Catherine Leonard1,2, Hélène Pollet2, Christiane Vermylen3, Nir Gov4, Donatienne Tyteca2, Marie-Paule Mingeot-Leclercq1. 1. FACM Unit, Louvain Drug Research Institute & Université Catholique de Louvain, Brussels, Belgium. 2. CELL Unit, de Duve Institute & Université Catholique de Louvain, Brussels, Belgium. 3. PEDI Unit, Institut de Recherche Expérimentale et Clinique & Université Catholique de Louvain, Brussels, Belgium. 4. Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
Abstract
BACKGROUND/AIMS: Transient nanometric cholesterol- and sphingolipid-enriched domains, called rafts, are characterized by higher lipid order as compared to surrounding lipids. Here, we asked whether the seminal concept of highly ordered rafts could be refined with the presence of lipid domains exhibiting different enrichment in cholesterol and sphingomyelin and association with erythrocyte curvature areas. We also investigated how differences in lipid order between domains and surrounding membrane (bulk) are regulated and whether changes in order differences could participate to erythrocyte deformation and vesiculation. METHODS: We used the fluorescent hydration- and membrane packing-sensitive probe Laurdan to determine by imaging mode the Generalized Polarization (GP) values of lipid domains vs the surrounding membrane. RESULTS: Laurdan revealed the majority of sphingomyelin-enriched domains associated to low erythrocyte curvature areas and part of the cholesterol-enriched domains associated with high curvature. Both lipid domains were less ordered than the surrounding lipids in erythrocytes at resting state. Upon erythrocyte deformation (elliptocytes and stimulation of calcium exchanges) or membrane vesiculation (storage at 4°C), lipid domains became more ordered than the bulk. Upon aging and in membrane fragility diseases (spherocytosis), an increase in the difference of lipid order between domains and the surrounding lipids contributed to the initiation of domain vesiculation. CONCLUSION: The critical role of domain-bulk differential lipid order modulation for erythrocyte reshaping is discussed in relation with the pressure exerted by the cytoskeleton on the membrane.
BACKGROUND/AIMS: Transient nanometric cholesterol- and sphingolipid-enriched domains, called rafts, are characterized by higher lipid order as compared to surrounding lipids. Here, we asked whether the seminal concept of highly ordered rafts could be refined with the presence of lipid domains exhibiting different enrichment in cholesterol and sphingomyelin and association with erythrocyte curvature areas. We also investigated how differences in lipid order between domains and surrounding membrane (bulk) are regulated and whether changes in order differences could participate to erythrocyte deformation and vesiculation. METHODS: We used the fluorescent hydration- and membrane packing-sensitive probe Laurdan to determine by imaging mode the Generalized Polarization (GP) values of lipid domains vs the surrounding membrane. RESULTS: Laurdan revealed the majority of sphingomyelin-enriched domains associated to low erythrocyte curvature areas and part of the cholesterol-enriched domains associated with high curvature. Both lipid domains were less ordered than the surrounding lipids in erythrocytes at resting state. Upon erythrocyte deformation (elliptocytes and stimulation of calcium exchanges) or membrane vesiculation (storage at 4°C), lipid domains became more ordered than the bulk. Upon aging and in membrane fragility diseases (spherocytosis), an increase in the difference of lipid order between domains and the surrounding lipids contributed to the initiation of domain vesiculation. CONCLUSION: The critical role of domain-bulk differential lipid order modulation for erythrocyte reshaping is discussed in relation with the pressure exerted by the cytoskeleton on the membrane.
Authors: Anne-Sophie Cloos; Marine Ghodsi; Amaury Stommen; Juliette Vanderroost; Nicolas Dauguet; Hélène Pollet; Ludovic D'Auria; Eric Mignolet; Yvan Larondelle; Romano Terrasi; Giulio G Muccioli; Patrick Van Der Smissen; Donatienne Tyteca Journal: Front Physiol Date: 2020-07-03 Impact factor: 4.566