Proteasome-dependent regulation of active zone proteins in activity-induced plasticity of presynaptic function
Final Report Abstract
Ubiquitin-proteasome system mediates ubiquitination and controlled degradation of cellular proteins. In neurons, physiological proteasome was linked to regulation of neurotransmission, but excessive proteolysis was also connected to neuropathological conditions manifesting by synapse loss and neuronal cell death. The mechanisms that regulate the activity and specificity of degradation of presynaptic proteins are still underexplored. In this project we investigated role of presynaptic scaffold protein bassoon in the regulation of presynaptic proteostasis. We described an interaction of bassoon with the E3 ubiquitin ligase SIAH1, which restricts SIAH’s Ub-conjugating activity and decreases ubiquitination of its target proteins. Deletion of both bassoon and its closely related protein piccolo in neuronal cultures resulted in increased ubiquitination and degradation of multiple presynaptic proteins and induced a progressive neuronal degeneration, which was likely driven by destabilization of synaptic vesicle cluster at presynaptic sites and their degradation by proteasomal and endo-lysosomal pathway. In the following study we identified an interaction of bassoon with PSMB4, a structural subunit of 20S core proteasome. This interaction restricts endopeptidase activity of presynaptic proteasome likely by steric interference with assembly of proteasome particles. In line with a negative regulatory role of bassoon on proteasome activity we measured elevated proteasome-associated endopeptidase activity in brains of bassoon knock-out mice. Finally, we detected a substantial decrease in the size of ready releasable and recycling pool of synaptic vesicles in bassoon knock-out neurons that was largely normalized by an acute pharmacological inhibition of proteasome. Thus, we propose that unconstrained proteasome activity causes aberrant neurotransmission in the absence of bassoon and exemplify a beneficial effect of pharmacological modulation of proteasome activity in bassoon-linked synaptopathy. Taking together, the investigations done in the frame of this project revealed presynaptic proteins bassoon and piccolo as critical regulators of presynaptic ubiquitination and proteostasis and suggested that they might provide a platform for cross-regulations of proteasomal, endolysosomal and autophagosomal pathways at presynapse.
Publications
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(2013) Molecular mechanisms driving homeostatic plasticity of neurotransmitter release. Front Cell Neurosci 7:244
Lazarevic V, Pothula S, Andres-Alonso M, Fejtova A
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Bassoon and Piccolo maintain synapse integrity by regulating protein ubiquitination and degradation (2013) EMBO J ;32(7):954-69
Waites CL, Leal-Ortiz SA, Okerlund N, Dalke H, Fejtova A, Altrock WD, Gundelfinger ED, Garner CC
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(2014) Bassoon specifically controls presynaptic P/Q-type Ca2+ channels via RIM-binding protein. Neuron 82:181-194
Davydova D, Marini C, King C, Klueva J, Bischof F, Romorini S, Montenegro- Venegas C, Heine M, Schneider R, Schroder MS, Altrock WD, Henneberger C, Rusakov DA, Gundelfinger ED, Fejtova A
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EMBO J. (2015) Synaptic activity controls localization and function of CtBP1 via binding to Bassoon and Piccolo. 34(8):1056-77
Ivanova D, Dirks A, Montenegro-Venegas C, Schöne C, Altrock WD, Marini C, Frischknecht R, Schanze D, Zenker M, Gundelfinger ED, Fejtova A
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(2016) Bassoon and piccolo regulate ubiquitination and link presynaptic molecular dynamics with activity-regulated gene expression. J Physiol. 2016 Oct 1;594(19):5441-8
Ivanova D, Dirks A, Fejtova A
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(2017) Aberrant neuronal activity-induced signaling and gene expression in a mouse model of RASopathy. PLoS Genet 13(3):e1006684
Altmüller F, Pothula S, Annamneedi A, Nakhaei-Rad S, Montenegro-Venegas C, Pina-Fernández E, Marini C, Santos M, Schanze D, Montag D, Ahmadian MR, Stork O, Zenker M, Fejtova A
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(2017) Physiological Concentrations of Amyloid Beta Regulate Recycling of Synaptic Vesicles via Alpha7 Acetylcholine Receptor and CDK5/Calcineurin Signaling. Front Mol Neurosci 10:221
Lzarevic V, Fieńko S, Andres-Alonso M, Anni D, Ivanova D, Montenegro-Venegas C, Gundelfinger ED, Cousin MA, Fejtova A
