51
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Physical interaction between calcineurin and Cav3.2 T‐type Ca
2
+
channel modulates their functions. FEBS Lett 2013; 587:1723-30. [DOI: 10.1016/j.febslet.2013.04.040] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 04/26/2013] [Accepted: 04/29/2013] [Indexed: 11/23/2022]
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52
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Abstract
Low-frequency depression (LFD) of transmitter release occurs at phasic synapses with stimulation at 0.2 Hz in both isolated crayfish (Procambarus clarkii) neuromuscular junction (NMJ) preparations and in intact animals. LFD is regulated by presynaptic activity of the Ca(2+)-dependent phosphatase calcineurin (Silverman-Gavrila and Charlton, 2009). Since the fast Ca(2+) chelator BAPTA-AM inhibits LFD but the slow chelator EGTA-AM does not, the Ca(2+) sensor for LFD may be close to a Ca(2+) source at active zones. Calcineurin can be activated by the Ca(2+)-activated protease calpain, and immunostaining showed that both proteins are present at nerve terminals. Three calpain inhibitors, calpain inhibitor I, MDL-28170, and PD150606, but not the control compound PD145305, inhibit LFD both in the intact animal as shown by electromyograms and by intracellular recordings at neuromuscular junctions. Analysis of mini-EPSPs indicated that these inhibitors had minimal postsynaptic effects. Proteolytic activity in CNS extract, detected by a fluorescent calpain substrate, was modulated by Ca(2+) and calpain inhibitors. Western blot analysis of CNS extract showed that proteolysis of calcineurin to a fragment consistent with the constitutively active form required Ca(2+) and was blocked by calpain inhibitors. Inhibition of LFD by calpain inhibition blocks the reduction in phosphoactin and the depolymerization of tubulin that normally occurs in LFD, probably by blocking the dephosphorylation of cytoskeletal proteins by calcineurin. In contrast, high-frequency depression does not involve protein phosphorylation- or calpain-dependent mechanisms. LFD may involve a specific pathway in which local Ca(2+) signaling activates presynaptic calpain and calcineurin at active zones and causes changes of tubulin cytoskeleton.
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Al-Biltagi M, Serag AR, Hefidah MM, Mabrouk MM. Evaluation of cardiac functions with Doppler echocardiography in children with Down syndrome and anatomically normal heart. Cardiol Young 2013; 23:174-80. [PMID: 22717046 DOI: 10.1017/s1047951112000613] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE To study the cardiac functions in Down syndrome children who did not have structural cardiac lesion by conventional and tissue Doppler echocardiography. MATERIALS AND METHODS A total of 85 children with Down syndrome without anatomic heart disease and 50 normal control children were subjected to the assessment of right and left ventricular functions by both two-dimensional and tissue Doppler echocardiography. RESULTS Children with Down syndrome had significantly higher left ventricular ejection fraction detected by two-dimensional echocardiography and left ventricular diastolic dysfunction detected by tissue Doppler than observed in the controls. In addition, children with Down syndrome also had right ventricular systolic and diastolic dysfunctions. Children with Down syndrome had significantly higher pulmonary artery systolic pressure than the control children. There was no significant difference in the cardiac functions between children with non-disjunction Down syndrome and those with the translocation type. CONCLUSION Despite an apparently normal heart, children with Down syndrome may have silent disturbed cardiac functions, which may be detected by two-dimensional or tissue Doppler echocardiography. This may have an important clinical implication, especially before involving Down syndrome children in surgery or strenuous exercise.
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Affiliation(s)
- Mohammed Al-Biltagi
- Cardiology Unit, Department of Paediatric, Faculty of Medicine, Tanta University, Tanta, Egypt.
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54
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Ramachandran KV, Hennessey JA, Barnett AS, Yin X, Stadt HA, Foster E, Shah RA, Yazawa M, Dolmetsch RE, Kirby ML, Pitt GS. Calcium influx through L-type CaV1.2 Ca2+ channels regulates mandibular development. J Clin Invest 2013; 123:1638-46. [PMID: 23549079 DOI: 10.1172/jci66903] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/29/2013] [Indexed: 11/17/2022] Open
Abstract
The identification of a gain-of-function mutation in CACNA1C as the cause of Timothy Syndrome (TS), a rare disorder characterized by cardiac arrhythmias and syndactyly, highlighted unexpected roles for the L-type voltage-gated Ca2+ channel CaV1.2 in nonexcitable cells. How abnormal Ca2+ influx through CaV1.2 underlies phenotypes such as the accompanying syndactyly or craniofacial abnormalities in the majority of affected individuals is not readily explained by established CaV1.2 roles. Here, we show that CaV1.2 is expressed in the first and second pharyngeal arches within the subset of cells that give rise to jaw primordia. Gain-of-function and loss-of-function studies in mouse, in concert with knockdown/rescue and pharmacological approaches in zebrafish, demonstrated that Ca2+ influx through CaV1.2 regulates jaw development. Cranial neural crest migration was unaffected by CaV1.2 knockdown, suggesting a role for CaV1.2 later in development. Focusing on the mandible, we observed that cellular hypertrophy and hyperplasia depended upon Ca2+ signals through CaV1.2, including those that activated the calcineurin signaling pathway. Together, these results provide new insights into the role of voltage-gated Ca2+ channels in nonexcitable cells during development.
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Affiliation(s)
- Kapil V Ramachandran
- Department of Medicine (Cardiology), Duke University Medical Center, Durham, North Carolina, USA
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55
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Gaydukov AE, Tarasova EO, Balezina OP. Calcium-dependent phosphatase calcineurin downregulates evoked neurotransmitter release in neuromuscular junctions of mice. NEUROCHEM J+ 2013. [DOI: 10.1134/s1819712413010030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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56
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Shaw RM, Colecraft HM. L-type calcium channel targeting and local signalling in cardiac myocytes. Cardiovasc Res 2013; 98:177-86. [PMID: 23417040 DOI: 10.1093/cvr/cvt021] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In the heart, Ca(2+) influx via Ca(V)1.2 L-type calcium channels (LTCCs) is a multi-functional signal that triggers muscle contraction, controls action potential duration, and regulates gene expression. The use of LTCC Ca(2+) as a multi-dimensional signalling molecule in the heart is complicated by several aspects of cardiac physiology. Cytosolic Ca(2+) continuously cycles between ~100 nM and ~1 μM with each heartbeat due to Ca(2+) linked signalling from LTCCs to ryanodine receptors. This rapid cycling raises the question as to how cardiac myocytes distinguish the Ca(2+) fluxes originating through L-type channels that are dedicated to contraction from Ca(2+) fluxes originating from other L-type channels that are used for non-contraction-related signalling. In general, disparate Ca(2+) sources in cardiac myocytes such as current through differently localized LTCCs as well as from IP3 receptors can signal selectively to Ca(2+)-dependent effectors in local microdomains that can be impervious to the cytoplasmic Ca(2+) transients that drive contraction. A particular challenge for diversified signalling via cardiac LTCCs is that they are voltage-gated and, therefore, open and presumably flood their microdomains with Ca(2+) with each action potential. Thus spatial localization of Cav1.2 channels to different types of microdomains of the ventricular cardiomyocyte membrane as well as the existence of particular macromolecular complexes in each Cav1.2 microdomain are important to effect different types of Cav1.2 signalling. In this review we examine aspects of Cav1.2 structure, targeting and signalling in two specialized membrane microdomains--transverse tubules and caveolae.
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Affiliation(s)
- Robin M Shaw
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, CA 94143, USA
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57
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Harvey RD, Hell JW. CaV1.2 signaling complexes in the heart. J Mol Cell Cardiol 2012; 58:143-52. [PMID: 23266596 DOI: 10.1016/j.yjmcc.2012.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/07/2012] [Accepted: 12/10/2012] [Indexed: 01/08/2023]
Abstract
L-type Ca(2+) channels (LTCCs) are essential for generation of the electrical and mechanical properties of cardiac muscle. Furthermore, regulation of LTCC activity plays a central role in mediating the effects of sympathetic stimulation on the heart. The primary mechanism responsible for this regulation involves β-adrenergic receptor (βAR) stimulation of cAMP production and subsequent activation of protein kinase A (PKA). Although it is well established that PKA-dependent phosphorylation regulates LTCC function, there is still much we do not understand. However, it has recently become clear that the interaction of the various signaling proteins involved is not left to completely stochastic events due to random diffusion. The primary LTCC expressed in cardiac muscle, CaV1.2, forms a supramolecular signaling complex that includes the β2AR, G proteins, adenylyl cyclases, phosphodiesterases, PKA, and protein phosphatases. In some cases, the protein interactions with CaV1.2 appear to be direct, in other cases they involve scaffolding proteins such as A kinase anchoring proteins and caveolin-3. Functional evidence also suggests that the targeting of these signaling proteins to specific membrane domains plays a critical role in maintaining the fidelity of receptor mediated LTCC regulation. This information helps explain the phenomenon of compartmentation, whereby different receptors, all linked to the production of a common diffusible second messenger, can vary in their ability to regulate LTCC activity. The purpose of this review is to examine our current understanding of the signaling complexes involved in cardiac LTCC regulation.
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Affiliation(s)
- Robert D Harvey
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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58
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Ch'ng TH, Uzgil B, Lin P, Avliyakulov NK, O'Dell TJ, Martin KC. Activity-dependent transport of the transcriptional coactivator CRTC1 from synapse to nucleus. Cell 2012; 150:207-21. [PMID: 22770221 DOI: 10.1016/j.cell.2012.05.027] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 04/05/2012] [Accepted: 05/02/2012] [Indexed: 12/30/2022]
Abstract
Long-lasting changes in synaptic efficacy, such as those underlying long-term memory, require transcription. Activity-dependent transport of synaptically localized transcriptional regulators provides a direct means of coupling synaptic stimulation with changes in transcription. The CREB-regulated transcriptional coactivator (CRTC1), which is required for long-term hippocampal plasticity, binds CREB to potently promote transcription. We show that CRTC1 localizes to synapses in silenced hippocampal neurons but translocates to the nucleus in response to localized synaptic stimulation. Regulated nuclear translocation occurs only in excitatory neurons and requires calcium influx and calcineurin activation. CRTC1 is controlled in a dual fashion with activity regulating CRTC1 nuclear translocation and cAMP modulating its persistence in the nucleus. Neuronal activity triggers a complex change in CRTC1 phosphorylation, suggesting that CRTC1 may link specific types of stimuli to specific changes in gene expression. Together, our results indicate that synapse-to-nuclear transport of CRTC1 dynamically informs the nucleus about synaptic activity.
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Affiliation(s)
- Toh Hean Ch'ng
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1737, USA
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59
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Huang CCY, Ko ML, Vernikovskaya DI, Ko GYP. Calcineurin serves in the circadian output pathway to regulate the daily rhythm of L-type voltage-gated calcium channels in the retina. J Cell Biochem 2012; 113:911-22. [PMID: 22371971 DOI: 10.1002/jcb.23419] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The L-type voltage-gated calcium channels (L-VGCCs) in avian retinal cone photoreceptors are under circadian control, in which the protein expression of the α1 subunits and the current density are greater at night than during the day. Both Ras-mitogen-activated protein kinase (MAPK) and Ras-phosphatidylionositol 3 kinase-protein kinase B (PI3K-AKT) signaling pathways are part of the circadian output that regulate the L-VGCC rhythm, while cAMP-dependent signaling is further upstream of Ras to regulate the circadian outputs in photoreceptors. However, there are missing links between cAMP-dependent signaling and Ras in the circadian output regulation of L-VGCCs. In this study, we report that calcineurin, a Ca2+/calmodulin-dependent serine (ser)/threonine (thr) phosphatase, participates in the circadian output pathway to regulate L-VGCCs through modulating both Ras-MAPK and Ras-PI3K-AKT signaling. The activity of calcineurin, but not its protein expression, was under circadian regulation. Application of a calcineurin inhibitor, FK-506 or cyclosporine A, reduced the L-VGCC current density at night with a corresponding decrease in L-VGCCα1D protein expression, but the circadian rhythm of L-VGCCα1D mRNA levels were not affected. Inhibition of calcineurin further reduced the phosphorylation of ERK and AKT (at thr 308) and inhibited the activation of Ras, but inhibitors of MAPK or PI3K signaling did not affect the circadian rhythm of calcineurin activity. However, inhibition of adenylate cyclase significantly dampened the circadian rhythm of calcineurin activity. These results suggest that calcineurin is upstream of MAPK and PI3K-AKT but downstream of cAMP in the circadian regulation of L-VGCCs.
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Affiliation(s)
- Cathy Chia-Yu Huang
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458, USA
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60
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Na(+)/H(+) exchanger 1 directly binds to calcineurin A and activates downstream NFAT signaling, leading to cardiomyocyte hypertrophy. Mol Cell Biol 2012; 32:3265-80. [PMID: 22688515 DOI: 10.1128/mcb.00145-12] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The calcineurin A (CaNA) subunit was identified as a novel binding partner of plasma membrane Na(+)/H(+) exchanger 1 (NHE1). CaN is a Ca(2+)-dependent phosphatase involved in many cellular functions, including cardiac hypertrophy. Direct binding of CaN to the (715)PVITID(720) sequence of NHE1, which resembles the consensus CaN-binding motif (PXIXIT), was observed. Overexpression of NHE1 promoted serum-induced CaN/nuclear factor of activated T cells (NFAT) signaling in fibroblasts, as indicated by enhancement of NFAT promoter activity and nuclear translocation, which was attenuated by NHE1 inhibitor. In neonatal rat cardiomyocytes, NHE1 stimulated hypertrophic gene expression and the NFAT pathway, which were inhibited by a CaN inhibitor, FK506. Importantly, CaN activity was strongly enhanced with increasing pH, so NHE1 may promote CaN/NFAT signaling via increased intracellular pH. Indeed, Na(+)/H(+) exchange activity was required for NHE1-dependent NFAT signaling. Moreover, interaction of CaN with NHE1 and clustering of NHE1 to lipid rafts were also required for this response. Based on these results, we propose that NHE1 activity may generate a localized membrane microdomain with higher pH, thereby sensitizing CaN to activation and promoting NFAT signaling. In cardiomyocytes, such signaling can be a pathway of NHE1-dependent hypertrophy.
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61
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Heart repair by reprogramming non-myocytes with cardiac transcription factors. Nature 2012; 485:599-604. [PMID: 22660318 PMCID: PMC3367390 DOI: 10.1038/nature11139] [Citation(s) in RCA: 876] [Impact Index Per Article: 73.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 04/12/2012] [Indexed: 12/25/2022]
Abstract
The adult mammalian heart possesses little regenerative potential following injury. Fibrosis due to activation of cardiac fibroblasts impedes cardiac regeneration and contributes to loss of contractile function, pathological remodelling and susceptibility to arrhythmias. Cardiac fibroblasts account for a majority of cells in the heart and represent a potential cellular source for restoration of cardiac function following injury through phenotypic reprogramming to a myocardial cell fate. Here we show that four transcription factors, GATA4, HAND2, MEF2C and TBX5, can cooperatively reprogram adult mouse tail-tip and cardiac fibroblasts into beating cardiac-like myocytes in vitro. Forced expression of these factors in dividing non-cardiomyocytes in mice reprograms these cells into functional cardiac-like myocytes, improves cardiac function and reduces adverse ventricular remodelling following myocardial infarction. Our results suggest a strategy for cardiac repair through reprogramming fibroblasts resident in the heart with cardiogenic transcription factors or other molecules.
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62
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Zhao F, Zhang S, Chen L, Wu Y, Qin J, Shao Y, Wang X, Chen Y. Calcium- and integrin-binding protein-1 and calcineurin are upregulated in the right atrial myocardium of patients with atrial fibrillation. Europace 2012; 14:1726-33. [PMID: 22547769 DOI: 10.1093/europace/eus149] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS The aim of this study was to determine whether altered expression and distribution of calcium- and integrin-binding protein-1 (CIB1) is involved in the pathogenesis of different types of patients with atrial fibrillation (AF) associated with valvular heart disease (VHD). METHODS AND RESULTS Right atrial specimens obtained from 65 patients undergoing valve replacement surgery were divided into three groups: sinus rhythm group (n= 24), paroxysmal atrial fibrillation group (PaAF; n= 10), and persistent atrial fibrillation group (PeAF; AF lasting >6 month; n= 31). The expression levels of mRNA and protein content for CIB1, calcineurin B, calcineurin A, and Na(+)-Ca(2+) exchanger-1 (NCX1) were measured. We also measured the combination of CIB1 with calcineurin B, L-type Ca(2+) channel, and NCX1 using immunoprecipitation. Expression of mRNA and protein content of CIB1, calcineurin B, calcineurin A, and NCX1 was increased in the AF group. Calcium- and integrin-binding protein-1 interacted with calcineurin B and L-type Ca(2+) channel. Surprisingly, CIB1 also combined with NCX1. CONCLUSIONS The CIB1 and calcineurin expression was increased in AF atrial tissue and was related to the type of AF. This finding suggests that CIB1 may be involved in the pathogenesis of AF in VHD patients.
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Affiliation(s)
- Fei Zhao
- Cardiothoracic Surgical Department, the First Affiliated Hospital of Nanjing Medical University, No. 300 Guangzhou Road, Nanjing 210029, Jiangsu Province, China
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63
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Cohen-Kutner M, Yahalom Y, Trus M, Atlas D. Calcineurin Controls Voltage-Dependent-Inactivation (VDI) of the Normal and Timothy Cardiac Channels. Sci Rep 2012; 2:366. [PMID: 22511998 PMCID: PMC3328044 DOI: 10.1038/srep00366] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/22/2012] [Indexed: 12/25/2022] Open
Abstract
Ca2+-entry in the heart is tightly controlled by Cav1.2 inactivation, which involves Ca2+-dependent inactivation (CDI) and voltage-dependent inactivation (VDI) components. Timothy syndrome, a subtype-form of congenital long-QT syndrome, results from a nearly complete elimination of VDI by the G406R mutation in the α11.2 subunit of Cav1.2. Here, we show that a single (A1929P) or a double mutation (H1926A-H1927A) within the CaN-binding site at the human C-terminal tail of α11.2, accelerate the inactivation rate and enhances VDI of both wt and Timothy channels. These results identify the CaN-binding site as the long-sought VDI-regulatory motif of the cardiac channel. The substantial increase in VDI and the accelerated inactivation caused by the selective inhibitors of CaN, cyclosporine A and FK-506, which act at the same CaN-binding site, further support this conclusion. A reversal of enhanced-sympathetic tone by VDI-enhancing CaN inhibitors could be beneficial for improving Timothy syndrome complications such as long-QT and autism.
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64
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Liu HB, Yang BF, Dong DL. Calcineurin and electrical remodeling in pathologic cardiac hypertrophy. Trends Cardiovasc Med 2011; 20:148-53. [PMID: 21742270 DOI: 10.1016/j.tcm.2010.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022]
Abstract
Calcineurin is a cytoplasmic Ca(2+)/calmodulin-dependent protein phosphatase that contributes to cardiac hypertrophy. Numerous studies have demonstrated that calcineurin/nuclear factor of activated T cell pathway affects the architecture of the heart under pathologic conditions, and the effects of calcineurin/nuclear factor of activated T cell pathway on cardiac hypertrophy have been well reviewed. Cardiac electrical remodeling is generally accompanied with the cardiac hypertrophy, and alteration of cardiac ion channel activity also leads to the changes of calcineurin activity and cardiac hypertrophy. Many studies have linked calcineurin with changes of a variety of ion channels, but the therapeutic approaches to target calcineurin for correcting cardiac electrical disturbance have not been formulated. Here, we review the recent progress in calcineurin and electrical remodeling in pathologic cardiac hypertrophy.
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Affiliation(s)
- Hui-Bin Liu
- Department of Pharmacology, Harbin Medical University, Harbin 150086, PR China
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65
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Heineke J, Ritter O. Cardiomyocyte calcineurin signaling in subcellular domains: from the sarcolemma to the nucleus and beyond. J Mol Cell Cardiol 2011; 52:62-73. [PMID: 22064325 DOI: 10.1016/j.yjmcc.2011.10.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 10/05/2011] [Accepted: 10/24/2011] [Indexed: 01/03/2023]
Abstract
The serine-threonine phosphatase calcineurin is activated in cardiac myocytes in the diseased heart and induces pathological hypertrophy. Calcineurin activity is mainly triggered by calcium/calmodulin binding but also through calpain mediated cleavage. How controlled calcineurin activation is possible in cardiac myocytes, which typically show a 10-fold difference in cytosolic calcium concentration with every heartbeat, has remained enigmatic. It is now emerging that calcineurin activation and signaling occur in subcellular microdomains, in which it is brought together with target proteins and exceedingly high concentrations of calcium in order to induce downstream signaling. We review current evidence of subcellular calcineurin mainly at the sarcolemma and the nucleus, but also in association with the sarcoplasmic reticulum and mitochondria. We also suggest that knowledge about subcellular signaling could help to develop inhibitors of calcineurin in specific microdomains to avoid side-effects that may arise from complete calcineurin inhibition.
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Affiliation(s)
- Joerg Heineke
- Medizinische Hochschule Hannover, Klinik für Kardiologie und Angiologie, Rebirth - Cluster of Excellence, Carl-Neuberg-Str.1, 30625 Hannover, Germany.
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66
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Shintani-Ishida K, Yoshida KI. Ischemia induces phospholamban dephosphorylation via activation of calcineurin, PKC-α, and protein phosphatase 1, thereby inducing calcium overload in reperfusion. Biochim Biophys Acta Mol Basis Dis 2011; 1812:743-51. [DOI: 10.1016/j.bbadis.2011.03.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 02/23/2011] [Accepted: 03/21/2011] [Indexed: 11/30/2022]
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67
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Saucerman JJ, Bers DM. Calmodulin binding proteins provide domains of local Ca2+ signaling in cardiac myocytes. J Mol Cell Cardiol 2011; 52:312-6. [PMID: 21708171 DOI: 10.1016/j.yjmcc.2011.06.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 05/24/2011] [Accepted: 06/02/2011] [Indexed: 11/25/2022]
Abstract
Calmodulin (CaM) acts as a common Ca(2+) sensor for many signaling pathways, transducing local Ca(2+) signals into specific cellular outcomes. Many of CaM's signaling functions can be explained by its unique biochemical properties, including high and low affinity Ca(2+)-binding sites with slow and fast kinetics, respectively. CaM is expected to have a limited spatial range of action, emphasizing its role in local Ca(2+) signaling. Interactions with target proteins further fine-tune CaM signal transduction. Here, we focus on only three specific cellular targets for CaM signaling in cardiac myocytes: the L-type Ca(2+) channel, the ryanodine receptor, and the IP(3) receptor. We elaborate a working hypothesis that each channel is regulated by two distinct functional populations of CaM: dedicated CaM and promiscuous CaM. Dedicated CaM is typically tethered to each channel and directly regulates channel activity. In addition, a local pool of promiscuous CaM appears poised to sense local Ca(2+) signals and trigger downstream pathways such as Ca(2+)/CaM dependent-protein kinase II and calcineurin. Understanding how promiscuous CaM coordinates multiple distinct signaling pathways remains a challenge, but is aided by the use of mathematical modeling and a new generation of fluorescent biosensors. This article is part of a special issue entitled "Local Signaling in Myocytes."
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Affiliation(s)
- Jeffrey J Saucerman
- Department of Biomedical Engineering, Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
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68
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Nejatbakhsh N, Feng ZP. Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases. Acta Pharmacol Sin 2011; 32:741-8. [PMID: 21642945 DOI: 10.1038/aps.2011.64] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.
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69
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Unraveling the secrets of a double life: contractile versus signaling Ca2+ in a cardiac myocyte. J Mol Cell Cardiol 2011; 52:317-22. [PMID: 21600216 DOI: 10.1016/j.yjmcc.2011.05.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 04/27/2011] [Accepted: 05/03/2011] [Indexed: 11/21/2022]
Abstract
No other inorganic molecule known in biology is considered as versatile as Ca(2+). In a vast majority of cell types, Ca(2+) acts as a universal second messenger underlying critical cellular processes varying from gene transcription to cell death. Although the role of Ca(2+) in myocyte contraction has been known for over a century, it was only more recently that this divalent cation has been implicated in mediating reactive signal transduction to promote cardiac hypertrophy. However, it remains unclear how Ca(2+)-dependent signaling pathways are regulated/activated in a cardiac myocyte given the prevailing conditions throughout the cytosol where Ca(2+) concentration oscillates between 100 nM and upwards of 1-2 μM during each contractile cycle. In this review we will examine three hypotheses put forward to explain how Ca(2+) might still function as a hypertrophic signaling molecule in cardiac myocytes and discuss the current literature that supports each of these views. This article is part of a special issue entitled "Local Signaling in Myocytes."
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70
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Three 4-letter words of hypertension-related cardiac hypertrophy: TRPC, mTOR, and HDAC. J Mol Cell Cardiol 2011; 50:964-71. [PMID: 21320507 DOI: 10.1016/j.yjmcc.2011.02.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 01/26/2011] [Accepted: 02/02/2011] [Indexed: 12/12/2022]
Abstract
Left ventricular hypertrophy due to hypertension represents a major risk factor for adverse cardiovascular events and death. In recent years, the prevalence of cardiac hypertrophy has increased due to obesity and an aging population. Notably, a significant number of individuals have persistent cardiac hypertrophy in the face of blood pressure that is normalized by drug treatment. Thus, a better understanding of the processes underlying the cardiac remodeling events that are set into play by hypertension is needed. At the level of the cardiac myocytes, hypertrophic growth is often described as physiological, as occurs with exercise, or pathological, as seen with hypertension. Here we discuss recent developments in three areas that are fundamental to pathological hypertrophic growth of cardiac myocytes. These areas are the transient receptor potential canonical (TRPC) channels, mammalian target of rapamycin (mTOR) complexes, and histone deacetylase (HDAC) enzymes. In the last several years, studies in each of these areas have yielded new and exciting discoveries into the genesis of pathological growth of cardiac myocytes. The phosphoinositide 3-kinase-Akt signaling network may be the common denominator that links these areas together. Defining the interrelationship among TRPC channels, mTOR signaling, and HDAC enzymes is a promising, but challenging area of research. Such knowledge will undoubtedly lead to new drugs that better prevent or reverse left ventricular hypertension.
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Abstract
During the last 15 years, the perception of the cardiac z-disc has undergone substantial changes. Initially viewed as a structural component at the lateral boundaries of the sarcomere, the cardiac z-disc has increasingly become recognized as a nodal point in cardiomyocyte signal transduction and disease. This minireview thus focuses on novel components and recent developments in z-disc biology and their role in cardiac signaling and disease.
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Affiliation(s)
- Derk Frank
- Internal Medicine III/Cardiology, University of Kiel, 24105 Kiel, Germany
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72
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Barry SP, Townsend PA. What causes a broken heart--molecular insights into heart failure. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 284:113-79. [PMID: 20875630 DOI: 10.1016/s1937-6448(10)84003-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Our understanding of the molecular processes which regulate cardiac function has grown immeasurably in recent years. Even with the advent of β-blockers, angiotensin inhibitors and calcium modulating agents, heart failure (HF) still remains a seriously debilitating and life-threatening condition. Here, we review the molecular changes which occur in the heart in response to increased load and the pathways which control cardiac hypertrophy, calcium homeostasis, and immune activation during HF. These can occur as a result of genetic mutation in the case of hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) or as a result of ischemic or hypertensive heart disease. In the majority of cases, calcineurin and CaMK respond to dysregulated calcium signaling and adrenergic drive is increased, each of which has a role to play in controlling blood pressure, heart rate, and left ventricular function. Many major pathways for pathological remodeling converge on a set of transcriptional regulators such as myocyte enhancer factor 2 (MEF2), nuclear factors of activated T cells (NFAT), and GATA4 and these are opposed by the action of the natriuretic peptides ANP and BNP. Epigenetic modification has emerged in recent years as a major influence cardiac physiology and histone acetyl transferases (HATs) and histone deacetylases (HDACs) are now known to both induce and antagonize hypertrophic growth. The newly emerging roles of microRNAs in regulating left ventricular dysfunction and fibrosis also has great potential for novel therapeutic intervention. Finally, we discuss the role of the immune system in mediating left ventricular dysfunction and fibrosis and ways this can be targeted in the setting of viral myocarditis.
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Affiliation(s)
- Seán P Barry
- Institute of Molecular Medicine, St. James's Hospital, Trinity College Dublin, Dublin 8, Ireland
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73
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Li Q, Sarna SK. Chronic stress targets posttranscriptional mechanisms to rapidly upregulate α1C-subunit of Cav1.2b calcium channels in colonic smooth muscle cells. Am J Physiol Gastrointest Liver Physiol 2011; 300:G154-63. [PMID: 21051529 PMCID: PMC3025508 DOI: 10.1152/ajpgi.00393.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chronic stress elevates plasma norepinephrine, which enhances expression of the α(1C)-subunit of Ca(v)1.2b channels in colonic smooth muscle cells within 1 h. Transcriptional upregulation usually does not explain such rapid protein synthesis. We investigated whether chronic stress-induced release of norepinephrine utilizes posttranscriptional mechanisms to enhance the α(1C)-subunit. We performed experiments on colonic circular smooth muscle strips and in conscious rats, using a 9-day chronic intermittent stress protocol. Incubation of rat colonic muscularis externa with norepinephrine enhanced α(1C)-protein expression within 45 min, without a concomitant increase in α(1C) mRNA, indicating posttranscriptional regulation of α(1C)-protein by norepinephrine. We found that norepinephrine activates the PI3K/Akt/GSK-3β pathway to concurrently enhance α(1C)-protein translation and block its polyubiquitination and proteasomal degradation. Incubation of colonic muscularis externa with norepinephrine or LiCl, which inhibits GSK-3β, enhanced p-GSK-3β and α(1C)-protein time dependently. Using enrichment of phosphoproteins and ubiquitinated proteins, we found that both norepinephrine and LiCl decrease α(1C) phosphorylation and polyubiquitination. Concurrently, they suppress eIF2α (Ser51) phosphorylation and 4E-BP1 expression, which stimulates gene-specific translation. The antagonism of two upstream kinases, PI3K and Akt, inhibits the induction of α(1C)-protein by norepinephrine. Cyanopindolol (β(3)-AR-antagonist) almost completely suppresses and propranolol (β(1/2)-AR antagonist) partially suppresses norepinephrine-induced α(1C)-protein expression, whereas phentolamine and prazosin (α-AR and α(1)-AR antagonist, respectively) have no significant effect. Experiments in conscious animals showed that chronic stress activates the PI3K/Akt/GSK-3β signaling. We conclude that norepinephrine released by chronic stress rapidly enhances the protein expression of α(1C)-subunit of Ca(v)1.2b channels by concurrently suppressing its degradation and enhancing translation of existing transcripts to maintain homeostasis.
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Affiliation(s)
| | - Sushil K. Sarna
- 1Department of Internal Medicine and ,2Department of Neuroscience and Cell Biology, The University of Texas Medical Branch at Galveston, Galveston, Texas
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74
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Xu H, Ginsburg KS, Hall DD, Zimmermann M, Stein IS, Zhang M, Tandan S, Hill JA, Horne MC, Bers D, Hell JW. Targeting of protein phosphatases PP2A and PP2B to the C-terminus of the L-type calcium channel Ca v1.2. Biochemistry 2010; 49:10298-307. [PMID: 21053940 PMCID: PMC3075818 DOI: 10.1021/bi101018c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The L-type Ca(2+) channel Ca(v)1.2 forms macromolecular signaling complexes that comprise the β(2) adrenergic receptor, trimeric G(s) protein, adenylyl cyclase, and cAMP-dependent protein kinase (PKA) for efficient signaling in heart and brain. The protein phosphatases PP2A and PP2B are part of this complex. PP2A counteracts increase in Ca(v)1.2 channel activity by PKA and other protein kinases, whereas PP2B can either augment or decrease Ca(v)1.2 currents in cardiomyocytes depending on the precise experimental conditions. We found that PP2A binds to two regions in the C-terminus of the central, pore-forming α(1) subunit of Ca(v)1.2: one region spans residues 1795-1818 and the other residues 1965-1971. PP2B binds immediately downstream of residue 1971. Injection of a peptide that contained residues 1965-1971 and displaced PP2A but not PP2B from endogenous Ca(v)1.2 increased basal and isoproterenol-stimulated L-type Ca(2+) currents in acutely isolated cardiomyocytes. Together with our biochemical data, these physiological results indicate that anchoring of PP2A at this site of Ca(v)1.2 in the heart negatively regulates cardiac L-type currents, likely by counterbalancing basal and stimulated phosphorylation that is mediated by PKA and possibly other kinases.
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Affiliation(s)
- Hui Xu
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA
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Del Duca D, Tadevosyan A, Karbassi F, Akhavein F, Vaniotis G, Rodaros D, Villeneuve LR, Allen BG, Nattel S, Rohlicek CV, Hébert TE. Hypoxia in early life is associated with lasting changes in left ventricular structure and function at maturity in the rat. Int J Cardiol 2010; 156:165-73. [PMID: 21131074 DOI: 10.1016/j.ijcard.2010.10.135] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 10/29/2010] [Indexed: 11/19/2022]
Abstract
BACKGROUND There is a growing population of adults with repaired cyanotic congenital heart disease. These patients have increased risk of impaired cardiac health and premature death. We hypothesized that hypoxia in early life before surgical intervention causes lasting changes in left ventricular structure and function with physiological implications in later life. METHODS Sprague-Dawley rats reared initially hypoxic conditions (FiO(2)=0.12) for days 1-10 of life were compared to rats reared only in ambient air. Cellular morphology and viability were compared among LV cardiomyocytes and histological analyses were performed on LV myocardium and arterioles. Intracellular calcium transients and cell shortening were measured in freshly-isolated cardiomyocytes, and mitochondrial hexokinase 2 (HK2) expression and activity were determined. Transthoracic echocardiography was used to assess LV function in anesthetized animals. RESULTS Cardiomyocytes from adult animals following hypoxia in early life had greater cellular volumes but significantly reduced viability. Echocardiographic analyses revealed LV hypertrophy and diastolic dysfunction, and alterations in cardiomyocyte calcium transients and cell shortening suggested impaired diastolic calcium reuptake. Histological analyses revealed significantly greater intima-media thickness and decreased lumen area in LV arterioles from hypoxic animals. Alterations in mitochondrial HK2 protein distribution and activity were also observed which may contribute to cardiomyocyte fragility. CONCLUSIONS Hypoxia in early life causes lasting changes in left ventricular structure and function that may negatively influence myocardial and vascular responses to physiological stress in later life. These data have implications for the growing population of adults with repaired or palliated cyanotic congenital heart disease.
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Affiliation(s)
- Danny Del Duca
- Division of Cardiovascular Surgery, Montréal Children's Hospital-McGill University Health Centre, Canada
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76
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Chen X, Nakayama H, Zhang X, Ai X, Harris DM, Tang M, Zhang H, Szeto C, Stockbower K, Berretta RM, Eckhart AD, Koch WJ, Molkentin JD, Houser SR. Calcium influx through Cav1.2 is a proximal signal for pathological cardiomyocyte hypertrophy. J Mol Cell Cardiol 2010; 50:460-70. [PMID: 21111744 DOI: 10.1016/j.yjmcc.2010.11.012] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 10/21/2010] [Accepted: 11/11/2010] [Indexed: 01/20/2023]
Abstract
Pathological cardiac hypertrophy (PCH) is associated with the development of arrhythmia and congestive heart failure. While calcium (Ca(2+)) is implicated in hypertrophic signaling pathways, the specific role of Ca(2+) influx through the L-type Ca(2+) channel (I(Ca-L)) has been controversial and is the topic of this study. To determine if and how sustained increases in I(Ca-L) induce PCH, transgenic mouse models with low (LE) and high (HE) expression levels of the β2a subunit of Ca(2+) channels (β2a) and in cultured adult feline (AF) and neonatal rat (NR) ventricular myocytes (VMs) infected with an adenovirus containing a β2a-GFP were used. In vivo, β2a LE and HE mice had increased heart weight to body weight ratio, posterior wall and interventricular septal thickness, tissue fibrosis, myocyte volume, and cross-sectional area and the expression of PCH markers in a time- and dose-dependent manner. PCH was associated with a hypercontractile phenotype including enhanced I(Ca-L), fractional shortening, peak Ca(2+) transient, at the myocyte level, greater ejection fraction, and fractional shortening at the organ level. In addition, LE mice had an exaggerated hypertrophic response to transverse aortic constriction. In vitro overexpression of β2a in cultured AFVMs increased I(Ca-L), cell volume, protein synthesis, NFAT, and HDAC translocations and in NRVMs increased surface area. These effects were abolished by the blockade of I(Ca-L), intracellular Ca(2+), calcineurin, CaMKII, and SERCA. In conclusion, increasing I(Ca-L) is sufficient to induce PCH through the calcineurin/NFAT and CaMKII/HDAC pathways. Both cytosolic and SR/ER-nuclear envelop Ca(2+) pools were shown to be involved.
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Affiliation(s)
- Xiongwen Chen
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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Krishna A, Sun L, Valderrábano M, Palade PT, Clark JW. Modeling CICR in rat ventricular myocytes: voltage clamp studies. Theor Biol Med Model 2010; 7:43. [PMID: 21062495 PMCID: PMC3245510 DOI: 10.1186/1742-4682-7-43] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 11/10/2010] [Indexed: 01/08/2023] Open
Abstract
Background The past thirty-five years have seen an intense search for the molecular mechanisms underlying calcium-induced calcium-release (CICR) in cardiac myocytes, with voltage clamp (VC) studies being the leading tool employed. Several VC protocols including lowering of extracellular calcium to affect Ca2+ loading of the sarcoplasmic reticulum (SR), and administration of blockers caffeine and thapsigargin have been utilized to probe the phenomena surrounding SR Ca2+ release. Here, we develop a deterministic mathematical model of a rat ventricular myocyte under VC conditions, to better understand mechanisms underlying the response of an isolated cell to calcium perturbation. Motivation for the study was to pinpoint key control variables influencing CICR and examine the role of CICR in the context of a physiological control system regulating cytosolic Ca2+ concentration ([Ca2+]myo). Methods The cell model consists of an electrical-equivalent model for the cell membrane and a fluid-compartment model describing the flux of ionic species between the extracellular and several intracellular compartments (cell cytosol, SR and the dyadic coupling unit (DCU), in which resides the mechanistic basis of CICR). The DCU is described as a controller-actuator mechanism, internally stabilized by negative feedback control of the unit's two diametrically-opposed Ca2+ channels (trigger-channel and release-channel). It releases Ca2+ flux into the cyto-plasm and is in turn enclosed within a negative feedback loop involving the SERCA pump, regulating[Ca2+]myo. Results Our model reproduces measured VC data published by several laboratories, and generates graded Ca2+ release at high Ca2+ gain in a homeostatically-controlled environment where [Ca2+]myo is precisely regulated. We elucidate the importance of the DCU elements in this process, particularly the role of the ryanodine receptor in controlling SR Ca2+ release, its activation by trigger Ca2+, and its refractory characteristics mediated by the luminal SR Ca2+ sensor. Proper functioning of the DCU, sodium-calcium exchangers and SERCA pump are important in achieving negative feedback control and hence Ca2+ homeostasis. Conclusions We examine the role of the above Ca2+ regulating mechanisms in handling various types of induced disturbances in Ca2+ levels by quantifying cellular Ca2+ balance. Our model provides biophysically-based explanations of phenomena associated with CICR generating useful and testable hypotheses.
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Affiliation(s)
- Abhilash Krishna
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA.
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78
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Xu KY, Zhu W, Xiao RP. Serine496 of β2 subunit of L-type Ca2+ channel participates in molecular crosstalk between activation of (Na++K+)-ATPase and the channel. Biochem Biophys Res Commun 2010; 402:319-23. [PMID: 20937253 DOI: 10.1016/j.bbrc.2010.10.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 11/29/2022]
Abstract
Activation of (Na++K+)-ATPase (NKA) regulates cardiac L-type Ca2+ channel (LTCC) function through molecular crosstalk. The mechanism underlying NKA-LTCC crosstalk remains poorly understood. We have previously shown that activation of NKA leads to phosphorylation of LTCC α1 Ser1928. Here we investigated whether LTCC β2 subunit is modulated by NKA activation and found that LTCC β2 Ser496 is phosphorylated in response to activation of NKA. Src inhibitor PP1 and Erk1/2 inhibitor PD98059 abolish LTCC β2 Ser496 phosphorylation, suggesting that NKA-mediated β2 Ser496 phosphorylation is dependent of Src/Erk1/2 signaling pathway. Protein kinase G (PKG) inhibitor KT5823 failed to inhibit the phosphorylation of β2 Ser496, indicating that the NKA-LTCC crosstalk is independent of PKG activity. The results of nifedipine sensitive 45Ca influx experiments suggest that phosphorylation of β2 Ser496 may play a key down-regulation role in attenuating the accelerated activity of α1 subunit of the channel. Ouabain does not cause a phosphorylation on β2 Ser496, indicating a fundamental difference between activation and inhibition of NKA-mediated biological processes. This study provides the first evidence to demonstrate that LTCC β2 subunit is coupled with the movement of signals in the mechanism of activation of NKA-mediated crosstalk with LTCC.
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Affiliation(s)
- Kai Y Xu
- Department of Surgery, Division of Cardiac Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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beta-Amyloid disrupts activity-dependent gene transcription required for memory through the CREB coactivator CRTC1. J Neurosci 2010; 30:9402-10. [PMID: 20631169 DOI: 10.1523/jneurosci.2154-10.2010] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activity-dependent gene expression mediating changes of synaptic efficacy is important for memory storage, but the mechanisms underlying gene transcriptional changes in age-related memory disorders are poorly understood. In this study, we report that gene transcription mediated by the cAMP-response element binding protein (CREB)-regulated transcription coactivator CRTC1 is impaired in neurons and brain from an Alzheimer's disease (AD) transgenic mouse expressing the human beta-amyloid precursor protein (APP(Sw,Ind)). Suppression of CRTC1-dependent gene transcription by beta-amyloid (Abeta) in response to cAMP and Ca(2+) signals is mediated by reduced calcium influx and disruption of PP2B/calcineurin-dependent CRTC1 dephosphorylation at Ser151. Consistently, expression of CRTC1 or active CRTC1 S151A and calcineurin mutants reverse the deficits on CRTC1 transcriptional activity in APP(Sw,Ind) neurons. Inhibition of calcium influx by pharmacological blockade of L-type voltage-gated calcium channels (VGCCs), but not by blocking NMDA or AMPA receptors, mimics the decrease on CRTC1 transcriptional activity observed in APP(Sw,Ind) neurons, whereas agonists of L-type VGCCs reverse efficiently these deficits. Consistent with a role of CRTC1 on Abeta-induced synaptic and memory dysfunction, we demonstrate a selective reduction of CRTC1-dependent genes related to memory (Bdnf, c-fos, and Nr4a2) coinciding with hippocampal-dependent spatial memory deficits in APP(Sw,Ind) mice. These findings suggest that CRTC1 plays a key role in coupling synaptic activity to gene transcription required for hippocampal-dependent memory, and that Abeta could disrupt cognition by affecting CRTC1 function.
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Nichols CB, Rossow CF, Navedo MF, Westenbroek RE, Catterall WA, Santana LF, McKnight GS. Sympathetic stimulation of adult cardiomyocytes requires association of AKAP5 with a subpopulation of L-type calcium channels. Circ Res 2010; 107:747-56. [PMID: 20671242 DOI: 10.1161/circresaha.109.216127] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
RATIONALE Sympathetic stimulation of the heart increases the force of contraction and rate of ventricular relaxation by triggering protein kinase (PK)A-dependent phosphorylation of proteins that regulate intracellular calcium. We hypothesized that scaffolding of cAMP signaling complexes by AKAP5 is required for efficient sympathetic stimulation of calcium transients. OBJECTIVE We examined the function of AKAP5 in the β-adrenergic signaling cascade. METHODS AND RESULTS We used calcium imaging and electrophysiology to examine the sympathetic response of cardiomyocytes isolated from wild type and AKAP5 mutant animals. The β-adrenergic regulation of calcium transients and the phosphorylation of substrates involved in calcium handling were disrupted in AKAP5 knockout cardiomyocytes. The scaffolding protein, AKAP5 (also called AKAP150/79), targets adenylyl cyclase, PKA, and calcineurin to a caveolin 3-associated complex in ventricular myocytes that also binds a unique subpopulation of Ca(v)1.2 L-type calcium channels. Only the caveolin 3-associated Ca(v)1.2 channels are phosphorylated by PKA in response to sympathetic stimulation in wild-type heart. However, in the AKAP5 knockout heart, the organization of this signaling complex is disrupted, adenylyl cyclase 5/6 no longer associates with caveolin 3 in the T-tubules, and noncaveolin 3-associated calcium channels become phosphorylated after β-adrenergic stimulation, although this does not lead to an enhanced calcium transient. The signaling domain created by AKAP5 is also essential for the PKA-dependent phosphorylation of ryanodine receptors and phospholamban. CONCLUSIONS These findings identify an AKAP5-organized signaling module that is associated with caveolin 3 and is essential for sympathetic stimulation of the calcium transient in adult heart cells.
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Affiliation(s)
- C Blake Nichols
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
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81
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Heineke J, Auger-Messier M, Correll RN, Xu J, Benard MJ, Yuan W, Drexler H, Parise LV, Molkentin JD. CIB1 is a regulator of pathological cardiac hypertrophy. Nat Med 2010; 16:872-9. [PMID: 20639889 PMCID: PMC2917617 DOI: 10.1038/nm.2181] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 06/15/2010] [Indexed: 11/30/2022]
Abstract
Hypertrophic heart disease is a leading health problem facing the Western world. Here we identified the small EF-hand domain-containing protein CIB1 (Ca2+ and integrin binding protein 1) in a screen for novel regulators of cardiomyocyte hypertrophy. Yeast two-hybrid screening for CIB1 interacting partners identified a related EF-hand domain-containing protein calcineurin B, the regulatory subunit of the pro-hypertrophic protein phosphatase calcineurin. CIB1 largely localizes to the sarcolemma in mouse and human myocardium, where it anchors calcineurin to control its activation in coordination with the L-type Ca2+ channel. CIB1 protein levels and membrane association were enhanced in cardiac pathological hypertrophy, but not in physiological hypertrophy. Consistent with these observations, mice lacking Cib1 show a dramatic reduction in myocardial hypertrophy, fibrosis, cardiac dysfunction, and calcineurin-NFAT activity following pressure overload, while the degree of physiologic hypertrophy after swimming was not altered. Transgenic mice with inducible and cardiac-specific overexpression of CIB1 showed enhanced cardiac hypertrophy in response to pressure overload or calcineurin signaling. Moreover, mice lacking the Ppp3cb gene showed no enhancement in cardiac hypertrophy associated with CIB1 overexpression. Thus, CIB1 functions as a novel regulator of cardiac hypertrophy through its ability to regulate calcineurin sarcolemmal association and activation.
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Affiliation(s)
- Joerg Heineke
- Howard Hughes Medical Institute, Department of Pediatrics, University of Cincinnati, Cincinnati, OH, USA.
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82
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Xu L, Lai D, Cheng J, Lim HJ, Keskanokwong T, Backs J, Olson EN, Wang Y. Alterations of L-type calcium current and cardiac function in CaMKII{delta} knockout mice. Circ Res 2010; 107:398-407. [PMID: 20538682 DOI: 10.1161/circresaha.110.222562] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Recent studies have highlighted important roles of CaMKII in regulating Ca(2+) handling and excitation-contraction coupling. However, the cardiac effect of chronic CaMKII inhibition has not been well understood. OBJECTIVE We have tested the alterations of L-type calcium current (I(Ca)) and cardiac function in CaMKIIdelta knockout (KO) mouse left ventricle (LV). METHODS AND RESULTS We used the patch-clamp method to record I(Ca) in ventricular myocytes and found that in KO LV, basal I(Ca) was significantly increased without changing the transmural gradient of I(Ca) distribution. Substitution of Ba(2+) for Ca(2+) showed similar increase in I(Ba). There was no change in the voltage dependence of I(Ca) activation and inactivation. I(Ca) recovery from inactivation, however, was significantly slowed. In KO LV, the Ca(2+)-dependent I(Ca) facilitation (CDF) and I(Ca) response to isoproterenol (ISO) were significantly reduced. However, ISO response was reversed by beta2-adrenergic receptor (AR) inhibition. Western blots showed a decrease in beta1-AR and an increase in Ca(v)1.2, beta2-AR, and Galphai3 protein levels. Ca(2+) transient and sarcomere shortening in KO myocytes were unchanged at 1-Hz but reduced at 3-Hz stimulation. Echocardiography in conscious mice revealed an increased basal contractility in KO mice. However, cardiac reserve to work load and beta-adrenergic stimulation was reduced. Surprisingly, KO mice showed a reduced heart rate in response to work load or beta-adrenergic stimulation. CONCLUSIONS Our results implicate physiological CaMKII activity in maintaining normal I(Ca), Ca(2+) handling, excitation-contraction coupling, and the in vivo heart function in response to cardiac stress.
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Affiliation(s)
- Lin Xu
- Department of Pediatrics and Children's Healthcare of Atlanta, Emory University, GA, USA
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83
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Affiliation(s)
- John D Scott
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA.
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84
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Wang Y, Hill JA. Electrophysiological remodeling in heart failure. J Mol Cell Cardiol 2010; 48:619-32. [PMID: 20096285 DOI: 10.1016/j.yjmcc.2010.01.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 11/25/2022]
Abstract
Heart failure affects nearly 6 million Americans, with a half-million new cases emerging each year. Whereas up to 50% of heart failure patients die of arrhythmia, the diverse mechanisms underlying heart failure-associated arrhythmia are poorly understood. As a consequence, effectiveness of antiarrhythmic pharmacotherapy remains elusive. Here, we review recent advances in our understanding of heart failure-associated molecular events impacting the electrical function of the myocardium. We approach this from an anatomical standpoint, summarizing recent insights gleaned from pre-clinical models and discussing their relevance to human heart failure.
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Affiliation(s)
- Yanggan Wang
- Department of Pediatrics, Emory University, Atlanta, GA, USA.
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85
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Maillet M, Davis J, Auger-Messier M, York A, Osinska H, Piquereau J, Lorenz JN, Robbins J, Ventura-Clapier R, Molkentin JD. Heart-specific deletion of CnB1 reveals multiple mechanisms whereby calcineurin regulates cardiac growth and function. J Biol Chem 2009; 285:6716-24. [PMID: 20037164 PMCID: PMC2825466 DOI: 10.1074/jbc.m109.056143] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Calcineurin is a protein phosphatase that is uniquely regulated by sustained increases in intracellular Ca2+ following signal transduction events. Calcineurin controls cellular proliferation, differentiation, apoptosis, and inducible gene expression following stress and neuroendocrine stimulation. In the adult heart, calcineurin regulates hypertrophic growth of cardiomyocytes in response to pathologic insults that are associated with altered Ca2+ handling. Here we determined that calcineurin signaling is directly linked to the proper control of cardiac contractility, rhythm, and the expression of Ca2+-handling genes in the heart. Our approach involved a cardiomyocyte-specific deletion using a CnB1-LoxP-targeted allele in mice and three different cardiac-expressing Cre alleles/transgenes. Deletion of calcineurin with the Nkx2.5-Cre knock-in allele resulted in lethality at 1 day after birth due to altered right ventricular morphogenesis, reduced ventricular trabeculation, septal defects, and valvular overgrowth. Slightly later deletion of calcineurin with the α-myosin heavy chain Cre transgene resulted in lethality in early mid adulthood that was characterized by substantial reductions in cardiac contractility, severe arrhythmia, and reduced myocyte content in the heart. Young calcineurin heart-deleted mice died suddenly after pressure overload stimulation or neuroendocrine agonist infusion, and telemetric monitoring of older mice showed arrhythmia leading to sudden death. Mechanistically, loss of calcineurin reduced expression of key Ca2+-handling genes that likely lead to arrhythmia and reduced contractility. Loss of calcineurin also directly impacted cellular proliferation in the postnatal developing heart. These results reveal multiple mechanisms whereby calcineurin regulates cardiac development and myocyte contractility.
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Affiliation(s)
- Marjorie Maillet
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, Ohio 45229-3039, USA
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Koitabashi N, Aiba T, Hesketh GG, Rowell J, Zhang M, Takimoto E, Tomaselli GF, Kass DA. Cyclic GMP/PKG-dependent inhibition of TRPC6 channel activity and expression negatively regulates cardiomyocyte NFAT activation Novel mechanism of cardiac stress modulation by PDE5 inhibition. J Mol Cell Cardiol 2009; 48:713-24. [PMID: 19961855 DOI: 10.1016/j.yjmcc.2009.11.015] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Revised: 10/28/2009] [Accepted: 11/19/2009] [Indexed: 12/15/2022]
Abstract
Increased cyclic GMP from enhanced synthesis or suppressed catabolism (e.g. PDE5 inhibition by sildenafil, SIL) activates protein kinase G (PKG) and blunts cardiac pathological hypertrophy. Suppressed calcineurin (Cn)-NFAT (nuclear factor of activated T-cells) signaling appears to be involved, though it remains unclear how this is achieved. One potential mechanism involves activation of Cn/NFAT by calcium entering via transient receptor potential canonical (TRPC) channels (notably TRPC6). Here, we tested the hypothesis that PKG blocks Cn/NFAT activation by modifying and thus inhibiting TRPC6 current to break the positive feedback loop involving NFAT and NFAT-dependent TRPC6 upregulation. TRPC6 expression rose with pressure-overload in vivo, and angiotensin (ATII) or endothelin (ET1) stimulation in neonatal and adult cardiomyocytes in vitro. 8Br-cGMP and SIL reduced ET1-stimulated TRPC6 expression and NFAT dephosphorylation (activity). TRPC6 upregulation was absent if its promoter was mutated with non-functional NFAT binding sites, whereas constitutively active NFAT triggered TRPC6 expression that was not inhibited by SIL. PKG phosphorylated TRPC6, and both T70 and S322 were targeted. Both sites were functionally relevant, as 8Br-cGMP strongly suppressed current in wild-type TRPC6 channels, but not in those with phospho-silencing mutations (T70A, S322A or S322Q). NFAT activation and increased protein synthesis stimulated by ATII or ET1 was blocked by 8Br-cGMP or SIL. However, transfection with T70A or S322Q TRPC6 mutants blocked this inhibitory effect, whereas phospho-mimetic mutants (T70E, S322E, and both combined) suppressed NFAT activation. Thus PDE5-inhibition blocks TRPC6 channel activation and associated Cn/NFAT activation signaling by PKG-dependent channel phosphorylation.
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Affiliation(s)
- Norimichi Koitabashi
- Division of Cardiology, Ross 858, Department of Medicine, Johns Hopkins University Medical Institutions, 720 Rutland Avenue, Baltimore, MD 21205, USA
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