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Carvajal C, Yan J, Nani A, DeSantiago J, Wan X, Deschenes I, Ai X, Fill M. Isolated Cardiac Ryanodine Receptor Function Varies Between Mammals. J Membr Biol 2024; 257:25-36. [PMID: 38285125 DOI: 10.1007/s00232-023-00301-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/24/2023] [Indexed: 01/30/2024]
Abstract
Concerted robust opening of cardiac ryanodine receptors' (RyR2) Ca2+ release 1oplasmic reticulum (SR) is fundamental for normal systolic cardiac function. During diastole, infrequent spontaneous RyR2 openings mediate the SR Ca2+ leak that normally constrains SR Ca2+ load. Abnormal large diastolic RyR2-mediated Ca2+ leak events can cause delayed after depolarizations (DADs) and arrhythmias. The RyR2-associated mechanisms underlying these processes are being extensively studied at multiple levels utilizing various model animals. Since there are well-described species-specific differences in cardiac intracellular Ca2+ handing in situ, we tested whether or not single RyR2 function in vitro retains this species specificity. We isolated RyR2-rich heavy SR microsomes from mouse, rat, rabbit, and human ventricular muscle and quantified RyR2 function using identical solutions and methods. The single RyR2 cytosolic Ca2+ sensitivity was similar across these species. However, there were significant species differences in single RyR2 mean open times in both systole and diastole-like solutions. In diastole-like solutions, single rat/mouse RyR2 open probability and frequency of long openings (> 6 ms) were similar, but these values were significantly greater than those of either single rabbit or human RyR2s. We propose these in vitro single RyR2 functional differences across species stem from the species-specific RyR2 regulatory environment present in the source tissue. Our results show the single rabbit RyR2 functional attributes, particularly in diastole-like conditions, replicate those of single human RyR2 best among the species tested.
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Affiliation(s)
- Catherine Carvajal
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Jiajie Yan
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Alma Nani
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Jaime DeSantiago
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Xiaoping Wan
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Isabelle Deschenes
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Xun Ai
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA.
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA.
| | - Michael Fill
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA.
- Department of Molecular Biophysics & Physiology, Rush University Medical Center, 1750 West Harrison Street, Columbus, OH, 43210, USA.
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Askarinejad A, Esmaeili S, Dalili M, Biglari A, Kohansal E, Maleki M, Kalayinia S. Catecholaminergic polymorphic ventricular tachycardia (and seizure) caused by a novel homozygous likely pathogenic variant in CASQ2 gene. Gene 2024; 895:148012. [PMID: 37995796 DOI: 10.1016/j.gene.2023.148012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/15/2023] [Indexed: 11/25/2023]
Abstract
BACKGROUND Although structural heart disease is frequently present among patients who experience sudden cardiac death (SCD), inherited arrhythmia syndromes can also play an important role in the occurrence of SCD. CPVT2, which is the second-most prevalent form of CPVT, arises from an abnormality in the CASQ2 gene. OBJECTIVE We represent a novel CASQ2 variant that causes CPVT2 and conduct a comprehensive review on this topic. METHODS The proband underwent Whole-exome sequencing (WES) in order to ascertain the etiology of CPVT. Subsequently, the process of segregating the available family members was carried out through the utilization of PCR and Sanger Sequencing. We searched the google scholar and PubMed/Medline for studies reporting CASQ2 variants, published up to May 10,2023. We used the following mesh term "Calsequestrin" and using free-text method with terms including "CASQ2","CASQ2 variants", and "CASQ2 mutation". RESULTS The CASQ2 gene was found to contain an autosomal recessive nonsense variant c.268_269insTA:p.Gly90ValfsTer4, which was identified by WES. This variant was determined to be the most probable cause of CPVT in the pedigree under investigation. CONCLUSION CASQ2 variants play an important role in pathogenesis of CPVT2. Notabely, based on results of our study and other findings in the literature the variant in this gene may cause an neurological signs in the patients with CPVT2. Further studies are needed for more details about the role of this gene in CPVT evaluation, diagnosis, and gene therapy.
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Affiliation(s)
- Amir Askarinejad
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran University of Medical Sciences, Tehran, Iran
| | - Shiva Esmaeili
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran University of Medical Sciences, Tehran, Iran
| | - Mohamad Dalili
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran University of Medical Sciences, Tehran, Iran
| | - Alireza Biglari
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran University of Medical Sciences, Tehran, Iran
| | - Erfan Kohansal
- Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran University of Medical Sciences, Tehran, Iran
| | - Majid Maleki
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Samira Kalayinia
- Cardiogenetic Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.
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Pérez PR, Hylind RJ, Roston TM, Bezzerides VJ, Abrams DJ. Gene Therapy for Catecholaminergic Polymorphic Ventricular Tachycardia. Heart Lung Circ 2023; 32:790-797. [PMID: 37032191 DOI: 10.1016/j.hlc.2023.01.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 10/13/2022] [Accepted: 01/04/2023] [Indexed: 04/11/2023]
Abstract
Over the last three decades, the genetic basis of various inherited arrhythmia syndromes has been elucidated, providing key insights into cardiomyocyte biology and various regulatory pathways associated with cellular excitation, contraction, and repolarisation. As varying techniques to manipulate genetic sequence, gene expression, and different cellular pathways have become increasingly defined and understood, the potential to apply various gene-based therapies to inherited arrhythmia has been explored. The promise of gene therapy has generated significant interest in the medical and lay press, providing hope for sufferers of seemingly incurable disorders to imagine a future without repeated medical intervention, and, in the case of various cardiac disorders, without the risk of sudden death. In this review, we focus on catecholaminergic polymorphic ventricular tachycardia (CPVT), discussing the clinical manifestations, genetic basis, and molecular biology, together with current avenues of research related to gene therapy.
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Affiliation(s)
- Paloma Remior Pérez
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA; Department of Cardiology, Hospital Universitario Puerta de Hierro, Madrid, Spain
| | - Robyn J Hylind
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA
| | - Thomas M Roston
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA; Clinician Investigator Program, The University of British Columbia, Vancouver, Canada
| | - Vassilios J Bezzerides
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA.
| | - Dominic J Abrams
- Center for Cardiovascular Genetics, Boston Children's Hospital, Harvard Medical School, Boston MA, USA.
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Lahooti H, Champion B, Wall JR. Relationship between smoking and serum levels of eye muscle and orbital connective tissue antibodies in patients with Graves ophthalmopathy. Endocrine 2023:10.1007/s12020-023-03335-5. [PMID: 36905575 DOI: 10.1007/s12020-023-03335-5] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 02/19/2023] [Indexed: 03/12/2023]
Abstract
Over the past three decades, several studies have quantified the risk of smoking in the development of ophthalmopathy in patients with Graves' hyperthyroidism, with an overall odds ratio of approximately 3.0. Smokers also have a greater risk of more advanced ophthalmopathy than non-smokers. We studied 30 patients with Graves' ophthalmopathy (GO) and 10 patients with upper eyelid signs as the only manifestation of ophthalmopathy, whose eye signs were assessed using the clinical activity score (CAS), NOSPECS classes and upper eyelid retraction (UER) score, half of whom were smokers and half of whom were non-smokers. Serum levels of eye muscle (CSQ, Fp2, G2s) and orbital connective tissue type XIII collagen (Coll XIII) antibodies are valuable markers of ophthalmopathy in patients with Graves' disease. Still, their relationship to smoking has not been investigated. These antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in all patients as a component of their clinical management. Mean serum antibody levels of all four antibodies were significantly greater in smokers than in non-smokers in patients with ophthalmopathy but not in those with upper eyelid signs only. As determined using one-way ANOVA and Spearman's correlation test, there was a significant correlation between smoking severity, assessed as pack-years, with mean Coll XIII antibody level, but not with levels of the 3 eye muscle antibodies. These results suggest that in patients with Graves' hyperthyroidism who smoke, the orbital inflammatory reactions are more advanced than in those with Graves' hyperthyroidism who do not smoke. The mechanism of this enhanced Autoimmunity against orbital antigens in smokers is unclear and worthy of further study.
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Affiliation(s)
- Hooshang Lahooti
- Department of Medicine, The University of Sydney, Nepean Clinical School, Sydney, NSW, Australia.
| | - Bernard Champion
- Department of Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Jack R Wall
- Department of Medicine, The University of Sydney, Nepean Clinical School, Sydney, NSW, Australia
- Department of Health Sciences, Macquarie University, Sydney, NSW, Australia
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Furlan S, Paradiso B, Greotti E, Volpe P, Nori A. Calsequestrin in Purkinje cells of mammalian cerebellum. Acta Histochem 2023; 125:152001. [PMID: 36669254 DOI: 10.1016/j.acthis.2023.152001] [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: 06/01/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023]
Abstract
Cerebellum is devoted to motor coordination and cognitive functions. Endoplasmic reticulum is the largest intracellular calcium store involved in all neuronal functions. Intralumenal calcium binding proteins play a pivotal role in calcium storage and contribute to both calcium release and uptake. Calsequestrin, a key calcium binding protein of sarco-endoplasmic reticulum in skeletal and cardiac muscles, was identified in chicken and fish cerebellum Purkinje cells, but its expression in mammals and human counterpart has not been studied in depth. Aim of the present paper was to investigate expression and localization of Calsequestrin in mammalian cerebellum. Calsequestrin was found to be expressed at low level in cerebellum, but specifically concentrated in Calbindin D28- and zebrin- immunopositive-Purkinje cells. Two additional fundamental calcium store markers, sarco-endoplasmic calcium pump isoform 2, SERCA2, and Inositol-trisphosphate receptor isoform 1, IP3R1, were found to be co-expressed in the region, with some localization peculiarities. In conclusion, a new marker was identified for Purkinje cells in adult mammals, including humans. Such a marker might help in staminal neuronal cells specification and in dissection of still unknown neurodegeneration and physio-pathological effects of dysregulated calcium homeostasis.
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Affiliation(s)
- Sandra Furlan
- National Research Council, Institute of Neuroscience, 35121 Padova, Italy
| | - Beatrice Paradiso
- General Pathology Unit, Dolo Hospital, Riviera XXIX Aprile, 2, 30031 Dolo, Venice, Italy
| | - Elisa Greotti
- National Research Council, Institute of Neuroscience, 35121 Padova, Italy; University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy; Padova Neuroscience Center (PNC), University of Padova, Padua, Italy
| | - Pompeo Volpe
- University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy
| | - Alessandra Nori
- University of Padova, Department of Biomedical Sciences and Interdepartmental Research Center of Myology (cirMYO), 35131 Padova, Italy.
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Neumann J, Bödicker K, Buchwalow IB, Schmidbaur C, Ramos G, Frantz S, Hofmann U, Gergs U. Effects of acute ischemia and hypoxia in young and adult calsequestrin (CSQ2) knock-out and wild-type mice. Mol Cell Biochem 2022; 477:1789-1801. [PMID: 35312907 PMCID: PMC9068673 DOI: 10.1007/s11010-022-04407-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 03/03/2022] [Indexed: 11/26/2022]
Abstract
Calsequestrin (CSQ2) is the main Ca2+-binding protein in the sarcoplasmic reticulum of the mammalian heart. In order to understand the function of calsequestrin better, we compared two age groups (young: 4-5 months of age versus adult: 18 months of age) of CSQ2 knock-out mice (CSQ2(-/-)) and littermate wild-type mice (CSQ2(+/+)). Using echocardiography, in adult mice, the basal left ventricular ejection fraction and the spontaneous beating rate were lower in CSQ2(-/-) compared to CSQ2(+/+). The increase in ejection fraction by β-adrenergic stimulation (intraperitoneal injection of isoproterenol) was lower in adult CSQ2(-/-) versus adult CSQ2(+/+). After hypoxia in vitro (isolated atrial preparations) by gassing the organ bath buffer with 95% N2, force of contraction in electrically driven left atria increased to lower values in young CSQ2(-/-) than in young CSQ2(+/+). In addition, after global ischemia and reperfusion (buffer-perfused hearts according to Langendorff; 20-min ischemia and 15-min reperfusion), the rate of tension development was higher in young CSQ2(-/-) compared to young CSQ2(+/+). Finally, we evaluated signs of inflammation (immune cells, autoantibodies, and fibrosis). However, whereas no immunological alterations were found between all investigated groups, pronounced fibrosis was found in the ventricles of adult CSQ2(-/-) compared to all other groups. We suggest that in young mice, CSQ2 is important for cardiac performance especially in isolated cardiac preparations under conditions of impaired oxygen supply, but with differences between atrium and ventricle. Lack of CSQ2 leads age dependently to fibrosis and depressed cardiac performance in echocardiographic studies.
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Affiliation(s)
- Joachim Neumann
- Institute for Pharmacology and Toxicology, Medical Faculty, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
- Institut für Pharmakologie und Toxikologie, Martin-Luther-Universität Halle-Wittenberg, Medizinische Fakultät, Magdeburger Str. 4, 06112 Halle, Germany
| | - Konrad Bödicker
- Institute for Pharmacology and Toxicology, Medical Faculty, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
| | | | - Constanze Schmidbaur
- Institute for Pharmacology and Toxicology, Medical Faculty, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
| | - Gustavo Ramos
- Department of Internal Medicine and Comprehensive Heart Failure Center, University Hospital Würzburg, 97080 Würzburg, Germany
| | - Stefan Frantz
- Department of Internal Medicine and Comprehensive Heart Failure Center, University Hospital Würzburg, 97080 Würzburg, Germany
| | - Ulrich Hofmann
- Department of Internal Medicine and Comprehensive Heart Failure Center, University Hospital Würzburg, 97080 Würzburg, Germany
| | - Ulrich Gergs
- Institute for Pharmacology and Toxicology, Medical Faculty, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
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Solarewicz J, Manly A, Kokoszka S, Sleiman N, Leff T, Cala S. Adiponectin secretion from cardiomyocytes produces canonical multimers and partial co-localization with calsequestrin in junctional SR. Mol Cell Biochem 2019; 457:201-214. [PMID: 30919218 DOI: 10.1007/s11010-019-03524-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/15/2019] [Indexed: 01/21/2023]
Abstract
Adiponectin (ADN) is an abundant protein in serum, secreted by adipocytes, that acts as a signal for fat metabolism. It is marked by a complex molecular structure that results from processes within the secretory pathway, producing a canonical set of multimers. ADN may also be secreted from cardiomyocytes, where a unique sarcomeric endoplasmic/sarcoplasmic reticulum (ER/SR) substructure has been characterized primarily for its Ca handling. We expressed ADN in cultured primary adult cardiomyocytes and nonmuscle (COS) cells. After 48 h of ADN expression by adenovirus treatment, roughly half of synthesized ADN was secreted from cardiomyocytes, and half was still in-transit within inner membrane compartments, similar to COS cells. Cardiomyocytes and COS cells both produced ADN in the three canonical forms: trimers, hexamers, and 18-mers. Higher rates of secretion occurred for higher-molecular weight multimers, especially 18-mers. The highest levels of ADN protein, whether in transit or secreted, were present as trimers and hexamers. In nonmuscle cell lines, ADN trafficked through ER and Golgi compartments as expected. In contrast, ADN in primary adult cardiomyocytes populated ER/SR tubules along the edges of sarcomeres that emanated from nuclear surfaces. Prominent co-localization of ADN occurred with calsequestrin, a marker of junctional SR, the Ca2+-release compartment of the cell. The early steps in ADN trafficking re-trace those recently described for newly made junctional SR proteins, involving a nuclear envelope (NE) translocation into SR tubules that are oriented along sarcolemmal transverse (T)-tubules (NEST pathway).
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Affiliation(s)
- Joanna Solarewicz
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Amanda Manly
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Stephanie Kokoszka
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Naama Sleiman
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA
| | - Todd Leff
- Department of Pathology, Wayne State University, Detroit, MI, 48201, USA
| | - Steven Cala
- Department of Physiology, Wayne State University, Detroit, MI, 48201, USA.
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8
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Valle G, Vergani B, Sacchetto R, Reggiani C, De Rosa E, Maccatrozzo L, Nori A, Villa A, Volpe P. Characterization of fast-twitch and slow-twitch skeletal muscles of calsequestrin 2 (CASQ2)-knock out mice: unexpected adaptive changes of fast-twitch muscles only. J Muscle Res Cell Motil 2017; 37:225-233. [PMID: 28130614 DOI: 10.1007/s10974-016-9463-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [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: 06/27/2016] [Accepted: 12/22/2016] [Indexed: 01/02/2023]
Abstract
This study investigates the functional role of calsequestrin 2 (CASQ2) in both fast-twitch and slow-twitch skeletal muscles by using CASQ2-/- mice; CASQ2 is expressed throughout life in slow-twitch muscles, but only in the developmental and neonatal stages in fast-twitch muscles. CASQ2-/- causes increase in calsequestrin 1 (CASQ1) expression, but without functional changes in both muscle types. CASQ2-/- mice have ultrastructural changes in fast-twitch muscles only, i.e., formation of pentads and stacks in the sarcoplasmic reticulum.
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Affiliation(s)
- Giorgia Valle
- Dipartimento di Scienze Biomediche dell'Università di Padova, Istituto Interuniversitario di Miologia, Viale G. Colombo 3, 35121, Padova, Italy
| | - Barbara Vergani
- Consorzio MIA (Microscopy Image Analysis), Università di Milano-Bicocca, 20052, Monza, Italy
| | - Roberta Sacchetto
- Dipartimento di Biomedicina Comparata ed Alimentazione dell'Università di Padova, Padova, Italy
| | - Carlo Reggiani
- Dipartimento di Scienze Biomediche dell'Università di Padova, Istituto Interuniversitario di Miologia, Viale G. Colombo 3, 35121, Padova, Italy
| | - Edith De Rosa
- Dipartimento di Scienze Biomediche dell'Università di Padova, Istituto Interuniversitario di Miologia, Viale G. Colombo 3, 35121, Padova, Italy
| | - Lisa Maccatrozzo
- Dipartimento di Biomedicina Comparata ed Alimentazione dell'Università di Padova, Padova, Italy
| | - Alessandra Nori
- Dipartimento di Scienze Biomediche dell'Università di Padova, Istituto Interuniversitario di Miologia, Viale G. Colombo 3, 35121, Padova, Italy
| | - Antonello Villa
- Consorzio MIA (Microscopy Image Analysis), Università di Milano-Bicocca, 20052, Monza, Italy
| | - Pompeo Volpe
- Dipartimento di Scienze Biomediche dell'Università di Padova, Istituto Interuniversitario di Miologia, Viale G. Colombo 3, 35121, Padova, Italy.
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Handhle A, Ormonde CE, Thomas NL, Bralesford C, Williams AJ, Lai FA, Zissimopoulos S. Calsequestrin interacts directly with the cardiac ryanodine receptor luminal domain. J Cell Sci 2016; 129:3983-3988. [PMID: 27609834 PMCID: PMC5117208 DOI: 10.1242/jcs.191643] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [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: 05/03/2016] [Accepted: 09/05/2016] [Indexed: 11/20/2022] Open
Abstract
Cardiac muscle contraction requires sarcoplasmic reticulum (SR) Ca2+ release mediated by the quaternary complex comprising the ryanodine receptor 2 (RyR2), calsequestrin 2 (CSQ2), junctin (encoded by ASPH) and triadin. Here, we demonstrate that a direct interaction exists between RyR2 and CSQ2. Topologically, CSQ2 binding occurs at the first luminal loop of RyR2. Co-expression of RyR2 and CSQ2 in a human cell line devoid of the other quaternary complex proteins results in altered Ca2+-release dynamics compared to cells expressing RyR2 only. These findings provide a new perspective for understanding the SR luminal Ca2+ sensor and its involvement in cardiac physiology and disease.
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Affiliation(s)
- Ahmed Handhle
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,Medical Biochemistry Department, Faculty of Medicine, Mansoura University, Mansoura 35516, Egypt
| | - Chloe E Ormonde
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - N Lowri Thomas
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Catherine Bralesford
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Alan J Williams
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - F Anthony Lai
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Spyros Zissimopoulos
- Sir Geraint Evans Wales Heart Research Institute, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
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10
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Guizoni DM, Oliveira-Junior SA, Noor SLR, Pagan LU, Martinez PF, Lima ARR, Gomes MJ, Damatto RL, Cezar MDM, Bonomo C, Zornoff LAM, Okoshi K, Okoshi MP. Effects of late exercise on cardiac remodeling and myocardial calcium handling proteins in rats with moderate and large size myocardial infarction. Int J Cardiol 2016; 221:406-12. [PMID: 27404715 DOI: 10.1016/j.ijcard.2016.07.072] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/04/2016] [Indexed: 01/10/2023]
Abstract
BACKGROUND Physical exercise attenuates myocardial infarction (MI)-induced cardiac remodeling. However, it is unsettled whether late exercise modulates post-infarction cardiac remodeling differentially according to infarct size. We investigated the effects of exercise started at late stage heart failure on cardiac remodeling in rats with moderate and large sized MI. METHODS Three months after MI, rats were assigned into sedentary and exercise groups. Exercise rats underwent treadmill for three months. After assessing infarct size by histological analysis, rats were subdivided into four groups: moderate MI sedentary (Mod MI-Sed; n=7), Mod MI exercised (Mod MI-Ex; n=7), Large MI-Sed (n=11), and Large MI-Ex (n=10). RESULTS Before exercise, MI-induced cardiac changes were demonstrated by comparing results to a Sham group; alterations were more intense in rats with large than moderate MI size. Systolic function, evaluated by echocardiogram using the variation in LV fractional area change between after and before exercise, was improved in exercise than sedentary groups. Calsequestrin expression increased in exercised compared to sedentary groups. L-type calcium channel was higher in Mod MI-Ex than Mod MI-Sed. SERCA2a, phospholamban, and Na(+)/Ca(2+) exchanger expression did not differ between groups. CONCLUSION Late exercise improves systolic function and modulates intracellular calcium signaling proteins in rats with moderate and large MI.
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Affiliation(s)
- Daniele M Guizoni
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | | | - Sefora L R Noor
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Luana U Pagan
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Paula F Martinez
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil; School of Physical Therapy, Federal University of Mato Grosso do Sul, Campo Grande, Brazil
| | - Aline R R Lima
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Mariana J Gomes
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Ricardo L Damatto
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Marcelo D M Cezar
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Camila Bonomo
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Leonardo A M Zornoff
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Katashi Okoshi
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil
| | - Marina P Okoshi
- Internal Medicine Department, Botucatu Medical School, Sao Paulo State University, UNESP, Botucatu, Brazil.
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Zungu-Edmondson M, Shults NV, Wong CM, Suzuki YJ. Modulators of right ventricular apoptosis and contractility in a rat model of pulmonary hypertension. Cardiovasc Res 2016; 110:30-9. [PMID: 26790474 DOI: 10.1093/cvr/cvw014] [Citation(s) in RCA: 31] [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: 10/08/2015] [Accepted: 12/30/2015] [Indexed: 11/12/2022] Open
Abstract
AIMS Right ventricular (RV) failure is the major cause of death among patients with pulmonary arterial hypertension (PAH). However, the mechanism of RV failure has not been defined. METHODS AND RESULTS This study examined mechanisms and consequences of RV myocyte apoptosis and fibrosis in response to PAH. Rats were injected with SU5416 (vascular endothelial growth factor inhibitor), followed by hypoxia for 3 weeks, and subsequently maintained in normoxia for 2, 5, or 14 weeks (5-, 8-, and 17-week time points after the SU5416 injection, respectively). RV systolic pressure (RVSP) was elevated to >70 mmHg at 5-week time point, and this pressure was sustained thereafter. Significant RV myocyte apoptosis and fibrosis were observed at 8- and 17-week time points. Apoptosis was associated with downregulated Bcl-xL (anti-apoptotic protein), downregulated GATA4 (transcriptional regulator of Bcl-xL), and upregulated p53 (negative regulator of GATA4 gene transcription). PAH-mediated RV apoptosis and fibrosis were attenuated in p53 knock-out rats. Despite the major loss of cardiomyocytes, RV contractility was enhanced, suggesting that the remaining myocytes can perform improved contractile functions. Improved RV contractility is associated with the increased expression of contractile and sarcoplasmic reticulum Ca(2+) uptake proteins. In contrast, the expression of calsequestrin 2 (CSQ2) was downregulated. The siRNA knockdown of CSQ2 improved RV contractility and increased the expression of contractile and Ca(2+) uptake proteins. CONCLUSION These results suggest that RV decompensation is associated with the death of cardiomyocytes, resulting in fibrosis. However, the remaining myocytes are capable of sustaining RV contractility through the mechanism that involves CSQ2.
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Affiliation(s)
- Makhosazane Zungu-Edmondson
- Department of Pharmacology and Physiology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington DC 20057, USA
| | - Nataliia V Shults
- Department of Pharmacology and Physiology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington DC 20057, USA
| | - Chi-Ming Wong
- Department of Pharmacology and Physiology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington DC 20057, USA
| | - Yuichiro J Suzuki
- Department of Pharmacology and Physiology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington DC 20057, USA
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Kryshtal DO, Gryshchenko O, Gomez-Hurtado N, Knollmann BC. Impaired calcium-calmodulin-dependent inactivation of Cav1.2 contributes to loss of sarcoplasmic reticulum calcium release refractoriness in mice lacking calsequestrin 2. J Mol Cell Cardiol 2015; 82:75-83. [PMID: 25758429 DOI: 10.1016/j.yjmcc.2015.02.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/26/2015] [Accepted: 02/27/2015] [Indexed: 11/20/2022]
Abstract
AIMS In cardiac muscle, Ca(2+) release from sarcoplasmic reticulum (SR) is reduced with successively shorter coupling intervals of premature stimuli, a phenomenon known as SR Ca(2+) release refractoriness. We recently reported that the SR luminal Ca(2+) binding protein calsequestrin 2 (Casq2) contributes to release refractoriness in intact mouse hearts, but the underlying mechanisms remain unclear. Here, we further investigate the mechanisms responsible for physiological release refractoriness. METHODS AND RESULTS Gene-targeted ablation of Casq2 (Casq2 KO) abolished SR Ca(2+) release refractoriness in isolated mouse ventricular myocytes. Surprisingly, impaired Ca(2+)-dependent inactivation of L-type Ca(2+) current (ICa), which is responsible for triggering SR Ca(2+) release, significantly contributed to loss of Ca(2+) release refractoriness in Casq2 KO myocytes. Recovery from Ca(2+)-dependent inactivation of ICa was significantly accelerated in Casq2 KO compared to wild-type (WT) myocytes. In contrast, voltage-dependent inactivation measured by using Ba(2+) as charge carrier was not significantly different between WT and Casq2 KO myocytes. Ca(2+)-dependent inactivation of ICa was normalized by intracellular dialysis of excess apo-CaM (20 μM), which also partially restored physiological Ca(2+) release refractoriness in Casq2 KO myocytes. CONCLUSIONS Our findings reveal that the intra-SR protein Casq2 is largely responsible for the phenomenon of SR Ca(2+) release refractoriness in murine ventricular myocytes. We also report a novel mechanism of impaired Ca(2+)-CaM-dependent inactivation of Cav1.2, which contributes to the loss of SR Ca(2+) release refractoriness in the Casq2 KO mouse model and, therefore, may further increase risk for ventricular arrhythmia in vivo.
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13
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Beard NA, Dulhunty AF. C-terminal residues of skeletal muscle calsequestrin are essential for calcium binding and for skeletal ryanodine receptor inhibition. Skelet Muscle 2015; 5:6. [PMID: 25861445 PMCID: PMC4389316 DOI: 10.1186/s13395-015-0029-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [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: 10/31/2014] [Accepted: 01/14/2015] [Indexed: 02/05/2023] Open
Abstract
Background Skeletal muscle function depends on calcium signaling proteins in the sarcoplasmic reticulum (SR), including the calcium-binding protein calsequestrin (CSQ), the ryanodine receptor (RyR) calcium release channel, and skeletal triadin 95 kDa (trisk95) and junctin, proteins that bind to calsequestrin type 1 (CSQ1) and ryanodine receptor type 1 (RyR1). CSQ1 inhibits RyR1 and communicates store calcium load to RyR1 channels via trisk95 and/or junctin. Methods In this manuscript, we test predictions that CSQ1’s acidic C-terminus contains binding sites for trisk95 and junctin, the major calcium binding domain, and that it determines CSQ1’s ability to regulate RyR1 activity. Results Progressive alanine substitution of C-terminal acidic residues of CSQ1 caused a parallel reduction in the calcium binding capacity but did not significantly alter CSQ1’s association with trisk95/junctin or influence its inhibition of RyR1 activity. Deletion of the final seven residues in the C-terminus significantly hampered calcium binding, significantly reduced CSQ’s association with trisk95/junctin and decreased its inhibition of RyR1. Deletion of the full C-terminus further reduced calcium binding to CSQ1 altered its association with trisk95 and junctin and abolished its inhibition of RyR1. Conclusions The correlation between the number of residues mutated/deleted and binding of calcium, trisk95, and junctin suggests that binding of each depends on diffuse ionic interactions with several C-terminal residues and that these interactions may be required for CSQ1 to maintain normal muscle function.
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Affiliation(s)
- Nicole A Beard
- John Curtin School of Medical Research, Australian National University, Garran Road, Canberra, ACT 2601 Australia ; Discipline of Biomedical Sciences, Centre for Research in Therapeutic Solutions, Faculty of Education Science, Technology and Maths, University of Canberra, Kirinari Street, Bruce, ACT 2601 Australia
| | - Angela F Dulhunty
- John Curtin School of Medical Research, Australian National University, Garran Road, Canberra, ACT 2601 Australia
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Kurtzwald-Josefson E, Hochhauser E, Bogachenko K, Harun-Khun S, Katz G, Aravot D, Seidman JG, Seidman CE, Eldar M, Shainberg A, Arad M. Alpha blockade potentiates CPVT therapy in calsequestrin-mutant mice. Heart Rhythm 2014; 11:1471-9. [PMID: 24768611 DOI: 10.1016/j.hrthm.2014.04.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Indexed: 11/21/2022]
Abstract
BACKGROUND Spontaneous calcium release evoking delayed afterdepolarization is believed to cause catecholaminergic polymorphic ventricular tachycardia (CPVT), a lethal human arrhythmia provoked by exercise or emotional stress. β-Adrenergic blockers are the drug of choice, but fail to achieve complete arrhythmia control in some patients. These individuals often require flecainide, device implantation, and/or sympathetic denervation. OBJECTIVE To optimize the arrhythmia therapy by pharmacological inhibition of the sympathetic nervous system in the homozygous calsequestrin knockout (CASQ2(Δ/Δ)) mouse model of CPVT2. METHODS A heart telemetry device was implanted for continuous electrocardiographic recording at rest and during provocation testing. Calcium transients and abnormal calcium release were studied in cardiomyocytes isolated from adult mice. Adrenergic receptor expression was determined by using Western blotting and confocal microscopy. RESULTS Adult CASQ2(Δ/Δ) mice suffer from complex ventricular arrhythmia at rest and ventricular tachycardia during treadmill exercise and after epinephrine injection. β-Adrenergic blockers, propranolol and metoprolol, attenuated arrhythmia at rest but not after stress. Reserpine had no efficacy in controlling arrhythmia. Agents with α-blocking activity, phentolamine or labetalol, abolished both exercise- and epinephrine-induced arrhythmia. In contrast, injection of α-adrenergic agonist phenylephrine reproducibly provoked ventricular tachycardia. Isolated cardiomyocytes from CASQ2(Δ/Δ) mice had delayed calcium release waves upon exposure to sympathetic agonists, which were abolished by phentolamine. Hearts of calsequestrin-mutant mice expressed more α1-adrenergic receptor than did wild type control mice (P < .05). CONCLUSION We identified a contribution of the α-adrenergic pathway to the pathogenesis of catecholamine-induced arrhythmia. α-Blockade emerges as an effective therapy in the murine model of CPVT2 and should be tried in humans resistant to β-blockers.
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Sanchez EJ, Hayes RP, Barr JT, Lewis KM, Webb BN, Subramanian AK, Nissen MS, Jones JP, Shelden EA, Sorg BA, Fill M, Schenk JO, Kang C. Potential role of cardiac calsequestrin in the lethal arrhythmic effects of cocaine. Drug Alcohol Depend 2013; 133:344-51. [PMID: 23876860 DOI: 10.1016/j.drugalcdep.2013.06.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 06/11/2013] [Accepted: 06/14/2013] [Indexed: 11/24/2022]
Abstract
BACKGROUND Cocaine-related deaths are continuously rising and its overdose is often associated with lethal cardiotoxic effects. METHODS AND RESULTS Our approach, employing isothermal titration calorimetry (ITC) and light scattering in parallel, has confirmed the significant affinity of human cardiac calsequestrin (CASQ2) for cocaine. Calsequestrin (CASQ) is a major Ca(2+)-storage protein within the sarcoplasmic reticulum (SR) of both cardiac and skeletal muscles. CASQ acts as a Ca(2+) buffer and Ca(2+)-channel regulator through its unique Ca(2+)-dependent oligomerization. Equilibrium dialysis and atomic absorption spectroscopy experiments illustrated the perturbational effect of cocaine on CASQ2 polymerization, resulting in substantial reduction of its Ca(2+)-binding capacity. We also confirmed the accumulation of cocaine in rat heart tissue and the substantial effects cocaine has on cultured C2C12 cells. The same experiments were performed with methamphetamine as a control, which displayed neither affinity for CASQ2 nor any significant effects on its function. Since cocaine did not have any direct effect on the Ca(2+)-release channel judging from our single channel recordings, these studies provide new insights into how cocaine may interfere with the normal E-C coupling mechanism with lethal arrhythmogenic consequences. CONCLUSION We propose that cocaine accumulates in SR through its affinity for CASQ2 and affects both SR Ca(2+) storage and release by altering the normal CASQ2 Ca(2+)-dependent polymerization. By this mechanism, cocaine use could produce serious cardiac problems, especially in people who have genetically-impaired CASQ2, defects in other E-C coupling components, or compromised cocaine metabolism and clearance.
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Katz G, Shainberg A, Hochhauser E, Kurtzwald-Josefson E, Issac A, El-Ani D, Aravot D, Afek A, Seidman JG, Seidman CE, Eldar M, Arad M. The role of mutant protein level in autosomal recessive catecholamine dependent polymorphic ventricular tachycardia (CPVT2). Biochem Pharmacol 2013; 86:1576-83. [PMID: 24070655 DOI: 10.1016/j.bcp.2013.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Revised: 09/12/2013] [Accepted: 09/12/2013] [Indexed: 01/05/2023]
Abstract
Humans and genetically engineered mice with recessively inherited CPVT develop arrhythmia which may arise due to malfunction or degradation of calsequestrin (CASQ2). We investigated the relation between protein level and arrhythmia severity in CASQ2(D307H/D307H) (D307H), compared to CASQ2(Δ/Δ) (KO) and wild type (WT) mice. CASQ2 expression and Ca²⁺ transients were recorded in cardiomyocytes from neonatal or adult mice. Arrhythmia was studied in vivo using heart rhythm telemetry at rest, exercise and after epinephrine injection. CASQ2 protein was absent in KO heart. Neonatal D307H and WT hearts expressed significantly less CASQ2 protein than the level found in the adult WT. Adult D307H expressed only 20% of CASQ2 protein found in WT. Spontaneous Ca²⁺ release was more prevalent in neonatal KO cardiomyocytes (89%) compared to 33-36% of either WT or D307H, respectively, p<0.001. Adult cardiomyocytes from both mutant mice had more Ca²⁺ abnormalities compared to control (KO: 82%, D307H 63%, WT 12%, p<0.01). Calcium oscillations were most common in KO cardiomyocytes. We then treated mice with bortezomib to inhibit CASQ2(D307H) degradation. Bortezomib increased CASQ2 expression in D307H hearts by ∼50% (p<0.05). Bortezomib-treated D307H mice had lower CPVT prevalence and less premature ventricular beats during peak exercise. No benefit against arrhythmia was observed in bortezomib treated KO mice. These results indicate that the mutant CASQ2(D307H) protein retains some of its physiological function. Its expression decreases with age and is inversely related to arrhythmia severity. Preventing the degradation of mutant protein should be explored as a possible therapeutic strategy in appropriate CPVT2 patients.
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Affiliation(s)
- Guy Katz
- Leviev Heart Center, Sheba Medical Center, Tel Hashomer and Sackler School of, Medicine, Tel Aviv University, Tel Aviv, Israel
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Abstract
TNNI3K is a cardiac-specific and cardiac troponin I (cTnI)-interacting MAP kinase, known to play important roles in promoting cardiac differentiation, maintenance of beating rhythm and contractual force. The molecular structure of TNNI3K contains three kinds of domain: a seven or ten NH2-terminal ankyrin repeat domain followed by a protein kinase domain and a COOH-terminal serine-rich domain. There are many binding sites in the structure of TNNI3K for binding to ATP, magnesium, nucleotide, protein kinase C, antioxidant protein 1 (AOP-1) and cTnI, indicating TNNI3K has many interacting partners. This review summarizes the evidence, hypothesis and significance of TNNI3K interacting with TNNI3 and its other putative interaction partners. From the literature, the interaction partners of TNNI3K are divided into 2 types following their phenotypic pattern of functions, positive interaction (to increase the cardiac performance) or negative interaction (to suppress the cardiac performance). Following their binding sites, it also can be divided into other 2 types: binding to C-terminal domain (e.g., cTnI) or binding to both ankyrin repeat domain and C-terminal domains (AOP-1). To date, a well understood partner of TNNI3K is cTnI, from the molecular structure, physiological function, mechanisms and its significance in some physiological and pathophysiological conditions. There are many reasons to believe that, with more understanding on the TNNI3K interacting with its partners, we can understand more roles of TNNI3K in some cardiac diseases.
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Fischer H, Fischer J, Boknik P, Gergs U, Schmitz W, Domschke W, Konturek JW, Neumann J. Reduced expression of Ca 2+-regulating proteins in the upper gastrointestinal tract of patients with achalasia. World J Gastroenterol 2006; 12:6002-7. [PMID: 17009399 PMCID: PMC4124408 DOI: 10.3748/wjg.v12.i37.6002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To compare expression of Ca2+-regulating proteins in upper gastrointestinal (GI) tract of achalasia patients and healthy volunteers and to elucidate their role in achalasia.
METHODS: Sarcoplasmic reticulum Ca2+ ATPase (SERCA) isoforms 2a and 2b, phospholamban (PLB), calsequestrin (CSQ), and calreticulin (CRT) were assessed by quantitative Western blotting in esophagus and heart of rats, rabbits, and humans. Furthermore, expression profiles of these proteins in biopsies of lower esophageal sphincter and esophagus from patients with achalasia and healthy volunteers were analyzed.
RESULTS: SERCA 2a protein expression was much higher in human heart (cardiac ventricle) compared to esophagus. However, SERCA 2b was expressed predominantly in the esophagus. The highest CRT expression was noted in the human esophagus, while PLB, although highly expressed in the heart, was below our detection limit in upper GI tissue. Compared to healthy controls, CSQ and CRT expression in lower esophageal sphincter and distal esophageal body were significantly reduced in patients with achalasia (P < 0.05).
CONCLUSION: PLB in the human esophagus might be of lesser importance for regulation of SERCA than in heart. Lower expression of Ca2+ storage proteins (CSQ and CRT) might contribute to increased lower esophageal sphincter pressure in achalasia, possibly by increasing free intracellular Ca2+.
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Affiliation(s)
- Harald Fischer
- Medizinische Klinik und Poliklinik B, Universitätsklinikum Münster, Germany
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