scholarly journals Reconstructing essential active zone functions within a synapse

2021 ◽  
Author(s):  
Chao Tan ◽  
Shan Shan H Wang ◽  
Giovanni de Nola ◽  
Pascal S Kaeser
Keyword(s):  
Fusion Protein ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Molecular Machines ◽  
Vesicle Docking ◽  
Active Zones ◽  
Ca2 Channels

Active zones are molecular machines that control neurotransmitter release through synaptic vesicle docking and priming, and through coupling of these vesicles to Ca2+ entry. The complexity of active zone machinery has made it challenging to determine which mechanisms drive these roles in release. Here, we induce RIM+ELKS knockout to eliminate active zone scaffolding networks, and then reconstruct each active zone function. Re-expression of RIM1-Zn fingers positioned Munc13 on undocked vesicles and rendered them release-competent. Reconstitution of release-triggering required docking of these vesicles to Ca2+ channels. Fusing RIM1-Zn to CaVbeta4-subunits sufficed to restore docking, priming and release-triggering without reinstating active zone scaffolds. Hence, exocytotic activities of the 80 kDa CaVbeta4-Zn fusion protein bypassed the need for megadalton-sized secretory machines. These data define key mechanisms of active zone function, establish that fusion competence and docking are mechanistically separable, and reveal that active zone scaffolding networks are not required for release.

scholarly journals A novel region in the CaV2.1 α1 subunit C-terminus regulates fast synaptic vesicle fusion and vesicle docking at the mammalian presynaptic active zone

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Matthias Lübbert ◽  
R Oliver Goral ◽  
Rachel Satterfield ◽  
Travis Putzke ◽  
Arn MJM van den Maagdenberg ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Physical Distance ◽  
Subunit C ◽  
Vesicle Docking ◽  
C Terminus ◽  
Synaptic Vesicle Release ◽  
Synaptic Vesicle Fusion ◽  
Α1 Subunit

In central nervous system (CNS) synapses, action potential-evoked neurotransmitter release is principally mediated by CaV2.1 calcium channels (CaV2.1) and is highly dependent on the physical distance between CaV2.1 and synaptic vesicles (coupling). Although various active zone proteins are proposed to control coupling and abundance of CaV2.1 through direct interactions with the CaV2.1 α1 subunit C-terminus at the active zone, the role of these interaction partners is controversial. To define the intrinsic motifs that regulate coupling, we expressed mutant CaV2.1 α1 subunits on a CaV2.1 null background at the calyx of Held presynaptic terminal. Our results identified a region that directly controlled fast synaptic vesicle release and vesicle docking at the active zone independent of CaV2.1 abundance. In addition, proposed individual direct interactions with active zone proteins are insufficient for CaV2.1 abundance and coupling. Therefore, our work advances our molecular understanding of CaV2.1 regulation of neurotransmitter release in mammalian CNS synapses.

RIM proteins and their role in synapse function

2010 ◽  
Vol 391 (6) ◽  
Author(s):  
Tobias Mittelstaedt ◽  
Elena Alvaréz-Baron ◽  
Susanne Schoch
Keyword(s):  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Multidomain Proteins ◽  
Short Term ◽  
Presynaptic Nerve Terminal ◽  
Presynaptic Plasticity ◽  
Active Zones ◽  
Synaptic Vesicle Release ◽  
The Brain

Abstract Active zones are specialized areas of the plasma membrane in the presynaptic nerve terminal that mediate neurotransmitter release and synaptic plasticity. The multidomain proteins RIM1 and RIM2 are integral components of the cytomatrix at the active zone, interacting with most other active zone-enriched proteins as well as synaptic vesicle proteins. In the brain, RIMs are present in multiple isoforms (α, β, γ) diverging in their structural composition, which mediate overlapping and distinct functions. Here, we summarize recent findings about the specific roles of the various RIM isoforms in basic synaptic vesicle release as well as long- and short-term presynaptic plasticity.

Neurotransmitter Release

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Synaptic Membrane ◽  
Specialized Region ◽  
Synaptic Vesicle Fusion

The biochemical and physiological processes of neurotransmitter release from an active zone, a specialized region of synaptic membrane, are examined. Synaptic vesicles containing neurotransmitters are docked at the active zone and then primed for release by SNARE complexes that bring them into extreme proximity to the plasma membrane. Entry of calcium ions through voltage-gated calcium channels triggers synaptic vesicle fusion with the synaptic terminal membrane and the consequent diffusion of neurotransmitter into the synaptic cleft. Release results when the fusion pore bridging the synaptic vesicle and plasma membrane widens and neurotransmitter from the inside of the synaptic vesicle diffuses into the synaptic cleft. Membrane from the active zone membrane is endocytosed, and synaptic vesicle proteins are then reassembled into recycled synaptic vesicles, allowing for more rounds of neurotransmitter release.

scholarly journals Fife organizes synaptic vesicles and calcium channels for high-probability neurotransmitter release

2016 ◽  
Vol 216 (1) ◽  
pp. 231-246 ◽  
Author(s):  
Joseph J. Bruckner ◽  
Hong Zhan ◽  
Scott J. Gratz ◽  
Monica Rao ◽  
Fiona Ukken ◽  
...  
Keyword(s):  
Neural Plasticity ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Motor Behavior ◽  
Molecular Organization ◽  
Electrophysiological Studies ◽  
Circuit Function ◽  
Synaptic Vesicle Release ◽  
Ca2 Channels

The strength of synaptic connections varies significantly and is a key determinant of communication within neural circuits. Mechanistic insight into presynaptic factors that establish and modulate neurotransmitter release properties is crucial to understanding synapse strength, circuit function, and neural plasticity. We previously identified Drosophila Piccolo-RIM-related Fife, which regulates neurotransmission and motor behavior through an unknown mechanism. Here, we demonstrate that Fife localizes and interacts with RIM at the active zone cytomatrix to promote neurotransmitter release. Loss of Fife results in the severe disruption of active zone cytomatrix architecture and molecular organization. Through electron tomographic and electrophysiological studies, we find a decrease in the accumulation of release-ready synaptic vesicles and their release probability caused by impaired coupling to Ca2+ channels. Finally, we find that Fife is essential for the homeostatic modulation of neurotransmission. We propose that Fife organizes active zones to create synaptic vesicle release sites within nanometer distance of Ca2+ channel clusters for reliable and modifiable neurotransmitter release.

scholarly journals Alignment of Synaptic Vesicle Macromolecules with the Macromolecules in Active Zone Material that Direct Vesicle Docking

PLoS ONE ◽  
2013 ◽  
Vol 8 (7) ◽  
pp. e69410 ◽  
Author(s):  
Mark L. Harlow ◽  
Joseph A. Szule ◽  
Jing Xu ◽  
Jae Hoon Jung ◽  
Robert M. Marshall ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Active Zone ◽  
Vesicle Docking

scholarly journals Drosophila Synaptotagmin 7 negatively regulates synaptic vesicle fusion and replenishment in a dosage-dependent manner

2020 ◽  
Author(s):  
Zhuo Guan ◽  
Mónica C. Quiñones-Frías ◽  
Yulia Akbergenova ◽  
J. Troy Littleton
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Dependent Manner ◽  
Short Term ◽  
Sensor Model ◽  
Synaptotagmin 1 ◽  
Asynchronous Release ◽  
Synaptic Vesicle Fusion

AbstractSynchronous neurotransmitter release is triggered by Ca2+ binding to the synaptic vesicle protein Synaptotagmin 1, while asynchronous fusion and short-term facilitation is hypothesized to be mediated by plasma membrane-localized Synaptotagmin 7 (SYT7). We generated mutations in Drosophila Syt7 to determine if it plays a conserved role as the Ca2+ sensor for these processes. Electrophysiology and quantal imaging revealed evoked release was elevated 2-fold. Syt7 mutants also had a larger pool of readily-releasable vesicles, faster recovery following stimulation, and robust facilitation. Syt1/Syt7 double mutants displayed more release than Syt1 mutants alone, indicating SYT7 does not mediate the residual asynchronous release remaining in the absence of SYT1. SYT7 localizes to an internal membrane tubular network within the peri-active zone, but does not enrich at release sites. These findings indicate the two Ca2+ sensor model of SYT1 and SYT7 mediating all phases of neurotransmitter release and facilitation is not applicable at Drosophila synapses.

scholarly journals Ring-like oligomers of Synaptotagmins and related C2 domain proteins

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Maria N Zanetti ◽  
Oscar D Bello ◽  
Jing Wang ◽  
Jeff Coleman ◽  
Yiying Cai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Synaptic Transmission ◽  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
Structural Aspect ◽  
C2 Domain ◽  
Early Step ◽  
Vesicle Docking ◽  
Ring Assembly ◽  
Synaptotagmin 1

We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca2+-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca2+ involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca2+ influx.

scholarly journals Separation of presynaptic Cav2 and Cav1 channel function in synaptic vesicle exo- and endocytosis by the membrane anchored Ca2+ pump PMCA

2021 ◽  
Vol 118 (28) ◽  
pp. e2106621118
Author(s):  
Niklas Krick ◽  
Stefanie Ryglewski ◽  
Aylin Pichler ◽  
Arthur Bikbaev ◽  
Torsten Götz ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
Calcium Currents ◽  
Short Term ◽  
Triggered Release ◽  
Presynaptic Terminals ◽  
Dynamic Regulation ◽  
Short Term Plasticity ◽  
Separate Control ◽  
Active Zones

Synaptic vesicle (SV) release, recycling, and plastic changes of release probability co-occur side by side within nerve terminals and rely on local Ca2+ signals with different temporal and spatial profiles. The mechanisms that guarantee separate regulation of these vital presynaptic functions during action potential (AP)–triggered presynaptic Ca2+ entry remain unclear. Combining Drosophila genetics with electrophysiology and imaging reveals the localization of two different voltage-gated calcium channels at the presynaptic terminals of glutamatergic neuromuscular synapses (the Drosophila Cav2 homolog, Dmca1A or cacophony, and the Cav1 homolog, Dmca1D) but with spatial and functional separation. Cav2 within active zones is required for AP-triggered neurotransmitter release. By contrast, Cav1 localizes predominantly around active zones and contributes substantially to AP-evoked Ca2+ influx but has a small impact on release. Instead, L-type calcium currents through Cav1 fine-tune short-term plasticity and facilitate SV recycling. Separate control of SV exo- and endocytosis by AP-triggered presynaptic Ca2+ influx through different channels demands efficient measures to protect the neurotransmitter release machinery against Cav1-mediated Ca2+ influx. We show that the plasma membrane Ca2+ ATPase (PMCA) resides in between active zones and isolates Cav2-triggered release from Cav1-mediated dynamic regulation of recycling and short-term plasticity, two processes which Cav2 may also contribute to. As L-type Cav1 channels also localize next to PQ-type Cav2 channels within axon terminals of some central mammalian synapses, we propose that Cav2, Cav1, and PMCA act as a conserved functional triad that enables separate control of SV release and recycling rates in presynaptic terminals.

scholarly journals Hypothesis Relating the Structure, Biochemistry and Function of Active Zone Material Macromolecules at a Neuromuscular Junction

2022 ◽  
Vol 13 ◽  
Author(s):  
Joseph A. Szule
Keyword(s):  
Membrane Fusion ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Structural Integrity ◽  
Neuromuscular Junctions ◽  
Vesicle Trafficking ◽  
Material Structure ◽  
Neurotransmitter Secretion ◽  
Active Zones ◽  
And Function

This report integrates knowledge of in situ macromolecular structures and synaptic protein biochemistry to propose a unified hypothesis for the regulation of certain vesicle trafficking events (i.e., docking, priming, Ca2+-triggering, and membrane fusion) that lead to neurotransmitter secretion from specialized “active zones” of presynaptic axon terminals. Advancements in electron tomography, to image tissue sections in 3D at nanometer scale resolution, have led to structural characterizations of a network of different classes of macromolecules at the active zone, called “Active Zone Material’. At frog neuromuscular junctions, the classes of Active Zone Material macromolecules “top-masts”, “booms”, “spars”, “ribs” and “pins” direct synaptic vesicle docking while “pins”, “ribs” and “pegs” regulate priming to influence Ca2+-triggering and membrane fusion. Other classes, “beams”, “steps”, “masts”, and “synaptic vesicle luminal filaments’ likely help organize and maintain the structural integrity of active zones. Extensive studies on the biochemistry that regulates secretion have led to comprehensive characterizations of the many conserved proteins universally involved in these trafficking events. Here, a hypothesis including a partial proteomic atlas of Active Zone Material is presented which considers the common roles, binding partners, physical features/structure, and relative positioning in the axon terminal of both the proteins and classes of macromolecules involved in the vesicle trafficking events. The hypothesis designates voltage-gated Ca2+ channels and Ca2+-gated K+ channels to ribs and pegs that are connected to macromolecules that span the presynaptic membrane at the active zone. SNARE proteins (Syntaxin, SNAP25, and Synaptobrevin), SNARE-interacting proteins Synaptotagmin, Munc13, Munc18, Complexin, and NSF are designated to ribs and/or pins. Rab3A and Rabphillin-3A are designated to top-masts and/or booms and/or spars. RIM, Bassoon, and Piccolo are designated to beams, steps, masts, ribs, spars, booms, and top-masts. Spectrin is designated to beams. Lastly, the luminal portions of SV2 are thought to form the bulk of the observed synaptic vesicle luminal filaments. The goal here is to help direct future studies that aim to bridge Active Zone Material structure, biochemistry, and function to ultimately determine how it regulates the trafficking events in vivo that lead to neurotransmitter secretion.

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