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Abstract
Heat stress is described as the cumulative detrimental effect caused by an imbalance between heat production within the body and heat dissipation. When cattle are exposed to heat stress with skin surface temperatures exceeding 35 °C, gene networks within and across cells respond to environmental heat loads with both intra and extracellular signals that coordinate cellular and whole-animal metabolism changes to store heat and rapidly increase evaporative heat loss. In this study, we examined evidence from genes known to be associated with heat tolerance (Hsp70, HSF1, HspB8, SOD1, PRLH, ATP1A1, MTOR, and EIF2AK4). This information could serve as valuable resource material for breeding programs aimed at increasing the thermotolerance of cattle.
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Affiliation(s)
- LuLan Zeng
- College of Life Sciences, Northwest A&F University, Yangling, China
| | - Kaixing Qu
- Yunnan Academy of Grassland and Animal Science, Kunming, China
| | - Jicai Zhang
- Yunnan Academy of Grassland and Animal Science, Kunming, China
| | - Bizhi Huang
- Yunnan Academy of Grassland and Animal Science, Kunming, China
| | - Chuzhao Lei
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Yangling, China
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Snow JP, Westlake G, Klofas LK, Jeon S, Armstrong LC, Swoboda KJ, George AL, Ess KC. Neuronal modeling of alternating hemiplegia of childhood reveals transcriptional compensation and replicates a trigger-induced phenotype. Neurobiol Dis 2020; 141:104881. [PMID: 32348881 DOI: 10.1016/j.nbd.2020.104881] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 04/18/2020] [Accepted: 04/24/2020] [Indexed: 01/30/2023] Open
Abstract
Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disease caused by heterozygous de novo missense mutations in the ATP1A3 gene that encodes the neuronal specific α3 subunit of the Na,K-ATPase (NKA) pump. Mechanisms underlying patient episodes including environmental triggers remain poorly understood, and there are no empirically proven treatments for AHC. In this study, we generated patient-specific induced pluripotent stem cells (iPSCs) and isogenic controls for the E815K ATP1A3 mutation that causes the most phenotypically severe form of AHC. Using an in vitro iPSC-derived cortical neuron disease model, we found elevated levels of ATP1A3 mRNA in AHC lines compared to controls, without significant perturbations in protein expression. Microelectrode array analyses demonstrated that in cortical neuronal cultures, ATP1A3+/E815K iPSC-derived neurons displayed less overall activity than neurons differentiated from isogenic mutation-corrected and unrelated control cell lines. However, induction of cellular stress by elevated temperature revealed a hyperactivity phenotype following heat stress in ATP1A3+/E815K neurons compared to control lines. Treatment with flunarizine, a drug commonly used to prevent AHC episodes, did not impact this stress-triggered phenotype. These findings support the use of iPSC-derived neuronal cultures for studying complex neurodevelopmental conditions such as AHC and provide a platform for mechanistic discovery in a human disease model.
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Affiliation(s)
- John P Snow
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Grant Westlake
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lindsay K Klofas
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA
| | - Soyoun Jeon
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Laura C Armstrong
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kathryn J Swoboda
- Center for Genomic Medicine, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Kevin C Ess
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.
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Parra V, Rothermel BA. Calcineurin signaling in the heart: The importance of time and place. J Mol Cell Cardiol 2017; 103:121-136. [PMID: 28007541 PMCID: PMC5778886 DOI: 10.1016/j.yjmcc.2016.12.006] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 12/12/2016] [Accepted: 12/16/2016] [Indexed: 12/20/2022]
Abstract
The calcium-activated protein phosphatase, calcineurin, lies at the intersection of protein phosphorylation and calcium signaling cascades, where it provides an essential nodal point for coordination between these two fundamental modes of intracellular communication. In excitatory cells, such as neurons and cardiomyocytes, that experience rapid and frequent changes in cytoplasmic calcium, calcineurin protein levels are exceptionally high, suggesting that these cells require high levels of calcineurin activity. Yet, it is widely recognized that excessive activation of calcineurin in the heart contributes to pathological hypertrophic remodeling and the progression to failure. How does a calcium activated enzyme function in the calcium-rich environment of the continuously contracting heart without pathological consequences? This review will discuss the wide range of calcineurin substrates relevant to cardiovascular health and the mechanisms calcineurin uses to find and act on appropriate substrates in the appropriate location while potentially avoiding others. Fundamental differences in calcineurin signaling in neonatal verses adult cardiomyocytes will be addressed as well as the importance of maintaining heterogeneity in calcineurin activity across the myocardium. Finally, we will discuss how circadian oscillations in calcineurin activity may facilitate integration with other essential but conflicting processes, allowing a healthy heart to reap the benefits of calcineurin signaling while avoiding the detrimental consequences of sustained calcineurin activity that can culminate in heart failure.
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Affiliation(s)
- Valentina Parra
- Advanced Centre for Chronic Disease (ACCDiS), Facultad Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Santiago,Chile; Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chie, Santiago, Chile
| | - Beverly A Rothermel
- Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Centre, Dallas, TX, USA; Department of Molecular Biology, University of Texas Southwestern Medical Centre, Dallas, TX, USA.
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Sahoo SS, Mishra C, Rout M, Nayak G, Mohanty ST, Panigrahy KK. Comparative in silico and protein-protein interaction network analysis of ATP1A1 gene. GENE REPORTS 2016. [DOI: 10.1016/j.genrep.2016.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Uyhelji HA, Cheng C, Besansky NJ. Transcriptomic differences between euryhaline and stenohaline malaria vector sibling species in response to salinity stress. Mol Ecol 2016; 25:2210-25. [PMID: 26945667 DOI: 10.1111/mec.13609] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 01/09/2016] [Accepted: 02/22/2016] [Indexed: 01/04/2023]
Abstract
Evolution of osmoregulatory systems is a key factor in the transition of species between fresh- and saltwater habitats. Anopheles coluzzii and Anopheles merus are stenohaline and euryhaline malaria vector mosquitoes belonging to a larger group of sibling species, the Anopheles gambiae complex, which radiated in Africa within the last 2 million years. Comparative ecological genomics of these vector species can provide insight into the mechanisms that permitted the rapid radiation of this species complex into habitats of contrasting salinity. Here, we use RNA-Seq to investigate gene expression differences between An. coluzzii and An. merus after briefly exposing both young and old larval instars of each species to either saltwater (SW) or freshwater (FW). Our study aims to identify candidate genes and pathways responsible for the greater SW tolerance of An. merus. Our results are congruent with the ability of gene induction to mediate salinity tolerance, with both species showing increasing amounts of differential gene expression between SW and FW as salt concentrations increase. Besides ion transporters such as AgAE2 that may serve as effectors for osmoregulation, we also find mitogen-activated protein kinases that may serve in a phosphorylation signalling pathway responding to salinity, and report potential cross-talk between the mosquito immune response and osmoregulation. This study provides a key step towards applying the growing molecular knowledge of these malaria vectors to improve understanding of their ecological tolerances and habitat occupancy.
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Affiliation(s)
- Hilary A Uyhelji
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, 46556, USA.,Functional Genomics Team, Civil Aerospace Medical Institute, Federal Aviation Administration, Oklahoma City, OK, 73169, USA
| | - Changde Cheng
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Nora J Besansky
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, 46556, USA
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Mavrogonatou E, Papadimitriou K, Urban JP, Papadopoulos V, Kletsas D. Deficiency in the α1 subunit of Na+/K+-ATPase enhances the anti-proliferative effect of high osmolality in nucleus pulposus intervertebral disc cells. J Cell Physiol 2015; 230:3037-48. [PMID: 25967398 DOI: 10.1002/jcp.25040] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/05/2015] [Indexed: 12/31/2022]
Abstract
Intervertebral disc cells are constantly exposed to a hyperosmotic environment. Among cellular responses towards this stress is the inhibition of proliferation through the activation of p38 MAPK and p53. In an effort to further elucidate the biochemical pathways triggered by hyperosmotic stress, we assessed the high osmolality-induced transcriptional changes of bovine nucleus pulposus cells using whole-genome arrays. A 5- and a 24-h hyperosmotic treatment led to the differential expression of >100 and >200 genes, respectively, including nine genes encoding transporters (SLC4A11, SLC5A3, ATP1A1, SLC38A2, KCNK17, KCTD20, KCTD11, SLC7A5, and CLCA2). Differences in the transcriptional profile of these selected genes, as indicated by the microarrays experiments, were validated by qRT-PCR in 2D and 3D cell cultures, under hyperosmolar salt and sorbitol conditions, revealing the presence of a common triggering signal for osmotic adaptation. The key signaling molecules p38 MAPK and p53 were demonstrated to differently participate in the regulation of the aforementioned transporters. Finally, siRNA-mediated knocking-down of each one of the three transporters with the highest and sustained over-expression (i.e., SLC4A11, SLC5A3, and ATP1A1) had a distinct outcome on the transcriptional profile of the other transporters, on p38 MAPK and p53 phosphorylation and consequently on cell cycle progression. The inhibition of ATP1A1 had the most prominent effect on the transcription of the rest of the transporters and was found to enhance the anti-proliferative effect of hyperosmotic conditions through an increased G2/M cell cycle block, ascribing to this pump a central role in the osmoregulatory response of nucleus pulposus cells.
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Affiliation(s)
- Eleni Mavrogonatou
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
| | - Konstantinos Papadimitriou
- Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, Athens, Greece
| | - Jill P Urban
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, United Kingdom
| | - Vassilios Papadopoulos
- The Research Institute of the McGill University Health Centre, Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Dimitris Kletsas
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Centre for Scientific Research "Demokritos", Athens, Greece
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Li Z, Langhans SA. Transcriptional regulators of Na,K-ATPase subunits. Front Cell Dev Biol 2015; 3:66. [PMID: 26579519 PMCID: PMC4620432 DOI: 10.3389/fcell.2015.00066] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 10/05/2015] [Indexed: 12/20/2022] Open
Abstract
The Na,K-ATPase classically serves as an ion pump creating an electrochemical gradient across the plasma membrane that is essential for transepithelial transport, nutrient uptake and membrane potential. In addition, Na,K-ATPase also functions as a receptor, a signal transducer and a cell adhesion molecule. With such diverse roles, it is understandable that the Na,K-ATPase subunits, the catalytic α-subunit, the β-subunit and the FXYD proteins, are controlled extensively during development and to accommodate physiological needs. The spatial and temporal expression of Na,K-ATPase is partially regulated at the transcriptional level. Numerous transcription factors, hormones, growth factors, lipids, and extracellular stimuli modulate the transcription of the Na,K-ATPase subunits. Moreover, epigenetic mechanisms also contribute to the regulation of Na,K-ATPase expression. With the ever growing knowledge about diseases associated with the malfunction of Na,K-ATPase, this review aims at summarizing the best-characterized transcription regulators that modulate Na,K-ATPase subunit levels. As abnormal expression of Na,K-ATPase subunits has been observed in many carcinoma, we will also discuss transcription factors that are associated with epithelial-mesenchymal transition, a crucial step in the progression of many tumors to malignant disease.
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Affiliation(s)
- Zhiqin Li
- Nemours Center for Childhood Cancer Research, Nemours/Alfred I. duPont Hospital for Children Wilmington, DE, USA
| | - Sigrid A Langhans
- Nemours Center for Childhood Cancer Research, Nemours/Alfred I. duPont Hospital for Children Wilmington, DE, USA
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Kashyap N, Kumar P, Deshmukh B, Bhat S, Kumar A, Chauhan A, Bhushan B, Singh G, Sharma D. Association of ATP1A1 gene polymorphism with thermotolerance in Tharparkar and Vrindavani cattle. Vet World 2015; 8:892-7. [PMID: 27047171 PMCID: PMC4774683 DOI: 10.14202/vetworld.2015.892-897] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/13/2015] [Accepted: 06/20/2015] [Indexed: 11/24/2022] Open
Abstract
Aim: One of the major biochemical aspects of thermoregulation is equilibrium of ion gradient across biological membranes. Na+/K+-ATPase, a member of P type-ATPase family, is a major contributor to the mechanism that actively controls cross-membrane ion gradient. Thus, we examined ATP1A1 gene that encodes alpha-1 chain of Na+/K+-ATPase, for genetic polymorphisms. Materials and Methods: A total of 100 Vrindavani (composite cross strain of Hariana x Holstein-Friesian/Brown Swiss/Jersey) and 64 Tharparkar (indigenous) cattle were screened for genetic polymorphism in ATP1A1 gene, using polymerase chain reaction single-strand conformation polymorphism and DNA sequencing. For association studies, rectal temperature (RT) and respiration rate (RR) of all animals were recorded twice daily for 3 seasons. Results: A SNP (C2789A) was identified in exon 17 of ATP1A1 gene. Three genotypes namely CC, CA, and AA were observed in both, Vrindavani and Tharparkar cattle. The gene frequencies in Tharparkar and Vrindavani for allele A were 0.51 and 0.48, and for allele C were 0.49 and 0.52, respectively, which remained at intermediate range. Association study of genotypes with RT and RR in both cattle population revealed that the animals with genotype CC exhibited significantly lower RT and higher heat tolerance coefficient than CA and AA genotypes. Conclusion: Differential thermoregulation between different genotypes of ATP1A1 gene indicate that the ATP1A1 gene could be potentially contributing to thermotolerance in both, Tharparkar, an indigenous breed and Vrindavani, a composite crossbred cattle.
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Affiliation(s)
- Neeraj Kashyap
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Pushpendra Kumar
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Bharti Deshmukh
- Department of Animal Genetics and Breeding, Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India
| | - Sandip Bhat
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Amit Kumar
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Anuj Chauhan
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Bharat Bhushan
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Gyanendra Singh
- Division of Physiology and Climatology, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Deepak Sharma
- Division of Animal Genetics, Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
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Creb and Sp/Krüppel response elements cooperate to control rat TRH gene transcription in response to cAMP. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1809:191-9. [PMID: 21266205 DOI: 10.1016/j.bbagrm.2011.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 01/18/2011] [Accepted: 01/20/2011] [Indexed: 12/17/2022]
Abstract
Expression of hypophysiotropic TRH, that controls thyroid axis activity, is increased by cold exposure; this effect is mimicked in rat hypothalamic cells incubated with norepinephrine or cAMP analogs. TRH proximal promoter contains three putative CRE: Site-4 or CRE-1 that overlaps an element recognized by thyroid hormone receptors, CRE-2 with adjacent sequences GC box or CACCC recognized by Sp/Krüppel factors (extended CRE-2), and AP-1 sites flanking a GRE(1/2). To evaluate the role of each element in the cAMP response, these sites were mutated or deleted in rat TRH promoter linked to luciferase gene (TRH-luc) and co-transfected with β-gal expression vector in various cell lines; C6 cells gave the highest response to forskolin. Basal activity was most affected by mutations or deletion of CRE-2 site, or CACCC (50-75% of wild type-WT). Forskolin-induced 3× stimulation in WT which decreased 25% with CRE-1 or AP-1 deletions, but 50% when CRE-2 or its 5' adjacent GC box was altered. SH-SY5Y cells co-transfected with CREB-expression vector increased dB-cAMP response in the wild type but not in the CRE-2 mutated plasmid; cotransfecting CREB-A (a dominant negative expression vector) strongly diminished basal or cAMP response. Primary cultures of hypothalamic cells transfected with plasmids containing deletions of CRE-1, CRE-2, or extended CRE-2 failed to respond to forskolin when CRE-2 was modified. These results corroborate the CRE-2 site as the main cAMP-response element of rat TRH promoter, not exclusive of transcription factors of hypothalamic cells, and stress the relevance of adjacent Sp-1 sites, important mediators of some metabolic hormones.
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Clifford RJ, Kaplan JH. Regulation of Na,K-ATPase subunit abundance by translational repression. J Biol Chem 2009; 284:22905-15. [PMID: 19553675 PMCID: PMC2755698 DOI: 10.1074/jbc.m109.030536] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 06/22/2009] [Indexed: 01/10/2023] Open
Abstract
The Na,K-ATPase is an alphabeta heterodimer responsible for maintaining fluid and electrolyte homeostasis in mammalian cells. We engineered Madin-Darby canine kidney cell lines expressing alpha(1)FLAG, beta(1)FLAG, or beta(2)MYC subunits via a tetracycline-regulated promoter and a line expressing both stable beta(1)MYC and tetracycline-regulated beta(1)FLAG to examine regulatory mechanisms of sodium pump subunit expression. When overexpression of exogenous beta(1)FLAG increased total beta subunit levels by >200% without changes in alpha subunit abundance, endogenous beta(1) subunit (beta(1)E) abundance decreased. beta(1)E down-regulation did not occur during beta(2)MYC overexpression, indicating isoform specificity of the repression mechanism. Measurements of RNA stability and content indicated that decreased beta subunit expression was not accompanied by any change in mRNA levels. In addition, the degradation rate of beta subunits was not altered by beta(1)FLAG overexpression. Cells stably expressing beta(1)MYC, when induced to express beta(1)FLAG subunits, showed reduced beta(1)MYC and beta(1)E subunit abundance, indicating that these effects occur via the coding sequences of the down-regulated polypeptides. In a similar way, Madin-Darby canine kidney cells overexpressing exogenous alpha(1)FLAG subunits exhibited a reduction of endogenous alpha(1) subunits (alpha(1)E) with no change in alpha mRNA levels or beta subunits. The reduction in alpha(1)E compensated for alpha(1)FLAG subunit expression, resulting in unchanged total alpha subunit abundance. Thus, regulation of alpha subunit expression maintained its native level, whereas beta subunit was not as tightly regulated and its abundance could increase substantially over native levels. These effects also occurred in human embryonic kidney cells. These data are the first indication that cellular sodium pump subunit abundance is modulated by translational repression. This mechanism represents a novel, potentially important mechanism for regulation of Na,K-ATPase expression.
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Affiliation(s)
- Rebecca J. Clifford
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607
| | - Jack H. Kaplan
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607
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Wang G, Kawakami K, Gick G. Regulation of Na,K-ATPase alpha1 subunit gene transcription in response to low K(+): role of CRE/ATF- and GC box-binding proteins. J Cell Physiol 2007; 213:167-76. [PMID: 17477345 DOI: 10.1002/jcp.21107] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Na,K-ATPase expression is upregulated in mammalian cells as a consequence of persistent inhibition of Na,K-ATPase enzymatic activity by low external K(+). We previously demonstrated that exposure of neonatal rat cardiac myocytes to low K(+) increased Na,K-ATPase alpha1 subunit mRNA content and promoter activity. In this work, we utilized transient transfection studies with rat Na,K-ATPase alpha1 subunit 5'-flanking region deletion plasmids to identify DNA sequences required for low K(+)-mediated stimulation of alpha1 subunit promoter expression in cardiac myocytes. Maximal low K(+)-responsiveness of the alpha1 promoter was found to be dependent on nucleotides from -102 to -62 and a downstream region from +53 to +261. Further analysis of the upstream low K(+)-responsive region using mutant constructs revealed that a CRE/ATF site at -70 to -63 and a GC box motif at -57 to -48 were both required for the effect of low K(+) on alpha1 subunit gene transcription. Electrophoretic mobility shift assays revealed that low K(+) increased binding of transcription factors to the GC box and, to a lesser extent, to the CRE/ATF site. Western blot analysis demonstrated that exposure of cardiac myocytes to low K(+) resulted in increased nuclear content of Sp1, Sp3 and CREB-1. Finally, a selective increase in phosphorylation of Sp1 was found in nuclear extracts from low K(+)-treated cells. We conclude that low K(+)-mediated upregulation of Na,K-ATPase alpha1 subunit gene expression in neonatal rat cardiac myocytes is dependent, in part, on CRE/ATF- and GC box-binding transcription factors.
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Affiliation(s)
- Gang Wang
- Department of Biochemistry, Center for Cardiovascular and Muscle Research, State University of New York Health Science Center at Brooklyn, Brooklyn, New York 11203, USA
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