scholarly journals Astrocytic extracellular vesicles modulate neuronal calcium homeostasis via transglutaminase-2

2021 ◽  
Author(s):  
Elisa Tonoli ◽  
Ivan Verduci ◽  
Ilaria Prada ◽  
Greta Forcaia ◽  
Martina Gabrielli ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Hippocampal Neurons ◽  
Brain Slices ◽  
Transglutaminase 2 ◽  
Synaptic Activity ◽  
Brain Inflammation ◽  
Mode Switching ◽  
Neuronal Membrane ◽  
Reverse Mode ◽  
Inward Currents

We have uncovered a novel role for astrocytes-derived extracellular vesicles (EVs) in controlling intraneuronal Ca2+ concentration ([Ca2+]i) and identified transglutaminase-2 (TG2) as a surface-cargo of astrocytes-derived EVs. Incubation of hippocampal neurons with primed astrocyte-derived EVs have led to an increase in [Ca2+]i, unlike EVs from TG2-knockout astrocytes. Exposure of neurons or brain slices to extracellular TG2 promoted a [Ca2+]i rise, which was reversible upon TG2 removal and was dependent on Ca2+ influx through the plasma membrane. Patch-clamp and calcium imaging recordings revealed TG2-dependent neuronal membrane depolarisation and activation of inward currents, due to the opening of L-type-VOCCs and to Na+/Ca2+-exchanger (NCX) operation in the reverse mode, as indicated by VOCCs/NCX pharmacological inhibitors. A subunit of Na+/K+-ATPase was selected by comparative proteomics and identified as being functionally inhibited by extracellular TG2, implicating Na+/K+-ATPase inhibition in NCX reverse mode-switching leading to Ca2+ influx and higher basal [Ca2+]i. These data suggest that reactive astrocytes control intraneuronal [Ca2+]i through release of EVs with TG2 as responsible cargo, which could have a significant impact on synaptic activity in brain inflammation.

scholarly journals Glycine Site of NMDA Receptor Serves as a Spatiotemporal Detector of Synaptic Activity Patterns

2009 ◽  
Vol 102 (1) ◽  
pp. 578-589 ◽  
Author(s):  
Yan Li ◽  
Boris Krupa ◽  
Jian-Sheng Kang ◽  
Vadim Y. Bolshakov ◽  
Guosong Liu
Keyword(s):  
Nmda Receptor ◽  
Hippocampal Neurons ◽  
Developmental Plasticity ◽  
Calcium Influx ◽  
Activity Patterns ◽  
Hippocampal Slices ◽  
Brain Slices ◽  
Cell Voltage ◽  
Synaptic Activity ◽  
Glycine Site

Calcium influx associated with the opening of N-methyl-d-aspartate (NMDA) receptor channels is the major signal triggering synaptic and developmental plasticity. Controlling the NMDA receptor function is therefore critical for many functions of the brain. We explored the mechanisms of synaptic activation of the NMDAR glycine site by endogenous coagonist using whole cell voltage-clamp recordings from hippocampal neurons in mixed cultures, containing both neurons and glial cells, and, under more physiological conditions, in hippocampal slices. Here we show that the glycine site of the NMDA receptor at hippocampal synapses, both in culture and acute brain slices, is not saturated by the ambient coagonist concentration and is modulated through activity-dependent coagonist release. Augmentation of the NMDA receptor-mediated synaptic responses by local glutamate-induced coagonist release is spatially restricted and determined by spatiotemporal summation of synaptic events at neighboring synaptic inputs on a single dendritic branch. Therefore different spatiotemporal patterns of presynaptic activity could be translated into different levels of the NMDAR activation in specific afferent projections. These results suggest that the NMDA receptor glycine site may serve as a detector of the spatiotemporal characteristics of presynaptic activity patterns.

scholarly journals GPI-1046 Increases Presenilin-1 Expression and Restores NMDA Channel Activity

2010 ◽  
Vol 37 (4) ◽  
pp. 457-467 ◽  
Author(s):  
Joseph P. Steiner ◽  
Kathryn B. Payne ◽  
Christopher Drummond Main ◽  
Sabrina D'Alfonso ◽  
Kirsten X. Jacobsen ◽  
...  
Keyword(s):  
Nmda Receptor ◽  
Synaptic Transmission ◽  
Brain Slices ◽  
Synaptic Activity ◽  
Presenilin 1 ◽  
Receptor Function ◽  
Channel Function ◽  
Nmda Channel ◽  
Nmda Receptor Function ◽  
6 Hydroxydopamine

Background:Previously we showed that 6-hydroxydopamine lesions of the substantia nigra eliminate corticostriatal LTP and that the neuroimmunolophilin ligand (NIL), GPI-1046, restores LTP.Methods:We used cDNA microarrays to determine what mRNAs may be over- or under-expressed in response to lesioning and/or GPI-1046 treatment. Patch clamp recordings were performed to investigate changes in NMDA channel function before and after treatments.Results:We found that 51 gene products were differentially expressed. Among these we found that GPI-1046 treatment up-regulated presenilin-1 (PS-1) mRNA abundance. This finding was confirmed using QPCR. PS-1 protein was also shown to be over-expressed in the striatum of lesioned/GPI-1046-treated rats. As PS-1 has been implicated in controlling NMDA-receptor function and LTP is reduced by lesioning we assayed NMDA mediated synaptic activity in striatal brain slices. The lesion-induced reduction of dopaminergic innervation was accompanied by the near complete loss of NDMA receptor-mediated synaptic transmission between the cortex and striatum. GPI-1046 treatment of the lesioned rats restored NMDA-mediated synaptic transmission but not the dopaminergic innervation. Restoration of NDMA channel function was apparently specific as the sodium channel current density was also reduced due to lesioning but GPI-1046 did not reverse this effect. We also found that restoration of NMDA receptor function was also not associated with either an increase in NMDA receptor mRNA or protein expression.Conclusion:As it has been previously shown that PS-1 is critical for normal NMDA receptor function, our data suggest that the improvement of excitatory neurotransmission occurs through the GPI-1046-induced up-regulation of PS-1.

Reverse mode switching of the random laser emission in dye doped liquid crystals under homogeneous and inhomogeneous electric fields

2016 ◽  
Vol 4 (1) ◽  
pp. 7 ◽  
Author(s):  
M. Shasti ◽  
P. Coutino ◽  
S. Mukherjee ◽  
A. Varanytsia ◽  
T. Smith ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Electric Fields ◽  
Laser Emission ◽  
Mode Switching ◽  
Random Laser ◽  
Reverse Mode

scholarly journals Impaired Kv7 channel activity in the central amygdala contributes to elevated sympathetic outflow in hypertension

2021 ◽  
Author(s):  
Zhao-Fu Sheng ◽  
Hua Zhang ◽  
PeiRu Zheng ◽  
Shanyan Chen ◽  
Zezong Gu ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Brain Slices ◽  
Primary Hypertension ◽  
Neuronal Membrane ◽  
Sympathetic Outflow ◽  
Channel Activity ◽  
Central Amygdala ◽  
Expression Levels ◽  
Wky Rats ◽  
Arterial Blood

Abstract Aims Elevated sympathetic outflow is associated with primary hypertension. However, the mechanisms involved in heightened sympathetic outflow in hypertension are unclear. The central amygdala (CeA) regulates autonomic components of emotions through projections to the brainstem. The neuronal Kv7 channel is a non-inactivating voltage-dependent K+ channel encoded by KCNQ2/3 genes involved in stabilizing the neuronal membrane potential and regulating neuronal excitability. In this study, we investigated if altered Kv7 channel activity in the CeA contributes to heightened sympathetic outflow in hypertension. Methods and results The mRNA and protein expression levels of Kv7.2/Kv7.3 in the CeA were significantly reduced in spontaneously hypertensive rats (SHRs) compared with Wistar–Kyoto (WKY) rats. Lowering blood pressure with coeliac ganglionectomy in SHRs did not alter Kv7.2 and Kv7.3 channel expression levels in the CeA. Fluospheres were injected into the rostral ventrolateral medulla (RVLM) to retrogradely label CeA neurons projecting to the RVLM (CeA–RVLM neurons). Kv7 channel currents recorded from CeA–RVLM neurons in brain slices were much smaller in SHRs than in WKY rats. Furthermore, the basal firing activity of CeA–RVLM neurons was significantly greater in SHRs than in WKY rats. Bath application of specific Kv7 channel blocker 10, 10-bis (4-pyridinylmethyl)-9(10H)-anthracnose (XE-991) increased the excitability of CeA–RVLM neurons in WKY rats, but not in SHRs. Microinjection of XE-991 into the CeA increased arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), while microinjection of Kv7 channel opener QO-58 decreased ABP and RSNA, in anaesthetized WKY rats but not SHRs. Conclusions Our findings suggest that diminished Kv7 channel activity in the CeA contributes to elevated sympathetic outflow in primary hypertension. This novel information provides new mechanistic insight into the pathogenesis of neurogenic hypertension.

Fast NMDA Receptor–Mediated Synaptic Currents in Neurons From Mice Lacking the ε2 (NR2B) Subunit

2000 ◽  
Vol 83 (1) ◽  
pp. 616-620 ◽  
Author(s):  
Kenneth R. Tovar ◽  
Kathleen Sprouffske ◽  
Gary L. Westbrook
Keyword(s):  
Nmda Receptor ◽  
Hippocampal Neurons ◽  
Postsynaptic Membrane ◽  
Synaptic Activity ◽  
Wild Type ◽  
Nmda Receptor Subunit ◽  
Deactivation Kinetics ◽  
Low Concentrations ◽  
Specific Antagonist

The N-methyl-d-aspartate (NMDA) receptor has been implicated in the formation of synaptic connections. To investigate the role of the ε2 (NR2B) NMDA receptor subunit, which is prominently expressed during early development, we used neurons from mice lacking this subunit. Although ε2−/− mice die soon after birth, we examined whether NMDA receptor targeting to the postsynaptic membrane was dependent on the ε2 subunit by rescuing hippocampal neurons from these mice and studying them in autaptic cultures. In voltage-clamp recordings, excitatory postsynaptic currents (EPSCs) from ε2−/− neurons expressed an NMDA receptor–mediated EPSC that was apparent as soon as synaptic activity developed. However, compared with wild-type neurons, NMDA receptor–mediated EPSC deactivation kinetics were much faster and were less sensitive to glycine, but were blocked by Mg2+ or AP5. Whole cell currents from ε2−/− neurons were also more sensitive to block by low concentrations of Zn2+ and much less sensitive to the ε2-specific antagonist ifenprodil than wild-type currents. The rapid NMDA receptor–mediated EPSC deactivation kinetics and the pharmacological profile from ε2−/−neurons are consistent with the expression of ζ1/ε1 diheteromeric receptors in excitatory hippocampal neurons from mice lacking the ε2 subunit. Thus ε1 can substitute for the ε2 subunit at synapses and ε2 is not required for targeting of NMDA receptors to the postsynaptic membrane.

A Simple Depletion Model of the Readily Releasable Pool of Synaptic Vesicles Cannot Account for Paired-Pulse Depression

2007 ◽  
Vol 97 (1) ◽  
pp. 948-950 ◽  
Author(s):  
Jane M. Sullivan
Keyword(s):  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Synaptic Activity ◽  
Excitatory Synapses ◽  
Short Term ◽  
Paired Pulse ◽  
Short Term Plasticity ◽  
Releasable Pool ◽  
Readily Releasable Pool ◽  
Paired Pulse Depression

Paired-pulse depression (PPD) is a form of short-term plasticity that plays a central role in processing of synaptic activity and is manifest as a decrease in the size of the response to the second of two closely timed stimuli. Despite mounting evidence to the contrary, PPD is still commonly thought to reflect depletion of the pool of synaptic vesicles available for release in response to the second stimulus. Here it is shown that PPD cannot be accounted for by depletion at excitatory synapses made by hippocampal neurons because PPD is unaffected by changes in the fraction of the readily releasable pool (RRP) released by the first of a pair of pulses.

Altered desensitization produces enhancement of EPSPs in neocortical neurons

1994 ◽  
Vol 72 (2) ◽  
pp. 1032-1036 ◽  
Author(s):  
M. R. Pelletier ◽  
J. J. Hablitz
Keyword(s):  
Nmda Receptors ◽  
Time Course ◽  
Glutamate Release ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Bath Application

1. Neocortical brain slices were prepared from rats (35–50 days of age) and maintained in vitro. Intracellular recordings were obtained from neurons in cortical layers II/III. The effect of bath application of cyclothiazide (CYZ), a potent blocker of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor desensitization, on evoked synaptic activity and passive membrane properties was investigated. 2. Bath application of CYZ did not significantly affect resting membrane potential, input resistance, or repetitive firing. CYZ increased both the amplitude and duration of evoked excitatory postsynaptic potentials (EPSPs). Polysynaptic responses were also augumented. These effects persisted after the blockade of N-methyl-D-aspartate (NMDA) receptors with D-2-amino-5-phosphonovaleric acid (D-APV). The magnitude of these effects appeared to vary directly with stimulation intensity and presumably, amount of glutamate release. 3. Epileptiform activity was induced by bath application of bicuculline methiodide. The amplitude and duration of evoked paroxysmal discharges were increased by CYZ. Similar results were seen in presence of D-APV. 4. These results indicate that CYZ has significant effects on synaptic transmission. Desensitization of non-NMDA receptors may be an important mechanism for determining the time course of EPSPs and in curtailing epileptiform responses in the rat neocortex.

Changes in membrane currents of hippocampal neurons evoked by brief anoxia

1989 ◽  
Vol 62 (1) ◽  
pp. 15-30 ◽  
Author(s):  
K. Krnjevic ◽  
J. Leblond
Keyword(s):  
Hippocampal Neurons ◽  
Hippocampal Slices ◽  
Reversal Potential ◽  
Outward Current ◽  
Membrane Currents ◽  
Sprague Dawley ◽  
Persistent Currents ◽  
Inward Currents ◽  
The Difference ◽  
Conductance Increase

1. Effects of anoxia (2-4 min of 95% N2-5% CO2) on membrane currents of CA1 neurons were studied by single-electrode voltage clamp in hippocampal slices (from Sprague-Dawley rats) kept in an interface-type chamber at 33.5 degree. 2. When recording with KCl electrodes at a holding potential (VH) near-70 mV, anoxia evoked a slow outward current [0.18 +/- 0.06 (SE) nA], accompanied by a conductance increase ( + 46 +/- 20%, mean +/- SE). The difference current evoked by N2 had a reversal potential near-100 mV. It was much smaller in presence of 2-4 mM extracellular Cs, and any remaining outward current was abolished by 10 mM tetraethylammonium (TEA). Only inward currents were observed when recording with CsCl electrodes. 3. Inward relaxations evoked by large hyperpolarizing pulses from VH less than or equal to - 70 mV (Q-type) were not significantly depressed by anoxia (-1.5 +/- 6.0%). 4. Some voltage-dependent outward currents (evoked by 200-ms depolarizing pulses) were depressed during anoxia: 1) a fast-inactivating (A-like) current, obtained at VH less than or equal to -70 mV and suppressed by 200 microM 4-AP, was reduced by 25.6 +/- 7.3% (n = 5); 2) a slower, noninactivating (C-like) current, suppressed by TEA, was reduced by 52 +/- 7.2% (n = 16). Neither of these currents (1 or 2) was observed when recording with 2- to 3-M CsCl electrodes; and 3) small (M-like) inward relaxations, observed at VH approximately -40 mV 5. Net inward currents could be evoked after blockage of GK with 10 mM TEA when recording with KCl electrodes or by recording with CsCl electrodes. At VH less than or equal to -70 mV, large, transient, and incompletely controlled currents were evoked by depolarizing pulses; at VH less than or equal to -50 mV, smaller and more persistent currents were evoked by depolarizing pulses (L-like), and transient currents (T-like?) were seen immediately after hyperpolarizing pulses. 6.L-type currents (at VH less than or equal to -50 mV) were nearly abolished after 1-2 min anoxia (by approximately 90%). This was equally true of the currents evoked by constant pulses or peak currents in I-V plots. After reoxygenation, recovery was biphasic, with a quick early phase (to 50-80% in 2 min) and then a much slower one (to 60-90% by 10-15 min).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Astrocyte-Derived Small Extracellular Vesicles Regulate Dendritic Complexity through miR-26a-5p Activity

2020 ◽  
Author(s):  
Alejandro Luarte ◽  
Roberto Henzi ◽  
Anllely Fernández ◽  
Diego Gaete ◽  
Pablo Cisternas ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Hippocampal Neurons ◽  
Morphological Changes ◽  
Morphological Differentiation ◽  
Total Content ◽  
Neuronal Morphology ◽  
Cultured Astrocytes ◽  
Neuronal Proteins ◽  
Dendritic Complexity ◽  
Mirna Content

In the last decades, it has been established that astrocytes play key roles in the regulation of neuronal morphology. However, the contribution of astrocyte-derived small extracellular vesicles (sEVs) to morphological differentiation of neurons has only recently been addressed. Here, we showed that cultured astrocytes expressing a GFP tagged version of the stress-regulated astrocytic enzyme Aldolase C (Aldo C-GFP) release small extracellular vesicles (sEVs) which are transferred into cultured hippocampal neurons. Surprisingly, Aldo C-GFP-containing sEVs (Aldo C-GFP sEVs) displayed an exacerbated capacity to reduce the dendritic complexity in developing hippocampal neurons compared to sEVs derived from control (i.e. GFP-expressing) astrocytes. Using bioinformatics and biochemical tools, we found that the total content of overexpressed Aldo C-GFP correlates with an increased content of endogenous miRNA-26a-5p in both total astrocyte homogenates and sEVs. Notably, neurons magnetofected with a nucleotide sequence that mimics endogenous miRNA-26a-5p (mimic 26a-5p) not only decreased the levels of neuronal proteins associated to morphogenesis regulation and also reproduced morphological changes induced by Aldo-C-GFP sEVs. Furthermore, neurons magnetofected with a sequence targeting miRNA-26a-5p (antago 26a-5p) were largely resistant to Aldo C-GFP sEVs. Our results support a novel and complex level of astrocyte-to-neuron communication mediated by astrocyte-derived sEVs and the activity of their miRNA content.

scholarly journals Formin Activity and mDia1 Contribute to Maintain Axon Initial Segment Composition and Structure

2021 ◽  
Author(s):  
Wei Zhang ◽  
María Ciorraga ◽  
Pablo Mendez ◽  
Diana Retana ◽  
Norah Boumedine-Guignon ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Initial Segment ◽  
Protein Transport ◽  
Neuronal Excitability ◽  
Brain Slices ◽  
Axon Initial Segment ◽  
Composition And Structure ◽  
The Stability ◽  
Protein Density ◽  
Voltage Gated Ion Channels

AbstractThe axon initial segment (AIS) is essential for maintaining neuronal polarity, modulating protein transport into the axon, and action potential generation. These functions are supported by a distinctive actin and microtubule cytoskeleton that controls axonal trafficking and maintains a high density of voltage-gated ion channels linked by scaffold proteins to the AIS cytoskeleton. However, our knowledge of the mechanisms and proteins involved in AIS cytoskeleton regulation to maintain or modulate AIS structure is limited. In this context, formins play a significant role in the modulation of actin and microtubules. We show that pharmacological inhibition of formins modifies AIS actin and microtubule characteristics in cultured hippocampal neurons, reducing F-actin density and decreasing microtubule acetylation. Moreover, formin inhibition diminishes sodium channels, ankyrinG and βIV-spectrin AIS density, and AIS length, in cultured neurons and brain slices, accompanied by decreased neuronal excitability. We show that genetic downregulation of the mDia1 formin by interference RNAs also decreases AIS protein density and shortens AIS length. The ankyrinG decrease and AIS shortening observed in pharmacologically inhibited neurons and neuron-expressing mDia1 shRNAs were impaired by HDAC6 downregulation or EB1-GFP expression, known to increase microtubule acetylation or stability. However, actin stabilization only partially prevented AIS shortening without affecting AIS protein density loss. These results suggest that mDia1 maintain AIS composition and length contributing to the stability of AIS microtubules.

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