Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

14-POS Board 14 A RANDOM-WALK MODEL FOR HIGHLY DYNAMIC SIMULATIONS OF THE VESICULAR RELEASE PROCESS Johan Dunevall 1 ; Anna Larsson 2 ; Soodabeh Majdi 2 ; Sebastian Barg 1 ; Andrew G Ewing 2 ; 1 Uppsala University, Medical Cell Biology, Uppsala, Uppsala län, Sweden 2 University of Gothenburg, Chemistry and Molecular Biology, Göteborg, Västra Götalands län, Sweden One technique that has proven extremely useful for the study of exocytosis during the last 25 years is single cell amperometry (SCA). In SCA benefits from the many neurotransmitters and/or hormones (signaling molecules), such as, catecholamines that are electroactive and can be oxidized or reduced at the surface of a polarized electrode. By recording the current passed through the electrode surface as a function of time a current vs. trace is obtained, which allows for the number of released molecules to be quantified. Also, due to the excellent temporal resolution (< ms) of SCA, rapid fluctuation in current (flux of molecules) can be monitored progressively during a release event. However, in the data obtained by this method, information about the regulatory mechanism of exocytosis is hidden and to be able to fully understand the release process highly dynamic models must be used. We present here a random-walk-based model where all geometric features, such as vesicle and pore radius as well as intra- and extravesicular diffusion coefficients can be altered as a function of time. This modelling tool can be used to increase the understanding of what factors are important for the regulation of exocytosis. In addition, the model can be used to estimate the fluctuation of the fusion pore radius as a function of time from experimentally obtained data. This can be extremely useful to understand how exocytosis is regulated during partial release, where only a fraction of the vesicular content is released during a fusion event.

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