title: Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca(2+) channel-vesicle coupling.
abstract: Brain function relies on fast and precisely timed synaptic vesicle (SV) release at active zones (AZs). Efficacy of SV release depends on distance from SV to Ca(2+) channel, but molecular mechanisms controlling this are unknown. Here we found that distances can be defined by targeting two unc-13 (Unc13) isoforms to presynaptic AZ subdomains. Super-resolution and intravital imaging of developing Drosophila melanogaster glutamatergic synapses revealed that the Unc13B isoform was recruited to nascent AZs by the scaffolding proteins Syd-1 and Liprin-α, and Unc13A was positioned by Bruchpilot and Rim-binding protein complexes at maturing AZs. Unc13B localized 120 nm away from Ca(2+) channels, whereas Unc13A localized only 70 nm away and was responsible for docking SVs at this distance. Unc13A(null) mutants suffered from inefficient, delayed and EGTA-supersensitive release. Mathematical modeling suggested that synapses normally operate via two independent release pathways differentially positioned by either isoform. We identified isoform-specific Unc13-AZ scaffold interactions regulating SV-Ca(2+)-channel topology whose developmental tightening optimizes synaptic transmission.
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.|NeuroCure, Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: Mathias A
authors.initials: MA
authors.lastname: Böhme
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Beis
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Suneel
authors.initials: S
authors.lastname: Reddy-Alla
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Reynolds
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Malou M
authors.initials: MM
authors.lastname: Mampell
authors.affiliation: NeuroCure, Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany.|Molecular and Theoretical Neuroscience, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany.
authors.forename: Andreas T
authors.identifier: 0000-0002-5895-6529
authors.initials: AT
authors.lastname: Grasskamp
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Janine
authors.initials: J
authors.lastname: Lützkendorf
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Dominique Dufour
authors.initials: DD
authors.lastname: Bergeron
authors.affiliation: Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Driller
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.
authors.forename: Husam
authors.initials: H
authors.lastname: Babikir
authors.affiliation: Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Göttfert
authors.affiliation: Plymouth University Peninsula School of Medicine, Plymouth University, Plymouth, UK.
authors.forename: Iain M
authors.initials: IM
authors.lastname: Robinson
authors.affiliation: Department of Genetics, University of Cambridge, Cambridge, UK.
authors.forename: Cahir J
authors.identifier: 0000-0002-3488-2078
authors.initials: CJ
authors.lastname: O'Kane
authors.affiliation: Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Stefan W
authors.initials: SW
authors.lastname: Hell
authors.affiliation: Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany.
authors.forename: Markus C
authors.initials: MC
authors.lastname: Wahl
authors.affiliation: Institute of Pharmaceutical Sciences, Pharmaceutical Chemistry, University of Graz, Graz, Austria.
authors.forename: Ulrich
authors.identifier: 0000-0003-2500-3585
authors.initials: U
authors.lastname: Stelzl
authors.affiliation: Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany.
authors.forename: Bernhard
authors.identifier: 0000-0001-7928-4488
authors.initials: B
authors.lastname: Loll
authors.affiliation: Molecular and Theoretical Neuroscience, Leibniz-Institut für Molekulare Pharmakologie, Berlin, Germany.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Walter
authors.affiliation: Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.|NeuroCure, Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Sigrist
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005260:Female; D020690:GTPase-Activating Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008959:Models, Neurological; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D020033:Protein Isoforms; D013572:Synaptic Vesicles / Q000378:metabolism*; D020692:rab3 GTP-Binding Proteins / Q000378:metabolism
chemical_list: C510146:BRP protein, Drosophila; D015220:Calcium Channels; D002352:Carrier Proteins; D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; C490600:Liprin-alpha protein, Drosophila; D010750:Phosphoproteins; D020033:Protein Isoforms; C577877:RIM protein, Drosophila; C548043:RhoGAP100F protein, Drosophila; C083141:phorbol ester binding protein; D020692:rab3 GTP-Binding Proteins