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Ygberg S, Akkuratov EE, Howard RJ, Taylan F, Jans DC, Mahato DR, Katz A, Kinoshita PF, Portal B, Nennesmo I, Lindskog M, Karlish SJD, Andersson M, Lindstrand A, Brismar H, Aperia A. A missense mutation converts the Na +,K +-ATPase into an ion channel and causes therapy-resistant epilepsy. J Biol Chem 2021; 297:101355. [PMID: 34717959 PMCID: PMC8637647 DOI: 10.1016/j.jbc.2021.101355] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 10/14/2021] [Accepted: 10/25/2021] [Indexed: 11/16/2022] Open
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.
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Affiliation(s)
- Sofia Ygberg
- Neuropediatric Unit, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Centre for Inherited Metabolic Diseases (CMMS), Karolinska University Hospital, Stockholm, Sweden
| | - Evgeny E Akkuratov
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Rebecca J Howard
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Fulya Taylan
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Daniel C Jans
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | | | - Adriana Katz
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovoth, Israel
| | - Paula F Kinoshita
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, São Paulo, Brazil
| | - Benjamin Portal
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Inger Nennesmo
- Department of Pathology, Karolinska University Hospital, Stockholm, Sweden
| | - Maria Lindskog
- Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Steven J D Karlish
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovoth, Israel
| | | | - Anna Lindstrand
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden; Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
| | - Anita Aperia
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
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2
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Zhang S, Cheng M, Dhinakaran MK, Sun Y, Li H. Enantioselective Antiport in Asymmetric Nanochannels. ACS NANO 2021; 15:13148-13154. [PMID: 34319088 DOI: 10.1021/acsnano.1c02630] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Enantioselective sensing and separation are major challenges. Nanochannel technologies are energy-saving and efficient for membrane separation. Herein, inspired by biological antiporter proteins, artificial nanochannels with antiporter behavior were fabricated for chiral sensing and separation. Tyrosine enantiomers were incorporated into hourglass-shaped nanochannels via stepwise modifications to fabricating multiligand-modified asymmetric channels. Chiral distinction of naproxen enantiomers was amplified in the l-Tyr/d-Tyr channels, with an enantioselectivity coefficient of 524, which was over 100-fold that of one-ligand-modified nanochannels. Furthermore, transport experiments evidenced the spontaneous antiport of naproxen enantiomers in the l-Tyr/d-Tyr channels. The racemic naproxen sample was separated via the chiral antiport process, with an enantiomeric excess of 71.2%. Further analysis using electro-osmotic flow experiments and finite-element simulations confirmed that the asymmetric modified multiligand was key to achieving separation of the naproxen enantiomers. We expect these multiligand-modified asymmetric nanochannels to provide insight into mimicking biological antiporter systems and offer an approach to energy-efficient and robust enantiomer separation.
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Affiliation(s)
- Siyun Zhang
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University (CCNU), Wuhan, 430079, People's Republic of China
| | - Ming Cheng
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University (CCNU), Wuhan, 430079, People's Republic of China
| | - Manivannan Kalavathi Dhinakaran
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University (CCNU), Wuhan, 430079, People's Republic of China
| | - Yue Sun
- State Key Laboratory of Separation Membrane and Membrane Process, School of Chemistry, Tiangong University, Tianjin 300387, People's Republic of China
- Hubei Key Laboratory of Catalysis and Materials Science, College of Chemistry and Material Sciences, South-Central University for Nationalities, Wuhan 430074, People's Republic of China
| | - Haibing Li
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University (CCNU), Wuhan, 430079, People's Republic of China
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3
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Mouillot T, Brindisi MC, Chambrier C, Audia S, Brondel L. [Refeeding syndrome]. Rev Med Interne 2021; 42:346-354. [PMID: 33549330 DOI: 10.1016/j.revmed.2020.12.012] [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: 04/11/2020] [Revised: 11/22/2020] [Accepted: 12/26/2020] [Indexed: 10/22/2022]
Abstract
Refeeding syndrome (RS) is a rare but severe condition that is poorly understood, often under-diagnosed and can lead to death. It occurs within 5 days after refeeding in patients after prolonged fasting or in a context of undernutrition. As a consequence of the abrupt transition from catabolism to anabolism, RS is defined as a decrease in plasma levels of phosphorus, potassium and/or magnesium, whether or not associated with organ dysfunction resulting from a decrease in one of the electrolytes or a thiamine deficiency, after refeeding. The clinical symptoms are varied and non-specific and are related to hydro electrolyte disorders, sodium-hydroxide retention or failure of one or more organs. Patient management should be appropriate with regular clinical examination and careful biological monitoring, including hydro electrolyte monitoring. The correction of hydroelectrolytic disorders and systematic thiamine supplementation are essential during refeeding, that must be done carefully and very progressively, whatever its form (oral, enteral or parenteral). The severity of the refeeding syndrome indicates that its prevention and screening are the corners of its management in at-risk patients.
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Affiliation(s)
- T Mouillot
- Service d'hépato-gastro-entérologie, CHU F.-Mitterrand, 21000 Dijon, France; AgroSup Dijon, CNRS, Inrae, centre des sciences du goût et de l'alimentation, université Bourgogne Franche-Comté, 21000 Dijon, France.
| | - M-C Brindisi
- AgroSup Dijon, CNRS, Inrae, centre des sciences du goût et de l'alimentation, université Bourgogne Franche-Comté, 21000 Dijon, France; Service d'endocrinologie et diabétologie, CHU F.-Mitterrand, 21000 Dijon, France
| | - C Chambrier
- Service de nutrition clinique intensive, hospices civils de Lyon, hôpital Lyon sud, 69495 Pierre-Bénite, France
| | - S Audia
- Service de médecine interne 1, CHU F.-Mitterrand, 21000 Dijon, France
| | - L Brondel
- Service d'hépato-gastro-entérologie, CHU F.-Mitterrand, 21000 Dijon, France; AgroSup Dijon, CNRS, Inrae, centre des sciences du goût et de l'alimentation, université Bourgogne Franche-Comté, 21000 Dijon, France
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4
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Peng W, Xie Y, Liu K, Qi H, Liu Z, Xia J, Cao H, Guo C, Sun Y, Liu X, Li B, Wen F, Zhang F, Zhang L. Discrepant acute effect of saline loading on blood pressure, urinary sodium and potassium according to salt intake level: EpiSS study. J Clin Hypertens (Greenwich) 2020; 23:289-300. [PMID: 33220161 PMCID: PMC8029760 DOI: 10.1111/jch.14106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/22/2020] [Accepted: 11/02/2020] [Indexed: 11/28/2022]
Abstract
Acute dietary salt intake may cause an elevation in blood pressure (BP). The study aimed to assess the acute effect of saline loading on BP in subjects with different levels of salt intake. This study is based on the baseline survey of systemic epidemiology of salt sensitivity study. The sodium excretion in the 24-hour urine was calculated for estimating the level of salt intake. Subjects were performed an acute oral saline loading test (1 L), and data of 2019 participants were included for analyses. Multivariate linear regression and stratified analyses were performed to identify associations between 24-hour urinary sodium (24hUNa) with BP changes. Due to saline loading, systolic BP (SBP), pulse pressure, and urinary sodium concentration were significantly increased, while diastolic BP, heart rate, and urinary potassium concentration were significantly decreased. The SBP increments were more significant in subjects with lower salt intake, normotensives, elders, males, smokers, and drinkers. There was a significant linear negative dose-response association between SBP increment with 24hUNa (β = -0.901, 95% CI: -1.253, -0.548), especially in lower salt intake individuals (β = -1.297, 95% CI: -2.338, -0.205) and hypertensive patients (β = -1.502, 95% CI: -2.037, -0.967). After excluding patients who received antidiabetic or antihypertensive medicines, the effects of negative associations weakened but remained significantly. In conclusion, acute salt loading leads to an increment in SBP, and the increased SBP was negatively related with 24hUNa. This study indicated avoiding acute salt loading was important for escaping acute BP changes, especially in lower salt intake populations.
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Affiliation(s)
- Wenjuan Peng
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Yunyi Xie
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Kuo Liu
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Han Qi
- The National Clinical Research Center for Mental Disorders, Beijing Key Laboratory of Mental Disorders, The Advanced Innovation Center for Human Brain Protection, Beijing Anding Hospital, School of Mental Health, Capital Medical University, Beijing, China
| | - Zheng Liu
- Science Department, Peking University People's Hospital, Beijing, China
| | - Juan Xia
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Han Cao
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Chunyue Guo
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Yanyan Sun
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Xiaohui Liu
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Bingxiao Li
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Fuyuan Wen
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Fengxu Zhang
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
| | - Ling Zhang
- Department of Epidemiology and Health Statistics, School of Public Health, Capital Medical University, Beijing, China.,Beijing Municipal Key Laboratory of Clinical Epidemiology, Capital Medical University, Beijing, China
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da Silva JSV, Seres DS, Sabino K, Adams SC, Berdahl GJ, Citty SW, Cober MP, Evans DC, Greaves JR, Gura KM, Michalski A, Plogsted S, Sacks GS, Tucker AM, Worthington P, Walker RN, Ayers P. ASPEN Consensus Recommendations for Refeeding Syndrome. Nutr Clin Pract 2020; 35:178-195. [DOI: 10.1002/ncp.10474] [Citation(s) in RCA: 104] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
| | - David S. Seres
- Columbia University Irving Medical Center New York New York USA
| | - Kim Sabino
- Saint Francis Hospital and Medical Center Hartford Connecticut USA
| | | | - Gideon J. Berdahl
- School of Pharmacy, University of Mississippi Jackson Mississippi USA
| | | | - M. Petrea Cober
- Akron Children's Hospital Akron Ohio USA
- Northeast Ohio Medical University Rootstown Ohio USA
| | - David C. Evans
- Ohio Health Trauma and Surgical Services Columbus Ohio USA
| | - June R. Greaves
- Coram CVS Speciality Infusion Services Northbrook Illinois USA
| | | | - Austin Michalski
- Patient Food and Nutrition ServicesMichigan Medicine Ann Arbor Michigan USA
| | - Stephen Plogsted
- Nutrition Support ServiceNationwide Children's Hospital Columbus Ohio USA
| | - Gordon S. Sacks
- Medical AffairsFresenius Kabi USA LLC Lake Zurich Illinois USA
| | - Anne M. Tucker
- Critical Care and Nutrition SupportUniversity of Texas M D Anderson Cancer Center Houston Texas USA
| | | | - Renee N. Walker
- Michael E. DeBakey Veterans Affairs Medical Center Houston Texas USA
| | - Phil Ayers
- Clinical Pharmacy ServicesMississippi Baptist Medical Center Jackson Mississippi USA
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6
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Meyer DJ, Gatto C, Artigas P. Na/K Pump Mutations Associated with Primary Hyperaldosteronism Cause Loss of Function. Biochemistry 2019; 58:1774-1785. [PMID: 30811176 DOI: 10.1021/acs.biochem.9b00051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Primary hyperaldosteronism (Conn's syndrome), a common cause of secondary hypertension, is frequently produced by unilateral aldosterone-producing adenomas that carry mutations in ion-transporting genes, including ATP1A1, encoding the Na/K pump's α1 subunit. Whether Na/K pump mutant-mediated inward currents are required to depolarize the cell and increase aldosterone production remains unclear, as such currents were observed in four out of five mutants described so far. Here, we use electrophysiology and uptake of the K+ congener 86Rb+, to characterize the effects of eight additional Na/K pump mutations in transmembrane segments TM1 (delM102-L103, delL103-L104, and delM102-I106), TM4 (delI322-I325 and I327S), and TM9 (delF956-E961, delF959-E961, and delE960-L964), expressed in Xenopus oocytes. All deletion mutants induced abnormal inward currents of different amplitudes at physiological voltages, while I327S lacked such currents. A detailed functional characterization revealed that I327S significantly reduces intracellular Na+ affinity without altering affinity for external K+. 86Rb+-uptake experiments show that I327S dramatically impairs function under physiological concentrations of Na+ and K+. Since Na/K pumps in the adrenal cortex may be formed by association of α1 with β3 instead of β1 subunits, we evaluated whether G99R (another mutant without inward currents when associated with β1) would show inward currents when associated with β3. We found that the kinetic characteristics of either mutant or wild-type α1β3 pumps expressed in Xenopus oocytes to be indistinguishable from those of α1β1 pumps. The observed functional consequences of each hyperaldosteronism mutant point to the loss of Na/K pump function as the common feature of all mutants, which is sufficient to induce hyperaldosteronism.
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Affiliation(s)
- Dylan J Meyer
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research , Texas Tech University Health Sciences Center , Lubbock , Texas 79430 , United States
| | - Craig Gatto
- School of Biological Sciences , Illinois State University , Normal , Illinois 61790 , United States
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research , Texas Tech University Health Sciences Center , Lubbock , Texas 79430 , United States
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7
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Sweadner KJ, Arystarkhova E, Penniston JT, Swoboda KJ, Brashear A, Ozelius LJ. Genotype-structure-phenotype relationships diverge in paralogs ATP1A1, ATP1A2, and ATP1A3. NEUROLOGY-GENETICS 2019; 5:e303. [PMID: 30842972 PMCID: PMC6384024 DOI: 10.1212/nxg.0000000000000303] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 11/08/2018] [Indexed: 11/15/2022]
Abstract
Objective We tested the assumption that closely related genes should have similar pathogenic variants by analyzing >200 pathogenic variants in a gene family with high neurologic impact and high sequence identity, the Na,K-ATPases ATP1A1, ATP1A2, and ATP1A3. Methods Data sets of disease-associated variants were compared. Their equivalent positions in protein crystal structures were used for insights into pathogenicity and correlated with the phenotype and conservation of homology. Results Relatively few mutations affected the corresponding amino acids in 2 genes. In the membrane domain of ATP1A3 (primarily expressed in neurons), variants producing milder neurologic phenotypes had different structural positions than variants producing severe phenotypes. In ATP1A2 (primarily expressed in astrocytes), membrane domain variants characteristic of severe phenotypes in ATP1A3 were absent from patient data. The known variants in ATP1A1 fell into 2 distinct groups. Sequence conservation was an imperfect indicator: it varied among structural domains, and some variants with demonstrated pathogenicity were in low conservation sites. Conclusions Pathogenic variants varied between genes despite high sequence identity, and there is a genotype-structure-phenotype relationship in ATP1A3 that correlates with neurologic outcomes. The absence of "severe" pathogenic variants in ATP1A2 patients predicts that they will manifest either in a different tissue or by death in utero and that new ATP1A1 variants will produce additional phenotypes. It is important that some variants in poorly conserved amino acids are nonetheless pathogenic and could be incorrectly predicted to be benign.
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Affiliation(s)
- Kathleen J Sweadner
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
| | - Elena Arystarkhova
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
| | - John T Penniston
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
| | - Kathryn J Swoboda
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
| | - Allison Brashear
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
| | - Laurie J Ozelius
- Department of Neurosurgery (K.J. Sweadner, E.A., J.T.P.), Center for Human Genetics Research (K.J. Swoboda), and Department of Neurology, (K.J. Swoboda, L.J.O.) Massachusetts General Hospital, Boston; and the Department of Neurology (A.B.), Wake Forest School of Medicine, Winston-Salem, NC
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8
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Dubey V, Han M, Kopec W, Solov'yov IA, Abe K, Khandelia H. K + binding and proton redistribution in the E 2P state of the H +, K +-ATPase. Sci Rep 2018; 8:12732. [PMID: 30143663 PMCID: PMC6109069 DOI: 10.1038/s41598-018-30885-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/07/2018] [Indexed: 12/13/2022] Open
Abstract
The H+, K+-ATPase (HKA) uses ATP to pump protons into the gastric lumen against a million-fold proton concentration gradient while counter-transporting K+ from the lumen. The mechanism of release of a proton into a highly acidic stomach environment, and the subsequent binding of a K+ ion necessitates a network of protonable residues and dynamically changing protonation states in the cation binding pocket dominated by five acidic amino acid residues E343, E795, E820, D824, and D942. We perform molecular dynamics simulations of spontaneous K+ binding to all possible protonation combinations of the acidic amino acids and carry out free energy calculations to determine the optimal protonation state of the luminal-open E2P state of the pump which is ready to bind luminal K+. A dynamic pKa correlation analysis reveals the likelihood of proton transfer events within the cation binding pocket. In agreement with in-vitro measurements, we find that E795 is likely to be protonated, and that E820 is at the center of the proton transfer network in the luminal-open E2P state. The acidic residues D942 and D824 are likely to remain protonated, and the proton redistribution occurs predominantly amongst the glutamate residues exposed to the lumen. The analysis also shows that a lower number of K+ ions bind at lower pH, modeled by a higher number of protons in the cation binding pocket, in agreement with the 'transport stoichiometry variation' hypothesis.
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Affiliation(s)
- Vikas Dubey
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, 5230 M, Denmark
- MEMPHYS-Center for Biomembrane Physics, Odense, Denmark
| | - Minwoo Han
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, 5230 M, Denmark
- MEMPHYS-Center for Biomembrane Physics, Odense, Denmark
| | - Wojciech Kopec
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Ilia A Solov'yov
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, 5230 M, Denmark
| | - Kazuhiro Abe
- Cellular and Structural Physiology Institute and Department of Medicinal Science, Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, 464-8601, Japan
| | - Himanshu Khandelia
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, 5230 M, Denmark.
- MEMPHYS-Center for Biomembrane Physics, Odense, Denmark.
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9
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The CAPOS mutation in ATP1A3 alters Na/K-ATPase function and results in auditory neuropathy which has implications for management. Hum Genet 2018; 137:111-127. [PMID: 29305691 DOI: 10.1007/s00439-017-1862-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Accepted: 12/14/2017] [Indexed: 12/21/2022]
Abstract
Cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorineural hearing impairment (CAPOS) is a rare clinically distinct syndrome caused by a single dominant missense mutation, c.2452G>A, p.Glu818Lys, in ATP1A3, encoding the neuron-specific alpha subunit of the Na+/K+-ATPase α3. Allelic mutations cause the neurological diseases rapid dystonia Parkinsonism and alternating hemiplegia of childhood, disorders which do not encompass hearing or visual impairment. We present detailed clinical phenotypic information in 18 genetically confirmed patients from 11 families (10 previously unreported) from Denmark, Sweden, UK and Germany indicating a specific type of hearing impairment-auditory neuropathy (AN). All patients were clinically suspected of CAPOS and had hearing problems. In this retrospective analysis of audiological data, we show for the first time that cochlear outer hair cell activity was preserved as shown by the presence of otoacoustic emissions and cochlear microphonic potentials, but the auditory brainstem responses were grossly abnormal, likely reflecting neural dyssynchrony. Poor speech perception was observed, especially in noise, which was beyond the hearing level obtained in the pure tone audiograms in several of the patients presented here. Molecular modelling and in vitro electrophysiological studies of the specific CAPOS mutation were performed. Heterologous expression studies of α3 with the p.Glu818Lys mutation affects sodium binding to, and release from, the sodium-specific site in the pump, the third ion-binding site. Molecular dynamics simulations confirm that the structure of the C-terminal region is affected. In conclusion, we demonstrate for the first time evidence for auditory neuropathy in CAPOS syndrome, which may reflect impaired propagation of electrical impulses along the spiral ganglion neurons. This has implications for diagnosis and patient management. Auditory neuropathy is difficult to treat with conventional hearing aids, but preliminary improvement in speech perception in some patients suggests that cochlear implantation may be effective in CAPOS patients.
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10
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Abstract
Insufficient sodium-ion extrusion by mutated Na+,K+-ATPases causes hyperaldosteronism.
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11
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Meyer DJ, Gatto C, Artigas P. On the effect of hyperaldosteronism-inducing mutations in Na/K pumps. J Gen Physiol 2017; 149:1009-1028. [PMID: 29030398 PMCID: PMC5677107 DOI: 10.1085/jgp.201711827] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 11/29/2022] Open
Abstract
Mutated Na/K pumps in adrenal adenomas are thought to cause hyperaldosteronism via a gain-of-function effect involving a depolarizing inward current. The findings of Meyer et al. suggest instead that the common mechanism by which Na/K pump mutants lead to hyperaldosteronism is a loss-of-function. Primary aldosteronism, a condition in which too much aldosterone is produced and that leads to hypertension, is often initiated by an aldosterone-producing adenoma within the zona glomerulosa of the adrenal cortex. Somatic mutations of ATP1A1, encoding the Na/K pump α1 subunit, have been found in these adenomas. It has been proposed that a passive inward current transported by several of these mutant pumps is a "gain-of-function" activity that produces membrane depolarization and concomitant increases in aldosterone production. Here, we investigate whether the inward current through mutant Na/K pumps is large enough to induce depolarization of the cells that harbor them. We first investigate inward currents induced by these mutations in Xenopus Na/K pumps expressed in Xenopus oocytes and find that these inward currents are similar in amplitude to wild-type outward Na/K pump currents. Subsequently, we perform a detailed functional evaluation of the human Na/K pump mutants L104R, delF100-L104, V332G, and EETA963S expressed in Xenopus oocytes. By combining two-electrode voltage clamp with [3H]ouabain binding, we measure the turnover rate of these inward currents and compare it to the turnover rate for outward current through wild-type pumps. We find that the turnover rate of the inward current through two of these mutants (EETA963S and L104R) is too small to induce significant cell depolarization. Electrophysiological characterization of another hyperaldosteronism-inducing mutation, G99R, reveals the absence of inward currents under many different conditions, including in the presence of the regulator FXYD1 as well as with mammalian ionic concentrations and body temperatures. Instead, we observe robust outward currents, but with significantly reduced affinities for intracellular Na+ and extracellular K+. Collectively, our results point to loss-of-function as the common mechanism for the hyperaldosteronism induced by these Na/K pump mutants.
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Affiliation(s)
- Dylan J Meyer
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX.,School of Biological Sciences, Illinois State University, Normal, IL
| | - Craig Gatto
- School of Biological Sciences, Illinois State University, Normal, IL
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
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12
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Zhekova HR, Ngo V, da Silva MC, Salahub D, Noskov S. Selective ion binding and transport by membrane proteins – A computational perspective. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2017.03.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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13
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Bandulik S. Of channels and pumps: different ways to boost the aldosterone? Acta Physiol (Oxf) 2017; 220:332-360. [PMID: 27862984 DOI: 10.1111/apha.12832] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 08/10/2016] [Accepted: 11/11/2016] [Indexed: 01/19/2023]
Abstract
The mineralocorticoid aldosterone is a major factor controlling the salt and water balance and thereby also the arterial blood pressure. Accordingly, primary aldosteronism (PA) characterized by an inappropriately high aldosterone secretion is the most common form of secondary hypertension. The physiological stimulation of aldosterone synthesis in adrenocortical glomerulosa cells by angiotensin II and an increased plasma K+ concentration depends on a membrane depolarization and an increase in the cytosolic Ca2+ activity. Recurrent gain-of-function mutations of ion channels and transporters have been identified in a majority of cases of aldosterone-producing adenomas and in familial forms of PA. In this review, the physiological role of these genes in the regulation of aldosterone synthesis and the altered function of the mutant proteins as well are described. The specific changes of the membrane potential and the cellular ion homoeostasis in adrenal cells expressing the different mutants are compared, and their impact on autonomous aldosterone production and proliferation is discussed.
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Affiliation(s)
- S. Bandulik
- Medical Cell Biology; University of Regensburg; Regensburg Germany
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14
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Abstract
The sodium and potassium gradients across the plasma membrane are used by animal cells for numerous processes, and the range of demands requires that the responsible ion pump, the Na,K-ATPase, can be fine-tuned to the different cellular needs. Therefore, several isoforms are expressed of each of the three subunits that make a Na,K-ATPase, the alpha, beta and FXYD subunits. This review summarizes the various roles and expression patterns of the Na,K-ATPase subunit isoforms and maps the sequence variations to compare the differences structurally. Mutations in the Na,K-ATPase genes encoding alpha subunit isoforms have severe physiological consequences, causing very distinct, often neurological diseases. The differences in the pathophysiological effects of mutations further underline how the kinetic parameters, regulation and proteomic interactions of the Na,K-ATPase isoforms are optimized for the individual cellular needs.
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Affiliation(s)
- Michael V Clausen
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark
| | - Florian Hilbers
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark
| | - Hanne Poulsen
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark
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15
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Abstract
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.
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Affiliation(s)
- Petra Čechová
- Department of Biophysics, Centre of the Region Hana for Biotechnological and Agricultural Research, Faculty of Science, Palacký University , Šlechtitelů 27, 783 71, Olomouc, Czech Republic
| | - Karel Berka
- Department of Physical Chemistry, Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University , 17. listopadu 12, 77146 Olomouc, Czech Republic
| | - Martin Kubala
- Department of Biophysics, Centre of the Region Hana for Biotechnological and Agricultural Research, Faculty of Science, Palacký University , Šlechtitelů 27, 783 71, Olomouc, Czech Republic
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16
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Stindl J, Tauber P, Sterner C, Tegtmeier I, Warth R, Bandulik S. Pathogenesis of Adrenal Aldosterone-Producing Adenomas Carrying Mutations of the Na(+)/K(+)-ATPase. Endocrinology 2015; 156:4582-91. [PMID: 26418325 DOI: 10.1210/en.2015-1466] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Aldosterone-producing adenoma (APA) is a major cause of primary aldosteronism, leading to secondary hypertension. Somatic mutations in the gene for the α1 subunit of the Na(+)/K(+)-ATPase were found in about 6% of APAs. APA-related α1 subunit of the Na(+)/K(+)-ATPase mutations lead to a loss of the pump function of the Na(+)/K(+)-ATPase, which is believed to result in membrane depolarization and Ca(2+)-dependent stimulation of aldosterone synthesis in adrenal cells. In addition, H(+) and Na(+) leak currents via the mutant Na(+)/K(+)-ATPase were suggested to contribute to the phenotype. The aim of this study was to investigate the cellular pathophysiology of adenoma-associated Na(+)/K(+)-ATPase mutants (L104R, V332G, G99R) in adrenocortical NCI-H295R cells. The expression of these Na(+)/K(+)-ATPase mutants depolarized adrenal cells and stimulated aldosterone secretion. However, an increase of basal cytosolic Ca(2+) levels in Na(+)/K(+)-ATPase mutant cells was not detectable, and stimulation with high extracellular K(+) hardly increased Ca(2+) levels in cells expressing L104R and V332G mutant Na(+)/K(+)-ATPase. Cytosolic pH measurements revealed an acidification of L104R and V332G mutant cells, despite an increased activity of the Na(+)/H(+) exchanger. The possible contribution of cellular acidification to the hypersecretion of aldosterone was supported by the observation that aldosterone secretion of normal adrenocortical cells was stimulated by acetate-induced acidification. Taken together, mutations of the Na(+)/K(+)-ATPase depolarize adrenocortical cells, disturb the K(+) sensitivity, and lower intracellular pH but, surprisingly, do not induce an overt increase of intracellular Ca(2+). Probably, the autonomous aldosterone secretion is caused by the concerted action of several pathological signaling pathways and incomplete cellular compensation.
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Affiliation(s)
- J Stindl
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
| | - P Tauber
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
| | - C Sterner
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
| | - I Tegtmeier
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
| | - R Warth
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
| | - S Bandulik
- Medical Cell Biology, University of Regensburg, 93053 Regensburg, Germany
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17
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Cheng Y, Zhou M, Wang Y. Arctigenin antagonizes mineralocorticoid receptor to inhibit the transcription of Na/K-ATPase. J Recept Signal Transduct Res 2015; 36:181-8. [DOI: 10.3109/10799893.2015.1075039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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18
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Abstract
The Na+/K+-ATPase restores sodium
(Na+) and potassium (K+)
electrochemical gradients dissipated by action potentials and ion-coupled transport
processes. As ions are transported, they become transiently trapped between
intracellular and extracellular gates. Once the external gate opens, three
Na+ ions are released, followed by the binding and
occlusion of two K+ ions. While the mechanisms of
Na+ release have been well characterized by the study of
transient Na+ currents, smaller and faster transient
currents mediated by external K+ have been more difficult to
study. Here we show that external K+ ions travelling to
their binding sites sense only a small fraction of the electric field as they
rapidly and simultaneously become occluded. Consistent with these results, molecular
dynamics simulations of a pump model show a wide water-filled access channel
connecting the binding site to the external solution. These results suggest a
mechanism of K+ gating different from that of
Na+ occlusion. During transport by the
Na+/K+-ATPase,
Na+ and K+ ions become occluded
between intra- and extracellular gates. Here Castillo et al. measure transient
electrical signals arising from K+ occlusion and use molecular
simulations to describe a K+ gating mechanism fundamentally
different to that of Na+.
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19
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Gomez-Sanchez CE, Kuppusamy M, Gomez-Sanchez EP. Somatic mutations of the ATP1A1 gene and aldosterone-producing adenomas. Mol Cell Endocrinol 2015; 408:213-9. [PMID: 25496839 PMCID: PMC4417446 DOI: 10.1016/j.mce.2014.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/05/2014] [Accepted: 12/05/2014] [Indexed: 01/01/2023]
Abstract
Primary aldosteronism is the most common form of secondary hypertension. It affects approximately 10% of patients with hypertension and causes greater cardiovascular morbidity and mortality compared to essential hypertension of similar severity and duration. The cause of primary aldosteronism in about half of these patients is an aldosterone-producing adenoma; over half of these adenomas have mutations in one of several ion channels and pumps, including the potassium channel KCNJ5, calcium channel Cav1.3, α1 subunit of the sodium potassium ATPase, and membrane calcium ATPase 3. This review concentrates on the molecular and physiological mechanisms by which mutations of the ATP1A1 gene increase aldosterone production.
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Affiliation(s)
- Celso E Gomez-Sanchez
- Division of Endocrinology, G.V. (Sonny) Montgomery VA Medical Center, Jackson, MS, USA; Department of Medicine-Endocrinology, University of Mississippi Medical Center, Jackson, MS, USA.
| | - Maniselvan Kuppusamy
- Department of Medicine-Endocrinology, University of Mississippi Medical Center, Jackson, MS, USA
| | - Elise P Gomez-Sanchez
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS, USA
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20
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Mahmmoud YA, Kopec W, Khandelia H. K+ congeners that do not compromise Na+ activation of the Na+,K+-ATPase: hydration of the ion binding cavity likely controls ion selectivity. J Biol Chem 2014; 290:3720-31. [PMID: 25533461 DOI: 10.1074/jbc.m114.577486] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Na(+),K(+)-ATPase is essential for ionic homeostasis in animal cells. The dephosphoenzyme contains Na(+) selective inward facing sites, whereas the phosphoenzyme contains K(+) selective outward facing sites. Under normal physiological conditions, K(+) inhibits cytoplasmic Na(+) activation of the enzyme. Acetamidinium (Acet(+)) and formamidinium (Form(+)) have been shown to permeate the pump through the outward facing sites. Here, we show that these cations, unlike K(+), are unable to enter the inward facing sites in the dephosphorylated enzyme. Consistently, the organic cations exhibited little to no antagonism to cytoplasmic Na(+) activation. Na(+),K(+)-ATPase structures revealed a previously undescribed rotamer transition of the hydroxymethyl side chain of the absolutely conserved Thr(772) of the α-subunit. The side chain contributes its hydroxyl to Na(+) in site I in the E1 form and rotates to contribute its methyl group toward K(+) in the E2 form. Molecular dynamics simulations to the E1·AlF4 (-)·ADP·3Na(+) structure indicated that 1) bound organic cations differentially distorted the ion binding sites, 2) the hydroxymethyl of Thr(772) rotates to stabilize bound Form(+) through water molecules, and 3) the rotamer transition is mediated by water traffic into the ion binding cavity. Accordingly, dehydration induced by osmotic stress enhanced the interaction of the congeners with the outward facing sites and profoundly modified the organization of membrane domains of the α-subunit. These results assign a catalytic role for water in pump function, and shed light on a backbone-independent but a conformation-dependent switch between H-bond and dispersion contact as part of the catalytic mechanism of the Na(+),K(+)-ATPase.
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Affiliation(s)
- Yasser A Mahmmoud
- From the Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C and
| | - Wojciech Kopec
- the MEMPHYS, Center for Biomembrane Physics, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Himanshu Khandelia
- the MEMPHYS, Center for Biomembrane Physics, University of Southern Denmark, DK-5230 Odense M, Denmark
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