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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 PMCID: PMC11193536 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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Yoneda JS, Sebinelli HG, Itri R, Ciancaglini P. Overview on solubilization and lipid reconstitution of Na,K-ATPase: enzyme kinetic and biophysical characterization. Biophys Rev 2020; 12:49-64. [PMID: 31955383 DOI: 10.1007/s12551-020-00616-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 01/07/2020] [Indexed: 12/11/2022] Open
Abstract
Na,K-ATPase is a membrane protein which plays a vital role. It pumps Na+ and K+ ions across the cellular membranes using energy from ATP hydrolysis, and is responsible for maintaining the osmotic equilibrium and generating the membrane potential. Moreover, Na,K-ATPase has also been involved in cell signaling, interacting with partner proteins. Cardiotonic steroids bind specifically to Na,K-ATPase triggering a number of signaling pathways. Because of its importance, many efforts have been employed to study the structure and function of this protein. Difficulties associated with its removal from natural membranes and the concomitant search for appropriate replacement conditions to keep the protein in solution have presented a challenge that had to be overcome prior to carrying out biophysical and biochemical studies in vitro. In this review, we summarized all of the methods and techniques applied by our group in order to obtain information about Na,K-ATPase in respect to solubilization, reconstitution into mimetic system, influence of lipid composition, stability, oligomerization, and aggregation.
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Affiliation(s)
- Juliana Sakamoto Yoneda
- Instituto de Fisica, Universidade de Sao Paulo, Rua do Matao, 1371, 05508-090, Sao Paulo, SP, Brazil.
| | - Heitor Gobbi Sebinelli
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto da Universidade de São Paulo (FFCLRP-USP), Ribeirão Preto, SP, 14040-901, Brazil
| | - Rosangela Itri
- Instituto de Fisica, Universidade de Sao Paulo, Rua do Matao, 1371, 05508-090, Sao Paulo, SP, Brazil
| | - Pietro Ciancaglini
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto da Universidade de São Paulo (FFCLRP-USP), Ribeirão Preto, SP, 14040-901, Brazil
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Yoneda JS, Scanavachi G, Sebinelli HG, Borges JC, Barbosa LRS, Ciancaglini P, Itri R. Multimeric species in equilibrium in detergent-solubilized Na,K-ATPase. Int J Biol Macromol 2016; 89:238-45. [PMID: 27109755 DOI: 10.1016/j.ijbiomac.2016.04.058] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 04/19/2016] [Accepted: 04/20/2016] [Indexed: 12/29/2022]
Abstract
In this work, we find an equilibrium between different Na,K-ATPase (NKA) oligomeric species solubilized in a non-ionic detergent C12E8 by means of Dynamic Light Scattering (DLS), Analytical Ultracentrifugation (AUC), Small Angle X-ray Scattering (SAXS), Spectrophotometry (absorption at 280/350nm) and enzymatic activity assay. The NKA sample after chromatography purification presented seven different populations as identified by AUC, with monomers and tetramers amounting to ∼55% of the total protein mass in solution. These two species constituted less than 40% of the total protein mass after increasing the NKA concentration. Removal of higher-order oligomer/aggregate species from the NKA solution using 220nm-pore filter resulted in an increase of the specific enzymatic activity. Nevertheless, the enzyme forms new large aggregates over an elapsed time of 20h. The results thus point out that C12E8-solubilized NKA is in a dynamic equilibrium of monomers, tetramers and high-order oligomers/subunit aggregates. These latter have low or null activity. High amount of detergent leads to the dissociation of NKA into smaller aggregates with no enzymatic activity.
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Affiliation(s)
- Juliana Sakamoto Yoneda
- Instituto de Física da Universidade de São Paulo, IF USP, 05508-090 São Paulo, Brazil; Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, FFCLRP USP, 14040-901 Ribeirão Preto, SP, Brazil
| | - Gustavo Scanavachi
- Instituto de Física da Universidade de São Paulo, IF USP, 05508-090 São Paulo, Brazil
| | - Heitor Gobbi Sebinelli
- Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, FFCLRP USP, 14040-901 Ribeirão Preto, SP, Brazil
| | - Júlio Cesar Borges
- Instituto de Química de São Carlos, IQSC-USP, 13560-970 São Carlos, SP, Brazil
| | - Leandro R S Barbosa
- Instituto de Física da Universidade de São Paulo, IF USP, 05508-090 São Paulo, Brazil
| | - Pietro Ciancaglini
- Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, FFCLRP USP, 14040-901 Ribeirão Preto, SP, Brazil
| | - Rosangela Itri
- Instituto de Física da Universidade de São Paulo, IF USP, 05508-090 São Paulo, Brazil.
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Dach I, Olesen C, Signor L, Nissen P, le Maire M, Møller JV, Ebel C. Active detergent-solubilized H+,K+-ATPase is a monomer. J Biol Chem 2012; 287:41963-78. [PMID: 23055529 DOI: 10.1074/jbc.m112.398768] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The H(+),K(+)-ATPase pumps protons or hydronium ions and is responsible for the acidification of the gastric fluid. It is made up of an α-catalytic and a β-glycosylated subunit. The relation between cation translocation and the organization of the protein in the membrane are not well understood. We describe here how pure and functionally active pig gastric H(+),K(+)-ATPase with an apparent Stokes radius of 6.3 nm can be obtained after solubilization with the non-ionic detergent C(12)E(8), followed by exchange of C(12)E(8) with Tween 20 on a Superose 6 column. Mass spectroscopy indicates that the β-subunit bears an excess mass of 9 kDa attributable to glycosylation. From chemical analysis, there are 0.25 g of phospholipids and around 0.024 g of cholesterol bound per g of protein. Analytical ultracentrifugation shows one main complex, sedimenting at s(20,)(w) = 7.2 ± 0.1 S, together with minor amounts of irreversibly aggregated material. From these data, a buoyant molecular mass is calculated, corresponding to an H(+),K(+)-ATPase α,β-protomer of 147.3 kDa. Complementary sedimentation velocity with deuterated water gives a picture of an α,β-protomer with 0.9-1.4 g/g of bound detergent and lipids and a reasonable frictional ratio of 1.5, corresponding to a Stokes radius of 7.1 nm. An α(2),β(2) dimer is rejected by the data. Light scattering coupled to gel filtration confirms the monomeric state of solubilized H(+),K(+)-ATPase. Thus, α,β H(+),K(+)-ATPase is active at least in detergent and may plausibly function as a monomer, as has been established for other P-type ATPases, Ca(2+)-ATPase and Na(+),K(+)-ATPase.
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Affiliation(s)
- Ingrid Dach
- Center for Membrane Pumps in Cells and Diseases, Danish Research Foundation, DK-8000 Aarhus, Denmark
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Liu L, Ivanov AV, Gable ME, Jolivel F, Morrill GA, Askari A. Comparative properties of caveolar and noncaveolar preparations of kidney Na+/K+-ATPase. Biochemistry 2011; 50:8664-73. [PMID: 21905705 PMCID: PMC3186040 DOI: 10.1021/bi2009008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
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To evaluate previously proposed functions of renal caveolar
Na+/K+-ATPase, we modified the standard procedures
for the preparation of the purified membrane-bound kidney enzyme,
separated the caveolar and noncaveolar pools, and compared their properties.
While the subunits of Na+/K+-ATPase (α,β,γ)
constituted most of the protein content of the noncaveolar pool, the
caveolar pool also contained caveolins and major caveolar proteins
annexin-2 tetramer and E-cadherin. Ouabain-sensitive Na+/K+-ATPase activities of the two pools had similar properties
and equal molar activities, indicating that the caveolar enzyme retains
its ion transport function and does not contain nonpumping enzyme.
As minor constituents, both caveolar and noncaveolar pools also contained
Src, EGFR, PI3K, and several other proteins known to be involved in
stimulous-induced signaling by Na+/K+-ATPase,
indicating that signaling function is not limited to the caveolar
pool. Endogenous Src was active in both pools but was not further
activated by ouabain, calling into question direct interaction of
Src with native Na+/K+-ATPase. Chemical cross-linking,
co-immunoprecipitation, and immunodetection studies showed that in
the caveolar pool, caveolin-1 oligomers, annexin-2 tetramers, and
oligomers of the α,β,γ-protomers of Na+/K+-ATPase form a large multiprotein complex. In conjunction
with known roles of E-cadherin and the β-subunit of Na+/K+-ATPase in cell adhesion and noted intercellular β,β-contacts
within the structure of Na+/K+-ATPase, our findings
suggest that interacting caveolar Na+/K+-ATPases
located at renal adherens junctions maintain contact of two adjacent
cells, conduct essential ion pumping, and are capable of locus-specific
signaling in junctional cells.
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Affiliation(s)
- Lijun Liu
- Department of Biochemistry and Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio 43614, United States
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Ochiai H, Takeda K, Soeda S, Tahara Y, Takenaka H, Abe K, Hayashi Y, Noguchi S, Inoue M, Schwarz S, Schwarz W, Kawamura M. Epigallocatechin-3-gallate is an inhibitor of Na+,K+-ATPase by favoring the E1 conformation. Biochem Pharmacol 2009; 78:1069-74. [DOI: 10.1016/j.bcp.2009.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/04/2009] [Accepted: 06/08/2009] [Indexed: 11/25/2022]
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Pilotelle-Bunner A, Matthews JM, Cornelius F, Apell HJ, Sebban P, Clarke RJ. ATP binding equilibria of the Na(+),K(+)-ATPase. Biochemistry 2009; 47:13103-14. [PMID: 19006328 DOI: 10.1021/bi801593g] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reported values of the dissociation constant, K(d), of ATP with the E1 conformation of the Na(+),K(+)-ATPase fall in two distinct ranges depending on how it is measured. Equilibrium binding studies yield values of 0.1-0.6 microM, whereas presteady-state kinetic studies yield values of 3-14 microM. It is unacceptable that K(d) varies with the experimental method of its determination. Using simulations of the expected equilibrium behavior for different binding models based on thermodynamic data obtained from isothermal titration calorimetry we show that this apparent discrepancy can be explained in part by the presence in presteady-state kinetic studies of excess Mg(2+) ions, which compete with the enzyme for the available ATP. Another important contributing factor is an inaccurate assumption in the majority of presteady-state kinetic studies of a rapid relaxation of the ATP binding reaction on the time scale of the subsequent phosphorylation. However, these two factors alone are insufficient to explain the previously observed presteady-state kinetic behavior. In addition one must assume that there are two E1-ATP binding equilibria. Because crystal structures of P-type ATPases indicate only a single bound ATP per alpha-subunit, the only explanation consistent with both crystal structural and kinetic data is that the enzyme exists as an (alphabeta)(2) diprotomer, with protein-protein interactions between adjacent alpha-subunits producing two ATP affinities. We propose that in equilibrium measurements the measured K(d) is due to binding of ATP to one alpha-subunit, whereas in presteady-state kinetic studies, the measured apparent K(d) is due to the binding of ATP to both alpha-subunits within the diprotomer.
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Mechanism of allosteric effects of ATP on the kinetics of P-type ATPases. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:3-17. [PMID: 19225774 DOI: 10.1007/s00249-009-0407-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 12/14/2008] [Accepted: 12/14/2008] [Indexed: 10/21/2022]
Abstract
The roles of allosteric effects of ATP and protein oligomerisation in the mechanisms of P-type ATPases belong to the most controversial and least well understood topics in the field. Recent crystal structural and kinetic data, however, now allow certain hypotheses to be definitely excluded and consistent hypotheses to be developed. The aim of this review is to critically discuss recent results and, in the light of them, to present a set of conclusions which could form the basis of future research. The major conclusions are: (1) at saturating ATP concentrations P-type ATPases function as monomeric enzymes, (2) the catalytic units of P-type ATPases only possess a single ATP binding site, (3) at non-saturating ATP concentrations P-type ATPases exist as diprotomeric (or higher oligomeric) complexes, (4) protein-protein interactions within a diprotomeric complex enhances the enzymes' ATP binding affinity, (5) ATP binding to both protomers within a diprotomeric complex causes it to dissociate into two separate monomers. The physiological role of protein-protein interactions within a diprotomer may be to enhance ATP binding affinity so as to scavenge ATP and maximize the ion pumping rate under hypoxic or anoxic conditions. For the first time a structural basis for the well-known ATP allosteric acceleration of the E2 --> E1 transition is presented. This is considered to be due to a minimization of steric hindrance between neighbouring protomers because of the ability of ATP to induce a compact conformation of the enzymes' cytoplasmic domains.
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