scholarly journals Examining molecular determinants underlying heterogeneity of synaptic release probability using optical quantal imaging

2017 ◽  
Author(s):  
Yulia Akbergenova ◽  
Yao V. Zhang ◽  
Shirley Weiss-Sharabi ◽  
Karen L. Cunningham ◽  
J. Troy Littleton
Keyword(s):  
Glutamate Receptor ◽  
Neuromuscular Junctions ◽  
Receptor Activation ◽  
Distinct Pattern ◽  
Strongly Correlated ◽  
Release Probability ◽  
Molecular Determinants ◽  
Synaptotagmin 1 ◽  
Developmental Analysis ◽  
Single Vesicle

AbstractNeurons communicate through neurotransmitter release at specialized synaptic regions known as active zones (AZs). Using transgenic biosensors to image postsynaptic glutamate receptor activation following single vesicle fusion events at Drosophila neuromuscular junctions, we analyzed release probability (Pr) maps for a defined connection with ~300 AZs between synaptic partners. Although Pr was very heterogeneous, it represented a stable and unique feature of each AZ. Pr heterogeneity was not abolished in mutants lacking Synaptotagmin 1, suggesting the AZ itself is likely to harbor a key determinant(s). Indeed, AZ Pr was strongly correlated with presynaptic Ca2+ channel density and Ca2+ influx at single release sites. In addition, Pr variability was reflected in the postsynaptic compartment, as high Pr AZs displayed a distinct pattern of glutamate receptor clustering. Developmental analysis suggests that high Pr sites emerge from earlier formed AZs, with a temporal maturation in transmission strength occurring over several days.

scholarly journals Characterization of developmental and molecular factors underlying release heterogeneity at Drosophila synapses

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Yulia Akbergenova ◽  
Karen L Cunningham ◽  
Yao V Zhang ◽  
Shirley Weiss ◽  
J Troy Littleton
Keyword(s):  
Glutamate Receptor ◽  
Neuromuscular Junctions ◽  
Field Size ◽  
High Frequency Stimulation ◽  
Receptor Subtype ◽  
Receptor Field ◽  
Synaptotagmin 1 ◽  
Synapse Maturation ◽  
Frequency Stimulation ◽  
Synaptic Vesicle Fusion

Neurons communicate through neurotransmitter release at specialized synaptic regions known as active zones (AZs). Using biosensors to visualize single synaptic vesicle fusion events at Drosophila neuromuscular junctions, we analyzed the developmental and molecular determinants of release probability (Pr) for a defined connection with ~300 AZs. Pr was heterogeneous but represented a stable feature of each AZ. Pr remained stable during high frequency stimulation and retained heterogeneity in mutants lacking the Ca2+ sensor Synaptotagmin 1. Pr correlated with both presynaptic Ca2+ channel abundance and Ca2+ influx at individual release sites. Pr heterogeneity also correlated with glutamate receptor abundance, with high Pr connections developing receptor subtype segregation. Intravital imaging throughout development revealed that AZs acquire high Pr during a multi-day maturation period, with Pr heterogeneity largely reflecting AZ age. The rate of synapse maturation was activity-dependent, as both increases and decreases in neuronal activity modulated glutamate receptor field size and segregation.

scholarly journals Molecular Determinants of Complexin Clamping in Reconstituted Single-Vesicle Fusion

2021 ◽  
Author(s):  
Manindra Bera ◽  
Sathish Ramakrishnan ◽  
Jeff Coleman ◽  
Shyam S Krishnakumar ◽  
James E Rothman
Keyword(s):  
Specific Interaction ◽  
Vesicle Fusion ◽  
Assembly Process ◽  
Inhibitory Function ◽  
Physiological Relevance ◽  
Vesicular Release ◽  
Molecular Determinants ◽  
Synaptotagmin 1 ◽  
Single Vesicle

Previously we reported that Synaptotagmin-1 and Complexin synergistically clamp the SNARE assembly process to generate and maintain a pool of docked vesicles that fuse rapidly and synchronously upon Ca2+ influx (Ramakrishnan et al. 2020). Here using the same in vitro single-vesicle fusion assay, we establish the molecular details of the Complexin clamp and its physiological relevance. We find that a delay in fusion kinetics, likely imparted by Synaptotagmin-1, is needed for Complexin to block fusion. Systematic truncation/mutational analyses reveal that continuous alpha-helical accessory-central domains of Complexin are essential for its inhibitory function and specific interaction of the accessory helix with the SNAREpins, analogous to the trans clamping model, enhances this functionality. The c-terminal domain promotes clamping by locally elevating Complexin concentration through interactions with the membrane. Further, we find that Complexin likely contributes to rapid Ca2+-synchronized vesicular release by preventing un-initiated fusion rather than by directly facilitating vesicle fusion.

scholarly journals Dual leucine zipper kinase is required for excitotoxicity-induced neuronal degeneration

2013 ◽  
Vol 210 (12) ◽  
pp. 2553-2567 ◽  
Author(s):  
Christine D. Pozniak ◽  
Arundhati Sengupta Ghosh ◽  
Alvin Gogineni ◽  
Jesse E. Hanson ◽  
Seung-Hye Lee ◽  
...  
Keyword(s):  
Glutamate Receptor ◽  
Leucine Zipper ◽  
Neuronal Degeneration ◽  
Neuronal Loss ◽  
Receptor Activation ◽  
Scaffolding Protein ◽  
Glutamate Signaling ◽  
Postsynaptic Density Proteins ◽  
Primary Driver

Excessive glutamate signaling is thought to underlie neurodegeneration in multiple contexts, yet the pro-degenerative signaling pathways downstream of glutamate receptor activation are not well defined. We show that dual leucine zipper kinase (DLK) is essential for excitotoxicity-induced degeneration of neurons in vivo. In mature neurons, DLK is present in the synapse and interacts with multiple known postsynaptic density proteins including the scaffolding protein PSD-95. To examine DLK function in the adult, DLK-inducible knockout mice were generated through Tamoxifen-induced activation of Cre-ERT in mice containing a floxed DLK allele, which circumvents the neonatal lethality associated with germline deletion. DLK-inducible knockouts displayed a modest increase in basal synaptic transmission but had an attenuation of the JNK/c-Jun stress response pathway activation and significantly reduced neuronal degeneration after kainic acid–induced seizures. Together, these data demonstrate that DLK is a critical upstream regulator of JNK-mediated neurodegeneration downstream of glutamate receptor hyper-activation and represents an attractive target for the treatment of indications where excitotoxicity is a primary driver of neuronal loss.

Extracellular taurine increase in rat hippocampus evoked by specific glutamate receptor activation is related to the excitatory potency of glutamate agonists

1989 ◽  
Vol 102 (1) ◽  
pp. 64-69 ◽  
Author(s):  
Nieves Menéndez ◽  
Oscar Herreras ◽  
JoséM. Solis ◽  
Antonio S. Herranz ◽  
Rafael Martín del Río
Keyword(s):  
Glutamate Receptor ◽  
Receptor Activation ◽  
Rat Hippocampus ◽  
Glutamate Agonists

scholarly journals The vesicular release probability sets the strength of individual Schaffer collateral synapses

2020 ◽  
Author(s):  
Céline D. Dürst ◽  
J. Simon Wiegert ◽  
Christian Schulze ◽  
Nordine Helassa ◽  
Katalin Török ◽  
...  
Keyword(s):  
Schaffer Collateral ◽  
Release Probability ◽  
Single Axon ◽  
Vesicular Release ◽  
High Calcium ◽  
Fusion Site ◽  
Presynaptic Boutons ◽  
The Brain ◽  
Measured Response ◽  
Single Vesicle

AbstractInformation processing in the brain is controlled by quantal release of neurotransmitters, a tightly regulated process. Even in a single axon, presynaptic boutons differ in the number of docked vesicles, but it is not known if the vesicular release probability (pves) is homogenous or variable between individual boutons. We optically measured evoked transmitter release at individual Schaffer collateral synapses using the genetically encoded glutamate sensor iGluSnFR, localizing the fusion site on the bouton with high spatiotemporal precision. Fitting a binomial model to measured response amplitude distributions allowed us to extract the quantal parameters N, pves, and q. Schaffer collateral boutons typically released only a single vesicle under low pves conditions and switched to multivesicular release in high calcium saline. We found that pves was highly variable between individual boutons and had a dominant impact on presynaptic output.

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