title: Local electrostatic interactions determine the diameter of fusion pores.
abstract: In regulated exocytosis vesicular and plasma membranes merge to form a fusion pore in response to stimulation. The nonselective cation HCN channels are involved in the regulation of unitary exocytotic events by at least 2 mechanisms. They can affect SNARE-dependent exocytotic activity indirectly, via the modulation of free intracellular calcium; and/or directly, by altering local cation concentration, which affects fusion pore geometry likely via electrostatic interactions. By monitoring membrane capacitance, we investigated how extracellular cation concentration affects fusion pore diameter in pituitary cells and astrocytes. At low extracellular divalent cation levels predominantly transient fusion events with widely open fusion pores were detected. However, fusion events with predominately narrow fusion pores were present at elevated levels of extracellular trivalent cations. These results show that electrostatic interactions likely help determine the stability of discrete fusion pore states by affecting fusion pore membrane composition.
authors.affiliation: a Laboratory of Neuroendocrinology-Molecular Cell Physiology ; Institute of Pathophysiology ; Faculty of Medicine ; University of Ljubljana ; Ljubljana , Slovenia.
authors.forename: Alenka
authors.initials: A
authors.lastname: Guček
authors.forename: Jernej
authors.initials: J
authors.lastname: Jorgačevski
authors.forename: Urszula
authors.initials: U
authors.lastname: Górska
authors.forename: Boštjan
authors.initials: B
authors.lastname: Rituper
authors.forename: Marko
authors.initials: M
authors.lastname: Kreft
authors.forename: Robert
authors.initials: R
authors.lastname: Zorec
mesh_terms: D000535:Aluminum / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004576:Electromyography; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008561:Membrane Fusion; D010316:Particle Size; D015221:Potassium Channels / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D055672:Static Electricity
chemical_list: C578712:Hcn2 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D011743:Pyrimidines; C082246:ICI D2788; D000535:Aluminum; D002118:Calcium
keywords: HCN channels; astrocytes; exocytosis; fusion pore; lactotrophs; vesicles
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