Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

62-POS Board 62 DYNAMIN 1 PUTS ALL VESICULAR RELEASE VIA SUBQUANTAL MODE IN ADRENAL CHROMAFFIN CELLS Zhuan Zhou 1 ; Quanfeng Zhang 1 ; Qihui Wu 1 ; 1 Institute of Molecular Medicine, Peking University, Beijing, China Dynamin 1 (dyn1) is required for clathrin-mediated endocytosis in most secretory (neuronal and neuroendocrine) cells. There are two modes of Ca 2+ -dependent catecholamine release from single dense-core vesicles: full-quantal (quantal) and sub-quantal in adrenal chromaffin cells (ACCs), but their relative occurrences and impacts on total secretion remain unclear. To address this fundamental question in neurotransmission area using both sexes of animals, here we report 1) dyn1-KO increased quantal size (QS, but not vesicle size/content) by >250% in dyn1-KO mice; 2) the KO-increase QS was rescued by dyn1 (but not its deficient mutant or dyn2); 3) the ratio of quantal versus subquantal events was increased by KO; 4) following a release event, more protein contents were retained in WT vs KO vesicles; and 5) the fusion pore size d p was increased from £9 to =9 nm by KO. Thus, Ca 2+ -induced exocytosis is a sub-quantal release in sympathetic adrenal chromaffin cells, implying that neurotransmitter release is generally regulated by dynamin in neuronal cells.

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