title: Glutamate receptor dynamics organizing synapse formation in vivo.
abstract: Insight into how glutamatergic synapses form in vivo is important for understanding developmental and experience-triggered changes of excitatory circuits. Here, we imaged postsynaptic densities (PSDs) expressing a functional, GFP-tagged glutamate receptor subunit (GluR-IIA(GFP)) at neuromuscular junctions of Drosophila melanogaster larvae for several days in vivo. New PSDs, associated with functional and structural presynaptic markers, formed independently of existing synapses and grew continuously until reaching a stable size within hours. Both in vivo photoactivation and photobleaching experiments showed that extrasynaptic receptors derived from diffuse, cell-wide pools preferentially entered growing PSDs. After entering PSDs, receptors were largely immobilized. In comparison, other postsynaptic proteins tested (PSD-95, NCAM and PAK homologs) exchanged faster and with no apparent preference for growing synapses. We show here that new glutamatergic synapses form de novo and not by partitioning processes from existing synapses, suggesting that the site-specific entry of particular glutamate receptor complexes directly controls the assembly of individual PSDs.
authors.affiliation: European Neuroscience Institute Göttingen, Max-Planck-Society, Waldweg 33, D-37073 Göttingen, Germany.
authors.forename: Tobias M
authors.initials: TM
authors.lastname: Rasse
authors.forename: Wernher
authors.initials: W
authors.lastname: Fouquet
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmid
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kittel
authors.forename: Sara
authors.initials: S
authors.lastname: Mertel
authors.forename: Carola B
authors.initials: CB
authors.lastname: Sigrist
authors.forename: Manuela
authors.initials: M
authors.lastname: Schmidt
authors.forename: Asja
authors.initials: A
authors.lastname: Guzman
authors.forename: Carlos
authors.initials: C
authors.lastname: Merino
authors.forename: Gang
authors.initials: G
authors.lastname: Qin
authors.forename: Christine
authors.initials: C
authors.lastname: Quentin
authors.forename: Frank F
authors.initials: FF
authors.lastname: Madeo
authors.forename: Manfred
authors.initials: M
authors.lastname: Heckmann
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Sigrist
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster; D049452:Green Fluorescent Proteins; D007814:Larva; D049408:Luminescent Agents; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism; D018091:Receptors, AMPA / Q000378:metabolism / Q000502:physiology*; D013569:Synapses / Q000502:physiology*
chemical_list: D049408:Luminescent Agents; D009419:Nerve Tissue Proteins; D018091:Receptors, AMPA; C033652:postsynaptic density proteins; D049452:Green Fluorescent Proteins; C104722:glutamate receptor ionotropic, AMPA 2