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Hale TM, Blackwood EA. Modeling heart failure with preserved ejection fraction in female mice: an elusive target. Am J Physiol Heart Circ Physiol 2024; 326:H1402-H1405. [PMID: 38668704 DOI: 10.1152/ajpheart.00139.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 05/18/2024]
Affiliation(s)
- Taben M Hale
- Department of Basic Medical Science, University of Arizona, College of Medicine-Phoenix, Phoenix, Arizona, United States
| | - Erik A Blackwood
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona, College of Medicine-Phoenix, Phoenix, Arizona, United States
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2
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Hofmann C, Aghajani M, Alcock CD, Blackwood EA, Sandmann C, Herzog N, Groß J, Plate L, Wiseman RL, Kaufman RJ, Katus HA, Jakobi T, Völkers M, Glembotski CC, Doroudgar S. ATF6 protects against protein misfolding during cardiac hypertrophy. J Mol Cell Cardiol 2024; 189:12-24. [PMID: 38401179 DOI: 10.1016/j.yjmcc.2024.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 01/11/2024] [Accepted: 02/01/2024] [Indexed: 02/26/2024]
Abstract
Cardiomyocytes activate the unfolded protein response (UPR) transcription factor ATF6 during pressure overload-induced hypertrophic growth. The UPR is thought to increase ER protein folding capacity and maintain proteostasis. ATF6 deficiency during pressure overload leads to heart failure, suggesting that ATF6 protects against myocardial dysfunction by preventing protein misfolding. However, conclusive evidence that ATF6 prevents toxic protein misfolding during cardiac hypertrophy is still pending. Here, we found that activation of the UPR, including ATF6, is a common response to pathological cardiac hypertrophy in mice. ATF6 KO mice failed to induce sufficient levels of UPR target genes in response to chronic isoproterenol infusion or transverse aortic constriction (TAC), resulting in impaired cardiac growth. To investigate the effects of ATF6 on protein folding, the accumulation of poly-ubiquitinated proteins as well as soluble amyloid oligomers were directly quantified in hypertrophied hearts of WT and ATF6 KO mice. Whereas only low levels of protein misfolding was observed in WT hearts after TAC, ATF6 KO mice accumulated increased quantities of misfolded protein, which was associated with impaired myocardial function. Collectively, the data suggest that ATF6 plays a critical adaptive role during cardiac hypertrophy by protecting against protein misfolding.
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Affiliation(s)
- Christoph Hofmann
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany; SDSU Heart Institute and Department of Biology, San Diego State University, San Diego, CA, USA
| | - Marjan Aghajani
- Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA
| | - Cecily D Alcock
- Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA
| | - Erik A Blackwood
- Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA
| | - Clara Sandmann
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Nicole Herzog
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Julia Groß
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Lars Plate
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - R Luke Wiseman
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Hugo A Katus
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Tobias Jakobi
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany; Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA
| | - Mirko Völkers
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Christopher C Glembotski
- Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA
| | - Shirin Doroudgar
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany; Department of Internal Medicine and the Translational Cardiovascular Research Center, University of Arizona College of Medicine - Phoenix, Phoenix, USA.
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3
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Glembotski CC, Bagchi S, Blackwood EA. ER-Specific Autophagy or ER-Phagy in Cardiac Myocytes Protects the Heart Against Doxorubicin-Induced Cardiotoxicity. JACC CardioOncol 2023; 5:671-673. [PMID: 37969647 PMCID: PMC10635872 DOI: 10.1016/j.jaccao.2023.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023] Open
Affiliation(s)
- Christopher C. Glembotski
- Translational Cardiovascular Research Center and the Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, USA
| | - Sukriti Bagchi
- Translational Cardiovascular Research Center and the Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, USA
| | - Erik A. Blackwood
- Translational Cardiovascular Research Center and the Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, Phoenix, Arizona, USA
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4
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Bilal AS, Parker SN, Murray VB, MacDonnell LF, Thuerauf DJ, Glembotski CC, Blackwood EA. Optimization of Large-Scale Adeno-Associated Virus (AAV) Production. Curr Protoc 2023; 3:e757. [PMID: 37166238 PMCID: PMC10188212 DOI: 10.1002/cpz1.757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Genetic manipulation in vivo is a critical method for mechanistically understanding gene function in disease and physiological processes. To facilitate this, embryonic transgenesis in popular animal models like mice has been developed. Compared to the longer, expensive methods of transgenesis, viral vectors, such as adeno-associated virus (AAV), have grown increasingly in popularity due to their relatively low cost and ease of production, translating to an overall greater versatility as a biological tool. In this article, we describe protocols for AAV production and purification for efficient transduction in vivo. Importantly, our method differs from others in application of a streamlined, more cost-effective approach. From this method, as many as 2 × 1013 genome-containing viral particles (vp), or 200 units, can be produced within 3 to 4 weeks, with a minimal cost of $1800 to $2000 for supplies and reagents and <15 hr of personnel time per week. A unit here is defined as 1 × 1011 vp, our standard dose of AAV per animal, injected via tail vein. Therefore, our method provides production and purification of AAV in quantities capable of transducing up to 200 animals. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: AAV production Basic Protocol 2: AAV purification.
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Affiliation(s)
- Alina S Bilal
- University of Arizona College of Medicine Phoenix, 475 N 5 St Phoenix, AZ 85004
| | - Sarah N Parker
- University of Arizona College of Medicine Phoenix, 475 N 5 St Phoenix, AZ 85004
| | - Victoria B Murray
- University of Arizona College of Medicine Phoenix, 475 N 5 St Phoenix, AZ 85004
| | - Lauren F MacDonnell
- University of Arizona College of Medicine Phoenix, 475 N 5 St Phoenix, AZ 85004
| | | | | | - Erik A Blackwood
- University of Arizona College of Medicine Phoenix, 475 N 5 St Phoenix, AZ 85004
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5
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Dave N, Judd JM, Decker A, Winslow W, Sarette P, Villarreal Espinosa O, Tallino S, Bartholomew SK, Bilal A, Sandler J, McDonough I, Winstone JK, Blackwood EA, Glembotski C, Karr T, Velazquez R. Dietary choline intake is necessary to prevent systems-wide organ pathology and reduce Alzheimer's disease hallmarks. Aging Cell 2023; 22:e13775. [PMID: 36642814 PMCID: PMC9924938 DOI: 10.1111/acel.13775] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 12/21/2022] [Accepted: 12/23/2022] [Indexed: 01/17/2023] Open
Abstract
There is an urgent need to identify modifiable environmental risk factors that reduce the incidence of Alzheimer's disease (AD). The B-like vitamin choline plays key roles in body- and brain-related functions. Choline produced endogenously by the phosphatidylethanolamine N-methyltransferase protein in the liver is not sufficient for adequate physiological functions, necessitating daily dietary intake. ~90% of Americans do not reach the recommended daily intake of dietary choline. Thus, it's imperative to determine whether dietary choline deficiency increases disease outcomes. Here, we placed 3xTg-AD, a model of AD, and non-transgenic (NonTg) control mice on either a standard laboratory diet with sufficient choline (ChN; 2.0 g/kg choline bitartrate) or a choline-deficient diet (Ch-; 0.0 g/kg choline bitartrate) from 3 to 12 (early to late adulthood) months of age. A Ch- diet reduced blood plasma choline levels, increased weight, and impaired both motor function and glucose metabolism in NonTg mice, with 3xTg-AD mice showing greater deficits. Tissue analyses showed cardiac and liver pathology, elevated soluble and insoluble Amyloid-β and Thioflavin S structures, and tau hyperphosphorylation at various pathological epitopes in the hippocampus and cortex of 3xTg-AD Ch- mice. To gain mechanistic insight, we performed unbiased proteomics of hippocampal and blood plasma samples. Dietary choline deficiency altered hippocampal networks associated with microtubule function and postsynaptic membrane regulation. In plasma, dietary choline deficiency altered protein networks associated with insulin metabolism, mitochondrial function, inflammation, and fructose metabolic processing. Our data highlight that dietary choline intake is necessary to prevent systems-wide organ pathology and reduce hallmark AD pathologies.
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Affiliation(s)
- Nikhil Dave
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Jessica M. Judd
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Arizona Alzheimer's ConsortiumPhoenixArizonaUSA
| | - Annika Decker
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Wendy Winslow
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Patrick Sarette
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Oscar Villarreal Espinosa
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Savannah Tallino
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Arizona Alzheimer's ConsortiumPhoenixArizonaUSA,School of Life SciencesArizona State UniversityTempeArizonaUSA
| | - Samantha K. Bartholomew
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Arizona Alzheimer's ConsortiumPhoenixArizonaUSA,School of Life SciencesArizona State UniversityTempeArizonaUSA
| | - Alina Bilal
- Translational Cardiovascular Research Center and Department of Internal MedicineUniversity of Arizona College of MedicinePhoenixArizonaUSA
| | - Jessica Sandler
- Biosciences Mass Spectrometry Facility, Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Ian McDonough
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Joanna K. Winstone
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Arizona Alzheimer's ConsortiumPhoenixArizonaUSA,School of Life SciencesArizona State UniversityTempeArizonaUSA
| | - Erik A. Blackwood
- Translational Cardiovascular Research Center and Department of Internal MedicineUniversity of Arizona College of MedicinePhoenixArizonaUSA
| | - Christopher Glembotski
- Translational Cardiovascular Research Center and Department of Internal MedicineUniversity of Arizona College of MedicinePhoenixArizonaUSA
| | - Timothy Karr
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Biosciences Mass Spectrometry Facility, Biodesign InstituteArizona State UniversityTempeArizonaUSA
| | - Ramon Velazquez
- Arizona State University‐Banner Neurodegenerative Disease Research Center at the Biodesign InstituteArizona State UniversityTempeArizonaUSA,Arizona Alzheimer's ConsortiumPhoenixArizonaUSA,School of Life SciencesArizona State UniversityTempeArizonaUSA
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6
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Blackwood EA, MacDonnell LF, Thuerauf DJ, Bilal AS, Murray VB, Bedi KC, Margulies KB, Glembotski CC. Noncanonical Form of ERAD Regulates Cardiac Hypertrophy. Circulation 2023; 147:66-82. [PMID: 36317534 PMCID: PMC9797446 DOI: 10.1161/circulationaha.122.061557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 09/30/2022] [Indexed: 11/05/2022]
Abstract
BACKGROUND Cardiac hypertrophy increases demands on protein folding, which causes an accumulation of misfolded proteins in the endoplasmic reticulum (ER). These misfolded proteins can be removed by the adaptive retrotranslocation, polyubiquitylation, and a proteasome-mediated degradation process, ER-associated degradation (ERAD), which, as a biological process and rate, has not been studied in vivo. To investigate a role for ERAD in a pathophysiological model, we examined the function of the functional initiator of ERAD, valosin-containing protein-interacting membrane protein (VIMP), positing that VIMP would be adaptive in pathological cardiac hypertrophy in mice. METHODS We developed a new method involving cardiac myocyte-specific adeno-associated virus serovar 9-mediated expression of the canonical ERAD substrate, TCRα, to measure the rate of ERAD, ie, ERAD flux, in the heart in vivo. Adeno-associated virus serovar 9 was also used to either knock down or overexpress VIMP in the heart. Then mice were subjected to transverse aortic constriction to induce pressure overload-induced cardiac hypertrophy. RESULTS ERAD flux was slowed in both human heart failure and mice after transverse aortic constriction. Surprisingly, although VIMP adaptively contributes to ERAD in model cell lines, in the heart, VIMP knockdown increased ERAD and ameliorated transverse aortic constriction-induced cardiac hypertrophy. Coordinately, VIMP overexpression exacerbated cardiac hypertrophy, which was dependent on VIMP engaging in ERAD. Mechanistically, we found that the cytosolic protein kinase SGK1 (serum/glucocorticoid regulated kinase 1) is a major driver of pathological cardiac hypertrophy in mice subjected to transverse aortic constriction, and that VIMP knockdown decreased the levels of SGK1, which subsequently decreased cardiac pathology. We went on to show that although it is not an ER protein, and resides outside of the ER, SGK1 is degraded by ERAD in a noncanonical process we call ERAD-Out. Despite never having been in the ER, SGK1 is recognized as an ERAD substrate by the ERAD component DERLIN1, and uniquely in cardiac myocytes, VIMP displaces DERLIN1 from initiating ERAD, which decreased SGK1 degradation and promoted cardiac hypertrophy. CONCLUSIONS ERAD-Out is a new preferentially favored noncanonical form of ERAD that mediates the degradation of SGK1 in cardiac myocytes, and in so doing is therefore an important determinant of how the heart responds to pathological stimuli, such as pressure overload.
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Affiliation(s)
- Erik A. Blackwood
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, AZ
| | - Lauren F. MacDonnell
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, AZ
| | - Donna J. Thuerauf
- San Diego State University Heart Institute and Department of Biology, San Diego State University, CA
| | - Alina S. Bilal
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, AZ
| | - Victoria B. Murray
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, AZ
| | - Kenneth C. Bedi
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Kenneth B. Margulies
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Christopher C. Glembotski
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, AZ
- Department of Internal Medicine, University of Arizona College of Medicine-Phoenix, Phoenix AZ
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7
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Blackwood EA, Glembotski CC. Hydrogen sulfide: the gas that fuels longevity. J Cardiovasc Aging 2022; 2:26. [PMID: 36776272 PMCID: PMC9912355 DOI: 10.20517/jca.2022.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The molecular determinants of lifespan can be examined in animal models with the long-term objective of applying what is learned to the development of strategies to enhance longevity in humans. Here, we comment on a recent publication examining the molecular mechanisms that determine lifespan in worms, Caenorhabditis elegans (C. elegans), where it was shown that inhibiting protein synthesis increased levels of the transcription factor, ATF4. Gene expression analyses showed that ATF4 increased the expression of genes responsible for the formation of the gas, hydrogen sulfide (H2S). Further examination showed that H2S increased longevity in C. elegans by modifying proteins in ways that stabilize their structures and enhance their functions. H2S has been shown to improve cardiovascular performance in mouse models of heart disease, and clinical trials are underway to test the effects of H2S on cardiovascular health in humans. These findings support the concept that nutrient deprivation, which slows protein synthesis and leads to ATF4-mediated H2S production, may extend lifespan by improving the function of the cardiovascular system and other systems that influence longevity in humans.
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Affiliation(s)
- Erik A Blackwood
- Department of Internal Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ 85004, USA
| | - Christopher C Glembotski
- Department of Internal Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ 85004, USA
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8
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Bilal AS, Thuerauf DJ, Blackwood EA, Glembotski CC. Design and Production of Heart Chamber-Specific AAV9 Vectors. Methods Mol Biol 2022; 2573:89-113. [PMID: 36040589 DOI: 10.1007/978-1-0716-2707-5_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Adeno-associated virus serotype 9 (AAV9) is often used in heart research involving gene delivery due to its cardiotropism, high transduction efficiency, and little to no pathogenicity, making it highly applicable for gene manipulation, in vivo. However, current AAV9 technology is limited by the lack of strains that can selectively express and elucidate gene function in an atrial- and ventricular-specific manner. In fact, study of gene function in cardiac atria has been limited due to the lack of an appropriate tool to study atrial gene expression in vivo, hindering progress in the study of atrial-specific diseases such as atrial fibrillation, the most common cardiac arrhythmia in the USA.This chapter describes the method for the design and production of such chamber-specific AAV9 vectors, with the use of Nppa and Myl2 promoters to enhance atrial- and ventricular-specific expression. While several gene promoter candidates were considered and tested, Nppa and Myl2 were selected for use here because of their clearly defined regulatory elements that confer cardiac chamber-specific expression. Accordingly, Nppa (-425/+25) and Myl2 (-226/+36) promoter fragments are inserted into AAV9 vectors. The atrial- and ventricular-specific expression conferred by these new recombinant AAV9 was confirmed in a double-fluorescent Cre-dependent reporter mouse model. At only 450 and 262 base pairs of Nppa and Myl2 promoters, respectively, these AAV9 that drive chamber-specific AAV9 transgene expression address two major limitations of AAV9 technology, i.e., achieving chamber-specificity while maximizing space in the AAV genome for insertion of larger transgenes.
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Affiliation(s)
- Alina S Bilal
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA
| | - Donna J Thuerauf
- Department of Cellular and Molecular Biology, San Diego State University, San Diego, CA, USA
| | - Erik A Blackwood
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA
| | - Christopher C Glembotski
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA.
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9
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Affiliation(s)
- Alina S Bilal
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix (A.S.B., E.A.B., C.C.G.)
| | - Erik A Blackwood
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix (A.S.B., E.A.B., C.C.G.)
| | - Donna J Thuerauf
- Department of Cellular and Molecular Biology, San Diego State University, CA (D.J.T.)
| | - Christopher C Glembotski
- Translational Cardiovascular Research Center and Department of Internal Medicine, University of Arizona College of Medicine-Phoenix (A.S.B., E.A.B., C.C.G.)
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10
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Marsh KG, Arrieta A, Thuerauf DJ, Blackwood EA, MacDonnell L, Glembotski CC. The peroxisomal enzyme, FAR1, is induced during ER stress in an ATF6-dependent manner in cardiac myocytes. Am J Physiol Heart Circ Physiol 2021; 320:H1813-H1821. [PMID: 33666503 DOI: 10.1152/ajpheart.00999.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Although peroxisomes have been extensively studied in other cell types, their presence and function have gone virtually unexamined in cardiac myocytes. Here, in neonatal rat ventricular myocytes (NRVM) we showed that several known peroxisomal proteins co-localize to punctate structures with a morphology typical of peroxisomes. Surprisingly, we found that the peroxisomal protein, fatty acyl-CoA reductase 1 (FAR1), was upregulated by pharmacological and pathophysiological ER stress induced by tunicamycin (TM) and simulated ischemia-reperfusion (sI/R), respectively. Moreover, FAR1 induction in NRVM was mediated by the ER stress sensor, activating transcription factor 6 (ATF6). Functionally, FAR1 knockdown reduced myocyte death during oxidative stress induced by either sI/R or hydrogen peroxide (H2O2). Thus, Far1 is an ER stress-inducible gene, which encodes a protein that localizes to peroxisomes of cardiac myocytes, where it reduces myocyte viability during oxidative stress. Since FAR1 is critical for plasmalogen synthesis, these results imply that plasmalogens may exert maladaptive effects on the viability of myocytes exposed to oxidative stress.NEW & NOTEWORTHY The peroxisomal enzyme, FAR1, was shown to be an ER stress- and ATF6-inducible protein that localizes to peroxisomes in cardiac myocytes. FAR1 decreases myocyte viability during oxidative stress.
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Affiliation(s)
- Kayleigh G Marsh
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California
| | - Adrian Arrieta
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California.,Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Donna J Thuerauf
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California
| | - Erik A Blackwood
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California.,Department of Internal Medicine and the Center for Translational Cardiovascular Research, University of Arizona, Phoenix, Arizona
| | - Lauren MacDonnell
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California.,Department of Internal Medicine and the Center for Translational Cardiovascular Research, University of Arizona, Phoenix, Arizona
| | - Christopher C Glembotski
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California.,Department of Internal Medicine and the Center for Translational Cardiovascular Research, University of Arizona, Phoenix, Arizona
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11
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Blackwood EA, Bilal AS, Azizi K, Sarakki A, Glembotski CC. Simultaneous Isolation and Culture of Atrial Myocytes, Ventricular Myocytes, and Non-Myocytes from an Adult Mouse Heart. J Vis Exp 2020:10.3791/61224. [PMID: 32597844 PMCID: PMC8580476 DOI: 10.3791/61224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The isolation and culturing of cardiac myocytes from mice has been essential for furthering the understanding of cardiac physiology and pathophysiology. While isolating myocytes from neonatal mouse hearts is relatively straightforward, myocytes from the adult murine heart are preferred. This is because compared to neonatal cells, adult myocytes more accurately recapitulate cell function as it occurs in the adult heart in vivo. However, it is technically difficult to isolate adult mouse cardiac myocytes in the necessary quantities and viability, which contributes to an experimental impasse. Furthermore, published procedures are specific for the isolation of either atrial or ventricular myocytes at the expense of atrial and ventricular non-myocyte cells. Described here is a detailed method for isolating both atrial and ventricular cardiac myocytes, along with atrial and ventricular non-myocytes, simultaneously from a single mouse heart. Also provided are the details for optimal cell-specific culturing methods, which enhance cell viability and function. This protocol aims not only to expedite the process of adult murine cardiac cell isolation, but also to increase the yield and viability of cells for investigations of atrial and ventricular cardiac cells.
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Affiliation(s)
- Erik A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University
| | - Alina S Bilal
- San Diego State University Heart Institute and the Department of Biology, San Diego State University
| | - Khalid Azizi
- San Diego State University Heart Institute and the Department of Biology, San Diego State University
| | - Anup Sarakki
- San Diego State University Heart Institute and the Department of Biology, San Diego State University
| | - Christopher C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University;
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12
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Blackwood EA, Thuerauf DJ, Stastna M, Stephens H, Sand Z, Pentoney A, Azizi K, Jakobi T, Van Eyk JE, Katus HA, Glembotski CC, Doroudgar S. Proteomic analysis of the cardiac myocyte secretome reveals extracellular protective functions for the ER stress response. J Mol Cell Cardiol 2020; 143:132-144. [PMID: 32339566 PMCID: PMC8597053 DOI: 10.1016/j.yjmcc.2020.04.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 04/07/2020] [Accepted: 04/09/2020] [Indexed: 12/25/2022]
Abstract
The effects of ER stress on protein secretion by cardiac myocytes are not well understood. In this study, the ER stressor thapsigargin (TG), which depletes ER calcium, induced death of cultured neonatal rat ventricular myocytes (NRVMs) in high media volume but fostered protection in low media volume. In contrast, another ER stressor, tunicamycin (TM), a protein glycosylation inhibitor, induced NRVM death in all media volumes, suggesting that protective proteins were secreted in response to TG but not TM. Proteomic analyses of TG- and TM-conditioned media showed that the secretion of most proteins was inhibited by TG and TM; however, secretion of several ER-resident proteins, including GRP78 was increased by TG but not TM. Simulated ischemia, which decreases ER/SR calcium also increased secretion of these proteins. Mechanistically, secreted GRP78 was shown to enhance survival of NRVMs by collaborating with a cell-surface protein, CRIPTO, to activate protective AKT signaling and to inhibit death-promoting SMAD2 signaling. Thus, proteins secreted during ER stress mediated by ER calcium depletion can enhance cardiac myocyte viability.
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Affiliation(s)
- Erik A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Donna J Thuerauf
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Miroslava Stastna
- Advanced Clinical Biosystems Research Institute, Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA; Institute of Analytical Chemistry of the Czech Academy of Sciences, Brno, Czech Republic
| | - Haley Stephens
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Zoe Sand
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Amber Pentoney
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Khalid Azizi
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Tobias Jakobi
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Germany; Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology, Heidelberg University Hospital, Heidelberg, Germany
| | - Jennifer E Van Eyk
- Advanced Clinical Biosystems Research Institute, Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Hugo A Katus
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Germany
| | - Christopher C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, USA
| | - Shirin Doroudgar
- Department of Internal Medicine III (Cardiology, Angiology, and Pneumology), Heidelberg University Hospital, Heidelberg, Germany; DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Germany.
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13
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Arrieta A, Blackwood EA, Stauffer WT, Santo Domingo M, Bilal AS, Thuerauf DJ, Pentoney AN, Aivati C, Sarakki AV, Doroudgar S, Glembotski CC. Mesencephalic astrocyte-derived neurotrophic factor is an ER-resident chaperone that protects against reductive stress in the heart. J Biol Chem 2020; 295:7566-7583. [PMID: 32327487 DOI: 10.1074/jbc.ra120.013345] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/17/2020] [Indexed: 12/13/2022] Open
Abstract
We have previously demonstrated that ischemia/reperfusion (I/R) impairs endoplasmic reticulum (ER)-based protein folding in the heart and thereby activates an unfolded protein response sensor and effector, activated transcription factor 6α (ATF6). ATF6 then induces mesencephalic astrocyte-derived neurotrophic factor (MANF), an ER-resident protein with no known structural homologs and unclear ER function. To determine MANF's function in the heart in vivo, here we developed a cardiomyocyte-specific MANF-knockdown mouse model. MANF knockdown increased cardiac damage after I/R, which was reversed by AAV9-mediated ectopic MANF expression. Mechanistically, MANF knockdown in cultured neonatal rat ventricular myocytes (NRVMs) impaired protein folding in the ER and cardiomyocyte viability during simulated I/R. However, this was not due to MANF-mediated protection from reactive oxygen species generated during reperfusion. Because I/R impairs oxygen-dependent ER protein disulfide formation and such impairment can be caused by reductive stress in the ER, we examined the effects of the reductive ER stressor DTT. MANF knockdown in NRVMs increased cell death from DTT-mediated reductive ER stress, but not from nonreductive ER stresses caused by thapsigargin-mediated ER Ca2+ depletion or tunicamycin-mediated inhibition of ER protein glycosylation. In vitro, recombinant MANF exhibited chaperone activity that depended on its conserved cysteine residues. Moreover, in cells, MANF bound to a model ER protein exhibiting improper disulfide bond formation during reductive ER stress but did not bind to this protein during nonreductive ER stress. We conclude that MANF is an ER chaperone that enhances protein folding and myocyte viability during reductive ER stress.
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Affiliation(s)
- Adrian Arrieta
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Erik A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Winston T Stauffer
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Michelle Santo Domingo
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Alina S Bilal
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Donna J Thuerauf
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Amber N Pentoney
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Cathrine Aivati
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Anup V Sarakki
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
| | - Shirin Doroudgar
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA.,Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Innere Medizin III, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
| | - Christopher C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California, USA
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14
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Abstract
Proteostasis encompasses a homeostatic cellular network in all cells that maintains the integrity of the proteome, which is critical for optimal cellular function. The components of the proteostasis network include protein synthesis, folding, trafficking, and degradation. Cardiac myocytes have a specialized endoplasmic reticulum (ER) called the sarcoplasmic reticulum that is well known for its role in contractile calcium handling. However, less studied is the proteostasis network associated with the ER, which is of particular importance in cardiac myocytes because it ensures the integrity of proteins that are critical for cardiac contraction, e.g., ion channels, as well as proteins necessary for maintaining myocyte viability and interaction with other cell types, e.g., secreted hormones and growth factors. A major aspect of the ER proteostasis network is the ER unfolded protein response (UPR), which is initiated when misfolded proteins in the ER activate a group of three ER transmembrane proteins, one of which is the transcription factor, ATF6. Prior to studies in the heart, ATF6 had been shown in model cell lines to be primarily adaptive, exerting protective effects by inducing genes that encode ER proteins that fortify protein-folding in this organelle, thus establishing the canonical role for ATF6. Subsequent studies in isolated cardiac myocytes and in the myocardium, in vivo, have expanded roles for ATF6 beyond the canonical functions to include the induction of genes that encode proteins outside of the ER that do not have known functions that are obviously related to ER protein-folding. The identification of such non-canonical roles for ATF6, as well as findings that the gene programs induced by ATF6 differ depending on the stimulus, have piqued interest in further research on ATF6 as an adaptive effector in cardiac myocytes, underscoring the therapeutic potential of activating ATF6 in the heart. Moreover, discoveries of small molecule activators of ATF6 that adaptively affect the heart, as well as other organs, in vivo, have expanded the potential for development of ATF6-based therapeutics. This review focuses on the ATF6 arm of the ER UPR and its effects on the proteostasis network in the myocardium.
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Affiliation(s)
- Christopher C Glembotski
- Department of Biology, College of Sciences, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Adrian Arrieta
- Department of Biology, College of Sciences, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Erik A Blackwood
- Department of Biology, College of Sciences, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Winston T Stauffer
- Department of Biology, College of Sciences, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
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Cheung TKD, Bilal AS, Blackwood EA, Thuerauf DJ, Glembotski CC. ATF6β is an Adaptive Transcription Factor in Cardiac Myocyte. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.09606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Bilal AS, Blackwood EA, Thuerauf DJ, Glembotski CC. Small Nppa and Myl2 Promoters Are Sufficient to Maintain Chamber‐specific Expression on an AAV9 Platform. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.07372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Palmer JE, Brietske BM, Bate TC, Blackwood EA, Garg M, Glembotski CC, Cooley CB. Reactive Oxygen Species (ROS)-Activatable Prodrug for Selective Activation of ATF6 after Ischemia/Reperfusion Injury. ACS Med Chem Lett 2020; 11:292-297. [PMID: 32184959 DOI: 10.1021/acsmedchemlett.9b00299] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 11/06/2019] [Indexed: 12/31/2022] Open
Abstract
We describe here the design, synthesis, and biological evaluation of a reactive oxygen species (ROS)-activatable prodrug for the selective delivery of 147, a small molecule ATF6 activator, for ischemia/reperfusion injury. ROS-activatable prodrug 1 and a negative control unable to release free drug were synthesized and examined for peroxide-mediated activation. Prodrug 1 blocks activity of 147 by its inability to undergo metabolic oxidation by ER-resident cytochrome P450 enzymes such as Cyp1A2, probed directly here for the first time. Biological evaluation of ROS-activatable prodrug 1 in primary cardiomyocytes demonstrates protection against peroxide-mediated toxicity and enhances viability following simulated I/R injury. The ability to selectively target ATF6 activation under diseased conditions establishes the potential for localized stress-responsive signaling pathway activation as a therapeutic approach for I/R injury and related protein misfolding maladies.
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Affiliation(s)
- Jonathan E. Palmer
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212, United States
| | - Breanna M. Brietske
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212, United States
| | - Tyler C. Bate
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212, United States
| | - Erik A. Blackwood
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California 92182, United States
| | - Manasa Garg
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212, United States
| | - Christopher C. Glembotski
- San Diego State University Heart Institute and Department of Biology, San Diego State University, San Diego, California 92182, United States
| | - Christina B. Cooley
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212, United States
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18
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Stauffer WT, Blackwood EA, Azizi K, Kaufman RJ, Glembotski CC. The ER Unfolded Protein Response Effector, ATF6, Reduces Cardiac Fibrosis and Decreases Activation of Cardiac Fibroblasts. Int J Mol Sci 2020; 21:ijms21041373. [PMID: 32085622 PMCID: PMC7073073 DOI: 10.3390/ijms21041373] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/06/2020] [Accepted: 02/14/2020] [Indexed: 02/06/2023] Open
Abstract
Activating transcription factor-6 α (ATF6) is one of the three main sensors and effectors of the endoplasmic reticulum (ER) stress response and, as such, it is critical for protecting the heart and other tissues from a variety of environmental insults and disease states. In the heart, ATF6 has been shown to protect cardiac myocytes. However, its roles in other cell types in the heart are unknown. Here we show that ATF6 decreases the activation of cardiac fibroblasts in response to the cytokine, transforming growth factor β (TGFβ), which can induce fibroblast trans-differentiation into a myofibroblast phenotype through signaling via the TGFβ–Smad pathway. ATF6 activation suppressed fibroblast contraction and the induction of α smooth muscle actin (αSMA). Conversely, fibroblasts were hyperactivated when ATF6 was silenced or deleted. ATF6 thus represents a novel inhibitor of the TGFβ–Smad axis of cardiac fibroblast activation.
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Affiliation(s)
- Winston T. Stauffer
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.T.S.); (E.A.B.); (K.A.)
| | - Erik A. Blackwood
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.T.S.); (E.A.B.); (K.A.)
| | - Khalid Azizi
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.T.S.); (E.A.B.); (K.A.)
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA;
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92161, USA
| | - Christopher C. Glembotski
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA 92182, USA; (W.T.S.); (E.A.B.); (K.A.)
- Correspondence: ; Tel.: +1-619-594-2958
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19
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Glembotski CC, Arrieta A, Blackwood EA. Unfolding the Roles of Mitochondria as Therapeutic Targets for Heart Disease. J Am Coll Cardiol 2020; 73:1807-1810. [PMID: 30975298 DOI: 10.1016/j.jacc.2018.12.089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 12/02/2018] [Indexed: 11/19/2022]
Affiliation(s)
- Christopher C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California.
| | - Adrian Arrieta
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California
| | - Erik A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, California
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20
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Arrieta A, Blackwood EA, Stauffer WT, Glembotski CC. Integrating ER and Mitochondrial Proteostasis in the Healthy and Diseased Heart. Front Cardiovasc Med 2020; 6:193. [PMID: 32010709 PMCID: PMC6974444 DOI: 10.3389/fcvm.2019.00193] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 12/18/2019] [Indexed: 12/12/2022] Open
Abstract
The integrity of the proteome in cardiac myocytes is critical for robust heart function. Proteome integrity in all cells is managed by protein homeostasis or proteostasis, which encompasses processes that maintain the balance of protein synthesis, folding, and degradation in ways that allow cells to adapt to conditions that present a potential challenge to viability (1). While there are processes in various cellular locations in cardiac myocytes that contribute to proteostasis, those in the cytosol, mitochondria and endoplasmic reticulum (ER) have dominant roles in maintaining cardiac contractile function. Cytosolic proteostasis has been reviewed elsewhere (2, 3); accordingly, this review focuses on proteostasis in the ER and mitochondria, and how they might influence each other and, thus, impact heart function in the settings of cardiac physiology and disease.
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Affiliation(s)
- Adrian Arrieta
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Erik A Blackwood
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Winston T Stauffer
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
| | - Christopher C Glembotski
- Department of Biology, San Diego State University Heart Institute, San Diego State University, San Diego, CA, United States
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21
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Blackwood EA, Hofmann C, Santo Domingo M, Bilal AS, Sarakki A, Stauffer W, Arrieta A, Thuerauf DJ, Kolkhorst FW, Müller OJ, Jakobi T, Dieterich C, Katus HA, Doroudgar S, Glembotski CC. ATF6 Regulates Cardiac Hypertrophy by Transcriptional Induction of the mTORC1 Activator, Rheb. Circ Res 2019; 124:79-93. [PMID: 30582446 DOI: 10.1161/circresaha.118.313854] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Endoplasmic reticulum (ER) stress dysregulates ER proteostasis, which activates the transcription factor, ATF6 (activating transcription factor 6α), an inducer of genes that enhance protein folding and restore ER proteostasis. Because of increased protein synthesis, it is possible that protein folding and ER proteostasis are challenged during cardiac myocyte growth. However, it is not known whether ATF6 is activated, and if so, what its function is during hypertrophic growth of cardiac myocytes. OBJECTIVE To examine the activity and function of ATF6 during cardiac hypertrophy. METHODS AND RESULTS We found that ER stress and ATF6 were activated and ATF6 target genes were induced in mice subjected to an acute model of transverse aortic constriction, or to free-wheel exercise, both of which promote adaptive cardiac myocyte hypertrophy with preserved cardiac function. Cardiac myocyte-specific deletion of Atf6 (ATF6 cKO [conditional knockout]) blunted transverse aortic constriction and exercise-induced cardiac myocyte hypertrophy and impaired cardiac function, demonstrating a role for ATF6 in compensatory myocyte growth. Transcript profiling and chromatin immunoprecipitation identified RHEB (Ras homologue enriched in brain) as an ATF6 target gene in the heart. RHEB is an activator of mTORC1 (mammalian/mechanistic target of rapamycin complex 1), a major inducer of protein synthesis and subsequent cell growth. Both transverse aortic constriction and exercise upregulated RHEB, activated mTORC1, and induced cardiac hypertrophy in wild type mouse hearts but not in ATF6 cKO hearts. Mechanistically, knockdown of ATF6 in neonatal rat ventricular myocytes blocked phenylephrine- and IGF1 (insulin-like growth factor 1)-mediated RHEB induction, mTORC1 activation, and myocyte growth, all of which were restored by ectopic RHEB expression. Moreover, adeno-associated virus 9- RHEB restored cardiac growth to ATF6 cKO mice subjected to transverse aortic constriction. Finally, ATF6 induced RHEB in response to growth factors, but not in response to other activators of ATF6 that do not induce growth, indicating that ATF6 target gene induction is stress specific. CONCLUSIONS Compensatory cardiac hypertrophy activates ER stress and ATF6, which induces RHEB and activates mTORC1. Thus, ATF6 is a previously unrecognized link between growth stimuli and mTORC1-mediated cardiac growth.
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Affiliation(s)
- Erik A Blackwood
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Christoph Hofmann
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.).,Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.)
| | - Michelle Santo Domingo
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Alina S Bilal
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Anup Sarakki
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Winston Stauffer
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Adrian Arrieta
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Donna J Thuerauf
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Fred W Kolkhorst
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
| | - Oliver J Müller
- Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.).,Department of Internal Medicine III, University of Kiel, Germany, and German Centre for Cardiovascular Research, Partner Site Hamburg/Kiel/Lübeck, Germany (O.J.M.)
| | - Tobias Jakobi
- Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.).,Section of Bioinformatics and Systems Cardiology, Department of Internal Medicine III, University Hospital Heidelberg, Germany (T.J., C.D.)
| | - Christoph Dieterich
- Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.).,Section of Bioinformatics and Systems Cardiology, Department of Internal Medicine III, University Hospital Heidelberg, Germany (T.J., C.D.)
| | - Hugo A Katus
- Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.)
| | - Shirin Doroudgar
- Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., O.J.M., H.A.K., S.D.).,German Centre for Cardiovascular Research, Partner Site Heidelberg (C.H., O.J.M., T.J., C.D., H.A.K., S.D.)
| | - Christopher C Glembotski
- From the Department of Biology, San Diego State University Heart Institute, San Diego State University, CA (E.A.B., C.H., M.S.D., A.S.B., A.S., W.S., A.A., D.J.T., F.W.K., C.C.G.)
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22
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Stauffer WT, Blackwood EA, Azizi K, Stephens HN, Doroudgar S, Glembotski CC. Abstract 260: The ER Unfolded Protein Response Effector, ATF6, Reduces Fibrosis and Moderates Activation of Cardiac Fibroblasts. Circ Res 2019. [DOI: 10.1161/res.125.suppl_1.260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fibroblasts in the heart respond to myocardial injury by infiltrating the affected area and differentiating into new cell types called myofibroblasts. These cells are characterized both by the induction of contractile proteins and the secretion of extracellular matrix proteins which form fibrotic scar tissue. Investigating the factors governing fibroblast activation is key to understanding how these cells function in the heart and may be key to future therapeutic strategies. Activating transcription factor 6 (ATF6), an effector of the endoplasmic reticulum unfolded protein response, plays critical roles in development, as well as in the differentiation of certain cell types, though it has not been studied in this regard in the heart. Our lab has demonstrated that ATF6 in cardiac myocytes is cardioprotective
in vivo
during heart disease. However, ATF6 has not been studied in cardiac fibroblasts and its effect on fibrosis in the heart is unknown. We hypothesized that ATF6 in fibroblasts is an important regulator of their function. Fibroblast activation markers including αSMA were increased in infarcted hearts with global ATF6 deletion. Additionally, hearts with pressure overload showed increased fibrosis staining in global ATF6-null mice relative to WT hearts. In isolated adult murine ventricular fibroblasts (AMVF), loss of ATF6 induced myofibroblast markers with and without the activation stimulus TGFβ. ATF6 loss of function also enhanced the effect of TGFβ on fibroblast contraction. These effects were associated with an increase in Smad phosphorylation, a crucial step in the TGFβ pathway. Interestingly, the effect of ATF6 loss of function in AMVF was erased when treated with a TGFβ receptor inhibitor. Additionally, when ATF6 was overexpressed or when endogenous ATF6 was chemically activated, myofibroblast markers were reduced and activation by TGFβ was blunted. ATF6 activation was associated with induction of several TGFβ/Smad pathway negative regulators including SMURF1, SMURF2, and PMEPA1, though none of these are known to be ATF6 target genes. These data suggest that ATF6 plays an important role in moderating fibroblast activation and this may contribute to previously reported roles for ATF6 in preserving cardiac function post-injury.
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23
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Blackwood EA, Azizi K, Thuerauf DJ, Paxman RJ, Plate L, Kelly JW, Wiseman RL, Glembotski CC. Pharmacologic ATF6 activation confers global protection in widespread disease models by reprograming cellular proteostasis. Nat Commun 2019; 10:187. [PMID: 30643122 PMCID: PMC6331617 DOI: 10.1038/s41467-018-08129-2] [Citation(s) in RCA: 118] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 12/11/2018] [Indexed: 01/05/2023] Open
Abstract
Pharmacologic activation of stress-responsive signaling pathways provides a promising approach for ameliorating imbalances in proteostasis associated with diverse diseases. However, this approach has not been employed in vivo. Here we show, using a mouse model of myocardial ischemia/reperfusion, that selective pharmacologic activation of the ATF6 arm of the unfolded protein response (UPR) during reperfusion, a typical clinical intervention point after myocardial infarction, transcriptionally reprograms proteostasis, ameliorates damage and preserves heart function. These effects were lost upon cardiac myocyte-specific Atf6 deletion in the heart, demonstrating the critical role played by ATF6 in mediating pharmacologically activated proteostasis-based protection of the heart. Pharmacological activation of ATF6 is also protective in renal and cerebral ischemia/reperfusion models, demonstrating its widespread utility. Thus, pharmacologic activation of ATF6 represents a proteostasis-based therapeutic strategy for ameliorating ischemia/reperfusion damage, underscoring its unique translational potential for treating a wide range of pathologies caused by imbalanced proteostasis.
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Affiliation(s)
- Erik A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA
| | - Khalid Azizi
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA
| | - Donna J Thuerauf
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA
| | - Ryan J Paxman
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Lars Plate
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, 92037, USA
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Jeffery W Kelly
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, 92037, USA
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - R Luke Wiseman
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Christopher C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA.
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24
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Paxman R, Plate L, Blackwood EA, Glembotski C, Powers ET, Wiseman RL, Kelly JW. Pharmacologic ATF6 activating compounds are metabolically activated to selectively modify endoplasmic reticulum proteins. eLife 2018; 7:37168. [PMID: 30084354 PMCID: PMC6080950 DOI: 10.7554/elife.37168] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/24/2018] [Indexed: 12/15/2022] Open
Abstract
Pharmacologic arm-selective unfolded protein response (UPR) signaling pathway activation is emerging as a promising strategy to ameliorate imbalances in endoplasmic reticulum (ER) proteostasis implicated in diverse diseases. The small molecule N-(2-hydroxy-5-methylphenyl)-3-phenylpropanamide (147) was previously identified (Plate et al., 2016) to preferentially activate the ATF6 arm of the UPR, promoting protective remodeling of the ER proteostasis network. Here we show that 147-dependent ATF6 activation requires metabolic oxidation to form an electrophile that preferentially reacts with ER proteins. Proteins covalently modified by 147 include protein disulfide isomerases (PDIs), known to regulate ATF6 activation. Genetic depletion of PDIs perturbs 147-dependent induction of the ATF6-target gene, BiP, implicating covalent modifications of PDIs in the preferential activation of ATF6 afforded by treatment with 147. Thus, 147 is a pro-drug that preferentially activates ATF6 signaling through a mechanism involving localized metabolic activation and selective covalent modification of ER resident proteins that regulate ATF6 activity.
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Affiliation(s)
- Ryan Paxman
- Department of Chemistry, The Scripps Research Institute, La Jolla, United States
| | - Lars Plate
- Department of Chemistry, The Scripps Research Institute, La Jolla, United States.,Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Erik A Blackwood
- Department of Biology, San Diego State University, San Diego, United States.,San Diego State University Heart Institute, San Diego State University, San Diego, United States
| | - Chris Glembotski
- Department of Biology, San Diego State University, San Diego, United States.,San Diego State University Heart Institute, San Diego State University, San Diego, United States
| | - Evan T Powers
- Department of Chemistry, The Scripps Research Institute, La Jolla, United States
| | - R Luke Wiseman
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States
| | - Jeffery W Kelly
- Department of Chemistry, The Scripps Research Institute, La Jolla, United States.,Department of Molecular Medicine, The Scripps Research Institute, La Jolla, United States.,The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, United States
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25
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Stauffer WT, Doroudgar S, Stephens HN, Blackwood EA, Glembotski CC. Abstract 479: The ER Unfolded Protein Response Effector, ATF6, Promotes Proliferation and Maintains Pluripotency in Cardiac Stem Cells. Circ Res 2018. [DOI: 10.1161/res.123.suppl_1.479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Recent studies have suggested that multipotent stem cells residing in the adult heart, called cardiac stem cells (CSCs), mitigate damage in the infarcted or failing heart. Investigating the factors governing CSC proliferation and differentiation is key to understanding what role these cells play in the heart and in future therapeutic strategies. Additionally, activating transcription factor 6 (ATF6), an effector of the endoplasmic reticulum (ER) unfolded protein response (UPR), plays critical roles in development, as well as in the differentiation of certain stem cell types, though it has not been studied in this regard in the heart. Our lab has demonstrated that ATF6 in cardiac myocytes is cardioprotective
in vivo
during ischemia/reperfusion partly by virtue of its ability to induce an antioxidant gene program that reduces damaging reactive oxygen species (ROS). However, ATF6, and its involvement in antioxidant gene induction, have not been studied in CSCs. Therefore, here we hypothesized that activation of the ATF6 branch of the UPR in CSCs is important for their proliferation and differentiation, given that ROS is known to be essential for these processes. To address this hypothesis, we subjected cultured mouse CSCs to simulated ischemia and observed increased ATF6 target gene mRNA levels. This demonstrates that, despite their undifferentiated status, CSCs have a functional UPR, which can be activated in response to ischemic stress. ATF6 loss of function (LOF) in CSCs, via RNAi or chemical inhibitor, yielded a basal decrease in cell viability and an increase in several differentiation markers, similar to the effect of dexamethasone differentiation stimulus. Increased ROS was also observed in an ATF6 LOF model. Strikingly, cotreatment with a chemical ROS inhibitor significantly rescued cell viability and reduced markers of differentiation in CSCs with reduced ATF6 function. These results suggest that CSCs require a basal level of ATF6 activity to maintain their proliferation and pluripotentcy
in vitro
and that this is mediated by the role of ATF6 in the mitigation of ROS. This is an important finding given that stem cell expansion
in vitro
is a critical step in the characterization of stem cells and their use in many therapeutic treatment strategies.
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26
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Blackwood EA, Azizi K, Thuerauf DJ, Paxman RJ, Plate L, Kelly JW, Wiseman RL, Glembotski CC. Abstract 547: Pharmacologic ATF6 Activation Confers Global Protection in Widespread Disease Models by Reprogramming Cellular Proteostasis. Circ Res 2018. [DOI: 10.1161/res.123.suppl_1.547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pharmacologic activation of stress-responsive signaling pathways provides a promising approach for ameliorating imbalances in proteostasis associated with diverse diseases. However, this approach has not been employed
in vivo
. Here, using a mouse model of myocardial ischemia/reperfusion, we showed that selective pharmacologic activation of the ATF6 arm of the unfolded protein response (UPR) during reperfusion, a typical clinical intervention point after myocardial infarction, transcriptionally reprograms proteostasis, ameliorates damage and preserves heart function. These effects were lost upon cardiac myocyte-specific
Atf6
deletion in the heart, demonstrating the critical role played by ATF6 in mediating pharmacologically activated proteostasis-based protection of the heart. Pharmacological activation of ATF6 was also protective in renal and cerebral ischemia/reperfusion models, demonstrating its widespread utility. Thus, pharmacologic activation of ATF6 represents a first-in-class proteostasis-based therapeutic strategy for ameliorating ischemia/reperfusion damage, underscoring its unique translational potential for treating a wide range of pathologies caused by imbalanced proteostasis.
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Affiliation(s)
| | | | | | | | - Lars Plate
- The Scripps Rsch Institute, La Jolla, CA
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27
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Arrieta A, Blackwood EA, Aivati C, Stauffer WT, Santo Domingo M, Bilal AS, Sarakki AV, Thuerauf DJ, Doroudgar S, Glembotski CC. Abstract 352: Manf, a Structurally Unique Redox-sensitive Chaperone, Restores Er-protein Folding in the Ischemic Heart. Circ Res 2018. [DOI: 10.1161/res.123.suppl_1.352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
In cardiomyocytes, secreted and membrane proteins critical for heart function are synthesized and folded in the sarcoplasmic/endoplasmic reticulum (SR/ER). We previously showed that myocardial ischemia decreases oxygen required for disulfide bond formation in nascent proteins, causing ER stress, i.e. the toxic accumulation of unfolded proteins, which contributes to cardiomyocyte death. In response to ER stress, the transcription factor ATF6 induces various ER-resident proteins that restore SR/ER protein folding, including ER chaperones. We found that ATF6 induces mesencephalic astrocyte-derived neurotrophic factor (MANF), a recently identified protein of unknown function. MANF is structurally unique, so its function could not be inferred by analogy to other proteins. Since we found that MANF is an ATF6-inducible ER-resident protein we hypothesized that it functions as a chaperone, and since MANF has 8 cysteine residues that are conserved in a wide range of species, that its chaperone function is redox-regulated and protective in the ischemic heart.
Methods:
The ability of recombinant MANF (rMANF) to suppress misfolded protein aggregation was examined in an
in vitro
chaperone assay. The effect of MANF knockdown on cell viability during simulated ischemia (sI) was determined in neonatal rat ventricular myocytes (NRVM). The effect of MANF loss-of-function in the ischemic heart,
in vivo
, was determined in a novel mouse model in which MANF is knocked down in cardiomyocytes.
Results:
rMANF formed disulfide-dependent complexes with and suppressed aggregation of model misfolded proteins
in vitro
, and these effects were lost when the cysteines in rMANF were mutated to alanine. In NRVM, MANF knockdown decreased viability during simulated ischemia; this viability deficit was restored upon ectopic expression of wild type, but not mutant MANF. MANF knockdown in the heart,
in vivo
, increased ischemia/reperfusion damage, and this damage was mitigated using an AAV9-based gene therapy approach to restore MANF expression.
Conclusions:
MANF is a novel redox-sensitive SR/ER-resident chaperone that is a critical contributor to SR/ER protein folding during the adaptive ER stress response and mitigates ischemia/reperfusion damage in the heart.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Shirin Doroudgar
- DZHK (German Cntr for Cardiovascular Rsch), Partner Site Heidelberg/Mannheim, Heidelberg, Germany
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28
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Blackwood EA, Plate L, Paxman RJ, Malter K, Wiseman L, Kelly J, Glembotski CC. Abstract 138: Identification of a Novel Small Molecule Activator of ATF6 that Confers Protection Against Ischemia/reperfusion Injury in the Heart. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
Reactive oxygen species generated during myocardial ischemia/reperfusion (I/R) potentiate myocyte death and cardiac dysfunction. Recently, our lab published a newly described role for the adaptive ER stress sensor and transcription factor, ATF6, as a novel inducer of an adaptive antioxidant gene family. These results highlight the need for the development of small molecule drug candidates that preferentially activate endogenous ATF6 to promote the adaptive effects of ER stress and ameliorate myocardial I/R damage. To this end we used of a cell-based high throughput-screen to identify a novel small molecular activator of endogenous ATF6, herein called compound 147, and tested its efficacy in cardiac myocytes and in the heart.
Objective/Methods:
The ability of compound 147 to activate endogenous ATF6, as measured by nuclear localization of ATF6 and ATF6-specific target gene induction was examined in cultured neonatal rat ventricular myocytes (NRVM). The effects of compound 147 on the viability of NRVM treated with H2O2 to generate ROS, or simulated I/R were assessed. Finally, the effects of compound 147 in the mouse heart were examined
in vivo
by administering the compound to mice and, 24h later, determining the effects of simulated I/R on cardiac myocytes isolated from the mice, or determining the effects of
ex vivo
I/R on hearts isolated from compound 147-treated mice.
Results:
Compared to a control compound, treatment of NRVM with compound 147 specifically and acutely activated ATF6 and primed cells to mount an adaptive response when treated with H2O2 or subjected to simulated I/R. Treatment of both neonatal and adult ventricular myocytes with compound 147 increased survival in cells subjected to simulated I/R. Compared to control, the cardiac myocytes and hearts from mice treated with compound 147 exhibited increased viability and functional recovery in response to I/R, respectively.
Conclusions:
Compound 147 specifically activates ATF6 in cardiac myocytes and confers cardioprotection during I/R,
in vitro
and
in vivo
. Thus, compound 147 represents a potential first- in-class small molecule drug candidate that enhances myocardial recovery from I/R damage, specifically by activating the endogenous adaptive ATF6 gene program in the heart.
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Affiliation(s)
| | - Lars Plate
- The Scripps Rsch Institute, La Jolla, CA
| | | | | | | | - Jeff Kelly
- The Scripps Rsch Institute, La Jolla, CA
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29
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Stauffer WT, Azizi K, Blackwood EA, Kaufman RJ, Glembotski CC. Abstract 257: Endogenous Activating Transcription Factor 6 Preserves Heart Structure and Function in a Mouse Model of Myocardial Infarction-induced Heart Failure. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
The ER stress response is activated by the accumulation of misfolded, toxic proteins in the endoplasmic reticulum (ER), and upregulates proteins that restore ER protein-folding capacity. The ER-transmembrane protein, activating transcription factor 6 (ATF6) senses ER stress and responds by transcriptionally inducing many of these genes and is thus a key component of the adaptive ER stress response. We previously showed that in the heart, ischemia activates ATF6. Furthermore, transgenic mouse hearts expressing a conditionally activated form of ATF6, and subjected to
ex vivo
ischemia/reperfusion, exhibited preserved heart function and smaller infarcts. Our lab also showed that by serving as a novel inducer of a global anti-oxidant gene program, endogenous ATF6 limits cardiac damage caused by reactive oxygen species during reperfusion. However, the effect of endogenous ATF6 in the failing heart is not known. Given that acute ischemia caused by occlusion of the coronary arteries is the cause of myocardial infarction (MI), we hypothesized that endogenous ATF6 limits infarct size and preserves heart function during MI. Additionally, since deleterious cardiac remodeling and heart failure can be long-term consequences of MI, we hypothesized that ATF6 can mitigate these effects.
Objective/Methods:
To examine the role of endogenous ATF6 in heart failure,
in vivo,
we used a mouse model of MI-induced heart failure in mice with a global deletion of the ATF6 gene (ATF6 KO). Infarct size was measured by TTC staining and heart function was observed via longitudinal echocardiogram.
Results:
We found that following infarction, ATF6 KO mouse hearts had larger infarcts compared to control. Thus, ischemic cardiac tissue in the peri-infarct region requires ATF6 to limit cardiac myocyte death. Interestingly, ejection fraction following MI decreased more over 13 weeks in ATF6 KO mice relative to control. While control and ATF6 KO mouse hearts hypertrophied to a similar degree, KO mice showed greater cardiac dilation.
Conclusions:
Together these findings show for the first time that endogenous ATF6 acts to preserve heart structure and function in an MI model of heart failure, suggesting that ATF6 may be a viable therapeutic target for treatment of this disease.
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30
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Arrieta A, Blackwood EA, Stauffer WT, Santo Domingo M, Pentoney AN, Thuerauf DJ, Doroudgar S, Glembotski CC. Abstract 2: MANF, A Structurally Unique Redox-Sensitive Chaperone, Restores ER Protein Folding in the Ischemic Heart. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
In cardiomyocytes, most secreted and membrane proteins are synthesized and folded in the sarcoplasmic/endoplasmic reticulum (SR/ER). We previously showed that during myocardial ischemia, decreased oxygen creates a reducing environment in the SR/ER, preventing protein disulfide isomerases (PDIs) from forming disulfide bonds in nascent proteins, causing ER stress, i.e. the toxic accumulation of unfolded proteins which contributes to cardiomyocyte death. In response to ER stress, the transcription factor, ATF6 induces chaperones that restore SR/ER protein folding. We found that ATF6 also induces mesencephalic astrocyte-derived neurotrophic factor (MANF), a recently identified protein of unknown function. MANF is structurally unique, so its function cannot be inferred from other proteins. Since MANF is induced by ATF6, is ER-localized, and contains a conserved redox-sensitive motif found in PDIs, we hypothesized that MANF is a redox-sensitive chaperone that optimizes cardiomyocyte viability during ischemia.
Methods:
The redox status of MANF during reductive ER stress and the ability of MANF to bind misfolded proteins during ischemia were assessed in neonatal rat ventricular myocytes (NRVM). The ability of recombinant MANF to suppress aggregation of misfolded proteins was examined in an
in vitro
chaperone assay. Finally, the effects of MANF loss-of-function in the ischemic heart,
in vivo
, were determined by generating a transgenic mouse model that expresses a cardiomyocyte-specific MANF-targeted microRNA.
Results:
In NRVM subjected to ER stress MANF was as sensitive to changes in ER redox status as the sentinel PDI, PDIA1. Moreover, MANF formed disulfide-linked complexes with misfolded proteins during ischemia-mediated ER stress. Under reducing conditions, recombinant MANF suppressed aggregation of model misfolded proteins,
in vitro
. MANF knockdown in the heart,
in vivo
, increased damage from myocardial infarction, and an AAV9-based gene therapy approach rescued the effects of MANF deficiency,
in vivo.
Conclusions:
MANF is a redox-sensitive SR/ER-resident chaperone that is a critical contributor to SR/ER protein folding during the adaptive ER stress response and decreases tissue damage in the ischemic heart.
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Affiliation(s)
| | | | | | | | | | | | - Shirin Doroudgar
- Dept of Cardiology, Angiology, and Pneumology, Univ Hosp Heidelberg, Germany, San Diego, CA
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31
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Gray CBB, Suetomi T, Xiang S, Mishra S, Blackwood EA, Glembotski CC, Miyamoto S, Westenbrink BD, Brown JH. CaMKIIδ subtypes differentially regulate infarct formation following ex vivo myocardial ischemia/reperfusion through NF-κB and TNF-α. J Mol Cell Cardiol 2017; 103:48-55. [PMID: 28077321 DOI: 10.1016/j.yjmcc.2017.01.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 01/04/2017] [Accepted: 01/05/2017] [Indexed: 02/08/2023]
Abstract
Deletion of Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) has been shown to protect against in vivo ischemia/reperfusion (I/R) injury. It remains unclear which CaMKIIδ isoforms and downstream mechanisms are responsible for the salutary effects of CaMKIIδ gene deletion. In this study we sought to compare the roles of the CaMKIIδB and CaMKIIδC subtypes and the mechanisms by which they contribute to ex vivo I/R damage. WT, CaMKIIδKO, and mice expressing only CaMKIIδB or δC were subjected to ex vivo global ischemia for 25min followed by reperfusion. Infarct formation was assessed at 60min reperfusion by triphenyl tetrazolium chloride (TTC) staining. Deletion of CaMKIIδ conferred significant protection from ex vivo I/R. Re-expression of CaMKIIδC in the CaMKIIδKO background reversed this effect and exacerbated myocardial damage and dysfunction following I/R, while re-expression of CaMKIIδB was protective. Selective activation of CaMKIIδC in response to I/R was evident in a subcellular fraction enriched for cytosolic/membrane proteins. Further studies demonstrated differential regulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and tumor necrosis factor alpha (TNF-α) expression by CaMKIIδB and CaMKIIδC. Selective activation of CaMKIIδC was also observed and associated with NF-κB activation in neonatal rat ventricular myocytes (NRVMs) subjected to oxidative stress. Pharmacological inhibition of NF-κB or TNF-α significantly ameliorated infarct formation in WT mice and those that re-express CaMKIIδC, demonstrating distinct roles for CaMKIIδ subtypes in I/R and implicating acute activation of CaMKIIδC and NF-κB in the pathogenesis of reperfusion injury.
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Affiliation(s)
- Charles B B Gray
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - Takeshi Suetomi
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - Sunny Xiang
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA; In Vivo Pharmacological & Clinical Laboratory Services, The Jackson Laboratory, Bar Harbor, ME, USA
| | | | - Erik A Blackwood
- San Diego State University Heart Institute, Department of Biology, San Diego, CA, USA
| | | | - Shigeki Miyamoto
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA
| | - B Daan Westenbrink
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA; Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Joan Heller Brown
- Department of Pharmacology, University of California San Diego, San Diego, CA, USA.
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32
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Abstract
Cardiac myocytes are the cells responsible for the robust ability of the heart to pump blood throughout the circulatory system. Cardiac myocytes grow in response to a variety of physiological and pathological conditions; this growth challenges endoplasmic reticulum-protein quality control (ER-PQC), a major feature of which includes the unfolded protein response (UPR). ER-PQC and the UPR in cardiac myocytes growing under physiological conditions, including normal development, exercise, and pregnancy, are sufficient to support hypertrophic growth of each cardiac myocyte. However, the ER-PQC and UPR are insufficient to respond to the challenge of cardiac myocyte growth under pathological conditions, including myocardial infarction and heart failure. In part, this insufficiency is due to a continual decline in the expression levels of important adaptive UPR components as a function of age and during myocardial pathology. This chapter will discuss the physiological and pathological conditions unique to the heart that involves ER-PQC, and whether the UPR is adaptive or maladaptive under these circumstances.
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Affiliation(s)
- A Arrieta
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA
| | - E A Blackwood
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA
| | - C C Glembotski
- San Diego State University Heart Institute and the Department of Biology, San Diego State University, San Diego, CA, 92182, USA.
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33
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Jin JK, Blackwood EA, Azizi K, Thuerauf DJ, Fahem AG, Hofmann C, Kaufman RJ, Doroudgar S, Glembotski CC. ATF6 Decreases Myocardial Ischemia/Reperfusion Damage and Links ER Stress and Oxidative Stress Signaling Pathways in the Heart. Circ Res 2016; 120:862-875. [PMID: 27932512 DOI: 10.1161/circresaha.116.310266] [Citation(s) in RCA: 190] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/02/2016] [Accepted: 12/08/2016] [Indexed: 12/14/2022]
Abstract
RATIONALE Endoplasmic reticulum (ER) stress causes the accumulation of misfolded proteins in the ER, activating the transcription factor, ATF6 (activating transcription factor 6 alpha), which induces ER stress response genes. Myocardial ischemia induces the ER stress response; however, neither the function of this response nor whether it is mediated by ATF6 is known. OBJECTIVE Here, we examined the effects of blocking the ATF6-mediated ER stress response on ischemia/reperfusion (I/R) in cardiac myocytes and mouse hearts. METHODS AND RESULTS Knockdown of ATF6 in cardiac myocytes subjected to I/R increased reactive oxygen species and necrotic cell death, both of which were mitigated by ATF6 overexpression. Under nonstressed conditions, wild-type and ATF6 knockout mouse hearts were similar. However, compared with wild-type, ATF6 knockout hearts showed increased damage and decreased function after I/R. Mechanistically, gene array analysis showed that ATF6, which is known to induce genes encoding ER proteins that augment ER protein folding, induced numerous oxidative stress response genes not previously known to be ATF6-inducible. Many of the proteins encoded by the ATF6-induced oxidative stress genes identified here reside outside the ER, including catalase, which is known to decrease damaging reactive oxygen species in the heart. Catalase was induced by the canonical ER stressor, tunicamycin, and by I/R in cardiac myocytes from wild-type but not in cardiac myocytes from ATF6 knockout mice. ER stress response elements were identified in the catalase gene and were shown to bind ATF6 in cardiac myocytes, which increased catalase promoter activity. Overexpression of catalase, in vivo, restored ATF6 knockout mouse heart function to wild-type levels in a mouse model of I/R, as did adeno-associated virus 9-mediated ATF6 overexpression. CONCLUSIONS ATF6 serves an important role as a previously unappreciated link between the ER stress and oxidative stress gene programs, supporting a novel mechanism by which ATF6 decreases myocardial I/R damage.
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Affiliation(s)
- Jung-Kang Jin
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Erik A Blackwood
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Khalid Azizi
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Donna J Thuerauf
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Asal G Fahem
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Christoph Hofmann
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Randal J Kaufman
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Shirin Doroudgar
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.)
| | - Christopher C Glembotski
- From the San Diego State University Heart Institute and the Department of Biology, San Diego State University, CA (J.-K.J., E.A.B., K.A., D.J.T., A.G.F., C.H., S.D., C.C.G.); Department of Cardiology, Angiology, and Pneumology, University Hospital Heidelberg, Germany (C.H., S.D.); DZHK (German Centre for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg, Germany (C.H., S.D.); and Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA (R.J.K.).
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Blackwood EA, Glembotski CC. Abstract 292: The Role of the ATF6 Branch of the ER Stress Response in the Endocrine Heart. Circ Res 2016. [DOI: 10.1161/res.119.suppl_1.292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rationale:
Atrial natriuretic peptide (ANP) is stored in the heart in large dense core granules of atrial myocytes as a biologically inactive precursor, pro-ANP. Hemodynamic stress and atrial stretch stimulate coordinate secretion and proteolytic cleavage of pro-ANP to its bioactive form, ANP, which promotes renal salt excretion and vasodilation, which, together contribute to decreasing blood pressure. While the ATF6 branch of the ER stress response has been studied in ventricular tissue mouse models of myocardial ischemia and pathological hypertrophy, roles for ATF6 and ER stress on the endocrine function of atrial myocytes have not been studied.
Objective/Methods:
To address this gap in our knowledge, we knocked down ATF6 in primary cultured neonatal rat atrial myocytes (NRAMs) using a chemical inhibitor of the proteolytic cleavage site enabling ATF6 activation and siRNA and measured ANP expression and secretion basally and in response to alpha- adrenergic agonist stimulation using phenylephrine. We also compared the ANP secretion from wild- type mice and ATF6 knockout mice in an ex vivo Langendorff model of the isolated perfused heart.
Results:
ATF6 knockdown in NRAMs significantly impaired basal and phenylephrine-stimulated ANP secretion. ATF6 knockout mice displayed lower levels of ANP in atrial tissue at baseline as well as after phenylephrine treatment. Similarly, in the ex vivo isolated perfused heart model, less ANP was detected in effluent of ATF6 knockout hearts compared to wild-type hearts.
Conclusions:
The ATF6 branch of the ER stress response is necessary for efficient co-secretional processing of pro-ANP to ANP and for agonist-stimulated ANP secretion from atrial myocytes. As ANP is secreted in a regulated manner in response to a stimulus and pro-ANP is synthesized and packaged through the classical secretory pathway, we posit that ATF6 is required for adequate expression, folding, trafficking, processing and secretion of biologically active ANP from the endocrine heart.
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Arrieta A, Stauffer WT, Pentoney AN, Blackwood EA, Doroudgar S, Glembotski CC. Abstract 291: MANF, a Structurally Unique ER Stress-inducible Protein, Restores ER-protein Folding in ER Stressed Cardiac Myocytes and in the Ischemic Heart. Circ Res 2016. [DOI: 10.1161/res.119.suppl_1.291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The sarco/endoplasmic reticulum (SR/ER) of cardiomyocytes is a critical site of protein synthesis and folding, as most secreted and membrane proteins including receptors, growth factors, ion channels, and calcium-handling proteins are made at this location. Myocardial ischemia induces ER stress, during which toxic, misfolded proteins accumulate in the SR/ER and contribute to cardiomyocyte death. The branch of the ER stress response mediated by the transcription factor, ATF6, induces ER chaperones that restore SR/ER protein folding. We found that ATF6 also induces mesencephalic astrocyte-derived neurotrophic factor (MANF), a novel, ubiquitously expressed, ER-luminal protein of unknown function. MANF is structurally unique, thus its function cannot be inferred by structural analogy to known proteins. Since it is ATF6-inducible, and resides in the ER lumen, we hypothesized that MANF is an ER chaperone required for optimal viability of cardiac myocytes during ER stresses, including ischemia. The characteristics of MANF gene induction by ER stress, and the effects of MANF knockdown on the ER stress response and cell viability were determined in cultured neonatal rat ventricular myocytes (NRVM). The ability of recombinant MANF to restore structure and function to model misfolded proteins was also examined. Finally, the effects of MANF loss-of-function in the ischemic heart,
in vivo
, were determined by generating a transgenic mouse model that expresses a cardiomyocyte-specific MANF-targeted microRNA. MANF induction and functional characteristics phenocopied those of a well-studied ER chaperone, glucose-regulated protein 78 (Grp78). Like Grp78, MANF was induced by ER stress in an ATF6-dependent manner. Like knockdown of Grp78, knockdown of MANF in NRVM increased myocyte death in response to ER stress. Like recombinant Grp78, recombinant MANF exhibited a robust ability to restore structure and function to model misfolded proteins,
in vitro.
Finally, MANF knockdown in the heart,
in vivo
, increased damage in a mouse model of myocardial infarction. These results suggest that MANF is an SR/ER-resident chaperone required for restoration of SR/ER protein folding during the adaptive ER stress response, and decreasing tissue damage in the ischemic heart.
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