Abstract
Although lipid domains have been evidenced in several living cell plasma membranes, their roles remain largely unclear. We here investigated whether they could contribute to function-associated cell (re)shaping. To address this question, we used erythrocytes as cellular model since they (i) exhibit a specific biconcave shape, allowing for reversible deformation in blood circulation, which is lost by membrane vesiculation upon aging; and (ii) display at their outer plasma membrane leaflet two types of submicrometric domains differently enriched in cholesterol and sphingomyelin. We here reveal the specific association of cholesterol- and sphingomyelin-enriched domains with distinct curvature areas of the erythrocyte biconcave membrane. Upon erythrocyte deformation, cholesterol-enriched domains gathered in high curvature areas. In contrast, sphingomyelin-enriched domains increased in abundance upon calcium efflux during shape restoration. Upon erythrocyte storage at 4 °C (to mimick aging), lipid domains appeared as specific vesiculation sites. Altogether, our data indicate that lipid domains could contribute to erythrocyte function-associated (re)shaping.
Highlights
The acknowledgment of lipid heterogeneous lateral distribution in plasma membrane (PM) has changed our perception of their role, from simple cellular compartmentation structures to active participants in cellular functions[1]
red blood cells (RBCs) spreading is an easy system for lipid domain imaging, it was crucial to ask about the influence of RBC spreading on intrinsic lipid domain topography
PM lipid domains have been evidenced in several living cells, their functions remain largely unclear
Summary
The acknowledgment of lipid heterogeneous lateral distribution in plasma membrane (PM) has changed our perception of their role, from simple cellular compartmentation structures to active participants in cellular functions[1]. RBC exhibits a specific biconcave shape in circulation, which results in high area-to-volume ratio with a ~40% surface excess as compared to a sphere of the same volume This specific shape both ensures fast oxygen and carbon dioxide exchanges between the RBC interior and its environment and decreases the forces that have to be applied to deform the membrane as compared to a spherical shape[21]. We here took benefit from the RBC wide range of function-related (re)shaping processes to investigate the potential role of submicrometric lipid domains in cell shape control To this end, we probed by vital imaging the lateral distribution of chol and SM (using either specific Toxin fragments or trace insertion of BODIPY-SM as previously12, 14) in relation with: (i) membrane biconcavity of resting RBC; (ii) membrane curvature changes and Ca2+ exchanges upon mechanical stretching of healthy RBCs or in elliptocytes, a RBC model of impaired shape[22]; and (iii) membrane vesiculation upon RBC aging. Our results revealed the contribution of lipid domains to erythrocyte function-associated (re)shaping
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