title: Myosin II contributes to fusion pore expansion during exocytosis.
abstract: During exocytosis, the fusion pore expands to allow release of neurotransmitters and hormones to the extracellular space. To understand the process of synaptic transmission, it is of outstanding importance to know the properties of the fusion pore and how these properties affect the release process. Many proteins have been implicated in vesicle fusion; however, there is little evidence for proteins involved in fusion pore expansion. Myosin II has been shown to participate in the transport of vesicles and, surprisingly, in the final phases of exocytosis, affecting the kinetics of catecholamine release in adrenal chromaffin cells as measured by amperometry. Here, we have studied single vesicle exocytosis in chromaffin cells overexpressing an unphosphorylatable form (T18AS19A RLC-GFP) of myosin II that produces an inactive protein by patch amperometry. This method allows direct determination of fusion pore expansion by measuring its conductance, whereas the release of catecholamines is recorded simultaneously by amperometry. Here we demonstrated that the fusion pore is of critical importance to control the release of catecholamines during single vesicle secretion in chromaffin cells. We proved that myosin II acts as a molecular motor on the fusion pore expansion by hindering its dilation when it lacks the phosphorylation sites.
authors.affiliation: Departamento Fisiología Médica y Biofísica, Universidad de Sevilla, Sevilla 41009, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Neco
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernández-Peruchena
authors.forename: Sergio
authors.initials: S
authors.lastname: Navas
authors.forename: Luis M
authors.initials: LM
authors.lastname: Gutiérrez
authors.forename: Guillermo Alvarez
authors.initials: GA
authors.lastname: de Toledo
authors.forename: Eva
authors.initials: E
authors.lastname: Alés
mesh_terms: D000818:Animals; D001692:Biological Transport; D002395:Catecholamines / Q000378:metabolism; D002463:Cell Membrane Permeability; D019439:Chromaffin Cells / Q000737:chemistry / Q000378:metabolism; D005089:Exocytosis; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008561:Membrane Fusion; D008954:Models, Biological; D009010:Monte Carlo Method; D024462:Myosin Type II / Q000737:chemistry / Q000502:physiology*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000737:chemistry
chemical_list: D002395:Catecholamines; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D024462:Myosin Type II