1
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Lev B, Chennath M, Cranfield CG, Cornelius F, Allen TW, Clarke RJ. Involvement of the alpha-subunit N-terminus in the mechanism of the Na +,K +-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119539. [PMID: 37479188 DOI: 10.1016/j.bbamcr.2023.119539] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/26/2023] [Accepted: 07/10/2023] [Indexed: 07/23/2023]
Abstract
Previous studies have shown that cytoplasmic K+ release and the associated E2 → E1 conformational change of the Na+,K+-ATPase is a major rate-determining step of the enzyme's ion pumping cycle and hence a prime site of acute regulatory intervention. From the ionic strength dependence of the enzyme's distribution between the E2 and E1 states, it has also been found that E2 is stabilized by an electrostatic attraction. Any disruption of this electrostatic attraction would, thus, have profound effects on the rate of ion pumping. The aim of this paper is to identify the location of this interaction. Using enhanced-sampling molecular dynamics simulations with a predicted N-terminal structure added to the X-ray crystal structure of the Na+,K+-ATPase, a previously postulated salt bridge between Lys32 and Glu233 (rat sequence numbering) of the enzyme's α-subunit can be excluded. The residues never approach closely enough to form a salt bridge. In contrast, strong interactions with anionic lipid head groups were seen. To investigate the possibility of a protein-lipid interaction experimentally, the surface charge density of Na+,K+-ATPase-containing membrane fragments was estimated from zeta potential measurements to be 0.019 (± 0.001) C m-2. This is in good agreement with the charge density previously determined to be responsible for stabilization of the E2 state of 0.023 (± 0.009) C m-2 and the membrane charge density estimated here from published electron-microscopic images of 0.018C m-2. The results are, therefore, consistent with an interaction of the Na+,K+-ATPase α-subunit N-terminus with negatively-charged lipid head groups of the neighbouring cytoplasmic membrane surface as the origin of the electrostatic interaction stabilising the E2 state.
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Affiliation(s)
- B Lev
- School of Science, RMIT University, Melbourne, Vic, 3001, Australia
| | - M Chennath
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - C G Cranfield
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - F Cornelius
- Department of Biomedicine, University of Aarhus, DK-8000 Aarhus, C, Denmark
| | - T W Allen
- School of Science, RMIT University, Melbourne, Vic, 3001, Australia
| | - R J Clarke
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, Sydney, NSW 2006, Australia.
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2
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Oda I, Danno D, Saigoh K, Wolf J, Kawashita N, Hirano M, Samukawa M, Kitamura S, Kikui S, Takeshima T, Mitsui Y, Kusunoki S, Nagai Y. Hemiplegic migraine type 2 with new mutation of the ATP1A2 gene in Japanese cases. Neurosci Res 2022; 180:83-89. [DOI: 10.1016/j.neures.2022.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 02/26/2022] [Accepted: 03/02/2022] [Indexed: 11/25/2022]
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3
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Petrushanko IY, Mitkevich VA, Makarov AA. Molecular Mechanisms of the Redox Regulation of the Na,K-ATPase. Biophysics (Nagoya-shi) 2020. [DOI: 10.1134/s0006350920050139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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4
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Poluektov YM, Dergousova EA, Lopina OD, Mitkevich VA, Makarov AA, Petrushanko IY. Na,K-ATPase α-subunit conformation determines glutathionylation efficiency. Biochem Biophys Res Commun 2019; 510:86-90. [PMID: 30661791 DOI: 10.1016/j.bbrc.2019.01.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Accepted: 01/09/2019] [Indexed: 10/27/2022]
Abstract
The functioning of the N, K-ATPase depends on the redox status of cells and its activity is inhibited by oxidative stress and hypoxia. We previously found that redox sensitivity of the Na,K-ATPase is mediated by glutathionylation of the α-subunit. An increase in the level of glutathionylation of cysteine residues in the Na,K-ATPase α-subunit under stressful conditions leads to a decrease in the activity of the enzyme and a change in its receptor function. The structure of the Na,K-ATPase undergoes significant conformational changes during functioning. The effects of enzyme conformation on its ability to undergo glutathionylation are not clear. Here we show that the highest level of glutathionylation in the α-subunit of Na,K-ATPase is achieved in the E1 (Na+-induced) conformation. The transition of the Na,K-ATPase to the E2 (K+-induced) conformation leads to a decrease in the efficiency of glutathionylation. The lowest efficiency of Na,K-ATPase glutathionylation was observed in the E2P and E2P ouabain states. According to molecular modelling data, the maximum number of cysteine residues available for glutathionylation are present in the E1P conformation. In the E2P conformation, the main functional cysteine residues (Cys204, Cys242, Cys452, and Cys456) are buried from the solvent, which makes them inaccessible for glutathionylation. Thus, the efficiency of α-subunit glutathionylation depends on enzyme conformation, which is altered by bound ligands and proteins. A shift in the E1/E2 equilibrium towards prevalence of E1 can lead to better access for the relevant ligands and proteins to the binding site located in the Na,K-ATPase α-subunit. Na,K-ATPase.
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Affiliation(s)
- Yuri M Poluektov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia; I.M. Sechenov First Moscow State Medical University, Ministry of Healthcare of the Russian Federation, Trubetskaya St. 8/2, 119991, Moscow, Russia
| | - Elena A Dergousova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia; Faculty of Biology, Lomonosov Moscow State University, Leninskie Gory, 1/12, Moscow, 119234, Russia
| | - Olga D Lopina
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia; Faculty of Biology, Lomonosov Moscow State University, Leninskie Gory, 1/12, Moscow, 119234, Russia
| | - Vladimir A Mitkevich
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia; Moscow Institute of Physics and Technology, 141700, Dolgoprudnyi, Moscow Region, Russia.
| | - Alexander A Makarov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia
| | - Irina Yu Petrushanko
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991, Moscow, Russia.
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5
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Leukemic stem cell signatures identify novel therapeutics targeting acute myeloid leukemia. Blood Cancer J 2018; 8:52. [PMID: 29921955 PMCID: PMC6889502 DOI: 10.1038/s41408-018-0087-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2017] [Revised: 03/01/2018] [Accepted: 04/03/2018] [Indexed: 12/18/2022] Open
Abstract
Therapy for acute myeloid leukemia (AML) involves intense cytotoxic treatment and yet approximately 70% of AML are refractory to initial therapy or eventually relapse. This is at least partially driven by the chemo-resistant nature of the leukemic stem cells (LSCs) that sustain the disease, and therefore novel anti-LSC therapies could decrease relapses and improve survival. We performed in silico analysis of highly prognostic human AML LSC gene expression signatures using existing datasets of drug–gene interactions to identify compounds predicted to target LSC gene programs. Filtering against compounds that would inhibit a hematopoietic stem cell (HSC) gene signature resulted in a list of 151 anti-LSC candidates. Using a novel in vitro LSC assay, we screened 84 candidate compounds at multiple doses and confirmed 14 drugs that effectively eliminate human AML LSCs. Three drug families presenting with multiple hits, namely antihistamines (astemizole and terfenadine), cardiac glycosides (strophanthidin, digoxin and ouabain) and glucocorticoids (budesonide, halcinonide and mometasone), were validated for their activity against human primary AML samples. Our study demonstrates the efficacy of combining computational analysis of stem cell gene expression signatures with in vitro screening to identify novel compounds that target the therapy-resistant LSC at the root of relapse in AML.
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6
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Petrushanko IY, Mitkevich VA, Anashkina AA, Klimanova EA, Dergousova EA, Lopina OD, Makarov AA. Critical role of γ-phosphate in structural transition of Na,K-ATPase upon ATP binding. Sci Rep 2014; 4:5165. [PMID: 24893715 PMCID: PMC4044624 DOI: 10.1038/srep05165] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 05/14/2014] [Indexed: 11/09/2022] Open
Abstract
Active transport of sodium and potassium ions by Na,K-ATPase is accompanied by the enzyme conformational transition between E1 and E2 states. ATP and ADP bind to Na,K-ATPase in the E1 conformation with similar affinity but the properties of enzyme in complexes with these nucleotides are different. We have studied thermodynamics of Na,K-ATPase binding with adenine nucleotides at different temperatures using isothermal titration calorimetry. Our data indicate that β-phosphate is involved in complex formation by increasing the affinity of adenine nucleotides to Na,K-ATPase by an order of magnitude, while γ-phosphate does not affect it. ATP binding to Na,K-ATPase in contrast to ADP binding generates a structural transition in the enzyme, which is consistent with the movement of a significant portion of the surface area to a solvent-protected state. We propose that ATP binding leads to convergence of the nucleotide-binding and phosphorylation domains transferring the enzyme from the "E1-open" to "E1-closed" conformation ready for phosphorylation.
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Affiliation(s)
- Irina Yu Petrushanko
- 1] Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991 Moscow, Russia [2]
| | - Vladimir A Mitkevich
- 1] Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991 Moscow, Russia [2]
| | - Anastasia A Anashkina
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991 Moscow, Russia
| | | | - Elena A Dergousova
- Faculty of Biology, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Olga D Lopina
- Faculty of Biology, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Alexander A Makarov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991 Moscow, Russia
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7
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Garcia A, Rasmussen HH, Apell HJ, Clarke RJ. Kinetic comparisons of heart and kidney Na+,K(+)-ATPases. Biophys J 2013; 103:677-88. [PMID: 22947929 DOI: 10.1016/j.bpj.2012.07.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/17/2012] [Accepted: 07/23/2012] [Indexed: 10/28/2022] Open
Abstract
Most kinetic measurements of the partial reactions of Na(+),K(+)-ATPase have been conducted on enzyme from mammalian kidney. Here we present a kinetic model that is based on the available equilibrium and kinetic parameters of purified kidney enzyme, and allows predictions of its steady-state turnover and pump current in intact cells as a function of ion and ATP concentrations and the membrane voltage. Using this model, we calculated the expected dependence of the pump current on voltage and extracellular Na(+) concentration. The simulations indicate a lower voltage dependence at negative potentials of the kidney enzyme in comparison with heart muscle Na(+),K(+)-ATPase, in agreement with experimental results. The voltage dependence is enhanced at high extracellular Na(+) concentrations. This effect can be explained by a voltage-dependent depopulation of extracellular K(+) ion binding sites on the E2P state and an increase in the proportion of enzyme in the E1P(Na(+))(3) state in the steady state. This causes a decrease in the effective rate constant for occlusion of K(+) by the E2P state and hence a drop in turnover. Around a membrane potential of zero, negligible voltage dependence is observed because the voltage-independent E2(K(+))(2) → E1 + 2K(+) transition is the major rate-determining step.
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Affiliation(s)
- Alvaro Garcia
- Department of Cardiology, Royal North Shore Hospital, and Kolling Institute, University of Sydney, Sydney, Australia
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8
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Petrushanko IY, Mitkevich VA, Borzova VA, Yakushev SS, Lopina OD, Makarov AA. Different domain organization of two main conformational states of Na+/K+-ATPase. Biophysics (Nagoya-shi) 2009. [DOI: 10.1134/s0006350909060050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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9
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Abstract
Cardiac glycosides are a diverse family of naturally derived compounds that bind to and inhibit Na+/K+-ATPase. Members of this family have been in clinical use for many years for the treatment of heart failure and atrial arrhythmia, and the mechanism of their positive inotropic effect is well characterized. Exciting recent findings have suggested additional signalling modes of action of Na+/K+-ATPase, implicating cardiac glycosides in the regulation of several important cellular processes and highlighting potential new therapeutic roles for these compounds in various diseases. Perhaps most notably, the increased susceptibility of cancer cells to these compounds supports their potential use as cancer therapies, and the first generation of glycoside-based anticancer drugs are currently in clinical trials.
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10
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Tonelli A, Gallanti A, Bersano A, Cardin V, Ballabio E, Airoldi G, Redaelli F, Candelise L, Bresolin N, Bassi MT. Amino acid changes in the amino terminus of the Na,K-adenosine triphosphatase alpha-2 subunit associated to familial and sporadic hemiplegic migraine. Clin Genet 2007; 72:517-23. [PMID: 17877748 DOI: 10.1111/j.1399-0004.2007.00892.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura inherited with an autosomal dominant pattern. Here, we report the genetic analysis of four families and one sporadic case with hemiplegic migraine (HM) in whom we searched for mutations in the three genes associated with the disease CACNA1A, ATP1A2 and SCN1A. Two novel amino acid changes p.Arg65Trp and p.Tyr9Asn, in the Na,K-adenosine triphosphatase (ATPase) alpha-2 subunit encoded by the ATP1A2 gene, were found in one FHM family and in the sporadic case, respectively. These mutations are peculiar for their location in the extreme N-terminus, an uncommon mutation target in this protein. Low frequency of migraine attacks in all our mutant patients with low complexity of the associated aura symptoms in the sporadic case is also observed. Besides the two novel mutations, the data here reported confirm the involvement of ATP1A2 gene in the sporadic form of HM, while the negative results on the other families tested for all genes known in HM strengthen the hypothesis of the existence of at least another locus involved in FHM.
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Affiliation(s)
- A Tonelli
- IRCCS E. Medea, Laboratory of Molecular Biology, Bosisio Parini Lecco, Italy
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11
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Zhang S, Malmersjö S, Li J, Ando H, Aizman O, Uhlén P, Mikoshiba K, Aperia A. Distinct Role of the N-terminal Tail of the Na,K-ATPase Catalytic Subunit as a Signal Transducer. J Biol Chem 2006; 281:21954-21962. [PMID: 16723354 DOI: 10.1074/jbc.m601578200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mounting evidence suggests that the ion pump, Na,K-ATPase, can, in the presence of ouabain, act as a signal transducer. A prominent binding motif linking the Na,K-ATPase to intracellular signaling effectors has, however, not yet been identified. Here we report that the N-terminal tail of the Na,K-ATPase catalytic alpha-subunit (alphaNT-t) binds directly to the N terminus of the inositol 1,4,5-trisphosphate receptor. Three amino acid residues, LKK, conserved in most species and most alpha-isoforms, are essential for the binding to occur. In wild-type cells, low concentrations of ouabain trigger low frequency calcium oscillations that activate NF-kappaB and protect from apoptosis. All of these effects are suppressed in cells overexpressing a peptide corresponding to alphaNT-t but not in cells overexpressing a peptide corresponding to alphaNT-t deltaLKK. Thus we have identified a well conserved Na,K-ATPase motif that binds to the inositol 1,4,5-trisphosphate receptor and can trigger an anti-apoptotic calcium signal.
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Affiliation(s)
- Songbai Zhang
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden; Division of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Seth Malmersjö
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden
| | - Juan Li
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden
| | - Hideaki Ando
- Division of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan; Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Oleg Aizman
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden
| | - Per Uhlén
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden
| | - Katsuhiko Mikoshiba
- Division of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan; Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Anita Aperia
- Department of Woman and Child Health, Karolinska Institutet, Astrid Lindgren Children's Hospital, Q2:09, SE-171 76 Stockholm, Sweden.
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12
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Zouzoulas A, Blostein R. Regions of the Catalytic α Subunit of Na,K-ATPase Important for Functional Interactions with FXYD 2. J Biol Chem 2006; 281:8539-44. [PMID: 16446368 DOI: 10.1074/jbc.m512700200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma modulator (FXYD 2) is a member of the FXYD family of single transmembrane proteins that modulate the kinetic behavior of Na,K-ATPase. This study concerns the identification of regions in the alpha subunit that are important for its functional interaction with gamma. An important effect of gamma is to increase K+ antagonism of cytoplasmic Na+ activation apparent as an increase in KNa' at high [K+]. We show that although gamma associates with alpha1, alpha2, and alpha3 isoforms, it increases the KNa' of alpha1 and alpha3 but not alpha2. Accordingly, chimeras of alpha1 and alpha2 were used to identify regions of alpha critical for the increased KNa'. As with alpha1 and alpha2, all chimeras associate with gamma. Kinetic analysis of alpha2front/alpha1back chimeras indicate that the C-terminal (Lys907-Tyr1018) region of alpha1, which includes transmembrane (TM)9 close to gamma, is important for the increase in KNa'. However, similar experiments with alpha1front/alpha2back chimeras indicate a modulatory role of the loop between TMs 7 and 8. Thus, as long as the alpha1 L7/8 loop is present, replacement of TM9 of alpha1 with that of alpha2 does not abrogate the gamma effect on KNa'. In contrast, as long as TM9 is that of alpha1, replacement of L7/8 of alpha1 with that of alpha2 does not abolish the effect. It is suggested that structural association of the TM regions of alpha and FXYD 2 is not the sole determinant of this effect of FXYD on KNa' but is subject to long range modulation by the extramembranous L7/8 loop of alpha.
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Affiliation(s)
- Athina Zouzoulas
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1A4, Canada
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13
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Abstract
The Na,K-pump was discovered about 50 years ago. Since then there has been a methodic investigation of its structure and functional characteristics. The development of the Albers-Post model for the transport cycle was a milestone that provided the framework for detailed understanding of the transport process. The pump is composed of 2 subunits that exist in the membrane as an alphabeta heterodimer. All known enzymatic functions of the pump occur through the alpha subunit. Although necessary for activity, the complete role of the beta subunit is not understood fully. Numerous studies have established that the alphabeta protomer is the minimal functional unit needed to perform the Albers-Post reaction cycle. However, higher orders of aggregation [(alphabeta)n] are commonly detected. There is little evidence that oligomerization has functional consequence for ion transport. The Na+,K+-adenosine triphosphatase (ATPase) is a member of the P-type ATPase family of transporters. Proteins within this family have common amino acid sequence motifs that share functional characteristics and structure. Low-resolution 3-dimensional reconstruction of 2-dimensional crystal diffractions provide evidence for the similarity in tertiary structure of the alpha subunit and the Ca2+ATPase (a closely related P-type ATPase). The spatial location of the beta subunit also is obvious in these reconstructions. Recent high-resolution reconstructions from 3-dimensional crystals of the Ca2+ATPase provide structural details at the atomic level. It now is possible to interpret structurally some of the key steps in the Albers-Post reaction. Some of these high-resolution interpretations are translatable to the Na+,K+-ATPase, but a high-resolution structure of the Na,K-pump is needed for the necessary details of those aspects that are unique to this transporter.
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Affiliation(s)
- Dwight W Martin
- Division of Hematology, Stony Brook University, Stony Brook, NY 11794-8151, USA.
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14
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Cornelius F, Mahmmoud YA, Meischke L, Cramb G. Functional Significance of the Shark Na,K-ATPase N-Terminal Domain. Is the Structurally Variable N-Terminus Involved in Tissue-Specific Regulation by FXYD Proteins? Biochemistry 2005; 44:13051-62. [PMID: 16185073 DOI: 10.1021/bi0504456] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The proteolytic profile after mild controlled trypsin cleavage of shark rectal gland Na,K-ATPase was characterized and compared to that of pig kidney Na,K-ATPase, and conditions for achieving N-terminal cleavage of the alpha-subunit at the T(2) trypsin cleavage site were established. Using such conditions, the shark enzyme N-terminus was much more susceptible to proteolysis than the pig enzyme. Nevertheless, the maximum hydrolytic activity was almost unaffected for the shark enzyme, whereas it was significantly decreased for the pig kidney enzyme. The apparent ATP affinity was unchanged for shark but increased for pig enzyme after N-terminal truncation. The main common effect following N-terminal truncation of shark and pig Na,K-ATPase is a shift in the E(1)-E(2) conformational equilibrium toward E(1). The phosphorylation and the main rate-limiting E(2) --> E(1) step are both accelerated after N-terminal truncation of the shark enzyme, but decreased significantly in the pig kidney enzyme. Some of the kinetic differences, like the acceleration of the phosphorylation reaction, following N-terminal truncation of the two preparations may be due to the fact that under the conditions used for N-terminal truncation, the C-terminal domain of the FXYD regulatory protein of the shark enzyme, PLMS or FXYD10, was also cleaved, whereas the gamma or FXYD2 of the pig enzyme was not. In the shark enzyme, N-terminal truncation of the alpha-subunit abolished association of exogenous PLMS with the alpha-subunit and the functional interactions were abrogated. Moreover, PKC phosphorylation of the preparation, which relieves PLMS inhibition of Na,K-ATPase activity, exposed the N-terminal trypsin cleavage site. It is suggested that PLMS interacts functionally with the N-terminus of the shark Na,K-ATPase to control the E(1)-E(2) conformational transition of the enzyme and that such interactions may be controlled by regulatory protein kinase phosphorylation of the N-terminus. Such interactions are likely in shark enzyme where PLMS has been demonstrated by cross-linking to associate with the Na,K-ATPase A-domain.
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Affiliation(s)
- Flemming Cornelius
- Department of Biophysics, University of Aarhus, Ole Worms Allé 185, DK-8000 Aarhus C, Denmark.
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15
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Kaunisto MA, Harno H, Vanmolkot KRJ, Gargus JJ, Sun G, Hämäläinen E, Liukkonen E, Kallela M, van den Maagdenberg AMJM, Frants RR, Färkkilä M, Palotie A, Wessman M. A novel missense ATP1A2 mutation in a Finnish family with familial hemiplegic migraine type 2. Neurogenetics 2004; 5:141-6. [PMID: 15133718 DOI: 10.1007/s10048-004-0178-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Accepted: 03/25/2004] [Indexed: 10/26/2022]
Abstract
Familial hemiplegic migraine (FHM), a rare autosomal dominant subtype of migraine with aura, has been linked to two chromosomal loci, 19p13 and 1q23. Mutations in the Na+K+-ATPase alpha2 subunit gene, ATP1A2, on 1q23 have recently been shown to cause familial hemiplegic migraine type 2 (FHM2). We sequenced the coding regions of this gene in a Finnish chromosome 1q23-linked FHM family with associated symptoms such as coma and identified a novel A1033G mutation in exon 9. This mutation results in a threonine-to-alanine substitution at codon 345. This residue is located in a highly conserved N-terminal region of the M4-5 loop of the Na+,K+-ATPase. Furthermore, the T345A mutation co-segregated with the disorder in our family and was not present in 132 healthy Finnish control individuals. For these reasons it is most likely the FHM-causing mutation in this family.
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Affiliation(s)
- M A Kaunisto
- Biomedicum Helsinki, Research Program in Molecular Medicine, University of Helsinki, Helsinki, Finland.
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16
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Lowe J, Araujo GMN, Pedrenho AR, Nunes-Tavares N, Ribeiro MGL, Hassón-Voloch A. Polarized distribution of Na+, K+-ATPase α-subunit isoforms in electrocyte membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1661:40-6. [PMID: 14967473 DOI: 10.1016/j.bbamem.2003.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Revised: 11/20/2003] [Accepted: 11/24/2003] [Indexed: 11/17/2022]
Abstract
We have previously demonstrated that Na+, K(+)-ATPase activity is present in both differentiated plasma membranes from Electrophorus electricus (L.) electrocyte. Considering that the alpha subunit is responsible for the catalytic properties of the enzyme, the aim of this work was to study the presence and localization of alpha isoforms (alpha1 and alpha2) in the electrocyte. Dose-response curves showed that non-innervated membranes present a Na+, K(+)-ATPase activity 2.6-fold more sensitive to ouabain (I50=1.0+/-0.1 microM) than the activity of innervated membranes (I50=2.6+/-0.2 microM). As depicted in [3H]ouabain binding experiments, when the [3H]ouabain-enzyme complex was incubated in a medium containing unlabeled ouabain, reversal of binding occurred differently: the bound inhibitor dissociated 32% from Na+, K(+)-ATPase in non-innervated membrane fractions within 1 h, while about 50% of the ouabain bound to the enzyme in innervated membrane fractions was released in the same time. These data are consistent with the distribution of alpha1 and alpha2 isoforms, restricted to the innervated and non-innervated membrane faces, respectively, as demonstrated by Western blotting from membrane fractions and immunohistochemical analysis of the main electric organ. The results provide direct evidence for a distinct distribution of Na+, K(+)-ATPase alpha-subunit isoforms in the differentiated membrane faces of the electrocyte, a characteristic not yet described for any polarized cell.
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Affiliation(s)
- J Lowe
- Laboratório de Físico Química-Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, 21949-590, Rio de Janeiro, RJ, Brazil.
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Segall L, Lane LK, Blostein R. Insights into the structural basis for modulation of E1<-->E2 transitions by cytoplasmic domains of the Na,K-ATPase alpha subunit. Ann N Y Acad Sci 2003; 986:58-62. [PMID: 12763775 DOI: 10.1111/j.1749-6632.2003.tb07139.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Laura Segall
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6
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