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Tarasov KV, Chakir K, Riordon DR, Lyashkov AE, Ahmet I, Perino MG, Silvester AJ, Zhang J, Wang M, Lukyanenko YO, Qu JH, Barrera MCR, Juhaszova M, Tarasova YS, Ziman B, Telljohann R, Kumar V, Ranek M, Lammons J, Bychkov R, de Cabo R, Jun S, Keceli G, Gupta A, Yang D, Aon MA, Adamo L, Morrell CH, Otu W, Carroll C, Chambers S, Paolocci N, Huynh T, Pacak K, Weiss R, Field L, Sollott SJ, Lakatta EG. A remarkable adaptive paradigm of heart performance and protection emerges in response to marked cardiac-specific overexpression of ADCY8. eLife 2022; 11:80949. [PMID: 36515265 PMCID: PMC9822292 DOI: 10.7554/elife.80949] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 12/08/2022] [Indexed: 12/15/2022] Open
Abstract
Adult (3 month) mice with cardiac-specific overexpression of adenylyl cyclase (AC) type VIII (TGAC8) adapt to an increased cAMP-induced cardiac workload (~30% increases in heart rate, ejection fraction and cardiac output) for up to a year without signs of heart failure or excessive mortality. Here, we show classical cardiac hypertrophy markers were absent in TGAC8, and that total left ventricular (LV) mass was not increased: a reduced LV cavity volume in TGAC8 was encased by thicker LV walls harboring an increased number of small cardiac myocytes, and a network of small interstitial proliferative non-cardiac myocytes compared to wild type (WT) littermates; Protein synthesis, proteosome activity, and autophagy were enhanced in TGAC8 vs WT, and Nrf-2, Hsp90α, and ACC2 protein levels were increased. Despite increased energy demands in vivo LV ATP and phosphocreatine levels in TGAC8 did not differ from WT. Unbiased omics analyses identified more than 2,000 transcripts and proteins, comprising a broad array of biological processes across multiple cellular compartments, which differed by genotype; compared to WT, in TGAC8 there was a shift from fatty acid oxidation to aerobic glycolysis in the context of increased utilization of the pentose phosphate shunt and nucleotide synthesis. Thus, marked overexpression of AC8 engages complex, coordinate adaptation "circuity" that has evolved in mammalian cells to defend against stress that threatens health or life (elements of which have already been shown to be central to cardiac ischemic pre-conditioning and exercise endurance cardiac conditioning) that may be of biological significance to allow for proper healing in disease states such as infarction or failure of the heart.
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Affiliation(s)
- Kirill V Tarasov
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Khalid Chakir
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Daniel R Riordon
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Alexey E Lyashkov
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Ismayil Ahmet
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Maria Grazia Perino
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Allwin Jennifa Silvester
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Jing Zhang
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Mingyi Wang
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Yevgeniya O Lukyanenko
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Jia-Hua Qu
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Miguel Calvo-Rubio Barrera
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Magdalena Juhaszova
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Yelena S Tarasova
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Bruce Ziman
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Richard Telljohann
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Vikas Kumar
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Mark Ranek
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - John Lammons
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Rostislav Bychkov
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Rafael de Cabo
- Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Seungho Jun
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Gizem Keceli
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Ashish Gupta
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Miguel A Aon
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Luigi Adamo
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Christopher H Morrell
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Walter Otu
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Cameron Carroll
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Shane Chambers
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Nazareno Paolocci
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Thanh Huynh
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Karel Pacak
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of HealthBethesdaUnited States
| | - Robert Weiss
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Loren Field
- Kraennert Institute of Cardiology, Indiana University School of MedicineIdianapolisUnited States
| | - Steven J Sollott
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of HealthBaltimoreUnited States
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Sirenko ST, Zahanich I, Li Y, Lukyanenko YO, Lyashkov AE, Ziman BD, Tarasov KV, Younes A, Riordon DR, Tarasova YS, Yang D, Vinogradova TM, Maltsev VA, Lakatta EG. Phosphoprotein Phosphatase 1 but Not 2A Activity Modulates Coupled-Clock Mechanisms to Impact on Intrinsic Automaticity of Sinoatrial Nodal Pacemaker Cells. Cells 2021; 10:cells10113106. [PMID: 34831329 PMCID: PMC8623309 DOI: 10.3390/cells10113106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/02/2021] [Accepted: 11/05/2021] [Indexed: 12/02/2022] Open
Abstract
Spontaneous AP (action potential) firing of sinoatrial nodal cells (SANC) is critically dependent on protein kinase A (PKA) and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent protein phosphorylation, which are required for the generation of spontaneous, diastolic local Ca2+ releases (LCRs). Although phosphoprotein phosphatases (PP) regulate protein phosphorylation, the expression level of PPs and phosphatase inhibitors in SANC and the impact of phosphatase inhibition on the spontaneous LCRs and other players of the oscillatory coupled-clock system is unknown. Here, we show that rabbit SANC express both PP1, PP2A, and endogenous PP inhibitors I-1 (PPI-1), dopamine and cyclic adenosine 3′,5′-monophosphate (cAMP)-regulated phosphoprotein (DARPP-32), kinase C-enhanced PP1 inhibitor (KEPI). Application of Calyculin A, (CyA), a PPs inhibitor, to intact, freshly isolated single SANC: (1) significantly increased phospholamban (PLB) phosphorylation (by 2–3-fold) at both CaMKII-dependent Thr17 and PKA-dependent Ser16 sites, in a time and concentration dependent manner; (2) increased ryanodine receptor (RyR) phosphorylation at the Ser2809 site; (3) substantially increased sarcoplasmic reticulum (SR) Ca2+ load; (4) augmented L-type Ca2+ current amplitude; (5) augmented LCR’s characteristics and decreased LCR period in intact and permeabilized SANC, and (6) increased the spontaneous basal AP firing rate. In contrast, the selective PP2A inhibitor okadaic acid (100 nmol/L) had no significant effect on spontaneous AP firing, LCR parameters, or PLB phosphorylation. Application of purified PP1 to permeabilized SANC suppressed LCR, whereas purified PP2A had no effect on LCR characteristics. Our numerical model simulations demonstrated that PP inhibition increases AP firing rate via a coupled-clock mechanism, including respective increases in the SR Ca2+ pumping rate, L-type Ca2+ current, and Na+/Ca2+-exchanger current. Thus, PP1 and its endogenous inhibitors modulate the basal spontaneous firing rate of cardiac pacemaker cells by suppressing SR Ca2+ cycling protein phosphorylation, the SR Ca2+ load and LCRs, and L-type Ca2+ current.
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Yang D, Morrell CH, Lyashkov AE, Tagirova Sirenko S, Zahanich I, Yaniv Y, Vinogradova TM, Ziman BD, Maltsev VA, Lakatta EG. Ca 2+ and Membrane Potential Transitions During Action Potentials Are Self-Similar to Each Other and to Variability of AP Firing Intervals Across the Broad Physiologic Range of AP Intervals During Autonomic Receptor Stimulation. Front Physiol 2021; 12:612770. [PMID: 34566668 PMCID: PMC8456031 DOI: 10.3389/fphys.2021.612770] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [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: 09/30/2020] [Accepted: 06/02/2021] [Indexed: 12/02/2022] Open
Abstract
Ca2+ and V m transitions occurring throughout action potential (AP) cycles in sinoatrial nodal (SAN) cells are cues that (1) not only regulate activation states of molecules operating within criticality (Ca2+ domain) and limit-cycle (V m domain) mechanisms of a coupled-clock system that underlies SAN cell automaticity, (2) but are also regulated by the activation states of the clock molecules they regulate. In other terms, these cues are both causes and effects of clock molecular activation (recursion). Recently, we demonstrated that Ca2+ and V m transitions during AP cycles in single SAN cells isolated from mice, guinea pigs, rabbits, and humans are self-similar (obey a power law) and are also self-similar to trans-species AP firing intervals (APFIs) of these cells in vitro, to heart rate in vivo, and to body mass. Neurotransmitter stimulation of β-adrenergic receptor or cholinergic receptor-initiated signaling in SAN cells modulates their AP firing rate and rhythm by impacting on the degree to which SAN clocks couple to each other, creating the broad physiologic range of SAN cell mean APFIs and firing interval variabilities. Here we show that Ca2+ and V m domain kinetic transitions (time to AP ignition in diastole and 90% AP recovery) occurring within given AP, the mean APFIs, and APFI variabilities within the time series of APs in 230 individual SAN cells are self-similar (obey power laws). In other terms, these long-range correlations inform on self-similar distributions of order among SAN cells across the entire broad physiologic range of SAN APFIs, regardless of whether autonomic receptors of these cells are stimulated or not and regardless of the type (adrenergic or cholinergic) of autonomic receptor stimulation. These long-range correlations among distributions of Ca2+ and V m kinetic functions that regulate SAN cell clock coupling during each AP cycle in different individual, isolated SAN cells not in contact with each other. Our numerical model simulations further extended our perspectives to the molecular scale and demonstrated that many ion currents also behave self-similar across autonomic states. Thus, to ensure rapid flexibility of AP firing rates in response to different types and degrees of autonomic input, nature "did not reinvent molecular wheels within the coupled-clock system of pacemaker cells," but differentially engaged or scaled the kinetics of gears that regulate the rate and rhythm at which the "wheels spin" in a given autonomic input context.
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Affiliation(s)
- Dongmei Yang
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Christopher H. Morrell
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
- Department of Mathematics and Statistics, Loyola University Maryland, Baltimore, MD, United States
| | - Alexey E. Lyashkov
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Syevda Tagirova Sirenko
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Ihor Zahanich
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Yael Yaniv
- Biomedical Engineering Faculty, Technion–Israel Institute of Technology, Haifa, Israel
| | - Tatiana M. Vinogradova
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Bruce D. Ziman
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Victor A. Maltsev
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| | - Edward G. Lakatta
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
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Vinogradova TM, Sirenko S, Lukyanenko YO, Yang D, Tarasov KV, Lyashkov AE, Varghese NJ, Li Y, Chakir K, Ziman B, Lakatta EG. Basal Spontaneous Firing of Rabbit Sinoatrial Node Cells Is Regulated by Dual Activation of PDEs (Phosphodiesterases) 3 and 4. Circ Arrhythm Electrophysiol 2019; 11:e005896. [PMID: 29880528 DOI: 10.1161/circep.117.005896] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 03/27/2018] [Indexed: 12/21/2022]
Abstract
BACKGROUND Spontaneous firing of sinoatrial node cells (SANCs) is regulated by cAMP-mediated, PKA (protein kinase A)-dependent (cAMP/PKA) local subsarcolemmal Ca2+ releases (LCRs) from RyRs (ryanodine receptors). LCRs occur during diastolic depolarization and activate an inward Na+/Ca2+ exchange current that accelerates diastolic depolarization rate prompting the next action potential. PDEs (phosphodiesterases) regulate cAMP-mediated signaling; PDE3/PDE4 represent major PDE activities in SANC, but how they modulate LCRs and basal spontaneous SANC firing remains unknown. METHODS Real-time polymerase chain reaction, Western blot, immunostaining, cellular perforated patch clamping, and confocal microscopy were used to elucidate mechanisms of PDE-dependent regulation of cardiac pacemaking. RESULTS PDE3A, PDE4B, and PDE4D were the major PDE subtypes expressed in rabbit SANC, and PDE3A was colocalized with α-actinin, PDE4D, SERCA (sarcoplasmic reticulum Ca2+ ATP-ase), and PLB (phospholamban) in Z-lines. Inhibition of PDE3 (cilostamide) or PDE4 (rolipram) alone increased spontaneous SANC firing by ≈20% (P<0.05) and ≈5% (P>0.05), respectively, but concurrent PDE3+PDE4 inhibition increased spontaneous firing by ≈45% (P<0.01), indicating synergistic effect. Inhibition of PDE3 or PDE4 alone increased L-type Ca2+ current (ICa,L) by ≈60% (P<0.01) or ≈5% (P>0.05), respectively, and PLB phosphorylation by ≈20% (P>0.05) each, but dual PDE3+PDE4 inhibition increased ICa,L by ≈100% (P<0.01) and PLB phosphorylation by ≈110% (P<0.05). Dual PDE3+PDE4 inhibition increased the LCR number and size (P<0.01) and reduced the SR (sarcoplasmic reticulum) Ca2+ refilling time (P<0.01) and the LCR period (time from action potential-induced Ca2+ transient to subsequent LCR; P<0.01), leading to decrease in spontaneous SANC cycle length (P<0.01). When RyRs were disabled by ryanodine and LCRs ceased, dual PDE3+PDE4 inhibition failed to increase spontaneous SANC firing. CONCLUSIONS Basal cardiac pacemaker function is regulated by concurrent PDE3+PDE4 activation which operates in a synergistic manner via decrease in cAMP/PKA phosphorylation, suppression of LCR parameters, and prolongation of the LCR period and spontaneous SANC cycle length.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD.
| | - Syevda Sirenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Yevgeniya O Lukyanenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Kirill V Tarasov
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Alexey E Lyashkov
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Nevin J Varghese
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Yue Li
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Khalid Chakir
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Bruce Ziman
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD
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Chakir K, Lyashkov AE, Tarasov KV, Ahmet I, Yang D, Tarasova YS, Riordon D, Lukyanenko YO, Huynh T, Pacak K, Lakatta EG. Cardiac Overexpression of Human Adenylyl Cyclase Type 8 in Mice Elicits Phosphorylation- Dependent Mechanisms that Permit Perpetual Heart Exercise while Conferring Protection Against Excessive Camp-PKA Signaling. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.658] [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
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Yang D, Lyashkov AE, Morrell CH, Zahanich I, Yaniv Y, Vinogradova TM, Ziman BD, Lakatta EG. Rhythm and Rate of Action Potential Firing of Single Cardiac Pacemaker Cells Emerge from Concordant Beat to Beat Variability of Coupled Calcium and Membrane Potential Functions. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1264] [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: 10/27/2022] Open
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Lyashkov AE, Behar J, Lakatta EG, Yaniv Y, Maltsev VA. Positive Feedback Mechanisms among Local Ca Releases, NCX, and I CaL Ignite Pacemaker Action Potentials. Biophys J 2018; 114:2024. [PMID: 29694879 DOI: 10.1016/j.bpj.2018.03.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Maltsev VA, Lyashkov AE, Behar J, Lakatta EG, Yaniv Y. Positive Feedback Mechanisms among Local Ca Releases, NCX, & ICAL Ignite Pacemaker Action Potentials. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3367] [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: 10/18/2022] Open
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Lukyanenko YO, Younes A, Lyashkov AE, Tarasov KV, Riordon DR, Lee J, Sirenko SG, Kobrinsky E, Ziman B, Tarasova YS, Juhaszova M, Sollott SJ, Graham DR, Lakatta EG. Ca(2+)/calmodulin-activated phosphodiesterase 1A is highly expressed in rabbit cardiac sinoatrial nodal cells and regulates pacemaker function. J Mol Cell Cardiol 2016; 98:73-82. [PMID: 27363295 DOI: 10.1016/j.yjmcc.2016.06.064] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 05/23/2016] [Accepted: 06/23/2016] [Indexed: 11/29/2022]
Abstract
Constitutive Ca(2+)/calmodulin (CaM)-activation of adenylyl cyclases (ACs) types 1 and 8 in sinoatrial nodal cells (SANC) generates cAMP within lipid-raft-rich microdomains to initiate cAMP-protein kinase A (PKA) signaling, that regulates basal state rhythmic action potential firing of these cells. Mounting evidence in other cell types points to a balance between Ca(2+)-activated counteracting enzymes, ACs and phosphodiesterases (PDEs) within these cells. We hypothesized that the expression and activity of Ca(2+)/CaM-activated PDE Type 1A is higher in SANC than in other cardiac cell types. We found that PDE1A protein expression was 5-fold higher in sinoatrial nodal tissue than in left ventricle, and its mRNA expression was 12-fold greater in the corresponding isolated cells. PDE1 activity (nimodipine-sensitive) accounted for 39% of the total PDE activity in SANC lysates, compared to only 4% in left ventricular cardiomyocytes (LVC). Additionally, total PDE activity in SANC lysates was lowest (10%) in lipid-raft-rich and highest (76%) in lipid-raft-poor fractions (equilibrium sedimentation on a sucrose density gradient). In intact cells PDE1A immunolabeling was not localized to the cell surface membrane (structured illumination microscopy imaging), but located approximately within about 150nm inside of immunolabeling of hyperpolarization-activated cyclic nucleotide-gated potassium channels (HCN4), which reside within lipid-raft-rich microenvironments. In permeabilized SANC, in which surface membrane ion channels are not functional, nimodipine increased spontaneous SR Ca(2+) cycling. PDE1A mRNA silencing in HL-1 cells increased the spontaneous beating rate, reduced the cAMP, and increased cGMP levels in response to IBMX, a broad spectrum PDE inhibitor (detected via fluorescence resonance energy transfer microscopy). We conclude that signaling via cAMP generated by Ca(2+)/CaM-activated AC in SANC lipid raft domains is limited by cAMP degradation by Ca(2+)/CaM-activated PDE1A in non-lipid raft domains. This suggests that local gradients of [Ca(2+)]-CaM or different AC and PDE1A affinity regulate both cAMP production and its degradation, and this balance determines the intensity of Ca(2+)-AC-cAMP-PKA signaling that drives SANC pacemaker function.
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Affiliation(s)
- Yevgeniya O Lukyanenko
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Antoine Younes
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Alexey E Lyashkov
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA; Department of Molecular and Comparative Pathobiology, Johns Hopkins School of Medicine, 733 N. Broadway, MRB 835, Baltimore, MD 21205, USA.
| | - Kirill V Tarasov
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Daniel R Riordon
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Joonho Lee
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Syevda G Sirenko
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Evgeny Kobrinsky
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Bruce Ziman
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Yelena S Tarasova
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Magdalena Juhaszova
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - Steven J Sollott
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
| | - David R Graham
- Department of Molecular and Comparative Pathobiology, Johns Hopkins School of Medicine, 733 N. Broadway, MRB 835, Baltimore, MD 21205, USA.
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, National Institute on Aging, 251 Bayview Blvd., Baltimore, MD 21224, USA.
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Vinogradova TM, Lukyanenko Y, Tarasov KV, Sirenko S, Lyashkov AE, Li Y, Lakatta EG. Concurrent PDE3 and PDE4 Activation Suppresses Local Ca2+ Releases (LCR) to Regulate Normal Spontaneous Firing of Sinoatrial Node Cells (SANC). Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1485] [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: 11/16/2022] Open
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Yaniv Y, Ganesan A, Yang D, Ziman BD, Lyashkov AE, Levchenko A, Zhang J, Lakatta EG. Real-time relationship between PKA biochemical signal network dynamics and increased action potential firing rate in heart pacemaker cells: Kinetics of PKA activation in heart pacemaker cells. J Mol Cell Cardiol 2015; 86:168-78. [PMID: 26241846 DOI: 10.1016/j.yjmcc.2015.07.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [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: 02/13/2015] [Revised: 06/11/2015] [Accepted: 07/25/2015] [Indexed: 01/07/2023]
Abstract
cAMP-PKA protein kinase is a key nodal signaling pathway that regulates a wide range of heart pacemaker cell functions. These functions are predicted to be involved in regulation of spontaneous action potential (AP) generation of these cells. Here we investigate if the kinetics and stoichiometry of increase in PKA activity match the increase in AP firing rate in response to β-adrenergic receptor (β-AR) stimulation or phosphodiesterase (PDE) inhibition, that alters the AP firing rate of heart sinoatrial pacemaker cells. In cultured adult rabbit pacemaker cells infected with an adenovirus expressing the FRET sensor AKAR3, the EC50 in response to graded increases in the intensity of β-AR stimulation (by Isoproterenol) the magnitude of the increases in PKA activity and the spontaneous AP firing rate were similar (0.4±0.1nM vs. 0.6±0.15nM, respectively). Moreover, the kinetics (t1/2) of the increases in PKA activity and spontaneous AP firing rate in response to β-AR stimulation or PDE inhibition were tightly linked. We characterized the system rate-limiting biochemical reactions by integrating these experimentally derived data into a mechanistic-computational model. Model simulations predicted that phospholamban phosphorylation is a potent target of the increase in PKA activity that links to increase in spontaneous AP firing rate. In summary, the kinetics and stoichiometry of increases in PKA activity in response to a physiological (β-AR stimulation) or pharmacological (PDE inhibitor) stimuli match those of changes in the AP firing rate. Thus Ca(2+)-cAMP/PKA-dependent phosphorylation limits the rate and magnitude of increase in spontaneous AP firing rate.
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Affiliation(s)
- Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel.
| | - Ambhighainath Ganesan
- Department of Biomedical Engineering, The Johns Hopkins University of Medicine, Baltimore, MD, USA
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Biomedical Research Center Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Bruce D Ziman
- Laboratory of Cardiovascular Science, Biomedical Research Center Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Alexey E Lyashkov
- Laboratory of Cardiovascular Science, Biomedical Research Center Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Andre Levchenko
- System Biology Institute, Yale University, New Haven, CT, USA
| | - Jin Zhang
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA.
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Colquhoun DR, Lyashkov AE, Ubaida Mohien C, Aquino VN, Bullock BT, Dinglasan RR, Agnew BJ, Graham DRM. Bioorthogonal mimetics of palmitoyl-CoA and myristoyl-CoA and their subsequent isolation by click chemistry and characterization by mass spectrometry reveal novel acylated host-proteins modified by HIV-1 infection. Proteomics 2015; 15:2066-77. [PMID: 25914232 DOI: 10.1002/pmic.201500063] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 03/15/2015] [Accepted: 04/23/2015] [Indexed: 01/28/2023]
Abstract
Protein acylation plays a critical role in protein localization and function. Acylation is essential for human immunodeficiency virus 1 (HIV-1) assembly and budding of HIV-1 from the plasma membrane in lipid raft microdomains and is mediated by myristoylation of the Gag polyprotein and the copackaging of the envelope protein is facilitated by colocalization mediated by palmitoylation. Since the viral accessory protein NEF has been shown to alter the substrate specificity of myristoyl transferases, and alter cargo trafficking lipid rafts, we hypothesized that HIV-1 infection may alter protein acylation globally. To test this hypothesis, we labeled HIV-1 infected cells with biomimetics of acyl azides, which are incorporated in a manner analogous to natural acyl-Co-A. A terminal azide group allowed us to use a copper catalyzed click chemistry to conjugate the incorporated modifications to a number of substrates to carry out SDS-PAGE, fluorescence microscopy, and enrichment for LC-MS/MS. Using LC-MS/MS, we identified 103 and 174 proteins from the myristic and palmitic azide enrichments, with 27 and 45 proteins respectively that differentiated HIV-1 infected from uninfected cells. This approach has provided us with important insights into HIV-1 biology and is widely applicable to many virological systems.
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Affiliation(s)
- David R Colquhoun
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Alexey E Lyashkov
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ceereena Ubaida Mohien
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Veronica N Aquino
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Brandon T Bullock
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rhoel R Dinglasan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Brian J Agnew
- Biosciences Group, Thermo Fisher Scientific, Eugene, OR, USA
| | - David R M Graham
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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13
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Yang D, Lyashkov AE, Yaniv Y, Ziman BD, Lakatta EG. Phosphorylation-Dependent Synchronization of Random Spontaneous Local Diastolic Ca2+ Releases Regulates Action Potential Firing Rhythmicity of Pacemaker Cells. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.608] [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: 10/24/2022] Open
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14
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Yaniv Y, Lyashkov AE, Sirenko S, Okamoto Y, Guiriba TR, Ziman BD, Morrell CH, Lakatta EG. Stochasticity intrinsic to coupled-clock mechanisms underlies beat-to-beat variability of spontaneous action potential firing in sinoatrial node pacemaker cells. J Mol Cell Cardiol 2014; 77:1-10. [PMID: 25257916 DOI: 10.1016/j.yjmcc.2014.09.008] [Citation(s) in RCA: 28] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 08/25/2014] [Accepted: 09/10/2014] [Indexed: 12/31/2022]
Abstract
Recent evidence indicates that the spontaneous action potential (AP) of isolated sinoatrial node cells (SANCs) is regulated by a system of stochastic mechanisms embodied within two clocks: ryanodine receptors of the "Ca(2+) clock" within the sarcoplasmic reticulum, spontaneously activate during diastole and discharge local Ca(2+) releases (LCRs) beneath the cell surface membrane; clock crosstalk occurs as LCRs activate an inward Na(+)/Ca(2+) exchanger current (INCX), which together with If and decay of K(+) channels prompts the "M clock," the ensemble of sarcolemmal-electrogenic molecules, to generate APs. Prolongation of the average LCR period accompanies prolongation of the average AP beating interval (BI). Moreover, the prolongation of the average AP BI accompanies increased AP BI variability. We hypothesized that both the average AP BI and AP BI variability are dependent upon stochasticity of clock mechanisms reported by the variability of LCR period. We perturbed the coupled-clock system by directly inhibiting the M clock by ivabradine (IVA) or the Ca(2+) clock by cyclopiazonic acid (CPA). When either clock is perturbed by IVA (3, 10 and 30 μM), which has no direct effect on Ca(2+) cycling, or CPA (0.5 and 5 μM), which has no direct effect on the M clock ion channels, the clock system failed to achieve the basal AP BI and both AP BI and AP BI variability increased. The changes in average LCR period and its variability in response to perturbations of the coupled-clock system were correlated with changes in AP beating interval and AP beating interval variability. We conclude that the stochasticity within the coupled-clock system affects and is affected by the AP BI firing rate and rhythm via modulation of the effectiveness of clock coupling.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA; Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel.
| | - Alexey E Lyashkov
- Translational Gerontology Branch, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Syevda Sirenko
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Yosuke Okamoto
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Toni-Rose Guiriba
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Bruce D Ziman
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Christopher H Morrell
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA; Mathematics and Statistics Department, Loyola University, Baltimore, MD, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, MD, USA.
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15
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Monfredi O, Lyashkov AE, Johnsen AB, Inada S, Schneider H, Wang R, Nirmalan M, Wisloff U, Maltsev VA, Lakatta EG, Zhang H, Boyett MR. Biophysical characterization of the underappreciated and important relationship between heart rate variability and heart rate. Hypertension 2014; 64:1334-43. [PMID: 25225208 DOI: 10.1161/hypertensionaha.114.03782] [Citation(s) in RCA: 207] [Impact Index Per Article: 20.7] [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
Heart rate (HR) variability (HRV; beat-to-beat changes in the R-wave to R-wave interval) has attracted considerable attention during the past 30+ years (PubMed currently lists >17 000 publications). Clinically, a decrease in HRV is correlated to higher morbidity and mortality in diverse conditions, from heart disease to fetal distress. It is usually attributed to fluctuation in cardiac autonomic nerve activity. We calculated HRV parameters from a variety of cardiac preparations (including humans, living animals, Langendorff-perfused heart, and single sinoatrial nodal cell) in diverse species, combining this with data from previously published articles. We show that regardless of conditions, there is a universal exponential decay-like relationship between HRV and HR. Using 2 biophysical models, we develop a theory for this and confirm that HRV is primarily dependent on HR and cannot be used in any simple way to assess autonomic nerve activity to the heart. We suggest that the correlation between a change in HRV and altered morbidity and mortality is substantially attributable to the concurrent change in HR. This calls for re-evaluation of the findings from many articles that have not adjusted properly or at all for HR differences when comparing HRV in multiple circumstances.
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Affiliation(s)
- Oliver Monfredi
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.).
| | - Alexey E Lyashkov
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Anne-Berit Johnsen
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Shin Inada
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Heiko Schneider
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Ruoxi Wang
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Mahesh Nirmalan
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Ulrik Wisloff
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Victor A Maltsev
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Edward G Lakatta
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Henggui Zhang
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
| | - Mark R Boyett
- From the Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (O.M., H.S., M.N., M.R.B.); Laboratory of Cardiovascular Science, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD (O.M., A.E.L., V.A.M., E.G.L.); K.G. Jebsen Center of Exercise in Medicine at Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway (A.-B.J., U.W.); Laboratory of Biomedical Sciences and Information Management, National Cerebral and Cardiovascular Center, Osaka, Japan (S.I.); and Biological Physics Group, University of Manchester, Manchester, United Kingdom (R.W., H.Z.)
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Yaniv Y, Ahmet I, Liu J, Lyashkov AE, Guiriba TR, Okamoto Y, Ziman BD, Lakatta EG. Synchronization of sinoatrial node pacemaker cell clocks and its autonomic modulation impart complexity to heart beating intervals. Heart Rhythm 2014; 11:1210-9. [PMID: 24713624 DOI: 10.1016/j.hrthm.2014.03.049] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [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: 12/05/2013] [Indexed: 10/25/2022]
Abstract
BACKGROUND A reduction of complexity of heart beating interval variability that is associated with an increased morbidity and mortality in cardiovascular disease states is thought to derive from the balance of sympathetic and parasympathetic neural impulses to the heart. However, rhythmic clocklike behavior intrinsic to pacemaker cells in the sinoatrial node (SAN) drives their beating, even in the absence of autonomic neural input. OBJECTIVE To test how this rhythmic clocklike behavior intrinsic to pacemaker cells interacts with autonomic impulses to the heart beating interval variability in vivo. METHODS We analyzed beating interval variability in time and frequency domains and by fractal and entropy analyses: (1) in vivo, when the brain input to the SAN is intact; (2) during autonomic denervation in vivo; (3) in isolated SAN tissue (ie, in which the autonomic neural input is completely absent); (4) in single pacemaker cells isolated from the SAN; and (5) after autonomic receptor stimulation of these cells. RESULTS Spontaneous beating intervals of pacemaker cells residing in the isolated SAN tissue exhibit fractal-like behavior and have lower approximate entropy compared with those in the intact heart. Isolation of pacemaker cells from SAN tissue, however, leads to a loss in the beating interval order and fractal-like behavior. β-Adrenergic receptor stimulation of isolated pacemaker cells increases intrinsic clock synchronization, decreases their action potential period, and increases system complexity. CONCLUSIONS Both the average beating interval in vivo and beating interval complexity are conferred by the combined effects of clock periodicity intrinsic to pacemaker cells and their response to autonomic neural input.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland; Biomedical Engineering Faculty, Technion-IIT, Haifa, Israel.
| | - Ismayil Ahmet
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Jie Liu
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland; Cardiovascular Physiology Laboratory, School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Alexey E Lyashkov
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Toni-Rose Guiriba
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Yosuke Okamoto
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Bruce D Ziman
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
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Yaniv Y, Lyashkov AE, Lakatta EG. Impaired signaling intrinsic to sinoatrial node pacemaker cells affects heart rate variability during cardiac disease. ACTA ACUST UNITED AC 2014; 4. [PMID: 26251764 DOI: 10.4172/2167-0870.1000152] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [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: 01/14/2023]
Abstract
The normal heart beat intervals are neither strictly stationary nor completely random, and continuously shift from one period to another. Decoding the ECG identifies this "hidden" information that imparts inherent complexity to the heart-beating interval time series. Loss of this complexity in cardiovascular disease is manifested as a reduction in heart rate variability (HRV) and this reduction correlates with an increase in both morbidity and mortality. Because HRV measurements are noninvasive and easy to perform, they have emerged as an important tool in cardiology. However, the identities of specific mechanisms that underline the changes in HRV that occur in cardiovascular diseases remain largely unknown. Changes in HRV have mainly been interpreted on a neural basis, ie due to changes in autonomic impulses to the heart: sympathetic activity decreases both the average heart beat interval and HRV, and parasympathetic activity increases both. It has now become clear, however, that the heart rate and HRV are also determined by intrinsic properties of the pacemaker cells that comprise the sinoatrial node, and the responses of these properties to autonomic receptor stimulation. Here we review how changes in the properties of coupled-clock mechanisms intrinsic to pacemaker cells that comprise the sinoatrial node and their impaired response to autonomic receptor stimulation are implicated in the changes of HRV observed in heart diseases.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
| | - Alexey E Lyashkov
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 North Broadway, Baltimore, Maryland, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
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18
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Yang D, Lyashkov AE, Ziman BD, Lakatta EG. CA2+ Cycling Proteins Phosphorylation in Isolated Sinoatrial Nodal Cells Modulates the Stochasticity of Spontaneous Diastolic Local CA2+ Releases which Regulate the Action Potential Cycle Length and its Beat-To-Beat Variation. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.680] [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
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Yaniv Y, Lyashkov AE, Lakatta EG. The fractal-like complexity of heart rate variability beyond neurotransmitters and autonomic receptors: signaling intrinsic to sinoatrial node pacemaker cells. ACTA ACUST UNITED AC 2013; 2. [PMID: 26709383 DOI: 10.4172/2329-6607.1000111] [Citation(s) in RCA: 23] [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] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The heart rate and rhythm are controlled by complex chaotic neural, chemical and hormonal networks which are not strictly regular, but exhibit fluctuations across multiple time scales. A careful assessment of the heart rate variability (HRV) offers clues to this complexity. A reduction in HRV, specifically in advanced age, is associated with increase in morbidity and mortality. Mechanisms that induce this decrease, however, have not been fully elucidated. The classical literature characterizes changes in HRV as a result of changes in the balance of competing influences of the sympathetic and parasympathetic autonomic impulses delivered to the heart. It has now become clear, however, that the heart rate and HRV are also determined by intrinsic properties of the pacemaker cells that comprise sinoatrial node, and that these properties respond to autonomic receptor stimulation in a non-linear mode. That HRV is determined by both the intrinsic properties of pacemaker cells in the sinoatrial node and the competing influences of the two branches of the autonomic neural input to the cells requires an expansion of our perspective about mechanisms that govern HRV in the normal heart, and how HRV changes with aging in health and in heart diseases.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
| | - Alexey E Lyashkov
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, 733 North Broadway, Baltimore, Maryland, USA
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland, USA
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Yaniv Y, Spurgeon HA, Ziman BD, Lyashkov AE, Lakatta EG. Mechanisms that match ATP supply to demand in cardiac pacemaker cells during high ATP demand. Am J Physiol Heart Circ Physiol 2013; 304:H1428-38. [PMID: 23604710 DOI: 10.1152/ajpheart.00969.2012] [Citation(s) in RCA: 31] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The spontaneous action potential (AP) firing rate of sinoatrial node cells (SANCs) involves high-throughput signaling via Ca(2+)-calmodulin activated adenylyl cyclases (AC), cAMP-mediated protein kinase A (PKA), and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of SR Ca(2+) cycling and surface membrane ion channel proteins. When the throughput of this signaling increases, e.g., in response to β-adrenergic receptor activation, the resultant increase in spontaneous AP firing rate increases the demand for ATP. We hypothesized that an increase of ATP production to match the increased ATP demand is achieved via a direct effect of increased mitochondrial Ca(2+) (Ca(2+)m) and an indirect effect via enhanced Ca(2+)-cAMP/PKA-CaMKII signaling to mitochondria. To increase ATP demand, single isolated rabbit SANCs were superfused by physiological saline at 35 ± 0.5°C with isoproterenol, or by phosphodiesterase or protein phosphatase inhibition. We measured cytosolic and mitochondrial Ca(2+) and flavoprotein fluorescence in single SANC, and we measured cAMP, ATP, and O₂ consumption in SANC suspensions. Although the increase in spontaneous AP firing rate was accompanied by an increase in O₂ consumption, the ATP level and flavoprotein fluorescence remained constant, indicating that ATP production had increased. Both Ca(2+)m and cAMP increased concurrently with the increase in AP firing rate. When Ca(2+)m was reduced by Ru360, the increase in spontaneous AP firing rate in response to isoproterenol was reduced by 25%. Thus, both an increase in Ca(2+)m and an increase in Ca(2+) activated cAMP-PKA-CaMKII signaling regulate the increase in ATP supply to meet ATP demand above the basal level.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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21
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Sirenko S, Yang D, Li Y, Lyashkov AE, Lukyanenko YO, Lakatta EG, Vinogradova TM. Ca²⁺-dependent phosphorylation of Ca²⁺ cycling proteins generates robust rhythmic local Ca²⁺ releases in cardiac pacemaker cells. Sci Signal 2013; 6:ra6. [PMID: 23362239 DOI: 10.1126/scisignal.2003391] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The spontaneous beating of the heart is governed by spontaneous firing of sinoatrial node cells, which generate action potentials due to spontaneous depolarization of the membrane potential, or diastolic depolarization. The spontaneous diastolic depolarization rate is determined by spontaneous local submembrane Ca²⁺ releases through ryanodine receptors (RyRs). We sought to identify specific mechanisms of intrinsic Ca²⁺ cycling by which sinoatrial node cells, but not ventricular myocytes, generate robust, rhythmic local Ca²⁺ releases. At similar physiological intracellular Ca²⁺ concentrations, local Ca²⁺ releases were large and rhythmic in permeabilized sinoatrial node cells but small and random in permeabilized ventricular myocytes. Furthermore, sinoatrial node cells spontaneously released more Ca²⁺ from the sarcoplasmic reticulum than did ventricular myocytes, despite comparable sarcoplasmic reticulum Ca²⁺ content in both cell types. This ability of sinoatrial node cells to generate larger and rhythmic local Ca²⁺ releases was associated with increased abundance of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA), reduced abundance of the SERCA inhibitor phospholamban, and increased Ca²⁺-dependent phosphorylation of phospholamban and RyR. The increased phosphorylation of RyR in sinoatrial node cells may facilitate Ca²⁺ release from the sarcoplasmic reticulum, whereas Ca²⁺-dependent increase in phosphorylation of phospholamban relieves its inhibition of SERCA, augmenting the pumping rate of Ca²⁺ required to support robust, rhythmic local Ca²⁺ releases. The differences in Ca²⁺ cycling between sinoatrial node cells and ventricular myocytes provide insights into the regulation of intracellular Ca²⁺ cycling that drives the automaticity of sinoatrial node cells.
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Affiliation(s)
- Syevda Sirenko
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging Intramural Research Program, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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22
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Yang D, Lyashkov AE, Ziman BD, Lakatta EG. Basal cAMP/Pka/Ca2+ Signaling is Linked to Action Potential (AP) Rhythmicity of Sinoatrial Nodal Cells (SANC) as well as to their Firing Rate. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1583] [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: 10/27/2022] Open
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23
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Yang D, Lyashkov AE, Li Y, Ziman BD, Lakatta EG. RGS2 overexpression or G(i) inhibition rescues the impaired PKA signaling and slow AP firing of cultured adult rabbit pacemaker cells. J Mol Cell Cardiol 2012; 53:687-94. [PMID: 22921807 DOI: 10.1016/j.yjmcc.2012.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 07/23/2012] [Accepted: 08/10/2012] [Indexed: 12/16/2022]
Abstract
Freshly isolated adult rabbit sinoatrial node cells (f-SANC) are an excellent model for studies of autonomic signaling, but are not amenable to genetic manipulation. We have developed and characterized a stable cultured rabbit SANC (c-SANC) model that is suitable for genetic manipulation to probe mechanisms of spontaneous action potential (AP) firing. After 48 h in culture, c-SANC generate stable, rhythmic APs at 34±0.5°C, at a rate that is 50% less than f-SANC. In c- vs. f-SANC: AP duration is prolonged; phosphorylation of phospholamban at Ser(16) and type2 ryanodine receptor (RyR2) at Ser(2809) are reduced; and the level of type2 regulator of G-protein signaling (RGS2), that facilitates adenylyl cyclases/cAMP/protein kinase A (PKA) via G(i) inhibition, is substantially reduced. Consistent with the interpretation that cAMP/PKA signaling becomes impaired in c-SANC, acute β-adrenergic receptor stimulation increases phospholamban and RyR2 phosphorylation, enhances RGS2-labeling density, and accelerates the AP firing rate to the similar maximum in c- and f-SANC. Specific PKA inhibition completely inhibits all β-adrenergic receptor effects. Adv-RGS2 infection, or pertussis toxin treatment to disable G(i)-signaling, each partially rescues the c-SANC spontaneous AP firing rate. Thus, a G(i)-dependent reduction in PKA-dependent protein phosphorylation, including that of Ca(2+) cycling proteins, reduces the spontaneous AP firing rate of c-SANC, and can be reversed by genetic or pharmacologic manipulation of PKA signaling.
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Affiliation(s)
- Dongmei Yang
- Laboratory of Cardiovascular Science, IRP, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224-6825, USA
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Yaniv Y, Spurgeon HA, Lyashkov AE, Yang D, Ziman BD, Maltsev VA, Lakatta EG. Crosstalk between mitochondrial and sarcoplasmic reticulum Ca2+ cycling modulates cardiac pacemaker cell automaticity. PLoS One 2012; 7:e37582. [PMID: 22666369 PMCID: PMC3362629 DOI: 10.1371/journal.pone.0037582] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/22/2012] [Indexed: 01/02/2023] Open
Abstract
Background Mitochondria dynamically buffer cytosolic Ca2+ in cardiac ventricular cells and this affects the Ca2+ load of the sarcoplasmic reticulum (SR). In sinoatrial-node cells (SANC) the SR generates periodic local, subsarcolemmal Ca2+ releases (LCRs) that depend upon the SR load and are involved in SANC automaticity: LCRs activate an inward Na+-Ca2+ exchange current to accelerate the diastolic depolarization, prompting the ensemble of surface membrane ion channels to generate the next action potential (AP). Objective To determine if mitochondrial Ca2+ (Ca2+m), cytosolic Ca2+ (Ca2+c)-SR-Ca2+ crosstalk occurs in single rabbit SANC, and how this may relate to SANC normal automaticity. Results Inhibition of mitochondrial Ca2+ influx into (Ru360) or Ca2+ efflux from (CGP-37157) decreased [Ca2+]m to 80±8% control or increased [Ca2+]m to 119±7% control, respectively. Concurrent with inhibition of mitochondrial Ca2+ influx or efflux, the SR Ca2+ load, and LCR size, duration, amplitude and period (imaged via confocal linescan) significantly increased or decreased, respectively. Changes in total ensemble LCR Ca2+ signal were highly correlated with the change in the SR Ca2+ load (r2 = 0.97). Changes in the spontaneous AP cycle length (Ru360, 111±1% control; CGP-37157, 89±2% control) in response to changes in [Ca2+]m were predicted by concurrent changes in LCR period (r2 = 0.84). Conclusion A change in SANC Ca2+m flux translates into a change in the AP firing rate by effecting changes in Ca2+c and SR Ca2+ loading, which affects the characteristics of spontaneous SR Ca2+ release.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Harold A. Spurgeon
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Alexey E. Lyashkov
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Bruce D. Ziman
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Victor A. Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Edward G. Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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Parish LA, Colquhoun DR, Ubaida Mohien C, Lyashkov AE, Graham DR, Dinglasan RR. Ookinete-interacting proteins on the microvillar surface are partitioned into detergent resistant membranes of Anopheles gambiae midguts. J Proteome Res 2011; 10:5150-62. [PMID: 21905706 PMCID: PMC3208356 DOI: 10.1021/pr2006268] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [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: 11/28/2022]
Abstract
Lipid raft microdomains, a component of detergent resistant membranes (DRMs), are routinely exploited by pathogens during host-cell entry. Multiple membrane-surface proteins mediate Plasmodium ookinete invasion of the Anopheles midgut, a critical step in the parasite life cycle that is successfully targeted by transmission-blocking vaccines (TBV). Given that lipid rafts are a common feature of host-pathogen interactions, we hypothesized that they promote the partitioning of midgut surface proteins and thus facilitate ookinete invasion. In support of this hypothesis, we found that five of the characterized Anopheles TBV candidates, including the leading Anopheles TBV candidate, AgAPN1, are present in Anopheles gambiae DRMs. Therefore, to extend the repertoire of putative midgut ligands that can be targeted by TBVs, we analyzed midgut DRMs by tandem mass spectrometry. We identified 1452 proteins including several markers of DRMs. Since glycosylphosphotidyl inositol (GPI)-anchored proteins partition to DRMs, we characterized the GPI subproteome of An. gambiae midgut brush-border microvilli and found that 96.9% of the proteins identified in the GPI-anchored fractions were also present in DRMs. Our study vastly expands the number of candidate malarial TBV targets for subsequent analysis by the broader community and provides an inferred role for midgut plasmalemma microdomains in ookinete cell invasion.
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Affiliation(s)
- Lindsay A Parish
- W. Harry Feinstone Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
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Yaniv Y, Juhaszova M, Lyashkov AE, Spurgeon HA, Sollott SJ, Lakatta EG. Ca2+-regulated-cAMP/PKA signaling in cardiac pacemaker cells links ATP supply to demand. J Mol Cell Cardiol 2011; 51:740-8. [PMID: 21835182 DOI: 10.1016/j.yjmcc.2011.07.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 07/12/2011] [Accepted: 07/21/2011] [Indexed: 10/17/2022]
Abstract
RATIONALE In sinoatrial node cells (SANC), Ca(2+) activates adenylate cyclase (AC) to generate a high basal level of cAMP-mediated/protein kinase A (PKA)-dependent phosphorylation of Ca(2+) cycling proteins. These result in spontaneous sarcoplasmic-reticulum (SR) generated rhythmic Ca(2+) oscillations during diastolic depolarization, that not only trigger the surface membrane to generate rhythmic action potentials (APs), but, in a feed-forward manner, also activate AC/PKA signaling. ATP is consumed to pump Ca(2+) to the SR, to produce cAMP, to support contraction and to maintain cell ionic homeostasis. OBJECTIVE Since feedback mechanisms link ATP-demand to ATP production, we hypothesized that (1) both basal ATP supply and demand in SANC would be Ca(2+)-cAMP/PKA dependent; and (2) due to its feed-forward nature, a decrease in flux through the Ca(2+)-cAMP/PKA signaling axis will reduce the basal ATP production rate. METHODS AND RESULTS O(2) consumption in spontaneous beating SANC was comparable to ventricular myocytes (VM) stimulated at 3 Hz. Graded reduction of basal Ca(2+)-cAMP/PKA signaling to reduce ATP demand in rabbit SANC produced graded ATP depletion (r(2)=0.96), and reduced O(2) consumption and flavoprotein fluorescence. Neither inhibition of glycolysis, selectively blocking contraction nor specific inhibition of mitochondrial Ca(2+) flux reduced the ATP level. CONCLUSIONS Feed-forward basal Ca(2+)-cAMP/PKA signaling both consumes ATP to drive spontaneous APs in SANC and is tightly linked to mitochondrial ATP production. Interfering with Ca(2+)-cAMP/PKA signaling not only slows the firing rate and reduces ATP consumption, but also appears to reduce ATP production so that ATP levels fall. This distinctly differs from VM, which lack this feed-forward basal cAMP/PKA signaling, and in which ATP level remains constant when the demand changes.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Gerontology Research Center, Intramural Research Program, National Institute on Aging, NIH, Baltimore, Maryland 21224-6825, USA
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Yaniv Y, Juhaszova M, Lyashkov AE, Spurgeon HA, Sollott SJ, Lakatta EG. Ca2+-Regulated-cAMP/PKA Signaling in Cardiac Pacemaker Cells Links ATP Supply to Demand. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.2579] [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: 10/18/2022] Open
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28
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Yang D, Zahanich I, Lyashkov AE, Lakatta EG. Sinoatrial Nodal (SAN) Cells from Center or Peripheral SAN Area are not Functionally Different. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.3329] [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
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29
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Lyashkov AE, Vinogradova TM, Zahanich I, Li Y, Younes A, Nuss HB, Spurgeon HA, Maltsev VA, Lakatta EG. Cholinergic receptor signaling modulates spontaneous firing of sinoatrial nodal cells via integrated effects on PKA-dependent Ca(2+) cycling and I(KACh). Am J Physiol Heart Circ Physiol 2009; 297:H949-59. [PMID: 19542482 DOI: 10.1152/ajpheart.01340.2008] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Prior studies indicate that cholinergic receptor (ChR) activation is linked to beating rate reduction (BRR) in sinoatrial nodal cells (SANC) via 1) a G(i)-coupled reduction in adenylyl cyclase (AC) activity, leading to a reduction of cAMP or protein kinase A (PKA) modulation of hyperpolarization-activated current (I(f)) or L-type Ca(2+) currents (I(Ca,L)), respectively; and 2) direct G(i)-coupled activation of ACh-activated potassium current (I(KACh)). More recent studies, however, have indicated that Ca(2+) cycling by the sarcoplasmic reticulum within SANC (referred to as a Ca(2+) clock) generates rhythmic, spontaneous local Ca(2+) releases (LCR) that are AC-PKA dependent. LCRs activate Na(+)-Ca(2+) exchange (NCX) current, which ignites the surface membrane ion channels to effect an AP. The purpose of the present study was to determine how ChR signaling initiated by a cholinergic agonist, carbachol (CCh), affects AC, cAMP, and PKA or sarcolemmal ion channels and LCRs and how these effects become integrated to generate the net response to a given intensity of ChR stimulation in single, isolated rabbit SANC. The threshold CCh concentration ([CCh]) for BRR was approximately 10 nM, half maximal inhibition (IC(50)) was achieved at 100 nM, and 1,000 nM stopped spontaneous beating. G(i) inhibition by pertussis toxin blocked all CCh effects on BRR. Using specific ion channel blockers, we established that I(f) blockade did not affect BRR at any [CCh] and that I(KACh) activation, evidenced by hyperpolarization, first became apparent at [CCh] > 30 nM. At IC(50), CCh reduced cAMP and reduced PKA-dependent phospholamban (PLB) phosphorylation by approximately 50%. The dose response of BRR to CCh in the presence of I(KACh) blockade by a specific inhibitor, tertiapin Q, mirrored that of CCh to reduced PLB phosphorylation. At IC(50), CCh caused a time-dependent reduction in the number and size of LCRs and a time dependent increase in LCR period that paralleled coincident BRR. The phosphatase inhibitor calyculin A reversed the effect of IC(50) CCh on SANC LCRs and BRR. Numerical model simulations demonstrated that Ca(2+) cycling is integrated into the cholinergic modulation of BRR via LCR-induced activation of NCX current, providing theoretical support for the experimental findings. Thus ChR stimulation-induced BRR is entirely dependent on G(i) activation and the extent of G(i) coupling to Ca(2+) cycling via PKA signaling or to I(KACh): at low [CCh], I(KACh) activation is not evident and BRR is attributable to a suppression of cAMP-mediated, PKA-dependent Ca(2+) signaling; as [CCh] increases beyond 30 nM, a tight coupling between suppression of PKA-dependent Ca(2+) signaling and I(KACh) activation underlies a more pronounced BRR.
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Affiliation(s)
- Alexey E Lyashkov
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224-6825, USA
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Vinogradova TM, Lyashkov AE, Spurgeon H, Lakatta EG. Concerted Phosphodiesterase (PDE) Subtype Activity Modulates Ca2+ Influx Through L-type Ca2+ Channels To Regulate Spontaneous Firing of Rabbit Sinoatrial Node Cells (SANC). Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.1015] [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: 10/21/2022] Open
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31
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Younes A, Lyashkov AE, Graham D, Sheydina A, Volkova MV, Mitsak M, Vinogradova TM, Lukyanenko YO, Li Y, Ruknudin AM, Boheler KR, van Eyk J, Lakatta EG. Ca(2+) -stimulated basal adenylyl cyclase activity localization in membrane lipid microdomains of cardiac sinoatrial nodal pacemaker cells. J Biol Chem 2008; 283:14461-8. [PMID: 18356168 DOI: 10.1074/jbc.m707540200] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Spontaneous, rhythmic subsarcolemmal local Ca(2+) releases driven by cAMP-mediated, protein kinase A (PKA)-dependent phosphorylation are crucial for normal pacemaker function of sinoatrial nodal cells (SANC). Because local Ca(2+) releases occur beneath the cell surface membrane, near to where adenylyl cyclases (ACs) reside, we hypothesized that the dual Ca(2+) and cAMP/PKA regulatory components of automaticity are coupled via Ca(2+) activation of AC activity within membrane microdomains. Here we show by quantitative reverse transcriptase PCR that SANC express Ca(2+)-activated AC isoforms 1 and 8, in addition to AC type 2, 5, and 6 transcripts. Immunolabeling of cell fractions, isolated by sucrose gradient ultracentrifugation, confirmed that ACs localize to membrane lipid microdomains. AC activity within these lipid microdomains is activated by Ca(2+) over the entire physiological Ca(2+) range. In intact SANC, the high basal AC activity produces a high level of cAMP that is further elevated by phosphodiesterase inhibition. cAMP and cAMP-mediated PKA-dependent activation of ion channels and Ca(2+) cycling proteins drive sarcoplasmic reticulum Ca(2+) releases, which, in turn, activate ACs. This feed forward "fail safe" system, kept in check by a high basal phosphodiesterase activity, is central to the generation of normal rhythmic, spontaneous action potentials by pacemaker cells.
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Affiliation(s)
- Antoine Younes
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, Intramural Research Program, NIH, Baltimore, MD 21224, USA
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Vinogradova TM, Sirenko S, Lyashkov AE, Younes A, Li Y, Zhu W, Yang D, Ruknudin AM, Spurgeon H, Lakatta EG. Constitutive phosphodiesterase activity restricts spontaneous beating rate of cardiac pacemaker cells by suppressing local Ca2+ releases. Circ Res 2008; 102:761-9. [PMID: 18276917 DOI: 10.1161/circresaha.107.161679] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Spontaneous beating of rabbit sinoatrial node cells (SANCs) is controlled by cAMP-mediated, protein kinase A-dependent local subsarcolemmal ryanodine receptor Ca(2+) releases (LCRs). LCRs activated an inward Na(+)/Ca(2+) exchange current that increases the terminal diastolic depolarization rate and, therefore, the spontaneous SANC beating rate. Basal cAMP in SANCs is elevated, suggesting that cAMP degradation by phosphodiesterases (PDEs) may be low. Surprisingly, total suppression of PDE activity with a broad-spectrum PDE inhibitor, 3'-isobutylmethylxanthine (IBMX), produced a 9-fold increase in the cAMP level, doubled cAMP-mediated, protein kinase A-dependent phospholamban phosphorylation, and increased SANC firing rate by approximately 55%, indicating a high basal activity of PDEs in SANCs. A comparison of specific PDE1 to -5 inhibitors revealed that the specific PDE3 inhibitor, milrinone, accelerated spontaneous firing by approximately 47% (effects of others were minor) and increased amplitude of L-type Ca(2+) current (I(Ca,L)) by approximately 46%, indicating that PDE3 was the major constitutively active PDE in the basal state. PDE-dependent control of the spontaneous SANC firing was critically dependent on subsarcolemmal LCRs, ie, PDE inhibition increased LCR amplitude and size and decreased LCR period, leading to earlier and augmented LCR Ca(2+) release, Na(+)/Ca(2+) exchange current, and an increase in the firing rate. When ryanodine receptors were disabled by ryanodine, neither IBMX nor milrinone was able to amplify LCRs, accelerate diastolic depolarization rate, or increase the SANC firing rate, despite preserved PDE inhibition-induced augmentation of I(Ca,L) amplitude. Thus, basal constitutive PDE activation provides a novel and powerful mechanism to decrease cAMP, limit cAMP-mediated, protein kinase A-dependent increase of diastolic ryanodine receptor Ca(2+) release, and restrict the spontaneous SANC beating rate.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, NIH, 5600 Nathan Shock Dr, Baltimore, MD 21224-6825, USA.
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Lyashkov AE, Juhaszova M, Dobrzynski H, Vinogradova TM, Maltsev VA, Juhasz O, Spurgeon HA, Sollott SJ, Lakatta EG. Calcium cycling protein density and functional importance to automaticity of isolated sinoatrial nodal cells are independent of cell size. Circ Res 2007; 100:1723-31. [PMID: 17525366 DOI: 10.1161/circresaha.107.153676] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Spontaneous, localized, rhythmic ryanodine receptor (RyRs) Ca(2+) releases occur beneath the cell membrane during late diastolic depolarization in cardiac sinoatrial nodal cells (SANCs). These activate the Na(+)/Ca(2+) exchanger (NCX1) to generate inward current and membrane excitation that drives normal spontaneous beating. The morphological background for the proposed functional of RyR and NCX crosstalk, however, has not been demonstrated. Here we show that the average isolated SANC whole cell labeling density of RyRs and SERCA2 is similar to atrial and ventricle myocytes, and is similar among SANCs of all sizes. Labeling of NCX1 is also similar among SANCs of all sizes and exceeds that in atrial and ventricle myocytes. Submembrane colocalization of NCX1 and cardiac RyR (cRyR) in all SANCs exceeds that in the other cell types. Further, the Cx43 negative primary pacemaker area of the intact rabbit sinoatrial node (SAN) exhibits robust positive labeling for cRyR, NCX1, and SERCA2. Functional studies in isolated SANCs show that neither the average action potential (AP) characteristics, nor those of intracellular Ca(2+) releases, nor the spontaneous cycle length vary with cell size. Chelation of intracellular [Ca(2+)], or disabling RyRs or NCX1, markedly attenuates or abolishes spontaneous SANC beating in all SANCs. Thus, there is dense labeling of SERCA2, RyRs, and NCX1 in small-sized SANCs, thought to reside within the SAN center, the site of impulse initiation. Because normal automaticity of these cells requires intact Ca(2+) cycling, interactions of SERCA, RyR2 and NCX molecules are implicated in the initiation of the SAN impulse.
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Affiliation(s)
- Alexey E Lyashkov
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, NIH, Baltimore, Maryland 21224-6825, USA
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Bogdanov KY, Maltsev VA, Vinogradova TM, Lyashkov AE, Spurgeon HA, Stern MD, Lakatta EG. Membrane Potential Fluctuations Resulting From Submembrane Ca
2+
Releases in Rabbit Sinoatrial Nodal Cells Impart an Exponential Phase to the Late Diastolic Depolarization That Controls Their Chronotropic State. Circ Res 2006; 99:979-87. [PMID: 17008599 DOI: 10.1161/01.res.0000247933.66532.0b] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Stochastic but roughly periodic LCRs (
L
ocal subsarcolemmal ryanodine receptor–mediated
C
a
2+
R
eleases) during the late phase of diastolic depolarization (DD) in rabbit sinoatrial nodal pacemaker cells (SANCs) generate an inward current (
I
NCX
) via the Na
+
/Ca
2+
exchanger. Although LCR characteristics have been correlated with spontaneous beating, the specific link between LCR characteristics and SANC spontaneous beating rate, ie, impact of LCRs on the fine structure of the DD, have not been explicitly defined. Here we determined how LCRs and resultant
I
NCX
impact on the DD fine structure to control the spontaneous SANC firing rate. Membrane potential (
V
m
) recordings combined with confocal Ca
2+
measurements showed that LCRs impart a nonlinear, exponentially rising phase to the DD later part, which exhibited beat-to-beat
V
m
fluctuations with an amplitude of approximately 2 mV. Maneuvers that altered LCR timing or amplitude of the nonlinear DD (ryanodine, BAPTA, nifedipine or isoproterenol) produced corresponding changes in
V
m
fluctuations during the nonlinear DD component, and the
V
m
fluctuation response evoked by these maneuvers was tightly correlated with the concurrent changes in spontaneous beating rate induced by these perturbations. Numerical modeling, using measured LCR characteristics under these perturbations, predicted a family of local
I
NCX
that reproduced
V
m
fluctuations measured experimentally and determined the onset and amplitude of the nonlinear DD component and the beating rate. Thus, beat-to-beat
V
m
fluctuations during late DD phase reflect the underlying LCR/
I
NCX
events, and the ensemble of these events forms the nonlinear DD component that ultimately controls the SANC chronotropic state in tight cooperation with surface membrane ion channels.
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Affiliation(s)
- Konstantin Y Bogdanov
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, NIH, 5600 Nathan Shock Dr, Baltimore, MD 21224-6825, USA.
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35
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Vinogradova TM, Lyashkov AE, Zhu W, Ruknudin AM, Sirenko S, Yang D, Deo S, Barlow M, Johnson S, Caffrey JL, Zhou YY, Xiao RP, Cheng H, Stern MD, Maltsev VA, Lakatta EG. High basal protein kinase A-dependent phosphorylation drives rhythmic internal Ca2+ store oscillations and spontaneous beating of cardiac pacemaker cells. Circ Res 2006; 98:505-14. [PMID: 16424365 DOI: 10.1161/01.res.0000204575.94040.d1] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Local, rhythmic, subsarcolemmal Ca2+ releases (LCRs) from the sarcoplasmic reticulum (SR) during diastolic depolarization in sinoatrial nodal cells (SANC) occur even in the basal state and activate an inward Na(+)-Ca2+ exchanger current that affects spontaneous beating. Why SANC can generate spontaneous LCRs under basal conditions, whereas ventricular cells cannot, has not previously been explained. Here we show that a high basal cAMP level of isolated rabbit SANC and its attendant increase in protein kinase A (PKA)-dependent phosphorylation are obligatory for the occurrence of spontaneous, basal LCRs and for spontaneous beating. Gradations in basal PKA activity, indexed by gradations in phospholamban phosphorylation effected by a specific PKA inhibitory peptide were highly correlated with concomitant gradations in LCR spatiotemporal synchronization and phase, as well as beating rate. Higher levels of basal PKA inhibition abolish LCRs and spontaneous beating ceases. Stimulation of beta-adrenergic receptors extends the range of PKA-dependent control of LCRs and beating rate beyond that in the basal state. The link between SR Ca2+ cycling and beating rate is also present in vivo, as the regulation of beating rate by local beta-adrenergic receptor stimulation of the sinoatrial node in intact dogs is markedly blunted when SR Ca2+ cycling is disrupted by ryanodine. Thus, PKA-dependent phosphorylation of proteins that regulate cell Ca2+ balance and spontaneous SR Ca2+ cycling, ie, phospholamban and L-type Ca2+ channels (and likely others not measured in this study), controls the phase and size of LCRs and the resultant Na(+)-Ca2+ exchanger current and is crucial for both basal and reserve cardiac pacemaker function.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, NIH, Baltimore, MD 21224-6825, USA
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36
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Vinogradova TM, Maltsev VA, Bogdanov KY, Lyashkov AE, Lakatta EG. Rhythmic Ca2+Oscillations Drive Sinoatrial Nodal Cell Pacemaker Function to Make the Heart Tick. Ann N Y Acad Sci 2006; 1047:138-56. [PMID: 16093492 DOI: 10.1196/annals.1341.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Excitation-induced Ca(2+) cycling into and out of the cytosol via the sarcoplasmic reticulum (SR) Ca(2+) pump, ryanodine receptor (RyR) and Na(+)-Ca(2+) exchanger (NCX) proteins, and modulation of this Ca(2+)cycling by beta-adrenergic receptor (beta-AR) stimulation, governs the strength of ventricular myocyte contraction and the cardiac contractile reserve. Recent evidence indicates that heart rate modulation and chronotropic reserve via beta-ARs also involve intracellular Ca(2+) cycling by these very same molecules. Specifically, sinoatrial nodal pacemaker cells (SANC), even in the absence of surface membrane depolarization, generate localized rhythmic, submembrane Ca(2+) oscillations via SR Ca(2+) pumping-RyR Ca(2+) release. During spontaneous SANC beating, these rhythmic, spontaneous Ca(2+) oscillations are interrupted by the occurrence of an action potential (AP), which activates L-type Ca(2+) channels to trigger SR Ca(2+) release, unloading the SR Ca(2+) content and inactivating RyRs. During the later part of the subsequent diastolic depolarization (DD), when Ca(2+) pumped back into the SR sufficiently replenishes the SR Ca(2+) content, and Ca(2+)-dependent RyR inactivation wanes, the spontaneous release of Ca(2+) via RyRs again begins to occur. The local increase in submembrane [Ca(2+)] generates an inward current via NCX, enhancing the DD slope, modulating the occurrence of the next AP, and thus the beating rate. Beta-AR stimulation increases the submembrane Ca(2+) oscillation amplitude and reduces the period (the time from the prior AP triggered SR Ca(2+) release to the onset of the local Ca(2+) release during the subsequent DD). This increased amplitude and phase shift causes the NCX current to occur at earlier times following a prior beat, promoting the earlier arrival of the next beat and thus an increase in the spontaneous firing rate. Ca(2+) cycling via the SR Ca(2+) pump, RyR and NCX, and its modulation by beta-AR stimulation is, therefore, a general mechanism of cardiac chronotropy and inotropy.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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