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Mario Delmar - One of the best experts on this subject based on the ideXlab platform.

  • nanoscale visualization of functional adhesion excitability nodes at the Intercalated Disc
    Nature Communications, 2016
    Co-Authors: Alejandra Leomacias, Esperanza Agullopascual, Jose L Sanchezalonso, Sarah Keegan, Tatiana Arcos, Yuri E Korchev, Julia Gorelik, David Fenyo, Eli Rothenberg, Mario Delmar
    Abstract:

    Intercellular adhesion and electrical excitability are considered separate cellular properties. Studies of myelinated fibres, however, show that voltage-gated sodium channels (VGSCs) aggregate with cell adhesion molecules at Discrete subcellular locations, such as the nodes of Ranvier. Demonstration of similar macromolecular organization in cardiac muscle is missing. Here we combine nanoscale-imaging (single-molecule localization microscopy; electron microscopy; and ‘angle view’ scanning patch clamp) with mathematical simulations to demonstrate distinct hubs at the cardiac Intercalated Disc, populated by clusters of the adhesion molecule N-cadherin and the VGSC NaV1.5. We show that the N-cadherin-NaV1.5 association is not random, that NaV1.5 molecules in these clusters are major contributors to cardiac sodium current, and that loss of NaV1.5 expression reduces intercellular adhesion strength. We speculate that adhesion/excitability nodes are key sites for crosstalk of the contractile and electrical molecular apparatus and may represent the structural substrate of cardiomyopathies in patients with mutations in molecules of the VGSC complex. In myelinated fibres conduction and adhesion proteins aggregate at Discrete foci, but it is unclear if this organization is present in other excitable cells. Using nanoscale visualization and in silico techniques, the authors show that adhesion/excitability nodes exist at the Intercalated Discs of adult cardiac muscle.

  • connexin43 and the regulation of Intercalated Disc function
    Heart Rhythm, 2012
    Co-Authors: Mario Delmar, Fengxia Liang
    Abstract:

    Gap junctions mediate the passage of ions and small molecules between cells. In the adult working cardiac ventricles, gap junctions are formed predominantly by oligomerization of the 43 kDa protein connexin43 (Cx43). It is generally accepted that gap junction-mediated intercellular communication is modulated by changes in the intracellular environment. The activity of various kinases, the concentration of protons or calcium, or the association of Cx43 with other intracellular components, all converge to determine the filtering capabilities of intercellular channels. The most studied post-translational modification of Cx43 is the phosphorylation of amino acids in its C-terminal domain (see, e.g1,2). Additional studies have shown that Cx43 is also a substrate for Ne-lysine acetylation.3 Changes in the ionic intracellular milieu can also, directly or indirectly, regulate the conductive state of Cx43. These modulatory mechanisms are likely to be activated in various pathophysiological states.2 Given the key role of gap junctions in action potential propagation, Cx43 regulation is a subject of intense research, and it is seen as an important pharmacological target for the treatment and/or prevention of cardiac arrhythmias.3-6

  • connexin43 regulates sodium current ankyrin g modulates gap junctions the Intercalated Disc exchanger
    Cardiovascular Research, 2012
    Co-Authors: Mario Delmar
    Abstract:

    Intercalated Disc structures have conventionally been considered to be independent. Recent work shows that molecules initially thought of as belonging to one complex can actually affect another. Here, I focus on the cross-talk between connexin43 (Cx43, ‘the gap junction protein’) and the sodium channel complex and, conversely, on ankyrin-G (AnkG, a ‘component of the sodium channel complex’) and gap junctions. I speculate as to the possibility that one molecule affects the function of the other by regulating its trafficking into the Intercalated Disc.

  • interactions between ankyrin g plakophilin 2 and connexin43 at the cardiac Intercalated Disc
    Circulation Research, 2011
    Co-Authors: Priscila Y Sato, Wanda Coombs, Oxana Nekrasova, Kathleen J Green, Lori L Isom, Steven M Taffet, Mario Delmar
    Abstract:

    Rationale:The early description of the Intercalated Disc defined 3 structures, all of them involved in cell-cell communication: desmosomes, gap junctions, and adherens junctions. Current evidence demonstrates that molecules not involved in providing a physical continuum between cells also populate the Intercalated Disc. Key among them is the voltage-gated sodium channel complex. An important component of this complex is the cytoskeletal adaptor protein Ankyrin-G (AnkG). Objective:To test the hypothesis that AnkG partners with desmosome and gap junction molecules and exerts a functional effect on intercellular communication in the heart. Methods and Results:We used a combination of microscopy, immunochemistry, patch-clamp, and optical mapping to assess the interactions between AnkG, Plakophilin-2, and Connexin43. Coimmunoprecipitation studies from rat heart lysate demonstrated associations between the 3 molecules. With the use of siRNA technology, we demonstrated that loss of AnkG expression caused signifi...

  • abstract 5933 reduced number of gap junctions at the Intercalated Disc in the ventricles of boxer dogs afflicted with arrhythmogenic right ventricular cardiomyopathy arvc
    Circulation, 2008
    Co-Authors: Eva M Oxford, Sydney N Moise, Karen Maass, Mario Delmar
    Abstract:

    ARVC is an inherited myocardial disease associated with sustained monomorphic ventricular tachycardia, sudden cardiac death, and replacement of RV myocardium with fatty or fibro-fatty tissue. Lethal arrhythmias often occur in young patients, before apparent structural damage. It has been hypothesized that loss of Cx43 gap junctions (GJ) may act as a substrate for ventricular arrhythmias in these patients. An inherited form of ARVC is present in the boxer, with clinical symptoms and pathological features similar to those of humans. Here, we used transmission electron microscopy (TEM) to assess the ultrastructure of the Intercalated Disc (ID) in ARVC-afflicted boxers. Samples from the right and left ventricles (RV and LV) of 1 unafflicted beagle, and 3 ARVC afflicted boxers were examined by TEM. Samples from beagle tissue showed normal morphology, good alignment of the sarcomeres and myofibrils, and attachment of myofibrils to the ID. Samples from the ARVC-afflicted boxer lacked myofibril organization, with few attachments to the ID. Within RV and LV longitudinal sections from one afflicted and one control animal, three parameters were measured: ID length, individual GJ length, and number of GJ per ID. No significant differences were found in the length of IDs or of GJs from RV or LV samples of ARVC vs. control. ID length (μm) was 26.8 +/− 5.4 and 44.9+/− 10.6 in control RV and LV, respectively. ID length in afflicted samples was 31.2+/− 5.0 and 52.3+/−13.5 (pNS). GJ length (μm) was .5+/−.03 and .5+/.05 for RV and LV of the control group, and .4+/−.07 and .6+/−,13 in samples obtained from RV and LV of ARVC afflicted animals (pNS). However, our data indicated a significant (p This research has received full or partial funding support from the American Heart Association, AHA Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).

Pauline M. Bennett - One of the best experts on this subject based on the ideXlab platform.

  • Riding the waves of the Intercalated Disc of the heart
    Biophysical Reviews, 2018
    Co-Authors: Pauline M. Bennett
    Abstract:

    Cardiomyocytes interact with each other at their ends through the specialised membrane complex, the Intercalated Disck (ID). It is a fascinating structure. It allows cardiomyocytes to interact with several neighbouring cells, thereby allowing the complex structure of the heart to develop. It acts as tension transducer, structural prop, and multi signalling domain as well as a regulator of growth. It achieves its many functions through a number of specialised domains and intercellular junctions associated with its complex folded membrane. This review outlines the results of some 20 years of fascination with the ups and downs of the ID. These include locating the spectrin-associated membrane cytoskeleton in the ID and investigating the role of Protein 4.1R in calcium signalling; structural studies of the relationship of the ID to myofibrils, sarcoplasmic reticulum and mitochondria and, finally, consideration of the role of the ID in cardiomyocyte growth and heart disease.

  • Sarcoplasmic reticulum is an intermediary of mitochondrial and myofibrillar growth at the Intercalated Disc
    Journal of Muscle Research and Cell Motility, 2016
    Co-Authors: Pauline M. Bennett, Elisabeth Ehler, Amanda J. Wilson
    Abstract:

    In cardiomyocytes columns of intermyofibrillar mitochondria run up to the Intercalated Disc (ID); half are collinear with those in the neighbouring cell, suggesting coordinated addition of sarcomeres and mitochondria both within and between cells during cardiomyocyte growth. Recent evidence for an association between sarcoplasmic reticulum (SR) and mitochondria indicates that the SR may be an intermediary in this coordinated behaviour. For this reason we have investigated the arrangement of SR and t tubules with respect to mitochondria and myofibrils, particularly at the ID. In the body of the cardiomyocyte the mitochondrial columns are frequently intersected by transverse tubules. In addition, we find that a majority of axial tubules are sandwiched between mitochondria and myofibril. No tubules are found at the ID. SR coats mitochondrial columns and fibrils throughout their length and reaches towards the peaks of the ID membrane where it attaches in the form of junctional (j)SR. These peripheral ID couplings are often situated between mitochondria and ID membrane, suggesting an SR connection between the two. In dilated cardiomyopathy (DCM) the mitochondria are somewhat disordered and clumped. In a mouse model for DCM, the muscle LIM protein KO, we find that there is a lack of mitochondria near the ID, suggesting the uncoupling of the myofibril/mitochondria organisation during growth. SR still coats the fibrils and reaches the ID folds in a jSR coupling. Unlike in control tissue, however, loops and long fingers of ID membrane penetrate into the proximal sarcomere suggesting a possible intermediary state in cardiomyocyte growth.

  • the Intercalated Disc a focal point for sarcomere growth and disease
    2015
    Co-Authors: Pauline M. Bennett
    Abstract:

    Heart muscle cells are glued together end to end by the Intercalated Disc (ID), a complex junction fulfilling many functions; it transduces the forces of contraction and transmits electrical signals from one cell to the next; it mechanically holds the cells together and is the site of other signalling pathways including those involved in calcium homeostasis. This chapter aims to describe the functional roles of the ID with respect to the observed structure. Particular emphasis is given to the relationship between myofibrils and the ID, and the evidence for cell growth and sarcomere addition at the ID is presented. Because of its complex nature, it is not surprising that the ID has been implicated in a number of heart diseases and malfunctions. Changes in its structure and composition associated with these heart problems are described with special regard to the role of the ID in dilated cardiomyopathy.

  • cardiomyocyte growth and sarcomerogenesis at the Intercalated Disc
    Cellular and Molecular Life Sciences, 2014
    Co-Authors: Amanda Wilson, Elisabeth Ehler, Roman Schoenauer, Irina Agarkova, Pauline M. Bennett
    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.

  • from myofibril to membrane the transitional junction at the Intercalated Disc
    Frontiers in Bioscience, 2012
    Co-Authors: Pauline M. Bennett
    Abstract:

    : Cardiomyocytes are coordinated by linking together at their ends through the Intercalated Disc. The Intercalated Disc with its complex folded membrane, encompasses many structural and signalling functions and is thought to play a role in cell growth and sarcomere addition. Its relationship to the contractile myofibrils is central to myocyte function. The myofibrils continue their ordered sarcomeric structure up to the edge of the Intercalated Disc where there is no terminal Z-Disc but, instead a transitional junction. Thin actin-containing filaments from the final half sarcomere extend beyond their normal length through the transitional junction to the folded Intercalated Disc membrane where tension is transmitted. The peaks of the membrane folds also occur at the transitional level. They are spectrin rich and associated with sarcoplasmic reticulum vesicles. A subset of Z-Disc proteins including titin, alpha-actinin and ZASP/cypher/oracle are found in the transitional region while others such as telethonin and FATZ/calsarcin/myozenin are absent. The presence of titin enables ordered sarcomeres to be maintained independently of changes in the amplitude of the membrane folds. The transitional junction is therefore poised to act as a site for a new Z-Disc/SR/T-tubule complex and sarcomere addition. The evidence for this is reviewed.

Margaret Anne Craig - One of the best experts on this subject based on the ideXlab platform.

  • dysregulation of cadherins in the Intercalated Disc of the spontaneously hypertensive stroke prone rat
    Journal of Molecular and Cellular Cardiology, 2010
    Co-Authors: Margaret Anne Craig, Martin W. Mcbride, Sarah J. George, Godfrey L Smith, Andrew H Baker
    Abstract:

    The structural integrity of cardiac cells is maintained by the Ca2+-dependent homophilic cell–cell adhesion of cadherins. N-cadherin is responsible for this adhesion under normal physiological conditions. The role of cadherins in adverse cardiac pathology is less clear. We studied the hearts of the stroke-prone spontaneously hypertensive (SHRSP) rat as a genetic model of cardiac hypertrophy and compared them to Wistar–Kyoto control animals. Western blotting of protein homogenates from 12-week old SHRSP animals indicated that similar levels of β, γ-, and α-catenin and T, N and R-cadherin were expressed in the control and SHRSP animals. However, dramatically higher levels of E-cadherin were detected in SHRSP animals compared to controls at 6, 12 and 18 weeks of age. This was confirmed by quantitative Taqman PCR and immunohistochemistry. E-cadherin was located at the Intercalated Disc of the myocytes in co-localisation with connexin 43. Adenoviral overexpression of E-cadherin in rat H9c2 cells and primary rabbit myocytes resulted in a significant reduction in myocyte cell diameter and breadth. E-cadherin overexpression resulted in re-localisation of β-catenin to the cell surface particularly to cell–cell junctions. Subsequent immunohistochemistry of the hearts of WKY and SHRSP animals also revealed increased levels of β-catenin in the Intercalated Disc in the SHRSP compared to WKY. Therefore, remodelling of the Intercalated Disc in the hearts of SHRSP animals may contribute to the altered function observed in these animals.

  • Dysregulation of cadherins in the Intercalated Disc of the spontaneously hypertensive stroke-prone rat
    Journal of Molecular and Cellular Cardiology, 2010
    Co-Authors: Margaret Anne Craig, Godfrey Smith, Martin W. Mcbride, Sarah J. George, Andrew Baker
    Abstract:

    The structural integrity of cardiac cells is maintained by the Ca2+-dependent homophilic cell-cell adhesion of cadherins. N-cadherin is responsible for this adhesion under normal physiological conditions. The role of cadherins in adverse cardiac pathology is less clear. We studied the hearts of the stroke-prone spontaneously hypertensive (SHRSP) rat as a genetic model of cardiac hypertrophy and compared them to Wistar-Kyoto control animals. Western blotting of protein homogenates from 12-week old SHRSP animals indicated that similar levels of β, γ-, and α-catenin and T, N and R-cadherin were expressed in the control and SHRSP animals. However, dramatically higher levels of E-cadherin were detected in SHRSP animals compared to controls at 6, 12 and 18weeks of age. This was confirmed by quantitative Taqman PCR and immunohistochemistry. E-cadherin was located at the Intercalated Disc of the myocytes in co-localisation with connexin 43. Adenoviral overexpression of E-cadherin in rat H9c2 cells and primary rabbit myocytes resulted in a significant reduction in myocyte cell diameter and breadth. E-cadherin overexpression resulted in re-localisation of β-catenin to the cell surface particularly to cell-cell junctions. Subsequent immunohistochemistry of the hearts of WKY and SHRSP animals also revealed increased levels of β-catenin in the Intercalated Disc in the SHRSP compared to WKY. Therefore, remodelling of the Intercalated Disc in the hearts of SHRSP animals may contribute to the altered function observed in these animals. © 2010 Elsevier Ltd.

Andrew Baker - One of the best experts on this subject based on the ideXlab platform.

  • Dysregulation of cadherins in the Intercalated Disc of the spontaneously hypertensive stroke-prone rat
    Journal of Molecular and Cellular Cardiology, 2010
    Co-Authors: Margaret Anne Craig, Godfrey Smith, Martin W. Mcbride, Sarah J. George, Andrew Baker
    Abstract:

    The structural integrity of cardiac cells is maintained by the Ca2+-dependent homophilic cell-cell adhesion of cadherins. N-cadherin is responsible for this adhesion under normal physiological conditions. The role of cadherins in adverse cardiac pathology is less clear. We studied the hearts of the stroke-prone spontaneously hypertensive (SHRSP) rat as a genetic model of cardiac hypertrophy and compared them to Wistar-Kyoto control animals. Western blotting of protein homogenates from 12-week old SHRSP animals indicated that similar levels of β, γ-, and α-catenin and T, N and R-cadherin were expressed in the control and SHRSP animals. However, dramatically higher levels of E-cadherin were detected in SHRSP animals compared to controls at 6, 12 and 18weeks of age. This was confirmed by quantitative Taqman PCR and immunohistochemistry. E-cadherin was located at the Intercalated Disc of the myocytes in co-localisation with connexin 43. Adenoviral overexpression of E-cadherin in rat H9c2 cells and primary rabbit myocytes resulted in a significant reduction in myocyte cell diameter and breadth. E-cadherin overexpression resulted in re-localisation of β-catenin to the cell surface particularly to cell-cell junctions. Subsequent immunohistochemistry of the hearts of WKY and SHRSP animals also revealed increased levels of β-catenin in the Intercalated Disc in the SHRSP compared to WKY. Therefore, remodelling of the Intercalated Disc in the hearts of SHRSP animals may contribute to the altered function observed in these animals. © 2010 Elsevier Ltd.

Andrew H Baker - One of the best experts on this subject based on the ideXlab platform.

  • dysregulation of cadherins in the Intercalated Disc of the spontaneously hypertensive stroke prone rat
    Journal of Molecular and Cellular Cardiology, 2010
    Co-Authors: Margaret Anne Craig, Martin W. Mcbride, Sarah J. George, Godfrey L Smith, Andrew H Baker
    Abstract:

    The structural integrity of cardiac cells is maintained by the Ca2+-dependent homophilic cell–cell adhesion of cadherins. N-cadherin is responsible for this adhesion under normal physiological conditions. The role of cadherins in adverse cardiac pathology is less clear. We studied the hearts of the stroke-prone spontaneously hypertensive (SHRSP) rat as a genetic model of cardiac hypertrophy and compared them to Wistar–Kyoto control animals. Western blotting of protein homogenates from 12-week old SHRSP animals indicated that similar levels of β, γ-, and α-catenin and T, N and R-cadherin were expressed in the control and SHRSP animals. However, dramatically higher levels of E-cadherin were detected in SHRSP animals compared to controls at 6, 12 and 18 weeks of age. This was confirmed by quantitative Taqman PCR and immunohistochemistry. E-cadherin was located at the Intercalated Disc of the myocytes in co-localisation with connexin 43. Adenoviral overexpression of E-cadherin in rat H9c2 cells and primary rabbit myocytes resulted in a significant reduction in myocyte cell diameter and breadth. E-cadherin overexpression resulted in re-localisation of β-catenin to the cell surface particularly to cell–cell junctions. Subsequent immunohistochemistry of the hearts of WKY and SHRSP animals also revealed increased levels of β-catenin in the Intercalated Disc in the SHRSP compared to WKY. Therefore, remodelling of the Intercalated Disc in the hearts of SHRSP animals may contribute to the altered function observed in these animals.