151
|
Calcineurin signaling mediates activity-dependent relocation of the axon initial segment. J Neurosci 2013; 33:6950-63. [PMID: 23595753 DOI: 10.1523/jneurosci.0277-13.2013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The axon initial segment (AIS) is a specialized neuronal subcompartment located at the beginning of the axon that is crucially involved in both the generation of action potentials and the regulation of neuronal polarity. We recently showed that prolonged neuronal depolarization produces a distal shift of the entire AIS structure away from the cell body, a change associated with a decrease in neuronal excitability. Here, we used dissociated rat hippocampal cultures, with a major focus on the dentate granule cell (DGC) population, to explore the signaling pathways underlying activity-dependent relocation of the AIS. First, a pharmacological screen of voltage-gated calcium channels (VGCCs) showed that AIS relocation is triggered by activation of L-type Cav1 VGCCs with negligible contribution from any other VGCC subtypes. Additional pharmacological analysis revealed that downstream signaling events are mediated by the calcium-sensitive phosphatase calcineurin; inhibition of calcineurin with either FK506 or cyclosporin A totally abolished both depolarization- and optogenetically-induced activity-dependent AIS relocation. Furthermore, calcineurin activation is sufficient for AIS plasticity, because expression of a constitutively active form of the phosphatase resulted in relocation of the AIS of DGCs without a depolarizing stimulus. Finally, we assessed the role of calcineurin in other forms of depolarization-induced plasticity. Neither membrane resistance changes nor spine density changes were affected by FK506 treatment, suggesting that calcineurin acts via a separate pathway to modulate AIS plasticity. Together, these results emphasize calcineurin as a vital player in the regulation of intrinsic plasticity as governed by the AIS.
Collapse
|
152
|
Herren AW, Bers DM, Grandi E. Post-translational modifications of the cardiac Na channel: contribution of CaMKII-dependent phosphorylation to acquired arrhythmias. Am J Physiol Heart Circ Physiol 2013; 305:H431-45. [PMID: 23771687 DOI: 10.1152/ajpheart.00306.2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The voltage-gated Na channel isoform 1.5 (NaV1.5) is the pore forming α-subunit of the voltage-gated cardiac Na channel, which is responsible for the initiation and propagation of cardiac action potentials. Mutations in the SCN5A gene encoding NaV1.5 have been linked to changes in the Na current leading to a variety of arrhythmogenic phenotypes, and alterations in the NaV1.5 expression level, Na current density, and/or gating have been observed in acquired cardiac disorders, including heart failure. The precise mechanisms underlying these abnormalities have not been fully elucidated. However, several recent studies have made it clear that NaV1.5 forms a macromolecular complex with a number of proteins that modulate its expression levels, localization, and gating and is the target of extensive post-translational modifications, which may also influence all these properties. We review here the molecular aspects of cardiac Na channel regulation and their functional consequences. In particular, we focus on the molecular and functional aspects of Na channel phosphorylation by the Ca/calmodulin-dependent protein kinase II, which is hyperactive in heart failure and has been causally linked to cardiac arrhythmia. Understanding the mechanisms of altered NaV1.5 expression and function is crucial for gaining insight into arrhythmogenesis and developing novel therapeutic strategies.
Collapse
Affiliation(s)
- Anthony W Herren
- Department of Pharmacology, University of California Davis, Davis, California
| | | | | |
Collapse
|
153
|
Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
Collapse
Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
| | | | | | | | | |
Collapse
|
154
|
Neef S, Maier LS. Novel aspects of excitation-contraction coupling in heart failure. Basic Res Cardiol 2013; 108:360. [PMID: 23740218 DOI: 10.1007/s00395-013-0360-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/18/2013] [Accepted: 03/28/2013] [Indexed: 12/19/2022]
Abstract
Excitation-contraction coupling is the process by which electrical activation is translated into contraction of a cardiac myocyte and thus the heart. In heart failure, expression, phosphorylation, and function of several intracellular proteins that are involved in excitation-contraction coupling are altered. The present review article summarizes central principles and highlights novel aspects of alterations in heart failure, focusing especially on recent findings regarding altered sarcoplasmic reticulum Ca2+ -leak and late Na+ -current without being able to cover all changes in full detail. These two pathomechanisms seem to play interesting roles with respect to systolic and diastolic dysfunction and may also be important for cardiac arrhythmias. Furthermore, the article outlines the translation of these novel findings into potential therapeutic approaches.
Collapse
Affiliation(s)
- Stefan Neef
- Abt. Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Robert-Koch-Str. 40, 37075, Göttingen, Germany
| | | |
Collapse
|
155
|
Maddala R, Nagendran T, de Ridder GG, Schey KL, Rao PV. L-type calcium channels play a critical role in maintaining lens transparency by regulating phosphorylation of aquaporin-0 and myosin light chain and expression of connexins. PLoS One 2013; 8:e64676. [PMID: 23734214 PMCID: PMC3667166 DOI: 10.1371/journal.pone.0064676] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 04/17/2013] [Indexed: 01/18/2023] Open
Abstract
Homeostasis of intracellular calcium is crucial for lens cytoarchitecture and transparency, however, the identity of specific channel proteins regulating calcium influx within the lens is not completely understood. Here we examined the expression and distribution profiles of L-type calcium channels (LTCCs) and explored their role in morphological integrity and transparency of the mouse lens, using cDNA microarray, RT-PCR, immunoblot, pharmacological inhibitors and immunofluorescence analyses. The results revealed that Ca (V) 1.2 and 1.3 channels are expressed and distributed in both the epithelium and cortical fiber cells in mouse lens. Inhibition of LTCCs with felodipine or nifedipine induces progressive cortical cataract formation with time, in association with decreased lens weight in ex-vivo mouse lenses. Histological analyses of felodipine treated lenses revealed extensive disorganization and swelling of cortical fiber cells resembling the phenotype reported for altered aquaporin-0 activity without detectable cytotoxic effects. Analysis of both soluble and membrane rich fractions from felodipine treated lenses by SDS-PAGE in conjunction with mass spectrometry and immunoblot analyses revealed decreases in β-B1-crystallin, Hsp-90, spectrin and filensin. Significantly, loss of transparency in the felodipine treated lenses was preceded by an increase in aquaporin-0 serine-235 phosphorylation and levels of connexin-50, together with decreases in myosin light chain phosphorylation and the levels of 14-3-3ε, a phosphoprotein-binding regulatory protein. Felodipine treatment led to a significant increase in gene expression of connexin-50 and 46 in the mouse lens. Additionally, felodipine inhibition of LTCCs in primary cultures of mouse lens epithelial cells resulted in decreased intracellular calcium, and decreased actin stress fibers and myosin light chain phosphorylation, without detectable cytotoxic response. Taken together, these observations reveal a crucial role for LTCCs in regulation of expression, activity and stability of aquaporin-0, connexins, cytoskeletal proteins, and the mechanical properties of lens, all of which have a vital role in maintaining lens function and cytoarchitecture.
Collapse
Affiliation(s)
- Rupalatha Maddala
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Tharkika Nagendran
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Gustaaf G. de Ridder
- Department of Pathology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Kevin L. Schey
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Ponugoti Vasantha Rao
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| |
Collapse
|
156
|
Machnicka B, Czogalla A, Hryniewicz-Jankowska A, Bogusławska DM, Grochowalska R, Heger E, Sikorski AF. Spectrins: a structural platform for stabilization and activation of membrane channels, receptors and transporters. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:620-34. [PMID: 23673272 DOI: 10.1016/j.bbamem.2013.05.002] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/25/2013] [Accepted: 05/06/2013] [Indexed: 12/22/2022]
Abstract
This review focuses on structure and functions of spectrin as a major component of the membrane skeleton. Recent advances on spectrin function as an interface for signal transduction mediation and a number of data concerning interaction of spectrin with membrane channels, adhesion molecules, receptors and transporters draw a picture of multifaceted protein. Here, we attempted to show the current depiction of multitask role of spectrin in cell physiology. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.
Collapse
Affiliation(s)
- Beata Machnicka
- University of Zielona Góra, Faculty of Biological Sciences, Poland
| | | | | | | | | | - Elżbieta Heger
- University of Zielona Góra, Faculty of Biological Sciences, Poland
| | | |
Collapse
|
157
|
Song YH. A Memory Molecule, Ca(2+)/Calmodulin-Dependent Protein Kinase II and Redox Stress; Key Factors for Arrhythmias in a Diseased Heart. Korean Circ J 2013; 43:145-51. [PMID: 23613689 PMCID: PMC3629238 DOI: 10.4070/kcj.2013.43.3.145] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Arrhythmias can develop in various cardiac diseases, such as ischemic heart disease, cardiomyopathy and congenital heart disease. It can also contribute to the aggravation of heart failure and sudden cardiac death. Redox stress and Ca2+ overload are thought to be the important triggering factors in the generation of arrhythmias in failing myocardium. From recent studies, it appears evident that Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays a central role in the arrhythmogenic processes in heart failure by sensing intracellular Ca2+ and redox stress, affecting individual ion channels and thereby leading to electrical instability in the heart. CaMKII, a multifunctional serine/threonine kinase, is an abundant molecule in the neuron and the heart. It has a specific property as "a memory molecule" such that the binding of calcified calmodulin (Ca2+/CaM) to the regulatory domain on CaMKII initially activates this enzyme. Further, it allows autophosphorylation of T287 or oxidation of M281/282 in the regulatory domain, resulting in sustained activation of CaMKII even after the dissociation of Ca2+/CaM. This review provides the understanding of both the structural and functional properties of CaMKII, the experimental findings of the interactions between CaMKII, redox stress and individual ion channels, and the evidences proving the potential participation of CaMKII and oxidative stress in the diverse arrhythmogenic processes in a diseased heart.
Collapse
Affiliation(s)
- Young-Hwan Song
- Department of Pediatrics, Sanggye Paik Hospital, College of Medicine, Inje University, Seoul, Korea
| |
Collapse
|
158
|
Deletion of the last five C-terminal amino acid residues of connexin43 leads to lethal ventricular arrhythmias in mice without affecting coupling via gap junction channels. Basic Res Cardiol 2013; 108:348. [PMID: 23558439 DOI: 10.1007/s00395-013-0348-y] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 03/08/2013] [Accepted: 03/25/2013] [Indexed: 10/27/2022]
Abstract
The cardiac intercalated disc harbors mechanical and electrical junctions as well as ion channel complexes mediating propagation of electrical impulses. Cardiac connexin43 (Cx43) co-localizes and interacts with several of the proteins located at intercalated discs in the ventricular myocardium. We have generated conditional Cx43D378stop mice lacking the last five C-terminal amino acid residues, representing a binding motif for zonula occludens protein-1 (ZO-1), and investigated the functional consequences of this mutation on cardiac physiology and morphology. Newborn and adult homozygous Cx43D378stop mice displayed markedly impaired and heterogeneous cardiac electrical activation properties and died from severe ventricular arrhythmias. Cx43 and ZO-1 were co-localized at intercalated discs in Cx43D378stop hearts, and the Cx43D378stop gap junction channels showed normal coupling properties. Patch clamp analyses of isolated adult Cx43D378stop cardiomyocytes revealed a significant decrease in sodium and potassium current densities. Furthermore, we also observed a significant loss of Nav1.5 protein from intercalated discs in Cx43D378stop hearts. The phenotypic lethality of the Cx43D378stop mutation was very similar to the one previously reported for adult Cx43 deficient (Cx43KO) mice. Yet, in contrast to Cx43KO mice, the Cx43 gap junction channel was still functional in the Cx43D378stop mutant. We conclude that the lethality of Cx43D378stop mice is independent of the loss of gap junctional intercellular communication, but most likely results from impaired cardiac sodium and potassium currents. The Cx43D378stop mice reveal for the first time that Cx43 dependent arrhythmias can develop by mechanisms other than impairment of gap junction channel function.
Collapse
|
159
|
Shi J, Geshi N, Takahashi S, Kiyonaka S, Ichikawa J, Hu Y, Mori Y, Ito Y, Inoue R. Molecular determinants for cardiovascular TRPC6 channel regulation by Ca2+/calmodulin-dependent kinase II. J Physiol 2013; 591:2851-66. [PMID: 23529130 DOI: 10.1113/jphysiol.2013.251249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The molecular mechanism underlying Ca(2+)/calmodulin (CaM)-dependent kinase II (CaMKII)-mediated regulation of the mouse transient receptor potential channel TRPC6 was explored by chimera, deletion and site-directed mutagenesis approaches. Induction of currents (ICCh) in TRPC6-expressing HEK293 cells by a muscarinic agonist carbachol (CCh; 100 μm) was strongly attenuated by a CaMKII-specific peptide, autocamtide-2-related inhibitory peptide (AIP; 10 μm). TRPC6/C7 chimera experiments showed that the TRPC6 C-terminal sequence is indispensable for ICCh to be sensitive to AIP-induced CaMKII inhibition. Further, deletion of a distal region (Gln(855)-Glu(877)) of the C-terminal CaM/inositol-1,4,5-trisphosphate receptor binding domain (CIRB) of TRPC6 was sufficient to abolish ICCh. Systematic alanine scanning for potential CaMKII phosphorylation sites revealed that Thr(487) was solely responsible for the activation of the TRPC6 channel by receptor stimulation. The abrogating effect of the alanine mutation of Thr(487) (T487A) was reproduced with other non-polar amino acids, namely glutamine or asparagine, while being partially rescued by phosphomimetic mutations with glutamate or aspartate. The cellular expression and distribution of TRPC6 channels did not significantly change with these mutations. Electrophysiological and immunocytochemical data with the Myc-tagged TRPC6 channel indicated that Thr(487) is most likely located at the intracellular side of the cell membrane. Overexpression of T487A caused significant reduction of endogenous TRPC6-like current induced by Arg(8)-vasopressin in A7r5 aortic myocytes. Based on these results, we propose that the optimal spatial arrangement of a C-terminal domain (presumably the distal CIRB region) around a single CaMKII phosphorylation site Thr(487) may be essential for CaMKII-mediated regulation of TRPC6 channels. This mechanism may be of physiological significance in a native environment such as in vascular smooth muscle cells.
Collapse
Affiliation(s)
- Juan Shi
- Department of Physiology, Graduate School of Medical Sciences, Fukuoka University, Nanakuma 7-45-1, Johnan-ku, Fukuoka 814-0180, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
160
|
Abstract
SIGNIFICANCE In heart failure (HF), contractile dysfunction and arrhythmias result from disturbed intracellular Ca handling. Activated stress kinases like cAMP-dependent protein kinase A (PKA), protein kinase C (PKC), and Ca/calmodulin-dependent protein kinase II (CaMKII), which are known to influence many Ca-regulatory proteins, are mechanistically involved. RECENT ADVANCES Beside classical activation pathways, it is becoming increasingly evident that reactive oxygen species (ROS) can directly oxidize these kinases, leading to alternative activation. Since HF is associated with increased ROS generation, ROS-activated serine/threonine kinases may play a crucial role in the disturbance of cellular Ca homeostasis. Many of the previously described ROS effects on ion channels and transporters are possibly mediated by these stress kinases. For instance, ROS have been shown to oxidize and activate CaMKII, thereby increasing Na influx through voltage-gated Na channels, which can lead to intracellular Na accumulation and action potential prolongation. Consequently, Ca entry via activated NCX is favored, which together with ROS-induced dysfunction of the sarcoplasmic reticulum can lead to dramatic intracellular Ca accumulation, diminished contractility, and arrhythmias. CRITICAL ISSUES While low amounts of ROS may regulate kinase activity, excessive uncontrolled ROS production may lead to direct redox modification of Ca handling proteins. Therefore, depending on the source and amount of ROS generated, ROS could have very different effects on Ca-handling proteins. FUTURE DIRECTIONS The discrimination between fine-tuned ROS signaling and unspecific ROS damage may be crucial for the understanding of heart failure development and important for the investigation of targeted treatment strategies.
Collapse
Affiliation(s)
- Stefan Wagner
- Abt. Kardiologie und Pneumologie/Herzzentrum, Deutsches Zentrum für Herzkreislaufforschung, Georg-August-Universität, Göttingen, Germany
| | | | | | | |
Collapse
|
161
|
Maier LS, Sossalla S. The late Na current as a therapeutic target: where are we? J Mol Cell Cardiol 2013; 61:44-50. [PMID: 23500390 DOI: 10.1016/j.yjmcc.2013.03.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 02/26/2013] [Accepted: 03/04/2013] [Indexed: 12/19/2022]
Abstract
In this article we review the late Na current which functionally can be measured using patch-clamp electrophysiology (INa,late). This current is largely enhanced under pathological myocardial conditions such as ischemia and heart failure. In addition, INa,late can cause systolic and diastolic contractile dysfunction via a Na-dependent Ca-overload of the myocyte. Moreover, INa,late plays a crucial role as ventricular and atrial proarrhythmic substrate in myocardial pathology by changing cellular electrophysiology. We summarize recent experimental and clinical studies that investigate therapeutic inhibition of this current and discuss the significance of the available data and try to answer not only the question, where we currently are but also where we may go in the near future. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
Collapse
Affiliation(s)
- Lars S Maier
- Abt. Kardiologie und Pneumologie/Herzzentrum, Deutsches Zentrum für Herzkreislaufforschung, Georg-August-Universität, Göttingen, Germany.
| | | |
Collapse
|
162
|
Noorman M, Hakim S, Kessler E, Groeneweg J, Cox MGPJ, Asimaki A, van Rijen HVM, van Stuijvenberg L, Chkourko H, van der Heyden MAG, Vos MA, de Jonge N, van der Smagt JJ, Dooijes D, Vink A, de Weger RA, Varro A, de Bakker JMT, Saffitz JE, Hund TJ, Mohler PJ, Delmar M, Hauer RNW, van Veen TAB. Remodeling of the cardiac sodium channel, connexin43, and plakoglobin at the intercalated disk in patients with arrhythmogenic cardiomyopathy. Heart Rhythm 2013; 10:412-9. [PMID: 23178689 PMCID: PMC3608196 DOI: 10.1016/j.hrthm.2012.11.018] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND Arrhythmogenic cardiomyopathy (AC) is closely associated with desmosomal mutations in a majority of patients. Arrhythmogenesis in patients with AC is likely related to remodeling of cardiac gap junctions and increased levels of fibrosis. Recently, using experimental models, we also identified sodium channel dysfunction secondary to desmosomal dysfunction. OBJECTIVE To assess the immunoreactive signal levels of the sodium channel protein NaV1.5, as well as connexin43 (Cx43) and plakoglobin (PKG), in myocardial specimens obtained from patients with AC. METHODS Left and right ventricular free wall postmortem material was obtained from 5 patients with AC and 5 controls matched for age and sex. Right ventricular septal biopsies were taken from another 15 patients with AC. All patients fulfilled the 2010 revised Task Force Criteria for the diagnosis of AC. Immunohistochemical analyses were performed using antibodies against Cx43, PKG, NaV1.5, plakophilin-2, and N-cadherin. RESULTS N-cadherin and desmoplakin immunoreactive signals and distribution were normal in patients with AC compared to controls. Plakophilin-2 signals were unaffected unless a plakophilin-2 mutation predicting haploinsufficiency was present. Distribution was unchanged compared to that in controls. Immunoreactive signal levels of PKG, Cx43, and NaV1.5 were disturbed in 74%, 70%, and 65% of the patients, respectively. CONCLUSIONS A reduced immunoreactive signal of PKG, Cx43, and NaV1.5 at the intercalated disks can be observed in a large majority of the patients. Decreased levels of Nav1.5 might contribute to arrhythmia vulnerability and, in the future, potentially could serve as a new clinically relevant tool for risk assessment strategies.
Collapse
Affiliation(s)
- Maartje Noorman
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands
| | - Sara Hakim
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
| | - Elise Kessler
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
| | - Judith Groeneweg
- Department of Cardiology, University Medical Center Utrecht, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands
| | - Moniek GPJ Cox
- Department of Cardiology, University Medical Center Utrecht, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands
| | - Angeliki Asimaki
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, USA
| | - Harold VM van Rijen
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
| | | | - Halina Chkourko
- The Leon H Charney Division of Cardiology, New York University School of Medicine, New York, NY, USA
| | | | - Marc A Vos
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
| | - Nicolaas de Jonge
- Department of Cardiology, University Medical Center Utrecht, The Netherlands
| | | | - Dennis Dooijes
- Department of Genetics, University Medical Center Utrecht, The Netherlands
| | - Aryan Vink
- Department of Pathology, University Medical Center Utrecht, The Netherlands
| | - Roel A de Weger
- Department of Pathology, University Medical Center Utrecht, The Netherlands
| | - Andras Varro
- Department of Pharmacology & Pharmacotherapy, Faculty of Medicine, University of Szeged, Hungary
| | | | - Jeffrey E Saffitz
- Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, USA
| | - Thomas J Hund
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Engineering, Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210
| | - Peter J Mohler
- The Dorothy M. Davis Heart and Lung Research Institute, Department of Internal Medicine, Division of Cardiovascular Medicine; Department of Physiology & Cell Biology, The Ohio State University Medical Center, Columbus, OH 43210
| | - Mario Delmar
- The Leon H Charney Division of Cardiology, New York University School of Medicine, New York, NY, USA
| | - Richard NW Hauer
- Department of Cardiology, University Medical Center Utrecht, The Netherlands
- Interuniversity Cardiology Institute of the Netherlands
| | - Toon AB van Veen
- Department of Medical Physiology, University Medical Center Utrecht, The Netherlands
| |
Collapse
|
163
|
Rokita AG, Anderson ME. New therapeutic targets in cardiology: arrhythmias and Ca2+/calmodulin-dependent kinase II (CaMKII). Circulation 2013; 126:2125-39. [PMID: 23091085 DOI: 10.1161/circulationaha.112.124990] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Adam G Rokita
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
| | | |
Collapse
|
164
|
|
165
|
Bennett V, Lorenzo DN. Spectrin- and Ankyrin-Based Membrane Domains and the Evolution of Vertebrates. CURRENT TOPICS IN MEMBRANES 2013; 72:1-37. [DOI: 10.1016/b978-0-12-417027-8.00001-5] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
166
|
DeGrande S, Nixon D, Koval O, Curran JW, Wright P, Wang Q, Kashef F, Chiang D, Li N, Wehrens XHT, Anderson ME, Hund TJ, Mohler PJ. CaMKII inhibition rescues proarrhythmic phenotypes in the model of human ankyrin-B syndrome. Heart Rhythm 2012; 9:2034-41. [PMID: 23059182 PMCID: PMC3630478 DOI: 10.1016/j.hrthm.2012.08.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND Cardiovascular disease is a leading cause of death worldwide. Arrhythmias are associated with significant morbidity and mortality related to cardiovascular disease. Recent work illustrates that many cardiac arrhythmias are initiated by a pathologic imbalance between kinase and phosphatase activities in excitable cardiomyocytes. OBJECTIVE To test the relationship between myocyte kinase/phosphatase imbalance and cellular and whole animal arrhythmia phenotypes associated with ankyrin-B cardiac syndrome. METHODS By using a combination of biochemical, electrophysiological, and in vivo approaches, we tested the ability of calcium/calmodulin-dependent kinase (CaMKII) inhibition to rescue imbalance in kinase/phosphatase pathways associated with human ankyrin-B-associated cardiac arrhythmia. RESULTS The cardiac ryanodine receptor (RyR(2)), a validated target of kinase/phosphatase regulation in myocytes, displays abnormal CaMKII-dependent phosphorylation (pS2814 hyperphosphorylation) in ankyrin-B(+/-) heart. Notably, RyR(2) dysregulation is rescued in myocytes from ankyrin-B(+/-) mice overexpressing a potent CaMKII-inhibitory peptide (AC3I), and aberrant RyR(2) open probability observed in ankyrin-B(+/-) hearts is normalized by treatment with the CaMKII inhibitor KN-93. CaMKII inhibition is sufficient to rescue abnormalities in ankyrin-B(+/-) myocyte electrical dysfunction including cellular afterdepolarizations, and significantly blunts whole animal cardiac arrhythmias and sudden death in response to elevated sympathetic tone. CONCLUSIONS These findings illustrate the complexity of the molecular components involved in human arrhythmia and define regulatory elements of the ankyrin-B pathway in pathophysiology. Furthermore, the findings illustrate the potential impact of CaMKII inhibition in the treatment of a congenital form of human cardiac arrhythmia.
Collapse
Affiliation(s)
- Sean DeGrande
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
167
|
Marionneau C, Lichti CF, Lindenbaum P, Charpentier F, Nerbonne JM, Townsend RR, Mérot J. Mass spectrometry-based identification of native cardiac Nav1.5 channel α subunit phosphorylation sites. J Proteome Res 2012; 11:5994-6007. [PMID: 23092124 DOI: 10.1021/pr300702c] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cardiac voltage-gated Na+ (Nav) channels are key determinants of action potential waveforms, refractoriness and propagation, and Nav1.5 is the main Nav pore-forming (α) subunit in the mammalian heart. Although direct phosphorylation of the Nav1.5 protein has been suggested to modulate various aspects of Nav channel physiology and pathophysiology, native Nav1.5 phosphorylation sites have not been identified. In the experiments here, a mass spectrometry (MS)-based proteomic approach was developed to identify native Nav1.5 phosphorylation sites directly. Using an anti-NavPAN antibody, Nav channel complexes were immunoprecipitated from adult mouse cardiac ventricles. The MS analyses revealed that this antibody immunoprecipitates several Nav α subunits in addition to Nav1.5, as well as several previously identified Nav channel associated/regulatory proteins. Label-free comparative and data-driven phosphoproteomic analyses of purified cardiac Nav1.5 protein identified 11 phosphorylation sites, 8 of which are novel. All the phosphorylation sites identified except one in the N-terminus are in the first intracellular linker loop, suggesting critical roles for this region in phosphorylation-dependent cardiac Nav channel regulation. Interestingly, commonly used prediction algorithms did not reliably predict these newly identified in situ phosphorylation sites. Taken together, the results presented provide the first in situ map of basal phosphorylation sites on the mouse cardiac Nav1.5 α subunit.
Collapse
|
168
|
He M, Jenkins P, Bennett V. Cysteine 70 of ankyrin-G is S-palmitoylated and is required for function of ankyrin-G in membrane domain assembly. J Biol Chem 2012; 287:43995-4005. [PMID: 23129772 PMCID: PMC3527982 DOI: 10.1074/jbc.m112.417501] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ankyrin-G (AnkG) coordinates protein composition of diverse membrane domains, including epithelial lateral membranes and neuronal axon initial segments. However, how AnkG itself localizes to these membrane domains is not understood. We report that AnkG remains on the plasma membrane in Madin-Darby canine kidney (MDCK) cells grown in low calcium, although these cells lack apical-basal polarity and exhibit loss of plasma membrane association of AnkG partners, E-cadherin and β2-spectrin. We subsequently demonstrate using mutagenesis and mass spectrometry that AnkG is S-palmitoylated exclusively at Cys-70, which is located in a loop of the first ankyrin repeat and is conserved in the vertebrate ankyrin family. Moreover, C70A mutation abolishes membrane association of 190-kDa AnkG in MDCK cells grown in low calcium. C70A 190-kDa AnkG fails to restore biogenesis of epithelial lateral membranes in MDCK cells depleted of endogenous AnkG. In addition, C70A 270-kDa AnkG fails to cluster at the axon initial segment of AnkG-depleted cultured hippocampal neurons and fails to recruit neurofascin as well as voltage-gated sodium channels. These effects of C70A mutation combined with evidence for its S-palmitoylation are consistent with a requirement of palmitoylation for targeting and function of AnkG in membrane domain biogenesis at epithelial lateral membranes and neuronal axon initial segments.
Collapse
Affiliation(s)
- Meng He
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | |
Collapse
|
169
|
Shy D, Gillet L, Abriel H. Cardiac sodium channel NaV1.5 distribution in myocytes via interacting proteins: the multiple pool model. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:886-94. [PMID: 23123192 DOI: 10.1016/j.bbamcr.2012.10.026] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/18/2012] [Accepted: 10/19/2012] [Indexed: 11/16/2022]
Abstract
The cardiac sodium current (INa) is responsible for the rapid depolarization of cardiac cells, thus allowing for their contraction. It is also involved in regulating the duration of the cardiac action potential (AP) and propagation of the impulse throughout the myocardium. Cardiac INa is generated by the voltage-gated Na(+) channel, NaV1.5, a 2016-residue protein which forms the pore of the channel. Over the past years, hundreds of mutations in SCN5A, the human gene coding for NaV1.5, have been linked to many cardiac electrical disorders, including the congenital and acquired long QT syndrome, Brugada syndrome, conduction slowing, sick sinus syndrome, atrial fibrillation, and dilated cardiomyopathy. Similar to many membrane proteins, NaV1.5 has been found to be regulated by several interacting proteins. In some cases, these different proteins, which reside in distinct membrane compartments (i.e. lateral membrane vs. intercalated disks), have been shown to interact with the same regulatory domain of NaV1.5, thus suggesting that several pools of NaV1.5 channels may co-exist in cardiac cells. The aim of this review article is to summarize the recent works that demonstrate its interaction with regulatory proteins and illustrate the model that the sodium channel NaV1.5 resides in distinct and different pools in cardiac cells. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.
Collapse
Affiliation(s)
- Diana Shy
- Department of Clinical Research, University of Bern, Bern, Switzerland
| | | | | |
Collapse
|
170
|
Koval OM, Snyder JS, Wolf RM, Pavlovicz RE, Glynn P, Curran J, Leymaster ND, Dun W, Wright PJ, Cardona N, Qian L, Mitchell CC, Boyden PA, Binkley PF, Li C, Anderson ME, Mohler PJ, Hund TJ. Ca2+/calmodulin-dependent protein kinase II-based regulation of voltage-gated Na+ channel in cardiac disease. Circulation 2012; 126:2084-94. [PMID: 23008441 DOI: 10.1161/circulationaha.112.105320] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Human gene variants affecting ion channel biophysical activity and/or membrane localization are linked to potentially fatal cardiac arrhythmias. However, the mechanism for many human arrhythmia variants remains undefined despite more than a decade of investigation. Posttranslational modulation of membrane proteins is essential for normal cardiac function. Importantly, aberrant myocyte signaling has been linked to defects in cardiac ion channel posttranslational modifications and disease. We recently identified a novel pathway for posttranslational regulation of the primary cardiac voltage-gated Na(+) channel (Na(v)1.5) by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). However, a role for this pathway in cardiac disease has not been evaluated. METHODS AND RESULTS We evaluated the role of CaMKII-dependent phosphorylation in human genetic and acquired disease. We report an unexpected link between a short motif in the Na(v)1.5 DI-DII loop, recently shown to be critical for CaMKII-dependent phosphorylation, and Na(v)1.5 function in monogenic arrhythmia and common heart disease. Experiments in heterologous cells and primary ventricular cardiomyocytes demonstrate that the human arrhythmia susceptibility variants (A572D and Q573E) alter CaMKII-dependent regulation of Na(v)1.5, resulting in abnormal channel activity and cell excitability. In silico analysis reveals that these variants functionally mimic the phosphorylated channel, resulting in increased susceptibility to arrhythmia-triggering afterdepolarizations. Finally, we report that this same motif is aberrantly regulated in a large-animal model of acquired heart disease and in failing human myocardium. CONCLUSIONS We identify the mechanism for 2 human arrhythmia variants that affect Na(v)1.5 channel activity through direct effects on channel posttranslational modification. We propose that the CaMKII phosphorylation motif in the Na(v)1.5 DI-DII cytoplasmic loop is a critical nodal point for proarrhythmic changes to Na(v)1.5 in congenital and acquired cardiac disease.
Collapse
Affiliation(s)
- Olha M Koval
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Medical Center, 473 W 12th Ave, Columbus, OH 43210, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
171
|
Swaminathan PD, Purohit A, Hund TJ, Anderson ME. Calmodulin-dependent protein kinase II: linking heart failure and arrhythmias. Circ Res 2012; 110:1661-77. [PMID: 22679140 DOI: 10.1161/circresaha.111.243956] [Citation(s) in RCA: 215] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Understanding relationships between heart failure and arrhythmias, important causes of suffering and sudden death, remains an unmet goal for biomedical researchers and physicians. Evidence assembled over the past decade supports a view that activation of the multifunctional Ca(2+) and calmodulin-dependent protein kinase II (CaMKII) favors myocardial dysfunction and cell membrane electrical instability. CaMKII activation follows increases in intracellular Ca(2+) or oxidation, upstream signals with the capacity to transition CaMKII into a Ca(2+) and calmodulin-independent constitutively active enzyme. Constitutively active CaMKII appears poised to participate in disease pathways by catalyzing the phosphorylation of classes of protein targets important for excitation-contraction coupling and cell survival, including ion channels and Ca(2+) homeostatic proteins, and transcription factors that drive hypertrophic and inflammatory gene expression. This rich diversity of downstream targets helps to explain the potential for CaMKII to simultaneously affect mechanical and electrical properties of heart muscle cells. Proof-of-concept studies from a growing number of investigators show that CaMKII inhibition is beneficial for improving myocardial performance and for reducing arrhythmias. We review the molecular physiology of CaMKII and discuss CaMKII actions at key cellular targets and results of animal models of myocardial hypertrophy, dysfunction, and arrhythmias that suggest CaMKII inhibition may benefit myocardial function while reducing arrhythmias.
Collapse
Affiliation(s)
- Paari Dominic Swaminathan
- Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | | | | | | |
Collapse
|
172
|
Kashef F, Li J, Wright P, Snyder J, Suliman F, Kilic A, Higgins RSD, Anderson ME, Binkley PF, Hund TJ, Mohler PJ. Ankyrin-B protein in heart failure: identification of a new component of metazoan cardioprotection. J Biol Chem 2012; 287:30268-81. [PMID: 22778271 DOI: 10.1074/jbc.m112.368415] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ankyrins (ankyrin-R, -B, and -G) are adapter proteins linked with defects in metazoan physiology. Ankyrin-B (encoded by ANK2) loss-of-function mutations are directly associated with human cardiovascular phenotypes including sinus node disease, atrial fibrillation, ventricular tachycardia, and sudden cardiac death. Despite the link between ankyrin-B dysfunction and monogenic disease, there are no data linking ankyrin-B regulation with common forms of human heart failure. Here, we report that ankyrin-B levels are altered in both ischemic and non-ischemic human heart failure. Mechanistically, we demonstrate that cardiac ankyrin-B levels are tightly regulated downstream of reactive oxygen species, intracellular calcium, and the calcium-dependent protease calpain, all hallmarks of human myocardial injury and heart failure. Surprisingly, β(II)-spectrin, previously thought to mediate ankyrin-dependent modulation in the nervous system and heart, is not coordinately regulated with ankyrin-B or its downstream partners. Finally, our data implicate ankyrin-B expression as required for vertebrate myocardial protection as hearts deficient in ankyrin-B show increased cardiac damage and impaired function relative to wild-type mouse hearts following ischemia reperfusion. In summary, our findings provide the data of ankyrin-B regulation in human heart failure, provide insight into candidate pathways for ankyrin-B regulation in acquired human cardiovascular disease, and surprisingly, implicate ankyrin-B as a molecular component for cardioprotection following ischemia.
Collapse
Affiliation(s)
- Farshid Kashef
- Dorothy M. Davis Heart and Lung Research Institute, Columbus, OH 43210, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
173
|
Cerrone M, Noorman M, Lin X, Chkourko H, Liang FX, van der Nagel R, Hund T, Birchmeier W, Mohler P, van Veen TA, van Rijen HV, Delmar M. Sodium current deficit and arrhythmogenesis in a murine model of plakophilin-2 haploinsufficiency. Cardiovasc Res 2012; 95:460-8. [PMID: 22764151 DOI: 10.1093/cvr/cvs218] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AIMS The shRNA-mediated loss of expression of the desmosomal protein plakophilin-2 leads to sodium current (I(Na)) dysfunction. Whether pkp2 gene haploinsufficiency leads to I(Na) deficit in vivo remains undefined. Mutations in pkp2 are detected in arrhythmogenic right ventricular cardiomyopathy (ARVC). Ventricular fibrillation and sudden death often occur in the 'concealed phase' of the disease, prior to overt structural damage. The mechanisms responsible for these arrhythmias remain poorly understood. We sought to characterize the morphology, histology, and ultrastructural features of PKP2-heterozygous-null (PKP2-Hz) murine hearts and explore the relation between PKP2 abundance, I(Na) function, and cardiac electrical synchrony. METHODS AND RESULTS Hearts of PKP2-Hz mice were characterized by multiple methods. We observed ultrastructural but not histological or gross anatomical differences in PKP2-Hz hearts compared with wild-type (WT) littermates. Yet, in myocytes, decreased amplitude and a shift in gating and kinetics of I(Na) were observed. To further unmask I(Na) deficiency, we exposed myocytes, Langendorff-perfused hearts, and anaesthetized animals to a pharmacological challenge (flecainide). In PKP2-Hz hearts, the extent of flecainide-induced I(Na) block, impaired ventricular conduction, and altered electrocardiographic parameters were larger than controls. Flecainide provoked ventricular arrhythmias and death in PKP2-Hz animals, but not in the WT. CONCLUSIONS PKP2 haploinsufficiency leads to I(Na) deficit in murine hearts. Our data support the notion of a cross-talk between desmosome and sodium channel complex. They also suggest that I(Na) dysfunction may contribute to generation and/or maintenance of arrhythmias in PKP2-deficient hearts. Whether pharmacological challenges could help unveil arrhythmia risk in patients with mutations or variants in PKP2 remains undefined.
Collapse
Affiliation(s)
- Marina Cerrone
- Division of Cardiology, New York University School of Medicine, New York, NY, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
174
|
Cai Y, Zhu HX, Li JM, Luo XG, Patrylo PR, Rose GM, Streeter J, Hayes R, Wang KKW, Yan XX, Jeromin A. Age-related intraneuronal elevation of αII-spectrin breakdown product SBDP120 in rodent forebrain accelerates in 3×Tg-AD mice. PLoS One 2012; 7:e37599. [PMID: 22723836 PMCID: PMC3377681 DOI: 10.1371/journal.pone.0037599] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 04/23/2012] [Indexed: 11/24/2022] Open
Abstract
Spectrins line the intracellular surface of plasmalemma and play a critical role in supporting cytoskeletal stability and flexibility. Spectrins can be proteolytically degraded by calpains and caspases, yielding breakdown products (SBDPs) of various molecular sizes, with SBDP120 being largely derived from caspase-3 cleavage. SBDPs are putative biomarkers for traumatic brain injury. The levels of SBDPs also elevate in the brain during aging and perhaps in Alzheimer’s disease (AD), although the cellular basis for this change is currently unclear. Here we examined age-related SBDP120 alteration in forebrain neurons in rats and in the triple transgenic model of AD (3×Tg-AD) relative to non-transgenic controls. SBDP120 immunoreactivity (IR) was found in cortical neuronal somata in aged rats, and was prominent in the proximal dendrites of the olfactory bulb mitral cells. Western blot and densitometric analyses in wild-type mice revealed an age-related elevation of intraneuronal SBDP120 in the forebrain which was more robust in their 3×Tg-AD counterparts. The intraneuronal SBDP120 occurrence was not spatiotemporally correlated with transgenic amyloid precursor protein (APP) expression, β-amyloid plaque development, or phosphorylated tau expression over various forebrain regions or lamina. No microscopically detectable in situ activated caspase-3 was found in the nuclei of SBDP120-containing neurons. The present study demonstrates the age-dependent intraneuronal presence of an αII-spectrin cleavage fragment in mammalian forebrain which is exacerbated in a transgenic model of AD. This novel neuronal alteration indicates that impairments in membrane protein metabolism, possibly due to neuronal calcium mishandling and/or enhancement of calcium sensitive proteolysis, occur during aging and in transgenic AD mice.
Collapse
Affiliation(s)
- Yan Cai
- Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan, China
| | - Hai-Xia Zhu
- Department of Neurology, The Third Xiangya Hospital, Changsha, Hunan, China
| | - Jian-Ming Li
- Neuroscience Research Center, Changsha Medical University, Changsha, Hunan, China
| | - Xue-Gang Luo
- Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan, China
| | - Peter R. Patrylo
- Departments of Anatomy & Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois, United States of America
- Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University School of Medicine, Carbondale, Illinois, United States of America
| | - Gregory M. Rose
- Departments of Anatomy & Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois, United States of America
- Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University School of Medicine, Carbondale, Illinois, United States of America
| | | | - Ron Hayes
- Banyan Biomarkers, Alachua, Florida, United States of America
| | | | - Xiao-Xin Yan
- Department of Anatomy and Neurobiology, Central South University Xiangya Medical School, Changsha, Hunan, China
- Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University School of Medicine, Carbondale, Illinois, United States of America
- * E-mail: (XXY); (AJ)
| | - Andreas Jeromin
- Banyan Biomarkers, Alachua, Florida, United States of America
- * E-mail: (XXY); (AJ)
| |
Collapse
|
175
|
Smith S, Curran J, Hund TJ, Mohler PJ. Defects in cytoskeletal signaling pathways, arrhythmia, and sudden cardiac death. Front Physiol 2012; 3:122. [PMID: 22586405 PMCID: PMC3343379 DOI: 10.3389/fphys.2012.00122] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Accepted: 04/12/2012] [Indexed: 11/25/2022] Open
Abstract
Ankyrin polypeptides are cellular adapter proteins that tether integral membrane proteins to the cytoskeleton in a host of human organs. Initially identified as integral components of the cytoskeleton in erythrocytes, a recent explosion in ankyrin research has demonstrated that these proteins play prominent roles in cytoskeletal signaling pathways and membrane protein trafficking/regulation in a variety of excitable and non-excitable cells including heart and brain. Importantly, ankyrin research has translated from bench to bedside with the discovery of human gene variants associated with ventricular arrhythmias that alter ankyrin–based pathways. Ankyrin polypeptides have also been found to play an instrumental role in various forms of sinus node disease and atrial fibrillation (AF). Mouse models of ankyrin-deficiency have played fundamental roles in the translation of ankyrin-based research to new clinical understanding of human sinus node disease, AF, and ventricular tachycardia.
Collapse
Affiliation(s)
- Sakima Smith
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Medical Center Columbus, OH, USA
| | | | | | | |
Collapse
|
176
|
Ashpole NM, Herren AW, Ginsburg KS, Brogan JD, Johnson DE, Cummins TR, Bers DM, Hudmon A. Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates cardiac sodium channel NaV1.5 gating by multiple phosphorylation sites. J Biol Chem 2012; 287:19856-69. [PMID: 22514276 DOI: 10.1074/jbc.m111.322537] [Citation(s) in RCA: 128] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The cardiac Na(+) channel Na(V)1.5 current (I(Na)) is critical to cardiac excitability, and altered I(Na) gating has been implicated in genetic and acquired arrhythmias. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is up-regulated in heart failure and has been shown to cause I(Na) gating changes that mimic those induced by a point mutation in humans that is associated with combined long QT and Brugada syndromes. We sought to identify the site(s) on Na(V)1.5 that mediate(s) the CaMKII-induced alterations in I(Na) gating. We analyzed both CaMKII binding and CaMKII-dependent phosphorylation of the intracellularly accessible regions of Na(V)1.5 using a series of GST fusion constructs, immobilized peptide arrays, and soluble peptides. A stable interaction between δ(C)-CaMKII and the intracellular loop between domains 1 and 2 of Na(V)1.5 was observed. This region was also phosphorylated by δ(C)-CaMKII, specifically at the Ser-516 and Thr-594 sites. Wild-type (WT) and phosphomutant hNa(V)1.5 were co-expressed with GFP-δ(C)-CaMKII in HEK293 cells, and I(Na) was recorded. As observed in myocytes, CaMKII shifted WT I(Na) availability to a more negative membrane potential and enhanced accumulation of I(Na) into an intermediate inactivated state, but these effects were abolished by mutating either of these sites to non-phosphorylatable Ala residues. Mutation of these sites to phosphomimetic Glu residues negatively shifted I(Na) availability without the need for CaMKII. CaMKII-dependent phosphorylation of Na(V)1.5 at multiple sites (including Thr-594 and Ser-516) appears to be required to evoke loss-of-function changes in gating that could contribute to acquired Brugada syndrome-like effects in heart failure.
Collapse
Affiliation(s)
- Nicole M Ashpole
- Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | | | | | | | | | | | | | | |
Collapse
|
177
|
Abstract
The action potential generally begins in the axon initial segment (AIS), a principle confirmed by 60 years of research; however, the most recent advances have shown that a very rich biology underlies this simple observation. The AIS has a remarkably complex molecular composition, with a wide variety of ion channels and attendant mechanisms for channel localization, and may feature membrane domains each with distinct roles in excitation. Its function may be regulated in the short term through the action of neurotransmitters, in the long term through activity- and Ca(2+)-dependent processes. Thus, the AIS is not merely the beginning of the axon, but rather a key site in the control of neuronal excitability.
Collapse
Affiliation(s)
- Kevin J Bender
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239, USA.
| | | |
Collapse
|
178
|
Buffington SA, Sobotzik JM, Schultz C, Rasband MN. IκBα is not required for axon initial segment assembly. Mol Cell Neurosci 2012; 50:1-9. [PMID: 22445657 DOI: 10.1016/j.mcn.2012.03.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 02/29/2012] [Accepted: 03/06/2012] [Indexed: 11/26/2022] Open
Abstract
The inhibitor of NF-κB alpha (IκBα) protein is an important regulator of the transcription factor NF-κB. In neurons, IκBα has been shown to play a role in neurite outgrowth and cell survival. Recently, a phosphorylated form of IκBα (pIκBα Ser32/36) was reported to be highly enriched at the axon initial segment (AIS) and was proposed to function upstream of ankyrinG in AIS assembly, including ion channel recruitment. However, we report here that the AIS clustering of ankyrinG and Na(+) channels in the brains of IκBα knockout (Nfkbia(-/-)) mice is comparable to that in wild-type littermates. Furthermore, we found that multiple phospho-specific antibodies against pIκBα Ser32/36 non-specifically label AIS in Nfkbia(-/-) cortex and AIS in dissociated Nfkbia(-/-) hippocampal neurons. With the exception of ankyrinG, shRNA-mediated knockdown of known AIS proteins in cultured hippocampal neurons did not eliminate the AIS labeling with pIκBα antibodies. Instead, the pIκBα antibodies cross-react with a phosphorylated epitope of a protein associated with the microtubule-based AIS cytoskeleton that is not integrated into the AIS membrane complex organized by ankyrinG. Our results indicate that pIκBα is neither enriched at the AIS nor required for AIS assembly.
Collapse
Affiliation(s)
- Shelly A Buffington
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | |
Collapse
|
179
|
Trenor B, Cardona K, Gomez JF, Rajamani S, Ferrero JM, Belardinelli L, Saiz J. Simulation and mechanistic investigation of the arrhythmogenic role of the late sodium current in human heart failure. PLoS One 2012; 7:e32659. [PMID: 22427860 PMCID: PMC3299678 DOI: 10.1371/journal.pone.0032659] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 02/02/2012] [Indexed: 11/18/2022] Open
Abstract
Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na+ current (INaL) is relevant and is currently under investigation. In this study we examined the role of INaL in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi et al. model for human ventricular action potential that incorporates the formulation of INaL. A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human INaL and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for INaL in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca2+ transient. A mechanistic investigation of intracellular Na+ accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na+/K+ pump, the Na+/Ca2+ exchanger and INaL. The results of the simulations also showed that in failing myocytes, the enhancement of INaL increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the INaL prolong APD and alter Ca2+ transient facilitating the development of early afterdepolarizations. An enhanced INaL appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca2+]i homeostasis of failing myocytes.
Collapse
Affiliation(s)
- Beatriz Trenor
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano, Universitat Politècnica de València, Valencia, Spain.
| | | | | | | | | | | | | |
Collapse
|
180
|
Pinder JC, Taylor-Harris PM, Bennett PM, Carter E, Hayes NVL, King MDA, Holt MR, Maggs AM, Gascard P, Baines AJ. Isoforms of protein 4.1 are differentially distributed in heart muscle cells: relation of 4.1R and 4.1G to components of the Ca2+ homeostasis system. Exp Cell Res 2012; 318:1467-79. [PMID: 22429617 DOI: 10.1016/j.yexcr.2012.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 03/01/2012] [Accepted: 03/02/2012] [Indexed: 11/30/2022]
Abstract
The 4.1 proteins are cytoskeletal adaptor proteins that are linked to the control of mechanical stability of certain membranes and to the cellular accumulation and cell surface display of diverse transmembrane proteins. One of the four mammalian 4.1 proteins, 4.1R (80 kDa/120 kDa isoforms), has recently been shown to be required for the normal operation of several ion transporters in the heart (Stagg MA et al. Circ Res, 2008; 103: 855-863). The other three (4.1G, 4.1N and 4.1B) are largely uncharacterised in the heart. Here, we use specific antibodies to characterise their expression, distribution and novel activities in the left ventricle. We detected 4.1R, 4.1G and 4.1N by immunofluorescence and immunoblotting, but not 4.1B. Only one splice variant of 4.1N and 4.1G was seen whereas there are several forms of 4.1R. 4.1N, like 4.1R, was present in intercalated discs, but unlike 4.1R, it was not localised at the lateral plasma membrane. Both 4.1R and 4.1N were in internal structures that, at the level of resolution of the light microscope, were close to the Z-disc (possibly T-tubules). 4.1G was also in intracellular structures, some of which were coincident with sarcoplasmic reticulum. 4.1G existed in an immunoprecipitable complex with spectrin and SERCA2. 80 kDa 4.1R was present in subcellular fractions enriched in intercalated discs, in a complex resistant to solubilization under non-denaturing conditions. At the intercalated disc 4.1R does not colocalise with the adherens junction protein, β-catenin, but does overlap with the other plasma membrane signalling proteins, the Na/K-ATPase and the Na/Ca exchanger NCX1. We conclude that isoforms of 4.1 proteins are differentially compartmentalised in the heart, and that they form specific complexes with proteins central to cardiomyocyte Ca(2+) metabolism.
Collapse
Affiliation(s)
- Jennifer C Pinder
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
181
|
Alekseev AE, Reyes S, Selivanov VA, Dzeja PP, Terzic A. Compartmentation of membrane processes and nucleotide dynamics in diffusion-restricted cardiac cell microenvironment. J Mol Cell Cardiol 2012; 52:401-9. [PMID: 21704043 PMCID: PMC3264845 DOI: 10.1016/j.yjmcc.2011.06.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 01/08/2023]
Abstract
Orchestrated excitation-contraction coupling in heart muscle requires adequate spatial arrangement of systems responsible for ion movement and metabolite turnover. Co-localization of regulatory and transporting proteins into macromolecular complexes within an environment of microanatomical cell components raises intracellular diffusion barriers that hamper the mobility of metabolites and signaling molecules. Compared to substrate diffusion in the cytosol, diffusional restrictions underneath the sarcolemma are much larger and could impede ion and nucleotide movement by a factor of 10(3)-10(5). Diffusion barriers thus seclude metabolites within the submembrane space enabling rapid and vectorial effector targeting, yet hinder energy supply from the bulk cytosolic space implicating the necessity for a shunting transfer mechanism. Here, we address principles of membrane protein compartmentation, phosphotransfer enzyme-facilitated interdomain energy transfer, and nucleotide signal dynamics at the subsarcolemma-cytosol interface. This article is part of a Special Issue entitled "Local Signaling in Myocytes".
Collapse
Affiliation(s)
- Alexey E. Alekseev
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Santiago Reyes
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Vitaly A. Selivanov
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, and IBUB Barcelona, Gran Via de les Corts Catalanes 585, 08007 Barcelona, Spain
| | - Petras P. Dzeja
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| |
Collapse
|
182
|
Abstract
The axon initial segment (AIS) is a highly specialized neuronal subregion that is the site of action potential initiation and the boundary between axonal and somatodendritic compartments. In recent years, our understanding of the molecular structure of the AIS, its maturation, and its multiple fundamental roles in neuronal function has seen major advances. We are beginning to appreciate that the AIS is dynamically regulated, both over short timescales via adaptations in ion channel function, and long timescales via activity-dependent structural reorganization. Here, we review results from this emerging field highlighting how structural and functional plasticity relate to the development of the initial segment, and to neuronal disorders linked to AIS dysfunction.
Collapse
|
183
|
Maier LS. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) in the Heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:685-702. [DOI: 10.1007/978-94-007-2888-2_30] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
184
|
|
185
|
Sanchez-Ponce D, Blazquez-Llorca L, DeFelipe J, Garrido JJ, Munoz A. Colocalization of -actinin and Synaptopodin in the Pyramidal Cell Axon Initial Segment. Cereb Cortex 2011; 22:1648-61. [DOI: 10.1093/cercor/bhr251] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
186
|
Rook MB, Evers MM, Vos MA, Bierhuizen MFA. Biology of cardiac sodium channel Nav1.5 expression. Cardiovasc Res 2011; 93:12-23. [PMID: 21937582 DOI: 10.1093/cvr/cvr252] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Na(v)1.5, the pore forming α-subunit of the voltage-dependent cardiac Na(+) channel, is an integral membrane protein involved in the initiation and conduction of action potentials. Mutations in the gene-encoding Na(v)1.5, SCN5A, have been associated with a variety of arrhythmic disorders, including long QT, Brugada, and sick sinus syndromes as well as progressive cardiac conduction defect and atrial standstill. Moreover, alterations in the Na(v)1.5 expression level and/or sodium current density have been frequently noticed in acquired cardiac disorders, such as heart failure. The molecular mechanisms underlying these alterations are poorly understood, but are considered essential for conception of arrhythmogenesis and the development of therapeutic strategies for prevention or treatment of arrhythmias. The unravelling of such mechanisms requires critical molecular insight into the biology of Na(v)1.5 expression and function. Therefore, the aim of this review is to provide an up-to-date account of molecular determinants of normal Na(v)1.5 expression and function. The parts of the Na(v)1.5 life cycle that are discussed include (i) regulatory aspects of the SCN5A gene and transcript structure, (ii) the nature, molecular determinants, and functional consequences of Na(v)1.5 post-translational modifications, and (iii) the role of Na(v)1.5 interacting proteins in cellular trafficking. The reviewed studies have provided valuable information on how the Na(v)1.5 expression level, localization, and biophysical properties are regulated, but also revealed that our understanding of the underlying mechanisms is still limited.
Collapse
Affiliation(s)
- Martin B Rook
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, The Netherlands
| | | | | | | |
Collapse
|
187
|
Erickson JR, He BJ, Grumbach IM, Anderson ME. CaMKII in the cardiovascular system: sensing redox states. Physiol Rev 2011; 91:889-915. [PMID: 21742790 DOI: 10.1152/physrev.00018.2010] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The multifunctional Ca(2+)- and calmodulin-dependent protein kinase II (CaMKII) is now recognized to play a central role in pathological events in the cardiovascular system. CaMKII has diverse downstream targets that promote vascular disease, heart failure, and arrhythmias, so improved understanding of CaMKII signaling has the potential to lead to new therapies for cardiovascular disease. CaMKII is a multimeric serine-threonine kinase that is initially activated by binding calcified calmodulin (Ca(2+)/CaM). Under conditions of sustained exposure to elevated Ca(2+)/CaM, CaMKII transitions into a Ca(2+)/CaM-autonomous enzyme by two distinct but parallel processes. Autophosphorylation of threonine-287 in the CaMKII regulatory domain "traps" CaMKII into an open configuration even after Ca(2+)/CaM unbinding. More recently, our group identified a pair of methionines (281/282) in the CaMKII regulatory domain that undergo a partially reversible oxidation which, like autophosphorylation, prevents CaMKII from inactivating after Ca(2+)/CaM unbinding. Here we review roles of CaMKII in cardiovascular disease with an eye to understanding how CaMKII may act as a transduction signal to connect pro-oxidant conditions into specific downstream pathological effects that are relevant to rare and common forms of cardiovascular disease.
Collapse
Affiliation(s)
- Jeffrey R Erickson
- Department of Pharmacology, University of California at Davis, Davis, California 95616, USA.
| | | | | | | |
Collapse
|
188
|
Machnicka B, Grochowalska R, Bogusławska DM, Sikorski AF, Lecomte MC. Spectrin-based skeleton as an actor in cell signaling. Cell Mol Life Sci 2011; 69:191-201. [PMID: 21877118 PMCID: PMC3249148 DOI: 10.1007/s00018-011-0804-5] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 08/08/2011] [Accepted: 08/10/2011] [Indexed: 01/12/2023]
Abstract
This review focuses on the recent advances in functions of spectrins in non-erythroid cells. We discuss new data concerning the commonly known role of the spectrin-based skeleton in control of membrane organization, stability and shape, and tethering protein mosaics to the cellular motors and to all major filament systems. Particular effort has been undertaken to highlight recent advances linking spectrin to cell signaling phenomena and its participation in signal transduction pathways in many cell types.
Collapse
Affiliation(s)
- B Machnicka
- University of Zielona Góra, Zielona Góra, Poland
| | | | | | | | | |
Collapse
|
189
|
Erickson JR, Patel R, Ferguson A, Bossuyt J, Bers DM. Fluorescence resonance energy transfer-based sensor Camui provides new insight into mechanisms of calcium/calmodulin-dependent protein kinase II activation in intact cardiomyocytes. Circ Res 2011; 109:729-38. [PMID: 21835909 DOI: 10.1161/circresaha.111.247148] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Calcium/calmodulin-dependent protein kinase II (CaMKII) is a key mediator of intracellular signaling in the heart. However, the tools currently available for assessing dynamic changes in CaMKII localization and activation in living myocytes are limited. OBJECTIVE We use Camui, a novel FRET-based biosensor in which full-length CaMKII is flanked by CFP and YFP, to measure CaMKII activation state in living rabbit myocytes. METHODS AND RESULTS We show that Camui and mutant variants that lack the sites of CaMKII autophosphorylation (T286A) and oxidative regulation (CM280/1VV) serve as useful biosensors for CaMKIIδ activation state. Camui (wild-type or mutant) was expressed in isolated adult cardiac myocytes, and localization and CaMKII activation state were determined using confocal microscopy. Camui, like CaMKIIδ, is concentrated at the z-lines, with low baseline activation state. Camui activation increased directly with pacing frequency, but the maximal effect was blunted with the T286A, consistent with frequency-dependent phosphorylation of CaMKII at T286 mainly at high-frequency and high-amplitude Ca transients. Camui was also activated by 4 neurohormonal agonists. Angiotensin II and endothelin-1 activated Camui, largely through an oxidation-dependent mechanism, whereas isoproterenol- and phenylephrine-mediated mechanisms had a significant autophosphorylation-dependent component. CONCLUSIONS Camui is a novel, nondestructive tool that allows spatiotemporally resolved measurement of CaMKII activation state in physiologically functioning myocytes. This represents a first step in using Camui to elucidate key mechanistic details of CaMKII signaling in live hearts and myocytes.
Collapse
Affiliation(s)
- Jeffrey R Erickson
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | | | | | | | | |
Collapse
|
190
|
Mohler PJ, Hund TJ. Membrane-select regulation of cardiac Na(v) channel isoforms. Heart Rhythm 2011; 8:1931-2. [PMID: 21835149 DOI: 10.1016/j.hrthm.2011.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Indexed: 10/17/2022]
|
191
|
In vitro maturation of the cisternal organelle in the hippocampal neuron's axon initial segment. Mol Cell Neurosci 2011; 48:104-16. [PMID: 21708259 DOI: 10.1016/j.mcn.2011.06.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 06/07/2011] [Accepted: 06/09/2011] [Indexed: 11/21/2022] Open
Abstract
Regulation of Ca(2+) concentrations is essential to maintain the structure and function of the axon initial segment (AIS). The so-called cisternal organelle of the AIS is a structure involved in this regulation, although little is known as to how this organelle matures and is stabilized. Here we describe how the cisternal organelle develops in cultured hippocampal neurons and the interactions that facilitate its stabilization in the AIS. We also characterize the developmental expression of molecules involved in Ca(2+) regulation in the AIS. Our results indicate that synaptopodin (synpo) positive elements considered to be associated to the cisternal organelle are present in the AIS after six days in vitro. There are largely overlapping microdomains containing the inositol 1,4,5-triphosphate receptor 1 (IP(3)R1) and the Ca(2+) binding protein annexin 6, suggesting that the regulation of Ca(2+) concentrations in the AIS is sensitive to IP(3) and subject to regulation by annexin 6. The expression of synpo, IP(3)R1 and annexin 6 in the AIS is independent of the neuron activity, as it was unaffected by tetrodotoxin blockage of action potentials and it was resistant to detergent extraction, indicating that these proteins interact with scaffolding and/or cytoskeleton proteins. The presence of ankyrin G seems to be required for the acquisition and maintenance of the cisternal organelle, while the integrity of the actin cytoskeleton must be maintained for the expression IP(3)R1 and annexin 6 to persist in the AIS.
Collapse
|
192
|
Yao L, Fan P, Jiang Z, Viatchenko-Karpinski S, Wu Y, Kornyeyev D, Hirakawa R, Budas GR, Rajamani S, Shryock JC, Belardinelli L. Nav1.5-dependent persistent Na+ influx activates CaMKII in rat ventricular myocytes and N1325S mice. Am J Physiol Cell Physiol 2011; 301:C577-86. [PMID: 21677263 DOI: 10.1152/ajpcell.00125.2011] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Late Na(+) current (I(NaL)) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) are both increased in the diseased heart. Recently, CaMKII was found to phosphorylate the Na(+) channel 1.5 (Na(v)1.5), resulting in enhanced I(NaL). Conversely, an increase of I(NaL) would be expected to cause elevation of intracellular Ca(2+) and activation of CaMKII. However, a relationship between enhancement of I(NaL) and activation of CaMKII has yet to be demonstrated. We investigated whether Na(+) influx via Na(v)1.5 leads to CaMKII activation and explored the functional significance of this pathway. In neonatal rat ventricular myocytes (NRVM), treatment with the I(NaL) activators anemone toxin II (ATX-II) or veratridine increased CaMKII autophosphorylation and increased phosphorylation of CaMKII substrates phospholamban and ryanodine receptor 2. Knockdown of Na(v)1.5 (but not Na(v)1.1 or Na(v)1.2) prevented ATX-II-induced CaMKII phosphorylation, providing evidence for a specific role of Na(v)1.5 in CaMKII activation. In support of this view, CaMKII activity was also increased in hearts of transgenic mice overexpressing a gain-of-function Na(v)1.5 mutant (N(1325)S). The effects of both ATX-II and the N(1325)S mutation were reversed by either I(NaL) inhibition (with ranolazine or tetrodotoxin) or CaMKII inhibition (with KN93 or autocamtide 2-related inhibitory peptide). Furthermore, ATX-II treatment also induced CaMKII-Na(v)1.5 coimmunoprecipitation. The same association between CaMKII and Na(v)1.5 was also found in N(1325)S mice, suggesting a direct protein-protein interaction. Pharmacological inhibitions of either CaMKII or I(NaL) also prevented ATX-II-induced cell death in NRVM and reduced the incidence of polymorphic ventricular tachycardia induced by ATX-II in rat perfused hearts. Taken together, these results suggest that a Na(v)1.5-dependent increase in Na(+) influx leads to activation of CaMKII, which in turn phosphorylates Na(v)1.5, further promoting Na(+) influx. Pharmacological inhibition of either CaMKII or Na(v)1.5 can ameliorate cardiac dysfunction caused by excessive Na(+) influx.
Collapse
Affiliation(s)
- Lina Yao
- Department of Biology, Gilead Sciences, Palo Alto, California 94304, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
193
|
Beyond membrane channelopathies: alternative mechanisms underlying complex human disease. Acta Pharmacol Sin 2011; 32:798-804. [PMID: 21642948 DOI: 10.1038/aps.2011.34] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Over the past fifteen years, our understanding of the molecular mechanisms underlying human disease has flourished in large part due to the discovery of gene mutations linked with membrane ion channels and transporters. In fact, ion channel defects ("channelopathies" - the focus of this review series) have been associated with a spectrum of serious human disease phenotypes including cystic fibrosis, cardiac arrhythmia, diabetes, skeletal muscle defects, and neurological disorders. However, we now know that human disease, particularly excitable cell disease, may be caused by defects in non-ion channel polypeptides including in cellular components residing well beneath the plasma membrane. For example, over the past few years, a new class of potentially fatal cardiac arrhythmias has been linked with cytoplasmic proteins that include sub-membrane adapters such as ankyrin-B (ANK2), ankyrin-G (ANK3), and alpha-1 syntrophin, membrane coat proteins including caveolin-3 (CAV3), signaling platforms including yotiao (AKAP9), and cardiac enzymes (GPD1L). The focus of this review is to detail the exciting role of lamins, yet another class of gene products that have provided elegant new insight into human disease.
Collapse
|
194
|
Sato PY, Coombs W, Lin X, Nekrasova O, Green KJ, Isom LL, Taffet SM, Delmar M. Interactions between ankyrin-G, Plakophilin-2, and Connexin43 at the cardiac intercalated disc. Circ Res 2011; 109:193-201. [PMID: 21617128 DOI: 10.1161/circresaha.111.247023] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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 significant changes in subcellular distribution and/or abundance of PKP2 and Connexin43 as well as a decrease in intercellular adhesion strength and electric coupling. Regulation of AnkG and of Na(v)1.5 by Plakophilin-2 was also demonstrated. Finally, optical mapping experiments in AnkG-silenced cells demonstrated a shift in the minimal frequency at which rate-dependence activation block was observed. CONCLUSIONS These experiments support the hypothesis that AnkG is a key functional component of the intercalated disc at the intersection of 3 complexes often considered independent: the voltage-gated sodium channel, gap junctions, and the cardiac desmosome. Possible implications to the pathophysiology of inherited arrhythmias (such as arrhythmogenic right ventricular cardiomyopathy) are discussed.
Collapse
Affiliation(s)
- Priscila Y Sato
- Division of Cardiovascular Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | | | | | | | | | | | | | | |
Collapse
|
195
|
|
196
|
Abstract
During peripheral nerve development, Schwann cells ensheathe axons and form myelin to enable rapid and efficient action potential propagation. Although myelination requires profound changes in Schwann cell shape, how neuron-glia interactions converge on the Schwann cell cytoskeleton to induce these changes is unknown. Here, we demonstrate that the submembranous cytoskeletal proteins αII and βII spectrin are polarized in Schwann cells and colocalize with signaling molecules known to modulate myelination in vitro. Silencing expression of these spectrins inhibited myelination in vitro, and remyelination in vivo. Furthermore, myelination was disrupted in motor nerves of zebrafish lacking αII spectrin. Finally, we demonstrate that loss of spectrin significantly reduces both F-actin in the Schwann cell cytoskeleton and the Nectin-like protein, Necl4, at the contact site between Schwann cells and axons. Therefore, we propose αII and βII spectrin in Schwann cells integrate the neuron-glia interactions mediated by membrane proteins into the actin-dependent cytoskeletal rearrangements necessary for myelination.
Collapse
|
197
|
Curran J, Mohler PJ. Coordinating electrical activity of the heart: ankyrin polypeptides in human cardiac disease. Expert Opin Ther Targets 2011; 15:789-801. [PMID: 21457127 DOI: 10.1517/14728222.2011.575363] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Over the past ten years, ankyrin polypeptides have emerged as players in cardiac excitation-contraction coupling. Once thought to solely play a structural role, loss-of-function variants of genes encoding ankyrin polypeptides have highlighted how this protein mediates subcellular localization of various electrical components of the excitation-contraction coupling machinery. Evidence has revealed how disruption of this localization is the primary cause of various cardiomyopathies, ranging from long-QT syndrome 4, to sinus node disease, to more common forms of arrhythmias. AREAS COVERED The roles of ankyrin polypeptides in excitation-contraction coupling in the heart and the development of ankyrin-specific cardiomyopathies. How ankyrin polypeptides may be involved in structural and electrical remodeling of the heart, post-myocardial infarct. How ankyrin interactions with membrane-bound ion channels may regulate these channels' response to stimuli. New data, which offers the potential for unique therapies, for not only combating heart disease, but also for wider applications to various disease states. EXPERT OPINION The ankyrin family of adapter proteins is emerging as an intimate player in cardiac excitation-contraction coupling. Until recently, these proteins have gone largely unappreciated for their importance in proper cardiac function. New insights into how these proteins function within the heart are offering potentially new avenues for therapies against cardiomyopathy.
Collapse
Affiliation(s)
- Jerry Curran
- The Ohio State University, The Dorothy M. Davis Heart and Lung Research Institute, Columbus, 43210, USA.
| | | |
Collapse
|
198
|
Anderson ME, Brown JH, Bers DM. CaMKII in myocardial hypertrophy and heart failure. J Mol Cell Cardiol 2011; 51:468-73. [PMID: 21276796 DOI: 10.1016/j.yjmcc.2011.01.012] [Citation(s) in RCA: 338] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 01/13/2011] [Accepted: 01/13/2011] [Indexed: 02/08/2023]
Abstract
Many signals have risen and fallen in the tide of investigation into mechanisms of myocardial hypertrophy and heart failure (HF). In our opinion, the multifunctional Ca and calmodulin-dependent protein kinase II (CaMKII) has emerged as a molecule to watch, in part because a solid body of accumulated data essentially satisfy Koch's postulates, showing that the CaMKII pathway is a core mechanism for promoting myocardial hypertrophy and heart failure. Multiple groups have now confirmed the following: (1) that CaMKII activity is increased in hypertrophied and failing myocardium from animal models and patients; (2) CaMKII overexpression causes myocardial hypertrophy and HF and (3) CaMKII inhibition (by drugs, inhibitory peptides and gene deletion) improves myocardial hypertrophy and HF. Patients with myocardial disease die in equal proportion from HF and arrhythmias, and a major therapeutic obstacle is that drugs designed to enhance myocardial contraction promote arrhythmias. In contrast, inhibiting the CaMKII pathway appears to reduce arrhythmias and improve myocardial responses to pathological stimuli. This brief paper will introduce the molecular physiology of CaMKII and discuss the impact of CaMKII on ion channels, Ca handling proteins and transcription in myocardium. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".
Collapse
Affiliation(s)
- Mark E Anderson
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
| | | | | |
Collapse
|
199
|
Wagner S, Ruff HM, Weber SL, Bellmann S, Sowa T, Schulte T, Anderson ME, Grandi E, Bers DM, Backs J, Belardinelli L, Maier LS. Reactive oxygen species-activated Ca/calmodulin kinase IIδ is required for late I(Na) augmentation leading to cellular Na and Ca overload. Circ Res 2011; 108:555-65. [PMID: 21252154 DOI: 10.1161/circresaha.110.221911] [Citation(s) in RCA: 230] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
RATIONALE In heart failure Ca/calmodulin kinase (CaMK)II expression and reactive oxygen species (ROS) are increased. Both ROS and CaMKII can increase late I(Na) leading to intracellular Na accumulation and arrhythmias. It has been shown that ROS can activate CaMKII via oxidation. OBJECTIVE We tested whether CaMKIIδ is required for ROS-dependent late I(Na) regulation and whether ROS-induced Ca released from the sarcoplasmic reticulum (SR) is involved. METHODS AND RESULTS 40 μmol/L H(2)O(2) significantly increased CaMKII oxidation and autophosphorylation in permeabilized rabbit cardiomyocytes. Without free [Ca](i) (5 mmol/L BAPTA/1 mmol/L Br(2)-BAPTA) or after SR depletion (caffeine 10 mmol/L, thapsigargin 5 μmol/L), the H(2)O(2)-dependent CaMKII oxidation and autophosphorylation was abolished. H(2)O(2) significantly increased SR Ca spark frequency (confocal microscopy) but reduced SR Ca load. In wild-type (WT) mouse myocytes, H(2)O(2) increased late I(Na) (whole cell patch-clamp). This increase was abolished in CaMKIIδ(-/-) myocytes. H(2)O(2)-induced [Na](i) and [Ca](i) accumulation (SBFI [sodium-binding benzofuran isophthalate] and Indo-1 epifluorescence) was significantly slowed in CaMKIIδ(-/-) myocytes (versus WT). CaMKIIδ(-/-) myocytes developed significantly less H(2)O(2)-induced arrhythmias and were more resistant to hypercontracture. Opposite results (increased late I(Na), [Na](i) and [Ca](i) accumulation) were obtained by overexpression of CaMKIIδ in rabbit myocytes (adenoviral gene transfer) reversible with CaMKII inhibition (10 μmol/L KN93 or 0.1 μmol/L AIP [autocamtide 2-related inhibitory peptide]). CONCLUSIONS Free [Ca](i) and a functional SR are required for ROS activation of CaMKII. ROS-activated CaMKIIδ enhances late I(Na), which may lead to cellular Na and Ca overload. This may be of relevance in hear failure, where enhanced ROS production meets increased CaMKII expression.
Collapse
Affiliation(s)
- Stefan Wagner
- Department of Cardiology and Pneumology, Georg-August-University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
200
|
Cunha SR, Mohler PJ. Ankyrin-based cellular pathways for cardiac ion channel and transporter targeting and regulation. Semin Cell Dev Biol 2010; 22:166-70. [PMID: 20934528 DOI: 10.1016/j.semcdb.2010.09.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 09/29/2010] [Accepted: 09/30/2010] [Indexed: 10/19/2022]
Abstract
The coordinate activities of ion channels and transporters regulate myocyte membrane excitability and normal cardiac function. Dysfunction in cardiac ion channel and transporter function may result in cardiac arrhythmias and sudden cardiac death. While the past fifteen years have linked defects in ion channel biophysical properties with human disease, more recent findings illustrate that ion channel and transporter localization within cardiomyocytes is equally critical for normal membrane excitability and tissue function. Ankyrins are a family of multifunctional adapter proteins required for the expression, membrane localization, and regulation of select cardiac ion channels and transporters. Notably, loss of ankyrin expression in mice, and ankyrin loss-of-function in humans is now associated with defects in myocyte excitability and cardiac physiology. Here, we provide an overview of the roles of ankyrin polypeptides in cardiac physiology, as well as review other recently identified pathways required for the membrane expression and regulation of key cardiac ion channels and transporters.
Collapse
Affiliation(s)
- Shane R Cunha
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, United States
| | | |
Collapse
|