title: Curvature-dependent lateral distribution of raft markers in the human erythrocyte membrane.
abstract: The distribution of raft markers in curved membrane exvaginations and invaginations, induced in human erythrocytes by amphiphile-treatment or increased cytosolic calcium level, was studied by fluorescence microscopy. Cholera toxin subunit B and antibodies were used to detect raft components. Ganglioside GM1 was enriched in membrane exvaginations (spiculae) induced by cytosolic calcium and amphiphiles. Stomatin and the cytosolic proteins synexin and sorcin were enriched in spiculae when induced by cytosolic calcium, but not in spiculae induced by amphiphiles. No enrichment of flotillin-1 was detected in spiculae. Analyses of the relative protein content of released exovesicles were in line with the microscopic observations. In invaginations induced by amphiphiles, the enrichment of ganglioside GM1, but not of the integral membrane proteins flotillin-1 and stomatin, was observed. Based on the experimental results and theoretical considerations we suggest that membrane skeleton-detached, laterally mobile rafts may sort into curved or flat membrane regions dependent on their intrinsic molecular shape and/or direct interactions between the raft elements.
authors.affiliation: Department of Biology, Abo Akademi University, Abo/Turku, Finland. henry.hagerstrand@abo.fi
authors.forename: Henry
authors.initials: H
authors.lastname: Hägerstrand
authors.forename: Lucyna
authors.initials: L
authors.lastname: Mrówczyńska
authors.forename: Ulrich
authors.initials: U
authors.lastname: Salzer
authors.forename: Rainer
authors.initials: R
authors.lastname: Prohaska
authors.forename: Kimmo A
authors.initials: KA
authors.lastname: Michelsen
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglic
authors.forename: Ales
authors.initials: A
authors.lastname: Iglic
mesh_terms: D015415:Biomarkers / Q000097:blood*; D002118:Calcium / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D008560:Membrane Fluidity / Q000502:physiology; D021962:Membrane Microdomains / Q000502:physiology*; D008565:Membrane Proteins; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology; D013501:Surface-Active Agents / Q000494:pharmacology
chemical_list: D015415:Biomarkers; D008565:Membrane Proteins; D013501:Surface-Active Agents; D002118:Calcium