scholarly journals Activity-dependent nucleation of dynamic microtubules at presynaptic boutons is required for neurotransmission

2019 ◽  
Author(s):  
Xiaoyi Qu ◽  
Atul Kumar ◽  
Heike Blockus ◽  
Clarissa Waites ◽  
Francesca Bartolini
Keyword(s):  
Synaptic Vesicle ◽  
Neuronal Activity ◽  
Neurotransmitter Release ◽  
Hippocampal Neurons ◽  
De Novo ◽  
List Type ◽  
Neuronal Function ◽  
Presynaptic Boutons ◽  
Rate Limiting ◽  
Activity Dependent

SUMMARYControl of microtubule (MT) dynamics is critical for neuronal function. Whether MT nucleation is regulated at presynaptic boutons and influences overall presynaptic activity remains unknown. By visualizing MT dynamics at individual excitatory en passant boutons in axons of hippocampal neurons we found that MTs preferentially grow from presynaptic boutons as a result of γ-tubulin and augmin-dependent nucleation. MT nucleation at boutons is promoted by neuronal activity, functionally coupled to synaptic vesicle (SV) transport, and required for neurotransmission. Hence, en passant boutons act as hotspots for activity-dependent MT nucleation, which is required for neurotransmission by providing the tracks for a rate-limiting supply of SVs to sites of neurotransmitter release.HighlightsExcitatory boutons are hotspots for neuronal activity-induced γ-tubulin dependent MT nucleationThe augmin complex is required for the correct polarity of presynaptic de novo nucleated MTsPresynaptic MT nucleation promotes SV motility and exocytosis at sites of releaseIn BriefOur results demonstrate that excitatory en passant boutons are hotspots for neuronal activity-induced γ-tubulin- and augmin-dependent oriented MT nucleation, and that the resulting presynaptic de novo nucleated MTs promote inter-bouton SV motility which is rate-limiting for neurotransmitter release.

scholarly journals Systematic identification of 3′-UTR regulatory elements in activity-dependent mRNA stability in hippocampal neurons

2014 ◽  
Vol 369 (1652) ◽  
pp. 20130509 ◽  
Author(s):  
Jonathan E. Cohen ◽  
Philip R. Lee ◽  
R. Douglas Fields
Keyword(s):  
Neuronal Activity ◽  
Mrna Stability ◽  
Hippocampal Neurons ◽  
Transcriptional Control ◽  
Regulatory Elements ◽  
Memory Storage ◽  
Long Term Memory ◽  
Synaptic Connections ◽  
Activity Dependent

Ongoing neuronal activity during development and plasticity acts to refine synaptic connections and contributes to the induction of plasticity and ultimately long-term memory storage. Activity-dependent, post-transcriptional control of mRNAs occurs through transport to axonal and dendritic compartments, local translation and mRNA stability. We have identified a mechanism that contributes to activity-dependent regulation of mRNA stability during synaptic plasticity in rat hippocampal neurons. In this study, we demonstrate rapid, post-transcriptional control over process-enriched mRNAs by neuronal activity. Systematic analysis of the 3′-UTRs of destabilized transcripts, identifies enrichment in sequence motifs corresponding to microRNA (miRNA)-binding sites. The miRNAs that were identified, miR-326-3p/miR-330-5p, miR-485-5p, miR-666-3p and miR-761 are predicted to regulate networks of genes important in plasticity and development. We find that these miRNAs are developmentally regulated in the hippocampus, many increasing by postnatal day 14. We further find that miR-485-5p controls NGF-induced neurite outgrowth in PC12 cells, tau expression and axonal development in hippocampal neurons. miRNAs can function at the synapse to rapidly control and affect short- and long-term changes at the synapse. These processes likely occur during refinement of synaptic connections and contribute to the induction of plasticity and learning and memory.

Remodeling of astrocytes, a prerequisite for synapse turnover in the adult brain? Insights from the oxytocin system of the hypothalamus

2006 ◽  
Vol 290 (5) ◽  
pp. R1175-R1182 ◽  
Author(s):  
Dionysia T. Theodosis ◽  
Andrei Trailin ◽  
Dominique A. Poulain
Keyword(s):  
Synaptic Plasticity ◽  
Synaptic Transmission ◽  
Neuronal Activity ◽  
Adult Brain ◽  
Synaptic Connectivity ◽  
Excitatory Synapses ◽  
Neuronal Function ◽  
Physiological Conditions ◽  
Baseline Levels ◽  
Activity Dependent

Neurons, including their synapses, are generally ensheathed by fine processes of astrocytes, but this glial coverage can be altered under different physiological conditions that modify neuronal activity. Changes in synaptic connectivity accompany astrocytic transformations so that an increased number of synapses are associated with reduced astrocytic coverage of postsynaptic elements, whereas synaptic numbers are reduced on reestablishment of glial coverage. A system that exemplifies activity-dependent structural synaptic plasticity in the adult brain is the hypothalamo-neurohypophysial system, and in particular, its oxytocin component. Under strong, prolonged activation (parturition, lactation, chronic dehydration), extensive portions of somatic and dendritic surfaces of magnocellular oxytocin neurons are freed of intervening astrocytic processes and become directly juxtaposed. Concurrently, they are contacted by an increased number of inhibitory and excitatory synapses. Once stimulation is over, astrocytic processes again cover oxytocinergic surfaces and synaptic numbers return to baseline levels. Such observations indicate that glial ensheathment of neurons is of consequence to neuronal function, not only directly, for example by modifying synaptic transmission, but indirectly as well, by preparing neuronal surfaces for synapse turnover.

scholarly journals Inositol pyrophosphates inhibit synaptotagmin-dependent exocytosis

2016 ◽  
Vol 113 (29) ◽  
pp. 8314-8319 ◽  
Author(s):  
Tae-Sun Lee ◽  
Joo-Young Lee ◽  
Jae Won Kyung ◽  
Yoosoo Yang ◽  
Seung Ju Park ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
Hippocampal Neurons ◽  
Vesicle Fusion ◽  
Synaptic Membrane ◽  
Synaptic Vesicle Exocytosis ◽  
Dependent Inhibition ◽  
Vesicle Exocytosis ◽  
Inositol Pyrophosphates

Inositol pyrophosphates such as 5-diphosphoinositol pentakisphosphate (5-IP7) are highly energetic inositol metabolites containing phosphoanhydride bonds. Although inositol pyrophosphates are known to regulate various biological events, including growth, survival, and metabolism, the molecular sites of 5-IP7 action in vesicle trafficking have remained largely elusive. We report here that elevated 5-IP7 levels, caused by overexpression of inositol hexakisphosphate (IP6) kinase 1 (IP6K1), suppressed depolarization-induced neurotransmitter release from PC12 cells. Conversely, IP6K1 depletion decreased intracellular 5-IP7 concentrations, leading to increased neurotransmitter release. Consistently, knockdown of IP6K1 in cultured hippocampal neurons augmented action potential-driven synaptic vesicle exocytosis at synapses. Using a FRET-based in vitro vesicle fusion assay, we found that 5-IP7, but not 1-IP7, exhibited significantly higher inhibitory activity toward synaptic vesicle exocytosis than IP6. Synaptotagmin 1 (Syt1), a Ca2+ sensor essential for synaptic membrane fusion, was identified as a molecular target of 5-IP7. Notably, 5-IP7 showed a 45-fold higher binding affinity for Syt1 compared with IP6. In addition, 5-IP7–dependent inhibition of synaptic vesicle fusion was abolished by increasing Ca2+ levels. Thus, 5-IP7 appears to act through Syt1 binding to interfere with the fusogenic activity of Ca2+. These findings reveal a role of 5-IP7 as a potent inhibitor of Syt1 in controlling the synaptic exocytotic pathway and expand our understanding of the signaling mechanisms of inositol pyrophosphates.

scholarly journals Light induced synaptic vesicle autophagy

2018 ◽  
Author(s):  
Sheila Hoffmann ◽  
Marta Orlando ◽  
Ewa Andrzejak ◽  
Thorsten Trimbuch ◽  
Christian Rosenmund ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Real Time ◽  
Hippocampal Neurons ◽  
Synaptic Function ◽  
Synaptic Proteins ◽  
Oxygen Species ◽  
Local Damage ◽  
Glutamatergic Synapses ◽  
Presynaptic Boutons ◽  
Presynaptic Proteins

AbstractThe regulated turnover of synaptic vesicle (SV) proteins is thought to involve the ubiquitin dependent tagging and degradation through endo-lysosomal and autophagy pathways. Yet, it remains unclear which of these pathways are used, when they become activated and whether SVs are cleared en-mass together with SV proteins or whether both are degraded selectively. Equally puzzling is how quickly these systems can be activated and whether they function in real time to support synaptic health. To address these questions, we have developed an imaging based system that simultaneously tags presynaptic proteins while monitoring autophagy. Moreover, by tagging SV proteins with a light activated reactive oxygen species (ROS) generator, Supernova, it was possible to temporally control the damage to specific SV proteins and assess their consequence to autophagy mediated clearance mechanisms and synaptic function. Our results show that, in mouse hippocampal neurons, presynaptic autophagy can be induced in as little as 5-10 minutes and eliminates primarily the damaged protein rather than the SV en-mass. Importantly, we also find that autophagy is essential for synaptic function, as light-induced damage to e.g. Synaptophysin only compromises synaptic function when autophagy is simultaneously blocked. These data support the concept that presynaptic boutons have a robust highly regulated clearance system to maintain not only synapse integrity, but also synaptic function.Significance StatementThe real-time surveillance and clearance of synaptic proteins is thought to be vital to the health, functionality and integrity of vertebrate synapses and is compromised in neurodegenerative disorders, yet the fundamental mechanisms regulating these systems remain enigmatic. Our analysis reveals that presynaptic autophagy is a critical part of a real-time clearance system at glutamatergic synapses capable of responding to local damage of synaptic vesicle proteins within minutes and to be critical for the ongoing functionality of these synapses. These data indicate that synapse autophagy is not only locally regulated but also crucial for the health and functionality of vertebrate presynaptic boutons.

scholarly journals Neuronal activity remodels the F-actin based submembrane lattice in dendrites but not axons of hippocampal neurons

2020 ◽  
Author(s):  
Flavie Lavoie-Cardinal ◽  
Anthony Bilodeau ◽  
Mado Lemieux ◽  
Marc-André Gardner ◽  
Theresa Wiesner ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Neuronal Activity ◽  
Protein Trafficking ◽  
Hippocampal Neurons ◽  
Actin Remodeling ◽  
Fluorescence Nanoscopy ◽  
Segmentation Approach ◽  
Weakly Supervised ◽  
Activity Dependent ◽  
Actin Rings

AbstractThe nanoscale organization of the F-actin cytoskeleton in neurons comprises membrane-associated periodical rings, bundles, and longitudinal fibers. The F-actin rings have been observed predominantly in axons but only sporadically in dendrites, where fluorescence nanoscopy reveals various patterns of F-actin arranged in mixed patches. These complex dendritic F-actin patterns pose a challenge for investigating quantitatively their regulatory mechanisms. We developed here a weakly supervised deep learning segmentation approach of fluorescence nanoscopy images of F-actin in cultured hippocampal neurons. This approach enabled the quantitative assessment of F-actin remodeling, revealing the disappearance of the rings during neuronal activity in dendrites, but not in axons. The dendritic F-actin cytoskeleton of activated neurons remodeled into longitudinal fibers. We show that this activity-dependent remodeling involves Ca2+ and NMDA-dependent mechanisms. This highly dynamic restructuring of dendritic F-actin based submembrane lattice into longitudinal fibers may serve to support activity-dependent membrane remodeling, protein trafficking and neuronal plasticity.

scholarly journals Light Stimulation Parameters Determine Neuron Dynamic Characteristics

2019 ◽  
Vol 9 (18) ◽  
pp. 3673 ◽  
Author(s):  
Alexander Erofeev ◽  
Evgenii Gerasimov ◽  
Anastasia Lavrova ◽  
Anastasia Bolshakova ◽  
Eugene Postnikov ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Light Pulse ◽  
Hippocampal Neurons ◽  
Primary Cultures ◽  
Optimal Parameters ◽  
Neuronal Function ◽  
Light Stimulation ◽  
Stimulation Parameters ◽  
Transgenic Lines ◽  
Bell Shaped Curve

Optogenetics is a recently developed technique that is widely used to study neuronal function. In optogenetic experiments, neurons encode opsins (channelrhodopsins, halorhodopsins or their derivatives) by means of viruses, plasmids or genetic modification (transgenic lines). Channelrhodopsin are light activated ion channels. Their expression in neurons allows light-dependent control of neuronal activity. The duration and frequency of light stimulation in optogenetic experiments is critical for stable, robust and reproducible experiments. In this study, we performed systematic analyses of these parameters using primary cultures of hippocampal neurons transfected with channelrhodopsin-2 (ChR2). The main goal of this work was to identify the optimal parameters of light stimulation that would result in stable neuronal activity during a repeated light pulse train. We demonstrated that the dependency of the photocurrent on the light pulse duration is described by a right-skewed bell-shaped curve, while the dependence on the stimulus intensity is close to linear. We established that a duration between 10–30 ms of stimulation was the minimal time necessary to achieve a full response. Obtained results will be useful in planning and interpretation of optogenetic experiments.

scholarly journals Ps in the (Channel) Pod Are Not Alike …

2007 ◽  
Vol 7 (5) ◽  
pp. 136-137
Author(s):  
Yoav Noam ◽  
Tallie Z. Baram
Keyword(s):  
Neuronal Activity ◽  
Hippocampal Neurons ◽  
Neuronal Excitability ◽  
Phosphorylation Sites ◽  
Voltage Dependent ◽  
Activity Dependent ◽  
Stimulation Of ◽  
Cultured Hippocampal Neurons

Bidirectional Activity-Dependent Regulation of Neuronal Ion Channel Phosphorylation. Misonou H, Menegola M, Mohapatra DP, Guy LK, Park KS, Trimmer JS. J Neurosci 2006;26(52):13505–13514. Activity-dependent dephosphorylation of neuronal Kv2.1 channels yields hyperpolarizing shifts in their voltage-dependent activation and homoeostatic suppression of neuronal excitability. We recently identified 16 phosphorylation sites that modulate Kv2.1 function. Here, we show that in mammalian neurons, compared with other regulated sites, such as serine (S)563, phosphorylation at S603 is supersensitive to calcineurin-mediated dephosphorylation in response to kainate-induced seizures in vivo, and brief glutamate stimulation of cultured hippocampal neurons. In vitro calcineurin digestion shows that supersensitivity of S603 dephosphorylation is an inherent property of Kv2.1. Conversely, suppression of neuronal activity by anesthetic in vivo causes hyperphosphorylation at S603 but not S563. Distinct regulation of individual phosphorylation sites allows for graded and bidirectional homeostatic regulation of Kv2.1 function. S603 phosphorylation represents a sensitive bidirectional biosensor of neuronal activity.

scholarly journals Regulation of TrkB receptor tyrosine kinase and its internalization by neuronal activity and Ca2+ influx

2003 ◽  
Vol 163 (2) ◽  
pp. 385-395 ◽  
Author(s):  
Jing Du ◽  
Linyin Feng ◽  
Eugene Zaitsev ◽  
Hyun-Soo Je ◽  
Xu-wen Liu ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Neuronal Activity ◽  
Cell Biology ◽  
Hippocampal Neurons ◽  
Electric Stimulation ◽  
Kinase Activity ◽  
Critical Role ◽  
Tyrosine Kinase Activity ◽  
Internalization Process ◽  
Activity Dependent

Internalization of the neurotrophin–Trk receptor complex is critical for many aspects of neurotrophin functions. The mechanisms governing the internalization process are unknown. Here, we report that neuronal activity facilitates the internalization of the receptor for brain-derived neurotrophic factor, TrkB, by potentiating its tyrosine kinase activity. Using three independent approaches, we show that electric stimulation of hippocampal neurons markedly enhances TrkB internalization. Electric stimulation also potentiates TrkB tyrosine kinase activity. The activity-dependent enhancement of TrkB internalization and its tyrosine kinase requires Ca2+ influx through N-methyl-d-aspartate receptors and Ca2+ channels. Inhibition of internalization had no effect on TrkB kinase, but inhibition of TrkB kinase prevents the modulation of TrkB internalization, suggesting a critical role of the tyrosine kinase in the activity-dependent receptor endocytosis. These results demonstrate an activity- and Ca2+-dependent modulation of TrkB tyrosine kinase and its internalization, and they provide new insights into the cell biology of tyrosine kinase receptors.

Sign in / Sign up

Export Citation Format

Share Document