title: Actin dynamics provides membrane tension to merge fusing vesicles into the plasma membrane.
abstract: Vesicle fusion is executed via formation of an Ω-shaped structure (Ω-profile), followed by closure (kiss-and-run) or merging of the Ω-profile into the plasma membrane (full fusion). Although Ω-profile closure limits release but recycles vesicles economically, Ω-profile merging facilitates release but couples to classical endocytosis for recycling. Despite its crucial role in determining exocytosis/endocytosis modes, how Ω-profile merging is mediated is poorly understood in endocrine cells and neurons containing small ∼30-300 nm vesicles. Here, using confocal and super-resolution STED imaging, force measurements, pharmacology and gene knockout, we show that dynamic assembly of filamentous actin, involving ATP hydrolysis, N-WASP and formin, mediates Ω-profile merging by providing sufficient plasma membrane tension to shrink the Ω-profile in neuroendocrine chromaffin cells containing ∼300 nm vesicles. Actin-directed compounds also induce Ω-profile accumulation at lamprey synaptic active zones, suggesting that actin may mediate Ω-profile merging at synapses. These results uncover molecular and biophysical mechanisms underlying Ω-profile merging.
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Peter J
authors: PJ
authors: Wen
authors: Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.|Department of Cell Biology, WGI, Stockholm University, 106 91 Stockholm, Sweden.
authors: Staffan
authors: S
authors: Grenklo
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.|Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.
authors: Gianvito
authors: G
authors: Arpino
authors: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Xinyu
authors: X
authors: Tan
authors: National Institute of Biomedical Imaging and Bioengineering (NIBIB), Bethesda, Maryland 20892, USA.
authors: Hsien-Shun
authors: HS
authors: Liao
authors: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Johanna
authors: J
authors: Heureaux
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Shi-Yong
authors: SY
authors: Peng
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Hsueh-Cheng
authors: HC
authors: Chiang
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Edaeni
authors: E
authors: Hamid
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Wei-Dong
authors: WD
authors: Zhao
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Wonchul
authors: W
authors: Shin
authors: Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.
authors: Tuomas
authors: T
authors: Näreoja
authors: Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.
authors: Emma
authors: E
authors: Evergren
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Yinghui
authors: Y
authors: Jin
authors: Department of Cell Biology, WGI, Stockholm University, 106 91 Stockholm, Sweden.
authors: Roger
authors: R
authors: Karlsson
authors: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 6900 Lake Nona Boulevard, Orlando, Florida 32827, USA.
authors: Steven N
authors: SN
authors: Ebert
authors: National Institute of Biomedical Imaging and Bioengineering (NIBIB), Bethesda, Maryland 20892, USA.
authors: Albert
authors: 0000-0003-3826-1081
authors: A
authors: Jin
authors: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Allen P
authors: AP
authors: Liu
authors: Center of Excellence in Developmental Biology, Department of Neuroscience, Karolinska Institutet, S-171 77 Stockholm, Sweden.|Institute of Translational Biomedicine, St. Petersburg State University, St. Petersburg 199034, Russia.
authors: Oleg
authors: O
authors: Shupliakov
authors: National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, Maryland 20892, USA.
authors: Ling-Gang
authors: LG
authors: Wu
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D019439:Chromaffin Cells; D004705:Endocytosis; D005089:Exocytosis; D005260:Female; D055786:Gene Knockout Techniques; D007091:Image Processing, Computer-Assisted; D007798:Lampreys / Q000235:genetics; D008297:Male; D008561:Membrane Fusion; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008853:Microscopy / Q000379:methods; D008954:Models, Biological; D057054:Molecular Imaging / Q000379:methods; D009474:Neurons / Q000378:metabolism; D018408:Patch-Clamp Techniques; D061251:Primary Cell Culture; D022142:Secretory Vesicles / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism
chemical_list: D000199:Actins