1
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Tozzi M, Larsen AT, Lange SC, Giannuzzo A, Andersen MN, Novak I. The P2X7 receptor and pannexin-1 are involved in glucose-induced autocrine regulation in β-cells. Sci Rep 2018; 8:8926. [PMID: 29895988 PMCID: PMC5997690 DOI: 10.1038/s41598-018-27281-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 05/31/2018] [Indexed: 01/02/2023] Open
Abstract
Extracellular ATP is an important short-range signaling molecule that promotes various physiological responses virtually in all cell types, including pancreatic β-cells. It is well documented that pancreatic β-cells release ATP through exocytosis of insulin granules upon glucose stimulation. We hypothesized that glucose might stimulate ATP release through other non-vesicular mechanisms. Several purinergic receptors are found in β-cells and there is increasing evidence that purinergic signaling regulates β-cell functions and survival. One of the receptors that may be relevant is the P2X7 receptor, but its detailed role in β-cell physiology is unclear. In this study we investigated roles of the P2X7 receptor and pannexin-1 in ATP release, intracellular ATP, Ca2+ signals, insulin release and cell proliferation/survival in β-cells. Results show that glucose induces rapid release of ATP and significant fraction of release involves the P2X7 receptor and pannexin-1, both expressed in INS-1E cells, rat and mouse β-cells. Furthermore, we provide pharmacological evidence that extracellular ATP, via P2X7 receptor, stimulates Ca2+ transients and cell proliferation in INS-1E cells and insulin secretion in INS-1E cells and rat islets. These data indicate that the P2X7 receptor and pannexin-1 have important functions in β-cell physiology, and should be considered in understanding and treatment of diabetes.
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Affiliation(s)
- Marco Tozzi
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Anna T Larsen
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Sofie C Lange
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Andrea Giannuzzo
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Martin N Andersen
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Ivana Novak
- Section for Cell Biology and Physiology, August Krogh Building, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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2
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Kragstrup TW, Andersen MN, Schiøttz-Christensen B, Jurik AG, Hvid M, Deleuran B. Increased interleukin (IL)-20 and IL-24 target osteoblasts and synovial monocytes in spondyloarthritis. Clin Exp Immunol 2017; 189:342-351. [PMID: 28369789 DOI: 10.1111/cei.12973] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2017] [Indexed: 12/12/2022] Open
Abstract
The pathogenesis of spondyloarthritis (SpA) involves activation of the innate immune system, inflammation and new bone formation. The two cytokines interleukin (IL)-20 and IL-24 have been shown to link innate immune activation and tissue homeostasis. We hypothesized that these two cytokines are secreted as part of activation of the innate immune system and affect bone homeostasis in SpA. IL-20 and IL-24 were measured in plasma from axial SpA patients (n = 83). Peripheral SpA patients (n = 16) were included for in-vitro cell culture studies. The plasma IL-20 and IL-24 levels were increased in SpA patients compared with healthy controls (HCs) by 57 and 83%, respectively (both P < 0·0001). The Toll-like receptor 4-induced secretion of the two cytokines was greater in SpA peripheral blood mononuclear cells (PBMCs) compared with HC PBMCs. IL-20 and IL-24 increased the production of monocyte chemoattractant protein-1 by activated SpA synovial fluid monocytes, decreased the production of Dickkopf-1 by SpA fibroblast-like synovial cells and induced mineralization in human osteoblasts. Taken together, our findings indicate disease-aggravating functions of IL-20 and IL-24 in SpA.
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Affiliation(s)
- T W Kragstrup
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark
| | - M N Andersen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - B Schiøttz-Christensen
- Spine Centre of Southern Denmark, Hospital Lillebaelt, Middelfart, Denmark.,Institute of Regional Health Services Research, University of Southern Denmark, Odense, Denmark
| | - A G Jurik
- Department of Radiology, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - M Hvid
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - B Deleuran
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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3
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Nonboe AW, Krigslund O, Soendergaard C, Skovbjerg S, Friis S, Andersen MN, Ellis V, Kawaguchi M, Kataoka H, Bugge TH, Vogel LK. HAI-2 stabilizes, inhibits and regulates SEA-cleavage-dependent secretory transport of matriptase. Traffic 2017; 18:378-391. [PMID: 28371047 DOI: 10.1111/tra.12482] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [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: 10/05/2016] [Revised: 03/24/2017] [Accepted: 03/24/2017] [Indexed: 11/28/2022]
Abstract
It has recently been shown that hepatocyte growth factor activator inhibitor-2 (HAI-2) is able to suppress carcinogenesis induced by overexpression of matriptase, as well as cause regression of individual established tumors in a mouse model system. However, the role of HAI-2 is poorly understood. In this study, we describe 3 mutations in the binding loop of the HAI-2 Kunitz domain 1 (K42N, C47F and R48L) that cause a delay in the SEA domain cleavage of matriptase, leading to accumulation of non-SEA domain cleaved matriptase in the endoplasmic reticulum (ER). We suggest that, like other known SEA domains, the matriptase SEA domain auto-cleaves and reflects that correct oligomerization, maturation, and/or folding has been obtained. Our results suggest that the HAI-2 Kunitz domain 1 mutants influence the flux of matriptase to the plasma membrane by affecting the oligomerization, maturation and/or folding of matriptase, and as a result the SEA domain cleavage of matriptase. Two of the HAI-2 Kunitz domain 1 mutants investigated (C47F, R48L and C47F/R48L) also displayed a reduced ability to proteolytically silence matriptase. Hence, HAI-2 separately stabilizes matriptase, regulates the secretory transport, possibly via maturation/oligomerization and inhibits the proteolytic activity of matriptase in the ER, and possible throughout the secretory pathway.
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Affiliation(s)
- Annika W Nonboe
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark
| | - Oliver Krigslund
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark
| | - Christoffer Soendergaard
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark.,Department of Gastroenterology, Medical Section, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Signe Skovbjerg
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark
| | - Stine Friis
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark.,Department of Molecular Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen East, Denmark
| | - Martin N Andersen
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Vincent Ellis
- School of Biological Sciences, University of East Anglia, Norwich, UK
| | - Makiko Kawaguchi
- Section of Oncopathology and Regenerative Biology, Department of Pathology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan
| | - Hiroaki Kataoka
- Section of Oncopathology and Regenerative Biology, Department of Pathology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan
| | - Thomas H Bugge
- Proteases and Tissue Remodeling Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Lotte K Vogel
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen North, Denmark
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4
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Andersen MN, Hefting LL, Steffensen AB, Schmitt N, Olesen SP, Olsen JV, Lundby A, Rasmussen HB. Protein kinase A stimulates Kv7.1 surface expression by regulating Nedd4-2-dependent endocytic trafficking. Am J Physiol Cell Physiol 2015; 309:C693-706. [PMID: 26405101 DOI: 10.1152/ajpcell.00383.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [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: 12/02/2014] [Accepted: 09/15/2015] [Indexed: 11/22/2022]
Abstract
The potassium channel Kv7.1 plays critical physiological roles in both heart and epithelial tissues. In heart, Kv7.1 and the accessory subunit KCNE1 forms the slowly activating delayed-rectifier potassium current current, which is enhanced by protein kinase A (PKA)-mediated phosphorylation. The observed current increase requires both phosphorylation of Kv7.1 and the presence of KCNE1. However, PKA also stimulates Kv7.1 currents in epithelial tissues, such as colon, where the channel does not coassemble with KCNE1. Here, we demonstrate that PKA activity significantly impacts the subcellular localization of Kv7.1 in Madin-Darby canine kidney cells. While PKA inhibition reduced the fraction of channels at the cell surface, PKA activation increased it. We show that PKA inhibition led to intracellular accumulation of Kv7.1 in late endosomes/lysosomes. By mass spectroscopy we identified eight phosphorylated residues on Kv7.1, however, none appeared to play a role in the observed response. Instead, we found that PKA acted by regulating endocytic trafficking involving the ubiquitin ligase Nedd4-2. We show that a Nedd4-2-resistant Kv7.1-mutant displayed significantly reduced intracellular accumulation upon PKA inhibition. Similar effects were observed upon siRNA knockdown of Nedd4-2. However, although Nedd4-2 is known to regulate Kv7.1 by ubiquitylation, biochemical analyses demonstrated that PKA did not influence the amount of Nedd4-2 bound to Kv7.1 or the ubiquitylation level of the channel. This suggests that PKA influences Nedd4-2-dependent Kv7.1 transport though a different molecular mechanism. In summary, we identify a novel mechanism whereby PKA can increase Kv7.1 current levels, namely by regulating Nedd4-2-dependent Kv7.1 transport.
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Affiliation(s)
- Martin N Andersen
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Louise L Hefting
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Annette B Steffensen
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Nicole Schmitt
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Søren-Peter Olesen
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Jesper V Olsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alicia Lundby
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hanne B Rasmussen
- The Danish National Research Foundation Center for Cardiac Arrhythmia and The Faculty of Health and Medical Sciences, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark; and
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5
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Yuan L, Koivumäki JT, Liang B, Lorentzen LG, Tang C, Andersen MN, Svendsen JH, Tfelt-Hansen J, Maleckar M, Schmitt N, Olesen MS, Jespersen T. Investigations of the Navβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant. Am J Physiol Heart Circ Physiol 2014; 306:H1204-12. [PMID: 24561865 DOI: 10.1152/ajpheart.00405.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [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: 11/22/2022]
Abstract
Brugada syndrome (BrS) is a rare inherited disease that can give rise to ventricular arrhythmia and ultimately sudden cardiac death. Numerous loss-of-function mutations in the cardiac sodium channel Nav1.5 have been associated with BrS. However, few mutations in the auxiliary Navβ1-4 subunits have been linked to this disease. Here we investigated differences in expression and function between Navβ1 and Navβ1b and whether the H162P/Navβ1b mutation found in a BrS patient is likely to be the underlying cause of disease. The impact of Navβ subunits was investigated by patch-clamp electrophysiology, and the obtained in vitro values were used for subsequent in silico modeling. We found that Navβ1b transcripts were expressed at higher levels than Navβ1 transcripts in the human heart. Navβ1 and Navβ1b coexpressed with Nav1.5 induced a negative shift on steady state of activation and inactivation compared with Nav1.5 alone. Furthermore, Navβ1b was found to increase the current level when coexpressed with Nav1.5, Navβ1b/H162P mutated subunit peak current density was reduced by 48% (-645 ± 151 vs. -334 ± 71 pA/pF), V1/2 steady-state inactivation shifted by -6.7 mV (-70.3 ± 1.5 vs. -77.0 ± 2.8 mV), and time-dependent recovery from inactivation slowed by >50% compared with coexpression with Navβ1b wild type. Computer simulations revealed that these electrophysiological changes resulted in a reduction in both action potential amplitude and maximum upstroke velocity. The experimental data thereby indicate that Navβ1b/H162P results in reduced sodium channel activity functionally affecting the ventricular action potential. This result is an important replication to support the notion that BrS can be linked to the function of Navβ1b and is associated with loss-of-function of the cardiac sodium channel.
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Affiliation(s)
- Lei Yuan
- Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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6
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Liang B, Soka M, Christensen AH, Olesen MS, Larsen AP, Knop FK, Wang F, Nielsen JB, Andersen MN, Humphreys D, Mann SA, Huttner IG, Vandenberg JI, Svendsen JH, Haunsø S, Preiss T, Seebohm G, Olesen SP, Schmitt N, Fatkin D. Genetic variation in the two-pore domain potassium channel, TASK-1, may contribute to an atrial substrate for arrhythmogenesis. J Mol Cell Cardiol 2013; 67:69-76. [PMID: 24374141 DOI: 10.1016/j.yjmcc.2013.12.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 12/09/2013] [Accepted: 12/17/2013] [Indexed: 12/22/2022]
Abstract
The two-pore domain potassium channel, K2P3.1 (TASK-1) modulates background conductance in isolated human atrial cardiomyocytes and has been proposed as a potential drug target for atrial fibrillation (AF). TASK-1 knockout mice have a predominantly ventricular phenotype however, and effects of TASK-1 inactivation on atrial structure and function have yet to be demonstrated in vivo. The extent to which genetic variation in KCNK3, that encodes TASK-1, might be a determinant of susceptibility to AF is also unknown. To address these questions, we first evaluated the effects of transient knockdown of the zebrafish kcnk3a and kcnk3b genes and cardiac phenotypes were evaluated using videomicroscopy. Combined kcnk3a and kcnk3b knockdown in 72 hour post fertilization embryos resulted in lower heart rate (p<0.001), marked increase in atrial diameter (p<0.001), and mild increase in end-diastolic ventricular diameter (p=0.01) when compared with control-injected embryos. We next performed genetic screening of KCNK3 in two independent AF cohorts (373 subjects) and identified three novel KCNK3 variants. Two of these variants, present in one proband with familial AF, were located at adjacent nucleotides in the Kozak sequence and reduced expression of an engineered reporter. A third missense variant, V123L, in a patient with lone AF, reduced resting membrane potential and altered pH sensitivity in patch-clamp experiments, with structural modeling predicting instability in the vicinity of the TASK-1 pore. These in vitro data suggest that the double Kozak variants and V123L will have loss-of-function effects on ITASK. Cardiac action potential modeling predicted that reduced ITASK prolongs atrial action potential duration, and that this is potentiated by reciprocal changes in activity of other ion channel currents. Our findings demonstrate the functional importance of ITASK in the atrium and suggest that inactivation of TASK-1 may have diverse effects on atrial size and electrophysiological properties that can contribute to an arrhythmogenic substrate.
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Affiliation(s)
- Bo Liang
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Magdalena Soka
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Alex Horby Christensen
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Morten S Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Anders P Larsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark; Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Filip K Knop
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Fan Wang
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Jonas B Nielsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Martin N Andersen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - David Humphreys
- Molecular Genetics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Stefan A Mann
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Inken G Huttner
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Jesper H Svendsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Stig Haunsø
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Preiss
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Germany
| | - Søren-Peter Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark.
| | - Diane Fatkin
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia; Cardiology Department, St Vincent's Hospital, Darlinghurst, New South Wales, Australia
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7
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Liang B, Nissen JD, Laursen M, Wang X, Skibsbye L, Hearing MC, Andersen MN, Rasmussen HB, Wickman K, Grunnet M, Olesen SP, Jespersen T. G-protein-coupled inward rectifier potassium current contributes to ventricular repolarization. Cardiovasc Res 2013; 101:175-84. [PMID: 24148898 DOI: 10.1093/cvr/cvt240] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [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: 11/13/2022] Open
Abstract
AIMS The purpose of this study was to investigate the functional role of G-protein-coupled inward rectifier potassium (GIRK) channels in the cardiac ventricle. METHODS AND RESULTS Immunofluorescence experiments demonstrated that GIRK4 was localized in outer sarcolemmas and t-tubules in GIRK1 knockout (KO) mice, whereas GIRK4 labelling was not detected in GIRK4 KO mice. GIRK4 was localized in intercalated discs in rat ventricle, whereas it was expressed in intercalated discs and outer sarcolemmas in rat atrium. GIRK4 was localized in t-tubules and intercalated discs in human ventricular endocardium and epicardium, but absent in mid-myocardium. Electrophysiological recordings in rat ventricular tissue ex vivo showed that the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and acetylcholine (ACh) shortened action potential duration (APD), and that the APD shortening was reversed by either the GIRK channel blocker tertiapin-Q, the adenosine A1 receptor antagonist DPCPX or by the muscarinic M2 receptor antagonist AF-DX 116. Tertiapin-Q prolonged APD in the absence of the exogenous receptor activation. Furthermore, CPA and ACh decreased the effective refractory period and the effect was reversed by either tertiapin-Q, DPCPX or AF-DX 116. Receptor activation also hyperpolarized the resting membrane potential, an effect that was reversed by tertiapin-Q. In contrast, tertiapin-Q depolarized the resting membrane potential in the absence of the exogenous receptor activation. CONCLUSION Confocal microscopy shows that among species GIRK4 is differentially localized in the cardiac ventricle, and that it is heterogeneously expressed across human ventricular wall. Electrophysiological recordings reveal that GIRK current may contribute significantly to ventricular repolarization and thereby to cardiac electrical stability.
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Affiliation(s)
- Bo Liang
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 16.5.35, Copenhagen DK-2200N, Denmark
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8
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Lundby A, Andersen MN, Steffensen AB, Horn H, Kelstrup CD, Francavilla C, Jensen LJ, Schmitt N, Thomsen MB, Olsen JV. In vivo phosphoproteomics analysis reveals the cardiac targets of β-adrenergic receptor signaling. Sci Signal 2013; 6:rs11. [PMID: 23737553 DOI: 10.1126/scisignal.2003506] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
β-Blockers are widely used to prevent cardiac arrhythmias and to treat hypertension by inhibiting β-adrenergic receptors (βARs) and thus decreasing contractility and heart rate. βARs initiate phosphorylation-dependent signaling cascades, but only a small number of the target proteins are known. We used quantitative in vivo phosphoproteomics to identify 670 site-specific phosphorylation changes in murine hearts in response to acute treatment with specific βAR agonists. The residues adjacent to the regulated phosphorylation sites exhibited a sequence-specific preference (R-X-X-pS/T), and integrative analysis of sequence motifs and interaction networks suggested that the kinases AMPK (adenosine 5'-monophosphate-activated protein kinase), Akt, and mTOR (mammalian target of rapamycin) mediate βAR signaling, in addition to the well-established pathways mediated by PKA (cyclic adenosine monophosphate-dependent protein kinase) and CaMKII (calcium/calmodulin-dependent protein kinase type II). We found specific regulation of phosphorylation sites on six ion channels and transporters that mediate increased ion fluxes at higher heart rates, and we showed that phosphorylation of one of these, Ser(92) of the potassium channel KV7.1, increased current amplitude. Our data set represents a quantitative analysis of phosphorylated proteins regulated in vivo upon stimulation of seven-transmembrane receptors, and our findings reveal previously unknown phosphorylation sites that regulate myocardial contractility, suggesting new potential targets for the treatment of heart disease and hypertension.
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Affiliation(s)
- Alicia Lundby
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, DK-2200 Copenhagen, Denmark.
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9
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David JP, Andersen MN, Olesen SP, Rasmussen HB, Schmitt N. Trafficking of the IKs -complex in MDCK cells: site of subunit assembly and determinants of polarized localization. Traffic 2013; 14:399-411. [PMID: 23324056 DOI: 10.1111/tra.12042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 01/08/2013] [Accepted: 01/16/2013] [Indexed: 11/28/2022]
Abstract
The voltage-gated potassium channel KV 7.1 is regulated by non-pore forming regulatory KCNE β-subunits. Together with KCNE1, it forms the slowly activating delayed rectifier potassium current IKs . However, where the subunits assemble and which of the subunits determines localization of the IKs -complex has not been unequivocally resolved yet. We employed trafficking-deficient KV 7.1 and KCNE1 mutants to investigate IKs trafficking using the polarized Madin-Darby Canine Kidney cell line. We find that the assembly happens early in the secretory pathway but provide three lines of evidence that it takes place in a post-endoplasmic reticulum compartment. We demonstrate that KV 7.1 targets the IKs -complex to the basolateral membrane, but that KCNE1 can redirect the complex to the apical membrane upon mutation of critical KV 7.1 basolateral targeting signals. Our data provide a possible explanation to the fact that KV 7.1 can be localized apically or basolaterally in different epithelial tissues and offer a solution to divergent literature results regarding the effect of KCNE subunits on the subcellular localization of KV 7.1/KCNE complexes.
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Affiliation(s)
- Jens-Peter David
- The Ion Channel Group, Danish National Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2200, Denmark
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10
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Larsen BR, Steffensen SDR, Nielsen NVL, Friis S, Godiksen S, Bornholdt J, Soendergaard C, Nonboe AW, Andersen MN, Poulsen SS, Szabo R, Bugge TH, Lin CY, Skovbjerg H, Jensen JK, Vogel LK. Hepatocyte growth factor activator inhibitor-2 prevents shedding of matriptase. Exp Cell Res 2013; 319:918-29. [PMID: 23333561 DOI: 10.1016/j.yexcr.2013.01.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 01/02/2013] [Accepted: 01/07/2013] [Indexed: 12/31/2022]
Abstract
Hepatocyte growth factor activator inhibitor-2 (HAI-2) is an inhibitor of many proteases in vitro, including the membrane-bound serine protease, matriptase. Studies of knock-out mice have shown that HAI-2 is essential for placental development only in mice expressing matriptase, suggesting that HAI-2 is important for regulation of matriptase. Previous studies have shown that recombinant expression of matriptase was unsuccessful unless co-expressed with another HAI, HAI-1. In the present study we show that when human matriptase is recombinantly expressed alone in the canine cell line MDCK, then human matriptase mRNA can be detected and the human matriptase ectodomain is shed to the media, suggesting that matriptase expressed alone is rapidly transported through the secretory pathway and shed. Whereas matriptase expressed together with HAI-1 or HAI-2 accumulates on the plasma membrane where it is activated, as judged by cleavage at Arg614 and increased peptidolytic activity of the cell extracts. Mutagenesis of Kunitz domain 1 but not Kunitz domain 2 abolished this function of HAI-2. HAI-2 seems to carry out its function intracellularly as this is where the vast majority of HAI-2 is located and since HAI-2 could not be detected on the basolateral plasma membrane where matriptase resides. However, minor amounts of HAI-2 not undergoing endocytosis could be detected on the apical plasma membrane. Our results suggest that Kunitz domain 1 of HAI-2 cause matriptase to accumulate in a membrane-bound form on the basolateral plasma membrane.
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Affiliation(s)
- Brian R Larsen
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
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Christophersen IE, Olesen MS, Liang B, Andersen MN, Larsen AP, Nielsen JB, Haunsø S, Olesen SP, Tveit A, Svendsen JH, Schmitt N. Genetic variation in KCNA5: impact on the atrial-specific potassium current IKur in patients with lone atrial fibrillation. Eur Heart J 2012; 34:1517-25. [DOI: 10.1093/eurheartj/ehs442] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Abstract
Ion transport processes are highly energy consuming. It is therefore critical to couple ion transport processes to the metabolic state of the cell. An important player in this coupling appears to be the AMP-activated protein kinase (AMPK). This kinase becomes activated during conditions of cellular metabolic stress and is well-known for its role in promoting ATP-generating catabolic pathways while turning off ATP-utilizing anabolic pathways. Over the past decade AMPK has also emerged as a key regulator of ion channel activity as an increasing number of ion channels are reported to be either directly or indirectly regulated by the kinase. AMPK therefore provides a necessary link between cellular energy levels and ion channel activity.
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Affiliation(s)
- Martin N Andersen
- The Danish National Research Foundation Centre for Cardiac Arrhythmia; Department of Biomedical Sciences; The Faculty of Health Sciences; University of Copenhagen; Copenhagen, Denmark
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Andersen MN, Krzystanek K, Jespersen T, Olesen SP, Rasmussen HB. AMP-Activated Protein Kinase Downregulates Kv7.1 Cell Surface Expression. Traffic 2011; 13:143-56. [DOI: 10.1111/j.1600-0854.2011.01295.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Abstract
The potassium channel KV7.1 is expressed in the heart where it contributes to the repolarization of the cardiac action potential. In addition, KV7.1 is expressed in epithelial tissues where it plays a role in salt and water transport. Mutations in the kcnq1 gene can lead to long QT syndrome and deafness, and several mutations have been described as trafficking mutations. To learn more about the basic mechanisms that regulate KV7.1 surface expression, we have investigated the trafficking of KV7.1 during the polarization process of the epithelial cell line Madin-Darby Canine Kidney (MDCK) using a modified version of the classical calcium switch. We discovered that KV7.1 exhibits a very dynamic localization pattern during the calcium switch. When MDCK cells are kept in low calcium medium, KV7.1 is mainly observed at the plasma membrane. During the first hours of the switch, KV7.1 is removed from the plasma membrane and an intracellular accumulation in the endoplasmic reticulum (ER) is observed. The channel is retained in the ER until the establishment of the lateral membranes at which point KV7.1 is released from the ER and moves to the plasma membrane. Our data furthermore suggest that while the removal of KV7.1 from the cell surface and its accumulation in the ER could involve activation of protein kinase C, the subsequent release of KV7.1 from the ER depends on phosphoinositide 3-kinase (PI3K) activation. In conclusion, our results demonstrate that KV7.1 surface expression is regulated by signaling mechanisms involved in epithelial cell polarization in particular signaling cascades involving protein kinase C and PI3K.
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Affiliation(s)
- Martin N. Andersen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Søren-Peter Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hanne B. Rasmussen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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15
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Abstract
To find the factors that significantly affected prognosis in patients with peripheral arterial thromboembolism, we reviewed a 12-year experience at two hospitals. Sixty-one patients had 67 embolectomies. Operative treatment and management preserved the limbs in 75.8%. Mortality was 22.4%. Outcome was favorably affected when age was less than 60 years and when arteriosclerotic heart disease was absent, and was adversely affected when common femoral emboli were present and hematocrit level elevated. Duration of symptoms did not affect outcome. Our treatment of patients with peripheral embolism is based on the effect of certain intrinsic factors on the formation of distal thrombus. These factors may be more important than duration of symptoms. Immediate, complete heparinization is recommended to arrest thrombosis, and to allow both for proper emphasis on treatment on the often-associated cardiopathy and for attention to hydration and acid-base balance. This preoperative plan of therapy should produce maximal limb salvage with reduced operative mortality.
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Tourbaf KD, Bettigole RE, Zizzi JA, Subramanian S, Andersen MN. Coronary bypass in a patient with hemophilia B, or Christmas disease. Case report. J Thorac Cardiovasc Surg 1979; 77:562-9. [PMID: 311396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A 40-year-old patient with moderate factor IX deficiency (Christmas disease) underwent quadruple saphenous vein coronary bypass grafts for angina and severe coronary atherosclerosis involving the left and right main, left anterior descending, and circumflex coronary arteries. Excessive bleeding was prevented by infusion of factor IX concentrates during and after the operation. The surgical procedure and total body perfusion were carried out in the same manner as in patients without a hemorrhagic disorder. The patient was discharged after 13 days of hospitalization. He is doing well at the time of this publication and has returned to work.
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Abstract
In this report we describe a patient with bilateral atrial myxomas, which were diagnosed preoperatively by echocardiography and angiography, and successfully removed. The excised tumor mass consisted of mobile right and left atrial myxomas connected by a common stalk which passed through the atrial septum, collectively resembling the shape of a dumbbell. Preoperative echocardiographic and angiographic observations were instrumental in planning the surgical approach, and correlated well with intraoperative findings and with the anatomic configuration of the intact pathologic specimen. Diagnostic aspects of echocardiography are emphasized as they relate to both isolated and bilaterally-occurring atrial myxomas.
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Falsetti HL, Andersen MN. Aneurysm of the membranous ventricular septum producing right ventricular outflow tract obstruction and left ventricular failure. Chest 1971; 59:578-80. [PMID: 4952563 DOI: 10.1378/chest.59.5.578] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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Williams BT, Jacobs RR, Andersen MN, Schenk WG. The effect of acute mitral insufficiency on hemodynamics of the left heart. Surg Gynecol Obstet 1970; 131:1148-52. [PMID: 4920855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Andersen MN. Ventilatory support. Surgery 1969; 66:1112-9. [PMID: 5272955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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24
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Andersen MN, Kuchiba K. Blood trauma produced by pump oxygenators: a comparative study of five different units. J Thorac Cardiovasc Surg 1969; 57:238-44. [PMID: 5764130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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25
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Lauria JI, Andersen MN. Automatically inflated cuffed tube for ventilatory support. Rev Surg 1969; 26:75-6. [PMID: 5789432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Andersen MN, Mouritzen CV, Gabrielli ER. Mechanisms of plasma hemoglobin clearance after acute hemolysis in dogs: serum haptoglobin levels and selective deposition in liver and kidney. Ann Surg 1966; 164:905-12. [PMID: 5923119 PMCID: PMC1477105 DOI: 10.1097/00000658-196611000-00019] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Mouritzen CV, Andersen MN. Mechanisms of ventricular fibrillation during hypothermia. Relative changes in myocardial refractory period and conduction velocity. J Thorac Cardiovasc Surg 1966; 51:585-9. [PMID: 5931958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Andersen MN, Mouritzen CV, Gabrieli E. Mechanisms of plasma hemoglobin clearance after acute hemolysis: studies in open-heart surgical patients. Ann Surg 1966; 163:529-36. [PMID: 5934631 PMCID: PMC1477139 DOI: 10.1097/00000658-196604000-00004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Andersen MN, Gabrieli E, Zizzi JA. Chronic hemolysis in patients with ball-valve prostheses. J Thorac Cardiovasc Surg 1965; 50:501-10. [PMID: 5835500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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