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Kim Y, Ko TH, Jin C, Zhang Y, Kang HR, Ma R, Li H, Choi JI, Han K. The emerging roles of Shank3 in cardiac function and dysfunction. Front Cell Dev Biol 2023; 11:1191369. [PMID: 37187620 PMCID: PMC10175600 DOI: 10.3389/fcell.2023.1191369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 04/17/2023] [Indexed: 05/17/2023] Open
Abstract
Shank3 is a member of the Shank family proteins (Shank1-3), which are abundantly present in the postsynaptic density (PSD) of neuronal excitatory synapses. As a core scaffold in the PSD, Shank3 plays a critical role in organizing the macromolecular complex, ensuring proper synaptic development and function. Clinically, various mutations of the SHANK3 gene are causally associated with brain disorders such as autism spectrum disorders and schizophrenia. However, recent in vitro and in vivo functional studies and expression profiling in various tissues and cell types suggest that Shank3 also plays a role in cardiac function and dysfunction. For example, Shank3 interacts with phospholipase Cβ1b (PLCβ1b) in cardiomyocytes, regulating its localization to the sarcolemma and its role in mediating Gq-induced signaling. In addition, changes in cardiac morphology and function associated with myocardial infarction and aging have been investigated in a few Shank3 mutant mouse models. This review highlights these results and potential underlying mechanisms, and predicts additional molecular functions of Shank3 based on its protein interactors in the PSD, which are also highly expressed and function in the heart. Finally, we provide perspectives and possible directions for future studies to better understand the roles of Shank3 in the heart.
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Affiliation(s)
- Yoonhee Kim
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
| | - Tae Hee Ko
- Division of Cardiology, Department of Internal Medicine, Korea University College of Medicine and Korea University Anam Hospital, Seoul, Republic of Korea
| | - Chunmei Jin
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science, Daejeon, Republic of Korea
| | - Yinhua Zhang
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
| | - Hyae Rim Kang
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
- BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea
| | - Ruiying Ma
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
- BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea
| | - Huiling Li
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
- BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea
| | - Jong-Il Choi
- Division of Cardiology, Department of Internal Medicine, Korea University College of Medicine and Korea University Anam Hospital, Seoul, Republic of Korea
- BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea
- *Correspondence: Jong-Il Choi, ; Kihoon Han,
| | - Kihoon Han
- Department of Neuroscience, Korea University College of Medicine, Seoul, Republic of Korea
- BK21 Graduate Program, Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Republic of Korea
- *Correspondence: Jong-Il Choi, ; Kihoon Han,
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2
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Wang Y, Xu Y, Guo W, Fang Y, Hu L, Wang R, Zhao R, Guo D, Qi B, Ren G, Ren J, Li Y, Zhang M. Ablation of Shank3 alleviates cardiac dysfunction in aging mice by promoting CaMKII activation and Parkin-mediated mitophagy. Redox Biol 2022; 58:102537. [PMID: 36436456 PMCID: PMC9709154 DOI: 10.1016/j.redox.2022.102537] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 11/08/2022] [Indexed: 11/19/2022] Open
Abstract
Compromised mitophagy and mitochondrial homeostasis are major contributors for the etiology of cardiac aging, although the precise underlying mechanisms remains elusive. Shank3, a heart-enriched protein, has recently been reported to regulate aging-related neurodegenerative diseases. This study aimed to examine the role of Shank3 in the pathogenesis of cardiac senescence and the possible mechanisms involved. Cardiac-specific conditional Shank3 knockout (Shank3CKO) mice were subjected to natural aging. Mitochondrial function and mitophagy activity were determined in vivo, in mouse hearts and in vitro, in cardiomyocytes. Here, we showed that cardiac Shank3 expression exhibited a gradual increase during the natural progression of the aging, accompanied by overtly decreased mitophagy activity and a decline in cardiac function. Ablation of Shank3 promoted mitophagy, reduced mitochondria-derived superoxide (H2O2 and O2•-) production and apoptosis, and protected against cardiac dysfunction in the aged heart. In an in vitro study, senescent cardiomyocytes treated with D-gal exhibited reduced mitophagy and significantly elevated Shank3 expression. Shank3 knock-down restored mitophagy, leading to increased mitochondrial membrane potential, decreased mitochondrial oxidative stress, and reduced apoptosis in senescent cardiomyocytes, whereas Shank3 overexpression mimicked D-gal-induced mitophagy inhibition and mitochondrial dysfunction in normally cultured cardiomyocytes. Mechanistically, the IP assay revealed that Shank3 directly binds to CaMKII, and this interaction was further increased in the aged heart. Enhanced Shank3/CaMKII binding impedes mitochondrial translocation of CaMKII, resulting in the inhibition of parkin-mediated mitophagy, which ultimately leads to mitochondrial dysfunction and cardiac damage in the aged heart. Our study identified Shank3 as a novel contributor to aging-related cardiac damage. Manipulating Shank3/CaMKII-induced mitophagy inhibition could thus be an optional strategy for therapeutic intervention in clinical aging-related cardiac dysfunctions.
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Affiliation(s)
- Ying Wang
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Yuerong Xu
- Department of Orthodontics, School of Stomatology, Air Force Medical University, Xi’an, 710032, China
| | - Wangang Guo
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Yexian Fang
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Lang Hu
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Runze Wang
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Ran Zhao
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Dong Guo
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Bingchao Qi
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Gaotong Ren
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China
| | - Jun Ren
- Department of Cardiology and Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, Shanghai, China,Corresponding author. Department of Cardiology and Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, Shanghai, China.
| | - Yan Li
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China,Corresponding author.
| | - Mingming Zhang
- Department of Cardiology, Tangdu Hospital, Air Force Medical University, Xi’an, 710038, China,Corresponding author.
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Tappia PS, Ramjiawan B, Dhalla NS. Role of Phospholipase C in Catecholamine-induced Increase in Myocardial Protein Synthesis. Can J Physiol Pharmacol 2022; 100:945-955. [PMID: 35767883 DOI: 10.1139/cjpp-2022-0189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The activation of the α1-adrenoceptor-(α1-AR) by norepinephrine results in the G-protein (Gqα) mediated increase in the phosphoinositide-specific phospholipase C (PLC) activity. The byproducts of PLC hydrolytic activity, namely, 1,2-diacylglycerol and inositol-1,4,5-trisphosphate, are important downstream signal transducers for increased protein synthesis in the cardiomyocyte and the subsequent hypertrophic response. In this article, evidence is outlined to demonstrate the role of cardiomyocyte PLC isozymes in the catecholamine-induced increase in protein synthesis by using a blocker of α1-AR and an inhibitor of PLC. The discussion will be focused on the α1-AR-Gqα-PLC-mediated hypertrophic signaling pathway from the viewpoint that it may compliment the other β1-AR-Gs protein-adenylyl cyclase signal transduction mechanisms in the early stages of cardiac hypertrophy development, but may become more relevant at the late stage of cardiac hypertrophy. From the information provided here, it is suggested that some specific PLC isozymes may potentially serve as important targets for the attenuation of cardiac hypertrophy in the vulnerable patient population at-risk for heart failure.
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Affiliation(s)
- Paramjit S Tappia
- Asper Clinical Research Institute, St. Boniface Hospital, Office of Clinical Research, Winnipeg, Manitoba, Canada;
| | - Bram Ramjiawan
- University of Manitoba, Faculty of Medicine, Winnipeg, Manitoba, Canada;
| | - Naranjan S Dhalla
- St Boniface Hospital Research, 120927, Institute of Cardiovascular Sciences, Albrechtsen Research Centre, Winnipeg, Manitoba, Canada;
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4
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Zhou J, Singh N, Monnier C, Marszalec W, Gao L, Jin J, Frisk M, Louch WE, Verma S, Krishnamurthy P, Nico E, Mulla M, Aistrup GL, Kishore R, Wasserstrom JA. Phosphatidylinositol-4,5-Bisphosphate Binding to Amphiphysin-II Modulates T-Tubule Remodeling: Implications for Heart Failure. Front Physiol 2022; 12:782767. [PMID: 35002765 PMCID: PMC8733645 DOI: 10.3389/fphys.2021.782767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/19/2021] [Indexed: 11/13/2022] Open
Abstract
BIN1 (amphyphysin-II) is a structural protein involved in T-tubule (TT) formation and phosphatidylinositol-4,5-bisphosphate (PIP2) is responsible for localization of BIN1 to sarcolemma. The goal of this study was to determine if PIP2-mediated targeting of BIN1 to sarcolemma is compromised during the development of heart failure (HF) and is responsible for TT remodeling. Immunohistochemistry showed co-localization of BIN1, Cav1.2, PIP2, and phospholipase-Cβ1 (PLCβ1) in TTs in normal rat and human ventricular myocytes. PIP2 levels were reduced in spontaneously hypertensive rats during HF progression compared to age-matched controls. A PIP Strip assay of two native mouse cardiac-specific isoforms of BIN1 including the longest (cardiac BIN1 #4) and shortest (cardiac BIN1 #1) isoforms as well human skeletal BIN1 showed that all bound PIP2. In addition, overexpression of all three BIN1 isoforms caused tubule formation in HL-1 cells. A triple-lysine motif in a short loop segment between two helices was mutated and replaced by negative charges which abolished tubule formation, suggesting a possible location for PIP2 interaction aside from known consensus binding sites. Pharmacological PIP2 depletion in rat ventricular myocytes caused TT loss and was associated with changes in Ca2+ release typically found in myocytes during HF, including a higher variability in release along the cell length and a slowing in rise time, time to peak, and decay time in treated myocytes. These results demonstrate that depletion of PIP2 can lead to TT disruption and suggest that PIP2 interaction with cardiac BIN1 is required for TT maintenance and function.
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Affiliation(s)
- Junlan Zhou
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Neha Singh
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Chloe Monnier
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - William Marszalec
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Li Gao
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Jing Jin
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Michael Frisk
- Institute for Experimental Medical Research (IEMR), Oslo University Hospital, Oslo, Norway.,K. G. Jebsen Cardiac Research Center, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research (IEMR), Oslo University Hospital, Oslo, Norway.,K. G. Jebsen Cardiac Research Center, University of Oslo, Oslo, Norway
| | - Suresh Verma
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Prasanna Krishnamurthy
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Elsa Nico
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Maaz Mulla
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Gary L Aistrup
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Raj Kishore
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - J Andrew Wasserstrom
- Department of Medicine (Cardiology), Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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5
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Tappia P, Elimban V, Dhalla N. Involvement of phospholipase C in the norepinephrine-induced hypertrophic response in Cardiomyocytes. SCRIPTA MEDICA 2022. [DOI: 10.5937/scriptamed53-36527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Norepinephrine (NE) is known to mediate cardiomyocyte hypertrophy through the G protein coupled a1 -adrenoceptor (a1 -AR) and the activation of the phosphoinositide-specific phospholipase C (PLC). Since the by-products of PLC activity are important downstream signal transducers for cardiac hypertrophy, the role of and the regulatory mechanisms involved in the activation of PLC isozymes in cardiac hypertrophy are highlighted in this review. The discussion is focused to underscore PLC in different experimental models of cardiac hypertrophy, as well as in isolated adult and neonatal cardiomyocytes treated with NE. Particular emphasis is laid concerning the a1 -AR-PLC-mediated hypertrophic signalling pathway. From the information provided, it is evident that the specific activation of PLC isozymes is a primary signalling event in the a1 -AR mediated response to NE as well as initiation and progression of cardiac hypertrophy. Furthermore, the possibility of PLC involvement in the perpetuation of cardiac hypertrophy is also described. It is suggested that specific PLC isozymes may serve as viable targets for the prevention of cardiac hypertrophy in patient population at-risk for the development of heart failure.
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Katan M, Cockcroft S. Phospholipase C families: Common themes and versatility in physiology and pathology. Prog Lipid Res 2020; 80:101065. [PMID: 32966869 DOI: 10.1016/j.plipres.2020.101065] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/14/2020] [Accepted: 09/17/2020] [Indexed: 12/20/2022]
Abstract
Phosphoinositide-specific phospholipase Cs (PLCs) are expressed in all mammalian cells and play critical roles in signal transduction. To obtain a comprehensive understanding of these enzymes in physiology and pathology, a detailed structural, biochemical, cell biological and genetic information is required. In this review, we cover all these aspects to summarize current knowledge of the entire superfamily. The families of PLCs have expanded from 13 enzymes to 16 with the identification of the atypical PLCs in the human genome. Recent structural insights highlight the common themes that cover not only the substrate catalysis but also the mechanisms of activation. This involves the release of autoinhibitory interactions that, in the absence of stimulation, maintain classical PLC enzymes in their inactive forms. Studies of individual PLCs provide a rich repertoire of PLC function in different physiologies. Furthermore, the genetic studies discovered numerous mutated and rare variants of PLC enzymes and their link to human disease development, greatly expanding our understanding of their roles in diverse pathologies. Notably, substantial evidence now supports involvement of different PLC isoforms in the development of specific cancer types, immune disorders and neurodegeneration. These advances will stimulate the generation of new drugs that target PLC enzymes, and will therefore open new possibilities for treatment of a number of diseases where current therapies remain ineffective.
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Affiliation(s)
- Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, 21 University Street, London WC1E 6JJ, UK.
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7
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Nash CA, Wei W, Irannejad R, Smrcka AV. Golgi localized β1-adrenergic receptors stimulate Golgi PI4P hydrolysis by PLCε to regulate cardiac hypertrophy. eLife 2019; 8:48167. [PMID: 31433293 PMCID: PMC6726460 DOI: 10.7554/elife.48167] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 08/21/2019] [Indexed: 12/25/2022] Open
Abstract
Increased adrenergic tone resulting from cardiovascular stress leads to development of heart failure, in part, through chronic stimulation of β1 adrenergic receptors (βARs) on cardiac myocytes. Blocking these receptors is part of the basis for β-blocker therapy for heart failure. Recent data demonstrate that G protein-coupled receptors (GPCRs), including βARs, are activated intracellularly, although the biological significance is unclear. Here we investigated the functional role of Golgi βARs in rat cardiac myocytes and found they activate Golgi localized, prohypertrophic, phosphoinositide hydrolysis, that is not accessed by cell surface βAR stimulation. This pathway is accessed by the physiological neurotransmitter norepinephrine (NE) via an Oct3 organic cation transporter. Blockade of Oct3 or specific blockade of Golgi resident β1ARs prevents NE dependent cardiac myocyte hypertrophy. This clearly defines a pathway activated by internal GPCRs in a biologically relevant cell type and has implications for development of more efficacious β-blocker therapies.
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Affiliation(s)
- Craig A Nash
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Wenhui Wei
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Roshanak Irannejad
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | - Alan V Smrcka
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
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Compartmentalized cyclic nucleotides have opposing effects on regulation of hypertrophic phospholipase Cε signaling in cardiac myocytes. J Mol Cell Cardiol 2018; 121:51-59. [PMID: 29885334 DOI: 10.1016/j.yjmcc.2018.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 05/12/2018] [Accepted: 06/05/2018] [Indexed: 12/11/2022]
Abstract
In cardiac myocytes activation of an exchange factor activated by cAMP (Epac) leads to activation of phospholipase Cε (PLCε)-dependent hydrolysis of phosphatidylinositol 4-phosphate (PI4P) in the Golgi apparatus a process critical for development of cardiac hypertrophy. Here we show that β-adrenergic receptor (βAR) stimulation does not stimulate this pathway in the presence of the broad spectrum phosphodiesterase (PDE) inhibitor IBMX, but selective PDE3 inhibition revealed βAR-dependent PI4P depletion. On the other hand, selective inhibition of PDE2 or PDE9A blocked endothelin-1 (ET-1) and cAMP-dependent PI4P hydrolysis by PLCε. Direct activation of protein kinase A (PKA), protein kinase G (PKG), or the atrial natriuretic factor (ANF) receptor abolished PI4P hydrolysis in response to multiple upstream stimuli. These results reveal distinct pools of cyclic nucleotides that either inhibit PLCε at the Golgi through PKA/PKG, or activate PLCε at the Golgi through Epac. These data together reveal a new mechanism by which ANF and selective PDE inhibitors can protect against cardiac hypertrophy.
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9
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Smrcka AV. Regulation of phosphatidylinositol-specific phospholipase C at the nuclear envelope in cardiac myocytes. J Cardiovasc Pharmacol 2016; 65:203-10. [PMID: 25658460 DOI: 10.1097/fjc.0000000000000195] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate hydrolysis at the plasma membrane by phospholipase C is one of the major hormone regulated intracellular signaling systems. The system generates the diffusible second messenger IP3 and the membrane bound messenger diacylglycerol. Spatial regulation of this system has been thought to be through specific subcellular distributions of the IP3 receptor or PKC. As is becoming increasingly apparent, receptor-stimulated signaling systems are also found at intracellular membranes. As discussed in this issue, G protein-coupled receptors have been identified at the nuclear envelope implying intracellular localization of the signaling systems that respond to G protein-coupled receptors. Here, we discuss the evidence for the existence of PLC signals that regulate nuclear processes, as well as the evidence for nuclear and nuclear envelope localization of PLC signaling components, and their implications for cardiac physiology and disease.
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Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY
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Expressing an inhibitor of PLCβ1b sustains contractile function following pressure overload. J Mol Cell Cardiol 2016; 93:12-7. [PMID: 26906633 DOI: 10.1016/j.yjmcc.2016.02.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 01/29/2016] [Accepted: 02/17/2016] [Indexed: 01/19/2023]
Abstract
The activity of phospholipase Cβ1b (PLCβ1b) is selectively elevated in failing myocardium and cardiac expression of PLCβ1b causes contractile dysfunction. PLCβ1b can be selectively inhibited by expressing a peptide inhibitor that prevents sarcolemmal localization. The inhibitory peptide, PLCβ1b-CT was expressed in heart from a mini-gene using adeno-associated virus (rAAV6-PLCβ1b-CT). rAAV6-PLCβ1b-CT, or blank virus, was delivered IV (4×10(9)vg/g body weight) and trans-aortic-constriction (TAC) or sham-operation was performed 8weeks later. Expression of PLCβ1b-CT prevented the loss of contractile function, eliminated lung congestion and improved survival following TAC with either a 'moderate' or 'severe' pressure gradient. Hypertrophy was attenuated but not eliminated. Expression of the PLCβ1b-CT peptide 2-3weeks after TAC reduced contractile dysfunction and lung congestion, without limiting hypertrophy. PLCβ1b inhibition ameliorates pathological responses following acute pressure overload. The targeting of PLCβ1b to the sarcolemma provides the basis for the development of a new class of inotropic agent.
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Genetic variants in PLCB4/PLCB1 as susceptibility loci for coronary artery aneurysm formation in Kawasaki disease in Han Chinese in Taiwan. Sci Rep 2015; 5:14762. [PMID: 26434682 PMCID: PMC4593004 DOI: 10.1038/srep14762] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 09/04/2015] [Indexed: 12/17/2022] Open
Abstract
Kawasaki disease (KD) is an acute, inflammatory, and self-limited vasculitis affecting infants and young children. Coronary artery aneurysm (CAA) formation is the major complication of KD and the leading cause of acquired cardiovascular disease among children. To identify susceptible loci that might predispose patients with KD to CAA formation, a genome-wide association screen was performed in a Taiwanese KD cohort. Patients with both KD and CAA had longer fever duration and delayed intravenous immunoglobulin treatment time. After adjusting for these factors, 100 susceptibility loci were identified. Four genes were identified from a single cluster of 35 using the Ingenuity Pathway Analysis (IPA) Knowledge Base. Silencing KCNQ5, PLCB1, PLCB4, and PLCL1 inhibited the effect of lipopolysaccharide-induced endothelial cell inflammation with varying degrees of proinflammatory cytokine expression. PLCB1 showed the most significant inhibition. Endothelial cell inflammation was also inhibited by using a phospholipase C (PLC) inhibitor. The single nucleotide polymorphism rs6140791 was identified between PLCB4 and PLCB1. Plasma PLC levels were higher in patients with KD and CC+CG rs6140791genotypes, and these genotypes were more prevalent in patients with KD who also had CAA. Our results suggest that polymorphism of the PLCB4/B1 genes might be involved in the CAA pathogenesis of KD.
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12
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Grubb DR, Luo J, Woodcock EA. Phospholipase Cβ1b directly binds the SH3 domain of Shank3 for targeting and activation in cardiomyocytes. Biochem Biophys Res Commun 2015; 461:519-24. [DOI: 10.1016/j.bbrc.2015.04.060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 04/10/2015] [Indexed: 12/24/2022]
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13
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Grubb DR, Crook B, Ma Y, Luo J, Qian HW, Gao XM, Kiriazis H, Du XJ, Gregorevic P, Woodcock EA. The atypical 'b' splice variant of phospholipase Cβ1 promotes cardiac contractile dysfunction. J Mol Cell Cardiol 2015; 84:95-103. [PMID: 25918049 DOI: 10.1016/j.yjmcc.2015.04.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 04/16/2015] [Accepted: 04/20/2015] [Indexed: 10/23/2022]
Abstract
The activity of the early signaling enzyme, phospholipase Cβ1b (PLCβ1b), is selectively elevated in diseased myocardium and activity increases with disease progression. We aimed to establish the contribution of heightened PLCβ1b activity to cardiac pathology. PLCβ1b, the alternative splice variant, PLCβ1a, and a blank virus were expressed in mouse hearts using adeno-associated viral vectors (rAAV6-FLAG-PLCβ1b, rAAV6-FLAG-PLCβ1a, or rAAV6-blank) delivered intravenously (IV). Following viral delivery, FLAG-PLCβ1b was expressed in all of the chambers of the mouse heart and was localized to the sarcolemma. Heightened PLCβ1b expression caused a rapid loss of contractility, 4-6 weeks, that was fully reversed, within 5 days, by inhibition of protein kinase Cα (PKCα). PLCβ1a did not localize to the sarcolemma and did not affect contractile function. Expression of PLCβ1b, but not PLCβ1a, caused downstream dephosphorylation of phospholamban and depletion of the Ca(2+) stores of the sarcoplasmic reticulum. We conclude that heightened PLCβ1b activity observed in diseased myocardium contributes to pathology by PKCα-mediated contractile dysfunction. PLCβ1b is a cardiac-specific signaling system, and thus provides a potential therapeutic target for the development of well-tolerated inotropic agents for use in failing myocardium.
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Affiliation(s)
- David R Grubb
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Bryony Crook
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Yi Ma
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Jieting Luo
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Hong Wei Qian
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Xiao-Ming Gao
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Helen Kiriazis
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Xiao-Jun Du
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia
| | - Elizabeth A Woodcock
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, 3004 Victoria, Australia.
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Klenke S, Rump K, Buschkamp K, Engler A, Peters J, Siffert W, Frey UH. Characterization of the PLCB1 promoter and regulation by early growth response transcription factor EGR-1. Eur J Pharmacol 2014; 742:8-14. [PMID: 25192965 DOI: 10.1016/j.ejphar.2014.08.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 08/21/2014] [Accepted: 08/25/2014] [Indexed: 10/24/2022]
Abstract
The Gαq/-Gα11-PLCβ1 pathway is important for intracellular signalling and associated with pathological conditions, such as cardiac hypertrophy. The GNAQ and GNA11 promoters (encoding for Gαq and Gα11) have already been characterized and are both regulated by the transcription factor early growth response 1 (Egr-1). In contrast, the PLCB1 promoter (encoding for the direct downstream effector PLCβ1) has neither been cloned nor characterized. Therefore, the purpose of this study was to 1) characterize the PLCB1 promoter, and 2) assess its potential regulation by Egr-1. By means of 5'- Rapid Amplification of 5'-cDNA ends analysis in human heart tissue we found an initiation of transcription from multiple starting points, the main transcription starting point being located at nt-235 relative to the translation start point. The PLCB1 promoter was cloned and deletion constructs were generated. Luciferase assays were performed in three different cell lines and regulatory regions were identified between nt-595/nt-313 (Hek293: P=0.013; HASMC: P=0.019; H9c2: P=0.005). In electrophoretic mobility shift assays one specific Egr-1 binding site was identified at nt-451/-419 and PLCB1 promoter activity was increased more than 5-fold (Hek293: P=0.0008) and 1,6- fold (H9c2: P=0.0499) following overexpression of Egr-1. Thus, the PLCB1 promoter was characterized for the first time and a specific interaction with the transcription factor Egr-1 was shown. Our data provide a potential molecular mechanism relating to pathophysiological conditions such as cardiac hypertrophy where activation by Egr-1 of Gαq/Gα11-PLCβ1 plays an important role.
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Affiliation(s)
- Stefanie Klenke
- Institut für Pharmakogenetik, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany; Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany.
| | - Katharina Rump
- Institut für Pharmakogenetik, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany; Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
| | - Kai Buschkamp
- Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
| | - Andrea Engler
- Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
| | - Jürgen Peters
- Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
| | - Winfried Siffert
- Institut für Pharmakogenetik, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
| | - Ulrich H Frey
- Klinik für Anästhesiologie & Intensivmedizin, Universität Duisburg-Essen and Universitätsklinikum Essen, Hufelandstr. 55, D-45122 Essen, Germany
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15
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Cooley N, Grubb DR, Luo J, Woodcock EA. The phosphatidylinositol(4,5)bisphosphate-binding sequence of transient receptor potential channel canonical 4α is critical for its contribution to cardiomyocyte hypertrophy. Mol Pharmacol 2014; 86:399-405. [PMID: 25049082 DOI: 10.1124/mol.114.093690] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Cardiomyocyte hypertrophy requires a source of Ca(2+) distinct from the Ca(2+) that regulates contraction. The canonical transient receptor potential channel (TrpC) family, a family of cation channels regulated by activation of phospholipase C (PLC), has been implicated in this response. Cardiomyocyte hypertrophy downstream of Gq-coupled receptors is mediated specifically by PLCβ1b that is scaffolded onto a SH3 and ankyrin repeat protein 3 (Shank3) complex at the sarcolemma. TrpC4 exists as two splice variants (TrpC4α and TrpC4β) that differ only in an 84-residue sequence that binds to phosphatidylinositol(4,5)bisphosphate (PIP2), the substrate of PLCβ1b. In neonatal rat cardiomyocytes, TrpC4α, but not TrpC4β, coimmunoprecipitated with both PLCβ1b and Shank3. Heightened PLCβ1b expression caused TrpC4α, but not TrpC4β, translocation to the sarcolemma, where it colocalized with PLCβ1b. When overexpressed in cardiomyocytes, TrpC4α, but not TrpC4β, increased cell area (893 ± 18 to 1497 ± 29 mm(2), P < 0.01) and marker gene expression (atrial natriuretic peptide increased by 409 ± 32%, and modulatory calcineurin inhibitory protein 1 by 315 ± 28%, P < 0.01). Dominant-negative TrpC4 reduced hypertrophy initiated by PLCβ1b, or PLCβ1b-coupled receptor activation, by 72 ± 8% and 39 ± 5 %, respectively. We conclude that TrpC4α is selectively involved in mechanisms downstream of PLCβ1b culminating in cardiomyocyte hypertrophy, and that the hypertrophic response is dependent on the TrpC4α splice variant-specific sequence that binds to PIP2.
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Affiliation(s)
- Nicola Cooley
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - David R Grubb
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Jieting Luo
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Elizabeth A Woodcock
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
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16
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Abstract
Phospholipase C (PLC) enzymes convert phosphatidylinositol-4,5-bisphosphate into the second messengers diacylglycerol and inositol-1,4,5-triphosphate. The production of these molecules promotes the release of intracellular calcium and activation of protein kinase C, which results in profound cellular changes. The PLCβ subfamily is of particular interest given its prominent role in cardiovascular and neuronal signaling and its regulation by G protein-coupled receptors, as PLCβ is the canonical downstream target of the heterotrimeric G protein Gαq. However, this is not the only mechanism regulating PLCβ activity. Extensive structural and biochemical evidence has revealed regulatory roles for autoinhibitory elements within PLCβ, Gβγ, small molecular weight G proteins, and the lipid membrane itself. Such complex regulation highlights the central role that this enzyme plays in cell signaling. A better understanding of the molecular mechanisms underlying the control of its activity will greatly facilitate the search for selective small molecule modulators of PLCβ.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, Michigan
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17
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Zhang L, Malik S, Pang J, Wang H, Park KM, Yule DI, Blaxall BC, Smrcka AV. Phospholipase Cε hydrolyzes perinuclear phosphatidylinositol 4-phosphate to regulate cardiac hypertrophy. Cell 2013; 153:216-27. [PMID: 23540699 DOI: 10.1016/j.cell.2013.02.047] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 01/22/2013] [Accepted: 02/14/2013] [Indexed: 01/08/2023]
Abstract
Phospholipase Cε (PLCε) is a multifunctional enzyme implicated in cardiovascular, pancreatic, and inflammatory functions. Here we show that conditional deletion of PLCε in mouse cardiac myocytes protects from stress-induced pathological hypertrophy. PLCε small interfering RNA (siRNA) in ventricular myocytes decreases endothelin-1 (ET-1)-dependent elevation of nuclear calcium and activation of nuclear protein kinase D (PKD). PLCε scaffolded to muscle-specific A kinase-anchoring protein (mAKAP), along with PKCε and PKD, localizes these components at or near the nuclear envelope, and this complex is required for nuclear PKD activation. Phosphatidylinositol 4-phosphate (PI4P) is identified as a perinuclear substrate in the Golgi apparatus for mAKAP-scaffolded PLCε. We conclude that perinuclear PLCε, scaffolded to mAKAP in cardiac myocytes, responds to hypertrophic stimuli to generate diacylglycerol (DAG) from PI4P in the Golgi apparatus, in close proximity to the nuclear envelope, to regulate activation of nuclear PKD and hypertrophic signaling pathways.
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Affiliation(s)
- Lianghui Zhang
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
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18
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Adjobo-Hermans MJ, Crosby KC, Putyrski M, Bhageloe A, van Weeren L, Schultz C, Goedhart J, Gadella TW. PLCβ isoforms differ in their subcellular location and their CT-domain dependent interaction with Gαq. Cell Signal 2013; 25:255-63. [DOI: 10.1016/j.cellsig.2012.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 09/08/2012] [Accepted: 09/16/2012] [Indexed: 11/15/2022]
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Mills KI, Anderson J, Levy PT, Cole FS, Silva JNA, Kulkarni S, Shinawi M. Duplication of 20p12.3 associated with familial Wolff-Parkinson-White syndrome. Am J Med Genet A 2012; 161A:137-44. [PMID: 23239491 DOI: 10.1002/ajmg.a.35701] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 09/01/2012] [Indexed: 01/19/2023]
Abstract
Wolff-Parkinson-White (WPW) syndrome is caused by preexcitation of the ventricular myocardium via an accessory pathway which increases the risk for paroxysmal supraventricular tachycardia. The condition is often sporadic and of unknown etiology in the majority of cases. Autosomal dominant inheritance and association with congenital heart defects or ventricular hypertrophy were described. Microdeletions of 20p12.3 have been associated with WPW syndrome with either cognitive dysfunction or Alagille syndrome. Here, we describe the association of 20p12.3 duplication with WPW syndrome in a patient who presented with non-immune hydrops. Her paternal uncle carries the duplication and has attention-deficit hyperactivity disorder and electrocardiographic findings consistent with WPW. The 769 kb duplication was detected by the Affymetrix Whole Genome-Human SNP Array 6.0 and encompasses two genes and the first two exons of a third gene. We discuss the potential role of the genes in the duplicated region in the pathogenesis of WPW and possible neurobehavioral abnormalities. Our data provide additional support for a significant role of 20p12.3 chromosomal rearrangements in the etiology of WPW syndrome.
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Affiliation(s)
- Kimberly I Mills
- Edward Mallinckrodt Department of Pediatrics, St. Louis Children's Hospital, St. Louis, MO, USA
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20
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Cellular neurochemical characterization and subcellular localization of phospholipase C β1 in rat brain. Neuroscience 2012; 222:239-68. [PMID: 22735577 DOI: 10.1016/j.neuroscience.2012.06.039] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 06/15/2012] [Accepted: 06/15/2012] [Indexed: 11/21/2022]
Abstract
The present study describes a complete and detailed neuroanatomical distribution map of the phospholipase C beta1 (PLCβ1) isoform along the adult rat neuraxis, and defines the phenotype of cells expressing PLCβ1, along with its subcellular localization in cortical neurons as assessed by double-immunofluorescence staining and confocal laser scanning. Immunohistochemical labeling revealed a considerable morphological heterogeneity among PLCβ1-positive cells in the cortex, even though there was a marked predominance of pyramidal morphologies. As an exception to the general non-matching distribution of GFAP and PLCβ1, a high degree of co-expression was observed in radial glia-like processes of the spinal cord white matter. In the somatosensory cortex, the proportion of GABAergic neurons co-stained with PLCβ1 was similar (around 2/3) in layers I, II-III, IV and VI, and considerably lower in layer V (around 2/5). Double immunofluorescence against PLCβ1 and nuclear speckle markers SC-35 and NeuN/Fox3 in isolated nuclei from the rat cortex showed a high overlap of both markers with PLCβ1 within the nuclear matrix. In contrast, there was no apparent co-localization with markers of the nuclear envelope and lamina. Finally, to assess whether the subcellular expression pattern of PLCβ1 involved specifically one of the two splice variants of PLCβ1, we carried out Western blot experiments in cortical subcellular fractions. Notably, PLCβ1a/1b ratios were statistically higher in the cytoplasm than in the nuclear and plasma membrane fractions. These results provide a deeper knowledge of the cellular distribution of the PLCβ1 isoform in different cell subtypes of the rat brain, and of its presence in the neuronal nuclear compartment.
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21
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Priest JR, Girirajan S, Vu TH, Olson A, Eichler EE, Portman MA. Rare copy number variants in isolated sporadic and syndromic atrioventricular septal defects. Am J Med Genet A 2012; 158A:1279-84. [PMID: 22529060 PMCID: PMC3564951 DOI: 10.1002/ajmg.a.35315] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 01/21/2012] [Indexed: 11/11/2022]
Abstract
Atrioventricular septal defects (AVSDs) are a frequent but not universal component of Down syndrome (DS), while AVSDs in otherwise normal individuals have no well-defined genetic basis. The contribution of copy number variation (CNV) to specific congenital heart disease (CHD) phenotypes including AVSD is unknown. We hypothesized that de novo CNVs on chromosome 21 might cause isolated sporadic AVSDs, and separately that CNVs throughout the genome might constitute an additional genetic risk factor for AVSD in patients with DS. We utilized a custom oligonucleotide arrays targeted to CNV hotspots that are flanked by large duplicated segments of high sequence identity. We assayed 29 euploid and 50 DS individuals with AVSD, and compared to general population controls. In patients with isolated-sporadic AVSD we identified two large unique deletions outside of chromosome 21 not seen in the expanded set of 8,635 controls, each overlapping with larger deletions associated with similar CHD reported in the DECIPHER database. There was a small duplication in one patient with DS and AVSD. We conclude that isolated sporadic AVSDs may be occasionally associated with large de novo genomic structural variation outside of chromosome 21. The absence of CNVs on chromosome 21 in patients with isolated sporadic AVSD suggests that sub-chromosomal duplications or deletions of greater than 150 kbp on chromosome 21 do not cause sporadic AVSDs. Large CNVs do not appear to be an additive risk factor for AVSD in the DS population.
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Affiliation(s)
- James R Priest
- Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, USA
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22
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Grubb DR, Luo J, Yu YL, Woodcock EA. Scaffolding protein Homer 1c mediates hypertrophic responses downstream of Gq in cardiomyocytes. FASEB J 2011; 26:596-603. [PMID: 22012123 DOI: 10.1096/fj.11-190330] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Activation of the heterotrimeric G protein, Gq, causes cardiomyocyte hypertrophy in vivo and in cell models. Responses to activated Gq in cardiomyocytes are mediated exclusively by phospholipase Cβ1b (PLCβ1b), because it localizes at the sarcolemma by binding to Shank3, a high-molecular-weight (MW) scaffolding protein. Shank3 can bind to the Homer family of low-MW scaffolding proteins that fine tune Ca(2+) signaling by facilitating crosstalk between Ca(2+) channels at the cell surface with those on intracellular Ca(2+) stores. Activation of α(1)-adrenergic receptors, expression of constitutively active Gαq (GαqQL), or PLCβ1b initiated cardiomyocyte hypertrophy and increased Homer 1c mRNA expression, by 1.6 ± 0.18-, 1.9 ± 0.17-, and 1.5 ± 0.07-fold, respectively (means ± se, 6 independent experiments, P<0.05). Expression of Homer 1c induced an increase in cardiomyocyte area from 853 ± 27 to 1146 ± 31 μm(2) (P<0.05); furthermore, expression of dominant-negative Homer (Homer 1a) reversed the increase in cell size caused by α(1)-adrenergic agonist or PLCβ1b treatment (1503±48 to 996±28 and 1626±48 to 828±31 μm(2), respectively, P<0.05). Homer proteins were localized near the sarcolemma, associated with Shank3 and phospholipase Cβ1b. We conclude that Gq-mediated hypertrophy involves activation of PLCβ1b scaffolded onto a Shank3/Homer complex. Signaling downstream of Homer 1c is necessary and sufficient for Gq-initiated hypertrophy.
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Affiliation(s)
- David R Grubb
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne,Victoria, Australia
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