1
|
Song Q, Alvarez-Laviada A, Schrup SE, Reilly-O'Donnell B, Entcheva E, Gorelik J. Opto-SICM framework combines optogenetics with scanning ion conductance microscopy for probing cell-to-cell contacts. Commun Biol 2023; 6:1131. [PMID: 37938652 PMCID: PMC10632396 DOI: 10.1038/s42003-023-05509-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 10/26/2023] [Indexed: 11/09/2023] Open
Abstract
We present a novel framework, Opto-SICM, for studies of cellular interactions in live cells with high spatiotemporal resolution. The approach combines scanning ion conductance microscopy, SICM, and cell-type-specific optogenetic interrogation. Light-excitable cardiac fibroblasts (FB) and myofibroblasts (myoFB) were plated together with non-modified cardiomyocytes (CM) and then paced with periodic illumination. Opto-SICM reveals the extent of FB/myoFB-CM cell-cell contacts and the dynamic changes over time not visible by optical microscopy. FB-CM pairs have lower gap junctional expression of connexin-43 and higher contact dynamism compared to myoFB-CM pairs. The responsiveness of CM to pacing via FB/myoFB depends on the dynamics of the contact but not on the area. The non-responding pairs have higher net cell-cell movement at the contact. These findings are relevant to cardiac disease states, where adverse remodeling leads to abnormal electrical excitation of CM. The Opto-SICM framework can be deployed to offer new insights on cellular and subcellular interactions in various cell types, in real-time.
Collapse
Affiliation(s)
- Qianqian Song
- Imperial College London, Du Cane road, W12 0NN, London, UK
| | | | - Sarah E Schrup
- Department of Biomedical Engineering, George Washington University, Washington, DC, USA
| | | | - Emilia Entcheva
- Department of Biomedical Engineering, George Washington University, Washington, DC, USA.
| | - Julia Gorelik
- Imperial College London, Du Cane road, W12 0NN, London, UK.
| |
Collapse
|
2
|
Poulet C, Sanchez-Alonso J, Swiatlowska P, Mouy F, Lucarelli C, Alvarez-Laviada A, Gross P, Terracciano C, Houser S, Gorelik J. Junctophilin-2 tethers T-tubules and recruits functional L-type calcium channels to lipid rafts in adult cardiomyocytes. Cardiovasc Res 2021; 117:149-161. [PMID: 32053184 PMCID: PMC7797210 DOI: 10.1093/cvr/cvaa033] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 01/08/2020] [Accepted: 02/06/2020] [Indexed: 12/19/2022] Open
Abstract
AIM In cardiomyocytes, transverse tubules (T-tubules) associate with the sarcoplasmic reticulum (SR), forming junctional membrane complexes (JMCs) where L-type calcium channels (LTCCs) are juxtaposed to Ryanodine receptors (RyR). Junctophilin-2 (JPH2) supports the assembly of JMCs by tethering T-tubules to the SR membrane. T-tubule remodelling in cardiac diseases is associated with downregulation of JPH2 expression suggesting that JPH2 plays a crucial role in T-tubule stability. Furthermore, increasing evidence indicate that JPH2 might additionally act as a modulator of calcium signalling by directly regulating RyR and LTCCs. This study aimed at determining whether JPH2 overexpression restores normal T-tubule structure and LTCC function in cultured cardiomyocytes. METHODS AND RESULTS Rat ventricular myocytes kept in culture for 4 days showed extensive T-tubule remodelling with impaired JPH2 localization and relocation of the scaffolding protein Caveolin3 (Cav3) from the T-tubules to the outer membrane. Overexpression of JPH2 restored T-tubule structure and Cav3 relocation. Depletion of membrane cholesterol by chronic treatment with methyl-β-cyclodextrin (MβCD) countered the stabilizing effect of JPH2 overexpression on T-tubules and Cav3. Super-resolution scanning patch-clamp showed that JPH2 overexpression greatly increased the number of functional LTCCs at the plasma membrane. Treatment with MβCD reduced LTCC open probability and activity. Proximity ligation assays showed that MβCD did not affect JPH2 interaction with RyR and the pore-forming LTCC subunit Cav1.2, but strongly impaired JPH2 association with Cav3 and the accessory LTCC subunit Cavβ2. CONCLUSIONS JPH2 promotes T-tubule structural stability and recruits functional LTCCs to the membrane, most likely by directly binding to the channel. Cholesterol is involved in the binding of JPH2 to T-tubules as well as in the modulation of LTCC activity. We propose a model where cholesterol and Cav3 support the assembly of lipid rafts which provide an anchor for JPH2 to form JMCs and a platform for signalling complexes to regulate LTCC activity.
Collapse
Affiliation(s)
- Claire Poulet
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Jose Sanchez-Alonso
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Pamela Swiatlowska
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Florence Mouy
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Carla Lucarelli
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
- Department of Cardiac Surgery, School of Medicine, University of Verona, Piazzale L.A. Scuro 10, 37134 Verona, Italy
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Polina Gross
- Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, 3500 N. Broad St., Philadelphia, PA 19140, USA
| | - Cesare Terracciano
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Steven Houser
- Cardiovascular Research Center, Lewis Katz School of Medicine, Temple University, 3500 N. Broad St., Philadelphia, PA 19140, USA
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, UK
| |
Collapse
|
3
|
Medvedev R, Sanchez-Alonso JL, Alvarez-Laviada A, Rossi S, Dries E, Schorn T, Abdul-Salam VB, Trayanova N, Wojciak-Stothard B, Miragoli M, Faggian G, Gorelik J. Nanoscale Study of Calcium Handling Remodeling in Right Ventricular Cardiomyocytes Following Pulmonary Hypertension. Hypertension 2020; 77:605-616. [PMID: 33356404 DOI: 10.1161/hypertensionaha.120.14858] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pulmonary hypertension is a complex disorder characterized by pulmonary vascular remodeling and right ventricular hypertrophy, leading to right heart failure. The mechanisms underlying this process are not well understood. We hypothesize that the structural remodeling occurring in the cardiomyocytes of the right ventricle affects the cytosolic Ca2+ handling leading to arrhythmias. After 12 days of monocrotaline-induced pulmonary hypertension in rats, epicardial mapping showed electrical remodeling in both ventricles. In myocytes isolated from the hypertensive rats, a combination of high-speed camera and confocal line-scan documented a prolongation of Ca2+ transients along with a higher local Ca2+-release activity. These Ca2+ transients were less synchronous than in controls, likely due to disorganized transverse-axial tubular system. In fact, following pulmonary hypertension, hypertrophied right ventricular myocytes showed significantly reduced number of transverse tubules and increased number of axial tubules; however, Stimulation Emission Depletion microscopy demonstrated that the colocalization of L-type Ca2+ channels and RyR2 (ryanodine receptor 2) remained unchanged. Finally, Stimulation Emission Depletion microscopy and super-resolution scanning patch-clamp analysis uncovered a decrease in the density of active L-type Ca2+ channels in right ventricular myocytes with an elevated open probability of the T-tubule anchored channels. This may represent a general mechanism of how nanoscale structural changes at the early stage of pulmonary hypertension impact on the development of the end stage failing phenotype in the right ventricle.
Collapse
Affiliation(s)
- Roman Medvedev
- From the Dipartimento di Cardiochirurgia, Università degli Studi di Verona, Ospedale Borgo Trento, Italy (R.M., G.F.).,National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.).,Humanitas Clinical and Research Center, Rozzano, Italy (R.M., T.S., M.M.)
| | - Jose L Sanchez-Alonso
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Stefano Rossi
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Parma, Italy (S.R., M.M.)
| | - Eef Dries
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.).,Lab of Experimental Cardiology, University of Leuven, Belgium (E.D.)
| | - Tilo Schorn
- Humanitas Clinical and Research Center, Rozzano, Italy (R.M., T.S., M.M.)
| | - Vahitha B Abdul-Salam
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Natalia Trayanova
- Department of Biomedical Engineering and Alliance for Cardiovascular Diagnostic and Treatment Innovation; Johns Hopkins University; Baltimore, MD (N.T.)
| | - Beata Wojciak-Stothard
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| | - Michele Miragoli
- Dipartimento di Medicina e Chirurgia, Università degli Studi di Parma, Italy (S.R., M.M.)
| | | | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, Du Cane Road, London W12 0NN, United Kingdom (R.M., J.L.S.-A., A.A.-L., E.D., V.B.A.S., B.W.-S., J.G.)
| |
Collapse
|
4
|
Wright PT, Bhogal NK, Diakonov I, Pannell LMK, Perera RK, Bork NI, Schobesberger S, Lucarelli C, Faggian G, Alvarez-Laviada A, Zaccolo M, Kamp TJ, Balijepalli RC, Lyon AR, Harding SE, Nikolaev VO, Gorelik J. Cardiomyocyte Membrane Structure and cAMP Compartmentation Produce Anatomical Variation in β 2AR-cAMP Responsiveness in Murine Hearts. Cell Rep 2019; 23:459-469. [PMID: 29642004 PMCID: PMC5912947 DOI: 10.1016/j.celrep.2018.03.053] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 02/02/2018] [Accepted: 03/13/2018] [Indexed: 01/19/2023] Open
Abstract
Cardiomyocytes from the apex but not the base of the heart increase their contractility in response to β2-adrenoceptor (β2AR) stimulation, which may underlie the development of Takotsubo cardiomyopathy. However, both cell types produce comparable cytosolic amounts of the second messenger cAMP. We investigated this discrepancy using nanoscale imaging techniques and found that, structurally, basal cardiomyocytes have more organized membranes (higher T-tubular and caveolar densities). Local membrane microdomain responses measured in isolated basal cardiomyocytes or in whole hearts revealed significantly smaller and more short-lived β2AR/cAMP signals. Inhibition of PDE4, caveolar disruption by removing cholesterol or genetic deletion of Cav3 eliminated differences in local cAMP production and equilibrated the contractile response to β2AR. We conclude that basal cells possess tighter control of cAMP because of a higher degree of signaling microdomain organization. This provides varying levels of nanostructural control for cAMP-mediated functional effects that orchestrate macroscopic, regional physiological differences within the heart. Cardiomyocyte membrane organization varies in degree between regions of the heart Differences in structural organization affect adrenergic signaling via β2AR Reduced organization allows β2AR-cAMP to influence contractility in myocardial apex Variability in cell structure may allow differential response of heart regions
Collapse
Affiliation(s)
- Peter T Wright
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Navneet K Bhogal
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Ivan Diakonov
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Laura M K Pannell
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Ruwan K Perera
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Nadja I Bork
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Sophie Schobesberger
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK; Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Carla Lucarelli
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK; Department of Cardiac Surgery, University of Verona School of Medicine, Azienda Ospedalieria Universitaria Integrata, Borgo Trento Piazzale A. Stefani, 37126 Verona, Italy
| | - Giuseppe Faggian
- Department of Cardiac Surgery, University of Verona School of Medicine, Azienda Ospedalieria Universitaria Integrata, Borgo Trento Piazzale A. Stefani, 37126 Verona, Italy
| | - Anita Alvarez-Laviada
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK
| | - Timothy J Kamp
- Department of Medicine, University of Wisconsin Madison, 1111 Highland Ave., Madison, WI 53705-2275, USA
| | - Ravi C Balijepalli
- Department of Medicine, University of Wisconsin Madison, 1111 Highland Ave., Madison, WI 53705-2275, USA
| | - Alexander R Lyon
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK; NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London SW7 3AZ, UK
| | - Sian E Harding
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Viacheslav O Nikolaev
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Julia Gorelik
- Myocardial Function, National Heart and Lung Institute, Imperial College London, ICTEM, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK.
| |
Collapse
|
5
|
Schultz F, Swiatlowska P, Alvarez-Laviada A, Sanchez-Alonso JL, Song Q, de Vries AAF, Pijnappels DA, Ongstad E, Braga VMM, Entcheva E, Gourdie RG, Miragoli M, Gorelik J. Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43. FASEB J 2019; 33:10453-10468. [PMID: 31253057 PMCID: PMC6704460 DOI: 10.1096/fj.201802740rr] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Healthy cardiomyocytes are electrically coupled at the intercalated discs by gap junctions. In infarcted hearts, adverse gap-junctional remodeling occurs in the border zone, where cardiomyocytes are chemically and electrically influenced by myofibroblasts. The physical movement of these contacts remains unquantified. Using scanning ion conductance microscopy, we show that intercellular contacts between cardiomyocytes and myofibroblasts are highly dynamic, mainly owing to the edge dynamics (lamellipodia) of the myofibroblasts. Decreasing the amount of functional connexin-43 (Cx43) at the membrane through Cx43 silencing, suppression of Cx43 trafficking, or hypoxia-induced Cx43 internalization attenuates heterocellular contact dynamism. However, we found decreased dynamism and stabilized membrane contacts when cellular coupling was strengthened using 4-phenylbutyrate (4PB). Fluorescent-dye transfer between cells showed that the extent of functional coupling between the 2 cell types correlated with contact dynamism. Intercellular calcein transfer from myofibroblasts to cardiomyocytes is reduced after myofibroblast-specific Cx43 down-regulation. Conversely, 4PB-treated myofibroblasts increased their functional coupling to cardiomyocytes. Consistent with lamellipodia-mediated contacts, latrunculin-B decreases dynamism, lowers physical communication between heterocellular pairs, and reduces Cx43 intensity in contact regions. Our data show that heterocellular cardiomyocyte-myofibroblast contacts exhibit high dynamism. Therefore, Cx43 is a potential target for prevention of aberrant cardiomyocyte coupling and myofibroblast proliferation in the infarct border zone.-Schultz, F., Swiatlowska, P., Alvarez-Laviada, A., Sanchez-Alonso, J. L., Song, Q., de Vries, A. A. F., Pijnappels, D. A., Ongstad, E., Braga, V. M. M., Entcheva, E., Gourdie, R. G., Miragoli, M., Gorelik, J. Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43.
Collapse
Affiliation(s)
- Francisca Schultz
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Pamela Swiatlowska
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | | | | | - Qianqian Song
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | | | - Daniël A. Pijnappels
- Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Emily Ongstad
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Roanoke, Virginia, USA
| | - Vania M. M. Braga
- Department of Respiratory Sciences, Faculty of Medicine, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Emilia Entcheva
- Department of Biomedical Engineering, George Washington University, Washington, DC, USA
| | - Robert G. Gourdie
- Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Roanoke, Virginia, USA
| | - Michele Miragoli
- Humanitas Clinical and Research Center, Milan, Italy;,Department of Medicine and Surgery, University of Parma, Parma, Italy,Correspondence: Department of Medicine and Surgery, University of Parma, Via Gramsci 14, 43124 Parma, Italy. E-mail:
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial College London, London, United Kingdom;,Correspondence: National Heart and Lung Institute, 4th Floor, Imperial Centre for Translational and Experimental Medicine, Imperial College London, Hammersmith Campus, Du Cane Rd., London W12 0NN, United Kingdom. E-mail:
| |
Collapse
|
6
|
Ke HY, Yang HY, Francis AJ, Collins TP, Surendran H, Alvarez-Laviada A, Firth JM, MacLeod KT. Changes in cellular Ca 2+ and Na + regulation during the progression towards heart failure in the guinea pig. J Physiol 2019; 598:1339-1359. [PMID: 30811606 PMCID: PMC7187457 DOI: 10.1113/jp277038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 02/26/2019] [Indexed: 12/19/2022] Open
Abstract
Key points During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
Abstract We followed changes in cardiac myocyte Ca2+ and Na+ regulation from the formation of compensated hypertrophy (CH) until signs of heart failure (HF) are apparent using a trans‐aortic pressure overload (TAC) model. In this model, in vivo fractional shortening (FS) remained constant despite HW:BW ratio increasing by 39% (CH) until HF developed 150 days post‐TAC when FS decreased from 70% to 39%. Using live and fixed fluorescence imaging and electrophysiological techniques, we found an increase in INa,late from –0.34 to –0.59 A F−1 and a decrease in Na+,K+‐ATPase current from 1.09 A F−1 to 0.54 A F−1 during CH. These changes persisted as HF developed (INa,late increased to –0.82 A F−1 and Na+,K+‐ATPase current decreased to 0.51 A F−1). Sarcoplasmic reticulum (SR) Ca2+ content increased during CH then decreased in HF (from 32 to 15 μm l−1) potentially supporting the maintenance of FS in the whole heart and Ca2+ transients in single myocytes during the former stage. We showed using glycoside blockade in healthy myocytes that increases in SR Ca2+ content and Ca2+ transients can be driven by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant in CH but decreases (τ for SERCA‐mediated Ca2+ removal changed from 6.3 to 3.0 s−1) in HF. In HF there was an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment. During compensated hypertrophy in vivo fractional shortening (FS) remains constant until heart failure (HF) develops, when FS decreases from 70% to 39%. Compensated hypertrophy is accompanied by an increase in INa,late and a decrease in Na+,K+‐ATPase current. These changes persist as HF develops. SR Ca2+ content increases during compensated hypertrophy then decreases in HF. In healthy cells, increases in SR Ca2+ content and Ca2+ transients can be achieved by the same amount of inhibition of the Na+,K+‐ATPase as measured in the diseased cells. SERCA function remains constant during compensated hypertrophy then decreases in HF, when there is also an increase in spark frequency and spark‐mediated Ca2+ leak. We suggest an increase in INa,late and a decrease in Na+,K+‐ATPase current and function alters the balance of Ca2+ flux mediated by the Na+/Ca2+ exchange that limits early contractile impairment.
Collapse
Affiliation(s)
- H-Y Ke
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - H-Y Yang
- Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan (ROC)
| | - A J Francis
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - T P Collins
- The Wellcome Trust, Gibbs Building, 215 Euston Road, London, NW1 2BE, UK
| | - H Surendran
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - A Alvarez-Laviada
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - J M Firth
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - K T MacLeod
- National Heart and Lung Institute, Imperial College, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| |
Collapse
|
7
|
Wright PT, Sanchez-Alonso JL, Lucarelli C, Alvarez-Laviada A, Poulet CE, Bello SO, Faggian G, Terracciano CM, Gorelik J. Partial Mechanical Unloading of the Heart Disrupts L-Type Calcium Channel and Beta-Adrenoceptor Signaling Microdomains. Front Physiol 2018; 9:1302. [PMID: 30283354 PMCID: PMC6157487 DOI: 10.3389/fphys.2018.01302] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 08/29/2018] [Indexed: 12/16/2022] Open
Abstract
Introduction: We investigated the effect of partial mechanical unloading (PMU) of the heart on the physiology of calcium and beta-adrenoceptor-cAMP (βAR-cAMP) microdomains. Previous studies have investigated PMU using a model of heterotopic-heart and lung transplantation (HTHAL). These studies have demonstrated that PMU disrupts the structure of cardiomyocytes and calcium handling. We sought to understand these processes by studying L-Type Calcium Channel (LTCC) activity and sub-type-specific βAR-cAMP signaling within cardiomyocyte membrane microdomains. Method: We utilized an 8-week model of HTHAL, whereby the hearts of syngeneic Lewis rats were transplanted into the abdomens of randomly assigned cage mates. A pronounced atrophy was observed in hearts after HTHAL. Cardiomyocytes were isolated via enzymatic perfusion. We utilized Förster Resonance Energy Transfer (FRET) based cAMP-biosensors and scanning ion conductance microscopy (SICM) based methodologies to study localization of LTCC and βAR-cAMP signaling. Results: β2AR-cAMP responses measured by FRET in the cardiomyocyte cytosol were reduced by PMU (loaded 28.51 ± 7.18% vs. unloaded 10.84 ± 3.27% N,n 4/10-13 mean ± SEM ∗p < 0.05). There was no effect of PMU on β2AR-cAMP signaling in RII_Protein Kinase A domains. β1AR-cAMP was unaffected by PMU in either microdomain. Consistent with this SICM/FRET analysis demonstrated that β2AR-cAMP was specifically reduced in t-tubules (TTs) after PMU (loaded TT 0.721 ± 0.106% vs. loaded crest 0.104 ± 0.062%, unloaded TT 0.112 ± 0.072% vs. unloaded crest 0.219 ± 0.084% N,n 5/6-9 mean ± SEM ∗∗p < 0.01, ∗∗∗p < 0.001 vs. loaded TT). By comparison β1AR-cAMP responses in either TT or sarcolemmal crests were unaffected by the PMU. LTCC occurrence and open probability (Po) were reduced by PMU (loaded TT Po 0.073 ± 0.011% vs. loaded crest Po 0.027 ± 0.006% N,n 5/18-26 mean ± SEM ∗p < 0.05) (unloaded TT 0.0350 ± 0.003% vs. unloaded crest Po 0.025 N,n 5/20-30 mean ± SEM NS #p < 0.05 unloaded vs. loaded TT). We discovered that PMU had reduced the association between Caveolin-3, Junctophilin-2, and Cav1.2. Discussion: PMU suppresses’ β2AR-cAMP and LTCC activity. When activated, the signaling of β2AR-cAMP and LTCC become more far-reaching after PMU. We suggest that a situation of ‘suppression/decompartmentation’ is elicited by the loss of refined cardiomyocyte structure following PMU. As PMU is a component of modern device therapy for heart failure this study has clinical ramifications and raises important questions for regenerative medicine.
Collapse
Affiliation(s)
- Peter T Wright
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Jose L Sanchez-Alonso
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Carla Lucarelli
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom.,Department of Cardiac Surgery, School of Medicine, University of Verona, Verona, Italy
| | - Anita Alvarez-Laviada
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Claire E Poulet
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Sean O Bello
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Giuseppe Faggian
- Department of Cardiac Surgery, School of Medicine, University of Verona, Verona, Italy
| | - Cesare M Terracciano
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| | - Julia Gorelik
- Myocardial Function, National Heart and Lung Institute, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, London, United Kingdom
| |
Collapse
|
8
|
Veeraraghavan R, Hoeker GS, Alvarez-Laviada A, Hoagland D, Wan X, King DR, Sanchez-Alonso J, Chen C, Jourdan J, Isom LL, Deschenes I, Smyth JW, Gorelik J, Poelzing S, Gourdie RG. The adhesion function of the sodium channel beta subunit (β1) contributes to cardiac action potential propagation. eLife 2018; 7:37610. [PMID: 30106376 PMCID: PMC6122953 DOI: 10.7554/elife.37610] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/06/2018] [Indexed: 12/22/2022] Open
Abstract
Computational modeling indicates that cardiac conduction may involve ephaptic coupling – intercellular communication involving electrochemical signaling across narrow extracellular clefts between cardiomyocytes. We hypothesized that β1(SCN1B) –mediated adhesion scaffolds trans-activating NaV1.5 (SCN5A) channels within narrow (<30 nm) perinexal clefts adjacent to gap junctions (GJs), facilitating ephaptic coupling. Super-resolution imaging indicated preferential β1 localization at the perinexus, where it co-locates with NaV1.5. Smart patch clamp (SPC) indicated greater sodium current density (INa) at perinexi, relative to non-junctional sites. A novel, rationally designed peptide, βadp1, potently and selectively inhibited β1-mediated adhesion, in electric cell-substrate impedance sensing studies. βadp1 significantly widened perinexi in guinea pig ventricles, and selectively reduced perinexal INa, but not whole cell INa, in myocyte monolayers. In optical mapping studies, βadp1 precipitated arrhythmogenic conduction slowing. In summary, β1-mediated adhesion at the perinexus facilitates action potential propagation between cardiomyocytes, and may represent a novel target for anti-arrhythmic therapies.
Collapse
Affiliation(s)
- Rengasayee Veeraraghavan
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Gregory S Hoeker
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | | | - Daniel Hoagland
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Xiaoping Wan
- Heart and Vascular Research Center, MetroHealth Medical Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - D Ryan King
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Graduate Program in Translational Biology, Medicine and Health, Virginia Tech, Virginia, United States
| | - Jose Sanchez-Alonso
- Department of Myocardial Function, Imperial College London, London, United Kingdom
| | - Chunling Chen
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States
| | - Jane Jourdan
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, United States
| | - Isabelle Deschenes
- Heart and Vascular Research Center, MetroHealth Medical Center, Department of Medicine, Case Western Reserve University, Cleveland, United States.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Unites States
| | - James W Smyth
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biological Sciences, College of Science, Blacksburg, United States
| | - Julia Gorelik
- Department of Myocardial Function, Imperial College London, London, United Kingdom
| | - Steven Poelzing
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Blacksburg, United States
| | - Robert G Gourdie
- Virginia Tech Carilion Research Institute, Virginia Polytechnic University, Roanoke, United States.,School of Medicine, Virginia Polytechnic University, Roanoke, United States.,Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Blacksburg, United States
| |
Collapse
|
9
|
Alvarez-Laviada A, Veeraraghavan R, Braga V, Gourdie R, Gorelik J. Dissecting Function and Distribution of Sodium Channels and GAP Junctional Proteins using Super-Resolution Patch-Clamp. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
10
|
Firth JM, Yang HY, Francis AJ, Alvarez-Laviada A, MacLeod KT. The Effect of Oestrogen on Ca2+ and Na+ Regulation in Heart Failure. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
11
|
Adeyemi O, Alvarez-Laviada A, Schultz F, Ibrahim E, Trauner M, Williamson C, Glukhov AV, Gorelik J. Ursodeoxycholic acid prevents ventricular conduction slowing and arrhythmia by restoring T-type calcium current in fetuses during cholestasis. PLoS One 2017; 12:e0183167. [PMID: 28934223 PMCID: PMC5608194 DOI: 10.1371/journal.pone.0183167] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 07/31/2017] [Indexed: 12/27/2022] Open
Abstract
Background Increased maternal serum bile acid concentrations in intrahepatic cholestasis of pregnancy (ICP) are associated with fetal cardiac arrhythmias. Ursodeoxycholic acid (UDCA) has been shown to demonstrate anti-arrhythmic properties via preventing ICP-associated cardiac conduction slowing and development of reentrant arrhythmias, although the cellular mechanism is still being elucidated. Methods High-resolution fluorescent optical mapping of electrical activity and electrocardiogram measurements were used to characterize effects of UDCA on one-day-old neonatal and adult female Langendorff-perfused rat hearts. ICP was modelled by perfusion of taurocholic acid (TC, 400μM). Whole-cell calcium currents were recorded from neonatal rat and human fetal cardiomyocytes. Results TC significantly prolonged the PR interval by 11.0±3.5% (P<0.05) and slowed ventricular conduction velocity (CV) by 38.9±5.1% (P<0.05) exclusively in neonatal and not in maternal hearts. A similar CV decline was observed with the selective T-type calcium current (ICa,T) blocker mibefradil 1μM (23.0±6.2%, P<0.05), but not with the L-type calcium current (ICa,L) blocker nifedipine 1μM (6.9±6.6%, NS). The sodium channel blocker lidocaine (30μM) reduced CV by 60.4±4.5% (P<0.05). UDCA co-treatment was protective against CV slowing induced by TC and mibefradil, but not against lidocaine. UDCA prevented the TC-induced reduction in the ICa,T density in both isolated human fetal (−10.2±1.5 versus −5.5±0.9 pA/pF, P<0.05) and neonatal rat ventricular myocytes (−22.3±1.1 versus −9.6±0.8 pA/pF, P<0.0001), whereas UDCA had limited efficacy on the ICa,L. Conclusion Our findings demonstrate that ICa,T plays a significant role in ICP-associated fetal cardiac conduction slowing and arrhythmogenesis, and is an important component of the fetus-specific anti-arrhythmic activity of UDCA.
Collapse
Affiliation(s)
- Oladipupo Adeyemi
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Anita Alvarez-Laviada
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Francisca Schultz
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | - Effendi Ibrahim
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- Faculty of Medicine, MARA Technology University, Sungai Buloh, Malaysia
| | - Michael Trauner
- Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Catherine Williamson
- Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
- Women's Health Academic Centre, King's College London, London, United Kingdom
| | - Alexey V. Glukhov
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, United States of America
- * E-mail: (JG); (AG)
| | - Julia Gorelik
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, London, United Kingdom
- * E-mail: (JG); (AG)
| |
Collapse
|
12
|
Rowlands CT, Owen T, Lawal S, Cao S, Pandey SS, Yang HY, Song W, Wilkinson R, Alvarez-Laviada A, Gehmlich K, Marston SB, MacLeod KT. Age- and strain-related aberrant Ca 2+ release is associated with sudden cardiac death in the ACTC E99K mouse model of hypertrophic cardiomyopathy. Am J Physiol Heart Circ Physiol 2017; 313:H1213-H1226. [PMID: 28887330 DOI: 10.1152/ajpheart.00244.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patients with hypertrophic cardiomyopathy, particularly young adults, can die from arrhythmia, but the mechanism underlying abnormal rhythm formation remains unknown. C57Bl6 × CBA/Ca mice carrying a cardiac actin ( ACTC) E99K (Glu99Lys) mutation reproduce many aspects of human hypertrophic cardiomyopathy, including increased myofilament Ca2+ sensitivity and sudden death in a proportion (up to 40%) of young (28-40 day old) animals. We studied the hearts of transgenic (TG; ACTC E99K) mice and their non-TG (NTG) littermates when they were in their vulnerable period (28-40 days old) and when they were adult (8-12 wk old). Ventricular myocytes were isolated from the hearts of TG and NTG mice at these two time points. We also examined the hearts of mice that died suddenly (SCD). SCD animals had approximately four times more collagen compared with age-matched NTG mice, yet myocyte cell size was normal. Young TG mice had double the collagen content of NTG mice. Contraction and Ca2+ transients were greater in cells from young TG mice compared with their NTG littermates but not in cells from adult mice (TG or NTG). Cells from young TG mice had a greater propensity for Ca2+ waves than NTG littermates, and, despite similar sarcoplasmic reticulum Ca2+ content, a proportion of these cells had larger Ca2+ spark mass. We found that the probability of SCD in young TG mice was increased when the mutation was expressed in animals with a CBA/Ca2+ background and almost eliminated in mice bred on a C57Bl6 background. The latter TG mice had normal cellular Ca2+ homeostasis. NEW & NOTEWORTHY Mice with the actin Glu99Lys hypertrophic cardiomyopathy mutation ( ACTC E99K) are prone to sudden cardiac death around 40 days, associated with increased Ca2+ transients, spark mass, and fibrosis. However, adult survivors have normal Ca2+ transients and spark density accompanied by hypertrophy. Penetrance of the sudden cardiac death phenotype depends on the genetic background of the mouse. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/calcium-regulation-in-e99k-mouse-heart/ .
Collapse
Affiliation(s)
- Christina T Rowlands
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Thomas Owen
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Saheed Lawal
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Shuangyi Cao
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Samata S Pandey
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Hsiang-Yu Yang
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Weihua Song
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Ross Wilkinson
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Anita Alvarez-Laviada
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Katja Gehmlich
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Steven B Marston
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| | - Kenneth T MacLeod
- National Heart & Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College, Hammersmith Hospital , London , United Kingdom
| |
Collapse
|
13
|
Yang HY, Firth JM, Francis AJ, Alvarez-Laviada A, MacLeod KT. Effect of ovariectomy on intracellular Ca 2+ regulation in guinea pig cardiomyocytes. Am J Physiol Heart Circ Physiol 2017; 313:H1031-H1043. [PMID: 28778911 DOI: 10.1152/ajpheart.00249.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 07/17/2017] [Accepted: 08/02/2017] [Indexed: 01/30/2023]
Abstract
This study addressed the hypothesis that long-term deficiency of ovarian hormones after ovariectomy (OVx) alters cellular Ca2+-handling mechanisms in the heart, resulting in the formation of a proarrhythmic substrate. It also tested whether estrogen supplementation to OVx animals reverses any alterations to cardiac Ca2+ handling and rescues proarrhythmic behavior. OVx or sham operations were performed on female guinea pigs using appropriate anesthetic and analgesic regimes. Pellets containing 17β-estradiol (1 mg, 60-day release) were placed subcutaneously in selected OVx animals (OVx + E). Cardiac myocytes were enzymatically isolated, and electrophysiological measurements were conducted with a switch-clamp system. In fluo-4-loaded cells, Ca2+ transients were 20% larger, and fractional sarcoplasmic reticulum (SR) Ca2+ release was 7% greater in the OVx group compared with the sham group. Peak L-type Ca2+ current was 16% larger in OVx myocytes with channel inactivation shifting to more positive membrane potentials, creating a larger "window" current. SR Ca2+ stores were 22% greater in the OVx group, and these cells showed a higher frequency of Ca2+ sparks and waves and shorter wave-free intervals. OVx myocytes showed higher frequencies of early afterdepolarizations, and a greater percentage of these cells showed delayed afterdepolarizations after exposure to isoprenaline compared with sham myocytes. The altered Ca2+ regulation occurring in the OVx group was not observed in the OVx + E group. These findings suggest that long-term deprivation of ovarian hormones in guinea pigs lead to changes in myocyte Ca2+-handling mechanisms that are considered proarrhythmogenic. 17β-Estradiol replacement prevented these adverse effects.NEW & NOTEWORTHY Ovariectomized guinea pig cardiomyocytes have higher frequencies of Ca2+ waves, and isoprenaline-challenged cells display more early afterdepolarizations, delayed afterdepolarizations, and extra beats compared with sham myocytes. These alterations to Ca2+ regulation were not observed in myocytes from ovariectomized guinea pigs supplemented with 17β-estradiol, suggesting that ovarian hormone deficiency modifies cardiac Ca2+ regulation, potentially creating proarrhythmic substrates.
Collapse
Affiliation(s)
- Hsiang-Yu Yang
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and.,Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defence Medical Center, Taipei, Taiwan
| | - Jahn M Firth
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Alice J Francis
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Kenneth T MacLeod
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| |
Collapse
|
14
|
Yang HY, Alvarez-Laviada A, Firth JM, Francis AJ, MacLeod KT. The Effect of Ovariectomy on Calcium (Ca 2+ ) Handling in Guinea Pig Cardiomyocytes. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|
15
|
Bannister ML, Alvarez-Laviada A, Thomas NL, Mason SA, Coleman S, du Plessis CL, Moran AT, Neill-Hall D, Osman H, Bagley MC, MacLeod KT, George CH, Williams AJ. Effect of flecainide derivatives on sarcoplasmic reticulum calcium release suggests a lack of direct action on the cardiac ryanodine receptor. Br J Pharmacol 2016; 173:2446-59. [PMID: 27237957 PMCID: PMC4945764 DOI: 10.1111/bph.13521] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 05/16/2016] [Accepted: 05/17/2016] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Flecainide is a use-dependent blocker of cardiac Na(+) channels. Mechanistic analysis of this block showed that the cationic form of flecainide enters the cytosolic vestibule of the open Na(+) channel. Flecainide is also effective in the treatment of catecholaminergic polymorphic ventricular tachycardia but, in this condition, its mechanism of action is contentious. We investigated how flecainide derivatives influence Ca(2) (+) -release from the sarcoplasmic reticulum through the ryanodine receptor channel (RyR2) and whether this correlates with their effectiveness as blockers of Na(+) and/or RyR2 channels. EXPERIMENTAL APPROACH We compared the ability of fully charged (QX-FL) and neutral (NU-FL) derivatives of flecainide to block individual recombinant human RyR2 channels incorporated into planar phospholipid bilayers, and their effects on the properties of Ca(2) (+) sparks in intact adult rat cardiac myocytes. KEY RESULTS Both QX-FL and NU-FL were partial blockers of the non-physiological cytosolic to luminal flux of cations through RyR2 channels but were significantly less effective than flecainide. None of the compounds influenced the physiologically relevant luminal to cytosol cation flux through RyR2 channels. Intracellular flecainide or QX-FL, but not NU-FL, reduced Ca(2) (+) spark frequency. CONCLUSIONS AND IMPLICATIONS Given its inability to block physiologically relevant cation flux through RyR2 channels, and its lack of efficacy in blocking the cytosolic-to-luminal current, the effect of QX-FL on Ca(2) (+) sparks is likely, by analogy with flecainide, to result from Na(+) channel block. Our data reveal important differences in the interaction of flecainide with sites in the cytosolic vestibules of Na(+) and RyR2 channels.
Collapse
Affiliation(s)
- Mark L Bannister
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| | - Anita Alvarez-Laviada
- Myocardial Function Section, National Heart and Lung Institute, Imperial College London, London, UK
| | - N Lowri Thomas
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| | - Sammy A Mason
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| | - Sharon Coleman
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| | - Christo L du Plessis
- Department of Chemistry, School of Life Sciences, University of Sussex, Brighton, UK
| | - Abbygail T Moran
- Department of Chemistry, School of Life Sciences, University of Sussex, Brighton, UK
| | - David Neill-Hall
- Department of Chemistry, School of Life Sciences, University of Sussex, Brighton, UK
| | - Hasnah Osman
- School of Chemical Sciences, Universiti Sains Malaysia, Penang, Malaysia
| | - Mark C Bagley
- Department of Chemistry, School of Life Sciences, University of Sussex, Brighton, UK
| | - Kenneth T MacLeod
- Myocardial Function Section, National Heart and Lung Institute, Imperial College London, London, UK
| | - Christopher H George
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| | - Alan J Williams
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff, UK
| |
Collapse
|
16
|
Alvarez-Laviada A, Bannister ML, Lowri Thomas N, Mason SA, du Plessis CL, Moran AT, Neil-Hall D, Osman H, Bagley MC, McLeod KT, George CH, Williams AJ. Effect of Flecainide Derivatives on Sarcoplasmic Reticulum Ca2+ Release Confirms a Lack of Direct Action on the Cardiac Ryanodine Receptor. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
17
|
Schultz F, Hasan A, Alvarez-Laviada A, Miragoli M, Bhogal N, Wells S, Poulet C, Chambers J, Williamson C, Gorelik J. The protective effect of ursodeoxycholic acid in an in vitro model of the human fetal heart occurs via targeting cardiac fibroblasts. Prog Biophys Mol Biol 2016; 120:149-63. [PMID: 26777584 DOI: 10.1016/j.pbiomolbio.2016.01.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/05/2016] [Accepted: 01/06/2016] [Indexed: 12/27/2022]
Abstract
Bile acids are elevated in the blood of women with intrahepatic cholestasis of pregnancy (ICP) and this may lead to fetal arrhythmia, fetal hypoxia and potentially fetal death in utero. The bile acid taurocholic acid (TC) causes abnormal calcium dynamics and contraction in neonatal rat cardiomyocytes. Ursodeoxycholic acid (UDCA), a drug clinically used to treat ICP, prevents adverse effects of TC. During development, the fetus is in a state of relative hypoxia. Although this is essential for the development of the heart and vasculature, resident fibroblasts can transiently differentiate into myofibroblasts and form gap junctions with cardiomyocytes in vitro, resulting in cardiomyocyte depolarization. We expanded on previously published work using an in vitro hypoxia model to investigate the differentiation of human fetal fibroblasts into myofibroblasts. Recent evidence shows that potassium channels are involved in maintaining the membrane potential of ventricular fibroblasts and that ATP-dependent potassium (KATP) channel subunits are expressed in cultured fibroblasts. KATP channels are a valuable target as they are thought to have a cardioprotective role during ischaemic and hypoxic conditions. We investigated whether UDCA could modulate fibroblast membrane potential. We established the isolation and culture of human fetal cardiomyocytes and fibroblasts to investigate the effect of hypoxia, TC and UDCA on human fetal cardiac cells. UDCA hyperpolarized myofibroblasts and prevented TC-induced depolarisation, possibly through the activation of KATP channels that are expressed in cultured fibroblasts. Also, similar to the rat model, UDCA can counteract TC-induced calcium abnormalities in human fetal cultures of cardiomyocytes and myofibroblasts. Under normoxic conditions, we found a higher number of myofibroblasts in cultures derived from human fetal hearts compared to cells isolated from neonatal rat hearts, indicating a possible increased number of myofibroblasts in human fetal hearts. Hypoxia further increased the number of human fetal and rat neonatal myofibroblasts. However, chronically administered UDCA reduced the number of myofibroblasts and prevented hypoxia-induced depolarisation. In conclusion, our results show that the protective effect of UDCA involves both the reduction of fibroblast differentiation into myofibroblasts, and hyperpolarisation of myofibroblasts, most likely through the stimulation of potassium channels, i.e. KATP channels. This could be important in validating UDCA as an antifibrotic and antiarrhythmic drug for treatment of failing hearts and fetal arrhythmia.
Collapse
Affiliation(s)
- Francisca Schultz
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK; Institute of Reproductive and Developmental Biology, Imperial College London, London, UK
| | - Alveera Hasan
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Michele Miragoli
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK; Humanitas Clinical and Research Institute, Rozzano, Italy
| | - Navneet Bhogal
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Sarah Wells
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Claire Poulet
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK
| | - Jenny Chambers
- Institute of Reproductive and Developmental Biology, Imperial College London, London, UK; Women's Health Academic Centre, King's College London, London, United Kingdom
| | - Catherine Williamson
- Institute of Reproductive and Developmental Biology, Imperial College London, London, UK; Women's Health Academic Centre, King's College London, London, United Kingdom
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, UK.
| |
Collapse
|
18
|
Glukhov AV, Balycheva M, Sanchez-Alonso JL, Ilkan Z, Alvarez-Laviada A, Bhogal N, Diakonov I, Schobesberger S, Sikkel MB, Bhargava A, Faggian G, Punjabi PP, Houser SR, Gorelik J. Direct Evidence for Microdomain-Specific Localization and Remodeling of Functional L-Type Calcium Channels in Rat and Human Atrial Myocytes. Circulation 2015; 132:2372-84. [PMID: 26450916 PMCID: PMC4689179 DOI: 10.1161/circulationaha.115.018131] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 10/02/2015] [Indexed: 12/27/2022]
Abstract
Supplemental Digital Content is available in the text. Distinct subpopulations of L-type calcium channels (LTCCs) with different functional properties exist in cardiomyocytes. Disruption of cellular structure may affect LTCC in a microdomain-specific manner and contribute to the pathophysiology of cardiac diseases, especially in cells lacking organized transverse tubules (T-tubules) such as atrial myocytes (AMs).
Collapse
Affiliation(s)
- Alexey V Glukhov
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Marina Balycheva
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Jose L Sanchez-Alonso
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Zeki Ilkan
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Anita Alvarez-Laviada
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Navneet Bhogal
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Ivan Diakonov
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Sophie Schobesberger
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Markus B Sikkel
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Anamika Bhargava
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Giuseppe Faggian
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Prakash P Punjabi
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Steven R Houser
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.)
| | - Julia Gorelik
- From Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial College London, United Kingdom (A.V.G., M.B., J.L.S.-A., Z.I., A.A.-L., N.B., I.D., S.S., M.B.S., A.B., P.P.P., J.G.); University of Verona, School of Medicine, Verona, Italy (M.B., G.F.); Department of Cardiothoracic Surgery, Hammersmith Hospital, National Heart and Lung Institute, Imperial College London, United Kingdom (P.P.P.); and Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA (S.R.H.).
| |
Collapse
|
19
|
Alvarez-Laviada A, Sikkel M, Al-khayatt B, MacLeod KT. Effects of Flecainide and Ranolazine on Intracellular Calcium Handling and Sarcolemmal Sodium Current. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.1865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
20
|
Ke HY, Collins TP, Alvarez-Laviada A, Rowlands C, MacLeod KT. Na/K ATPase Function Declines Before Changes to Calcium Handling in a Guinea-Pig Model of Progressive Heart Failure. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
|
21
|
Kadurin I, Alvarez-Laviada A, Ng SFJ, Walker-Gray R, D'Arco M, Fadel MG, Pratt WS, Dolphin AC. Calcium currents are enhanced by α2δ-1 lacking its membrane anchor. J Biol Chem 2012; 287:33554-66. [PMID: 22869375 PMCID: PMC3460456 DOI: 10.1074/jbc.m112.378554] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The accessory α(2)δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α(2) and δ. All α(2)δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α(2)δ subunits, we have now examined the properties of α(2)δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α(2)δ-1ΔC-term). We find that the majority of α(2)δ-1ΔC-term is soluble and secreted into the medium, but unexpectedly, some of the protein remains associated with detergent-resistant membranes, also termed lipid rafts, and is extrinsically bound to the plasma membrane. Furthermore, heterologous co-expression of α(2)δ-1ΔC-term with Ca(V)2.1/β1b results in a substantial enhancement of the calcium channel currents, albeit less than that produced by wild-type α(2)δ-1. These results call into question the role of membrane anchoring of α(2)δ subunits for calcium current enhancement.
Collapse
Affiliation(s)
- Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
| | | | | | | | | | | | | | | |
Collapse
|