scholarly journals Activation of SGK1.1 Upregulates the M-current in the Presence of Epilepsy Mutations

2021 ◽  
Vol 14 ◽  
Author(s):  
Elva Martin-Batista ◽  
Rían W. Manville ◽  
Belinda Rivero-Pérez ◽  
David Bartolomé-Martín ◽  
Diego Alvarez de la Rosa ◽  
...  
Keyword(s):  
Critical Role ◽  
Epileptic Encephalopathy ◽  
Electrical Excitability ◽  
Channel Activity ◽  
M Current ◽  
Proximity Ligation ◽  
Electrode Voltage ◽  
The Central Nervous System ◽  
Firing Properties ◽  
Excitability Of Neurons

In the central nervous system, the M-current plays a critical role in regulating subthreshold electrical excitability of neurons, determining their firing properties and responsiveness to synaptic input. The M-channel is mainly formed by subunits Kv7.2 and Kv7.3 that co-assemble to form a heterotetrametric channel. Mutations in Kv7.2 and Kv7.3 are associated with hyperexcitability phenotypes including benign familial neonatal epilepsy (BFNE) and neonatal epileptic encephalopathy (NEE). SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), increases M-current density in neurons, leading to reduced excitability and protection against seizures. Herein, using two-electrode voltage clamp on Xenopus laevis oocytes, we demonstrate that SGK1.1 selectively activates heteromeric Kv7 subunit combinations underlying the M-current. Importantly, activated SGK1.1 increases M-channel activity in the presence of two different epilepsy mutations found in Kv7.2, R207W and A306T. In addition, proximity ligation assays in the N2a cell line allowed us to address the effect of these mutations on Kv7-SGK1.1-Nedd4 molecular associations, a proposed pathway underlying augmentation of M-channel activity by SGK1.1

scholarly journals Activation of SGK1.1 up-regulates the M-current in the presence of epilepsy mutations

2021 ◽  
Author(s):  
Elva Martin-Batista ◽  
Rian W Manville ◽  
Belinda Rivero-Perez ◽  
David Bartolome-Martin ◽  
Diego Alvarez de la Rosa ◽  
...  
Keyword(s):  
Critical Role ◽  
Epileptic Encephalopathy ◽  
Xenopus Laevis Oocytes ◽  
Channel Activity ◽  
M Current ◽  
Proximity Ligation ◽  
Electrode Voltage ◽  
The Central Nervous System ◽  
Firing Properties ◽  
Excitability Of Neurons

In the central nervous system, the M-current plays a critical role in regulating subthreshold electrical excitability of neurons, determining their firing properties and responsiveness to synaptic input. The M-channel is mainly formed by subunits Kv7.2 and Kv7.3 that co-assemble to form a heterotetrametric channel. Mutations in Kv7.2 and Kv7.3 are associated with hyperexcitability phenotypes including benign familial neonatal epilepsy (BFNE) and neonatal epileptic encephalopathy (NEE). SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), increases M-current density in neurons, leading to reduced excitability and protection against seizures. Herein, using two-electrode voltage clamp on Xenopus laevis oocytes, we demonstrate that SGK1.1 selectively activates heteromeric Kv7 subunit combinations underlying the M-current. Importantly, activated SGK1.1 is able to up-regulate M-channel activity in the presence of two different epilepsy mutations found in Kv7.2 subunit, R207W and A306T. In addition, proximity ligation assays in the N2a cell line allowed us to address the effect of these mutations on Kv7-SGK1.1-Nedd4 molecular associations, a proposed pathway underlying M-channel up-regulation by SGK1.1

scholarly journals Nonreciprocal mechanisms in up- and downregulation of spinal motoneuron excitability by modulators of KCNQ/Kv7 channels

2016 ◽  
Vol 116 (5) ◽  
pp. 2114-2124 ◽  
Author(s):  
Joseph Lombardo ◽  
Melissa A. Harrington
Keyword(s):  
Initial Segment ◽  
Input Resistance ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Channel Activity ◽  
Spinal Motoneurons ◽  
M Current ◽  
Kv7 Channels ◽  
Axonal Initial Segment ◽  
The Central Nervous System

KCNQ/Kv7 channels form a slow noninactivating K+ current, also known as the M current. They activate in the subthreshold range of membrane potentials and regulate different aspects of excitability in neurons of the central nervous system. In spinal motoneurons (MNs), KCNQ/Kv7 channels have been identified in the somata, axonal initial segment, and nodes of Ranvier, where they generate a slow, noninactivating, K+ current sensitive to both muscarinic receptor-mediated inhibition and KCNQ/Kv7 channel blockers. In this study, we thoroughly reevaluated the function of up- and downregulation of KCNQ/Kv7 channels in mouse immature spinal MNs. Using electrophysiological techniques together with specific pharmacological modulators of the activity of KCNQ/Kv7 channels, we show that enhancement of the activity of these channels decreases the excitability of spinal MNs in mouse neonates. This action on MNs results from a combination of hyperpolarization of the resting membrane potential, a decrease in the input resistance, and depolarization of the voltage threshold. On the other hand, the effect of inhibition of KCNQ/Kv7 channels suggested that these channels play a limited role in regulating basal excitability. Computer simulations confirmed that pharmacological enhancement of KCNQ/Kv7 channel activity decreases excitability and also suggested that the effects of inhibition of KCNQ/Kv7 channels on the excitability of spinal MNs do not depend on a direct effect in these neurons but likely on spinal cord synaptic partners. These results indicate that KCNQ/Kv7 channels have a fundamental role in the modulation of the excitability of spinal MNs acting both in these neurons and in their local presynaptic partners.

scholarly journals NGF Inhibits M/KCNQ Currents and Selectively Alters Neuronal Excitability in Subsets of Sympathetic Neurons Depending on their M/KCNQ Current Background

2008 ◽  
Vol 131 (6) ◽  
pp. 575-587 ◽  
Author(s):  
Zhanfeng Jia ◽  
Junjie Bei ◽  
Lise Rodat-Despoix ◽  
Boyi Liu ◽  
Qingzhong Jia ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Sympathetic Neurons ◽  
Critical Role ◽  
Neuronal Cell ◽  
Similar Proportion ◽  
M Current ◽  
Proliferation And Differentiation ◽  
Cervical Ganglion ◽  
Firing Properties ◽  
G Protein Coupled

M/KCNQ currents play a critical role in the determination of neuronal excitability. Many neurotransmitters and peptides modulate M/KCNQ current and neuronal excitability through their G protein–coupled receptors. Nerve growth factor (NGF) activates its receptor, a member of receptor tyrosine kinase (RTK) superfamily, and crucially modulates neuronal cell survival, proliferation, and differentiation. In this study, we studied the effect of NGF on the neuronal (rat superior cervical ganglion, SCG) M/KCNQ currents and excitability. As reported before, subpopulation SCG neurons with distinct firing properties could be classified into tonic, phasic-1, and phasic-2 neurons. NGF inhibited M/KCNQ currents by similar proportion in all three classes of SCG neurons but increased the excitability only significantly in tonic SCG neurons. The effect of NGF on excitability correlated with a smaller M-current density in tonic neurons. The present study indicates that NGF is an M/KCNQ channel modulator and the characteristic modulation of the neuronal excitability by NGF may have important physiological implications.

Response to Steroids in IQSEC2-Related Encephalopathy Presenting with Rett-Like Phenotype and Infantile Spasms

2020 ◽  
Author(s):  
Divya Nagabushana ◽  
Aparajita Chatterjee ◽  
Raghavendra Kenchaiah ◽  
Ajay Asranna ◽  
Gautham Arunachal ◽  
...  
Keyword(s):  
Late Onset ◽  
Neurodevelopmental Disorder ◽  
Epileptic Encephalopathy ◽  
Infantile Spasms ◽  
The Past ◽  
Resource Limited ◽  
The Central Nervous System ◽  
Motor Milestone ◽  
Behavior And Cognition ◽  
Atypical Rett Syndrome

Abstract Introduction IQSEC2-related encephalopathy is an X-linked childhood neurodevelopmental disorder with intellectual disability, epilepsy, and autism. This disorder is caused by a mutation in the IQSEC2 gene, the product of which plays an important role in the development of the central nervous system. Case Report We describe the symptomatology, clinical course, and management of a 17-month-old male child with a novel IQSEC2 mutation. He presented with an atypical Rett syndrome phenotype with developmental delay, autistic features, midline stereotypies, microcephaly, hypotonia and epilepsy with multiple seizure types including late-onset infantile spasms. Spasms were followed by worsening of behavior and cognition, and regression of acquired milestones. Treatment with steroids led to control of spasms and improved attention, behavior and recovery of lost motor milestone. In the past 10 months following steroid therapy, child lags in development, remains autistic with no further seizure recurrence. Conclusion IQSEC2-related encephalopathy may present with atypical Rett phenotype and childhood spasms. In resource-limited settings, steroids may be considered for spasm remission in IQSEC2-related epileptic encephalopathy.

Heterogeneity and Proliferative and Differential Regulators of NG2-glia in Physiological and Pathological States

2020 ◽  
Vol 27 (37) ◽  
pp. 6384-6406 ◽  
Author(s):  
Zuo Zhang ◽  
Hongli Zhou ◽  
Jiyin Zhou
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Physiological State ◽  
Critical Role ◽  
Adult Brain ◽  
Pathological State ◽  
Peripheral Neurons ◽  
Neuronal Synapses ◽  
The Central Nervous System ◽  
Rapid Modulation

NG2-glia, also called Oligodendrocyte Precursor Cells (OPCs), account for approximately 5%-10% of the cells in the developing and adult brain and constitute the fifth major cell population in the central nervous system. NG2-glia express receptors and ion channels involved in rapid modulation of neuronal activities and signaling with neuronal synapses, which have functional significance in both physiological and pathological states. NG2-glia participate in quick signaling with peripheral neurons via direct synaptic touches in the developing and mature central nervous system. These distinctive glia perform the unique function of proliferating and differentiating into oligodendrocytes in the early developing brain, which is critical for axon myelin formation. In response to injury, NG2-glia can proliferate, migrate to the lesions, and differentiate into oligodendrocytes to form new myelin sheaths, which wrap around damaged axons and result in functional recovery. The capacity of NG2-glia to regulate their behavior and dynamics in response to neuronal activity and disease indicate their critical role in myelin preservation and remodeling in the physiological state and in repair in the pathological state. In this review, we provide a detailed summary of the characteristics of NG2-glia, including their heterogeneity, the regulators of their proliferation, and the modulators of their differentiation into oligodendrocytes.

The Yin and Yang of BK Channels in Epilepsy

2018 ◽  
Vol 17 (4) ◽  
pp. 272-279 ◽  
Author(s):  
Yudan Zhu ◽  
Shuzhang Zhang ◽  
Yijun Feng ◽  
Qian Xiao ◽  
Jiwei Cheng ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Bk Channels ◽  
Bk Channel ◽  
Potential Shape ◽  
Yin And Yang ◽  
The Central Nervous System ◽  
Action Potential Shape ◽  
Excitability Of Neurons

Background & Objective: The large conductance calcium-activated potassium (BK) channel, extensively distributed in the central nervous system (CNS), is considered as a vital player in the pathogenesis of epilepsy, with evidence implicating derangement of K+ as well as regulating action potential shape and duration. However, unlike other channels implicated in epilepsy whose function in neurons could clearly be labeled “excitatory” or “inhibitory”, the unique physiological behavior of the BK channel allows it to both augment and decrease the excitability of neurons. Thus, the role of BK in epilepsy is controversial so far, and a growing area of intense investigation. Conclusion: Here, this review aims to highlight recent discoveries on the dichotomous role of BK channels in epilepsy, focusing on relevant BK-dependent pro- as well as antiepileptic pathways, and discuss the potential of BK specific modulators for the treatment of epilepsy.

scholarly journals The Class II Phosphatidylinositol 3 kinase C2β Is Required for the Activation of the K+ Channel KCa3.1 and CD4 T-Cells

2009 ◽  
Vol 20 (17) ◽  
pp. 3783-3791 ◽  
Author(s):  
Shekhar Srivastava ◽  
Lie Di ◽  
Olga Zhdanova ◽  
Zhai Li ◽  
Santosha Vardhana ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cd4 T Cells ◽  
Critical Role ◽  
Class Ii ◽  
K Channel ◽  
Channel Activity ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

The Ca2+-activated K+ channel KCa3.1 is required for Ca2+ influx and the subsequent activation of T-cells. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, directly phosphorylates and activates KCa3.1 and is required for the activation of human CD4 T lymphocytes. We now show that the class II phosphatidylinositol 3 kinase C2β (PI3K-C2β) is activated by the T-cell receptor (TCR) and functions upstream of NDPK-B to activate KCa3.1 channel activity. Decreased expression of PI3K-C2β by siRNA in human CD4 T-cells resulted in inhibition of KCa3.1 channel activity. The inhibition was due to decreased phosphatidylinositol 3-phosphate [PI(3)P] because dialyzing PI3K-C2β siRNA-treated T-cells with PI(3)P rescued KCa3.1 channel activity. Moreover, overexpression of PI3K-C2β in KCa3.1-transfected Jurkat T-cells led to increased TCR-stimulated activation of KCa3.1 and Ca2+ influx, whereas silencing of PI3K-C2β inhibited both responses. Using total internal reflection fluorescence microscopy and planar lipid bilayers, we found that PI3K-C2β colocalized with Zap70 and the TCR in peripheral microclusters in the immunological synapse. This is the first demonstration that a class II PI3K plays a critical role in T-cell activation.

Abstract 388: ICV Angiotensin-(1-7) Improves Cardiac Function and Attenuates Remodeling In (mren2)27 Transgenic Hypertensive Rats

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Lucas M Kangussu ◽  
Marcos B Melo ◽  
Priscila S Guimarães ◽  
Ana P Nadu ◽  
Michael Bader ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Natriuretic Peptide ◽  
Critical Role ◽  
Renin Angiotensin System ◽  
Vagal Activity ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Angiotensin System ◽  
The Central Nervous System ◽  
Tgf Β1

Overactivity of the renin-angiotensin system (RAS), through Ang II/AT1 axis, plays a critical role in the pathogenesis of cardiovascular diseases. On the other hand, Ang-(1-7)/Mas axis is recognized to attenuate the deleterious effects of the RAS at different sites including the central nervous system. In the present study, Sprague Dawley (SD) and transgenic hypertensive rats (mRen2)27, instrumented with telemetry probes for arterial pressure (AP) measurements, were subjected to 14 days of lateral ventricle (ICV) infusion of Ang-(1-7) (200 ng/h) alone, Ang-(1-7) (200 ng/h) in association with a Mas receptor antagonist (A779, 1 μg/h) or saline (0.5 ml/hour) through osmotic mini-pumps. Ang-(1-7) ICV attenuated hypertension of (mRen2)27 rats (144±8 mmHg vs 174±3 mmHg, before. The AP lowering effect of ICV Ang-(1-7) was completely blocked by A779 (174±12 mmHg). Cardiac hypertrophy and dysfunction, evaluated by echocardiography, of (mRen2)27 rats were attenuated in Ang-(1-7) infused rats. The increased levels of atrial natriuretic peptide, brain natriuretic peptide, collagen I, fibronectin and TGF-β1 in the heart of (mRen2)27 rats were significantly reduced by Ang-(1-7) infusion and partially reversed by the concomitant infusion of A-779. Further, cardiac effects induced by ICV Ang-(1-7) were accompanied by an attenuation of the increased ratio sympathetic/ vagal activity to the heart of (mRen2)27. The data of the present study indicate that short-term central infusion of Ang-(1-7) produces Mas-mediate improvement in cardiac function and attenuates cardiac remodeling in (mRen2)27 hypertensive rats, probably through an improvement of the autonomic balance to the heart. Support: CAPES and FAPEMIG/CNPq through INCT-NanoBioFar and PRONEX.

FC 006PP2A PHOSPHATASE INHIBITION IS ANTI-FIBROTIC THROUGH SER77 PHOSPHORYLATION-MEDIATED ARNT/ARNT HOMODIMER FORMATION

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Gunsmaa Nyamsuren ◽  
Gregor Christof Rapp ◽  
Björn Tampe ◽  
Michael Zeisberg
Keyword(s):  
Molecular Mechanisms ◽  
Therapeutic Potential ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Receptor Expression ◽  
Proximity Ligation Assay ◽  
Proximity Ligation ◽  
Aryl Hydrocarbon ◽  
Ureter Obstruction

Abstract Background and Aims Aryl hydrocarbon receptor nuclear translocator (ARNT) mediates anti-fibrotic activity in kidney and liver through induction of ALK3-receptor expression and subsequently increased Smad1/5/8 signaling. While expression of ARNT can be pharmacologically induced by sub-immunosuppressive doses of FK506 or by GPI1046, its anti-fibrotic activity is only realized when ARNT-ARNT homodimers form, as opposed to formation of ARNT-AHR or ARNT-HIF1α heterodimers. Mechanisms underlying ARNTs dimerization decision to specifically form ARNT-ARNT homodimers and possible cues to specifically induce ARNT homodimerization have been previously unknown. We here aimed to elucidate the molecular mechanisms underlying control of ARNT dimerization decision and to explore its therapeutic potential. Method We analyzed dimerization of recombinant and native ARNT by immunoprecipitation, MALDI-TOF mass spectrometry, and LS-MS/MS analysis and proximity ligation assay. Phosphorylation sites were mapped through generation of phosphorylation site mutants and through pharmacological inhibition. For in vivo analysis we challenged mice with model of unilateral ureter obstruction and carbon tetrachloride to induce fibrosis in kidney and liver. Results Here we report that inhibition of PP2A phosphatase activity increases intracellular accumulation of ARNT-ARNT homodimers. This effect is dependent on enhanced ARNT-ARNT homodimerization and decreased ARNT proteolytic degradation, but independent of ARNT transcription (which remains unchanged upon PP2A inhibition). We further identify that Ser77 phosphorylation plays a critical role in ARNT homodimerization, as ARNT-ARNT homodimers do not form with Ser77/Asp-mutant ARNT proteins. In light of previous studies which identified anti-fibrotic activity upon increased ARNT expression, we further demonstrate attenuated fibrosis upon monotherapy with the PP2A inhibitor LB100, and additive anti-fibrotic activities upon combination with pharmacological inducers of ARNT expression FK506 or GPI1046 in murine models of kidney and liver fibrosis. Conclusion Our study provides additional evidence for the anti-fibrotic activity of ARNT and reveals Ser77 phosphorylation as a novel pharmacological target to realize the therapeutic potential of increased ARNT transactivation activity.

Central mineralocorticoid receptor blockade decreases plasma TNF-α after coronary artery ligation in rats

2003 ◽  
Vol 284 (2) ◽  
pp. R328-R335 ◽  
Author(s):  
Joseph Francis ◽  
Robert M. Weiss ◽  
Alan Kim Johnson ◽  
Robert B. Felder
Keyword(s):  
Heart Failure ◽  
Central Nervous System ◽  
Nervous System ◽  
Mineralocorticoid Receptor ◽  
Critical Role ◽  
Evaluation Study ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Tnf Α ◽  
The Central Nervous System

The Randomized Aldactone Evaluation Study (RALES) demonstrated a substantial clinical benefit to blocking the effects of aldosterone (Aldo) in patients with heart failure. We recently demonstrated that the enhanced renal conservation of sodium and water in rats with heart failure can be reduced by blocking the central nervous system effects of Aldo with the mineralocorticoid receptor (MR) antagonist spironolactone (SL). Preliminary data from our laboratory suggested that central MR might contribute to another peripheral mechanism in heart failure, the release of proinflammatory cytokines. In the present study, SL (100 ng/h for 21 days) or ethanol vehicle (Veh) was administered via the 3rd cerebral ventricle to one group of rats after coronary ligation (CL) or sham CL (Sham) to induce congestive heart failure (CHF). In Veh-treated CHF rats, tumor necrosis factor-α (TNF-α) levels increased during day 1 and continued to increase throughout the 3-wk observation period. In CHF rats treated with SL, started 24 h after CL, TNF-α levels rose initially but retuned to control levels by day 5 after CL and remained low throughout the study. These findings suggest that activation of MR in the central nervous system plays a critical role in regulating TNF-α release in heart failure rats. Thus some of the beneficial effect of blocking MR in heart failure could be due at least in part to a reduction in TNF-α production.

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