1
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Hodeify R, Kreydiyyeh S, Zaid LMJ. Identified and potential internalization signals involved in trafficking and regulation of Na +/K + ATPase activity. Mol Cell Biochem 2024; 479:1583-1598. [PMID: 37634170 PMCID: PMC11254989 DOI: 10.1007/s11010-023-04831-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 08/14/2023] [Indexed: 08/29/2023]
Abstract
The sodium-potassium pump (NKA) or Na+/K+ ATPase consumes around 30-40% of the total energy expenditure of the animal cell on the generation of the sodium and potassium electrochemical gradients that regulate various electrolyte and nutrient transport processes. The vital role of this protein entails proper spatial and temporal regulation of its activity through modulatory mechanisms involving its expression, localization, enzymatic activity, and protein-protein interactions. The residence of the NKA at the plasma membrane is compulsory for its action as an antiporter. Despite the huge body of literature reporting on its trafficking between the cell membrane and intracellular compartments, the mechanisms controlling the trafficking process are by far the least understood. Among the molecular determinants of the plasma membrane proteins trafficking are intrinsic sequence-based endocytic motifs. In this review, we (i) summarize previous reports linking the regulation of Na+/K+ ATPase trafficking and/or plasma membrane residence to its activity, with particular emphasis on the endocytic signals in the Na+/K+ ATPase alpha-subunit, (ii) map additional potential internalization signals within Na+/K+ ATPase catalytic alpha-subunit, based on canonical and noncanonical endocytic motifs reported in the literature, (iii) pinpoint known and potential phosphorylation sites associated with NKA trafficking, (iv) highlight our recent studies on Na+/K+ ATPase trafficking and PGE2-mediated Na+/K+ ATPase modulation in intestine, liver, and kidney cells.
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Affiliation(s)
- Rawad Hodeify
- Department of Biotechnology, School of Arts and Sciences, American University of Ras Al Khaimah, Ras Al Khaimah, United Arab Emirates.
| | - Sawsan Kreydiyyeh
- Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Beirut, Lebanon
| | - Leen Mohammad Jamal Zaid
- Department of Biotechnology, School of Arts and Sciences, American University of Ras Al Khaimah, Ras Al Khaimah, United Arab Emirates
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2
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Weber DK, Reddy UV, Wang S, Larsen EK, Gopinath T, Gustavsson MB, Cornea RL, Thomas DD, De Simone A, Veglia G. Structural basis for allosteric control of the SERCA-Phospholamban membrane complex by Ca 2+ and phosphorylation. eLife 2021; 10:66226. [PMID: 33978571 PMCID: PMC8184213 DOI: 10.7554/elife.66226] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 05/10/2021] [Indexed: 01/26/2023] Open
Abstract
Phospholamban (PLN) is a mini-membrane protein that directly controls the cardiac Ca2+-transport response to β-adrenergic stimulation, thus modulating cardiac output during the fight-or-flight response. In the sarcoplasmic reticulum membrane, PLN binds to the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA), keeping this enzyme's function within a narrow physiological window. PLN phosphorylation by cAMP-dependent protein kinase A or increase in Ca2+ concentration reverses the inhibitory effects through an unknown mechanism. Using oriented-sample solid-state NMR spectroscopy and replica-averaged NMR-restrained structural refinement, we reveal that phosphorylation of PLN's cytoplasmic regulatory domain signals the disruption of several inhibitory contacts at the transmembrane binding interface of the SERCA-PLN complex that are propagated to the enzyme's active site, augmenting Ca2+ transport. Our findings address long-standing questions about SERCA regulation, epitomizing a signal transduction mechanism operated by posttranslationally modified bitopic membrane proteins.
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Affiliation(s)
- Daniel K Weber
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - U Venkateswara Reddy
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - Songlin Wang
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - Erik K Larsen
- Department of Chemistry, University of Minnesota, Minneapolis, United States
| | - Tata Gopinath
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - Martin B Gustavsson
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - Razvan L Cornea
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - David D Thomas
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States
| | - Alfonso De Simone
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom.,Department of Pharmacy, University of Naples 'Federico II', Naples, Italy
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, United States.,Department of Chemistry, University of Minnesota, Minneapolis, United States
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3
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Alford RF, Smolin N, Young HS, Gray JJ, Robia SL. Protein docking and steered molecular dynamics suggest alternative phospholamban-binding sites on the SERCA calcium transporter. J Biol Chem 2020; 295:11262-11274. [PMID: 32554805 DOI: 10.1074/jbc.ra120.012948] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 06/16/2020] [Indexed: 01/27/2023] Open
Abstract
The transport activity of the sarco(endo)plasmic reticulum calcium ATPase (SERCA) in cardiac myocytes is modulated by an inhibitory interaction with a transmembrane peptide, phospholamban (PLB). Previous biochemical studies have revealed that PLB interacts with a specific inhibitory site on SERCA, and low-resolution structural evidence suggests that PLB interacts with distinct alternative sites on SERCA. High-resolution details of the structural determinants of SERCA regulation have been elusive because of the dynamic nature of the regulatory complex. In this study, we used computational approaches to develop a structural model of SERCA-PLB interactions to gain a mechanistic understanding of PLB-mediated SERCA transport regulation. We combined steered molecular dynamics and membrane protein-protein docking experiments to achieve both a global search and all-atom force calculations to determine the relative affinities of PLB for candidate sites on SERCA. We modeled the binding of PLB to several SERCA conformations, representing different enzymatic states sampled during the calcium transport catalytic cycle. The results of the steered molecular dynamics and docking experiments indicated that the canonical PLB-binding site (comprising transmembrane helices M2, M4, and M9) is the preferred site. This preference was even more stringent for a superinhibitory PLB variant. Interestingly, PLB-binding specificity became more ambivalent for other SERCA conformers. These results provide evidence for polymorphic PLB interactions with novel sites on M3 and with the outside of the SERCA helix M9. Our findings are compatible with previous physical measurements that suggest that PLB interacts with multiple binding sites, conferring dynamic responsiveness to changing physiological conditions.
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Affiliation(s)
- Rebecca F Alford
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Nikolai Smolin
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Cardiovascular Research Institute, Loyola University Chicago, Maywood, Illinois, USA
| | - Howard S Young
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jeffrey J Gray
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Cardiovascular Research Institute, Loyola University Chicago, Maywood, Illinois, USA
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4
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Selenko P. Quo Vadis Biomolecular NMR Spectroscopy? Int J Mol Sci 2019; 20:ijms20061278. [PMID: 30875725 PMCID: PMC6472163 DOI: 10.3390/ijms20061278] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 03/07/2019] [Accepted: 03/08/2019] [Indexed: 02/06/2023] Open
Abstract
In-cell nuclear magnetic resonance (NMR) spectroscopy offers the possibility to study proteins and other biomolecules at atomic resolution directly in cells. As such, it provides compelling means to complement existing tools in cellular structural biology. Given the dominance of electron microscopy (EM)-based methods in current structure determination routines, I share my personal view about the role of biomolecular NMR spectroscopy in the aftermath of the revolution in resolution. Specifically, I focus on spin-off applications that in-cell NMR has helped to develop and how they may provide broader and more generally applicable routes for future NMR investigations. I discuss the use of ‘static’ and time-resolved solution NMR spectroscopy to detect post-translational protein modifications (PTMs) and to investigate structural consequences that occur in their response. I argue that available examples vindicate the need for collective and systematic efforts to determine post-translationally modified protein structures in the future. Furthermore, I explain my reasoning behind a Quinary Structure Assessment (QSA) initiative to interrogate cellular effects on protein dynamics and transient interactions present in physiological environments.
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Affiliation(s)
- Philipp Selenko
- Weizmann Institute of Science, Department of Biological Regulation, 234 Herzl Street, Rehovot 76100, Israel.
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5
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Polyamines regulate phosphorylation–dephosphorylation kinetics in a crustacean gill (Na+, K+)-ATPase. Mol Cell Biochem 2017; 429:187-198. [DOI: 10.1007/s11010-017-2946-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 01/17/2017] [Indexed: 12/15/2022]
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6
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Dobbelaere D, Leclerc F, Mention-Mulliez K, Vamecq J. [Propranolol and lactatemia during hypovolemic shock: a case report]. Arch Pediatr 2014; 22:292-5. [PMID: 25524288 DOI: 10.1016/j.arcped.2014.11.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 06/13/2014] [Accepted: 11/14/2014] [Indexed: 11/25/2022]
Abstract
Lactate production results from anaerobic glycolysis. This pathway is recruited physiologically during intense and sustained muscular contractions. Hyperlactatemia may develop when tissue oxygenation is jeopardized such as in shock, its absence having been, however, sometimes reported in sepsis in which interactions between infectious agents and the organism's cells might blunt or disrupt hyperlactatemia development. During the course of acute rotavirus gastroenteritis, a 9-month-old girl developed severe dehydration (capillary-refill time, 5 s) leading to hypovolemic shock without signs of sepsis and with hypotension at 62/21 mmHg Surprisingly, the child failed to develop hyperlactatemia during shock. An etiologic search to understand why hyperlactatemia did not occur revealed that this patient had been receiving propranolol since the age of four months for the treatment of a Cyrano hemangioma. Via its inhibitory action on β-adrenergic receptors, propranolol antagonizes the stimulation of glycolysis by catecholamines, which may be rationally proposed to have contributed to preventing hyperlactatemia during hypovolemic shock in this patient. Mechanisms by which propranolol can mediate this antihyperlactatemia action are further illustrated and discussed.
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Affiliation(s)
- D Dobbelaere
- Centre de référence des maladies héréditaires du métabolisme, CHRU de Lille, 59037 Lille, France
| | - F Leclerc
- Service de réanimation pédiatrique, hôpital Jeanne-de-Flandre, CHRU de Lille, 59037 Lille, France
| | - K Mention-Mulliez
- Centre de référence des maladies héréditaires du métabolisme, CHRU de Lille, 59037 Lille, France
| | - J Vamecq
- Inserm et biochimie et biologie moléculaire, HMNO, CBP, CHRU de Lille, 2, boulevard du Professeur-Jules-Leclercq, 59037 Lille, France.
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7
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Gong XM, Ding Y, Yu J, Yao Y, Marassi FM. Structure of the Na,K-ATPase regulatory protein FXYD2b in micelles: implications for membrane-water interfacial arginines. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:299-306. [PMID: 24794573 DOI: 10.1016/j.bbamem.2014.04.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/19/2014] [Accepted: 04/23/2014] [Indexed: 01/06/2023]
Abstract
FXYD2 is a membrane protein responsible for regulating the function of the Na,K-ATPase in mammalian kidney epithelial cells. Here we report the structure of FXYD2b, one of two splice variants of the protein, determined by NMR spectroscopy in detergent micelles. Solid-state NMR characterization of the protein embedded in phospholipid bilayers indicates that several arginine side chains may be involved in hydrogen bond interactions with the phospholipid polar head groups. The structure and the NMR data suggest that FXYD2b could regulate the Na,K-ATPase by modulating the effective membrane surface electrostatics near the ion binding sites of the pump.
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Affiliation(s)
- Xiao-Min Gong
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Yi Ding
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jinghua Yu
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Yong Yao
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Francesca M Marassi
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
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8
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Regulation of the cardiac Na(+) pump by palmitoylation of its catalytic and regulatory subunits. Biochem Soc Trans 2013; 41:95-100. [PMID: 23356265 DOI: 10.1042/bst20120269] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Na+/K+-ATPase (Na+ pump) is the principal consumer of ATP in multicellular organisms. In the heart, the Na+ gradient established by the pump is essential for all aspects of cardiac function, and appropriate regulation of the cardiac Na+ pump is therefore crucial to match cardiac output to the physiological requirements of an organism. The cardiac pump is a multi-subunit enzyme, consisting of a catalytic α-subunit and regulatory β- and FXYD subunits. All three subunits may become palmitoylated, although the functional outcome of these palmitoylation events is incompletely characterized to date. Interestingly, both β- and FXYD subunits may be palmitoylated or glutathionylated at the same cysteine residues. These competing chemically distinct post-translational modifications may mediate functionally different effects on the cardiac pump. In the present article, we review the cellular events that control the balance between these modifications, and discuss the likely functional effects of pump subunit palmitoylation.
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9
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Smet-Nocca C, Launay H, Wieruszeski JM, Lippens G, Landrieu I. Unraveling a phosphorylation event in a folded protein by NMR spectroscopy: phosphorylation of the Pin1 WW domain by PKA. JOURNAL OF BIOMOLECULAR NMR 2013; 55:323-337. [PMID: 23456038 DOI: 10.1007/s10858-013-9716-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 02/15/2013] [Indexed: 06/01/2023]
Abstract
The Pin1 protein plays a critical role in the functional regulation of the hyperphosphorylated neuronal Tau protein in Alzheimer's disease and is by itself regulated by phosphorylation. We have used Nuclear Magnetic Resonance (NMR) spectroscopy to both identify the PKA phosphorylation site in the Pin1 WW domain and investigate the functional consequences of this phosphorylation. Detection and identification of phosphorylation on serine/threonine residues in a globular protein, while mostly occurring in solvent-exposed flexible loops, does not lead to chemical shift changes as obvious as in disordered proteins and hence does not necessarily shift the resonances outside the spectrum of the folded protein. Other complications were encountered to characterize the extent of the phosphorylation, as part of the (1)H,(15)N amide resonances around the phosphorylation site are specifically broadened in the unphosphorylated state. Despite these obstacles, NMR spectroscopy was an efficient tool to confirm phosphorylation on S16 of the WW domain and to quantify the level of phosphorylation. Based on this analytical characterization, we show that WW phosphorylation on S16 abolishes its binding capacity to a phosphorylated Tau peptide. A reduced conformational heterogeneity and flexibility of the phospho-binding loop upon S16 phosphorylation could account for part of the decreased affinity for its phosphorylated partner. Additionally, a structural model of the phospho-WW obtained by molecular dynamics simulation and energy minimization suggests that the phosphate moiety of phospho-S16 could compete with the phospho-substrate.
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Affiliation(s)
- Caroline Smet-Nocca
- Institut Fédératif de Recherches 147, CNRS UMR 8576, Université de Lille-Nord de France, Villeneuve d'Ascq, France.
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10
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Scherer EBS, Loureiro SO, Vuaden FC, Schmitz F, Kolling J, Siebert C, Savio LEB, Schweinberger BM, Bogo MR, Bonan CD, Wyse ATS. Mild hyperhomocysteinemia reduces the activity and immunocontent, but does not alter the gene expression, of catalytic α subunits of cerebral Na+,K+-ATPase. Mol Cell Biochem 2013; 378:91-7. [DOI: 10.1007/s11010-013-1598-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 02/22/2013] [Indexed: 12/27/2022]
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11
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Cheung JY, Zhang XQ, Song J, Gao E, Chan TO, Rabinowitz JE, Koch WJ, Feldman AM, Wang J. Coordinated regulation of cardiac Na(+)/Ca (2+) exchanger and Na (+)-K (+)-ATPase by phospholemman (FXYD1). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 961:175-90. [PMID: 23224879 DOI: 10.1007/978-1-4614-4756-6_15] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Phospholemman (PLM) is the founding member of the FXYD family of regulators of ion transport. PLM is a 72-amino acid protein consisting of the signature PFXYD motif in the extracellular N terminus, a single transmembrane (TM) domain, and a C-terminal cytoplasmic tail containing three phosphorylation sites. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. The TM domain of PLM interacts with TM9 of the α-subunit of Na(+)-K(+)-ATPase, while its cytoplasmic tail interacts with two small regions (spanning residues 248-252 and 300-304) of the proximal intracellular loop of Na(+)/Ca(2+) exchanger. Under stress, catecholamine stimulation phosphorylates PLM at serine(68), resulting in relief of inhibition of Na(+)-K(+)-ATPase by decreasing K(m) for Na(+) and increasing V(max), and simultaneous inhibition of Na(+)/Ca(2+) exchanger. Enhanced Na(+)-K(+)-ATPase activity lowers intracellular Na(+), thereby minimizing Ca(2+) overload and risks of arrhythmias. Inhibition of Na(+)/Ca(2+) exchanger reduces Ca(2+) efflux, thereby preserving contractility. Thus, the coordinated actions of PLM during stress serve to minimize arrhythmogenesis and maintain inotropy. In acute cardiac ischemia and chronic heart failure, either expression or phosphorylation of PLM or both are altered. PLM regulates important ion transporters in the heart and offers a tempting target for development of drugs to treat heart failure.
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Affiliation(s)
- Joseph Y Cheung
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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12
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Fuller W, Tulloch LB, Shattock MJ, Calaghan SC, Howie J, Wypijewski KJ. Regulation of the cardiac sodium pump. Cell Mol Life Sci 2012; 70:1357-80. [PMID: 22955490 PMCID: PMC3607738 DOI: 10.1007/s00018-012-1134-y] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/27/2012] [Accepted: 08/13/2012] [Indexed: 01/24/2023]
Abstract
In cardiac muscle, the sarcolemmal sodium/potassium ATPase is the principal quantitative means of active transport at the myocyte cell surface, and its activity is essential for maintaining the trans-sarcolemmal sodium gradient that drives ion exchange and transport processes that are critical for cardiac function. The 72-residue phosphoprotein phospholemman regulates the sodium pump in the heart: unphosphorylated phospholemman inhibits the pump, and phospholemman phosphorylation increases pump activity. Phospholemman is subject to a remarkable plethora of post-translational modifications for such a small protein: the combination of three phosphorylation sites, two palmitoylation sites, and one glutathionylation site means that phospholemman integrates multiple signaling events to control the cardiac sodium pump. Since misregulation of cytosolic sodium contributes to contractile and metabolic dysfunction during cardiac failure, a complete understanding of the mechanisms that control the cardiac sodium pump is vital. This review explores our current understanding of these mechanisms.
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Affiliation(s)
- W Fuller
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine Dentistry and Nursing, University of Dundee, Dundee, UK.
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13
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Bidwell P, Blackwell DJ, Hou Z, Zima AV, Robia SL. Phospholamban binds with differential affinity to calcium pump conformers. J Biol Chem 2011; 286:35044-50. [PMID: 21832088 PMCID: PMC3186385 DOI: 10.1074/jbc.m111.266759] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 08/03/2011] [Indexed: 12/16/2022] Open
Abstract
To investigate the mechanism of regulation of sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA) by phospholamban (PLB), we expressed Cerulean-SERCA and yellow fluorescent protein (YFP)-PLB in adult rabbit ventricular myocytes using adenovirus vectors. SERCA and PLB were localized in the sarcoplasmic reticulum and were mobile over multiple sarcomeres on a timescale of tens of seconds. We also observed robust fluorescence resonance energy transfer (FRET) from Cerulean-SERCA to YFP-PLB. Electrical pacing of cardiac myocytes elicited cytoplasmic Ca(2+) elevations, but these increases in Ca(2+) produced only modest changes in SERCA-PLB FRET. The data suggest that the regulatory complex is not disrupted by elevations of cytosolic calcium during cardiac contraction (systole). This conclusion was also supported by parallel experiments in heterologous cells, which showed that FRET was reduced but not abolished by calcium. Thapsigargin also elicited a small decrease in PLB-SERCA binding affinity. We propose that PLB is not displaced from SERCA by high calcium during systole, and relief of functional inhibition does not require dissociation of the regulatory complex. The observed modest reduction in the affinity of the PLB-SERCA complex with Ca(2+) or thapsigargin suggests that the binding interface is altered by SERCA conformational changes. The results are consistent with multiple modes of PLB binding or alternative binding sites.
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Affiliation(s)
- Philip Bidwell
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153
| | - Daniel J. Blackwell
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153
| | - Zhanjia Hou
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153
| | - Aleksey V. Zima
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153
| | - Seth L. Robia
- From the Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153
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14
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Tulloch LB, Howie J, Wypijewski KJ, Wilson CR, Bernard WG, Shattock MJ, Fuller W. The inhibitory effect of phospholemman on the sodium pump requires its palmitoylation. J Biol Chem 2011; 286:36020-36031. [PMID: 21868384 DOI: 10.1074/jbc.m111.282145] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholemman (PLM), the principal sarcolemmal substrate for protein kinases A and C in the heart, regulates the cardiac sodium pump. We investigated post-translational modifications of PLM additional to phosphorylation in adult rat ventricular myocytes (ARVM). LC-MS/MS of tryptically digested PLM immunoprecipitated from ARVM identified cysteine 40 as palmitoylated in some peptides, but no information was obtained regarding the palmitoylation status of cysteine 42. PLM palmitoylation was confirmed by immunoprecipitating PLM from ARVM loaded with [(3)H]palmitic acid and immunoblotting following streptavidin affinity purification from ARVM lysates subjected to fatty acyl biotin exchange. Mutagenesis identified both Cys-40 and Cys-42 of PLM as palmitoylated. Phosphorylation of PLM at serine 68 by PKA in ARVM or transiently transfected HEK cells increased its palmitoylation, but PKA activation did not increase the palmitoylation of S68A PLM-YFP in HEK cells. Wild type and unpalmitoylatable PLM-YFP were all correctly targeted to the cell surface membrane, but the half-life of unpalmitoylatable PLM was reduced compared with wild type. In cells stably expressing inducible PLM, PLM expression inhibited the sodium pump, but PLM did not inhibit the sodium pump when palmitoylation was inhibited. Hence, palmitoylation of PLM controls its turnover, and palmitoylated PLM inhibits the sodium pump. Surprisingly, phosphorylation of PLM enhances its palmitoylation, probably through the enhanced mobility of the phosphorylated intracellular domain increasing the accessibility of cysteines for the palmitoylating enzyme, with interesting theoretical implications. All FXYD proteins have conserved intracellular cysteines, so FXYD protein palmitoylation may be a universal means to regulate the sodium pump.
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Affiliation(s)
- Lindsay B Tulloch
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Jacqueline Howie
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Krzysztof J Wypijewski
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Catherine R Wilson
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - William G Bernard
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Michael J Shattock
- Cardiovascular Division, The Rayne Institute, St. Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - William Fuller
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, United Kingdom.
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15
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Song Q, Pallikkuth S, Bossuyt J, Bers DM, Robia SL. Phosphomimetic mutations enhance oligomerization of phospholemman and modulate its interaction with the Na/K-ATPase. J Biol Chem 2011; 286:9120-6. [PMID: 21220422 DOI: 10.1074/jbc.m110.198036] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na/K-ATPase (NKA) activity is dynamically regulated by an inhibitory interaction with a small transmembrane protein, phospholemman (PLM). Inhibition is relieved upon PLM phosphorylation. Phosphorylation may alter how PLM interacts with NKA and/or itself, but details of these interactions are unknown. To address this, we quantified FRET between PLM and its regulatory target NKA in live cells. Phosphorylation of PLM was mimicked by mutation S63E (PKC site), S68E (PKA/PKC site), or S63E/S68E. The dependence of FRET on protein expression in live cells yielded information about the structure and binding affinity of the PLM-NKA regulatory complex. PLM phosphomimetic mutations altered the quaternary structure of the regulatory complex and reduced the apparent affinity of the PLM-NKA interaction. The latter effect was likely due to increased oligomerization of PLM phosphomimetic mutants, as suggested by PLM-PLM FRET measurements. Distance constraints obtained by FRET suggest that phosphomimetic mutations slightly alter the oligomer quaternary conformation. Photon-counting histogram measurements revealed that the major PLM oligomeric species is a tetramer. We conclude that phosphorylation of PLM increases its oligomerization into tetramers, decreases its binding to NKA, and alters the structures of both the tetramer and NKA regulatory complex.
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Affiliation(s)
- Qiujing Song
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois 60153, USA
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16
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Hughes E, Whittaker CAP, Barsukov IL, Esmann M, Middleton DA. A study of the membrane association and regulatory effect of the phospholemman cytoplasmic domain. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1021-31. [PMID: 21130070 DOI: 10.1016/j.bbamem.2010.11.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/18/2010] [Accepted: 11/22/2010] [Indexed: 10/18/2022]
Abstract
Phospholemman (PLM) is a single-span transmembrane protein belonging to the FXYD family of proteins. PLM (or FXYD1) regulates the Na,K-ATPase (NKA) ion pump by altering its affinity for K(+) and Na(+) and by reducing its hydrolytic activity. Structural studies of PLM in anionic detergent micelles have suggested that the cytoplasmic domain, which alone can regulate NKA, forms a partial helix which is stabilized by interactions with the charged membrane surface. This work examines the membrane affinity and regulatory function of a 35-amino acid peptide (PLM(38-72)) representing the PLM cytoplasmic domain. Isothermal titration calorimetry and solid-state NMR measurements confirm that PLM(38-72) associates strongly with highly anionic phospholipid membranes, but the association is weakened substantially when the negative surface charge is reduced to a more physiologically relevant environment. Membrane interactions are also weakened when the peptide is phosphorylated at S68, one of the substrate sites for protein kinases. PLM(38-72) also lowers the maximal velocity of ATP hydrolysis (V(max)) by NKA, and phosphorylation of the peptide at S68 gives rise to a partial recovery of V(max). These results suggest that the PLM cytoplasmic domain populates NKA-associated and membrane-associated states in dynamic equilibrium and that phosphorylation may alter the position of the equilibrium. Interestingly, peptides representing the cytoplasmic domains of two other FXYD proteins, Mat-8 (FXYD3) and CHIF (FXYD4), have little or no interaction with highly anionic phospholipid membranes and have no effect on NKA function. This suggests that the functional and physical properties of PLM are not conserved across the entire FXYD family.
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Affiliation(s)
- Eleri Hughes
- School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, UK
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Cheung JY, Zhang XQ, Song J, Gao E, Rabinowitz JE, Chan TO, Wang J. Phospholemman: a novel cardiac stress protein. Clin Transl Sci 2010; 3:189-96. [PMID: 20718822 DOI: 10.1111/j.1752-8062.2010.00213.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Phospholemman (PLM), a member of the FXYD family of regulators of ion transport, is a major sarcolemmal substrate for protein kinases A and C in cardiac and skeletal muscle. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. Functionally, when phosphorylated at serine(68), PLM stimulates Na(+)-K(+)-ATPase but inhibits Na(+)/Ca(2+) exchanger in cardiac myocytes. In heterologous expression systems, PLM modulates the gating of cardiac L-type Ca(2+) channel. Therefore, PLM occupies a key modulatory role in intracellular Na(+) and Ca(2+) homeostasis and is intimately involved in regulation of excitation-contraction (EC) coupling. Genetic ablation of PLM results in a slight increase in baseline cardiac contractility and prolongation of action potential duration. When hearts are subjected to catecholamine stress, PLM minimizes the risks of arrhythmogenesis by reducing Na(+) overload and simultaneously preserves inotropy by inhibiting Na(+)/Ca(2+) exchanger. In heart failure, both expression and phosphorylation state of PLM are altered and may partly account for abnormalities in EC coupling. The unique role of PLM in regulation of Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and potentially L-type Ca(2+) channel in the heart, together with the changes in its expression and phosphorylation in heart failure, make PLM a rational and novel target for development of drugs in our armamentarium against heart failure. Clin Trans Sci 2010; Volume 3: 189-196.
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Affiliation(s)
- Joseph Y Cheung
- Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
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