1
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Nielsen MS, van Opbergen CJM, van Veen TAB, Delmar M. The intercalated disc: a unique organelle for electromechanical synchrony in cardiomyocytes. Physiol Rev 2023; 103:2271-2319. [PMID: 36731030 PMCID: PMC10191137 DOI: 10.1152/physrev.00021.2022] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 01/24/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
The intercalated disc (ID) is a highly specialized structure that connects cardiomyocytes via mechanical and electrical junctions. Although described in some detail by light microscopy in the 19th century, it was in 1966 that electron microscopy images showed that the ID represented apposing cell borders and provided detailed insight into the complex ID nanostructure. Since then, much has been learned about the ID and its molecular composition, and it has become evident that a large number of proteins, not all of them involved in direct cell-to-cell coupling via mechanical or gap junctions, reside at the ID. Furthermore, an increasing number of functional interactions between ID components are emerging, leading to the concept that the ID is not the sum of isolated molecular silos but an interacting molecular complex, an "organelle" where components work in concert to bring about electrical and mechanical synchrony. The aim of the present review is to give a short historical account of the ID's discovery and an updated overview of its composition and organization, followed by a discussion of the physiological implications of the ID architecture and the local intermolecular interactions. The latter will focus on both the importance of normal conduction of cardiac action potentials as well as the impact on the pathophysiology of arrhythmias.
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Affiliation(s)
- Morten S Nielsen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Chantal J M van Opbergen
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
| | - Toon A B van Veen
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Mario Delmar
- The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, New York, United States
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2
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Sykora M, Andelova K, Szeiffova Bacova B, Egan Benova T, Martiskova A, Knezl V, Tribulova N. Hypertension Induces Pro-arrhythmic Cardiac Connexome Disorders: Protective Effects of Treatment. Biomolecules 2023; 13:biom13020330. [PMID: 36830700 PMCID: PMC9953310 DOI: 10.3390/biom13020330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/16/2023] [Accepted: 01/21/2023] [Indexed: 02/11/2023] Open
Abstract
Prolonged population aging and unhealthy lifestyles contribute to the progressive prevalence of arterial hypertension. This is accompanied by low-grade inflammation and over time results in heart dysfunction and failure. Hypertension-induced myocardial structural and ion channel remodeling facilitates the development of both atrial and ventricular fibrillation, and these increase the risk of stroke and sudden death. Herein, we elucidate hypertension-induced impairment of "connexome" cardiomyocyte junctions. This complex ensures cell-to-cell adhesion and coupling for electrical and molecular signal propagation. Connexome dysfunction can be a key factor in promoting the occurrence of both cardiac arrhythmias and heart failure. However, the available literature indicates that arterial hypertension treatment can hamper myocardial structural remodeling, hypertrophy and/or fibrosis, and preserve connexome function. This suggests the pleiotropic effects of antihypertensive agents, including anti-inflammatory. Therefore, further research is required to identify specific molecular targets and pathways that will protect connexomes, and it is also necessary to develop new approaches to maintain heart function in patients suffering from primary or pulmonary arterial hypertension.
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3
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Weng A, Rabin EE, Flozak AS, Chiarella SE, Aillon RP, Gottardi CJ. Alpha-T-catenin is expressed in peripheral nerves as a constituent of Schwann cell adherens junctions. Biol Open 2022; 11:bio059634. [PMID: 36420826 PMCID: PMC9793867 DOI: 10.1242/bio.059634] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 11/16/2022] [Indexed: 11/26/2022] Open
Abstract
The adherens junction component, alpha-T-catenin (αTcat) is an established contributor to cardiomyocyte junction structure and function, but recent genomic studies link CTNNA3 polymorphisms to diseases with no clear cardiac underpinning, including asthma, autism and multiple sclerosis, suggesting causal contributions from a different cell-type. We show Ctnna3 mRNA is highly expressed in peripheral nerves (e.g. vagus and sciatic), where αTcat protein enriches at paranodes and myelin incisure adherens junctions of Schwann cells. We validate αTcat immunodetection specificity using a new Ctnna3-knock-out fluorescence reporter mouse line yet find no obvious Schwann cell loss-of-function morphology at the light microscopic level. CTNNA3/Ctnna3 mRNA is also abundantly detected in oligodendrocytes of the central nervous system via public databases, supporting a general role for αTcat in these unique cell-cell junctions. These data suggest that the wide range of diseases linked to CTNNA3 may be through its role in maintaining neuroglial functions of central and peripheral nervous systems. This article has a corresponding First Person interview with the co-first authors of the paper.
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Affiliation(s)
- Anthea Weng
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Erik E. Rabin
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Annette S. Flozak
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Sergio E. Chiarella
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Mayo Clinic, Rochester, MN 55902, USA
| | - Raul Piseaux Aillon
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Cara J. Gottardi
- Department of Pulmonary Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Cell & Developmental Biology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
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4
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Yeruva S, Waschke J. Structure and regulation of desmosomes in intercalated discs: Lessons from epithelia. J Anat 2022; 242:81-90. [PMID: 35128661 PMCID: PMC9773171 DOI: 10.1111/joa.13634] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/22/2021] [Accepted: 01/10/2022] [Indexed: 12/25/2022] Open
Abstract
For electromechanical coupling of cardiomyocytes, intercalated discs (ICDs) are pivotal as highly specialized intercellular contact areas. ICD consists of adhesive contacts, such as desmosomes and adherens junctions (AJs) that are partially intermingled and thereby form an area composita to provide mechanical strength, as well as gap junctions (GJ) and sodium channels for excitation propagation. In contrast, in epithelia, mixed junctions with features of desmosomes and AJs are regarded as transitory primarily during the formation of desmosomes. The anatomy of desmosomes is defined by a typical ultrastructure with dense intracellular plaques anchoring the cadherin-type adhesion molecules to the intermediate filament cytoskeleton. Desmosomal diseases characterized by impaired adhesive and signalling functions of desmosomal contacts lead to arrhythmogenic cardiomyopathy when affecting cardiomyocytes and cause pemphigus when manifesting in keratinocytes or present as cardiocutaneous syndromes when both cell types are targeted by the disease, which underscores the high biomedical relevance of these cell contacts. Therefore, comparative analyses regarding the structure and regulation of desmosomal contacts in cardiomyocytes and epithelial cells are helpful to better understand disease pathogenesis. In this brief review, we describe the structural properties of ICD compared to epithelial desmosomes and suggest that mechanisms regulating adhesion may at least in part be comparable. Also, we discuss whether phenomena such as hyperadhesion or the bidirectional regulation of desmosomes to serve as signalling hubs in epithelial cells may also be relevant for ICD.
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Affiliation(s)
- Sunil Yeruva
- Ludwig‐Maximilian‐Universität München, Anatomische Anstalt, Lehrstuhl Anatomie I – Vegetative AnatomieMunichGermany
| | - Jens Waschke
- Ludwig‐Maximilian‐Universität München, Anatomische Anstalt, Lehrstuhl Anatomie I – Vegetative AnatomieMunichGermany
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5
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Abstract
Desmoplakin (DSP), encoded by the DSP gene, is the main desmosome component and is abundant in the myocardial tissue. There are three DSP isoforms that assume the role of supporting structural stability through intercellular adhesion. It has been found that DSP regulates the transcription of adipogenic and fibrogenic genes, and maintains appropriate electrical conductivity by regulating gap junctions and ion channels. DSP is essential for normal myocardial development and the maintenance of its structural functions. Studies have suggested that DSP gene mutations are associated with a variety of hereditary cardiomyopathy, such as arrhythmia cardiomyopathy, dilated cardiomyopathy (DCM), left ventricular noncompaction, and is also closely associated with the Carvajal syndrome, Naxos disease, and erythro-keratodermia-cardiomyopathy syndrome with skin and heart damage. The structure and function of DSP, as well as the clinical manifestations of DSP-related cardiomyopathy were reviewed in this article.
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A catenin of the plakophilin-subfamily, Pkp3, responds to canonical-Wnt pathway components and signals. Biochem Biophys Res Commun 2021; 563:31-39. [PMID: 34058472 DOI: 10.1016/j.bbrc.2021.05.043] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 05/13/2021] [Indexed: 12/21/2022]
Abstract
Vertebrate beta-catenin plays a key role as a transducer of canonical-Wnt signals. We earlier reported that, similar to beta-catenin, the cytoplasmic signaling pool of p120-catenin-isoform1 is stabilized in response to canonical-Wnt signals. To obtain a yet broader view of the Wnt-pathway's impact upon catenin proteins, we focused upon plakophilin3 (plakophilin-3; Pkp3) as a representative of the plakophilin-catenin subfamily. Promoting tissue integrity, the plakophilins assist in linking desmosomal cadherins to intermediate filaments at desmosome junctions, and in common with other catenins they perform additional functions including in the nucleus. In this report, we test whether canonical-Wnt pathway components modulate Pkp3 protein levels. We find that in common with beta-catenin and p120-catenin-isoform1, Pkp3 is stabilized in the presence of a Wnt-ligand or a dominant-active form of the LRP6 receptor. Pkp3's levels are conversely lowered upon expressing destruction-complex components such as GSK3β and Axin, and in further likeness to beta-catenin and p120-isoform1, Pkp3 associates with GSK3beta and Axin. Finally, we note that Pkp3-catenin trans-localizes into the nucleus in response to Wnt-ligand and its exogenous expression stimulates an accepted Wnt reporter. These findings fit an expanded model where context-dependent Wnt-signals or pathway components modulate Pkp3-catenin levels. Future studies will be needed to assess potential gene regulatory, cell adhesive, or cytoskeletal effects.
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Interplay between desmoglein2 and hypoxia controls metastasis in breast cancer. Proc Natl Acad Sci U S A 2021; 118:2014408118. [PMID: 33431674 DOI: 10.1073/pnas.2014408118] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Metastasis is the major cause of cancer death. An increased level of circulating tumor cells (CTCs), metastatic cancer cells that have intravasated into the circulatory system, is particularly associated with colonization of distant organs and poor prognosis. However, the key factors required for tumor cell dissemination and colonization remain elusive. We found that high expression of desmoglein2 (DSG2), a component of desmosome-mediated intercellular adhesion complexes, promoted tumor growth, increased the prevalence of CTC clusters, and facilitated distant organ colonization. The dynamic regulation of DSG2 by hypoxia was key to this process, as down-regulation of DSG2 in hypoxic regions of primary tumors led to elevated epithelial-mesenchymal transition (EMT) gene expression, allowing cells to detach from the primary tumor and undergo intravasation. Subsequent derepression of DSG2 after intravasation and release of hypoxic stress was associated with an increased ability to colonize distant organs. This dynamic regulation of DSG2 was mediated by Hypoxia-Induced Factor1α (HIF1α). In contrast to its more widely observed function to promote expression of hypoxia-inducible genes, HIF1α repressed DSG2 by recruitment of the polycomb repressive complex 2 components, EZH2 and SUZ12, to the DSG2 promoter in hypoxic cells. Consistent with our experimental data, DSG2 expression level correlated with poor prognosis and recurrence risk in breast cancer patients. Together, these results demonstrated the importance of DSG2 expression in metastasis and revealed a mechanism by which hypoxia drives metastasis.
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8
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Zhao G, Zhang HM, Qiu Y, Ye X, Yang D. Cleavage of Desmosomal Cadherins Promotes γ-Catenin Degradation and Benefits Wnt Signaling in Coxsackievirus B3-Induced Destruction of Cardiomyocytes. Front Microbiol 2020; 11:767. [PMID: 32457708 PMCID: PMC7225294 DOI: 10.3389/fmicb.2020.00767] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 03/31/2020] [Indexed: 01/01/2023] Open
Abstract
Coxsackievirus B3 (CVB3) is the primary etiologic agent of viral myocarditis, a major heart disease that occurs predominantly in children and young adolescents. In the heart, intercalated disks (ICD) are important structural formations that connect adjacent cardiomyocytes to maintain cardiac architecture and mediate signal communication. Deficiency in ICD components, such as desmosome proteins, leads to heart dysfunction. γ-catenin, a component protein of desmosomes, normally binds directly to desmocollin-2 and desmoglein-2. In this study, we found that CVB3 infection downregulated γ-catenin at the protein level but not the mRNA level in mouse HL-1 cardiomyocytes. We further found that this reduction of γ-catenin protein is a result of ubiquitin proteasome-mediated degradation, since the addition of proteasome inhibitor MG132 inhibited γ-catenin downregulation. In addition, we found that desmocollin-2 and desmoglein-2 were cleaved by both viral protease 3C and virus-activated cellular caspase, respectively. These cleavages led to the release of bound γ-catenin from the desmosome into the cytosol, resulting in rapid degradation of γ-catenin. Since γ-catenin shares high sequence homology with β-catenin in binding the TCF/LEF transcription factor, we further studied the effect of γ-catenin degradation on Wnt/β-catenin signaling. Luciferase assay showed that γ-catenin expression inhibited Wnt/β-catenin signaling. This finding was substantiated by qPCR to show that overexpression of γ-catenin downregulated transcription of Wnt signal target genes, c-myc and MMP9, while silencing γ-catenin upregulated these target genes. Finally, we demonstrated that γ-catenin expression inhibited CVB3 replication. In search for the underlying mechanism, we found that silencing γ-catenin caused down-regulation of interferon-β and its stimulated antiviral genes MDA5, MAVS, and ISG15. Taken together, our results indicate, for the first time, that CVB3 infection causes cardiomyocyte death through, at least in part, direct damage to the desmosome structure and reduction of γ-catenin protein, which in return promotes Wnt/β-catenin signaling and downregulates interferon-β stimulated immune responses.
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Affiliation(s)
- Guangze Zhao
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Huifang M Zhang
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Ye Qiu
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,College of Biology, Hunan University, Changsha, China
| | - Xin Ye
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
| | - Decheng Yang
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.,Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, BC, Canada
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9
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Angulo-Urarte A, van der Wal T, Huveneers S. Cell-cell junctions as sensors and transducers of mechanical forces. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183316. [PMID: 32360073 DOI: 10.1016/j.bbamem.2020.183316] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/02/2020] [Accepted: 04/15/2020] [Indexed: 12/16/2022]
Abstract
Epithelial and endothelial monolayers are multicellular sheets that form barriers between the 'outside' and 'inside' of tissues. Cell-cell junctions, made by adherens junctions, tight junctions and desmosomes, hold together these monolayers. They form intercellular contacts by binding their receptor counterparts on neighboring cells and anchoring these structures intracellularly to the cytoskeleton. During tissue development, maintenance and pathogenesis, monolayers encounter a range of mechanical forces from the cells themselves and from external systemic forces, such as blood pressure or tissue stiffness. The molecular landscape of cell-cell junctions is diverse, containing transmembrane proteins that form intercellular bonds and a variety of cytoplasmic proteins that remodel the junctional connection to the cytoskeleton. Many junction-associated proteins participate in mechanotransduction cascades to confer mechanical cues into cellular responses that allow monolayers to maintain their structural integrity. We will discuss force-dependent junctional molecular events and their role in cell-cell contact organization and remodeling.
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Affiliation(s)
- Ana Angulo-Urarte
- Amsterdam UMC, University of Amsterdam, Location AMC, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Tanne van der Wal
- Amsterdam UMC, University of Amsterdam, Location AMC, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
| | - Stephan Huveneers
- Amsterdam UMC, University of Amsterdam, Location AMC, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands.
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10
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Green KJ, Jaiganesh A, Broussard JA. Desmosomes: Essential contributors to an integrated intercellular junction network. F1000Res 2019; 8. [PMID: 31942240 PMCID: PMC6944264 DOI: 10.12688/f1000research.20942.1] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/18/2019] [Indexed: 12/12/2022] Open
Abstract
The development of adhesive connections between cells was critical for the evolution of multicellularity and for organizing cells into complex organs with discrete compartments. Four types of intercellular junction are present in vertebrates: desmosomes, adherens junctions, tight junctions, and gap junctions. All are essential for the development of the embryonic layers and organs as well as adult tissue homeostasis. While each junction type is defined as a distinct entity, it is now clear that they cooperate physically and functionally to create a robust and functionally diverse system. During evolution, desmosomes first appeared in vertebrates as highly specialized regions at the plasma membrane that couple the intermediate filament cytoskeleton at points of strong cell–cell adhesion. Here, we review how desmosomes conferred new mechanical and signaling properties to vertebrate cells and tissues through their interactions with the existing junctional and cytoskeletal network.
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Affiliation(s)
- Kathleen J Green
- Departments of Pathology and Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA
| | - Avinash Jaiganesh
- Departments of Pathology and Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Joshua A Broussard
- Departments of Pathology and Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, IL, USA
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11
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Sun C, Wang L, Yang XX, Jiang YH, Guo XL. The aberrant expression or disruption of desmocollin2 in human diseases. Int J Biol Macromol 2019; 131:378-386. [DOI: 10.1016/j.ijbiomac.2019.03.041] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 03/05/2019] [Accepted: 03/05/2019] [Indexed: 12/21/2022]
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12
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Abstract
Desmosomes are junctional protein complexes that confer strong adhesive capacity to adjacent host cells. In a recent study, we showed that enteropathogenic Escherichia coli (EPEC) disrupts desmosomes, weakens cell-cell adhesion and perturbs barrier function of intestinal epithelial (C2BBe) cells. Desmosomal damage was dependent on the EPEC effector protein EspH and its inhibitory effect on Rho GTPases. EspH-mediated Rho inactivation resulted in retraction of keratin intermediate filaments and degradation of desmosomal cadherins. Immunofluorescence studies of EPEC-infected C2BBe cells revealed keratin retraction towards the nucleus coincident with significant cytoplasmic redistribution of the desmosomal cadherin desmoglein-2 (DSG2). In this addendum, we expand on how EPEC-induced keratin retraction leads to loss of DSG2 anchoring at the junctions, and show that maturity of the epithelial cell monolayer impacts the fate of desmosomes during infection.
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Affiliation(s)
- Jennifer Lising Roxas
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA
| | - Gayatri Vedantam
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA,Department of Immunobiology, University of Arizona, Tucson, AZ, USA,BIO5 Institute for Collaborative Research, University of Arizona, Tucson, AZ, USA,Southern Arizona VA Healthcare System, Tucson, AZ, USA
| | - V.K. Viswanathan
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA,Department of Immunobiology, University of Arizona, Tucson, AZ, USA,BIO5 Institute for Collaborative Research, University of Arizona, Tucson, AZ, USA,CONTACT V.K. Viswanathan, Ph.D. School of Animal & Comparative Biomedical Sciences, University of Arizona, 1007 E. Lowell, Building 106, Rm. 231, Tucson, AZ 85721, USA
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13
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Chiarella SE, Rabin EE, Ostilla LA, Flozak AS, Gottardi CJ. αT-catenin: A developmentally dispensable, disease-linked member of the α-catenin family. Tissue Barriers 2018; 6:e1463896. [PMID: 29746206 PMCID: PMC6179130 DOI: 10.1080/21688370.2018.1463896] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/19/2018] [Accepted: 02/23/2018] [Indexed: 02/07/2023] Open
Abstract
α-Catenins are actin-filament binding proteins and critical subunits of the cadherin-catenin cell-cell adhesive complex. They are found in nominally-defined epithelial (E), neural (N), and testis (T) forms transcribed from three distinct genes. While most of α-catenin research has focused on the developmentally essential founding member, αE-catenin, this review discusses recent studies on αT-catenin (CTNNA3), a developmentally dispensable isoform that is emerging as relevant to cardiac, allergic and neurological diseases.
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Affiliation(s)
- Sergio E. Chiarella
- Department of Medicine
- Cellular and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Erik E. Rabin
- Department of Medicine
- Weinberg College of Arts and Sciences, Northwestern University, Evanston, IL
| | - Lorena A. Ostilla
- Department of Medicine
- Cellular and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Annette S. Flozak
- Department of Medicine
- Cellular and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, IL
| | - Cara J. Gottardi
- Department of Medicine
- Cellular and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, IL
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14
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Buttner P, Galli R, Husser D, Bollmann A. Label-free Imaging of Myocardial Remodeling in Atrial Fibrillation Using Nonlinear Optical Microscopy: A Feasibility Study. J Atr Fibrillation 2018; 10:1644. [PMID: 29988238 DOI: 10.4022/jafib.1644] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 02/23/2018] [Accepted: 02/24/2018] [Indexed: 01/21/2023]
Abstract
Atrial fibrillation, characterized by rapid disorganized electrical activation of myocardium, is caused by and accompanied by remodeling of myocardial tissue. We applied nonlinear optical microscopy (NLOM) to visualize typical myocardial features and atrial fibrillation effects in order to test anon-destructive imaging technology that in principle can be applied in vivo.Coherent anti-Stokes Raman scattering, endogenous two-photon excited fluorescence, and second harmonic generation were used to inspect unstained human atrial myocardium from three patients who underwent surgical Cox-MAZE procedure with amputation of left atrial appendage. Using NLOM techniques, we collected detailrich pictures of unstained tissue that enable comprehensive characterization of myocardial characteristics like myocyte structure, collagen and lipofuscin deposition, intercalating disc width, and fatty degradation. Development of in vivo application of the NLOM technique may represent a revolutionary approach in characterizing atrial fibrillation associated myocardial remodeling with important implications for therapy individualization and monitoring.
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Affiliation(s)
- Petra Buttner
- Department of Electrophysiology, Heart Center Leipzig, Strumpellstrabe 39, 04289 Leipzig, Germany
| | - Roberta Galli
- Clinical Sensoring and Monitoring, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine Carl Gustav Carus, TU Dresden, Fetscherstrabe 74, 01307 Dresden, Germany
| | - Daniela Husser
- Department of Electrophysiology, Heart Center Leipzig, Strumpellstrabe 39, 04289 Leipzig, Germany
| | - Andreas Bollmann
- Department of Electrophysiology, Heart Center Leipzig, Strumpellstrabe 39, 04289 Leipzig, Germany
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15
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Affiliation(s)
- Nicole A. Najor
- Department of Biology, University of Detroit Mercy, Detroit, Michigan 48221
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16
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Ackermann MA, King B, Lieberman NAP, Bobbili PJ, Rudloff M, Berndsen CE, Wright NT, Hecker PA, Kontrogianni-Konstantopoulos A. Novel obscurins mediate cardiomyocyte adhesion and size via the PI3K/AKT/mTOR signaling pathway. J Mol Cell Cardiol 2017; 111:27-39. [PMID: 28826662 PMCID: PMC5694667 DOI: 10.1016/j.yjmcc.2017.08.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 12/29/2022]
Abstract
The intercalated disc of cardiac muscle embodies a highly-ordered, multifunctional network, essential for the synchronous contraction of the heart. Over 200 known proteins localize to the intercalated disc. The challenge now lies in their characterization as it relates to the coupling of neighboring cells and whole heart function. Using molecular, biochemical and imaging techniques, we characterized for the first time two small obscurin isoforms, obscurin-40 and obscurin-80, which are enriched at distinct locations of the intercalated disc. Both proteins bind specifically and directly to select phospholipids via their pleckstrin homology (PH) domain. Overexpression of either isoform or the PH-domain in cardiomyocytes results in decreased cell adhesion and size via reduced activation of the PI3K/AKT/mTOR pathway that is intimately linked to cardiac hypertrophy. In addition, obscurin-80 and obscurin-40 are significantly reduced in acute (myocardial infarction) and chronic (pressure overload) murine cardiac-stress models underscoring their key role in maintaining cardiac homeostasis. Our novel findings implicate small obscurins in the maintenance of cardiomyocyte size and coupling, and the development of heart failure by antagonizing the PI3K/AKT/mTOR pathway.
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Affiliation(s)
- Maegen A Ackermann
- Department of Biochemistry and Molecular Biology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States; Department of Physiology and Cell Biology, Wexner College of Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, United States.
| | - Brendan King
- Department of Biochemistry and Molecular Biology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States
| | - Nicole A P Lieberman
- Department of Biochemistry and Molecular Biology, University of Maryland, School of Medicine, Baltimore, MD 21201, United States
| | - Prameela J Bobbili
- Department of Physiology and Cell Biology, Wexner College of Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, United States
| | - Michael Rudloff
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, United States
| | - Christopher E Berndsen
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, United States
| | - Nathan T Wright
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, VA 22807, United States
| | - Peter A Hecker
- Division of Cardiology and Department of Medicine, University of Maryland, Baltimore, MD 20201, United States
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Turkowski KL, Tester DJ, Bos JM, Haugaa KH, Ackerman MJ. Whole exome sequencing with genomic triangulation implicatesCDH2-encoded N-cadherin as a novel pathogenic substrate for arrhythmogenic cardiomyopathy. CONGENIT HEART DIS 2017; 12:226-235. [DOI: 10.1111/chd.12462] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 03/01/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Kari L. Turkowski
- Mayo Clinic Graduate School of Biomedical Sciences; Mayo Clinic; Rochester Minnesota USA
| | - David J. Tester
- Department of Molecular Pharmacology & Experimental Therapeutics; Windland Smith Rice Sudden Death Genomics Laboratory; Mayo Clinic; Rochester Minnesota USA
- Department of Cardiovascular Diseases, Division of Heart Rhythm Services; Mayo Clinic; Rochester Minnesota USA
| | - J. Martijn Bos
- Department of Molecular Pharmacology & Experimental Therapeutics; Windland Smith Rice Sudden Death Genomics Laboratory; Mayo Clinic; Rochester Minnesota USA
- Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology; Mayo Clinic; Rochester Minnesota USA
| | - Kristina H. Haugaa
- Center for Cardiological Innovation, Department of Cardiology; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo Norway and University of Oslo; Oslo Norway
| | - Michael J. Ackerman
- Department of Molecular Pharmacology & Experimental Therapeutics; Windland Smith Rice Sudden Death Genomics Laboratory; Mayo Clinic; Rochester Minnesota USA
- Department of Cardiovascular Diseases, Division of Heart Rhythm Services; Mayo Clinic; Rochester Minnesota USA
- Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology; Mayo Clinic; Rochester Minnesota USA
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18
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Gurha P, Chen X, Lombardi R, Willerson JT, Marian AJ. Knockdown of Plakophilin 2 Downregulates miR-184 Through CpG Hypermethylation and Suppression of the E2F1 Pathway and Leads to Enhanced Adipogenesis In Vitro. Circ Res 2016; 119:731-50. [PMID: 27470638 DOI: 10.1161/circresaha.116.308422] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 07/28/2016] [Indexed: 12/15/2022]
Abstract
RATIONALE PKP2, encoding plakophilin 2 (PKP2), is the most common causal gene for arrhythmogenic cardiomyopathy. OBJECTIVE To characterize miRNA expression profile in PKP2-deficient cells. METHODS AND RESULTS Control and PKP2-knockdown HL-1 (HL-1(Pkp2-shRNA)) cells were screened for 750 miRNAs using low-density microfluidic panels. Fifty-nine miRNAs were differentially expressed. MiR-184 was the most downregulated miRNA. Expression of miR-184 in the heart and cardiac myocyte was developmentally downregulated and was low in mature myocytes. MicroRNA-184 was predominantly expressed in cardiac mesenchymal progenitor cells. Knockdown of Pkp2 in cardiac mesenchymal progenitor cells also reduced miR-184 levels. Expression of miR-184 was transcriptionally regulated by the E2F1 pathway, which was suppressed in PKP2-deficient cells. Activation of E2F1, on overexpression of its activator CCND1 (cyclin D1) or knockdown of its inhibitor retinoblastoma 1, partially rescued miR-184 levels. In addition, DNA methyltransferase-1 was recruited to the promoter region of miR-184, and the CpG sites at the upstream region of miR-184 were hypermethylated. Treatment with 5-aza-2'-deoxycytidine, a demethylation agent, and knockdown of DNA methyltransferase-1 partially rescued miR-184 level. Pathway analysis of paired miR-184:mRNA targets identified cell proliferation, differentiation, and death as the main affected biological processes. Knockdown of miR-184 in HL-1 cells and mesenchymal progenitor cells induced and, conversely, its overexpression attenuated adipogenesis. CONCLUSIONS PKP2 deficiency leads to suppression of the E2F1 pathway and hypermethylation of the CpG sites at miR-184 promoter, resulting in downregulation of miR-184 levels. Suppression of miR-184 enhances and its activation attenuates adipogenesis in vitro. Thus, miR-184 contributes to the pathogenesis of adipogenesis in PKP2-deficient cells.
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Affiliation(s)
- Priyatansh Gurha
- From the Center for Cardiovascular Genetics, Institute of Molecular Medicine and Department of Medicine, University of Texas Health Sciences Center at Houston, and Texas Heart Institute
| | - Xiaofan Chen
- From the Center for Cardiovascular Genetics, Institute of Molecular Medicine and Department of Medicine, University of Texas Health Sciences Center at Houston, and Texas Heart Institute
| | - Raffaella Lombardi
- From the Center for Cardiovascular Genetics, Institute of Molecular Medicine and Department of Medicine, University of Texas Health Sciences Center at Houston, and Texas Heart Institute
| | - James T Willerson
- From the Center for Cardiovascular Genetics, Institute of Molecular Medicine and Department of Medicine, University of Texas Health Sciences Center at Houston, and Texas Heart Institute
| | - Ali J Marian
- From the Center for Cardiovascular Genetics, Institute of Molecular Medicine and Department of Medicine, University of Texas Health Sciences Center at Houston, and Texas Heart Institute.
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19
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George SA, Bonakdar M, Zeitz M, Davalos RV, Smyth JW, Poelzing S. Extracellular sodium dependence of the conduction velocity-calcium relationship: evidence of ephaptic self-attenuation. Am J Physiol Heart Circ Physiol 2016; 310:H1129-39. [PMID: 26945081 DOI: 10.1152/ajpheart.00857.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 03/02/2016] [Indexed: 11/22/2022]
Abstract
Our laboratory previously demonstrated that perfusate sodium and potassium concentrations can modulate cardiac conduction velocity (CV) consistent with theoretical predictions of ephaptic coupling (EpC). EpC depends on the ionic currents and intercellular separation in sodium channel rich intercalated disk microdomains like the perinexus. We suggested that perinexal width (WP) correlates with changes in extracellular calcium ([Ca(2+)]o). Here, we test the hypothesis that increasing [Ca(2+)]o reduces WP and increases CV. Mathematical models of EpC also predict that reducing WP can reduce sodium driving force and CV by self-attenuation. Therefore, we further hypothesized that reducing WP and extracellular sodium ([Na(+)]o) will reduce CV consistent with ephaptic self-attenuation. Transmission electron microscopy revealed that increasing [Ca(2+)]o (1 to 3.4 mM) significantly decreased WP Optically mapping wild-type (WT) (100% Cx43) mouse hearts demonstrated that increasing [Ca(2+)]o increases transverse CV during normonatremia (147.3 mM), but slows transverse CV during hyponatremia (120 mM). Additionally, CV in heterozygous (∼50% Cx43) hearts was more sensitive to changes in [Ca(2+)]o relative to WT during normonatremia. During hyponatremia, CV slowed in both WT and heterozygous hearts to the same extent. Importantly, neither [Ca(2+)]o nor [Na(+)]o altered Cx43 expression or phosphorylation determined by Western blotting, or gap junctional resistance determined by electrical impedance spectroscopy. Narrowing WP, by increasing [Ca(2+)]o, increases CV consistent with enhanced EpC between myocytes. Interestingly, during hyponatremia, reducing WP slowed CV, consistent with theoretical predictions of ephaptic self-attenuation. This study suggests that serum ion concentrations may be an important determinant of cardiac disease expression.
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Affiliation(s)
- Sharon A George
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - Mohammad Bonakdar
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; and
| | - Michael Zeitz
- Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
| | - Rafael V Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; and
| | - James W Smyth
- Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
| | - Steven Poelzing
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia; Virginia Tech Carilion Research Institute and Center for Heart and Regenerative Medicine, Roanoke, Virginia
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20
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Abstract
Currently, the exact role of telocytes within fascial structures is unknown. The morphology, distribution and behaviour of fascial telocytes as well as the mutual relationship between telocytes and other cellular fascia constituents should be definitely a subject of further studies. It will contribute to better understanding of the role of the fascial system in health and diseases, may shed light on the regeneration potential of these tissues and may help to find targets for future treatments for locomotor disorders, including fascial diseases. Last but not least, confirmation of the presence of telocytes within fascia may contribute to optimise the use of fascia as a graft material.
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21
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Vermillion KL, Jagtap P, Johnson JE, Griffin TJ, Andrews MT. Characterizing Cardiac Molecular Mechanisms of Mammalian Hibernation via Quantitative Proteogenomics. J Proteome Res 2015; 14:4792-804. [DOI: 10.1021/acs.jproteome.5b00575] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Katie L. Vermillion
- Department
of Biology, University of Minnesota Duluth, 1035 Kirby Drive, Duluth, Minnesota 55812, United States
| | - Pratik Jagtap
- Center
for Mass Spectrometry and Proteomics, University of Minnesota, 1479 Gortner
Avenue, St. Paul, Minnesota 55108, United States
- Department
of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, Minnesota 55455, United States
| | - James E. Johnson
- Minnesota Supercomputing Institute, 512 Walter Library 117 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Timothy J. Griffin
- Center
for Mass Spectrometry and Proteomics, University of Minnesota, 1479 Gortner
Avenue, St. Paul, Minnesota 55108, United States
- Department
of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church St SE, Minneapolis, Minnesota 55455, United States
| | - Matthew T. Andrews
- Department
of Biology, University of Minnesota Duluth, 1035 Kirby Drive, Duluth, Minnesota 55812, United States
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22
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Abstract
Arrhythmogenic cardiomyopathy (ACM) is a primary myocardial disease. It is characterized by frequent ventricular arrhythmias and increased risk of sudden cardiac death typically arising as an early manifestation before the onset of significant myocardial remodelling. Myocardial degeneration, often confined to the right ventricular free wall, with replacement by fibrofatty scar tissue, develops in many patients. ACM is a familial disease but genetic penetrance can be low and disease expression is highly variable. Inflammation might promote disease progression. It also appears that exercise increases disease penetrance and accelerates its development. More than 60% of probands harbour mutations in genes that encode desmosomal proteins, which has raised the possibility that defective cell-cell adhesion might play a role in disease pathogenesis. Recent advances have implicated changes in the canonical wingless-type mouse mammary tumour virus integration site (Wnt)/β-catenin and Hippo signalling pathways and defects in forwarding trafficking of ion channels and other proteins to the intercalated disk in cardiac myocytes. In this review we summarize the current understanding of the pathogenesis of ACM and highlight future research directions.
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Affiliation(s)
- Angeliki Asimaki
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Andre G Kleber
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.
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23
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Campuzano O, Alcalde M, Berne P, Zorio E, Iglesias A, Navarro-Manchón J, Brugada J, Brugada R. Role of novel DSP_p.Q986X genetic variation in arrhythmogenic right ventricular cardiomyopathy. Eur J Med Genet 2013; 56:541-5. [PMID: 23954618 DOI: 10.1016/j.ejmg.2013.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 08/02/2013] [Indexed: 10/26/2022]
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24
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Wilson AJ, Schoenauer R, Ehler E, Agarkova I, Bennett PM. Cardiomyocyte growth and sarcomerogenesis at the intercalated disc. Cell Mol Life Sci 2013; 71:165-81. [PMID: 23708682 PMCID: PMC3889684 DOI: 10.1007/s00018-013-1374-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/27/2013] [Accepted: 05/13/2013] [Indexed: 12/02/2022]
Abstract
Cardiomyocytes grow during heart maturation or disease-related cardiac remodeling. We present evidence that the intercalated disc (ID) is integral to both longitudinal and lateral growth: increases in width are accommodated by lateral extension of the plicate tread regions and increases in length by sarcomere insertion within the ID. At the margin between myofibril and the folded membrane of the ID lies a transitional junction through which the thin filaments from the last sarcomere run to the ID membrane and it has been suggested that this junction acts as a proto Z-disc for sarcomere addition. In support of this hypothesis, we have investigated the ultrastructure of the ID in mouse hearts from control and dilated cardiomyopathy (DCM) models, the MLP-null and a cardiac-specific β-catenin mutant, cΔex3, as well as in human left ventricle from normal and DCM samples. We find that the ID amplitude can vary tenfold from 0.2 μm up to a maximum of ~2 μm allowing gradual expansion during heart growth. At the greatest amplitude, equivalent to a sarcomere length, A-bands and thick filaments are found within the ID membrane loops together with a Z-disc, which develops at the transitional junction position. Here, also, the tops of the membrane folds, which are rich in αII spectrin, become enlarged and associated with junctional sarcoplasmic reticulum. Systematically larger ID amplitudes are found in DCM samples. Other morphological differences between mouse DCM and normal hearts suggest that sarcomere inclusion is compromised in the diseased hearts.
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Affiliation(s)
- Amanda J Wilson
- Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London, SE1 1UL, UK,
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25
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Kowalczyk AP, Green KJ. Structure, function, and regulation of desmosomes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 116:95-118. [PMID: 23481192 DOI: 10.1016/b978-0-12-394311-8.00005-4] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Desmosomes are adhesive intercellular junctions that mechanically integrate adjacent cells by coupling adhesive interactions mediated by desmosomal cadherins to the intermediate filament cytoskeletal network. Desmosomal cadherins are connected to intermediate filaments by densely clustered cytoplasmic plaque proteins comprising members of the armadillo gene family, including plakoglobin and plakophilins, and members of the plakin family of cytolinkers, such as desmoplakin. The importance of desmosomes in tissue integrity is highlighted by human diseases caused by mutations in desmosomal genes, autoantibody attack of desmosomal cadherins, and bacterial toxins that selectively target desmosomal cadherins. In addition to reviewing the well-known roles of desmosomal proteins in tissue integrity, this chapter also highlights the growing appreciation for how desmosomal proteins are integrated with cell signaling pathways to contribute to vertebrate tissue organization and differentiation.
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Affiliation(s)
- Andrew P Kowalczyk
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia, USA
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26
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Wang Q, Lin JLC, Chan SY, Lin JJC. The Xin repeat-containing protein, mXinβ, initiates the maturation of the intercalated discs during postnatal heart development. Dev Biol 2012; 374:264-80. [PMID: 23261932 DOI: 10.1016/j.ydbio.2012.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 11/25/2012] [Accepted: 12/04/2012] [Indexed: 10/27/2022]
Abstract
The intercalated disc (ICD) is a unique structure to the heart and plays vital roles in communication and signaling among cardiomyocytes. ICDs are formed and matured during postnatal development through a profound redistribution of the intercellular junctions, as well as recruitment and assembly of more than 200 proteins at the termini of cardiomyocytes. The molecular mechanism underlying this process is not completely understood. The mouse orthologs (mXinα and mXinβ) of human cardiomyopathy-associated (CMYA)/Xin actin-binding repeat-containing protein (XIRP) genes (CMYA1/XIRP1 and CMYA3/XIRP2, respectively) encode proteins localized to ICDs. Ablation of mXinα results in adult late-onset cardiomyopathy with conduction defects and up-regulation of mXinβ. ICD structural defects are found in adult but not juvenile mXinα-null hearts. On the other hand, loss of mXinβ leads to ICD defects at postnatal day 16.5, a developmental stage when the heart is forming ICDs, suggesting mXinβ is required for ICD formation. Using quantitative Western blot, we showed in this study that mXinβ but not mXinα was uniquely up-regulated during the redistribution of intercellular junction from the lateral membrane of cardiomyocytes to their termini. In the absence of mXinβ, the intercellular junctions failed to be restricted to the termini of the cells, and the onset of such defect correlated with the peak expression of mXinβ. Immunofluorescence staining and subcellular fractionation showed that mXinβ preferentially associated with the forming ICDs, further suggesting that mXinβ functioned locally to promote ICD maturation. In contrast, the spatiotemporal expression profile of mXinα and the lack of more severe ICD defects in mXinα-/-;mXinβ-/- double knockout hearts than in mXinβ-/- hearts suggested that mXinα was not essential for the postnatal formation of ICDs. A two-step model for the development of ICD is proposed where mXinβ is essential for the redistribution of intercellular junction components from the lateral puncta to the cell termini.
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Affiliation(s)
- Qinchuan Wang
- Department of Biology, University of Iowa, Iowa City, IA 52242-1324, USA
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27
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Hong M, Bao L, Kefaloyianni E, Agullo-Pascual E, Chkourko H, Foster M, Taskin E, Zhandre M, Reid DA, Rothenberg E, Delmar M, Coetzee WA. Heterogeneity of ATP-sensitive K+ channels in cardiac myocytes: enrichment at the intercalated disk. J Biol Chem 2012; 287:41258-67. [PMID: 23066018 DOI: 10.1074/jbc.m112.412122] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ventricular ATP-sensitive potassium (K(ATP)) channels link intracellular energy metabolism to membrane excitability and contractility. Our recent proteomics experiments identified plakoglobin and plakophilin-2 (PKP2) as putative K(ATP) channel-associated proteins. We investigated whether the association of K(ATP) channel subunits with junctional proteins translates to heterogeneous subcellular distribution within a cardiac myocyte. Co-immunoprecipitation experiments confirmed physical interaction between K(ATP) channels and PKP2 and plakoglobin in rat heart. Immunolocalization experiments demonstrated that K(ATP) channel subunits (Kir6.2 and SUR2A) are expressed at a higher density at the intercalated disk in mouse and rat hearts, where they co-localized with PKP2 and plakoglobin. Super-resolution microscopy demonstrate that K(ATP) channels are clustered within nanometer distances from junctional proteins. The local K(ATP) channel density, recorded in excised inside-out patches, was larger at the cell end when compared with local currents recorded from the cell center. The K(ATP) channel unitary conductance, block by MgATP and activation by MgADP, did not differ between these two locations. Whole cell K(ATP) channel current density (activated by metabolic inhibition) was ∼40% smaller in myocytes from mice haploinsufficient for PKP2. Experiments with excised patches demonstrated that the regional heterogeneity of K(ATP) channels was absent in the PKP2 deficient mice, but the K(ATP) channel unitary conductance and nucleotide sensitivities remained unaltered. Our data demonstrate heterogeneity of K(ATP) channel distribution within a cardiac myocyte. The higher K(ATP) channel density at the intercalated disk implies a possible role at the intercellular junctions during cardiac ischemia.
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Affiliation(s)
- Miyoun Hong
- Department of Pediatrics, New York University School of Medicine, New York, New York 10016, USA
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28
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Rizzo S, Lodder EM, Verkerk AO, Wolswinkel R, Beekman L, Pilichou K, Basso C, Remme CA, Thiene G, Bezzina CR. Intercalated disc abnormalities, reduced Na(+) current density, and conduction slowing in desmoglein-2 mutant mice prior to cardiomyopathic changes. Cardiovasc Res 2012; 95:409-18. [PMID: 22764152 DOI: 10.1093/cvr/cvs219] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
AIMS Mutations in genes encoding desmosomal proteins have been implicated in the pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC). However, the consequences of these mutations in early disease stages are unknown. We investigated whether mutation-induced intercalated disc remodelling impacts on electrophysiological properties before the onset of cell death and replacement fibrosis. METHODS AND RESULTS Transgenic mice with cardiac overexpression of mutant Desmoglein2 (Dsg2) Dsg2-N271S (Tg-NS/L) were studied before and after the onset of cell death and replacement fibrosis. Mice with cardiac overexpression of wild-type Dsg2 and wild-type mice served as controls. Assessment by electron microscopy established that intercellular space widening at the desmosomes/adherens junctions occurred in Tg-NS/L mice before the onset of necrosis and fibrosis. At this stage, epicardial mapping in Langendorff-perfused hearts demonstrated prolonged ventricular activation time, reduced longitudinal and transversal conduction velocities, and increased arrhythmia inducibility. A reduced action potential (AP) upstroke velocity due to a lower Na(+) current density was also observed at this stage of the disease. Furthermore, co-immunoprecipitation demonstrated an in vivo interaction between Dsg2 and the Na(+) channel protein Na(V)1.5. CONCLUSION Intercellular space widening at the level of the intercalated disc (desmosomes/adherens junctions) and a concomitant reduction in AP upstroke velocity as a consequence of lower Na(+) current density lead to slowed conduction and increased arrhythmia susceptibility at disease stages preceding the onset of necrosis and replacement fibrosis. The demonstration of an in vivo interaction between Dsg2 and Na(V)1.5 provides a molecular pathway for the observed electrical disturbances during the early ARVC stages.
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Affiliation(s)
- Stefania Rizzo
- Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Padua 35121, Italy
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29
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Lodder EM, Rizzo S. Mouse models in arrhythmogenic right ventricular cardiomyopathy. Front Physiol 2012; 3:221. [PMID: 22737134 PMCID: PMC3380338 DOI: 10.3389/fphys.2012.00221] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 06/02/2012] [Indexed: 01/17/2023] Open
Abstract
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disorder characterized by fibro-fatty replacement of cardiomyocytes. The cardinal manifestations are arrhythmias, sudden cardiac death, and seldom heart failure. Mutations in genes encoding desmosomal proteins and their interaction partners have been implicated in the pathogenesis of ARVC and it is now widely accepted that ARVC is a disease caused by abnormal cell–cell adhesion. The mechanism(s) by which mutations in desmosomal proteins lead to fibro-fatty replacement remains to be fully elucidated. To this aim over the last 10 years different transgenic and targeted mouse models have been developed, these models and what they have taught us will be discussed in this review.
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Affiliation(s)
- Elisabeth M Lodder
- Department of Experimental Cardiology, Heart Failure Research Center, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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30
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Cardiac telocytes - their junctions and functional implications. Cell Tissue Res 2012; 348:265-79. [PMID: 22350946 PMCID: PMC3349856 DOI: 10.1007/s00441-012-1333-8] [Citation(s) in RCA: 204] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 01/10/2012] [Indexed: 12/11/2022]
Abstract
Telocytes (TCs) form a cardiac network of interstitial cells. Our previous studies have shown that TCs are involved in heterocellular contacts with cardiomyocytes and cardiac stem/progenitor cells. In addition, TCs frequently establish ‘stromal synapses’ with several types of immunoreactive cells in various organs (www.telocytes.com). Using electron microscopy (EM) and electron microscope tomography (ET), we further investigated the interstitial cell network of TCs and found that TCs form ‘atypical’ junctions with virtually all types of cells in the human heart. EM and ET showed different junction types connecting TCs in a network (puncta adhaerentia minima, processus adhaerentes and manubria adhaerentia). The connections between TCs and cardiomyocytes are ‘dot’ junctions with nanocontacts or asymmetric junctions. Junctions between stem cells and TCs are either ‘stromal synapses’ or adhaerens junctions. An unexpected finding was that TCs have direct cell–cell (nano)contacts with Schwann cells, endothelial cells and pericytes. Therefore, ultrastructural analysis proved that the cardiac TC network could integrate the overall ‘information’ from vascular system (endothelial cells and pericytes), nervous system (Schwann cells), immune system (macrophages, mast cells), interstitium (fibroblasts, extracellular matrix), stem cells/progenitors and working cardiomyocytes. Generally, heterocellular contacts occur by means of minute junctions (point contacts, nanocontacts and planar contacts) and the mean intermembrane distance is within the macromolecular interaction range (10–30 nm). In conclusion, TCs make a network in the myocardial interstitium, which is involved in the long-distance intercellular signaling coordination. This integrated interstitial system appears to be composed of large homotropic zones (TC–TC junctions) and limited (distinct) heterotropic zones (heterocellular junctions of TCs).
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31
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Brooke MA, Nitoiu D, Kelsell DP. Cell-cell connectivity: desmosomes and disease. J Pathol 2011; 226:158-71. [PMID: 21989576 DOI: 10.1002/path.3027] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 01/12/2023]
Abstract
Cell-cell connectivity is an absolute requirement for the correct functioning of cells, tissues and entire organisms. At the level of the individual cell, direct cell-cell adherence and communication is mediated by the intercellular junction complexes: desmosomes, adherens, tight and gap junctions. A broad spectrum of inherited, infectious and auto-immune diseases can affect the proper function of intercellular junctions and result in either diseases affecting specific individual tissues or widespread syndromic conditions. A particularly diverse group of diseases result from direct or indirect disruption of desmosomes--a consequence of their importance in tissue integrity, their extensive distribution, complex structure, and the wide variety of functions their components accomplish. As a consequence, disruption of desmosomal assembly, structure or integrity disrupts not only their intercellular adhesive function but also their functions in cell communication and regulation, leading to such diverse pathologies as cardiomyopathy, epidermal and mucosal blistering, palmoplantar keratoderma, woolly hair, keratosis, epidermolysis bullosa, ectodermal dysplasia and alopecia. Here, as well as describing the importance of the other intercellular junctions, we focus primarily on the desmosome, its structure and its role in disease. We will examine the various pathologies that result from impairment of desmosome function and thereby demonstrate the importance of desmosomes to tissues and to the organism as a whole.
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Affiliation(s)
- Matthew A Brooke
- Centre for Cutaneous Research, Blizard Institute, Barts and the London School of Medicine and Dentistry, London, UK
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32
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Gherghiceanu M, Popescu LM. Heterocellular communication in the heart: electron tomography of telocyte-myocyte junctions. J Cell Mol Med 2011; 15:1005-11. [PMID: 21426485 PMCID: PMC3922684 DOI: 10.1111/j.1582-4934.2011.01299.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Myocardium is composed of two main cell populations: cardiomyocytes (CMs) and interstitial cells (e.g. fibroblasts, immunoreactive cells, capillaries). However, very recently we have showed that a novel type of interstitial cell called telocytes (TCs) does exist in epi-, myo- and endocardium. They have very long and thin telopodes (Tp) formed by alternating podomeres and podoms. Heterocellular communication between TCs and CMs it is supposed to occur by shed vesicles and close apposition. If TCs have to play a role in cardiac physiology it is expected to develop direct and unambiguous contacts with CMs. Because a clear membrane-to-membrane junction has not been reported by electron microscopy we have investigated the heterocellular communication in the mouse heart by electron tomography. This advanced technique showed that small dense structures (10-15 nm nanocontacts) directly connect TCs with CMs. More complex and atypical junctions could be observed between TCs and CMs at the level of intercalated discs. This study proves that TCs and CMs are directly connected and might represent a 'functional unit'.
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Palatinus JA, Rhett JM, Gourdie RG. The connexin43 carboxyl terminus and cardiac gap junction organization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1831-43. [PMID: 21856279 DOI: 10.1016/j.bbamem.2011.08.006] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Revised: 07/25/2011] [Accepted: 08/03/2011] [Indexed: 12/09/2022]
Abstract
The precise spatial order of gap junctions at intercalated disks in adult ventricular myocardium is thought vital for maintaining cardiac synchrony. Breakdown or remodeling of this order is a hallmark of arrhythmic disease of the heart. The principal component of gap junction channels between ventricular cardiomyocytes is connexin43 (Cx43). Protein-protein interactions and modifications of the carboxyl-terminus of Cx43 are key determinants of gap junction function, size, distribution and organization during normal development and in disease processes. Here, we review data on the role of proteins interacting with the Cx43 carboxyl-terminus in the regulation of cardiac gap junction organization, with particular emphasis on Zonula Occludens-1. The rapid progress in this area suggests that in coming years we are likely to develop a fuller understanding of the molecular mechanisms causing pathologic remodeling of gap junctions. With these advances come the promise of novel approach to the treatment of arrhythmia and the prevention of sudden cardiac death. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Joseph A Palatinus
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, USA
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