title: A new role for the dynamin GTPase in the regulation of fusion pore expansion.
abstract: Dynamin is a master regulator of membrane fission in endocytosis. However, a function for dynamin immediately upon fusion has also been suspected from a variety of experiments that measured release of granule contents. The role of dynamin guanosine triphosphate hydrolase (GTPase) activity in controlling fusion pore expansion and postfusion granule membrane topology was investigated using polarization optics and total internal reflection fluorescence microscopy (pTIRFM) and amperometry. A dynamin-1 (Dyn1) mutant with increased GTPase activity resulted in transient deformations consistent with rapid fusion pore widening after exocytosis; a Dyn1 mutant with decreased activity slowed fusion pore widening by stabilizing postfusion granule membrane deformations. The experiments indicate that, in addition to its role in endocytosis, GTPase activity of dynamin regulates the rapidity of fusion pore expansion from tens of milliseconds to seconds after fusion. These findings expand the membrane-sculpting repertoire of dynamin to include the regulation of immediate postfusion events in exocytosis that control the rate of release of soluble granule contents.
authors: Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA. arunanan@umich.edu
authors: Arun
authors: A
authors: Anantharam
authors: Mary A
authors: MA
authors: Bittner
authors: Rachel L
authors: RL
authors: Aikman
authors: Edward L
authors: EL
authors: Stuenkel
authors: Sandra L
authors: SL
authors: Schmid
authors: Daniel
authors: D
authors: Axelrod
authors: Ronald W
authors: RW
authors: Holz
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D019439:Chromaffin Cells; D034284:Dynamin I / Q000235:genetics / Q000378:metabolism*; D004548:Elasticity; D005089:Exocytosis; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008561:Membrane Fusion / Q000235:genetics; D020125:Mutation, Missense; D009478:Neuropeptide Y / Q000378:metabolism; D021381:Protein Transport; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002395:Catecholamines; D009478:Neuropeptide Y; D011994:Recombinant Proteins; D034284:Dynamin I; D020558:GTP Phosphohydrolases