PRRT2 modulates presynaptic Ca2+ influx by interacting with P/Q-type channels.
Ontology highlight
ABSTRACT:
SUBMITTER: Ferrante D
PROVIDER: S-EPMC8220258 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:To achieve ultrafast neurotransmission, neurons assemble synapses with highly organized presynaptic and postsynaptic nanomachines that are aligned by synaptic adhesion molecules. How functional assembly of presynaptic active zones is controlled via trans-synaptic interactions remains unknown. Here, we conditionally deleted all three neurexin adhesion molecules from presynaptic neurons of the calyx of Held in the mouse auditory system, a model synapse that allows precise biophysical analyses of synaptic properties. The pan-neurexin deletion had no effect on synapse development or the basic release machinery, but dramatically impaired fast neurotransmitter release. The overall properties of presynaptic calcium ion channels appeared normal, as reflected by the similar characteristics of calcium currents recorded at the nerve terminals. However, the pan-neurexin deletion significantly impaired the tight coupling of calcium influx to exocytosis, thereby suppressing neurotransmitter release. Furthermore, the pan-neurexin deletion reduced the function of calcium-activated BK potassium channels, whose activation depends on their tight association with presynaptic calcium channels. Together, these results suggest that neurexins perform a major function at the calyx synapse in coupling presynaptic calcium channels to release sites.
| S-EPMC7110102 | biostudies-literature
Project description:Presynaptic CaV2 channels are essential for Ca2+-triggered exocytosis. In addition, there are two competing models for their roles in synapse structure. First, Ca2+ channels or Ca2+ entry may control synapse assembly. Second, active zone proteins may scaffold CaV2s to presynaptic release sites, and synapse structure is CaV2 independent. Here, we ablated all three CaV2s using conditional knockout in cultured hippocampal neurons or at the calyx of Held, which abolished evoked exocytosis. Compellingly, synapse and active zone structure, vesicle docking, and transsynaptic nano-organization were unimpaired. Similarly, long-term blockade of action potentials and Ca2+ entry did not disrupt active zone assembly. Although CaV2 knockout impaired the localization of β subunits, α2δ-1 localized normally. Rescue with CaV2 restored exocytosis, and CaV2 active zone targeting depended on the intracellular C-terminus. We conclude that synapse assembly is independent of CaV2s or Ca2+ entry through them. Instead, active zone proteins recruit and anchor CaV2s via CaV2 C-termini.
| S-EPMC7442750 | biostudies-literature
Project description:Calcium flux through L-type voltage-activated calcium (Cav1) channels is crucial for regulating brain functions including memory formation and behavior. Alterations in Ca²+ homeostasis have been linked to many cognitive disorders, and understanding the regulation of this process is crucial for their remedy. Therefore, here, we have evaluated the effect of a multifunctional protein known to be involved in memory functions called regulator of G-protein signaling 14 (RGS-14) on Cav1 channel activity in neuronal cell lines NG108-15 and SH-SY5Y. RGS-14 protein produced significant reduction in Ca²+ influx in both cell lines and this effect was dependent on nifedipine-sensitive Cav1 channels. Thus, our results provide evidence supporting the idea that RGS-14 may facilitate the cognitive processing by modulating Cav1 channel-mediated intracellular Ca²+ transients.
| S-EPMC3181207 | biostudies-literature
Project description:Common cardiovascular diseases such as hypertension and myocardial infarction require that myocytes develop greater than normal force to maintain cardiac pump function. This requires increases in [Ca(2+)]. These diseases induce cardiac hypertrophy and increases in [Ca(2+)] are known to be an essential proximal signal for activation of hypertrophic genes. However, the source of "hypertrophic" [Ca(2+)] is not known and is the topic of this study. The role of Ca(2+) influx through L-type Ca(2+) channels (LTCC), T-type Ca(2+) channels (TTCC) and transient receptor potential (TRP) channels on the activation of calcineurin (Cn)-nuclear factor of activated T cells (NFAT) signaling and myocyte hypertrophy was studied. Neonatal rat ventricular myocytes (NRVMs) and adult feline ventricular myocytes (AFVMs) were infected with an adenovirus containing NFAT-GFP, to determine factors that could induce NFAT nuclear translocation. Four millimolar Ca(2+) or pacing induced NFAT nuclear translocation. This effect was blocked by Cn inhibitors. In NRVMs Nifedipine (Nif, LTCC antagonist) blocked high Ca(2+)-induced NFAT nuclear translocation while SKF-96365 (TRP channel antagonist) and Nickel (Ni, TTCC antagonist) were less effective. The relative potency of these antagonists against Ca(2+) induced NFAT nuclear translocation (Nif>SKF-96365>Ni) was similar to their effects on Ca(2+) transients and the LTCC current. Infection of NRVM with viruses containing TRP channels also activated NFAT-GFP nuclear translocation and caused myocyte hypertrophy. TRP effects were reduced by SKF-96365, but were more effectively antagonized by Nif. These experiments suggest that Ca(2+) influx through LTCCs is the primary source of Ca(2+) to activate Cn-NFAT signaling in NRVMs and AFVMs. While TRP channels cause hypertrophy, they appear to do so through a mechanism involving Ca(2+) entry via LTCCs.
| S-EPMC3472041 | biostudies-literature
Project description:The active zone of presynaptic nerve terminals organizes the neurotransmitter release machinery, thereby enabling fast Ca2+-triggered synaptic vesicle exocytosis. BK-channels are Ca2+-activated large-conductance K+-channels that require close proximity to Ca2+-channels for activation and control Ca2+-triggered neurotransmitter release by accelerating membrane repolarization during action potential firing. How BK-channels are recruited to presynaptic Ca2+-channels, however, is unknown. Here, we show that RBPs (for RIM-binding proteins), which are evolutionarily conserved active zone proteins containing SH3- and FN3-domains, directly bind to BK-channels. We find that RBPs interact with RIMs and Ca2+-channels via their SH3-domains, but to BK-channels via their FN3-domains. Deletion of RBPs in calyx of Held synapses decreased and decelerated presynaptic BK-currents and depleted BK-channels from active zones. Our data suggest that RBPs recruit BK-channels into a RIM-based macromolecular active zone complex that includes Ca2+-channels, synaptic vesicles, and the membrane fusion machinery, thereby enabling tight spatio-temporal coupling of Ca2+-influx to Ca2+-triggered neurotransmitter release in a presynaptic terminal.
| S-EPMC6092624 | biostudies-literature
Project description:Spontaneous Ca2+-release events (SCaEs) from the sarcoplasmic reticulum play crucial roles in the initiation of cardiac arrhythmias by promoting triggered activity. However, the subcellular determinants of these SCaEs remain incompletely understood. Structural differences between atrial and ventricular cardiomyocytes, e.g., regarding the density of T-tubular membrane invaginations, may influence cardiomyocyte Ca2+-handling and the distribution of cardiac ryanodine receptors (RyR2) has recently been shown to undergo remodeling in atrial fibrillation. These data suggest that the subcellular distribution of Ca2+-handling proteins influences proarrhythmic Ca2+-handling abnormalities. Here, we employ computational modeling to provide an in-depth analysis of the impact of variations in subcellular RyR2 and L-type Ca2+-channel distributions on Ca2+-transient properties and SCaEs in a human atrial cardiomyocyte model. We incorporate experimentally observed RyR2 expression patterns and various configurations of axial tubules in a previously published model of the human atrial cardiomyocyte. We identify an increased SCaE incidence for larger heterogeneity in RyR2 expression, in which SCaEs preferentially arise from regions of high local RyR2 expression. Furthermore, we show that the propagation of Ca2+ waves is modulated by the distance between RyR2 bands, as well as the presence of experimentally observed RyR2 clusters between bands near the lateral membranes. We also show that incorporation of axial tubules in various amounts and locations reduces Ca2+-transient time to peak. Furthermore, selective hyperphosphorylation of RyR2 around axial tubules increases the number of spontaneous waves. Finally, we present a novel model of the human atrial cardiomyocyte with physiological RyR2 and L-type Ca2+-channel distributions that reproduces experimentally observed Ca2+-handling properties. Taken together, these results significantly enhance our understanding of the structure-function relationship in cardiomyocytes, identifying that RyR2 and L-type Ca2+-channel distributions have a major impact on systolic Ca2+ transients and SCaEs.
| S-EPMC6107030 | biostudies-literature
Project description:L-type voltage-gated Ca2+ channels (LTCCs) are implicated in neurodegenerative processes and cell death. Accordingly, LTCC antagonists have been proposed to be neuroprotective, although this view is disputed, because intentional LTCC activation can also have beneficial effects. LTCC-mediated Ca2+ influx influences mitochondrial function, which plays a crucial role in the regulation of cell viability. Hence, we investigated the effect of modulating LTCC-mediated Ca2+ influx on mitochondrial function in cultured hippocampal neurons. To activate LTCCs, neuronal activity was stimulated by increasing extracellular K+ or by application of the GABAA receptor antagonist bicuculline. The activity of LTCCs was altered by application of an agonistic (Bay K8644) or an antagonistic (isradipine) dihydropyridine. Our results demonstrated that activation of LTCC-mediated Ca2+ influx affected mitochondrial function in a bimodal manner. At moderate stimulation strength, ATP synthase activity was enhanced, an effect that involved Ca2+-induced Ca2+ release from intracellular stores. In contrast, high LTCC-mediated Ca2+ loads led to a switch in ATP synthase activity to reverse-mode operation. This effect, which required nitric oxide, helped to prevent mitochondrial depolarization and sustained increases in mitochondrial Ca2+ Our findings indicate a complex role of LTCC-mediated Ca2+ influx in the tuning and maintenance of mitochondrial function. Therefore, the use of LTCC inhibitors to protect neurons from neurodegeneration should be reconsidered carefully.
| S-EPMC7116774 | biostudies-literature
Project description:BackgroundAdministration of amplitude modulated 27·12 MHz radiofrequency electromagnetic fields (AM RF EMF) by means of a spoon-shaped applicator placed on the patient's tongue is a newly approved treatment for advanced hepatocellular carcinoma (HCC). The mechanism of action of tumour-specific AM RF EMF is largely unknown.MethodsWhole body and organ-specific human dosimetry analyses were performed. Mice carrying human HCC xenografts were exposed to AM RF EMF using a small animal AM RF EMF exposure system replicating human dosimetry and exposure time. We performed histological analysis of tumours following exposure to AM RF EMF. Using an agnostic genomic approach, we characterized the mechanism of action of AM RF EMF.FindingsIntrabuccal administration results in systemic delivery of athermal AM RF EMF from head to toe at levels lower than those generated by cell phones held close to the body. Tumour shrinkage results from differentiation of HCC cells into quiescent cells with spindle morphology. AM RF EMF targeted antiproliferative effects and cancer stem cell inhibiting effects are mediated by Ca2+ influx through Cav3·2 T-type voltage-gated calcium channels (CACNA1H) resulting in increased intracellular calcium concentration within HCC cells only.InterpretationIntrabuccally-administered AM RF EMF is a systemic therapy that selectively block the growth of HCC cells. AM RF EMF pronounced inhibitory effects on cancer stem cells may explain the exceptionally long responses observed in several patients with advanced HCC. FUND: Research reported in this publication was supported by the National Cancer Institute's Cancer Centre Support Grant award number P30CA012197 issued to the Wake Forest Baptist Comprehensive Cancer Centre (BP) and by funds from the Charles L. Spurr Professorship Fund (BP). DWG is supported by R01 AA016852 and P50 AA026117.
| S-EPMC6604666 | biostudies-literature
Project description:BACKGROUND AND PURPOSE: The calcimimetic, (R)-N-(3-(3-(trifluoromethyl)phenyl)propyl)-1-(1-napthyl)ethylamine hydrochloride (cinacalcet), which activates Ca²(+) -sensing receptors (CaR) in parathyroid glands, is used to treat hyperparathyroidism. Interestingly, CaR in perivascular nerves or endothelial cells is also thought to modulate vascular tone. This study aims to characterize the vascular actions of calcimimetics. EXPERIMENTAL APPROACH: In rat isolated small mesenteric arteries, the relaxant responses to the calcimimetics, cinacalcet and (R)-2-[[[1-(1-naphthyl)ethyl]amino]methyl]-1H-indole hydrochloride (calindol) were characterized, with particular emphasis on the role of CaR, endothelium, perivascular nerves, K(+) channels and Ca²(+) channels. Effects of L-ornithine, which activates a Ca(2+) -sensitive receptor related to CaR (GPRC6A), were also tested. KEY RESULTS: Cinacalcet induced endothelium-independent relaxation (pEC?? 5.58 ± 0.07, E(max) 97 ± 6%) that was insensitive to sensory nerve desensitization by capsaicin or blockade of large-conductance Ca²(+) -activated K(+) channels by iberiotoxin. Calindol, another calcimimetic, caused more potent relaxation (pEC?? 6.10 ± 0.10, E(max) 101 ± 6%), which was attenuated by endothelial removal or capsaicin, but not iberiotoxin. The negative modulator of CaR, calhex 231 or changes in [Ca²(+) ](o) had negligible effect on relaxation to both calcimimetics. The calcimimetics relaxed vessels precontracted with high [K(+) ](o) and inhibited Ca²(+) influx in endothelium-denuded vessels stimulated by methoxamine, but not ionomycin. They also inhibited contractions to the L-type Ca²(+) channel activator, BayK8644. L-ornithine induced small relaxation alone and had no effect on the responses to calcimimetics. CONCLUSION AND IMPLICATIONS: Cinacalcet and calindol are potent arterial relaxants. Under the experimental conditions used, they predominantly act by inhibiting Ca²(+) influx through L-type Ca²(+) channels into vascular smooth muscle, whereas Ca²(+) -sensitive receptors (CaR or GPRC6A) play a minor role.
| S-EPMC3041262 | biostudies-other
Project description:Given the complexity of the nervous system and its capacity for change, it is remarkable that robust, reproducible neural function and animal behavior can be achieved. It is now apparent that homeostatic signaling systems have evolved to stabilize neural function. At the neuromuscular junction (NMJ) of organisms ranging from Drosophila to human, inhibition of postsynaptic neurotransmitter receptor function causes a homeostatic increase in presynaptic release that precisely restores postsynaptic excitation. Here we address what occurs within the presynaptic terminal to achieve homeostatic potentiation of release at the Drosophila NMJ. By imaging presynaptic Ca(2+) transients evoked by single action potentials, we reveal a retrograde, transsynaptic modulation of presynaptic Ca(2+) influx that is sufficient to account for the rapid induction and sustained expression of the homeostatic change in vesicle release. We show that the homeostatic increase in Ca(2+) influx and release is blocked by a point mutation in the presynaptic CaV2.1 channel, demonstrating that the modulation of presynaptic Ca(2+) influx through this channel is causally required for homeostatic potentiation of release. Together with additional analyses, we establish that retrograde, transsynaptic modulation of presynaptic Ca(2+) influx through CaV2.1 channels is a key factor underlying the homeostatic regulation of neurotransmitter release.
| S-EPMC4367479 | biostudies-literature