Abstract
Tiny membrane-enclosed cellular fragments that can mediate interactions between cells and organisms have recently become a subject of increasing attention. In this work the mechanism of formation of cell membrane nanovesicles (CNVs) was studied experimentally and theoretically. CNVs were isolated by centrifugation and washing of blood cells and observed by optical microscopy and scanning electron microscopy. The shape of the biological membrane in the budding process, as observed in phospholipid vesicles, in erythrocytes and in CNVs, was described by an unifying model. Taking the mean curvature h and the curvature deviator d of the membrane surface as the relevant parameters, the shape and the distribution of membrane constituents were determined theoretically by minimization of membrane free energy. Considering these results and previous results on vesiculation of red blood cells it was interpreted that the budding processes may lead to formation of different types of CNVs as regards the compartment (exo/endovesicles), shape (spherical/tubular/torocytic) and composition (enriched/depleted in particular kinds of molecules). It was concluded that the specificity of pinched off nanovesicles derives from the shape of the membrane constituents and not primarily from their chemical identity, which explains evidences on great heterogeneity of isolated extracellular vesicles with respect to composition.
Highlights
Submicron sized membrane-enclosed cellular fragments that can mediate interactions between cellular compartments, cells and organisms have recently rised high hopes for diagnostics and therapy of different diseases
To outline the principle of budding, sequences of shapes corresponding to a formation of one spherical bud were calculated by minimization of the free energy (Eq (6)) (Fig 3; sequences a-d and f-i, respectively)
The corresponding shapes observed in cell membrane nanovesicles (CNVs) and in giant phospholipid vesicles are shown
Summary
Submicron sized membrane-enclosed cellular fragments that can mediate interactions between cellular compartments, cells and organisms have recently rised high hopes for diagnostics and therapy of different diseases. Understanding mechanisms of their formation is of utmost importance for effective use in science, medicine and technology [1,2]. It is necessary to study the processes leading to the release of the vesicles from the membrane. The mechanisms conveniently studied in these simple systems can be generalized to other types of biological membranes as they all share common essential properties
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