title: Enhancement of dynamin polymerization and GTPase activity by Arc/Arg3.1.
abstract: BACKGROUND
  The Activity-regulated cytoskeleton-associated protein, Arc, is an immediate-early gene product implicated in various forms of synaptic plasticity. Arc promotes endocytosis of AMPA type glutamate receptors and regulates cytoskeletal assembly in neuronal dendrites. Its role in endocytosis may be mediated by its reported interaction with dynamin 2, a 100 kDa GTPase that polymerizes around the necks of budding vesicles and catalyzes membrane scission.
  
  
  METHODS
  Enzymatic and turbidity assays are used in this study to monitor effects of Arc on dynamin activity and polymerization. Arc oligomerization is measured using a combination of approaches, including size exclusion chromatography, sedimentation analysis, dynamic light scattering, fluorescence correlation spectroscopy, and electron microscopy.
  
  
  RESULTS
  We present evidence that bacterially-expressed His6-Arc facilitates the polymerization of dynamin 2 and stimulates its GTPase activity under physiologic conditions (37°C and 100mM NaCl). At lower ionic strength Arc also stabilizes pre-formed dynamin 2 polymers against GTP-dependent disassembly, thereby prolonging assembly-dependent GTP hydrolysis catalyzed by dynamin 2. Arc also increases the GTPase activity of dynamin 3, an isoform of implicated in dendrite remodeling, but does not affect the activity of dynamin 1, a neuron-specific isoform involved in synaptic vesicle recycling. We further show in this study that Arc (either His6-tagged or untagged) has a tendency to form large soluble oligomers, which may function as a scaffold for dynamin assembly and activation.
  
  
  CONCLUSIONS
  The ability of Arc to enhance dynamin polymerization and GTPase activation may provide a mechanism to explain Arc-mediated endocytosis of AMPA receptors and the accompanying effects on synaptic plasticity.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Byers
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Barbara
authors.initials: B
authors.lastname: Barylko
authors.affiliation: Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States.
authors.forename: Justin A
authors.initials: JA
authors.lastname: Ross
authors.affiliation: Department of Chemistry and Chemical Biology, University of California, San Francisco, CA 94158, United States.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Southworth
authors.affiliation: Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: James
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Clinton A
authors.initials: CA
authors.lastname: Taylor
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Katie A
authors.initials: KA
authors.lastname: Collins
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Armando
authors.initials: A
authors.lastname: Estrada
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Maggie
authors.initials: M
authors.lastname: Waung
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Tara C
authors.initials: TC
authors.lastname: Tassin
authors.affiliation: Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Huber
authors.affiliation: Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 9681, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Jameson
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States. Electronic address: Joseph.Albanesi@UTSouthwestern.edu.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Albanesi
mesh_terms: D000818:Animals; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034284:Dynamin I / Q000378:metabolism; D034285:Dynamin II / Q000378:metabolism; D034286:Dynamin III / Q000378:metabolism; D034281:Dynamins / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D006160:Guanosine Triphosphate / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D058105:Polymerization; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012965:Sodium Chloride / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
chemical_list: D003598:Cytoskeletal Proteins; C471213:His-His-His-His-His-His; D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D011993:Recombinant Fusion Proteins; C092069:activity regulated cytoskeletal-associated protein; D012965:Sodium Chloride; D006639:Histidine; D006160:Guanosine Triphosphate; D034284:Dynamin I; D034285:Dynamin II; D034286:Dynamin III; D034281:Dynamins
keywords: Arc/Arg3.1; Dynamin; GTPase; Self-assembly