayers; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C097760:N-palmitoylsphingosine; D002784:Cholesterol