Browse
Submit Data
Databases
API
Help

Dataset Information

29 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

A missense mutation converts the Na⁺,K⁺-ATPase into an ion channel and causes therapy-resistant epilepsy.

ABSTRACT: The ion pump Na⁺,K⁺-ATPase is a critical determinant of neuronal excitability; however, its role in the etiology of diseases of the central nervous system (CNS) is largely unknown. We describe here the molecular phenotype of a Trp931Arg mutation of the Na⁺,K⁺-ATPase catalytic α1 subunit in an infant diagnosed with therapy-resistant lethal epilepsy. In addition to the pathological CNS phenotype, we also detected renal wasting of Mg²⁺. We found that membrane expression of the mutant α1 protein was low, and ion pumping activity was lost. Arginine insertion into membrane proteins can generate water-filled pores in the plasma membrane, and our molecular dynamic (MD) simulations of the principle states of Na⁺,K⁺-ATPase transport demonstrated massive water inflow into mutant α1 and destabilization of the ion-binding sites. MD simulations also indicated that a water pathway was created between the mutant arginine residue and the cytoplasm, and analysis of oocytes expressing mutant α1 detected a nonspecific cation current. Finally, neurons expressing mutant α1 were observed to be depolarized compared with neurons expressing wild-type protein, compatible with a lowered threshold for epileptic seizures. The results imply that Na⁺,K⁺-ATPase should be considered a neuronal locus minoris resistentia in diseases associated with epilepsy and with loss of plasma membrane integrity.

SUBMITTER: Ygberg S

PROVIDER: S-EPMC8637647 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Capsazepine, a synthetic vanilloid that converts the Na,K-ATPase to Na-ATPase.

Project description:Capsazepine (CPZ), a synthetic capsaicin analogue, inhibits ATP hydrolysis by Na,K-ATPase in the presence but not in the absence of K(+). Studies with purified membranes revealed that CPZ reduced Na(+)-dependent phosphorylation by interference with Na(+) binding from the intracellular side of the membrane. Kinetic analyses showed that CPZ stabilized an enzyme species that constitutively occluded K(+). Low-affinity ATP interaction with the enzyme was strongly reduced after CPZ treatment; in contrast, indirectly measured interaction with ADP was much increased, which suggests that composite regulatory communication with nucleotides takes place during turnover. Studies with lipid vesicles revealed that CPZ reduced ATP-dependent digitoxigenin-sensitive (22)Na(+) influx into K(+)-loaded vesicles only at saturating ATP concentrations. The drug apparently abolishes the regulatory effect of ATP on the pump. Drawing on previous homology modeling studies of Na,K-ATPase to atomic models of sarcoplasmic reticulum Ca-ATPase and on kinetic data, we propose that CPZ uncouples an Na(+) cycle from an Na(+)/K(+) cycle in the pump. The Na(+) cycle possibly involves transport through the recently characterized Na(+)-specific site. A shift to such an uncoupled mode is believed to produce pumps mediating uncoupled Na(+) efflux by modifying the transport stoichiometry of single pump units.

| S-EPMC2234217 | biostudies-literature

Oxidative stress induced by the anti-cancer agents, plumbagin, and atovaquone, inhibits ion transport through Na+/K+-ATPase.

Project description:Oxidative stress inhibits Na+/K+-ATPase (NKA), the ion channel that maintains membrane potential. Here, we investigate the role of oxidative stress-mediated by plumbagin and atovaquone in the inhibition of NKA activity. We confirm that plumbagin and atovaquone inhibit the proliferation of three human (OVCAR-3, SKOV-3, and TYKNu) and one mouse (ID8) ovarian cancer cell lines. The oxygen radical scavenger, N-acetylcysteine (NAC), attenuates the chemotoxicity of plumbagin and atovaquone. Whole-cell patch clamping demonstrates that plumbagin and atovaquone inhibit outward and the inward current flowing through NKA in SKOV-3 and OVCAR-3. Although both drugs decrease cellular ATP; providing exogenous ATP (5 mM) in the pipet solution used during patch clamping did not recover NKA activity in the plumbagin or atovaquone treated SKOV-3 and OVCAR-3 cells. However, pretreatment of the cells with NAC completely abrogated the NKA inhibitory activity of plumbagin and atovaquone. Exposure of the SKOV-3 cells to either drug significantly decreases the expression of NKA. We conclude that oxidative stress caused by plumbagin and atovaquone degrades NKA, resulting in the inability to maintain ion transport. Therefore, when evaluating compounds that induce oxidative stress, it is important to consider the contribution of NKA inhibition to their cytotoxic effects on tumor cells.

| S-EPMC7659016 | biostudies-literature

A missense mutation of the Na+ channel alpha II subunit gene Na(v)1.2 in a patient with febrile and afebrile seizures causes channel dysfunction.

Project description:Generalized epilepsy with febrile seizures plus (GEFS+), a clinical subset of febrile seizures (FS), is characterized by frequent episodes beyond 6 years of age (FS+) and various types of subsequent epilepsy. Mutations in beta1 and alpha(I)-subunit genes of voltage-gated Na(+) channels have been associated with GEFS+1 and 2, respectively. Here, we report a mutation resulting in an amino acid exchange (R188W) [corrected] in the gene encoding the alpha-subunit of neuronal voltage-gated Na(+) channel type II (Na(v)1.2) in a patient with FS associated with afebrile seizures. The mutation R188W [corrected] occurring on Arg(187), a highly conserved residue among voltage-gated Na(+) channels, was not found in 224 alleles of unaffected individuals. Whole-cell patch clamp recordings on human embryonic kidney (HEK) cells expressing a rat wild-type (rNa(v)1.2) and the corresponding mutant channels showed that the mutant channel inactivated more slowly than wild-type whereas the Na(+) channel conductance was not affected. Prolonged residence in the open state of the R188W [corrected] mutant channel may augment Na(+) influx and thereby underlie the neuronal hyperexcitability that induces seizure activity. Even though a small pedigree could not show clear cosegregation with the disease phenotype, these findings strongly suggest the involvement of Na(v)1.2 in a human disease and propose the R188W [corrected] mutation as the genetic defect responsible for febrile seizures associated with afebrile seizures.

| S-EPMC33477 | biostudies-literature

MicroED structure of the NaK ion channel reveals a Na+ partition process into the selectivity filter.

Project description:Sodium (Na+) is a ubiquitous and important inorganic salt mediating many critical biological processes such as neuronal excitation, signaling, and facilitation of various transporters. The hydration states of Na+ are proposed to play critical roles in determining the conductance and the selectivity of Na+ channels, yet they are rarely captured by conventional structural biology means. Here we use the emerging cryo-electron microscopy (cryoEM) method micro-electron diffraction (MicroED) to study the structure of a prototypical tetrameric Na+-conducting channel, NaK, to 2.5 Å resolution from nano-crystals. Two new conformations at the external site of NaK are identified, allowing us to visualize a partially hydrated Na+ ion at the entrance of the channel pore. A process of dilation coupled with Na+ movement is identified leading to valuable insights into the mechanism of ion conduction and gating. This study lays the ground work for future studies using MicroED in membrane protein biophysics.

| S-EPMC6112790 | biostudies-literature

Na Channel ? Subunits: Overachievers of the Ion Channel Family.

Project description:Voltage-gated Na(+) channels (VGSCs) in mammals contain a pore-forming ? subunit and one or more ? subunits. There are five mammalian ? subunits in total: ?1, ?1B, ?2, ?3, and ?4, encoded by four genes: SCN1B-SCN4B. With the exception of the SCN1B splice variant, ?1B, the ? subunits are type I topology transmembrane proteins. In contrast, ?1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC ? subunits are multifunctional. While they do not form the ion channel pore, ? subunits alter gating, voltage-dependence, and kinetics of VGSC? subunits and thus regulate cellular excitability in vivo. In addition to their roles in channel modulation, ? subunits are members of the immunoglobulin superfamily of cell adhesion molecules and regulate cell adhesion and migration. ? subunits are also substrates for sequential proteolytic cleavage by secretases. An example of the multifunctional nature of ? subunits is ?1, encoded by SCN1B, that plays a critical role in neuronal migration and pathfinding during brain development, and whose function is dependent on Na(+) current and ?-secretase activity. Functional deletion of SCN1B results in Dravet Syndrome, a severe and intractable pediatric epileptic encephalopathy. ? subunits are emerging as key players in a wide variety of physiopathologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, Huntington's disease, neuropsychiatric disorders, neuropathic and inflammatory pain, and cancer. ? subunits mediate multiple signaling pathways on different timescales, regulating electrical excitability, adhesion, migration, pathfinding, and transcription. Importantly, some ? subunit functions may operate independently of ? subunits. Thus, ? subunits perform critical roles during development and disease. As such, they may prove useful in disease diagnosis and therapy.

| S-EPMC3181431 | biostudies-literature

NRSF mediated epigenetic mechanisms of ion channel dysfunction in experimental temporal lobe epilepsy

Project description:This SuperSeries is composed of the SubSeries listed below.

2014-08-12 | GSE22899 | GEO

Curcumin, a Multi-Ion Channel Blocker That Preferentially Blocks Late Na+ Current and Prevents I/R-Induced Arrhythmias.

Project description:Increasing evidence shows that Curcumin (Cur) has a protective effect against cardiovascular diseases. However, the role of Cur in the electrophysiology of cardiomyocytes is currently not entirely understood. Therefore, the present study was conducted to investigate the effects of Cur on the action potential and transmembrane ion currents in rabbit ventricular myocytes to explore its antiarrhythmic property. The whole-cell patch clamp was used to record the action potential and ion currents, while the multichannel acquisition and analysis system was used to synchronously record the electrocardiogram and monophasic action potential. The results showed that 30 μmol/L Cur shortened the 50 and 90% repolarization of action potential by 17 and 7%, respectively. In addition, Cur concentration dependently inhibited the Late-sodium current (I Na.L), Transient-sodium current (I Na.T), L-type calcium current (I Ca.L), and Rapidly delayed rectifying potassium current (I Kr), with IC50 values of 7.53, 398.88, 16.66, and 9.96 μmol/L, respectively. Importantly, the inhibitory effect of Cur on I Na.L was 52.97-fold higher than that of I Na.T. Moreover, Cur decreased ATX II-prolonged APD, suppressed the ATX II-induced early afterdepolarization (EAD) and Ca2+-induced delayed afterdepolarization (DAD) in ventricular myocytes, and reduced the occurrence and average duration of ventricular tachycardias and ventricular fibrillations induced by ischemia-reperfusion injury. In conclusion, Cur inhibited I Na.L, I Na.T, I Ca.L, and I Kr; shortened APD; significantly suppressed EAD and DAD-like arrhythmogenic activities at the cellular level; and exhibited antiarrhythmic effect at the organ level. It is first revealed that Cur is a multi-ion channel blocker that preferentially blocks I Na.L and may have potential antiarrhythmic property.

| S-EPMC7472421 | biostudies-literature

Specific decreasing of Na+ channel expression on the lateral membrane of cardiomyocytes causes fatal arrhythmias in Brugada syndrome.

Project description:Reduced cardiac sodium (Na+) channel current (INa) resulting from the loss-of-function of Na+ channel is a major cause of lethal arrhythmias in Brugada syndrome (BrS). Inspired by previous experimental studies which showed that in heart diseases INa was reduced along with expression changes in Na+ channel within myocytes, we hypothesized that the local decrease in INa caused by the alteration in Na+ channel expression in myocytes leads to the occurrence of phase-2 reentry, the major triggering mechanism of lethal arrhythmias in BrS. We constructed in silico human ventricular myocardial strand and ring models, and examined whether the Na+ channel expression changes in each myocyte cause the phase-2 reentry in BrS. Reducing Na+ channel expression in the lateral membrane of each myocyte caused not only the notch-and-dome but also loss-of-dome type action potentials and slowed conduction, both of which are typically observed in BrS patients. Furthermore, the selective reduction in Na+ channels on the lateral membrane of each myocyte together with spatial tissue heterogeneity of Na+ channel expression caused the phase-2 reentry and phase-2 reentry-mediated reentrant arrhythmias. Our data suggest that the BrS phenotype is strongly influenced by expression abnormalities as well as genetic abnormalities of Na+ channels.

| S-EPMC7673036 | biostudies-literature

NRSF mediated epigenetic mechanisms of ion channel dysfunction in experimental temporal lobe epilepsy

Project description:This SuperSeries is composed of the SubSeries listed below. Refer to individual Series

2014-08-12 | E-GEOD-22899 | biostudies-arrayexpress

Na+/K+-ATPase-Targeted Cytotoxicity of (+)-Digoxin and Several Semisynthetic Derivatives.

Project description:(+)-Digoxin (1) is a well-known cardiac glycoside long used to treat congestive heart failure and found more recently to show anticancer activity. Several known cardenolides (2-5) and two new analogues, (+)-8(9)-β-anhydrodigoxigenin (6) and (+)-17-epi-20,22-dihydro-21α-hydroxydigoxin (7), were synthesized from 1 and evaluated for their cytotoxicity toward a small panel of human cancer cell lines. A preliminary structure-activity relationship investigation conducted indicated that the C-12 and C-14 hydroxy groups and the C-17 unsaturated lactone unit are important for 1 to mediate its cytotoxicity toward human cancer cells, but the C-3 glycosyl residue seems to be less critical for such an effect. Molecular docking profiles showed that the cytotoxic 1 and the noncytotoxic derivative 7 bind differentially to Na+/K+-ATPase. The HO-12β, HO-14β, and HO-3'aα hydroxy groups of (+)-digoxin (1) may form hydrogen bonds with the side-chains of Asp121 and Asn122, Thr797, and Arg880 of Na+/K+-ATPase, respectively, but the altered lactone unit of 7 results in a rotation of its steroid core, which depotentiates the binding between this compound and Na+/K+-ATPase. Thus, 1 was found to inhibit Na+/K+-ATPase, but 7 did not. In addition, the cytotoxic 1 did not affect glucose uptake in human cancer cells, indicating that this cardiac glycoside mediates its cytotoxicity by targeting Na+/K+-ATPase but not by interacting with glucose transporters.

| S-EPMC7243443 | biostudies-literature