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Neuron Jun 2021Optical manipulations of genetically defined cell types have generated significant insights into the dynamics of neural circuits. While optogenetic activation has been...
Optical manipulations of genetically defined cell types have generated significant insights into the dynamics of neural circuits. While optogenetic activation has been relatively straightforward, rapid and reversible synaptic inhibition has proven more elusive. Here, we leveraged the natural ability of inhibitory presynaptic GPCRs to suppress synaptic transmission and characterize parapinopsin (PPO) as a GPCR-based opsin for terminal inhibition. PPO is a photoswitchable opsin that couples to G signaling cascades and is rapidly activated by pulsed blue light, switched off with amber light, and effective for repeated, prolonged, and reversible inhibition. PPO rapidly and reversibly inhibits glutamate, GABA, and dopamine release at presynaptic terminals. Furthermore, PPO alters reward behaviors in a time-locked and reversible manner in vivo. These results demonstrate that PPO fills a significant gap in the neuroscience toolkit for rapid and reversible synaptic inhibition and has broad utility for spatiotemporal control of inhibitory GPCR signaling cascades.
Topics: Animals; Dopamine; Exocytosis; Fish Proteins; Glutamic Acid; HEK293 Cells; HeLa Cells; Humans; Male; Mice; Neural Inhibition; Optogenetics; Presynaptic Terminals; Receptors, G-Protein-Coupled; Reward; Rod Opsins; Synaptic Transmission; gamma-Aminobutyric Acid
PubMed: 33979635
DOI: 10.1016/j.neuron.2021.04.026 -
The Journal of Physiology Feb 2016Synaptic communication between neurons is a highly dynamic process involving specialized structures. At the level of the presynaptic terminal, neurotransmission is... (Review)
Review
Synaptic communication between neurons is a highly dynamic process involving specialized structures. At the level of the presynaptic terminal, neurotransmission is ensured by fusion of vesicles to the membrane, which releases neurotransmitter in the synaptic cleft. Depending on the level of activity experienced by the terminal, the spatiotemporal properties of calcium invasion will dictate the timing and the number of vesicles that need to be released. Diverse presynaptic firing patterns are translated to neurotransmitter release with a distinct temporal feature. Complex patterns of neurotransmitter release can be achieved when different vesicles respond to distinct calcium dynamics in the presynaptic terminal. Specific vesicles from different pools are recruited during various modes of release as the particular molecular composition of their membrane proteins define their functional properties. Such diversity endows the presynaptic terminal with the ability to respond to distinct physiological signals via the mobilization of specific subpopulation of vesicles. There are several mechanisms by which a diverse vesicle population could be generated in single presynaptic terminals, including distinct recycling pathways that utilize various adaptor proteins. Several additional factors could potentially contribute to the development of a heterogeneous vesicle pool such as specialized release sites, spatial segregation within the terminal and specialized delivery pathways. Among these factors molecular heterogeneity plays a central role in defining the functional properties of different subpopulations of vesicles.
Topics: Animals; Calcium; Exocytosis; Humans; Presynaptic Terminals; Synaptic Transmission; Synaptic Vesicles
PubMed: 26614712
DOI: 10.1113/JP270194 -
Neuron Mar 2021Tau is a major driver of neurodegeneration and is implicated in over 20 diseases. Tauopathies are characterized by synaptic loss and neuroinflammation, but it is unclear...
Tau is a major driver of neurodegeneration and is implicated in over 20 diseases. Tauopathies are characterized by synaptic loss and neuroinflammation, but it is unclear if these pathological events are causally linked. Tau binds to Synaptogyrin-3 on synaptic vesicles. Here, we interfered with this function to determine the role of pathogenic Tau at pre-synaptic terminals. We show that heterozygous knockout of synaptogyrin-3 is benign in mice but strongly rescues mutant Tau-induced defects in long-term synaptic plasticity and working memory. It also significantly rescues the pre- and post-synaptic loss caused by mutant Tau. However, Tau-induced neuroinflammation remains clearly upregulated when we remove the expression of one allele of synaptogyrin-3. Hence neuroinflammation is not sufficient to cause synaptic loss, and these processes are separately induced in response to mutant Tau. In addition, the pre-synaptic defects caused by mutant Tau are enough to drive defects in cognitive tasks.
Topics: Animals; Encephalitis; Female; Hippocampus; Male; Memory Disorders; Mice, Knockout; Microglia; Neuronal Plasticity; Presynaptic Terminals; Synaptogyrins; tau Proteins; Mice
PubMed: 33472038
DOI: 10.1016/j.neuron.2020.12.016 -
The Journal of Neuroscience : the... Mar 2022Efficient and reliable neurotransmission requires precise coupling between action potentials (APs), Ca entry and neurotransmitter release. However, Ca requirements for...
Efficient and reliable neurotransmission requires precise coupling between action potentials (APs), Ca entry and neurotransmitter release. However, Ca requirements for release, including the number of channels required, their subtypes, and their location with respect to primed vesicles, remains to be precisely defined for central synapses. Indeed, Ca entry may occur through small numbers or even single open Ca channels, but these questions remain largely unexplored in simple active zone (AZ) synapses common in the nervous system, and key to addressing Ca channel and synaptic dysfunction underlying numerous neurologic and neuropsychiatric disorders. Here, we present single channel analysis of evoked AZ Ca entry, using cell-attached patch clamp and lattice light-sheet microscopy (LLSM), resolving small channel numbers evoking Ca entry following depolarization, at single AZs in individual central lamprey reticulospinal presynaptic terminals from male and females. We show a small pool (mean of 23) of Ca channels at each terminal, comprising N-(CaV2.2), P/Q-(CaV2.1), and R-(CaV2.3) subtypes, available to gate neurotransmitter release. Significantly, of this pool only one to seven channels (mean of 4) open on depolarization. High temporal fidelity lattice light-sheet imaging reveals AP-evoked Ca transients exhibiting quantal amplitude variations of 0-6 event sizes between individual APs and stochastic variation of precise locations of Ca entry within the AZ. Further, total Ca channel numbers at each AZ correlate to the number of presynaptic primed synaptic vesicles. Dispersion of channel openings across the AZ and the similar number of primed vesicles and channels indicate that Ca entry via as few as one channel may trigger neurotransmitter release. Presynaptic Ca entry through voltage-gated calcium channels (VGCCs) causes neurotransmitter release. To understand neurotransmission, its modulation, and plasticity, we must quantify Ca entry and its relationship to vesicle fusion. This requires direct recordings from active zones (AZs), previously possible only at calyceal terminals containing many AZs, where few channels open following action potentials (APs; Sheng et al., 2012), and even single channel openings may trigger release (Stanley, 1991, 1993). However, recording from more conventional terminals with single AZs commonly found centrally has thus far been impossible. We addressed this by cell-attached recordings from acutely dissociated single lamprey giant axon AZs, and by lattice light sheet microscopy of presynaptic Ca entry. We demonstrate nanodomains of presynaptic VGCCs coupling with primed vesicles with 1:1 stoichiometry.
Topics: Animals; Calcium; Female; Lampreys; Male; Neurotransmitter Agents; Presynaptic Terminals; Synaptic Transmission; Synaptic Vesicles
PubMed: 35063999
DOI: 10.1523/JNEUROSCI.2207-21.2022 -
PLoS Biology Dec 2023Neuronal development orchestrates the formation of an enormous number of synapses that connect the nervous system. In developing presynapses, the core active zone...
Neuronal development orchestrates the formation of an enormous number of synapses that connect the nervous system. In developing presynapses, the core active zone structure has been found to assemble through liquid-liquid phase separation. Here, we find that the phase separation of Caenorhabditis elegans SYD-2/Liprin-α, a key active zone scaffold, is controlled by phosphorylation. We identify the SAD-1 kinase as a regulator of SYD-2 phase separation and determine presynaptic assembly is impaired in sad-1 mutants and increased by overactivation of SAD-1. Using phosphoproteomics, we find SAD-1 phosphorylates SYD-2 on 3 sites that are critical to activate phase separation. Mechanistically, SAD-1 phosphorylation relieves a binding interaction between 2 folded domains in SYD-2 that inhibits phase separation by an intrinsically disordered region (IDR). We find synaptic cell adhesion molecules localize SAD-1 to nascent synapses upstream of active zone formation. We conclude that SAD-1 phosphorylates SYD-2 at developing synapses, activating its phase separation and active zone assembly.
Topics: Animals; Presynaptic Terminals; Caenorhabditis elegans Proteins; Synapses; Caenorhabditis elegans; Intercellular Signaling Peptides and Proteins
PubMed: 38048304
DOI: 10.1371/journal.pbio.3002421 -
Nature Nov 2016The effects of Δ-tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis, are a pressing concern for global mental health. Patterns of cannabis use are... (Review)
Review
The effects of Δ-tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis, are a pressing concern for global mental health. Patterns of cannabis use are changing drastically owing to legalization, the availability of synthetic analogues (commonly termed spice), cannavaping and an emphasis on the purported therapeutic effects of cannabis. Many of the reinforcing effects of THC are mediated by the dopamine system. Owing to the complexity of the cannabinoid-dopamine interactions that take place, there is conflicting evidence from human and animal studies concerning the effects of THC on the dopamine system. Acute THC administration causes increased dopamine release and neuron activity, whereas long-term use is associated with blunting of the dopamine system. Future research must examine the long-term and developmental dopaminergic effects of THC.
Topics: Animals; Behavior, Animal; Brain; Cell Shape; Dopamine; Dopaminergic Neurons; Dronabinol; Eating; Humans; Post-Synaptic Density; Presynaptic Terminals; Receptor, Cannabinoid, CB1
PubMed: 27853201
DOI: 10.1038/nature20153 -
Cells Mar 2021In presynaptic terminals, synaptic vesicles (SVs) are found in a discrete cluster that includes a reserve pool that is mobilized during synaptic activity. Synapsins... (Review)
Review
In presynaptic terminals, synaptic vesicles (SVs) are found in a discrete cluster that includes a reserve pool that is mobilized during synaptic activity. Synapsins serve as a key protein for maintaining SVs within this reserve pool, but the mechanism that allows synapsins to do this is unclear. This mechanism is likely to involve synapsins either cross-linking SVs, thereby anchoring SVs to each other, or creating a liquid phase that allows SVs to float within a synapsin droplet. Here, we summarize what is known about the role of synapsins in clustering of SVs and evaluate experimental evidence supporting these two models.
Topics: Animals; Exocytosis; Humans; Models, Neurological; Presynaptic Terminals; Protein Binding; Protein Transport; Synapsins; Synaptic Transmission; Synaptic Vesicles
PubMed: 33809712
DOI: 10.3390/cells10030658 -
Invertebrate Neuroscience : IN Mar 2018Synapses are specialized contact sites that mediate information flow between neurons and their targets. Important physical interactions across the synapse are mediated... (Review)
Review
Synapses are specialized contact sites that mediate information flow between neurons and their targets. Important physical interactions across the synapse are mediated by synaptic adhesion molecules. These adhesions regulate formation of synapses during development and play a role during mature synaptic function. Importantly, genes regulating synaptogenesis and axon regeneration are conserved across the animal phyla. Genetic screens in the nematode Caenorhabditis elegans have identified a number of molecules required for synapse patterning and assembly. C. elegans is able to survive even with its neuronal function severely compromised. This is in comparison with Drosophila and mice where increased complexity makes them less tolerant to impaired function. Although this fact may reflect differences in the function of the homologous proteins in the synapses between these organisms, the most likely interpretation is that many of these components are equally important, but not absolutely essential, for synaptic transmission to support the relatively undemanding life style of laboratory maintained C. elegans. Here, we review research on the major group of synaptic proteins, involved in the presynaptic machinery in C. elegans, showing a strong conservation between higher organisms and highlight how C. elegans can be used as an informative tool for dissecting synaptic components, based on a simple nervous system organization.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Neurons; Presynaptic Terminals; Synapses; Synaptic Transmission
PubMed: 29532181
DOI: 10.1007/s10158-018-0207-5 -
Journal of Alzheimer's Disease : JAD 2024A key aspect of synaptic dysfunction in Alzheimer's disease (AD) is loss of synaptic proteins. Previous publications showed that the presynaptic machinery is more... (Meta-Analysis)
Meta-Analysis
BACKGROUND
A key aspect of synaptic dysfunction in Alzheimer's disease (AD) is loss of synaptic proteins. Previous publications showed that the presynaptic machinery is more strongly affected than postsynaptic proteins. However, it has also been reported that presynaptic protein loss is highly variable and shows region- and protein-specificity.
OBJECTIVE
The objective of this meta-analysis was to provide an update on the available literature and to further characterize patterns of presynaptic protein loss in AD.
METHODS
Systematic literature search was conducted for studies published between 2015-2022 which quantified presynaptic proteins in postmortem tissue from AD patients and healthy controls. Three-level random effects meta-analyses of twenty-two identified studies was performed to characterize overall presynaptic protein loss and changes in specific regions, proteins, protein families, and functional categories.
RESULTS
Meta-analysis confirmed overall loss of presynaptic proteins in AD patients. Subgroup analysis revealed region specificity of protein loss, with largest effects in temporal and frontal cortex. Results concerning different groups of proteins were also highly variable. Strongest and most consistently affected was the family of synaptosome associated proteins, especially SNAP25. Among the most severely affected were proteins regulating dense core vesicle exocytosis and the synaptic vesicle cycle.
CONCLUSIONS
Results confirm previous literature related to presynaptic protein loss in AD patients and provide further in-depth characterization of most affected proteins and presynaptic functions.
Topics: Humans; Alzheimer Disease; Proteins; Presynaptic Terminals
PubMed: 38073390
DOI: 10.3233/JAD-231034 -
Molecular Neurobiology Jun 2018Among all the biological systems in vertebrates, the central nervous system (CNS) is the most complex, and its function depends on specialized contacts among neurons... (Review)
Review
Among all the biological systems in vertebrates, the central nervous system (CNS) is the most complex, and its function depends on specialized contacts among neurons called synapses. The assembly and organization of synapses must be exquisitely regulated for a normal brain function and network activity. There has been a tremendous effort in recent decades to understand the molecular and cellular mechanisms participating in the formation of new synapses and their organization, maintenance, and regulation. At the vertebrate presynapses, proteins such as Piccolo, Bassoon, RIM, RIM-BPs, CAST/ELKS, liprin-α, and Munc13 are constant residents and participate in multiple and dynamic interactions with other regulatory proteins, which define network activity and normal brain function. Here, we review the function of these active zone (AZ) proteins and diverse factors involved in AZ assembly and maintenance, with an emphasis on axonal trafficking of precursor vesicles, protein homo- and hetero-oligomeric interactions as a mechanism of AZ trapping and stabilization, and the role of F-actin in presynaptic assembly and its modulation by Wnt signaling.
Topics: Animals; Models, Biological; Nerve Tissue Proteins; Presynaptic Terminals; Vertebrates; Wnt Signaling Pathway
PubMed: 28685386
DOI: 10.1007/s12035-017-0661-9