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- Delacruz, Joannalyn B., et al.
(författare)
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Fusion pores with low conductance are cation selective
- 2021
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 36:8, s. 109580-109580
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Tidskriftsartikel (refereegranskat)abstract
- Many neurotransmitters are organic ions that carry a net charge, and their release from secretory vesicles is therefore an electrodiffusion process. The selectivity of early exocytotic fusion pores is investigated by combining electrodiffusion theory, measurements of amperometric foot signals from chromaffin cells with anion substitution, and molecular dynamics simulation. The results reveal that very narrow fusion pores are cation selective, but more dilated fusion pores become anion permeable. The transition occurs around a fusion pore conductance of ∼300 pS. The cation selectivity of a narrow fusion pore accelerates the release of positively charged transmitters such as dopamine, noradrenaline, adrenaline, serotonin, and acetylcholine, while glutamate release may require a more dilated fusion pore.
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| 2. |
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| 3. |
- Zhao, Ying, et al.
(författare)
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All SNAP25 molecules in the vesicle–plasma membrane contact zone change conformation during vesicle priming
- 2024
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 121:2
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Tidskriftsartikel (refereegranskat)abstract
- In neuronal cell types, vesicular exocytosis is governed by the SNARE (soluble NSF attachment receptor) complex consisting of synaptobrevin2, SNAP25, and syntaxin1. These proteins are required for vesicle priming and fusion. We generated an improved SNAP25- based SNARE COmplex Reporter (SCORE2) incorporating mCeruelan3 and Venus and overexpressed it in SNAP25 knockout embryonic mouse chromaffin cells. This construct rescues vesicle fusion with properties indistinguishable from fusion in wild- type cells. Combining electrochemical imaging of individual release events using electrochemical detector arrays with total internal reflection fluorescence resonance energy transfer (TIR- FRET) imaging reveals a rapid FRET increase preceding indi-vidual fusion events by 65 ms. The experiments are performed under conditions of a steady- state cycle of docking, priming, and fusion, and the delay suggests that the FRET change reflects tight docking and priming of the vesicle, followed by fusion after ~65 ms. Given the absence of wt SNAP25, SCORE2 allows determination of the number of molecules at fusion sites and the number that changes conformation. The number of SNAP25 molecules changing conformation in the priming step increases with vesicle size and SNAP25 density in the plasma membrane and equals the number of copies present in the vesicle–plasma membrane contact zone. We estimate that in wt cells, 6 to 7 copies of SNAP25 change conformation during the priming step.
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