Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

52-POS Board 52 EXOCYTOSIS AS AN ENDOGENOUS ELECTROFUSION

Justin Teissie 1 ; STEFAN Weinandy 1 ; Valerie Réat 1 ; Alain Milon 1 ; Pascal Demange 1 ; 1 IPBS UMR 5089 CNRS and Université P Sabatier , Toulouse, Haute-Garonne, France It was suggested that fusion pore can be ascribed to electroporation of the membrane, triggered by the strong electric field existing at the site of exocytosis (1). Pulsed electric fields (PEF) are known to mediate a fusogenic state to plasma membranes when applied to a cell suspension. To mimic exocytosis, exocytotic vesicles are modelled by large unilamelar vesicules (LUVs). The PEF parameters are selected to affect specifically the cells leaving the vesicles unaffected. When LUVs are electrostatically brought in contact with cells by a salt bridge, their content is delivered in the cytoplasm when cells are electropermeabilized. It is the electropermeabilized state of the cell membrane that is the support of the merging between the plasma membrane and the lipid bilayer, giving an experimental support to Rosenheck’s model (1). LUV composition should be made “fusogenic” by a proper balance between phosphatidylcholine and phosphatidylethanolamine. Mixing electropermeabilized cells with tagged LUVs results in a distribution of the fluorescent lipids in the cell plasma membrane. This is observed by confocal fluorescence microscopy with fluorescently labelled LUVs. The process is a content and “membrane” mixing, following neither a «kiss and run» mechanism nor an endocytotic pathway. [1] Rosenheck K. Biophys. J. 75(3):1237-43. (1998).

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