Functional nanoscopy of the synaptic active zone
Final Report Abstract
Information processing by the nervous system depends on neurotransmitter release from synaptic vesicles (SVs) at the highly specialized presynaptic active zone (AZ). The precise molecular architecture of AZs gives rise to different structural and functional AZ states, which shape chemical neurotransmission and fundamentally influence brain function. Despite a gradually emerging comprehensive AZ protein catalogue, we still lack basic mechanistic information describing how the nanoscopic organisation and functional interactions of proteins determine AZ physiology. To a large extent, this is due to the diffraction-limited resolution of conventional light microscopy, which has hindered access to the spatial nanodomain in a physiologically relevant context and to experimental difficulties of studying AZ function in vivo. The present research project set out to study how function is encoded in the ultrastructure of AZs. Focusing on Drosophila melanogaster, the experiments took advantage of the powerful tools for manipulating the fruit fly genome and exploited the experimental accessibility of the larval peripheral nervous system. The technology-driven research program focussed on two central work packages. (i) A genetic screen was combined with electrophysiology and superresolution microscopy to characterize molecular mechanisms of AZ plasticity. (ii) New optogenetic approaches were introduced to manipulate synaptic activity in the intact, freely moving organism. The main results identified the conserved SNARE regulator Complexin (Cpx) as a functional interaction partner of the core AZ component Bruchpilot (Brp). Cpx and Brp promote SV recruitment to the filamentous AZ cytomatrix and counteract short-term synaptic depression. Combined with a comparative analysis of mouse ribbon synapses, these findings support an evolutionarily conserved role of Cpx upstream of SNARE complex assembly. In terms of technological advances, highly efficient optogenetic effectors based on Channelrhodopsin-2 derivatives and the photoactivated adenylyl cyclase bPAC were developed. Together with innovative photostimulation strategies, these tools provide new opportunities for studying AZ physiology in a behavioural context.
Publications
- (2017) Drosophila active zones: from molecules to behaviour. Neurosci Res 127:14-24
Ehmann N, Owald D, Kittel RJ
(See online at https://doi.org/10.1016/j.neures.2017.11.015) - 2017) Mechano-dependent signaling by Latrophilin/CIRL quenches cAMP in proprioceptive neurons. eLife 6:e28360
Scholz N, Guan C, Nieberler M, Grotemeyer A, Maiellaro I, Gao S, Beck S, Pawlak M, Sauer M, Asan E, Rothemund S, Winkler J, Prömel S, Nagel G, Langenhan T, Kittel RJ
(See online at https://doi.org/10.7554/eLife.28360) - (2018) Synthetic light-activated ion channels for optogenetic activation and inhibition. Front Neurosci 12:643
Beck S, Yu-Strzelczyk J, Pauls D, Constantin OM, Gee CE, Ehmann N, Kittel RJ, Nagel G, Gao S
(See online at https://doi.org/10.3389/fnins.2018.00643) - (2019) Complexin cooperates with Bruchpilot to tether synaptic vesicles to the active zone cytomatrix. J Cell Biol 218:1011-1026
Scholz N, Ehmann N, Sachidanandan D, Imig C, Cooper BH, Jahn O, Reim K, Brose N, Meyer J, Lamberty M, Altrichter S, Bormann A, Hallermann S, Pauli M, Heckmann M, Stigloher C, Langenhan T, Kittel RJ
(See online at https://doi.org/10.1083/jcb.201806155) - (2019) Implications of the Sap47 null mutation for synapsin phosphorylation, longevity, climbing proficiency and behavioural plasticity in adult Drosophila. J Exp Biol 222:19
Blanco-Redondo B, Nuwal N, Kneitz S, Nuwal T, Halder P, Liu Y, Ehmann N, Scholz N, Mayer A, Kleber J, Kähne T, Schmitt D, Sadanandappa MK, Funk N, Albertova V, Helfrich-Förster C, Ramaswami M, Hasan G, Kittel RJ, Langenhan T, Gerber B, Buchner E
(See online at https://doi.org/10.1242/jeb.203505) - (2020) Active zone compaction in presynaptic homeostatic potentiation. bioRxiv
Mrestani A, Kollmannsberger P, Pauli M, Repp F, Kittel RJ, Eilers J, Doose S, Sauer M, Sirén A-L, Heckmann M, Paul MM
(See online at https://doi.org/10.1101/802843) - (2020) Antinociceptive modulation by the adhesion GPCR CIRL promotes mechanosensory signal discrimination. eLife 9:e56738
Dannhäuser S, Lux TJ, Hu C, Selcho M, Chen JT-C, Ehmann N, Sachidanandan D, Stopp S, Pauls D, Pawlak M, Langenhan T, Soba P, Rittner HL, Kittel RJ
(See online at https://doi.org/10.7554/eLife.56738) - (2020) Smartphone optogenetics: Controlling the behaviour of Drosophila melanogaster using smartphone displays. Sci Rep 10:17614
Meloni I, Sachidanandan D, Thum AS, Kittel RJ, Murawski C
(See online at https://doi.org/10.1038/s41598-020-74448-4)
