Browse
Submit Data
Databases
API
Help

Dataset Information

28 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Synaptic targeting of N-type calcium channels in hippocampal neurons.

ABSTRACT: N-type calcium (Ca2+) channels play a critical role in synaptic function, but the mechanisms responsible for their targeting in neurons are poorly understood. N-type channels are formed by an alpha(1B) (Ca(V)2.2) pore-forming subunit associated with beta and alpha2delta auxiliary subunits. By expressing epitope-tagged recombinant alpha1B subunits in rat hippocampal neuronal cultures, we demonstrate here that synaptic targeting of N-type channels depends on neuronal contacts and synapse formation. We also establish that the C-terminal 163 aa (2177-2339) of the alpha1B-1 (Ca(V)2.2a) splice variant contain sequences that are both necessary and sufficient for synaptic targeting. By site-directed mutagenesis, we demonstrate that postsynaptic density-95/discs large/zona occludens-1 and Src homology 3 domain-binding motifs located within this region of the alpha1B subunit (Maximov et al., 1999) act as synergistic synaptic targeting signals. We also show that the recombinant modular adaptor proteins Mint1 and CASK colocalize with N-type channels in synapses. We found that the alpha1B-2 (Ca(V)2.2b) splice variant is restricted to soma and dendrites and postulated that somatodendritic and axonal/presynaptic isoforms of N-type channels are generated via alternative splicing of alpha1B C termini. These data lead us to propose that during synaptogenesis, the alpha1B-1 (Ca(V)2.2a) splice variant of the N-type Ca2+ channel pore-forming subunit is recruited to presynaptic locations by means of interactions with modular adaptor proteins Mint1 and CASK. Our results provide a novel insight into the molecular mechanisms responsible for targeting of Ca2+ channels and other synaptic proteins in neurons.

SUBMITTER: Maximov A

PROVIDER: S-EPMC3307533 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Calcium-activated chloride channels (CaCCs) regulate action potential and synaptic response in hippocampal neurons.

Project description:Central neurons respond to synaptic inputs from other neurons by generating synaptic potentials. Once the summated synaptic potentials reach threshold for action potential firing, the signal propagates leading to transmitter release at the synapse. The calcium influx accompanying such signaling opens calcium-activated ion channels for feedback regulation. Here, we report a mechanism for modulating hippocampal neuronal signaling that involves calcium-activated chloride channels (CaCCs). We present evidence that CaCCs reside in hippocampal neurons and are in close proximity of calcium channels and NMDA receptors to shorten action potential duration, dampen excitatory synaptic potentials, impede temporal summation, and raise the threshold for action potential generation by synaptic potential. Having recently identified TMEM16A and TMEM16B as CaCCs, we further show that TMEM16B but not TMEM16A is important for hippocampal CaCC, laying the groundwork for deciphering the dynamic CaCC modulation of neuronal signaling in neurons important for learning and memory.

| S-EPMC3329964 | biostudies-literature

Roles of somatic A-type K(+) channels in the synaptic plasticity of hippocampal neurons.

Project description:In the mammalian brain, information encoding and storage have been explained by revealing the cellular and molecular mechanisms of synaptic plasticity at various levels in the central nervous system, including the hippocampus and the cerebral cortices. The modulatory mechanisms of synaptic excitability that are correlated with neuronal tasks are fundamental factors for synaptic plasticity, and they are dependent on intracellular Ca(2+)-mediated signaling. In the present review, the A-type K(+) (IA) channel, one of the voltage-dependent cation channels, is considered as a key player in the modulation of Ca(2+) influx through synaptic NMDA receptors and their correlated signaling pathways. The cellular functions of IA channels indicate that they possibly play as integral parts of synaptic and somatic complexes, completing the initiation and stabilization of memory.

| S-EPMC5562601 | biostudies-other

Surface traffic of dendritic CaV1.2 calcium channels in hippocampal neurons.

Project description:In neurons L-type calcium currents function in gene regulation and synaptic plasticity, while excessive calcium influx leads to excitotoxicity and neurodegeneration. The major neuronal Ca(V)1.2 L-type channels are localized in clusters in dendritic shafts and spines. Whereas Ca(V)1.2 clusters remain stable during NMDA-induced synaptic depression, L-type calcium currents are rapidly downregulated during strong excitatory stimulation. Here we used fluorescence recovery after photobleaching (FRAP), live cell-labeling protocols, and single particle tracking (SPT) to analyze the turnover and surface traffic of Ca(V)1.2 in dendrites of mature cultured mouse and rat hippocampal neurons, respectively. FRAP analysis of channels extracellularly tagged with superecliptic pHluorin (Ca(V)1.2-SEP) demonstrated ∼20% recovery within 2 min without reappearance of clusters. Pulse-chase labeling showed that membrane-expressed Ca(V)1.2-HA is not internalized within1 h, while blocking dynamin-dependent endocytosis resulted in increased cluster density after 30 min. Together, these results suggest a turnover rate of clustered Ca(V)1.2s on the hour time scale. Direct recording of the lateral movement in the membrane using SPT demonstrated that dendritic Ca(V)1.2s show highly confined mobility with diffusion coefficients of ∼0.005 μm² s⁻¹. Consistent with the mobile Ca(V)1.2 fraction observed in FRAP, a ∼30% subpopulation of channels reversibly exchanged between confined and diffusive states. Remarkably, high potassium depolarization did not alter the recovery rates in FRAP or the diffusion coefficients in SPT analyses. Thus, an equilibrium of clustered and dynamic Ca(V)1.2s maintains stable calcium channel complexes involved in activity-dependent cell signaling, whereas the minor mobile channel pool in mature neurons allows limited capacity for short-term adaptations.

| S-EPMC3325119 | biostudies-literature

Formaldehyde increases intracellular calcium concentration in primary cultured hippocampal neurons partly through NMDA receptors and T-type calcium channels.

Project description:Formaldehyde at high concentrations is a contributor to air pollution. It is also an endogenous metabolic product in cells, and when beyond physiological concentrations, has pathological effects on neurons. Formaldehyde induces mis-folding and aggregation of neuronal tau protein, hippocampal neuronal apoptosis, cognitive impairment and loss of memory functions, as well as excitation of peripheral nociceptive neurons in cancer pain models. Intracellular calcium ([Ca(2+)](i)) is an important intracellular messenger, and plays a key role in many pathological processes. The present study aimed to investigate the effect of formaldehyde on [Ca(2+)](i) and the possible involvement of N-methyl-D-aspartate receptors (NMDARs) and T-type Ca(2+) channels on the cell membrane.Using primary cultured hippocampal neurons as a model, changes of [Ca(2+)](i) in the presence of formaldehyde at a low concentration were detected by confocal laser scanning microscopy.Formaldehyde at 1 mmol/L approximately doubled [Ca(2+)](i). (2R)-amino-5-phosphonopentanoate (AP5, 25 μmol/L, an NMDAR antagonist) and mibefradil (MIB, 1 μmol/L, a T-type Ca(2+) channel blocker), given 5 min after formaldehyde perfusion, each partly inhibited the formaldehyde-induced increase of [Ca(2+)](i), and this inhibitory effect was reinforced by combined application of AP5 and MIB. When applied 3 min before formaldehyde perfusion, AP5 (even at 50 μmol/L) did not inhibit the formaldehyde-induced increase of [Ca(2+)](i), but MIB (1 μmol/L) significantly inhibited this increase by 70%.These results suggest that formaldehyde at a low concentration increases [Ca(2+)](i) in cultured hippocampal neurons; NMDARs and T-type Ca(2+) channels may be involved in this process.

| S-EPMC5561821 | biostudies-other

The Downregulation of Somatic A-Type K(+) Channels Requires the Activation of Synaptic NMDA Receptors in Young Hippocampal Neurons of Rats.

Project description:The downregulation of A-type K(+) channels (IA channels) accompanying enhanced somatic excitability can mediate epileptogenic conditions in mammalian central nervous system. As IA channels are dominantly targeted by dendritic and postsynaptic processings during synaptic plasticity, it is presumable that they may act as cellular linkers between synaptic responses and somatic processings under various excitable conditions. In the present study, we electrophysiologically tested if the downregulation of somatic IA channels was sensitive to synaptic activities in young hippocampal neurons. In primarily cultured hippocampal neurons (DIV 6~9), the peak of IA recorded by a whole-cell patch was significantly reduced by high KCl or exogenous glutamate treatment to enhance synaptic activities. However, the pretreatment of MK801 to block synaptic NMDA receptors abolished the glutamate-induced reduction of the IA peak, indicating the necessity of synaptic activation for the reduction of somatic IA. This was again confirmed by glycine treatment, showing a significant reduction of the somatic IA peak. Additionally, the gating property of IA channels was also sensitive to the activation of synaptic NMDA receptors, showing the hyperpolarizing shift in inactivation kinetics. These results suggest that synaptic LTP possibly potentiates somatic excitability via downregulating IA channels in expression and gating kinetics. The consequential changes of somatic excitability following the activity-dependent modulation of synaptic responses may be a series of processings for neuronal functions to determine outputs in memory mechanisms or pathogenic conditions.

| S-EPMC3994300 | biostudies-literature

Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels in cultured rat hippocampal neurons.

Project description:To investigate the effect of ginsenoside Rb1 on voltage-gated calcium currents in cultured rat hippocampal neurons and the modulatory mechanism.Cultured hippocampal neurons were prepared from Sprague Dawley rat embryos. Whole-cell configuration of the patch-clamp technique was used to record the voltage-gated calcium currents (VGCCs) from the hippocampal neurons,and the effect of Rb1 was examined.Rb1 (2-100 μmol/L) inhibited VGCCs in a concentration-dependent manner, and the current was mostly recovered upon wash-out. The specific L-type Ca(2+) channel inhibitor nifedipine (10 μmol/L) occluded Rb1-induced inhibition on VGCCs. Neither the selective N-type Ca(2+) channel blocker ω-conotoxin-GVIA (1 μmol/L), nor the selective P/Q-type Ca(2+) channel blocker ω-agatoxin IVA (30 nmol/L) diminished Rb1-sensitive VGCCs. Rb1 induced a leftward shift of the steady-state inactivation curve of I(Ca) to a negative potential without affecting its activation kinetics or reversal potential in the I-V curve. The inhibitory effect of Rb1 was neither abolished by the adenylyl cyclase activator forskolin (10 μmol/L), nor by the PKA inhibitor H-89 (10 μmol/L).Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels, without affecting the N-type or P/Q-type Ca(2+) channels in hippocampal neurons. cAMP-PKA signaling pathway is not involved in this effect.

| S-EPMC4003359 | biostudies-other

Behavior-Dependent Activity and Synaptic Organization of Septo-hippocampal GABAergic Neurons Selectively Targeting the Hippocampal CA3 Area.

Project description:Rhythmic medial septal (MS) GABAergic input coordinates cortical theta oscillations. However, the rules of innervation of cortical cells and regions by diverse septal neurons are unknown. We report a specialized population of septal GABAergic neurons, the Teevra cells, selectively innervating the hippocampal CA3 area bypassing CA1, CA2, and the dentate gyrus. Parvalbumin-immunopositive Teevra cells show the highest rhythmicity among MS neurons and fire with short burst duration (median, 38 ms) preferentially at the trough of both CA1 theta and slow irregular oscillations, coincident with highest hippocampal excitability. Teevra cells synaptically target GABAergic axo-axonic and some CCK interneurons in restricted septo-temporal CA3 segments. The rhythmicity of their firing decreases from septal to temporal termination of individual axons. We hypothesize that Teevra neurons coordinate oscillatory activity across the septo-temporal axis, phasing the firing of specific CA3 interneurons, thereby contributing to the selection of pyramidal cell assemblies at the theta trough via disinhibition. VIDEO ABSTRACT.

| S-EPMC5746169 | biostudies-literature

Pentobarbitone modulates calcium transients in axons and synaptic boutons of hippocampal CA1 neurons.

Project description:Although barbiturates, like other general anaesthetics, depress excitatory synaptic transmission in the central nervous system (CNS), the underlying cellular mechanisms remain unresolved. They may increase the likelihood that an action potential will fail to invade every branch of the axonal arbour, thereby decreasing the synaptic drive to the postsynaptic neurons. Alternatively, they may inhibit calcium entry into the presynaptic terminals, thus reducing transmitter release. To resolve these issues, we have used two-photon microscopy to monitor calcium transients evoked by action potentials in axons, axonal varicosities (synaptic boutons) and fine axon collaterals of hippocampal CA1 neurons. Pentobarbitone (75-300 microM) did not block the invasion of the axonal arbour or the synaptic boutons, but it did reduce the amplitude of the calcium transients recorded from the axons in a concentration-dependent manner. At 150 microM, pentobarbitone reduced the transients to 78+/-4% of the control. Pentobarbitone depressed the calcium transients recorded from the synaptic boutons in a concentration-dependent manner. When 150 microM pentobarbitone was applied, the calcium transients recorded from the boutons were 53+/-3% of the control. This concentration of pentobarbitone also reduced the amplitude and frequency of the spontaneous excitatory postsynaptic potentials to 54+/-4 and 42+/-17% of the control, respectively. The local anaesthetic procaine (500 microM) had no significant effect on action potential invasion of axon collaterals, even though it reduced the action potential amplitude by 25%. This data are consistent with the notion that the pentobarbitone-induced depression of presynaptic calcium transients contributes to its depressant effect on excitatory synaptic transmission in the CNS.

| S-EPMC1574109 | biostudies-other

T-type calcium channels mediate rebound firing in intact deep cerebellar neurons.

Project description:Neurons of the deep cerebellar nuclei (DCN) form the main output of the cerebellar circuitry and thus play an important role in cerebellar motor coordination. A prominent biophysical property observed in rat DCN neurons is rebound firing; a brief but strong hyperpolarizing input transiently increases their firing rate to much higher levels compared with that prior to the inhibitory input. Low-threshold T-type voltage-gated calcium channels have been suspected for a long time to be responsible for this phenomenon, but direct pharmacological evidence in support of this proposition is lacking. Even though a multitude of functional roles has been assigned to rebound firing in DCN neurons, their prevalence under physiological conditions is in question. Studies aimed at delineating the physiological role of rebound firing are hampered by the lack of a good pharmacological blocker. Here we show that mibefradil, a compound that blocks T-type calcium channels, potently blocks rebound firing in DCN neurons. In whole-cell experiments both mibefradil and NNC 55-0396 [(1S,2S)-2-(2-(N-[(3-benzimidazol-2-yl)propyl]-N-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl cyclopropanecarboxylate dihydrochloride]. a more selective T-type calcium channel blocker, effectively blocked rebound firing produced by direct current injection. Thus, mibefradil and other T-type channel modulators may prove to be invaluable tools for elucidating the functional importance of DCN rebound firing in cerebellar computation.

| S-EPMC2649676 | biostudies-literature

The role of MAP1A light chain 2 in synaptic surface retention of Cav2.2 channels in hippocampal neurons.

Project description:Ca(v)2.2 channels are localized at nerve terminals where they play a critical role in neurotransmission. However, the determinant that controls surface retention of these channels has not been identified. Here, we report that presynaptic surface localization of Ca(v)2.2 is mediated through its interaction with light chain 2 (LC2) of microtubule-associated protein MAP1A. Deletion of a 23-residue binding domain within the Ca(v)2.2 C terminus resulted in reduced synaptic distribution of the mutant channels. Using an antibody generated against an extracellular epitope of Ca(v)2.2, we demonstrate that interfering the interaction with LC2 reduced surface expression of endogenous Ca(v)2.2 at presynaptic boutons. In addition, the disruption of LC2-Ca(v)2.2 coupling reduced Ca(2+)-influx into nerve terminals through Ca(v)2.2 and impaired activity-dependent FM4-64 uptake. The treatments of neurons with Latrunculin A to disrupt actin filaments resulted in reduced density of surface Ca(v)2.2-positive boutons. Furthermore, LC2NT, a LC2 truncated mutant lacking the actin-binding domain, could not rescue Ca(v)2.2 surface expression after suppressing LC2 expression with RNAi. Because actin filaments are major cytomatric components at the presynaptic boutons, these observations suggest a mechanism by which LC2 provides anchoring of surface Ca(v)2.2 to the actin cytoskeleton, thus contributing to presynaptic function.

| S-EPMC2596948 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data