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Abstract
Calcium ions (Ca2+) are the basis of a unique and potent array of cellular responses. Calmodulin (CaM) is a small but vital protein that is able to rapidly transmit information about changes in Ca2+ concentrations to its regulatory targets. CaM plays a critical role in cellular Ca2+ signaling, and interacts with a myriad of target proteins. Ca2+-dependent modulation by CaM is a major component of a diverse array of processes, ranging from gene expression in neurons to the shaping of the cardiac action potential in heart cells. Furthermore, the protein sequence of CaM is highly evolutionarily conserved, and identical CaM proteins are encoded by three independent genes (CALM1-3) in humans. Mutations within any of these three genes may lead to severe cardiac deficits including severe long QT syndrome (LQTS) and/or catecholaminergic polymorphic ventricular tachycardia (CPVT). Research into disease-associated CaM variants has identified several proteins modulated by CaM that are likely to underlie the pathogenesis of these calmodulinopathies, including the cardiac L-type Ca2+ channel (LTCC) CaV1.2, and the sarcoplasmic reticulum Ca2+ release channel, ryanodine receptor 2 (RyR2). Here, we review the research that has been done to identify calmodulinopathic CaM mutations and evaluate the mechanisms underlying their role in disease.
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Affiliation(s)
- John W. Hussey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Worawan B. Limpitikul
- Department of Medicine, Division of Cardiology, Massachusetts General Hospital, Boston, MA, USA
| | - Ivy E. Dick
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- CONTACT Ivy E. Dick School of Medicine, University of Maryland, Baltimore, MD21210
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Limpitikul WB, Das S. Obesity-Related Atrial Fibrillation: Cardiac Manifestation of a Systemic Disease. J Cardiovasc Dev Dis 2023; 10:323. [PMID: 37623336 PMCID: PMC10455513 DOI: 10.3390/jcdd10080323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/27/2023] [Accepted: 07/27/2023] [Indexed: 08/26/2023] Open
Abstract
Atrial fibrillation (AF) is the most common arrhythmia worldwide and is associated with increased morbidity and mortality. The mechanisms underlying AF are complex and multifactorial. Although it is well known that obesity is a strong risk factor for AF, the mechanisms underlying obesity-related AF are not completely understood. Current evidence proposes that in addition to overall hemodynamic changes due to increased body weight, excess adiposity raises systemic inflammation and oxidative stress, which lead to adverse atrial remodeling. This remodeling includes atrial fibrosis, atrial dilation, decreased electrical conduction between atrial myocytes, and altered ionic currents, making atrial tissue more vulnerable to both the initiation and maintenance of AF. However, much remains to be learned about the mechanistic links between obesity and AF. This knowledge will power the development of novel diagnostic tools and treatment options that will help combat the rise of the global AF burden among the obesity epidemic.
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Affiliation(s)
- Worawan B. Limpitikul
- Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA;
| | - Saumya Das
- Cardiovascular Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA;
- Demoulas Family Foundation Center for Cardiac Arrhythmias, Massachusetts General Hospital, Boston, MA 02114, USA
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Limpitikul WB, Dewland TA, Vittinghoff E, Soliman E, Nah G, Fang C, Siscovick DS, Psaty BM, Sotoodehnia N, Heckbert S, Stein PK, Gottdiener J, Hu X, Hempfling R, Marcus GM. Premature ventricular complexes and development of heart failure in a community-based population. Heart 2022; 108:105-110. [PMID: 34493549 PMCID: PMC8702448 DOI: 10.1136/heartjnl-2021-319473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 08/09/2021] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVE A higher premature ventricular complex (PVC) frequency is associated with incident congestive heart failure (CHF) and death. While certain PVC characteristics may contribute to that risk, the current literature stems from patients in medical settings and is therefore prone to referral bias. This study aims to identify PVC characteristics associated with incident CHF in a community-based setting. METHODS The Cardiovascular Health Study is a cohort of community-dwelling individuals who underwent prospective evaluation and follow-up. We analysed 24-hour Holter data to assess PVC characteristics and used multivariable logistic and Cox proportional hazards models to identify predictors of a left ventricular ejection fraction (LVEF) decline and incident CHF, respectively. RESULTS Of 871 analysed participants, 316 participants exhibited at least 10 PVCs during the 24-hour recording. For participants with PVCs, the average age was 72±5 years, 41% were women and 93% were white. Over a median follow-up of 11 years, 34% developed CHF. After adjusting for demographics, cardiovascular comorbidities, antiarrhythmic drug use and PVC frequency, a greater heterogeneity of the PVC coupling interval was associated with an increased risk of LVEF decline and incident CHF. Of note, neither PVC duration nor coupling interval duration exhibited a statistically significant relationship with either outcome. CONCLUSIONS In this first community-based study to identify Holter-based features of PVCs that are associated with LVEF reduction and incident CHF, the fact that coupling interval heterogeneity was an independent risk factor suggests that the mechanism of PVC generation may influence the risk of heart failure.
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Affiliation(s)
- Worawan B Limpitikul
- Medicine, University of California San Francisco, San Francisco, California, USA
| | - Thomas A Dewland
- Division of Cardiology, Electrophysiology Section, University of California San Francisco, San Francisco, California, USA
| | - Eric Vittinghoff
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, USA
| | - Elsayed Soliman
- Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Gregory Nah
- Division of Cardiology, Electrophysiology Section, University of California San Francisco, San Francisco, California, USA
| | - Christina Fang
- Division of Cardiology, Electrophysiology Section, University of California San Francisco, San Francisco, California, USA
| | | | - Bruce M Psaty
- Cardiovascular Health Research Unit, Departments of Medicine, Epidemiology, and Health Services, University of Washington, Seattle, Washington, USA
| | - Nona Sotoodehnia
- Division of Cardiology, University of Washington, Seattle, Washington, USA
| | - Susan Heckbert
- Cardiovascular Health Research Unit, Departments of Medicine, Epidemiology, and Health Services, University of Washington, Seattle, Washington, USA
| | - Phyllis K Stein
- Cardiovascular Division, Washington University School of Medicine in Saint Louis, St Louis, Missouri, USA
| | - John Gottdiener
- Cardiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Xiao Hu
- Duke University School of Nursing, Durham, North Carolina, USA
| | | | - Gregory M Marcus
- Division of Cardiology, Electrophysiology Section, University of California San Francisco, San Francisco, California, USA
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Limpitikul WB, Viswanathan MC, O'Rourke B, Yue DT, Cammarato A. L-Type Calcium Channels are a Major Source of Plasmalemmel Calcium Influx for Drosophila Cardiomyocytes. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.848] [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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Blice-Baum AC, Vogler G, Viswanathan MC, Trinh B, Limpitikul WB, Cammarato A. Quantifying Tissue-Specific Overexpression of FOXO in Drosophila via mRNA Fluorescence In Situ Hybridization Using Branched DNA Probe Technology. Methods Mol Biol 2019; 1890:171-190. [PMID: 30414154 PMCID: PMC7906431 DOI: 10.1007/978-1-4939-8900-3_15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
While the highly conserved FOXO transcription factors have been studied in Drosophila melanogaster for decades, the ability to accurately control and measure their tissue-specific expression is often cumbersome due to a lack of reagents and to limited, nonhomogeneous samples. The need for quantitation within a distinct cell type is particularly important because transcription factors must be expressed in specific amounts to perform their functions properly. However, the inherent heterogeneity of many samples can make evaluating cell-specific FOXO and/or FOXO load difficult. Here, we describe an extremely sensitive fluorescence in situ hybridization (FISH) approach for visualizing and quantifying multiple mRNAs with single-cell resolution in adult Drosophila cardiomyocytes. The procedure relies upon branched DNA technology, which allows several fluorescent molecules to label an individual transcript, drastically increasing the signal-to-noise ratio compared to other FISH assays. This protocol can be modified for use in various small animal models, tissue types, and for assorted nucleic acids.
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Affiliation(s)
- Anna C Blice-Baum
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Science Department, Iadarola Center for Science, Education and Technology, Cabrini University, Radnor, PA, USA.
| | - Georg Vogler
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
| | - Meera C Viswanathan
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bosco Trinh
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Worawan B Limpitikul
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Limpitikul WB, Greenstein JL, Yue DT, Dick IE, Winslow RL. A bilobal model of Ca 2+-dependent inactivation to probe the physiology of L-type Ca 2+ channels. J Gen Physiol 2018; 150:1688-1701. [PMID: 30470716 PMCID: PMC6279366 DOI: 10.1085/jgp.201812115] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 08/01/2018] [Accepted: 10/26/2018] [Indexed: 12/20/2022] Open
Abstract
L-type calcium channels undergo Ca2+-dependent inactivation (CDI) in order to precisely control the entry of Ca2+ into cells such as cardiomyocytes. Limpitikul et al. develop a bilobal model of CDI and use it to understand the pathogenesis of arrhythmias associated with mutations in CaM. L-type calcium channels (LTCCs) are critical elements of normal cardiac function, playing a major role in orchestrating cardiac electrical activity and initiating downstream signaling processes. LTCCs thus use feedback mechanisms to precisely control calcium (Ca2+) entry into cells. Of these, Ca2+-dependent inactivation (CDI) is significant because it shapes cardiac action potential duration and is essential for normal cardiac rhythm. This important form of regulation is mediated by a resident Ca2+ sensor, calmodulin (CaM), which is comprised of two lobes that are each capable of responding to spatially distinct Ca2+ sources. Disruption of CaM-mediated CDI leads to severe forms of long-QT syndrome (LQTS) and life-threatening arrhythmias. Thus, a model capable of capturing the nuances of CaM-mediated CDI would facilitate increased understanding of cardiac (patho)physiology. However, one critical barrier to achieving a detailed kinetic model of CDI has been the lack of quantitative data characterizing CDI as a function of Ca2+. This data deficit stems from the experimental challenge of uncoupling the effect of channel gating on Ca2+ entry. To overcome this obstacle, we use photo-uncaging of Ca2+ to deliver a measurable Ca2+ input to CaM/LTCCs, while simultaneously recording CDI. Moreover, we use engineered CaMs with Ca2+ binding restricted to a single lobe, to isolate the kinetic response of each lobe. These high-resolution measurements enable us to build mathematical models for each lobe of CaM, which we use as building blocks for a full-scale bilobal model of CDI. Finally, we use this model to probe the pathogenesis of LQTS associated with mutations in CaM (calmodulinopathies). Each of these models accurately recapitulates the kinetics and steady-state properties of CDI in both physiological and pathological states, thus offering powerful new insights into the mechanistic alterations underlying cardiac arrhythmias.
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Affiliation(s)
- Worawan B Limpitikul
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Joseph L Greenstein
- Institute for Computational Medicine, Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Ivy E Dick
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD .,Department of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Raimond L Winslow
- Institute for Computational Medicine, Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD
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Limpitikul WB, Viswanathan MC, O'Rourke B, Yue DT, Cammarato A. Conservation of cardiac L-type Ca 2+ channels and their regulation in Drosophila: A novel genetically-pliable channelopathic model. J Mol Cell Cardiol 2018; 119:64-74. [PMID: 29684406 DOI: 10.1016/j.yjmcc.2018.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [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: 11/10/2017] [Revised: 04/08/2018] [Accepted: 04/11/2018] [Indexed: 01/28/2023]
Abstract
Dysregulation of L-type Ca2+ channels (LTCCs) underlies numerous cardiac pathologies. Understanding their modulation with high fidelity relies on investigating LTCCs in their native environment with intact interacting proteins. Such studies benefit from genetic manipulation of endogenous channels in cardiomyocytes, which often proves cumbersome in mammalian models. Drosophila melanogaster, however, offers a potentially efficient alternative as it possesses a relatively simple heart, is genetically pliable, and expresses well-conserved genes. Fluorescence in situ hybridization confirmed an abundance of Ca-α1D and Ca-α1T mRNA in fly myocardium, which encode subunits that specify hetero-oligomeric channels homologous to mammalian LTCCs and T-type Ca2+ channels, respectively. Cardiac-specific knockdown of Ca-α1D via interfering RNA abolished cardiac contraction, suggesting Ca-α1D (i.e. A1D) represents the primary functioning Ca2+ channel in Drosophila hearts. Moreover, we successfully isolated viable single cardiomyocytes and recorded Ca2+ currents via patch clamping, a feat never before accomplished with the fly model. The profile of Ca2+ currents recorded in individual cells when Ca2+ channels were hypomorphic, absent, or under selective LTCC blockage by nifedipine, additionally confirmed the predominance of A1D current across all activation voltages. T-type current, activated at more negative voltages, was also detected. Lastly, A1D channels displayed Ca2+-dependent inactivation, a critical negative feedback mechanism of LTCCs, and the current through them was augmented by forskolin, an activator of the protein kinase A pathway. In sum, the Drosophila heart possesses a conserved compendium of Ca2+ channels, suggesting that the fly may serve as a robust and effective platform for studying cardiac channelopathies.
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Affiliation(s)
- Worawan B Limpitikul
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States
| | - Meera C Viswanathan
- Institute of CardioScience, Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States
| | - Brian O'Rourke
- Institute of CardioScience, Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States
| | - Anthony Cammarato
- Institute of CardioScience, Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States; Department of Physiology, The Johns Hopkins University School of Medicine, Ross Research Building, 720 Rutland Avenue, Baltimore, MD 21205, United States.
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Limpitikul WB, Dick IE, Tester DJ, Boczek NJ, Limphong P, Yang W, Choi MH, Babich J, DiSilvestre D, Kanter RJ, Tomaselli GF, Ackerman MJ, Yue DT. A Precision Medicine Approach to the Rescue of Function on Malignant Calmodulinopathic Long-QT Syndrome. Circ Res 2016; 120:39-48. [PMID: 27765793 DOI: 10.1161/circresaha.116.309283] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [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: 06/11/2016] [Revised: 10/17/2016] [Accepted: 10/20/2016] [Indexed: 12/24/2022]
Abstract
RATIONALE Calmodulinopathies comprise a new category of potentially life-threatening genetic arrhythmia syndromes capable of producing severe long-QT syndrome (LQTS) with mutations involving CALM1, CALM2, or CALM3. The underlying basis of this form of LQTS is a disruption of Ca2+/calmodulin (CaM)-dependent inactivation of L-type Ca2+ channels. OBJECTIVE To gain insight into the mechanistic underpinnings of calmodulinopathies and devise new therapeutic strategies for the treatment of this form of LQTS. METHODS AND RESULTS We generated and characterized the functional properties of induced pluripotent stem cell-derived cardiomyocytes from a patient with D130G-CALM2-mediated LQTS, thus creating a platform with which to devise and test novel therapeutic strategies. The patient-derived induced pluripotent stem cell-derived cardiomyocytes display (1) significantly prolonged action potentials, (2) disrupted Ca2+ cycling properties, and (3) diminished Ca2+/CaM-dependent inactivation of L-type Ca2+ channels. Next, taking advantage of the fact that calmodulinopathy patients harbor a mutation in only 1 of 6 redundant CaM-encoding alleles, we devised a strategy using CRISPR interference to selectively suppress the mutant gene while sparing the wild-type counterparts. Indeed, suppression of CALM2 expression produced a functional rescue in induced pluripotent stem cell-derived cardiomyocytes with D130G-CALM2, as shown by the normalization of action potential duration and Ca2+/CaM-dependent inactivation after treatment. Moreover, CRISPR interference can be designed to achieve selective knockdown of any of the 3 CALM genes, making it a generalizable therapeutic strategy for any calmodulinopathy. CONCLUSIONS Overall, this therapeutic strategy holds great promise for calmodulinopathy patients as it represents a generalizable intervention capable of specifically altering CaM expression and potentially attenuating LQTS-triggered cardiac events, thus initiating a path toward precision medicine.
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Affiliation(s)
- Worawan B Limpitikul
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Ivy E Dick
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - David J Tester
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Nicole J Boczek
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Pattraranee Limphong
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Wanjun Yang
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Myoung Hyun Choi
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Jennifer Babich
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Deborah DiSilvestre
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Ronald J Kanter
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - Gordon F Tomaselli
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.).
| | - Michael J Ackerman
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
| | - David T Yue
- From the Calcium Signals Laboratory, Department of Biomedical Engineering (W.B.L., I.E.D., W.Y., M.H.C., J.B., D.T.Y.) and Division of Cardiology, Department of Medicine (P.L., D.D., G.F.T.), The Johns Hopkins University School of Medicine, Baltimore, MD; Department of Physiology, The University of Maryland School of Medicine, Baltimore (I.E.D.); Division of Heart Rhythm Services, Department of Cardiovascular Diseases (D.J.T., N.J.B., M.J.A.), Division of Pediatric Cardiology, Department of Pediatrics (D.J.T., N.J.B., M.J.A.), and Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics (D.J.T., N.J.B., M.J.A.), Mayo Clinic, Rochester, MN; and Division of Cardiology, Nicklaus Children's Hospital, Miami, FL (R.J.K.)
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9
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Ben-Johny M, Dick IE, Sang L, Limpitikul WB, Kang PW, Niu J, Banerjee R, Yang W, Babich JS, Issa JB, Lee SR, Namkung H, Li J, Zhang M, Yang PS, Bazzazi H, Adams PJ, Joshi-Mukherjee R, Yue DN, Yue DT. Towards a Unified Theory of Calmodulin Regulation (Calmodulation) of Voltage-Gated Calcium and Sodium Channels. Curr Mol Pharmacol 2016; 8:188-205. [PMID: 25966688 DOI: 10.2174/1874467208666150507110359] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 01/29/2015] [Accepted: 04/20/2015] [Indexed: 12/13/2022]
Abstract
Voltage-gated Na and Ca(2+) channels represent two major ion channel families that enable myriad biological functions including the generation of action potentials and the coupling of electrical and chemical signaling in cells. Calmodulin regulation (calmodulation) of these ion channels comprises a vital feedback mechanism with distinct physiological implications. Though long-sought, a shared understanding of the channel families remained elusive for two decades as the functional manifestations and the structural underpinnings of this modulation often appeared to diverge. Here, we review recent advancements in the understanding of calmodulation of Ca(2+) and Na channels that suggest a remarkable similarity in their regulatory scheme. This interrelation between the two channel families now paves the way towards a unified mechanistic framework to understand vital calmodulin-dependent feedback and offers shared principles to approach related channelopathic diseases. An exciting era of synergistic study now looms.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - David T Yue
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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10
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Limpitikul WB, Dick IE, Ben-Johny M, Yue DT. An autism-associated mutation in CaV1.3 channels has opposing effects on voltage- and Ca(2+)-dependent regulation. Sci Rep 2016; 6:27235. [PMID: 27255217 PMCID: PMC4891671 DOI: 10.1038/srep27235] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/13/2016] [Indexed: 01/07/2023] Open
Abstract
CaV1.3 channels are a major class of L-type Ca(2+) channels which contribute to the rhythmicity of the heart and brain. In the brain, these channels are vital for excitation-transcription coupling, synaptic plasticity, and neuronal firing. Moreover, disruption of CaV1.3 function has been associated with several neurological disorders. Here, we focus on the de novo missense mutation A760G which has been linked to autism spectrum disorder (ASD). To explore the role of this mutation in ASD pathogenesis, we examined the effects of A760G on CaV1.3 channel gating and regulation. Introduction of the mutation severely diminished the Ca(2+)-dependent inactivation (CDI) of CaV1.3 channels, an important feedback system required for Ca(2+) homeostasis. This reduction in CDI was observed in two major channel splice variants, though to different extents. Using an allosteric model of channel gating, we found that the underlying mechanism of CDI reduction is likely due to enhanced channel opening within the Ca(2+)-inactivated mode. Remarkably, the A760G mutation also caused an opposite increase in voltage-dependent inactivation (VDI), resulting in a multifaceted mechanism underlying ASD. When combined, these regulatory deficits appear to increase the intracellular Ca(2+) concentration, thus potentially disrupting neuronal development and synapse formation, ultimately leading to ASD.
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Affiliation(s)
- Worawan B Limpitikul
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Ivy E Dick
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Manu Ben-Johny
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
| | - David T Yue
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713,720 Rutland Avenue, Baltimore, MD 21205, USA
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11
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DeMazumder D, Limpitikul WB, Dorante M, Dey S, Mukhopadhyay B, Zhang Y, Moorman JR, Cheng A, Berger RD, Guallar E, Jones SR, Tomaselli GF. Entropy of cardiac repolarization predicts ventricular arrhythmias and mortality in patients receiving an implantable cardioverter-defibrillator for primary prevention of sudden death. Europace 2016; 18:1818-1828. [PMID: 27044982 DOI: 10.1093/europace/euv399] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 11/03/2015] [Indexed: 11/12/2022] Open
Abstract
AIMS The need for a readily available, inexpensive, non-invasive method for improved risk stratification of heart failure (HF) patients is paramount. Prior studies have proposed that distinct fluctuation patterns underlying the variability of physiological signals have unique prognostic value. We tested this hypothesis in an extensively phenotyped cohort of HF patients using EntropyXQT, a novel non-linear measure of cardiac repolarization dynamics. METHODS AND RESULTS In a prospective, multicentre, observational study of 852 patients in sinus rhythm undergoing clinically indicated primary prevention implantable cardioverter-defibrillator (ICD) implantation (2003-10), exposures included demographics, history, physical examination, medications, laboratory results, serum biomarkers, ejection fraction, conventional electrocardiographic (ECG) analyses of heart rate and QT variability, and EntropyXQT. The primary outcome was first 'appropriate' ICD shock for ventricular arrhythmias. The secondary outcome was composite events (appropriate ICD shock and all-cause mortality). After exclusions, the cohort (n = 816) had a mean age of 60 ± 13 years, 28% women, 36% African Americans, 56% ischaemic cardiomyopathy, and 29 ± 16% Seattle HF risk score (SHFS) 5-year predicted mortality. Over 45 ± 24 months, there were 134 appropriate shocks and 166 deaths. After adjusting for 30 exposures, the hazard ratios (comparing the 5th to 1st quintile of EntropyXQT) for primary and secondary outcomes were 3.29 (95% CI 1.74-6.21) and 2.28 (1.53-3.41), respectively. Addition of EntropyXQT to a model comprised of the exposures or SHFS significantly increased net reclassification and the ROC curve area. CONCLUSIONS EntropyXQT measured during ICD implantation strongly and independently predicts appropriate shock and all-cause mortality over follow-up. EntropyXQT complements conventional risk predictors and has the potential for broad clinical application.
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Affiliation(s)
- Deeptankar DeMazumder
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Worawan B Limpitikul
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Miguel Dorante
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Swati Dey
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Bhasha Mukhopadhyay
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Yiyi Zhang
- Department of Epidemiology and Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - J Randall Moorman
- Division of Cardiology, University of Virginia, Charlottesville, VA, USA
| | - Alan Cheng
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Ronald D Berger
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Eliseo Guallar
- Department of Epidemiology and Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Steven R Jones
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
| | - Gordon F Tomaselli
- Division of Cardiology, Johns Hopkins University School of Medicine, 720 North Rutland Avenue, Ross 844, Baltimore, MD 21205, USA
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12
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Limpitikul WB, Limphong P, Dick IE, Hyun Choi M, Yang W, Babich J, Tester DJ, Ackerman MJ, Tomaselli GF, Yue DT. Functional Rescue of Calmodulinopathy IPSC-Derived Cardiomyocytes -- a Foray into Personalized Medicine. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2367] [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: 11/28/2022] Open
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13
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Dick IE, Joshi-Mukherjee R, Yang W, Limpitikul WB, Yue DT. Toward a new Therapeutic Strategy in the Treatment of Timothy Syndrome. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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14
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Limpitikul WB, Viswanathan MC, Cammarato A, Yue DT. Abstract 336: Conservation of Cardiac L-type Ca2+ Channels and Their Modulation in Drosophila: a Novel Genetically Pliable Channelopathic Model. Circ Res 2015. [DOI: 10.1161/res.117.suppl_1.336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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
Misregulation of L-type Ca
2+
channels (LTCCs) underlies numerous cardiac pathologies. For example, heart failure features blunted protein kinase A (PKA) upregulation of the LTCCs. However, studying LTCC regulation in mammalian systems is challenging due to complex physiology and lack of genetic manipulability while recombinant channels expressed in heterologous systems, which lack key auxiliary elements, poorly represent the native context.
Drosophila
, however, has a simple heart with many conserved genes and is genetically pliable. Thus, we pinpointed the signature of Ca
2+
channels (CCs) in the fly cardiac tubes. First, RNAi-mediated selective knockdown of Dmca1D, homologous to the human LTCCs, abolished cardiac contraction (B, as compared to ctrl in A), establishing this channel isoform as the primary CC in fly hearts. Second, we successfully isolated viable single fly cardiomyocytes (C, inset) and recorded robust Ca
2+
currents using patch clamp electrophysiology (C), a feat never before accomplished for the fly cardiac system. Moreover, recording Ca
2+
currents in distinct hypomorphic CC lines, we confirmed the CC type in the fly heart. We also observed pharmacological responses of the CCs that were strikingly similar to those seen in humans. Current through Dmca1D is blocked by a dihydropiridine, nifedipine (C), and is readily upregulated by forskolin, a downstream activator of the PKA pathway (C). In all, we have established the existence of a conserved compendium of cardiac CCs in fly heart tubes, suggesting that
Drosophila
may serve as a robust and effective platform to study the pathophysiology of diseases involving cardiac CCs and to devise therapeutic strategies.
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Affiliation(s)
| | | | | | - David T Yue
- Johns Hopkins Univ Sch of Medicine, Baltimore, MD
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15
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Dick IE, Limpitikul WB, Niu J, Banerjee R, Issa JB, Ben-Johny M, Adams PJ, Kang PW, Lee SR, Sang L, Yang W, Babich J, Zhang M, Bazazzi H, Yue NC, Tomaselli GF. A rendezvous with the queen of ion channels: Three decades of ion channel research by David T Yue and his Calcium Signals Laboratory. Channels (Austin) 2015; 10:20-32. [PMID: 26176690 DOI: 10.1080/19336950.2015.1051272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
David T. Yue was a renowned biophysicist who dedicated his life to the study of Ca(2+) signaling in cells. In the wake of his passing, we are left not only with a feeling of great loss, but with a tremendous and impactful body of work contributed by a remarkable man. David's research spanned the spectrum from atomic structure to organ systems, with a quantitative rigor aimed at understanding the fundamental mechanisms underlying biological function. Along the way he developed new tools and approaches, enabling not only his own research but that of his contemporaries and those who will come after him. While we cannot hope to replicate the eloquence and style we are accustomed to in David's writing, we nonetheless undertake a review of David's chosen field of study with a focus on many of his contributions to the calcium channel field.
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Affiliation(s)
- Ivy E Dick
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Worawan B Limpitikul
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Jacqueline Niu
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Rahul Banerjee
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - John B Issa
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Manu Ben-Johny
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Paul J Adams
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA.,b Kwantlen Polytechnic University ; Surrey , BC Canada
| | - Po Wei Kang
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Shin Rong Lee
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Lingjie Sang
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Wanjun Yang
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Jennifer Babich
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Manning Zhang
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Hojjat Bazazzi
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Nancy C Yue
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
| | - Gordon F Tomaselli
- a Calcium Signals Laboratory; Department of Biomedical Engineering ; Johns Hopkins University School of Medicine ; Baltimore , MD USA.,c Division of Cardiology; Department of Medicine ; Johns Hopkins University School of Medicine ; Baltimore , MD USA
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16
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Limpitikul WB, Dick IE, Joshi-Mukherjee R, Overgaard MT, George AL, Yue DT. Calmodulin mutations associated with long QT syndrome prevent inactivation of cardiac L-type Ca(2+) currents and promote proarrhythmic behavior in ventricular myocytes. J Mol Cell Cardiol 2014; 74:115-24. [PMID: 24816216 DOI: 10.1016/j.yjmcc.2014.04.022] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 04/28/2014] [Indexed: 01/13/2023]
Abstract
Recent work has identified missense mutations in calmodulin (CaM) that are associated with severe early-onset long-QT syndrome (LQTS), leading to the proposition that altered CaM function may contribute to the molecular etiology of this subset of LQTS. To date, however, no experimental evidence has established these mutations as directly causative of LQTS substrates, nor have the molecular targets of CaM mutants been identified. Here, therefore, we test whether expression of CaM mutants in adult guinea-pig ventricular myocytes (aGPVM) induces action-potential prolongation, and whether affiliated alterations in the Ca(2+) regulation of L-type Ca(2+) channels (LTCC) might contribute to such prolongation. In particular, we first overexpressed CaM mutants in aGPVMs, and observed both increased action potential duration (APD) and heightened Ca(2+) transients. Next, we demonstrated that all LQTS CaM mutants have the potential to strongly suppress Ca(2+)/CaM-dependent inactivation (CDI) of LTCCs, whether channels were heterologously expressed in HEK293 cells, or present in native form within myocytes. This attenuation of CDI is predicted to promote action-potential prolongation and boost Ca(2+) influx. Finally, we demonstrated how a small fraction of LQTS CaM mutants (as in heterozygous patients) would nonetheless suffice to substantially diminish CDI, and derange electrical and Ca(2+) profiles. In all, these results highlight LTCCs as a molecular locus for understanding and treating CaM-related LQTS in this group of patients.
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Affiliation(s)
- Worawan B Limpitikul
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ivy E Dick
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Rosy Joshi-Mukherjee
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Michael T Overgaard
- Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Denmark
| | - Alfred L George
- Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205; Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205.
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