Regulation of Synaptic Vesicle Docking by Different Classes of Macromolecules in Active Zone Material

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.

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Reconstructing essential active zone functions within a synapse

10.1101/2021.11.21.469466 ◽

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.

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Faculty Opinions recommendation of 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.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.727964942.793539677 ◽

2017 ◽

Author(s):

Jens Rettig ◽

David Stevens

Keyword(s):

Synaptic Vesicle ◽

Active Zone ◽

Vesicle Fusion ◽

Subunit C ◽

Vesicle Docking ◽

C Terminus ◽

Presynaptic Active Zone ◽

Synaptic Vesicle Fusion ◽

Α1 Subunit

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Liprin-α3 controls vesicle docking and exocytosis at the active zone of hippocampal synapses

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719012115 ◽

2018 ◽

Vol 115 (9) ◽

pp. 2234-2239 ◽

Cited By ~ 22

Author(s):

Man Yan Wong ◽

Changliang Liu ◽

Shan Shan H. Wang ◽

Aram C. F. Roquas ◽

Stephen C. Fowler ◽

...

Keyword(s):

Synaptic Vesicle ◽

Active Zone ◽

Hippocampal Neurons ◽

Stimulated Emission ◽

Loss Of Function ◽

Zone Structure ◽

Vesicle Docking ◽

Synaptic Vesicle Exocytosis ◽

Vesicle Exocytosis ◽

And Function

The presynaptic active zone provides sites for vesicle docking and release at central nervous synapses and is essential for speed and accuracy of synaptic transmission. Liprin-α binds to several active zone proteins, and loss-of-function studies in invertebrates established important roles for Liprin-α in neurodevelopment and active zone assembly. However, Liprin-α localization and functions in vertebrates have remained unclear. We used stimulated emission depletion superresolution microscopy to systematically determine the localization of Liprin-α2 and Liprin-α3, the two predominant Liprin-α proteins in the vertebrate brain, relative to other active-zone proteins. Both proteins were widely distributed in hippocampal nerve terminals, and Liprin-α3, but not Liprin-α2, had a prominent component that colocalized with the active-zone proteins Bassoon, RIM, Munc13, RIM-BP, and ELKS. To assess Liprin-α3 functions, we generated Liprin-α3–KO mice by using CRISPR/Cas9 gene editing. We found reduced synaptic vesicle tethering and docking in hippocampal neurons of Liprin-α3–KO mice, and synaptic vesicle exocytosis was impaired. Liprin-α3 KO also led to mild alterations in active zone structure, accompanied by translocation of Liprin-α2 to active zones. These findings establish important roles for Liprin-α3 in active-zone assembly and function, and suggest that interplay between various Liprin-α proteins controls their active-zone localization.

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