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Cardiac-specific overexpression of Claudin-5 exerts protection against myocardial ischemia and reperfusion injury. Biochim Biophys Acta Mol Basis Dis 2022; 1868:166535. [PMID: 36058416 DOI: 10.1016/j.bbadis.2022.166535] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/25/2022] [Accepted: 08/25/2022] [Indexed: 11/23/2022]
Abstract
Claudin-5 has recently attracted increasing attention by its potential as a novel treatment target in the early stage of heart failure. However, whether Claudin-5 produces beneficial effects on myocardial ischemia and reperfusion (IR) injury has not been elucidated yet. In this study, we identified reduced levels of Claudin-5 in the hearts of mice subjected to acute myocardial IR injury and murine HL-1 cardiomyocytes subjected to hypoxia and reoxygenation (HR). We then constructed cardiac-specific Cldn5-overexpressing mice using an adeno-associated virus (AAV9) vector and demonstrated that Cldn5 overexpression ameliorated cardiac dysfunction and myocardial damage in mice subjected to myocardial IR injury. Moreover, Cldn5 overexpression attenuated myocardial oxidative stress (DHE and protein levels of Nrf2, HO-1, and NQO1), inflammatory response (levels of MPO, F4/80, Ly6C, and circulating inflammatory cells), mitochondrial dysfunction (protein levels of PGC-1α, NRF1, and TFAM), endoplasmic reticulum stress (protein levels of GRP78, ATF6, and CHOP and p-PERK), energy metabolism disorder (p-AMPK and ACC), and apoptosis (TUNEL assay and protein levels of Bax and Bcl2) in mice subjected to myocardial IR. Next, we generated Cldn5 knockdown cells by lentiviral shRNA and observed that Cldn5 knockdown inhibited cell viability and affected the expression or activation of these IR-related signalings in HL-1 cardiomyocytes subjected to HR. Mechanistically, SIRT1 was proved to be involved in regulating the expression of Claudin-5 by co-immunoprecipitation analysis and Sirt1 knockdown experiments. Our data demonstrated that targeting Claudin-5 may represent a promising approach for preventing and treating acute myocardial IR injury.
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2
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Yang Y, Zhou Q, Gao A, Chen L, Li L. Endoplasmic reticulum stress and focused drug discovery in cardiovascular disease. Clin Chim Acta 2020; 504:125-137. [PMID: 32017925 DOI: 10.1016/j.cca.2020.01.031] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 01/29/2020] [Accepted: 01/29/2020] [Indexed: 12/28/2022]
Abstract
Endoplasmic reticulum (ER) is an intracellular membranous organelle involved in the synthesis, folding, maturation and post-translation modification of secretory and transmembrane proteins. Therefore, ER is closely related to the maintenance of intracellular homeostasis and the good balance between health and diseases. Endoplasmic reticulum stress (ERS) occurs when unfolded/misfolded proteins accumulate after disturbance of ER environment. In response to ERS, cells trigger an adaptive response called the Unfolded protein response (UPR), which helps cells cope with the stress. In recent years, a large number of studies show that ERS can aggravate cardiovascular diseases. ERS-related proteins expression in cardiovascular diseases is on the rise. Therefore, down-regulation of ERS is critical for alleviating symptoms of cardiovascular diseases, which may be used in the near future to treat cardiovascular diseases. This article reviews the relationship between ERS and cardiovascular diseases and drugs that inhibit ERS. Furthermore, we detail the role of ERS inhibitors in the treatment of cardiovascular disease. Drugs that inhibit ERS are considered as promising strategies for the treatment of cardiovascular diseases.
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Affiliation(s)
- Yiyuan Yang
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang 421001, China
| | - Qionglin Zhou
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang 421001, China
| | - Anbo Gao
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang 421001, China
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang 421001, China.
| | - Lanfang Li
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang 421001, China.
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3
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Choy KW, Murugan D, Mustafa MR. Natural products targeting ER stress pathway for the treatment of cardiovascular diseases. Pharmacol Res 2018; 132:119-129. [PMID: 29684674 DOI: 10.1016/j.phrs.2018.04.013] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 03/06/2018] [Accepted: 04/16/2018] [Indexed: 12/22/2022]
Abstract
Endoplasmic reticulum (ER) is the main organelle for the synthesis, folding, and processing of secretory and transmembrane proteins. Pathological stimuli including hypoxia, ischaemia, inflammation and oxidative stress interrupt the homeostatic function of ER, leading to accumulation of unfolded proteins, a condition referred to as ER stress. ER stress triggers a complex signalling network referred as the unfolded protein response (UPR). Extensive studies have demonstrated that ER stress plays an important role in the pathogenesis of various cardiovascular diseases such as heart failure, ischemic heart disease and atherosclerosis. The importance of natural products in modern medicine are well recognized and continues to be of interests as a source of novel lead compounds. Natural products targeting components of UPR and reducing ER stress offers an innovative strategic approach to treat cardiovascular diseases. In this review, we discussed several therapeutic interventions using natural products with potential cardiovascular protective properties targeting ER stress signalling pathways.
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Affiliation(s)
- Ker Woon Choy
- Department of Pharmacology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Dharmani Murugan
- Department of Pharmacology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Mohd Rais Mustafa
- Department of Pharmacology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Natural Products Research and Drug Discovery (CENAR), University of Malaya, 50603 Kuala Lumpur, Malaysia.
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4
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Wu C, Dong S, Li Y. Effects of miRNA-455 on cardiac hypertrophy induced by pressure overload. Int J Mol Med 2015; 35:893-900. [PMID: 25695617 PMCID: PMC4356433 DOI: 10.3892/ijmm.2015.2105] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 02/11/2015] [Indexed: 01/15/2023] Open
Abstract
microRNAs (miRNAs or miRs) are essential in cardiac hypertrophy and in the development of heart failure. In the present study, we aimed to determine whether the restoration of miRNA-455 (miR-455) gene expression in vivo aggravates hypertrophy, but protects against adverse cardiac remodeling induced by pressure overload. Cardiac hypertrophy was induced by left ventricular pressure overload in male mice subjected to transverse aortic constriction (TAC). The mice were randomly selected to receive a tail vein injection of either miR-455 or green fluorescent protein per animal at 1, 8, 15 and 21 days following surgery. Cardiac hypertrophy, function and remodeling were evaluated by echocardiography, catheterization, histological analysis and the examination of the expression of specific genes and cardiac apoptosis. TAC (2 weeks following surgery) resulted in significant cardiac hypertrophy, which was significantly aggravated by treatment with miR-455. However, miR-455 replacement therapy markedly reduced myocardial fibrosis and inhibited apoptosis, suggesting that this therapy can prevent maladaptive ventricular remodeling. miR-455 was also identified and validated to target calreticulin, a protein that is critical for cardiac development. The restoration of miR-455 gene expression may thus be a potential therapeutic strategy to reverse pressure-induced cardiac hypertrophy and prevent maladaptive cardiac remodeling through the regulation of miR-455 at different time points following hypertrophy.
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Affiliation(s)
- Chuntao Wu
- Intensive Care Unit, The Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Shimin Dong
- Intensive Care Unit, The Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Yongjun Li
- Department of Cardiology, The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
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5
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The Protective Effect of Lacidipine on Myocardial Remodeling Is Mediated by the Suppression in Expression of GPR78 and CHOP in Rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2015; 2015:945076. [PMID: 25688281 PMCID: PMC4320802 DOI: 10.1155/2015/945076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 12/18/2014] [Accepted: 12/19/2014] [Indexed: 11/22/2022]
Abstract
Lacidipine (LAC) is now widely used for the treatment of hypertension and further can prevent cardiac hypertrophy and remodeling. However, the underlying mechanism has not been fully understood. In this study, we examined the protective effects of LAC on cardiac remodeling in spontaneously hypertensive rats (SHR) and investigated the possible mechanism. Four weeks after administration of the designated drugs, blood pressure, left ventricular mass index (LVMI), and rterial pressure (MAP) were measured. The endoplasmic reticulum stress (ERS) parameters such as GRP78 and CHOP expressions in cardiomyocytes were also detected by immunohistochemistry. Results showed that the MAP in 0.36 and 0.72 mg/kg LAC groups was markedly lowered compared with that of the SHR control group (P < 0.01 or P < 0.05). Moreover, 0.72 mg/kg LAC could also significantly decrease the LVMI (P < 0.05). Simultaneously, the results of immunohistochemistry demonstrated that the expression of GRP78 and CHOP was significantly decreased by 0.72 mg/kg LAC (P < 0.05), respectively. Our present study suggested that LAC could lower blood pressure and could prevent left ventricular hypertrophy accompanied by inhibiting expression of GRP78 and CHOP in ERS.
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Chidiac P, Sobiesiak AJ, Lee KN, Gros R, Nguyen CH. The eIF2B-interacting domain of RGS2 protects against GPCR agonist-induced hypertrophy in neonatal rat cardiomyocytes. Cell Signal 2014; 26:1226-34. [PMID: 24576550 DOI: 10.1016/j.cellsig.2014.02.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 02/05/2014] [Accepted: 02/11/2014] [Indexed: 11/29/2022]
Abstract
The protective effect of Regulator of G protein Signaling 2 (RGS2) in cardiac hypertrophy is thought to occur through its ability to inhibit the chronic GPCR signaling that promotes pathogenic growth both in vivo and in cultured cardiomyocytes. However, RGS2 is known to have additional functions beyond its activity as a GTPase accelerating protein, such as the ability to bind to eukaryotic initiation factor, eIF2B, and inhibit protein synthesis. The RGS2 eIF2B-interacting domain (RGS2(eb)) was examined for its ability to regulate hypertrophy in neonatal ventricular myocytes. Both full-length RGS2 and RGS2(eb) were able to inhibit agonist-induced cardiomyocyte hypertrophy, but RGS2(eb) had no effect on receptor-mediated inositol phosphate production, cAMP production, or ERK 1/2 activation. These results suggest that the protective effects of RGS2 in cardiac hypertrophy may derive at least in part from its ability to govern protein synthesis.
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Affiliation(s)
- Peter Chidiac
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Alina J Sobiesiak
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Katherine N Lee
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Robert Gros
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Chau H Nguyen
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada; School of Pharmacy, D'Youville College, Buffalo, NY 14201, USA.
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7
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Lacidipine inhibits endoplasmic reticulum stress and myocardial remodeling induced by pressure overload in rat heart. Eur J Pharmacol 2013; 718:441-7. [DOI: 10.1016/j.ejphar.2013.07.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 07/10/2013] [Accepted: 07/16/2013] [Indexed: 11/23/2022]
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Millott R, Dudek E, Michalak M. The endoplasmic reticulum in cardiovascular health and disease. Can J Physiol Pharmacol 2012; 90:1209-17. [PMID: 22897133 DOI: 10.1139/y2012-058] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The endoplasmic reticulum has an intricate network of pathways built to deal with the secretory and integral membrane protein synthesis demands of the cell, as well as adaptive responses set up for the endoplasmic reticulum to rely on when stressed. These pathways are both essential and complex, and because of these 2 factors, several situations can lead to a dysfunctional endoplasmic reticulum and result in a dysfunctional cell with the potential to contribute to the progression of disease. The endoplasmic reticulum has been implicated in several metabolic, neurodegenerative, inflammatory, autoimmune, and renal diseases and disorders, and in particular, cardiovascular diseases. The role of the endoplasmic reticulum in cardiovascular disease shows how the change in function of a particular microscopic organelle can lead to macroscopic changes in the form of disease.
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Affiliation(s)
- Robyn Millott
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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9
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Park CS, Cha H, Kwon EJ, Sreenivasaiah PK, Kim DH. The chemical chaperone 4-phenylbutyric acid attenuates pressure-overload cardiac hypertrophy by alleviating endoplasmic reticulum stress. Biochem Biophys Res Commun 2012; 421:578-84. [PMID: 22525677 DOI: 10.1016/j.bbrc.2012.04.048] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 04/10/2012] [Indexed: 11/19/2022]
Abstract
Evidence has shown that endoplasmic reticulum stress (ERS) is associated with the pathogenesis of cardiac hypertrophy. The aim of this study was to investigate whether direct alleviation of ER stress by 4-phenylbutyric acid (PBA), a known chemical chaperone drug, could attenuate pressure-overload cardiac hypertrophy in mice. The effects of orally administered PBA (100mg/kg body weight daily for a week) were examined using mice undergoing transverse aortic constriction (TAC-mice), an animal model to produce pressure overload. TAC application for 1 week led to a 1.8-fold increase in the ratio of the heart weight over body weight (HW/BW) and up-regulation of the hypertrophy markers ANF and BNF accompanied by up-regulation of ERS markers (GRP78, p-PERK, and p-elF2α). The oral administration of PBA to the TAC-mice reduced hypertrophy (19%) and severely downregulated the fibrosis-related genes (transforming growth factor-β1, phospho-smad2, and pro-collagen isoforms). We conclude that ERS is induced as a consequence of remodeling during pathological hypertrophy and that PBA may help to relieve ERS and play a protective role against cardiac hypertrophy and possibly heart failure. We suggest PBA as a novel therapeutic agent for cardiac hypertrophy and fibrosis.
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Affiliation(s)
- Chang Sik Park
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro (1 Oryong-dong), Buk-gu, Gwangju 500-712, Republic of Korea
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10
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Dickhout JG, Carlisle RE, Austin RC. Interrelationship between cardiac hypertrophy, heart failure, and chronic kidney disease: endoplasmic reticulum stress as a mediator of pathogenesis. Circ Res 2011; 108:629-42. [PMID: 21372294 DOI: 10.1161/circresaha.110.226803] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Synthesis of transmembrane and secretory proteins occurs within the endoplasmic reticulum (ER) and is extremely important in the normal functioning of both the heart and kidney. The dysregulation of protein synthesis/processing within the ER causes the accumulation of unfolded proteins, thereby leading to ER stress and the activation of the unfolded protein response. Sarcoplasmic reticulum/ER Ca2+ disequilibrium can lead to cardiac hypertrophy via cytosolic Ca2+ elevation and stimulation of the Ca2+/calmodulin, calcineurin, NF-AT3 pathway. Although cardiac hypertrophy may be initially adaptive, prolonged or severe ER stress resulting from the increased protein synthesis associated with cardiac hypertrophy can lead to apoptosis of cardiac myocytes and result in reduced cardiac output and chronic heart failure. The failing heart has a dramatic effect on renal function because of inadequate perfusion and stimulates the release of many neurohumoral factors that may lead to further ER stress within the heart, including angiotensin II and arginine-vasopressin. Renal failure attributable to proteinuria and uremia also induces ER stress within the kidney, which contributes to the transformation of tubular epithelial cells to a fibroblast-like phenotype, fibrosis, and tubular cell apoptosis, further diminishing renal function. As a consequence, cardiorenal syndrome may develop into a vicious circle with poor prognosis. New therapeutic modalities to alleviate ER stress through stimulation of the cytoprotective components of the unfolded protein response, including GRP78 upregulation and eukaryotic initiation factor 2α phosphorylation, may hold promise to reduce the high morbidity and mortality associated with cardiorenal syndrome.
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Affiliation(s)
- Jeffrey G Dickhout
- Department of Medicine, Division of Nephrology McMaster University and St Joseph's Healthcare Hamilton, 50 Charlton Ave, East Hamilton, Ontario, Canada, L8N 4A6
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11
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Zhang ZY, Liu XH, Hu WC, Rong F, Wu XD. The calcineurin-myocyte enhancer factor 2c pathway mediates cardiac hypertrophy induced by endoplasmic reticulum stress in neonatal rat cardiomyocytes. Am J Physiol Heart Circ Physiol 2010; 298:H1499-509. [PMID: 20207814 DOI: 10.1152/ajpheart.00980.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endoplasmic reticulum (ER) stress (ERS) is involved in various cardiovascular diseases. Our previous study verified that ERS took part in the development of cardiac hypertrophy; however, its mechanism is still unclear. This study aimed to investigate the roles of the calcineurin (CaN) signal pathway in hypertrophy induced by the ERS inductor thapsigargin (TG) in neonatal cardiomyocytes from Sprague-Dawley rats. Investigation of ER chaperone expression, ER staining, and calreticulin immunofluorescence were used to detect the ERS response. mRNA expression of atrial natriuretic peptide and brain natriuretic peptide, total protein synthesis rate, and cell surface area were used to evaluate cardiac hypertrophy induced by TG. TG induced a significant ERS response along with hypertrophy in a dose- and time-dependent manner in cardiomyocytes, which was verified by treatment with tunicamycin, another ERS inducer. Furthermore, TG induced a significant elevation of the intracellular Ca(2+) level, CaN activation, and myocyte enhancer factor 2c (MEF2c) expression in a dose- and time-dependent manner in cardiomyocytes. Cyclosporine A, a CaN inhibitor, markedly suppressed MEF2c nuclear translocation and inhibited TG-induced hypertrophy. These results demonstrate that ERS induces cardiac hypertrophy and that the CaN-MEF2c pathway is involved in ERS-induced hypertrophy in cardiomyocytes.
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Affiliation(s)
- Zhen-Ying Zhang
- Department of Pathophysiology, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, China
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12
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Abstract
Over the last decade, it has become clear that the accumulation of misfolded proteins contributes to a number of neurodegenerative, immune, and endocrine pathologies, as well as other age-related illnesses. Recent interest has focused on the possibility that the accumulation of misfolded proteins can also contribute to vascular and cardiac diseases. In large part, the misfolding of proteins takes place during synthesis on free ribosomes in the cytoplasm or on endoplasmic reticulum ribosomes. In fact, even under optimal conditions, approximately 30% of all newly synthesized proteins are rapidly degraded, most likely because of improper folding. Accordingly, stresses that perturb the folding of proteins during or soon after synthesis can lead to the accumulation of misfolded proteins and to potential cellular dysfunction and pathological consequences. To avert such outcomes, cells have developed elaborate protein quality-control systems for detecting misfolded proteins and making appropriate adjustments to the machinery responsible for protein synthesis and/or degradation. Important contributors to protein quality control include cytosolic and organelle-targeted molecular chaperones, which help fold and stabilize proteins from unfolding, and the ubiquitin proteasome system, which degrades terminally misfolded proteins. Both of these systems play important roles in cardiovascular biology. The focus of this review is the endoplasmic reticulum stress response, a protein quality-control and signal-transduction system that has not been well studied in the context of cardiovascular biology but that could be important for vascular and cardiac health and disease.
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Affiliation(s)
- Christopher C Glembotski
- SDSU Heart Institute and the Department of Biology, San Diego State University, 5500 Campanile Dr, San Diego, CA 92182, USA.
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Sharma A, Masri J, Jo OD, Bernath A, Martin J, Funk A, Gera J. Protein kinase C regulates internal initiation of translation of the GATA-4 mRNA following vasopressin-induced hypertrophy of cardiac myocytes. J Biol Chem 2007; 282:9505-9516. [PMID: 17284439 DOI: 10.1074/jbc.m608874200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
GATA-4 is a key member of the GATA family of transcription factors involved in cardiac development and growth as well as in cardiac hypertrophy and heart failure. Our previous studies suggest that GATA-4 protein synthesis may be translationally regulated. We report here that the 518-nt long 5'-untranslated region (5'-UTR) of the GATA-4 mRNA, which is predicted to form stable secondary structures (-65 kcal/mol) such as to be inhibitory to cap-dependent initiation, confers efficient translation to monocistronic reporter mRNAs in cell-free extracts. Moreover, uncapped GATA-4 5'-UTR containing monocistronic reporter mRNAs continue to be well translated while capped reporters are insensitive to the inhibition of initiation by cap-analog, suggesting a cap-independent mechanism of initiation. Utilizing a dicistronic luciferase mRNA reporter containing the GATA-4 5'-UTR within the intercistronic region, we demonstrate that this leader sequence confers functional internal ribosome entry site (IRES) activity. The activity of the GATA-4 IRES is unaffected in trans-differentiating P19CL6 cells, however, is strongly stimulated immediately following arginine-vasopressin exposure of H9c2 ventricular myocytes. IRES activity is then maintained at submaximal levels during hypertrophic growth of these cells. Supraphysiological Ca(2+) levels diminished stimulation of IRES activity immediately following exposure to vasopressin and inhibition of protein kinase C activity utilizing a pseudosubstrate peptide sequence blocked IRES activity during hypertrophy. Thus, our data suggest a mechanism for GATA-4 protein synthesis under conditions of reduced global cap-dependent translation, which is maintained at a submaximal level during hypertrophic growth and point to the regulation of GATA-4 IRES activity by sarco(ER)-reticular Ca(2+) stores and PKC.
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Affiliation(s)
- Anushree Sharma
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Janine Masri
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Oak D Jo
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Andrew Bernath
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Jheralyn Martin
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Alexander Funk
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343
| | - Joseph Gera
- Department of Research & Development, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, California 91343; Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90048.
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14
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Thuerauf DJ, Marcinko M, Gude N, Rubio M, Sussman MA, Glembotski CC. Activation of the unfolded protein response in infarcted mouse heart and hypoxic cultured cardiac myocytes. Circ Res 2006; 99:275-82. [PMID: 16794188 DOI: 10.1161/01.res.0000233317.70421.03] [Citation(s) in RCA: 239] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Endoplasmic reticulum (ER) stresses that reduce ER protein folding activate the unfolded protein response (UPR). One effector of the UPR is the transcription factor X-box binding protein-1 (XBP1), which is expressed on ER stress-mediated splicing of the XBP1 mRNA. XBP1 induces certain ER-targeted proteins, eg, glucose-regulated protein 78 (GRP78), that help resolve the ER stress and foster cell survival. In this study, we determined whether hypoxia can activate the UPR in the cardiac context. Neonatal rat ventricular myocyte cultures subjected to hypoxia (16 hours) exhibited increased XBP1 mRNA splicing, XBP1 protein expression, GRP78 promoter activation, and GRP78 protein levels; however, the levels of these UPR markers declined during reoxygenation, suggesting that the UPR is activated during hypoxia but not during reoxygenation. When cells were infected with a recombinant adenovirus (AdV) encoding dominant-negative XBP1 (AdV-XBP1dn), UPR markers were reduced; however, hypoxia/reoxygenation-induced apoptosis increased. Confocal immunocytofluorescence demonstrated that hypoxia induced GRP78 in neonatal rat and isolated adult mouse ventricular myocytes. Moreover, mouse hearts subjected to in vivo myocardial infarction exhibited increased GRP78 expression in cardiac myocytes near the infarct, but not in healthy cells distal to the infarct. These results indicate that hypoxia activates the UPR in cardiac myocytes and that XBP1-inducible proteins may contribute to protecting the myocardium during hypoxic stress.
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Affiliation(s)
- Donna J Thuerauf
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, Calif. 92182, USA
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15
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Brostrom MA, Pan Z, Meiners S, Drumm C, Ahmed I, Brostrom CO. Ca2+ dynamics of thrombin-stimulated rat heart-derived embryonic myocytes: relationship to protein synthesis and cell growth. Int J Biochem Cell Biol 2003; 35:1573-87. [PMID: 12824066 DOI: 10.1016/s1357-2725(03)00132-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Various cell types respond to the serum protease, thrombin, with increased proliferation rates. In non-dividing postnatal mammalian cardiomyocytes, however, thrombin induces cellular hypertrophy. Both growth responses are associated with early Ca2+ signaling. The present study was conducted to characterize Ca2+ dynamics in thrombin stimulated, dividing embryonic cardiomyocytes, and to ascertain whether such dynamics support hypertrophic or hyperplastic growth. H9c2 rat cardiomyoblasts responded to thrombin with immediate, large increments in free Ca2+ that arose principally from the release of S(E)R sequestered Ca2+ and that persisted for only a few min. Ca2+ stores were refilled within 1h. Thrombin also increased rates of overall protein synthesis for several hours. This translational up-regulation, which required gene transcription, was abolished if cells were incubated at low extracellular Ca2+ during the first hour with thrombin. The protease conferred protective effects against toxicity resulting from serum deprivation and doxorubicin treatment. However, thrombin induced neither cellular hypertrophy, as is seen with arginine vasopressin, nor hyperplasia, as is observed with platelet-derived growth factor (PDGF-BB), in H9c2 cardiomyocytes. In comparison with vasopressin or PDGF-BB, thrombin promoted brief Ca2+ signaling, little cation movement to the extracellular fluid, and more rapid refilling of the S(E)R. It is concluded that the Ca2+ signaling generated by thrombin and the translational stimulation shown in this report to depend on this Ca2+ signaling are insufficient to sustain a major growth response in these embryonic cardiomyocytes.
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Affiliation(s)
- Margaret A Brostrom
- Department of Pharmacologya, U.M.D.N.J.-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
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Brostrom MA, Brostrom CO. Calcium dynamics and endoplasmic reticular function in the regulation of protein synthesis: implications for cell growth and adaptability. Cell Calcium 2003; 34:345-63. [PMID: 12909081 DOI: 10.1016/s0143-4160(03)00127-1] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The endoplasmic reticulum (ER) possesses the structural and functional features expected of an organelle that supports the integration and coordination of major cellular processes. Ca(2+) sequestered within the ER sustains lumenal protein processing while providing a reservoir of the cation to support stimulus-response coupling in the cytosol. Release of ER Ca(2+) sufficient to impair protein processing promotes ER stress and signals the "unfolded protein response" (UPR). The association of the UPR with an acute suppression of mRNA translational initiation and a longer term up-regulation of ER chaperones and partial translational recovery is discussed. Regulatory sites in mRNA translation and the mechanisms responsible for the early and later phases of the UPR are reviewed. The regulatory significance of GRP78/BiP, a multifunctional, broad-specificity ER chaperone, in the coordination of ER protein processing with mRNA translation during acute and chronic ER stress is addressed. The relationship of ER stress to protein misfolding in the cytoplasm is examined. Translational alterations in embryonic cardiomyocytes during treatments with various Ca(2+)-mobilizing, growth-promoting stimuli are described. The importance of ER Ca(2+) stores, ER chaperones, and cytosolic-free Ca(2+) in translational control and growth promotion by these stimuli is assessed. Some perspectives are provided regarding Ca(2+) as an integrating factor in the generation or diversion of metabolic energy. Circumstances impacting upon cellular adaptability during exposure to growth stimuli or during stressful conditions that require rapid adjustments in ATP for continued viability are considered.
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Affiliation(s)
- Margaret A Brostrom
- Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
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Brostrom MA, Meiners S, Brostrom CO. Functional receptor for platelet-derived growth factor in rat embryonic heart-derived myocytes: role of sequestered Ca2+ stores in receptor signaling and antagonism by arginine vasopressin. J Cell Biochem 2002; 84:736-49. [PMID: 11835399 DOI: 10.1002/jcb.10085] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Platelet-derived growth factor (PDGF) is established to function importantly in the growth, development, and function of most cardiovascular tissues. However, evidence that the factor participates directly in the growth and development of the mammalian myocardium is lacking. H9c2 rat embryonic ventricular myocytes were found to respond to PDGF-BB with a rapid mobilization of cell-associated Ca2+ and increased rates of protein synthesis, followed by markedly increased rates of DNA synthesis. PDGF acted as a full mitogen for these myocytes. Evidence is provided that documents the expression of classical PDGF-beta, but not PDGF-alpha, receptors in H9c2 cells. Scatchard analysis revealed the presence of 44,000 beta-receptors per myocyte. Cell shortening and clustering of plasmalemmal beta-receptors occurred within 30 min of exposure to PDGF-BB. Treatment was also associated with a transient increase in the rate of synthesis of GRP78/BiP, consistent with a transitory release of Ca2+ from the sarcoplasmic/endoplasmic reticulum [S(E)R]. Increased rates of protein synthesis at early times of PDGF treatment were additive with those occurring in response to arginine vasopressin, indicating different mechanisms of translational upregulation by these agents. The mitogenic effects of PDGF were delayed by vasopressin, which causes H9c2 myocytes to undergo hypertrophy while promoting the persistent depletion of S(E)R Ca2+ stores. In the presence of PDGF, vasopressin did not induce hypertrophy. As compared to untreated myocytes, DNA synthesis in PDGF-treated myocytes was optimized at lower extracellular Ca2+ concentrations and was significantly less sensitive to inhibition by ionomycin. H9c2 cells appear to provide a useful embryonic cardiomyocyte model in which to examine both PDGF-activated proliferative and vasopressin-activated hypertrophic events and the importance of transient vs. sustained Ca2+ release in these events.
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Affiliation(s)
- Margaret A Brostrom
- Department of Pharmacology, U.M.D.N.J.-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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