Maintenance of Na+ and K+ gradients across the cell plasma membrane is an essential process for mammalian cell survival. An enzyme responsible for this process, sodium-potassium ATPase (NKA), has been currently extensively studied as a potential anticancer target, especially in lung cancer and glioblastoma. To date, many NKA inhibitors, mainly of natural origin from the family of cardiac steroids (CSs), have been reported and extensively studied. Interestingly, upon CS binding to NKA at nontoxic doses, the role of NKA as a receptor is activated and intracellular signaling is triggered, upon which cancer cell death occurs, which lies in the expression of different NKA isoforms than in healthy cells. Two major CSs, digoxin and digitoxin, originally used for the treatment of cardiac arrhythmias, are also being tested for another indication-cancer. Such drug repositioning has a big advantage in smoother approval processes. Besides this, novel CS derivatives with improved performance are being developed and evaluated in combination therapy. This article deals with the NKA structure, mechanism of action, activity modulation, and its most important inhibitors, some of which could serve not only as a powerful tool to combat cancer, but also help to decipher the so-far poorly understood NKA regulation.
- MeSH
- digitoxin chemie terapeutické užití MeSH
- digoxin chemie terapeutické užití MeSH
- glioblastom farmakoterapie enzymologie patologie MeSH
- inhibitory enzymů chemie terapeutické užití MeSH
- izoenzymy antagonisté a inhibitory chemie metabolismus MeSH
- klinické zkoušky jako téma MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární modely MeSH
- nádory mozku farmakoterapie enzymologie patologie MeSH
- nádory plic farmakoterapie enzymologie patologie MeSH
- ouabain chemie terapeutické užití MeSH
- přehodnocení terapeutických indikací léčivého přípravku MeSH
- protinádorové látky chemie terapeutické užití MeSH
- sodíko-draslíková ATPasa antagonisté a inhibitory chemie metabolismus MeSH
- vazba proteinů MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
The lipidic liquid-crystalline cubic phase (LCP) is a membrane-mimetic material useful for the stabilization and structural analysis of membrane proteins. Here, we focused on the incorporation of the membrane ATP-hydrolysing sodium/potassium transporter Na+/K+-ATPase (NKA) into a monoolein-derived LCP. Small-angle X-ray scattering was employed for the determination of the LCP structure, which was of Pn3m symmetry for all the formulations studied. The fully characterized NKA-LCP material was immobilized onto a glassy carbon electrode, forming a highly stable enzyme electrode and a novel sensing platform. A typical NKA voltammetric signature was monitored via the anodic reaction of tyrosine and tryptophan residues. The in situ enzyme activity evaluation was based on the ability of NKA to transform ATP to ADP and free phosphate, the latter reacting with ammonium molybdate to form the ammonium phosphomolybdate complex under acidic conditions. The square-wave voltammetric detection of phosphomolybdate was performed and complemented with spectrophotometric measurement at 710nm. The anodic voltammetric response, corresponding to the catalytic ATP-hydrolysing function of NKA incorporated into the LCP, was monitored at around + 0.2V vs. Ag/AgCl in the presence or absence of ouabain, a specific NKA inhibitor. NKA incorporated into the LCP retained its ATP-hydrolysing activity for 7 days, while the solubilized protein became practically inactive. The novelty of this work is the first incorporation of NKA into a lipidic cubic phase with consequent enzyme functionality and stability evaluation using voltammetric detection. The application of LCPs could also be important in the further development of new membrane protein electrochemical sensors and enzyme electrodes.
- MeSH
- adenosintrifosfát metabolismus MeSH
- biosenzitivní techniky metody MeSH
- enzymatické testy metody MeSH
- enzymy imobilizované chemie metabolismus MeSH
- glyceridy chemie MeSH
- hydrolýza MeSH
- kapalné krystaly chemie MeSH
- molekulární modely MeSH
- prasata MeSH
- sodíko-draslíková ATPasa chemie metabolismus MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Although mutations in more than 90 genes are known to cause CMT, the underlying genetic cause of CMT remains unknown in more than 50% of affected individuals. The discovery of additional genes that harbor CMT2-causing mutations increasingly depends on sharing sequence data on a global level. In this way-by combining data from seven countries on four continents-we were able to define mutations in ATP1A1, which encodes the alpha1 subunit of the Na+,K+-ATPase, as a cause of autosomal-dominant CMT2. Seven missense changes were identified that segregated within individual pedigrees: c.143T>G (p.Leu48Arg), c.1775T>C (p.Ile592Thr), c.1789G>A (p.Ala597Thr), c.1801_1802delinsTT (p.Asp601Phe), c.1798C>G (p.Pro600Ala), c.1798C>A (p.Pro600Thr), and c.2432A>C (p.Asp811Ala). Immunostaining peripheral nerve axons localized ATP1A1 to the axolemma of myelinated sensory and motor axons and to Schmidt-Lanterman incisures of myelin sheaths. Two-electrode voltage clamp measurements on Xenopus oocytes demonstrated significant reduction in Na+ current activity in some, but not all, ouabain-insensitive ATP1A1 mutants, suggesting a loss-of-function defect of the Na+,K+ pump. Five mutants fall into a remarkably narrow motif within the helical linker region that couples the nucleotide-binding and phosphorylation domains. These findings identify a CMT pathway and a potential target for therapy development in degenerative diseases of peripheral nerve axons.
- MeSH
- Charcotova-Marieova-Toothova nemoc genetika MeSH
- dítě MeSH
- dominantní geny * MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- mutace genetika MeSH
- rodina MeSH
- rodokmen MeSH
- sekvence aminokyselin MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- sodíko-draslíková ATPasa chemie genetika MeSH
- Check Tag
- dítě MeSH
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Na(+)/K(+)-ATPase (NKA) is an enzyme of crucial importance for all animal cells. We examined the inhibitory effects of halogenated phenylquinolinones on NKA. The 5,6,7,8-tetrafluoro-3-hydroxy-2-phenylquinolin-4(1H)-one (TFHPQ) was identified as an efficient NKA inhibitor with IC50 near 10 μM. The inhibition by TFHPQ is particularly efficient at higher concentrations of K(+), where NKA adopts the E2 conformation. The experimental observations are in a good agreement with the outcomes from molecular docking. We identified an energetically favourable TFHPQ binding site for the K(+)-bound NKA, which is located in the proximity of the cytoplasmic C-terminus.
- MeSH
- chinolony chemie farmakologie MeSH
- inhibitory enzymů chemie farmakologie MeSH
- prasata metabolismus MeSH
- simulace molekulového dockingu * MeSH
- sodíko-draslíková ATPasa antagonisté a inhibitory chemie metabolismus MeSH
- terciární struktura proteinů MeSH
- vazebná místa MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Proteins are subject to oxidative modification and the formation of adducts with a broad spectrum of reactive species via enzymatic and non-enzymatic mechanisms. Here we report that in vitro non-enzymatic methylglyoxal (MGO) binding causes the inhibition and formation of MGO advanced glycation end-products (MAGEs) in Na+/K+-ATPase (NKA). Concretely, MGO adducts with NKA amino acid residues (mainly Arg) and Nε-(carboxymethyl)lysine (CML) formation were found. MGO is not only an inhibitor for solubilized NKA (IC50=91±16μM), but also for reconstituted NKA in the lipid bilayer environment, which was clearly demonstrated using a DPPC/DPPE liposome model in the presence or absence of the NKA-selective inhibitor ouabain. High-resolution mass spectrometric analysis of a tryptic digest of NKA isolated from pig (Sus scrofa) kidney indicates that the intracellular α-subunit is naturally (post-translationally) modified by MGO in vivo. In contrast to this, the β-subunit could only be modified by MGO artificially, and the transmembrane part of the protein did not undergo MGO binding under the experimental setup used. As with bovine serum albumin, serving as the water-soluble model, we also demonstrated a high binding capacity of MGO to water-poorly soluble NKA using a multi-spectral methodology based on electroanalytical, immunochemical and fluorimetric tools. In addition, a partial suppression of the MGO-mediated inhibitory effect could be observed in the presence of aminoguanidine (pimagedine), a glycation suppressor and MGO-scavenger. All the results here were obtained with the X-ray structure of NKA in the E1 conformation (3WGV) and could be used in the further interpretation of the functionality of this key enzyme in the presence of highly-reactive metabolic side-products, glycation agents and generally under oxidative stress conditions.
- MeSH
- guanidiny farmakologie MeSH
- hmotnostní spektrometrie MeSH
- konformace proteinů MeSH
- krystalografie rentgenová MeSH
- ledviny metabolismus MeSH
- ouabain farmakologie MeSH
- oxidační stres MeSH
- produkty pokročilé glykace chemie metabolismus MeSH
- pyruvaldehyd chemie metabolismus MeSH
- sérový albumin hovězí metabolismus MeSH
- skot MeSH
- sodíko-draslíková ATPasa antagonisté a inhibitory chemie metabolismus MeSH
- Sus scrofa MeSH
- vazba proteinů MeSH
- zvířata MeSH
- Check Tag
- skot MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Na(+)/K(+)-ATPase (NKA) is an essential cation pump protein responsible for the maintenance of the sodium and potassium gradients across the plasma membrane. Recently published high-resolution structures revealed amino acids forming the cation binding sites (CBS) in the transmembrane domain and variable position of the domains in the cytoplasmic headpiece. Here we report molecular dynamic simulations of the human NKA α1β1 isoform embedded into DOPC bilayer. We have analyzed the NKA conformational changes in the presence of Na(+)- or K(+)-cations in the CBS, for various combinations of the cytoplasmic ligands, and the two major enzyme conformations in the 100 ns runs (more than 2.5 μs of simulations in total). We identified two novel cytoplasmic pathways along the pairs of transmembrane helices TM3/TM7 or TM6/TM9 that allow hydration of the CBS or transport of cations from/to the bulk. These findings can provide a structural explanation for previous mutagenesis studies, where mutation of residues that are distal from the CBS resulted in the alteration of the enzyme affinity to the transported cations or change in the enzyme activity.
- MeSH
- draslík metabolismus MeSH
- fosfatidylcholiny metabolismus MeSH
- kationty metabolismus MeSH
- konformace proteinů MeSH
- lidé MeSH
- lipidové dvojvrstvy metabolismus MeSH
- simulace molekulární dynamiky MeSH
- sodík metabolismus MeSH
- sodíko-draslíková ATPasa chemie metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Cisplatin is the most widely used chemotherapeutics for cancer treatment, however, its administration is connected to inevitable adverse effects. Previous studies suggested that cisplatin is able to inhibit Na(+)/K(+)-ATPase (NKA), the enzyme responsible for maintaining electrochemical potential and sodium gradient across the plasma membrane. Here we report a crystallographic analysis of cisplatin bound to NKA in the ouabain bound E2P form. Despite a moderate resolution (7.4 Å and 7.9 Å), the anomalous scattering from platinum and a model representation from a recently published structure enabled localization of seven cisplatin binding sites by anomalous difference Fourier maps. Comparison with NKA structures in the E1P conformation suggested two possible inhibitory mechanisms for cisplatin. Binding to Met151 can block the N-terminal pathway for transported cations, while binding to Met171 can hinder the interaction of cytoplasmic domains during the catalytic cycle.
- MeSH
- cisplatina škodlivé účinky chemie metabolismus MeSH
- konformace proteinů MeSH
- krystalografie rentgenová MeSH
- methionin chemie metabolismus MeSH
- molekulární modely MeSH
- ouabain chemie MeSH
- sodíko-draslíková ATPasa antagonisté a inhibitory chemie metabolismus MeSH
- terciární struktura proteinů MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
AIMS: Cisplatin is a widely used chemotherapeutic. However, it is associated with numerous adverse effects. The aim of our study was examination of cisplatin interaction with Na(+)/K(+)-ATPase (NKA, the sodium pump). This enzyme is of crucial importance for all animal cells and particularly for the kidney, which is frequently damaged during chemotherapy. METHODS: The entire NKA was isolated from porcine kidney. Its large cytoplasmic segment connecting transmembrane helices 4 and 5 (C45), was heterologously expressed in E.coli (wild-type or C367S mutant). The ATPase activity was evaluated according to the inorganic phosphate production and the interaction of isolated C45 with cisplatin was studied using chronopotentiometry and mass spectrometry. RESULTS: Our experiments revealed that cisplatin can inhibit NKA. The finding that other platinum-based drugs with a low nephrotoxicity, carboplatin and oxaliplatin, did not inhibit NKA, suggested that NKA/cisplatin interaction is an important factor in cisplatin adverse effects. The inhibitory effect of cisplatin could be prevented by preincubation of the enzyme with reduced glutathione or DTT. Using chronopotentiometry and mass spectrometry, we found that cisplatin is bound to C45. However, our mutagenesis experiment did not confirm that the suggested Cys367 could be the binding site for cisplatin. CONCLUSION: Unintended interactions of drugs present serious limitations to treatment success. Although a large number of membrane pumps have been identified as potential targets of cisplatin, vis-a-vis nephrotoxicity, NKA inhibition seems to be of crucial importance. Experiments with isolated large cytoplasmic segment C45 revealed that it is the main target of cisplatin on NKA and that the reaction with cysteine residues plays an important role in cisplatin/NKA interactions. However, further experiments must be performed to identify the interacting amino acid residues more precisely.
- MeSH
- cisplatina škodlivé účinky chemie farmakologie MeSH
- ledviny enzymologie MeSH
- prasata MeSH
- protinádorové látky škodlivé účinky chemie farmakologie MeSH
- sodíko-draslíková ATPasa antagonisté a inhibitory chemie MeSH
- spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Combination of fluorescence techniques and molecular docking was used to monitor interaction of Na,K-ATPase and its large cytoplasmic loop connecting fourth and fifth transmembrane helices (C45) with fluorone dyes (i.e. eosin Y, 5(6)-carboxyeosin, rose bengal, fluorescein, and erythrosine B). Our data suggested that there are at least two binding sites for all used fluorone dyes, except of 5(6)-carboxyeosin. The first binding site is located on C45 loop, and it is sensitive to the presence of nucleotide. The other site is located on the extracellular part of the enzyme, and it is sensitive to the presence of Na(+) or K(+) ions. The molecular docking revealed that in the open conformation of C45 loop (which is obtained in the presence of ATP) all used fluorone dyes occupy position directly inside the ATP-binding pocket, while in the closed conformation (i.e. in the absence of any ligand) they are located only near the ATP-binding site depending on their different sizes. On the extracellular part of the protein, the molecular docking predicts two possible binding sites with similar binding energy near Asp897(α) or Gln69(β). The former was identified as a part of interaction site between α- and β-subunits, the latter is in contact with conserved FXYD sequence of the γ-subunit. Our findings provide structural explanation for numerous older studies, which were performed with fluorone dyes before the high-resolution structures were known. Further, fluorone dyes seem to be good probes for monitoring of intersubunit interactions influenced by Na(+) and K(+) binding.
- MeSH
- adenosintrifosfát chemie MeSH
- červeň bengálská chemie MeSH
- chemické modely MeSH
- cytoplazma metabolismus MeSH
- draslík chemie MeSH
- eosin chemie MeSH
- erythrosin chemie MeSH
- Escherichia coli metabolismus MeSH
- fluorescein chemie MeSH
- fluoresceiny chemie farmakologie MeSH
- fluorescenční barviva farmakologie MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární konformace MeSH
- sodík chemie MeSH
- sodíko-draslíková ATPasa chemie MeSH
- terciární struktura proteinů MeSH
- vazebná místa MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The effects of sanguinarine (SG) and its metabolite dihydrosanguinarine (DHSG) on Na(+)/K(+)-ATPase were investigated using fluorescence spectroscopy. The results showed that the enzyme in E1 conformation can bind both charged and neutral (pseudobase) forms of SG with a K(D)=7.2+/-2.0 microM or 11.7+/-0.9 microM, while the enzyme in E2 conformation binds only the charged form of SG with a K(D)=4.7+/-1.1 microM. Fluorescence quenching experiments suggest that the binding site in E1 conformation is located on the surface of the enzyme for both forms but the binding site in E2 conformation is protected from the solvent. We found no evidence for interaction of Na(+)/K(+)-ATPase and DHSG. This implies that any in vivo effect of SG attributable to inhibition of Na(+)/K(+)-ATPase can be considered only prior to SG-->DHSG transformation in the gastro-intestinal tract and/or blood. Hence, Na(+)/K(+)-ATPase inhibition will be effective in SG topical application but its duration will be very limited in SG oral or parenteral administration.
