title: Structural organization of the presynaptic density at identified synapses in the locust central nervous system.
abstract: In a synaptic active zone, vesicles aggregate around a densely staining structure called the presynaptic density. We focus on its three-dimensional architecture and a major molecular component in the locust. We used electron tomography to study the presynaptic density in synapses made in the brain by identified second-order neuron of the ocelli. Here, vesicles close to the active zone are organized in two rows on either side of the presynaptic density, a level of organization not previously reported in insect central synapses. The row of vesicles that is closest to the density's base includes vesicles docked with the presynaptic membrane and thus presumably ready for release, whereas the outer row of vesicles does not include any that are docked. We show that a locust ortholog of the Drosophila protein Bruchpilot is localized to the presynaptic density, both in the ocellar pathway and compound eye visual neurons. An antibody recognizing the C-terminus of the Bruchpilot ortholog selectively labels filamentous extensions of the presynaptic density that reach out toward vesicles. Previous studies on Bruchpilot have focused on its role in neuromuscular junctions in Drosophila, and our study shows it is also a major functional component of presynaptic densities in the central nervous system of an evolutionarily distant insect. Our study thus reveals Bruchpilot executes similar functions in synapses that can sustain transmission of small graded potentials as well as those relaying large, spike-evoked signals.
authors.affiliation: Institute of Cell Biology, Histology and Embryology, Center for Molecular Medicine (ZMM), Medical University of Graz, Austria. Gerd.Leitinger@medunigraz
authors.forename: Gerd
authors.initials: G
authors.lastname: Leitinger
authors.forename: Sergej
authors.initials: S
authors.lastname: Masich
authors.forename: Josef
authors.initials: J
authors.lastname: Neumüller
authors.forename: Maria Anna
authors.initials: MA
authors.lastname: Pabst
authors.forename: Margit
authors.initials: M
authors.lastname: Pavelka
authors.forename: F Claire
authors.initials: FC
authors.lastname: Rind
authors.forename: Oleg
authors.initials: O
authors.lastname: Shupliakov
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Simmons
authors.forename: Dagmar
authors.initials: D
authors.lastname: Kolb
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000033:anatomy & histology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D055032:Electron Microscope Tomography / Q000379:methods; D006110:Grasshoppers / Q000033:anatomy & histology*; D007150:Immunohistochemistry; D008854:Microscopy, Electron / Q000379:methods; D009469:Neuromuscular Junction / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000648:ultrastructure*
chemical_list: C510146:BRP protein, Drosophila; D029721:Drosophila Proteins