scholarly journals Activity-dependent expression of reporter proteins at dendritic spines for synaptic activity mapping and optogenetic stimulation

2016 ◽  
Author(s):  
Francesco Gobbo ◽  
Laura Marchetti ◽  
Claudia Alia ◽  
Stefano Luin ◽  
Antonino Cattaneo
Keyword(s):  
Dendritic Spines ◽  
Cognitive Disorders ◽  
Synaptic Activity ◽  
Regulatory Sequences ◽  
Synaptic Connections ◽  
Optogenetic Stimulation ◽  
Reporter Proteins ◽  
Activity Dependent ◽  
The Brain ◽  
Spine Number

Increasing evidence points to the importance of dendritic spines in the formation and allocation of memories, and alterations of spine number and physiology are associated to memory and cognitive disorders. Synaptic connections and pathways constitute the physical substrate that conveys information in the brain, and different combinations of active synaptic connections are believed to be responsible for the encoding of specific memories. In addition, modifications of the activity of such subsets of synapses are believed to be crucial for memory establishment, but a way to directly test this hypothesis, by selectively controlling the activity of potentiated spines, is currently lagging behind. Therefore it would be important to develop methods to tag active synapses for mapping functionally active connections and to selectively stimulate or interfere with active synapses. Here we introduce an approach to express light-sensitive membrane channels at synapses in an activity-dependent way by means of RNA and protein regulatory sequences. This approach is based on the local expression of reporter proteins, including optogenetic probes, at activated synapses and will allow the mapping of previously active synapses and the re-activation of the neuron only at these sites. This will allow extending the investigation of memory processes beyond the current neuron tagging technologies, whose resolution is limited at the cellular scale. Thus, it will be possible to unveil and recall the synaptic engram out of the global set of synapses.

scholarly journals Actin in dendritic spines: connecting dynamics to function

2010 ◽  
Vol 189 (4) ◽  
pp. 619-629 ◽  
Author(s):  
Pirta Hotulainen ◽  
Casper C. Hoogenraad
Keyword(s):  
Dendritic Spines ◽  
Synaptic Activity ◽  
Actin Dynamics ◽  
Excitatory Synapses ◽  
Synaptic Connections ◽  
Neuronal Dendrites ◽  
Brain Changes ◽  
Processing And Storage ◽  
And Storage ◽  
The Brain

Dendritic spines are small actin-rich protrusions from neuronal dendrites that form the postsynaptic part of most excitatory synapses and are major sites of information processing and storage in the brain. Changes in the shape and size of dendritic spines are correlated with the strength of excitatory synaptic connections and heavily depend on remodeling of its underlying actin cytoskeleton. Emerging evidence suggests that most signaling pathways linking synaptic activity to spine morphology influence local actin dynamics. Therefore, specific mechanisms of actin regulation are integral to the formation, maturation, and plasticity of dendritic spines and to learning and memory.

scholarly journals Activity-dependent, homeostatic regulation of neurotransmitter release from auditory nerve fibers

2015 ◽  
Vol 112 (20) ◽  
pp. 6479-6484 ◽  
Author(s):  
Tenzin Ngodup ◽  
Jack A. Goetz ◽  
Brian C. McGuire ◽  
Wei Sun ◽  
Amanda M. Lauer ◽  
...  
Keyword(s):  
Auditory Nerve ◽  
Neurotransmitter Release ◽  
High Reliability ◽  
Downstream Processing ◽  
Nerve Fibers ◽  
Synaptic Activity ◽  
Quantal Size ◽  
Activity Dependent ◽  
The Brain ◽  
Homeostatic Response

Information processing in the brain requires reliable synaptic transmission. High reliability at specialized auditory nerve synapses in the cochlear nucleus results from many release sites (N), high probability of neurotransmitter release (Pr), and large quantal size (Q). However, high Pr also causes auditory nerve synapses to depress strongly when activated at normal rates for a prolonged period, which reduces fidelity. We studied how synapses are influenced by prolonged activity by exposing mice to constant, nondamaging noise and found that auditory nerve synapses changed to facilitating, reflecting low Pr. For mice returned to quiet, synapses recovered to normal depression, suggesting that these changes are a homeostatic response to activity. Two additional properties, Q and average excitatory postsynaptic current (EPSC) amplitude, were unaffected by noise rearing, suggesting that the number of release sites (N) must increase to compensate for decreased Pr. These changes in N and Pr were confirmed physiologically using the integration method. Furthermore, consistent with increased N, endbulbs in noise-reared animals had larger VGlut1-positive puncta, larger profiles in electron micrographs, and more release sites per profile. In current-clamp recordings, noise-reared BCs had greater spike fidelity even during high rates of synaptic activity. Thus, auditory nerve synapses regulate excitability through an activity-dependent, homeostatic mechanism, which could have major effects on all downstream processing. Our results also suggest that noise-exposed bushy cells would remain hyperexcitable for a period after returning to normal quiet conditions, which could have perceptual consequences.

scholarly journals Targeting of NF-κB to Dendritic Spines is Required for Synaptic Signaling and Spine Development

2018 ◽  
Author(s):  
Erica C. Dresselhaus ◽  
Matthew C.H. Boersma ◽  
Mollie K. Meffert
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Dendritic Spines ◽  
Brain Plasticity ◽  
Spatial Localization ◽  
Synaptic Activity ◽  
Wild Type ◽  
Spine Development ◽  
Response Expression ◽  
Activity Dependent

ABSTRACTLong-term forms of brain plasticity share a requirement for changes in gene expression induced by neuronal activity. Mechanisms that determine how the distinct and overlapping functions of multiple activity-responsive transcription factors, including nuclear factor kappa B (NF-κB), give rise to stimulus-appropriate neuronal responses remain unclear. We report that the p65/RelA subunit of NF-κB confers subcellular enrichment at neuronal dendritic spines and engineer a p65 mutant that lacks spine-enrichment (ΔSEp65) but retains inherent transcriptional activity equivalent to wild-type p65. Wild-type p65 or ΔSEp65 both rescue NF-κB-dependent gene expression in p65-deficient murine hippocampal neurons responding to diffuse (PMA/ionomycin) stimulation. In contrast, neurons lacking spine-enriched NF-κB are selectively impaired in NF-κB-dependent gene expression induced by elevated excitatory synaptic stimulation (bicuculline or glycine). We used the setting of excitatory synaptic activity during development that produces NF-κB-dependent growth of dendritic spines to test physiological function of spine-enriched NF-κB in an activity-dependent response. Expression of wild-type p65, but not ΔSEp65, is capable of rescuing spine density to normal levels in p65-deficient pyramidal neurons. Collectively, these data reveal that spatial localization in dendritic spines contributes unique capacities to the NF-κB transcription factor in synaptic activity-dependent responses.SIGNIFICANCE STATEMENTExtensive research has established a model in which the regulation of neuronal gene expression enables enduring forms of plasticity and learning. However, mechanisms imparting stimulus-specificity to gene regulation, insuring biologically appropriate responses, remain incompletely understood. NF-κB is a potent transcription factor with evolutionarily-conserved functions in learning and the growth of excitatory synaptic contacts. Neuronal NF-κB is localized in both synapse and somatic compartments, but whether the synaptic pool of NF-κB has discrete functions is unknown. This study reveals that NF-κB enriched in dendritic spines (the postsynaptic sites of excitatory contacts) is selectively required for NF-κB activation by synaptic stimulation and normal dendritic spine development. These results support spatial localization at synapses as a key variable mediating selective stimulus-response coupling.

scholarly journals SULTA4A1 modulates synaptic development and function by promoting the formation of PSD-95/NMDAR complex

2019 ◽  
Author(s):  
Lorenza Culotta ◽  
Benedetta Terragni ◽  
Ersilia Vinci ◽  
Alessandro Sessa ◽  
Vania Broccoli ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Biological Function ◽  
Dendritic Morphology ◽  
Synaptic Activity ◽  
Spine Density ◽  
Neuron Development ◽  
Dendritic Spine Density ◽  
And Function ◽  
The Brain

AbstractSulfotransferase 4A1 (SULT4A1) is a cytosolic sulfotransferase, that is highly conserved across species and extensively expressed in the brain. However, the biological function of SULT4A1 is unclear. SULT4A1 has been implicated in several neuropsychiatric disorders, such as Phelan-McDermid Syndrome and schizophrenia. Here, we investigate the role of SULT4A1 within neuron development and function. Our data demonstrate that SULT4A1 modulates neuronal branching complexity and dendritic spines formation. Moreover, we show that SULT4A1, by negatively regulating the catalytic activity of Pin1 towards PSD-95, facilitates NMDAR synaptic expression and function. Finally, we demonstrate that the pharmacological inhibition of Pin1 reverses the pathological phenotypes of SULT4A1 knockdown neurons by specifically restoring dendritic spine density and rescuing NMDAR-mediated synaptic transmission. Together, these findings identify SULT4A1 as a novel player in neuron development and function by modulating dendritic morphology and synaptic activity.

scholarly journals Activity-dependent trafficking of lysosomes in dendrites and dendritic spines

2017 ◽  
Vol 216 (8) ◽  
pp. 2499-2513 ◽  
Author(s):  
Marisa S. Goo ◽  
Laura Sancho ◽  
Natalia Slepak ◽  
Daniela Boassa ◽  
Thomas J. Deerinck ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Synaptic Activity ◽  
Synaptic Membrane ◽  
Dependent Manner ◽  
Two Photon ◽  
Acid Type ◽  
Cytoskeletal Dynamics ◽  
And Function ◽  
Actin Cytoskeletal Dynamics ◽  
Activity Dependent

In neurons, lysosomes, which degrade membrane and cytoplasmic components, are thought to primarily reside in somatic and axonal compartments, but there is little understanding of their distribution and function in dendrites. Here, we used conventional and two-photon imaging and electron microscopy to show that lysosomes traffic bidirectionally in dendrites and are present in dendritic spines. We find that lysosome inhibition alters their mobility and also decreases dendritic spine number. Furthermore, perturbing microtubule and actin cytoskeletal dynamics has an inverse relationship on the distribution and motility of lysosomes in dendrites. We also find trafficking of lysosomes is correlated with synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid–type glutamate receptors. Strikingly, lysosomes traffic to dendritic spines in an activity-dependent manner and can be recruited to individual spines in response to local activation. These data indicate the position of lysosomes is regulated by synaptic activity and thus plays an instructive role in the turnover of synaptic membrane proteins.

scholarly journals Regulation of dendritic spine growth through activity-dependent recruitment of the brain-enriched Na+/H+ exchanger NHE5

2011 ◽  
Vol 22 (13) ◽  
pp. 2246-2257 ◽  
Author(s):  
Graham H. Diering ◽  
Fergil Mills ◽  
Shernaz X. Bamji ◽  
Masayuki Numata
Keyword(s):  
Nmda Receptor ◽  
Dendritic Spines ◽  
Dendritic Spine ◽  
Molecular Mechanisms ◽  
Fluorescent Protein ◽  
Receptor Activation ◽  
Neuronal Activation ◽  
Activity Dependent ◽  
The Brain ◽  
Nmda Receptor Activation

Subtle changes in cellular and extracellular pH within the physiological range have profound impacts on synaptic activities. However, the molecular mechanisms underlying local pH regulation at synapses and their influence on synaptic structures have not been elucidated. Dendritic spines undergo dynamic structural changes in response to neuronal activation, which contributes to induction and long-term maintenance of synaptic plasticity. Although previous studies have indicated the importance of cytoskeletal rearrangement, vesicular trafficking, cell signaling, and adhesion in this process, much less is known about the involvement of ion transporters. In this study we demonstrate that N-methyl-d-aspartate (NMDA) receptor activation causes recruitment of the brain-enriched Na+/H+ exchanger NHE5 from endosomes to the plasma membrane. Concomitantly, real-time imaging of green fluorescent protein–tagged NHE5 revealed that NMDA receptor activation triggers redistribution of NHE5 to the spine head. We further show that neuronal activation causes alkalinization of dendritic spines following the initial acidification, and suppression of NHE5 significantly retards the activity-induced alkalinization. Perturbation of NHE5 function induces spontaneous spine growth, which is reversed by inhibition of NMDA receptors. In contrast, overexpression of NHE5 inhibits spine growth in response to neuronal activity. We propose that NHE5 constrains activity-dependent dendritic spine growth via a novel, pH-based negative-feedback mechanism.

scholarly journals Abl2:cortactin interactions regulate dendritic spine stability via control of a stable filamentous actin pool

2020 ◽  
Author(s):  
Juliana E. Shaw ◽  
Michaela B. C. Kilander ◽  
Yu-Chih Lin ◽  
Anthony J. Koleske
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Actin Filaments ◽  
Synaptic Activity ◽  
Spine Density ◽  
Filamentous Actin ◽  
Nonreceptor Tyrosine Kinase ◽  
Spine Stability ◽  
Small Pool ◽  
Activity Dependent

AbstractDendritic spines are enriched with stable and dynamic actin filaments, which determine their structure and shape. Disruption of the Abl2/Arg nonreceptor tyrosine kinase in mice compromises spine stability and size. We provide evidence that binding to cortactin tethers Abl2 in spines, where Abl2 and cortactin maintain the small pool of stable actin required for dendritic spine stability. Using fluorescence recovery after photobleaching of GFP-actin, we find that disruption of Abl2:cortactin interactions eliminates stable actin filaments in dendritic spines, significantly reducing spine density. A subset of spines remaining after Abl2 depletion retain their stable actin pool and undergo activity-dependent spine enlargement associated with increased cortactin levels. Finally, tonic increases in synaptic activity rescue spine loss upon Abl2 depletion by promoting cortactin enrichment in vulnerable spines. Together, our findings strongly suggest Abl2:cortactin interactions promote spine stability by maintaining pools of stable actin filaments in spines.

scholarly journals ADAR2 mediated Q/R editing of GluK2 regulates homeostatic plasticity of kainate receptors

2018 ◽  
Author(s):  
Sonam Gurung ◽  
Ashley J. Evans ◽  
Kevin A. Wilkinson ◽  
Jeremy M. Henley
Keyword(s):  
Neuronal Excitability ◽  
Surface Expression ◽  
Synaptic Activity ◽  
Homeostatic Plasticity ◽  
Kainate Receptors ◽  
Mrna Editing ◽  
Network Function ◽  
Pore Lining ◽  
Activity Dependent ◽  
The Brain

AbstractKainate receptors (KARs) are heteromeric glutamate-gated ion channels that regulate neuronal excitability and network function in the brain. Most KARs contain the subunit GluK2 and the precise properties of these GluK2-containing KARs are determined by additional factors including ADAR2-mediated mRNA editing of a single codon that changes a genomically encoded glutamine (Q) to arginine (R) in the pore-lining region of GluK2. ADAR2-dependent Q/R editing of GluK2 is dynamically regulated during homeostatic plasticity (scaling) elicited by suppression of synaptic activity with TTX. Here we show that TTX decreases levels of ADAR2 by enhancing its proteasomal degradation. This selectively reduces the numbers of GluK2 subunits that are edited and increases the surface expression of GluK2-containing KARs. Furthermore, we show that partial ADAR2 knockdown phenocopies and occludes TTX-induced scaling of KARs. These data indicate that activity-dependent regulation of ADAR2 proteostasis and GluK2 Q/R editing provides a mechanism for KAR homeostatic plasticity.

scholarly journals miR-501-3p mediates the activity-dependent regulation of the expression of AMPA receptor subunit GluA1

2015 ◽  
Vol 208 (7) ◽  
pp. 949-959 ◽  
Author(s):  
Zhonghua Hu ◽  
Jun Zhao ◽  
Tianyi Hu ◽  
Yan Luo ◽  
Jun Zhu ◽  
...  
Keyword(s):  
Ampa Receptor ◽  
Dendritic Spines ◽  
Untranslated Region ◽  
Synaptic Activity ◽  
Receptor Subunit ◽  
Local Regulation ◽  
Physiological Conditions ◽  
Ampa Receptor Subunit ◽  
Nmdar Subunit ◽  
Activity Dependent

The number of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) in synapses determines synaptic strength. AMPAR expression can be regulated locally in dendrites by synaptic activity. The mechanisms of activity-dependent local regulation of AMPAR expression, however, remain unclear. Here, we tested whether microRNAs (miRNAs) are involved in N-methyl-d-aspartate (NMDA) receptor (NMDAR)–dependent AMPAR expression. We used the 3′ untranslated region of Gria1, which encodes the AMPA receptor subunit GluA1, to pull down miRNAs binding to it and analyzed these miRNAs using next-generation deep sequencing. Among the identified miRNAs, miR-501-3p is also a computationally predicted Gria1-targeting miRNA. We confirmed that miR-501-3p targets Gria1 and regulates its expression under physiological conditions. The expression of miR-501-3p and GluA1, moreover, is inversely correlated during postnatal brain development. miR-501-3p expression is up-regulated locally in dendrites through the NMDAR subunit GluN2A, and this regulation is required for NMDA-induced suppression of GluA1 expression and long-lasting remodeling of dendritic spines. These findings elucidate a miRNA-mediated mechanism for activity-dependent, local regulation of AMPAR expression in dendrites.

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