title: Post-fusion structural changes and their roles in exocytosis and endocytosis of dense-core vesicles.
abstract: Vesicle fusion with the plasma membrane generates an Ω-shaped membrane profile. Its pore is thought to dilate until flattening (full-collapse), followed by classical endocytosis to retrieve vesicles. Alternatively, the pore may close (kiss-and-run), but the triggering mechanisms and its endocytic roles remain poorly understood. Here, using confocal and stimulated emission depletion microscopy imaging of dense-core vesicles, we find that fusion-generated Ω-profiles may enlarge or shrink while maintaining vesicular membrane proteins. Closure of fusion-generated Ω-profiles, which produces various sizes of vesicles, is the dominant mechanism mediating rapid and slow endocytosis within ~1-30 s. Strong calcium influx triggers dynamin-mediated closure. Weak calcium influx does not promote closure, but facilitates the merging of Ω-profiles with the plasma membrane via shrinking rather than full-collapse. These results establish a model, termed Ω-exo-endocytosis, in which the fusion-generated Ω-profile may shrink to merge with the plasma membrane, change in size or change in size then close in response to calcium, which is the main mechanism to retrieve dense-core vesicles.
authors.affiliation: 1] National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA [2].
authors.forename: Hsueh-Cheng
authors.initials: HC
authors.lastname: Chiang
authors.affiliation: 1] National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA [2].
authors.forename: Wonchul
authors.initials: W
authors.lastname: Shin
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Zhao
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Edaeni
authors.initials: E
authors.lastname: Hamid
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Jiansong
authors.initials: J
authors.lastname: Sheng
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Maryna
authors.initials: M
authors.lastname: Baydyuk
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Wen
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering (NIBIB), Bethesda, Maryland 20892, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Jin
authors.affiliation: 1] National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA [2].
authors.forename: Fanny
authors.initials: F
authors.lastname: Momboisse
authors.affiliation: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors.forename: Ling-Gang
authors.initials: LG
authors.lastname: Wu
mesh_terms: D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology; D008561:Membrane Fusion / Q000502:physiology*; D018613:Microscopy, Confocal; D022142:Secretory Vesicles / Q000737:chemistry* / Q000378:metabolism