Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

42-POS Board 42 TARGETING FUSION TO SPECIFIC MEMBRANE DOMAINS Rafaela R. M. Cavalcanti 1,2 ; Rafael B. Lira 2 ; Karin A. Riske 1 ; Rumiana Dimova 2 ; 1 Universidade Federal de São Paulo, Biophysics, São Paulo, Brazil 2 Max Planck Institute of Kolloids and Interfaces, Theory & Bio-Systems, Golm-Potsdam, Brandenburg, Germany Membrane fusion is a fundamental process in cell life but certain molecular details are still unknown. In addition, because cell membranes are commonly organized in domains, understanding the fusion process in non-homogenous systems can be especially challenging. The use of giant unilamellar vesicles (GUVs) as a biomimetic system can assist the better understanding of the modifications occurring at the membrane fusion to specific regions and monitored changes in membrane composition using cationioc fusogenic liposomes (LUVs, ~100 nm) and GUVs exhibiting coexisting fluid and gel phases. Fusion efficiency was assessed using microscopy-based fluorescence resonance energy transfer (FRET). We observed high FRET signal at the negatively charged fluid domains. Fusion was associated with content mixing (full fusion) and GUV budding, indicating increase in membrane area. The high fusion efficiency lead to dissolution of the (initially neutral) gel domains. In GUVs with neutral fluid domains and negatively charged gel domains, we observed low FRET, low but detectable content mixing and mainly LUV docking on the gel domains. In these vesicles, the phase separated domains persisted due to the low fusion efficiency. We also explored fusion to homogeneous fluid charged GUVs with increasing cholesterol fraction: no significant change in fusion efficiency was observed. In conclusion, we demonstrate targeting of fusion to specific membrane domains and modulation of fusion efficiency by controlling membrane charge and phase state. This can play an important role in regulating the interaction between cells and liposomes used in drug delivery systems.

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