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Aziz Q, Tinker A. The Pathophysiology of Cardiac Abnormalities in Cantu Syndrome: Perspective on "The Mechanism of High-Output Cardiac Hypertrophy Arising From Potassium Channel Gain-of-Function in Cantú Syndrome". FUNCTION (OXFORD, ENGLAND) 2020; 1:zqaa005. [PMID: 32864620 PMCID: PMC7446246 DOI: 10.1093/function/zqaa005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 01/06/2023]
Affiliation(s)
- Qadeer Aziz
- William Harvey Heart Centre, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ. UK
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52
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McClenaghan C, Huang Y, Matkovich SJ, Kovacs A, Weinheimer CJ, Perez R, Broekelmann TJ, Harter TM, Lee JM, Remedi MS, Nichols CG. The Mechanism of High-Output Cardiac Hypertrophy Arising From Potassium Channel Gain-of-Function in Cantú Syndrome. FUNCTION (OXFORD, ENGLAND) 2020; 1:zqaa004. [PMID: 32865539 PMCID: PMC7446247 DOI: 10.1093/function/zqaa004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 01/06/2023]
Abstract
Dramatic cardiomegaly arising from gain-of-function (GoF) mutations in the ATP-sensitive potassium (KATP) channels genes, ABCC9 and KCNJ8, is a characteristic feature of Cantú syndrome (CS). How potassium channel over-activity results in cardiac hypertrophy, as well as the long-term consequences of cardiovascular remodeling in CS, is unknown. Using genome-edited mouse models of CS, we therefore sought to dissect the pathophysiological mechanisms linking KATP channel GoF to cardiac remodeling. We demonstrate that chronic reduction of systemic vascular resistance in CS is accompanied by elevated renin-angiotensin signaling, which drives cardiac enlargement and blood volume expansion. Cardiac enlargement in CS results in elevation of basal cardiac output, which is preserved in aging. However, the cardiac remodeling includes altered gene expression patterns that are associated with pathological hypertrophy and are accompanied by decreased exercise tolerance, suggestive of reduced cardiac reserve. Our results identify a high-output cardiac hypertrophy phenotype in CS which is etiologically and mechanistically distinct from other myocardial hypertrophies, and which exhibits key features of high-output heart failure (HOHF). We propose that CS is a genetically-defined HOHF disorder and that decreased vascular smooth muscle excitability is a novel mechanism for HOHF pathogenesis.
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Affiliation(s)
- Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yan Huang
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Scot J Matkovich
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Attila Kovacs
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Carla J Weinheimer
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ron Perez
- Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas J Broekelmann
- Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Theresa M Harter
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jin-Moo Lee
- Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA,Corresponding author. E-mail:
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53
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Davis MJ, Kim HJ, Zawieja SD, Castorena-Gonzalez JA, Gui P, Li M, Saunders BT, Zinselmeyer BH, Randolph GJ, Remedi MS, Nichols CG. Kir6.1-dependent K ATP channels in lymphatic smooth muscle and vessel dysfunction in mice with Kir6.1 gain-of-function. J Physiol 2020; 598:3107-3127. [PMID: 32372450 DOI: 10.1113/jp279612] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 05/01/2020] [Indexed: 02/06/2023] Open
Abstract
KEY POINTS Spontaneous contractions are essential for normal lymph transport and these contractions are exquisitely sensitive to the KATP channel activator pinacidil. KATP channel Kir6.1 and SUR2B subunits are expressed in mouse lymphatic smooth muscle (LSM) and form functional KATP channels as verified by electrophysiological techniques. Global deletion of Kir6.1 or SUR2 subunits results in severely impaired lymphatic contractile responses to pinacidil. Smooth muscle-specific expression of Kir6.1 gain-of-function mutant (GoF) subunits results in profound lymphatic contractile dysfunction and LSM hyperpolarization that is partially rescued by the KATP inhibitor glibenclamide. In contrast, lymphatic endothelial-specific expression of Kir6.1 GoF has essentially no effect on lymphatic contractile function. The high sensitivity of LSM to KATP channel GoF offers an explanation for the lymphoedema observed in patients with Cantú syndrome, a disorder caused by gain-of-function mutations in genes encoding Kir6.1 or SUR2, and suggests that glibenclamide may be an appropriate therapeutic agent. ABSTRACT This study aimed to understand the functional expression of KATP channel subunits in distinct lymphatic cell types, and assess the consequences of altered KATP channel activity on lymphatic pump function. KATP channel subunits Kir6.1 and SUR2B were expressed in mouse lymphatic muscle by PCR, but only Kir6.1 was expressed in lymphatic endothelium. Spontaneous contractions of popliteal lymphatics from wild-type (WT) (C57BL/6J) mice, assessed by pressure myography, were very sensitive to inhibition by the SUR2-specific KATP channel activator pinacidil, which hyperpolarized both mouse and human lymphatic smooth muscle (LSM). In vessels from mice with deletion of Kir6.1 (Kir6.1-/- ) or SUR2 (SUR2[STOP]) subunits, contractile parameters were not significantly different from those of WT vessels, suggesting that basal KATP channel activity in LSM is not an essential component of the lymphatic pacemaker, and does not exert a strong influence over contractile strength. However, these vessels were >100-fold less sensitive than WT vessels to pinacidil. Smooth muscle-specific expression of a Kir6.1 gain-of-function (GoF) subunit resulted in severely impaired lymphatic contractions and hyperpolarized LSM. Membrane potential and contractile activity was partially restored by the KATP channel inhibitor glibenclamide. In contrast, lymphatic endothelium-specific expression of Kir6.1 GoF subunits had negligible effects on lymphatic contraction frequency or amplitude. Our results demonstrate a high sensitivity of lymphatic contractility to KATP channel activators through activation of Kir6.1/SUR2-dependent channels in LSM. In addition, they offer an explanation for the lymphoedema observed in patients with Cantú syndrome, a disorder caused by gain-of-function mutations in genes encoding Kir6.1/SUR2.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Hae Jin Kim
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Scott D Zawieja
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Jorge A Castorena-Gonzalez
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Peichun Gui
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Min Li
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Brian T Saunders
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Bernd H Zinselmeyer
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Gwendalyn J Randolph
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Maria S Remedi
- Department of Medicine, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO, 63110, USA
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54
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Grange DK, Roessler HI, McClenaghan C, Duran K, Shields K, Remedi MS, Knoers NVAM, Lee JM, Kirk EP, Scurr I, Smithson SF, Singh GK, van Haelst MM, Nichols CG, van Haaften G. Cantú syndrome: Findings from 74 patients in the International Cantú Syndrome Registry. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 181:658-681. [PMID: 31828977 DOI: 10.1002/ajmg.c.31753] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 10/14/2019] [Accepted: 10/18/2019] [Indexed: 11/11/2022]
Abstract
Cantú syndrome (CS), first described in 1982, is caused by pathogenic variants in ABCC9 and KCNJ8, which encode the regulatory and pore forming subunits of ATP-sensitive potassium (KATP ) channels, respectively. Multiple case reports of affected individuals have described the various clinical features of CS, but systematic studies are lacking. To define the effects of genetic variants on CS phenotypes and clinical outcomes, we have developed a standardized REDCap-based registry for CS. We report phenotypic features and associated genotypes on 74 CS subjects, with confirmed ABCC9 variants in 72 of the individuals. Hypertrichosis and a characteristic facial appearance are present in all individuals. Polyhydramnios during fetal life, hyperflexibility, edema, patent ductus arteriosus (PDA), cardiomegaly, dilated aortic root, vascular tortuosity of cerebral arteries, and migraine headaches are common features, although even with this large group of subjects, there is incomplete penetrance of CS-associated features, without clear correlation to genotype.
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Affiliation(s)
- Dorothy K Grange
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.,Center for the Investigation of Membrane Excitability Diseases (CIMED)
| | - Helen I Roessler
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri
| | - Karen Duran
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Kathleen Shields
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Medicine, Division of Endocrinology, Washington University School of Medicine, St. Louis, Missouri
| | - Nine V A M Knoers
- Department of Genetics, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands.,Department of Genetics, University Medical Center Groningen, Groningen, the Netherlands
| | - Jin-Moo Lee
- Department of Neurology and Radiology, Washington University School of Medicine, St. Louis, Missouri
| | - Edwin P Kirk
- Centre for Clinical Genetics, Sydney Children's Hospital, Randwick, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales, Randwick, New South Wales, Australia
| | - Ingrid Scurr
- Department of Clinical Genetics, University Hospitals, Bristol, UK
| | - Sarah F Smithson
- Department of Clinical Genetics, University Hospitals, Bristol, UK
| | - Gautam K Singh
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.,Center for the Investigation of Membrane Excitability Diseases (CIMED)
| | - Mieke M van Haelst
- Department of Clinical Genetics, VU Medical Center, VU University Amsterdam, Amsterdam, The Netherlands.,Department of Clinical Genetics, Amsterdam Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
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55
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Walsh KB. Screening Technologies for Inward Rectifier Potassium Channels: Discovery of New Blockers and Activators. SLAS DISCOVERY 2020; 25:420-433. [PMID: 32292089 DOI: 10.1177/2472555220905558] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
K+ channels play a critical role in maintaining the normal electrical activity of excitable cells by setting the cell resting membrane potential and by determining the shape and duration of the action potential. In nonexcitable cells, K+ channels establish electrochemical gradients necessary for maintaining salt and volume homeostasis of body fluids. Inward rectifier K+ (Kir) channels typically conduct larger inward currents than outward currents, resulting in an inwardly rectifying current versus voltage relationship. This property of inward rectification results from the voltage-dependent block of the channels by intracellular polyvalent cations and makes these channels uniquely designed for maintaining the resting potential near the K+ equilibrium potential (EK). The Kir family of channels consist of seven subfamilies of channels (Kir1.x through Kir7.x) that include the classic inward rectifier (Kir2.x) channel, the G-protein-gated inward rectifier K+ (GIRK) (Kir3.x), and the adenosine triphosphate (ATP)-sensitive (KATP) (Kir 6.x) channels as well as the renal Kir1.1 (ROMK), Kir4.1, and Kir7.1 channels. These channels not only function to regulate electrical/electrolyte transport activity, but also serve as effector molecules for G-protein-coupled receptors (GPCRs) and as molecular sensors for cell metabolism. Of significance, Kir channels represent promising pharmacological targets for treating a number of clinical conditions, including cardiac arrhythmias, anxiety, chronic pain, and hypertension. This review provides a brief background on the structure, function, and pharmacology of Kir channels and then focuses on describing and evaluating current high-throughput screening (HTS) technologies, such as membrane potential-sensitive fluorescent dye assays, ion flux measurements, and automated patch clamp systems used for Kir channel drug discovery.
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Affiliation(s)
- Kenneth B Walsh
- Department of Pharmacology, Physiology & Neuroscience, School of Medicine, University of South Carolina, Columbia, SC, USA
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56
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Bickers SC, Sayewich JS, Kanelis V. Intrinsically disordered regions regulate the activities of ATP binding cassette transporters. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183202. [PMID: 31972165 DOI: 10.1016/j.bbamem.2020.183202] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 12/11/2022]
Abstract
ATP binding cassette (ABC) proteins are a large family of membrane proteins present in all kingdoms of life. These multi-domain proteins are comprised, at minimum, of two membrane-spanning domains (MSD1, MSD2) and two cytosolic nucleotide binding domains (NBD1, NBD2). ATP binding and hydrolysis at the NBDs enables ABC proteins to actively transport solutes across membranes, regulate activities of other proteins, or function as channels. Like most eukaryotic membrane proteins, ABC proteins contain intrinsically disordered regions (IDRs). These conformationally dynamic regions in ABC proteins possess residual structure, are sites of phosphorylation, and mediate protein-protein interactions. Here, we review the role of IDRs in regulating ABC protein activity.
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Affiliation(s)
- Sarah C Bickers
- Department of Chemistry, University of Toronto, Toronto, ON, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Jonathan S Sayewich
- Department of Chemistry, University of Toronto, Toronto, ON, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Voula Kanelis
- Department of Chemistry, University of Toronto, Toronto, ON, Canada; Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, Canada; Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.
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57
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Zangerl-Plessl EM, Qile M, Bloothooft M, Stary-Weinzinger A, van der Heyden MAG. Disease Associated Mutations in K IR Proteins Linked to Aberrant Inward Rectifier Channel Trafficking. Biomolecules 2019; 9:biom9110650. [PMID: 31731488 PMCID: PMC6920955 DOI: 10.3390/biom9110650] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/28/2022] Open
Abstract
The ubiquitously expressed family of inward rectifier potassium (KIR) channels, encoded by KCNJ genes, is primarily involved in cell excitability and potassium homeostasis. Channel mutations associate with a variety of severe human diseases and syndromes, affecting many organ systems including the central and peripheral neural system, heart, kidney, pancreas, and skeletal muscle. A number of mutations associate with altered ion channel expression at the plasma membrane, which might result from defective channel trafficking. Trafficking involves cellular processes that transport ion channels to and from their place of function. By alignment of all KIR channels, and depicting the trafficking associated mutations, three mutational hotspots were identified. One localized in the transmembrane-domain 1 and immediately adjacent sequences, one was found in the G-loop and Golgi-export domain, and the third one was detected at the immunoglobulin-like domain. Surprisingly, only few mutations were observed in experimentally determined Endoplasmic Reticulum (ER)exit-, export-, or ER-retention motifs. Structural mapping of the trafficking defect causing mutations provided a 3D framework, which indicates that trafficking deficient mutations form clusters. These “mutation clusters” affect trafficking by different mechanisms, including protein stability.
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Affiliation(s)
- Eva-Maria Zangerl-Plessl
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Muge Qile
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Meye Bloothooft
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
- Correspondence: ; Tel.: +31-887558901
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Kurian C, Pinamonti G, Starling Hughes S, Martin J, Lypka M. You "Cantu": Multidisciplinary Collaboration Resulting in Successful Orthognathic Surgery. Cleft Palate Craniofac J 2019; 57:249-254. [PMID: 31401848 DOI: 10.1177/1055665619868043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Cantú syndrome (CS) is a rare autosomal dominant disorder caused by a heterozygous pathogenic variant in the ABCC9 or KCNJ8 gene. The disorder is characterized by congenital generalized hypertrichosis, coarse acromegaloid facial features (broad nasal bridge, epicanthal folds, wide mouth, macroglossia), skeletal abnormalities (calvarial thickening, metaphyseal flares, coxa valga, scoliosis), tortuous vasculature (meningeal arteriovenous malformations), and cardiac abnormalities (patent ductus arteriosus, pericardial effusion). Despite the constellation of craniofacial features, there are currently no documented cases of a patient with CS having orthognathic surgery. The purpose of this report is to highlight the multidisciplinary collaboration, including establishment of a genetic diagnosis, cardiac management, and orthodontic therapy, in performing successful orthognathic surgery in a patient with CS.
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Affiliation(s)
- Christopher Kurian
- University of Missouri, Kansas City School of Medicine, Kansas City, MO, USA
| | | | | | - Julie Martin
- Heart Center, Children's Mercy Hospital, Kansas City, MO, USA
| | - Michael Lypka
- University of Missouri, Kansas City School of Medicine, Kansas City, MO, USA.,Division of Orthodontics, University of Missouri-Kansas City School of Dentistry, Kansas City, MO, USA.,Division of Pediatric Plastic and Craniofacial Surgery, Children's Mercy Hospital, Kansas City, MO, USA
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59
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Ma A, Gurnasinghani S, Kirk EP, McClenaghan C, Singh GK, Grange DK, Pandit C, Zhu Y, Roscioli T, Elakis G, Buckley M, Mehta B, Roberts P, Mervis J, Biggin A, Nichols CG. Glibenclamide treatment in a Cantú syndrome patient with a pathogenic ABCC9 gain-of-function variant: Initial experience. Am J Med Genet A 2019; 179:1585-1590. [PMID: 31175705 PMCID: PMC6899598 DOI: 10.1002/ajmg.a.61200] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/18/2019] [Accepted: 04/19/2019] [Indexed: 12/21/2022]
Abstract
Cantú syndrome (CS), characterized by hypertrichosis, distinctive facial features, and complex cardiovascular abnormalities, is caused by pathogenic variants in ABCC9 and KCNJ8 genes. These genes encode gain-of-function mutations in the regulatory (SUR2) and pore-forming (Kir6.1) subunits of KATP channels, respectively, suggesting that channel-blocking sulfonylureas could be a viable therapy. Here we report a neonate with CS, carrying a heterozygous ABCC9 variant (c.3347G>A, p.Arg1116His), born prematurely at 32 weeks gestation. Initial echocardiogram revealed a large patent ductus arteriosus (PDA), and high pulmonary pressures with enlarged right ventricle. He initially received surfactant and continuous positive airway pressure ventilation and was invasively ventilated for 4 weeks, until PDA ligation. After surgery, he still had ongoing bilevel positive airway pressure (BiPAP) requirement, but was subsequently weaned to nocturnal BiPAP. He was treated for pulmonary hypertension with Sildenafil, but failed to make further clinical improvement. A therapeutic glibenclamide trial was commenced in week 11 (initial dose of 0.05 mg-1 kg-1 day-1 in two divided doses). After 1 week of treatment, he began to tolerate time off BiPAP when awake, and edema improved. Glibenclamide was well tolerated, and the dose was slowly increased to 0.15 mg-1 kg-1 day-1 over the next 12 weeks. Mild transient hypoglycemia was observed, but there was no cardiovascular dysfunction. Confirmation of therapeutic benefit will require studies of more CS patients but, based on this limited experience, consideration should be given to glibenclamide as CS therapy, although problems associated with prematurity, and complications of hypoglycemia, might limit outcome in critically ill neonates with CS.
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Affiliation(s)
- Alan Ma
- Department of Clinical GeneticsChildren's Hospital at Westmead, Sydney Children's Hospital NetworkSydneyNew South WalesAustralia
- Discipline of Genomic MedicineSydney Medical School, University of SydneySydneyNew South WalesAustralia
| | - Sunita Gurnasinghani
- Department of Clinical GeneticsChildren's Hospital at Westmead, Sydney Children's Hospital NetworkSydneyNew South WalesAustralia
| | - Edwin P. Kirk
- Centre for Clinical GeneticsSydney Children's Hospital, Sydney Children's Hospital NetworkSydneyNew South WalesAustralia
- NSW Health Pathology East Genomics LaboratorySydneyNew South WalesAustralia
- School of Women's and Children's Health, University of NSWSydneyNew South WalesAustralia
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of MedicineSt. LouisMissouri
- Department of Cell Biology and PhysiologyWashington University School of MedicineSt. LouisMissouri
| | - Gautam K. Singh
- Department of PediatricsWashington University School of MedicineSt. LouisMissouri
| | - Dorothy K. Grange
- Department of PediatricsWashington University School of MedicineSt. LouisMissouri
| | - Chetan Pandit
- Department of Respiratory and Sleep MedicineThe Children's Hospital at WestmeadSydneyNew South WalesAustralia
| | - Yung Zhu
- NSW Health Pathology East Genomics LaboratorySydneyNew South WalesAustralia
| | - Tony Roscioli
- Centre for Clinical GeneticsSydney Children's Hospital, Sydney Children's Hospital NetworkSydneyNew South WalesAustralia
- NSW Health Pathology East Genomics LaboratorySydneyNew South WalesAustralia
| | - George Elakis
- NSW Health Pathology East Genomics LaboratorySydneyNew South WalesAustralia
| | - Michael Buckley
- NSW Health Pathology East Genomics LaboratorySydneyNew South WalesAustralia
| | - Bhavesh Mehta
- Grace Centre for Newborn Intensive CareThe Children's Hospital at WestmeadSydneyNew South WalesAustralia
| | - Philip Roberts
- Department of CardiologyThe Children's Hospital at WestmeadSydneyNew South WalesAustralia
| | - Jonathan Mervis
- Department of CardiologyThe Children's Hospital at WestmeadSydneyNew South WalesAustralia
| | - Andrew Biggin
- Children's Hospital Westmead Clinical School, University of SydneyNew South WalesAustralia
- Institute of Endocrinology and Diabetes, The Children's Hospital at WestmeadSydneyNew South WalesAustralia
| | - Colin G. Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of MedicineSt. LouisMissouri
- Department of Cell Biology and PhysiologyWashington University School of MedicineSt. LouisMissouri
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60
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Chen X, Garon A, Wieder M, Houtman MJC, Zangerl-Plessl EM, Langer T, van der Heyden MAG, Stary-Weinzinger A. Computational Identification of Novel Kir6 Channel Inhibitors. Front Pharmacol 2019; 10:549. [PMID: 31178728 PMCID: PMC6543810 DOI: 10.3389/fphar.2019.00549] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/01/2019] [Indexed: 12/25/2022] Open
Abstract
KATP channels consist of four Kir6.x pore-forming subunits and four regulatory sulfonylurea receptor (SUR) subunits. These channels couple the metabolic state of the cell to membrane excitability and play a key role in physiological processes such as insulin secretion in the pancreas, protection of cardiac muscle during ischemia and hypoxic vasodilation of arterial smooth muscle cells. Abnormal channel function resulting from inherited gain or loss-of-function mutations in either the Kir6.x and/or SUR subunits are associated with severe diseases such as neonatal diabetes, congenital hyperinsulinism, or Cantú syndrome (CS). CS is an ultra-rare genetic autosomal dominant disorder, caused by dominant gain-of-function mutations in SUR2A or Kir6.1 subunits. No specific pharmacotherapeutic treatment options are currently available for CS. Kir6 specific inhibitors could be beneficial for the development of novel drug therapies for CS, particular for mutations, which lack high affinity for sulfonylurea inhibitor glibenclamide. By applying a combination of computational methods including atomistic MD simulations, free energy calculations and pharmacophore modeling, we identified several novel Kir6.1 inhibitors, which might be possible candidates for drug repurposing. The in silico predictions were confirmed using inside/out patch-clamp analysis. Importantly, Cantú mutation C166S in Kir6.2 (equivalent to C176S in Kir6.1) and S1020P in SUR2A, retained high affinity toward the novel inhibitors. Summarizing, the inhibitors identified in this study might provide a starting point toward developing novel therapies for Cantú disease.
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Affiliation(s)
- Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Arthur Garon
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Marcus Wieder
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Marien J. C. Houtman
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | | | - Thierry Langer
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Marcel A. G. van der Heyden
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
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Houtman MJC, Chen X, Qile M, Duran K, van Haaften G, Stary-Weinzinger A, van der Heyden MAG. Glibenclamide and HMR1098 normalize Cantú syndrome-associated gain-of-function currents. J Cell Mol Med 2019; 23:4962-4969. [PMID: 31119887 PMCID: PMC7346732 DOI: 10.1111/jcmm.14329] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 03/13/2019] [Accepted: 03/25/2019] [Indexed: 12/15/2022] Open
Abstract
Cantú syndrome (CS) is caused by dominant gain-of-function mutation in ATP-dependent potassium channels. Cellular ATP concentrations regulate potassium current thereby coupling energy status with membrane excitability. No specific pharmacotherapeutic options are available to treat CS but IKATP channels are pharmaceutical targets in type II diabetes or cardiac arrhythmia treatment. We have been suggested that IKATP inhibitors, glibenclamide and HMR1098, normalize CS channels. IKATP in response to Mg-ATP, glibenclamide and HMR1098 were measured by inside-out patch-clamp electrophysiology. Results were interpreted in view of cryo-EM IKATP channel structures. Mg-ATP IC50 values of outward current were increased for D207E (0.71 ± 0.14 mmol/L), S1020P (1.83 ± 0.10), S1054Y (0.95 ± 0.06) and R1154Q (0.75 ± 0.13) channels compared to H60Y (0.14 ± 0.01) and wild-type (0.15 ± 0.01). HMR1098 dose-dependently inhibited S1020P and S1054Y channels in the presence of 0.15 mmol/L Mg-ATP, reaching, at 30 μmol/L, current levels displayed by wild-type and H60Y channels in the presence of 0.15 mmol/L Mg-ATP. Glibenclamide (10 μmol/L) induced similar normalization. S1054Y sensitivity to glibenclamide increases strongly at 0.5 mmol/L Mg-ATP compared to 0.15 mmol/L, in contrast to D207E and S1020P channels. Experimental findings agree with structural considerations. We conclude that CS channel activity can be normalized by existing drugs; however, complete normalization can be achieved at supraclinical concentrations only.
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Affiliation(s)
- Marien J C Houtman
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Muge Qile
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Karen Duran
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Gijs van Haaften
- Center for Molecular Medicine, Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Marcel A G van der Heyden
- Division of Heart and Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands
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62
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Resistin Mediates Sex-Dependent Effects of Perivascular Adipose Tissue on Vascular Function in the Shrsp. Sci Rep 2019; 9:6897. [PMID: 31053755 PMCID: PMC6499830 DOI: 10.1038/s41598-019-43326-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 04/23/2019] [Indexed: 12/30/2022] Open
Abstract
Premenopausal women are relatively protected from developing hypertension compared to men. Perivascular adipose tissue (PVAT) has been shown to mediate vasoactive effects; however, a sex-dependent difference in PVAT function in the setting of hypertension has not yet been explored. We investigated the effect of PVAT on resistance vessel biology in male and female 16 week old stroke prone spontaneously hypertensive rats (SHRSP). This preclinical model of hypertension exhibits a sex-dependent difference in the development of hypertension similar to humans. Wire myography was used to assess vascular function in third-order mesenteric arteries. KATP channel-mediated vasorelaxation by cromakalim was significantly impaired in vessels from SHRSP males + PVAT relative to females (maximum relaxation: male + PVAT 46.9 ± 3.9% vs. female + PVAT 97.3 ± 2.7%). A cross-over study assessing the function of male PVAT on female vessels confirmed the reduced vasorelaxation response to cromakalim associated with male PVAT (maximum relaxation: female + PVATfemale90.6 ± 1.4% vs. female + PVATmale65.8 ± 3.5%). In order to explore the sex-dependent differences in PVAT at a molecular level, an adipokine array and subsequent western blot validation identified resistin expression to be increased approximately 2-fold in PVAT from male SHRSP vessels. Further wire myography experiments showed that pre-incubation with resistin (40 ng/ml) significantly impaired the ability of female + PVAT vessels to relax in response to cromakalim (maximum relaxation: female + PVAT 97.3 ± 0.9% vs. female + PVAT + resistin[40ng/ml]36.8 ± 2.3%). These findings indicate a novel role for resistin in mediating sex-dependent vascular function in hypertension through a KATP channel-mediated mechanism.
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63
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Dogan MF, Yildiz O, Arslan SO, Ulusoy KG. Potassium channels in vascular smooth muscle: a pathophysiological and pharmacological perspective. Fundam Clin Pharmacol 2019; 33:504-523. [PMID: 30851197 DOI: 10.1111/fcp.12461] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/23/2022]
Abstract
Potassium (K+ ) ion channel activity is an important determinant of vascular tone by regulating cell membrane potential (MP). Activation of K+ channels leads to membrane hyperpolarization and subsequently vasodilatation, while inhibition of the channels causes membrane depolarization and then vasoconstriction. So far five distinct types of K+ channels have been identified in vascular smooth muscle cells (VSMCs): Ca+2 -activated K+ channels (BKC a ), voltage-dependent K+ channels (KV ), ATP-sensitive K+ channels (KATP ), inward rectifier K+ channels (Kir ), and tandem two-pore K+ channels (K2 P). The activity and expression of vascular K+ channels are changed during major vascular diseases such as hypertension, pulmonary hypertension, hypercholesterolemia, atherosclerosis, and diabetes mellitus. The defective function of K+ channels is commonly associated with impaired vascular responses and is likely to become as a result of changes in K+ channels during vascular diseases. Increased K+ channel function and expression may also help to compensate for increased abnormal vascular tone. There are many pharmacological and genotypic studies which were carried out on the subtypes of K+ channels expressed in variable amounts in different vascular beds. Modulation of K+ channel activity by molecular approaches and selective drug development may be a novel treatment modality for vascular dysfunction in the future. This review presents the basic properties, physiological functions, pathophysiological, and pharmacological roles of the five major classes of K+ channels that have been determined in VSMCs.
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Affiliation(s)
- Muhammed Fatih Dogan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Oguzhan Yildiz
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
| | - Seyfullah Oktay Arslan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Kemal Gokhan Ulusoy
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
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64
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Lambadiari V, Dimitriadis G, Kadoglou NPE. The impact of oral anti-diabetic medications on heart failure: lessons learned from preclinical studies. Heart Fail Rev 2019. [PMID: 29524067 DOI: 10.1007/s10741-018-9690-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The prevalence of heart failure (HF) in the diabetic population has rapidly increased over the past 2 decades, triggering research about the impact of oral anti-diabetic medications on it. Unfortunately, not all success at the bench in preclinical experiments has translated to success at the bedside. On the other hand, recent promising clinical data from oral SGLT2 inhibitors mainly lack mechanistic explanation from experimental studies. Hence, it is critical to understand the lessons learned from prior translational studies to gain a better knowledge of the mechanisms of oral anti-diabetic drugs in HF. This review aims to summarize the results from preclinical studies regarding the interaction between oral anti-diabetic medications and heart failure development and/or exacerbation. Although there is a wide spectrum of controversial results, the underlying hope is that the clinical success rate will improve and the adverse events during ineffective targeted therapy will be limited.
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Affiliation(s)
- Vaia Lambadiari
- 2nd Department of Internal Medicine-Propaedeutic, Research Unit and Diabetes Center, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - George Dimitriadis
- 2nd Department of Internal Medicine-Propaedeutic, Research Unit and Diabetes Center, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Nikolaos P E Kadoglou
- Centre for Statistics in Medicine - Βotnar Research Centre, University of Oxford, Oxford, UK.
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TDP-43 proteinopathy in aging: Associations with risk-associated gene variants and with brain parenchymal thyroid hormone levels. Neurobiol Dis 2019; 125:67-76. [PMID: 30682540 DOI: 10.1016/j.nbd.2019.01.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/13/2019] [Accepted: 01/19/2019] [Indexed: 02/08/2023] Open
Abstract
TDP-43 proteinopathy is very prevalent among the elderly (affecting at least 25% of individuals over 85 years of age) and is associated with substantial cognitive impairment. Risk factors implicated in age-related TDP-43 proteinopathy include commonly inherited gene variants, comorbid Alzheimer's disease pathology, and thyroid hormone dysfunction. To test parameters that are associated with aging-related TDP-43 pathology, we performed exploratory analyses of pathologic, genetic, and biochemical data derived from research volunteers in the University of Kentucky Alzheimer's Disease Center autopsy cohort (n = 136 subjects). Digital pathologic methods were used to discriminate and quantify both neuritic and intracytoplasmic TDP-43 pathology in the hippocampal formation. Overall, 46.4% of the cases were positive for TDP-43 intracellular inclusions, which is consistent with results in other prior community-based cohorts. The pathologies were correlated with hippocampal sclerosis of aging (HS-Aging) linked genotypes. We also assayed brain parenchymal thyroid hormone (triiodothyronine [T3] and thyroxine [T4]) levels. In cases with SLCO1A2/IAPP or ABCC9 risk associated genotypes, the T3/T4 ratio tended to be reduced (p = .051 using 2-tailed statistical test), and in cases with low T3/T4 ratios (bottom quintile), there was a higher likelihood of HS-Aging pathology (p = .025 using 2-tailed statistical test). This is intriguing because the SLCO1A2/IAPP and ABCC9 risk associated genotypes have been associated with altered expression of the astrocytic thyroid hormone receptor (protein product of the nearby gene SLCO1C1). These data indicate that dysregulation of thyroid hormone signaling may play a role in age-related TDP-43 proteinopathy.
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66
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Marques P, Korbonits M. Pseudoacromegaly. Front Neuroendocrinol 2019; 52:113-143. [PMID: 30448536 DOI: 10.1016/j.yfrne.2018.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/30/2018] [Accepted: 11/14/2018] [Indexed: 01/19/2023]
Abstract
Individuals with acromegaloid physical appearance or tall stature may be referred to endocrinologists to exclude growth hormone (GH) excess. While some of these subjects could be healthy individuals with normal variants of growth or physical traits, others will have acromegaly or pituitary gigantism, which are, in general, straightforward diagnoses upon assessment of the GH/IGF-1 axis. However, some patients with physical features resembling acromegaly - usually affecting the face and extremities -, or gigantism - accelerated growth/tall stature - will have no abnormalities in the GH axis. This scenario is termed pseudoacromegaly, and its correct diagnosis can be challenging due to the rarity and variability of these conditions, as well as due to significant overlap in their characteristics. In this review we aim to provide a comprehensive overview of pseudoacromegaly conditions, highlighting their similarities and differences with acromegaly and pituitary gigantism, to aid physicians with the diagnosis of patients with pseudoacromegaly.
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Affiliation(s)
- Pedro Marques
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - Márta Korbonits
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.
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Herrera A, Vajravelu ME, Givler S, Mitteer L, Avitabile CM, Lord K, De León DD. Prevalence of Adverse Events in Children With Congenital Hyperinsulinism Treated With Diazoxide. J Clin Endocrinol Metab 2018; 103:4365-4372. [PMID: 30247666 PMCID: PMC6207144 DOI: 10.1210/jc.2018-01613] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/04/2018] [Indexed: 12/30/2022]
Abstract
CONTEXT Diazoxide, the only U.S. Food and Drug Administration-approved drug to treat hyperinsulinemic hypoglycemia, has been associated with several adverse events, which has raised concerns about the safety of this drug. Existing reports are limited to small studies and case reports. OBJECTIVE To determine prevalence of and clinical factors associated with adverse events in infants and children treated with diazoxide. DESIGN Retrospective cohort study of children with hyperinsulinism (HI) treated with diazoxide between 2003 and 2014. SETTING The Congenital Hyperinsulinism Center at the Children's Hospital of Philadelphia. PATIENTS Children and infants with laboratory-confirmed diagnosis of HI. MAIN OUTCOME MEASURES Prevalence of pulmonary hypertension (PH), edema, neutropenia, thrombocytopenia, and hyperuricemia was determined. Tests of association and logistic regression were used to identify potential risk factors. RESULTS A total of 295 patients (129 female) met inclusion criteria. The median age at diazoxide initiation was 29 days (interquartile range, 10 to 142 days; n = 226 available start dates); 2.4% of patients were diagnosed with PH after diazoxide initiation. Children with PH (P = 0.003) or edema (P = 0.002) were born at earlier gestational age and more frequently had potential PH risk factors, including respiratory failure and structural heart disease (P < 0.0001 and P = 0.005). Other adverse events included neutropenia (15.6%), thrombocytopenia (4.7%), and hyperuricemia (5.0%). CONCLUSION In this large cohort, PH occurred in infants with underlying risk factors, but no identifiable risk profile emerged for other adverse events. The relatively high prevalence of neutropenia, thrombocytopenia, and hyperuricemia suggests the value in proactively screening for these side effects in children treated with diazoxide.
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Affiliation(s)
- Adriana Herrera
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Mary Ellen Vajravelu
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Stephanie Givler
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Lauren Mitteer
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Catherine M Avitabile
- Department of Pediatrics, The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
- Division of Cardiology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Katherine Lord
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Diva D De León
- Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, The Children’s Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
- Correspondence and Reprint Requests: Diva D. De León, MD, Division of Endocrinology and Diabetes, The Children’s Hospital of Philadelphia, Suite 11NW30, 3401 Civic Center Boulevard, Philadelphia, Pennsylvania 19104. E-mail:
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68
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Sooklal CR, López-Alonso JP, Papp N, Kanelis V. Phosphorylation Alters the Residual Structure and Interactions of the Regulatory L1 Linker Connecting NBD1 to the Membrane-Bound Domain in SUR2B. Biochemistry 2018; 57:6278-6292. [PMID: 30273482 DOI: 10.1021/acs.biochem.8b00503] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
ATP-sensitive potassium (KATP) channels in vascular smooth muscle are comprised of four pore-forming Kir6.1 subunits and four copies of the sulfonylurea receptor 2B (SUR2B), which acts as a regulator of channel gating. Recent electron cryo-microscopy (cryo-EM) structures of the pancreatic KATP channel show a central Kir6.2 pore that is surrounded by the SUR1 subunits. Mutations in the L1 linker connecting the first membrane-spanning domain and the first nucleotide binding domain (NBD1) in SUR2B cause cardiac disease; however, this part of the protein is not resolved in the cryo-EM structures. Phosphorylation of the L1 linker, by protein kinase A, disrupts its interactions with NBD1, which increases the MgATP affinity of NBD1 and KATP channel gating. To elucidate the mode by which the L1 linker regulates KATP channels, we have probed the effects of phosphorylation on its structure and interactions using nuclear magnetic resonance (NMR) spectroscopy and other techniques. We demonstrate that the L1 linker is an intrinsically disordered region of SUR2B but possesses residual secondary and compact structure, both of which are disrupted with phosphorylation. NMR binding studies demonstrate that phosphorylation alters the mode by which the L1 linker interacts with NBD1. The data show that L1 linker residues with the greatest α-helical propensity also form the most stable interaction with NBD1, highlighting a hot spot within the L1 linker. This hot spot is the site of disease-causing mutations and is associated with other processes that regulate KATP channel gating. These data provide insights into the mode by which the phospho-regulatory L1 linker regulates KATP channels.
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Affiliation(s)
- Clarissa R Sooklal
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Jorge P López-Alonso
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Natalia Papp
- Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Voula Kanelis
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6.,Department of Cell and Systems Biology , University of Toronto , Toronto , ON , Canada M5S 3G5
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69
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Huang Y, McClenaghan C, Harter TM, Hinman K, Halabi CM, Matkovich SJ, Zhang H, Brown GS, Mecham RP, England SK, Kovacs A, Remedi MS, Nichols CG. Cardiovascular consequences of KATP overactivity in Cantu syndrome. JCI Insight 2018; 3:121153. [PMID: 30089727 DOI: 10.1172/jci.insight.121153] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 06/28/2018] [Indexed: 11/17/2022] Open
Abstract
Cantu syndrome (CS) is characterized by multiple vascular and cardiac abnormalities including vascular dilation and tortuosity, systemic hypotension, and cardiomegaly. The disorder is caused by gain-of-function (GOF) mutations in genes encoding pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) ATP-sensitive potassium (KATP) channel subunits. However, there is little understanding of the link between molecular dysfunction and the complex pathophysiology observed, and there is no known treatment, in large part due to the lack of appropriate preclinical disease models in which to test therapies. Notably, expression of Kir6.1 and SUR2 does not fully overlap, and the relative contribution of KATP GOF in various cardiovascular tissues remains to be elucidated. To investigate pathophysiologic mechanisms in CS we have used CRISPR/Cas9 engineering to introduce CS-associated SUR2[A478V] and Kir6.1[V65M] mutations to the equivalent endogenous loci in mice. Mirroring human CS, both of these animals exhibit low systemic blood pressure and dilated, compliant blood vessels, as well dramatic cardiac enlargement, the effects being more severe in V65M animals than in A478V animals. In both animals, whole-cell patch-clamp recordings reveal enhanced basal KATP conductance in vascular smooth muscle, explaining vasodilation and lower blood pressure, and demonstrating a cardinal role for smooth muscle KATP dysfunction in CS etiology. Echocardiography confirms in situ cardiac enlargement and increased cardiac output in both animals. Patch-clamp recordings reveal reduced ATP sensitivity of ventricular myocyte KATP channels in A478V, but normal ATP sensitivity in V65M, suggesting that cardiac remodeling occurs secondary to KATP overactivity outside of the heart. These SUR2[A478V] and Kir6.1[V65M] animals thus reiterate the key cardiovascular features seen in human CS. They establish the molecular basis of the pathophysiological consequences of reduced smooth muscle excitability resulting from SUR2/Kir6.1-dependent KATP GOF, and provide a validated animal model in which to examine potential therapeutic approaches to treating CS.
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Affiliation(s)
- Yan Huang
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - Theresa M Harter
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | | | | | | | - Haixia Zhang
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - G Schuyler Brown
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | | | - Sarah K England
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Obstetrics and Gynecology, and
| | - Attila Kovacs
- Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
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70
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Watanabe Y, Kishimoto T, Miki T, Seino S, Nakaya H, Matsumoto A. Ectopic overexpression of Kir6.1 in the mouse heart impacts on the life expectancy. Sci Rep 2018; 8:11723. [PMID: 30082733 PMCID: PMC6078942 DOI: 10.1038/s41598-018-30175-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 07/24/2018] [Indexed: 12/28/2022] Open
Abstract
We recently reported the reduced ATP-sensitive potassium (KATP) channel activities in the transgenic mouse heart overexpressing the vascular type KATP channel pore-forming subunit (Kir6.1). Although dysfunction of cardiac KATP channel has been nominated as a cause of cardiomyopathy in human, these transgenic mice looked normal as wild-type (WT) during the experiment period (~20 weeks). Extended observation period revealed unexpected deaths beginning from 30 weeks and about 50% of the transgenic mice died by 55 weeks. Surface ECG recordings from the transgenic mice at rest demonstrated the normal sinus rhythm and the regular ECG complex as well as the control WT mice except for prolonged QT interval. However, the stress ECG test with noradrenaline revealed abnormal intraventricular conduction delay and arrhythmogeneity in the transgenic mouse. Fibrotic changes in the heart tissue were remarkable in aged transgenic mice, and the cardiac fibrosis developed progressively at least from the age of 30 weeks. Gene expression analyses revealed the differentiation of cardiac fibroblasts to myofibroblasts with elevated cytokine expressions was initiated way in advance before the fibrotic changes and the upregulation of BNP in the ventricle. In sum, Kir6.1TG mice provide an electro-pathological disease concept originated from KATP channel dysfunction.
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Affiliation(s)
- Yasuhiro Watanabe
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takashi Kishimoto
- Department of Molecular Pathology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takashi Miki
- Department of Medical Physiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Haruaki Nakaya
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Akio Matsumoto
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan.
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71
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Cheng F, Desai RJ, Handy DE, Wang R, Schneeweiss S, Barabási AL, Loscalzo J. Network-based approach to prediction and population-based validation of in silico drug repurposing. Nat Commun 2018; 9:2691. [PMID: 30002366 PMCID: PMC6043492 DOI: 10.1038/s41467-018-05116-5] [Citation(s) in RCA: 292] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 06/08/2018] [Indexed: 12/21/2022] Open
Abstract
Here we identify hundreds of new drug-disease associations for over 900 FDA-approved drugs by quantifying the network proximity of disease genes and drug targets in the human (protein–protein) interactome. We select four network-predicted associations to test their causal relationship using large healthcare databases with over 220 million patients and state-of-the-art pharmacoepidemiologic analyses. Using propensity score matching, two of four network-based predictions are validated in patient-level data: carbamazepine is associated with an increased risk of coronary artery disease (CAD) [hazard ratio (HR) 1.56, 95% confidence interval (CI) 1.12–2.18], and hydroxychloroquine is associated with a decreased risk of CAD (HR 0.76, 95% CI 0.59–0.97). In vitro experiments show that hydroxychloroquine attenuates pro-inflammatory cytokine-mediated activation in human aortic endothelial cells, supporting mechanistically its potential beneficial effect in CAD. In summary, we demonstrate that a unique integration of protein-protein interaction network proximity and large-scale patient-level longitudinal data complemented by mechanistic in vitro studies can facilitate drug repurposing. Repurposing approved drugs could accelerate treatment options for various diseases. Here, the authors use network proximity of disease gene products and drug targets in the human protein interactome to identify drug-disease associations for cardiovascular disease, and validate these using longitudinal healthcare data.
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Affiliation(s)
- Feixiong Cheng
- Center for Complex Networks Research and Department of Physics, Northeastern University, Boston, MA, 02115, USA.,Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Rishi J Desai
- Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Diane E Handy
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Ruisheng Wang
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Sebastian Schneeweiss
- Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Albert-László Barabási
- Center for Complex Networks Research and Department of Physics, Northeastern University, Boston, MA, 02115, USA.,Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA.,Center for Network Science, Central European University, Budapest, 1051, Hungary
| | - Joseph Loscalzo
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA.
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Alterations of ATP-sensitive K + channels in human umbilical arterial smooth muscle during gestational diabetes mellitus. Pflugers Arch 2018; 470:1325-1333. [PMID: 29855712 DOI: 10.1007/s00424-018-2154-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/11/2018] [Accepted: 05/09/2018] [Indexed: 12/20/2022]
Abstract
We investigated the alterations of ATP-sensitive K+ (KATP) channels in human umbilical arterial smooth muscle cells during gestational diabetes mellitus (GDM). The amplitude of the KATP current induced by application of the KATP channel opener pinacidil (10 μM) was reduced in the GDM group than in the control group. Pinacidil-induced vasorelaxation was also predominant in the normal group compared with the GDM group. Reverse transcription polymerase chain reaction and Western blot analysis suggested that the expression of KATP channel subunits such as Kir6.1, Kir6.2, and SUR2B were decreased in the GDM group relative to the normal group. The application of forskolin and adenosine, which activates protein kinase A (PKA) and thereby KATP channels, elicited KATP current in both the normal and GDM groups. However, the current amplitudes were not different between the normal and GDM groups. In addition, the expression levels of PKA subunits were not altered between the two groups. These results suggest that the reduction of KATP current and KATP channel-induced vasorelaxation are due to the decreased expression of KATP channels, not to the impairment of KATP-related signaling pathways.
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Pecoraro M, Ciccarelli M, Fiordelisi A, Iaccarino G, Pinto A, Popolo A. Diazoxide Improves Mitochondrial Connexin 43 Expression in a Mouse Model of Doxorubicin-Induced Cardiotoxicity. Int J Mol Sci 2018. [PMID: 29518932 PMCID: PMC5877618 DOI: 10.3390/ijms19030757] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Doxorubicin (DOXO) administration induces alterations in Connexin 43 (Cx43) expression and localization, thus, inducing alterations in chemical and electrical signal transmission between cardiomyocytes and in intracellular calcium homeostasis even evident after a single administration. This study was designed to evaluate if Diazoxide (DZX), a specific opener of mitochondrial KATP channels widely used for its cardioprotective effects, can fight DOXO-induced cardiotoxicity in a short-time mouse model. DZX (20 mg/kg i.p.) was administered 30 min before DOXO (10 mg/kg i.p.) in C57BL/6j female mice for 1–3 or seven days once every other day. A recovery of cardiac parameters, evaluated by Echocardiography, were observed in DZX+DOXO co-treated mice. Western blot analysis performed on heart lysates showed an increase in sarco/endoplasmic reticulum Ca2+-ATPase (SERCAII) and a reduction in phospholamban (PLB) amounts in DZX+DOXO co-treated mice. A contemporary recovery of intracellular Ca2+-signal, detected spectrofluorometrically by means of FURA-2AM, was observed in these mice. Cx43 expression and localization, analyzed by Western blot and confirmed by immunofluorescence analysis, showed that DZX co-treatement increases Cx43 amount both on sarcoplasmic membrane and on mitochondria. In conclusion, our data demonstrate that, in a short-time mouse model of DOXO-induced cardiotoxicity, DZX exerts its cardioprotective effects also by enhancing the amount Cx43.
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Affiliation(s)
- Michela Pecoraro
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy.
| | - Michele Ciccarelli
- Department of Medicine and Surgery, University of Salerno, 84084 Baronissi, Italy.
| | - Antonella Fiordelisi
- Department of Advanced Biomedical Sciences, Federico II University, 80138 Naples, Italy.
| | - Guido Iaccarino
- Department of Medicine and Surgery, University of Salerno, 84084 Baronissi, Italy.
| | - Aldo Pinto
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy.
| | - Ada Popolo
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy.
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Gururaja Rao S, Ponnalagu D, Patel NJ, Singh H. Three Decades of Chloride Intracellular Channel Proteins: From Organelle to Organ Physiology. CURRENT PROTOCOLS IN PHARMACOLOGY 2018; 80:11.21.1-11.21.17. [PMID: 30040212 PMCID: PMC6060641 DOI: 10.1002/cpph.36] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Intracellular organelles are membranous structures central for maintaining cellular physiology and the overall health of the cell. To maintain cellular function, intracellular organelles are required to tightly regulate their ionic homeostasis. Any imbalance in ionic concentrations can disrupt energy production (mitochondria), protein degradation (lysosomes), DNA replication (nucleus), or cellular signaling (endoplasmic reticulum). Ionic homeostasis is also important for volume regulation of intracellular organelles and is maintained by cation and anion channels as well as transporters. One of the major classes of ion channels predominantly localized to intracellular membranes is chloride intracellular channel proteins (CLICs). They are non-canonical ion channels with six homologs in mammals, existing as either soluble or integral membrane protein forms, with dual functions as enzymes and channels. Provided in this overview is a brief introduction to CLICs, and a summary of recent information on their localization, biophysical properties, and physiological roles. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
- Shubha Gururaja Rao
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Neel J Patel
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania
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Gheibi S, Jeddi S, Kashfi K, Ghasemi A. Regulation of vascular tone homeostasis by NO and H 2S: Implications in hypertension. Biochem Pharmacol 2018; 149:42-59. [PMID: 29330066 PMCID: PMC5866223 DOI: 10.1016/j.bcp.2018.01.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/05/2018] [Indexed: 02/09/2023]
Abstract
Nitric oxide (NO) and hydrogen sulfide (H2S) are two gasotransmitters that are produced in the vasculature and contribute to the regulation of vascular tone. NO and H2S are synthesized in both vascular smooth muscle and endothelial cells; NO functions primarily through the sGC/cGMP pathway, and H2S mainly through activation of the ATP-dependent potassium channels; both leading to relaxation of vascular smooth muscle cells. A deficit in the NO/H2S homeostasis is involved in the pathogenesis of various cardiovascular diseases, especially hypertension. It is now becoming increasingly clear that there are important interactions between NO and H2S and that have a profound impact on vascular tone and this may provide insights into the new therapeutic interventions. The aim of this review is to provide a better understanding of individual and interactive roles of NO and H2S in vascular biology. Overall, available data indicate that both NO and H2S contribute to vascular (patho)physiology and in regulating blood pressure. In addition, boosting NO and H2S using various dietary sources or donors could be a hopeful therapeutic strategy in the management of hypertension.
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Affiliation(s)
- Sevda Gheibi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Neurophysiology Research Center and Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Jeddi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Khosrow Kashfi
- Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, NY, USA
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Marques P, Spencer R, Morrison PJ, Carr IM, Dang MN, Bonthron DT, Hunter S, Korbonits M. Cantú syndrome with coexisting familial pituitary adenoma. Endocrine 2018; 59:677-684. [PMID: 29327300 PMCID: PMC5847123 DOI: 10.1007/s12020-017-1497-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 12/11/2017] [Indexed: 12/26/2022]
Abstract
CONTEXT Pseudoacromegaly describes conditions with an acromegaly related physical appearance without abnormalities in the growth hormone (GH) axis. Acromegaloid facies, together with hypertrichosis, are typical manifestations of Cantú syndrome. CASE DESCRIPTION We present a three-generation family with 5 affected members, with marked acromegaloid facies and prominent hypertrichosis, due to a novel missense variant in the ABCC9 gene. The proband, a 2-year-old girl, was referred due to marked hypertrichosis, noticed soon after birth, associated with coarsening of her facial appearance. Her endocrine assessment, including of the GH axis, was normal. The proband's father, paternal aunt, and half-sibling were referred to the Endocrine department for exclusion of acromegaly. Although the GH axis was normal in all, two subjects had clinically non-functioning pituitary macroadenomas, a feature which has not previously been associated with Cantú syndrome. CONCLUSIONS Activating mutations in the ABCC9 and, less commonly, KCNJ8 genes-representing the two subunits of the ATP-sensitive potassium channel-have been linked with Cantú syndrome. Interestingly, minoxidil, a well-known ATP-sensitive potassium channel agonist, can cause a similar phenotype. There is no clear explanation why activating this channel would lead to acromegaloid features or hypertrichosis. This report raises awareness for this complex condition, especially for adult or pediatric endocrinologists who might see these patients referred for evaluation of acromegaloid features or hirsutism. The link between Cantú syndrome and pituitary adenomas is currently unclear.
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Affiliation(s)
- Pedro Marques
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Rupert Spencer
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | | | - Ian M Carr
- School of Medicine, St James's University Hospital, University of Leeds, Leeds, UK
| | - Mary N Dang
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - David T Bonthron
- School of Medicine, St James's University Hospital, University of Leeds, Leeds, UK
| | - Steven Hunter
- Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Belfast, UK
| | - Márta Korbonits
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
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Abstract
Although the mechanism of sudden cardiac death (SCD) in heart failure is not completely known, genetic variations are known to play key roles in this process. Increasing numbers of mutations and variants are being discovered through genome-wide association studies. The genetic variations involved in the mechanisms of SCD have aroused widespread concern. Comprehensive understanding of the genetic variations involved in SCD may help prevent it. To this end, we briefly reviewed the genetic variations involved in SCD and their associations and interactions, and observed that cardiac ion channels are the core molecules involved in this process. Genetic variations involved in cardiac structure, cardiogenesis and development, cell division and differentiation, and DNA replication and transcription are all speculated to be loci involved in SCD. Additionally, the systems involved in neurohumoral regulation as well as substance and energy metabolism are also potentially responsible for susceptibility to SCD. They form an elaborate network and mutually interact with each other to govern the fate of SCD-susceptible individuals.
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Agasid MT, Wang X, Huang Y, Janczak CM, Bränström R, Saavedra SS, Aspinwall CA. Expression, purification, and electrophysiological characterization of a recombinant, fluorescent Kir6.2 in mammalian cells. Protein Expr Purif 2018; 146:61-68. [PMID: 29409958 DOI: 10.1016/j.pep.2018.01.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 11/27/2022]
Abstract
The inwardly rectifying K+ (Kir) channel, Kir6.2, plays critical roles in physiological processes in the brain, heart, and pancreas. Although Kir6.2 has been extensively studied in numerous expression systems, a comprehensive description of an expression and purification protocol has not been reported. We expressed and characterized a recombinant Kir6.2, with an N-terminal decahistidine tag, enhanced green fluorescent protein (eGFP) and deletion of C-terminal 26 amino acids, in succession, denoted eGFP-Kir6.2Δ26. eGFP-Kir6.2Δ26 was expressed in HEK293 cells and a purification protocol developed. Electrophysiological characterization showed that eGFP-Kir6.2Δ26 retains native single channel conductance (64 ± 3.3 pS), mean open times (τ1 = 0.72 ms, τ2 = 15.3 ms) and ATP affinity (IC50 = 115 ± 25 μM) when expressed in HEK293 cells. Detergent screening using size exclusion chromatography (SEC) identified Fos-choline-14 (FC-14) as the most suitable surfactant for protein solubilization, as evidenced by maintenance of the native tetrameric structure in SDS-PAGE and western blot analysis. A two-step scheme using Co2+-metal affinity chromatography and SEC was implemented for purification. Purified protein activity was assessed by reconstituting eGFP-Kir6.2Δ26 in black lipid membranes (BLMs) composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG), l-α-phosphatidylinositol-4,5-bisphosphate (PIP2) in a 89.5:10:0.5 mol ratio. Reconstituted eGFP-Kir6.2Δ26 displayed similar single channel conductance (61.8 ± 0.54 pS) compared to eGFP-Kir6.2Δ26 expressed in HEK293 membranes; however, channel mean open times increased (τ1 = 7.9 ms, τ2 = 61.9 ms) and ATP inhibition was significantly reduced for eGFP-Kir6.2Δ26 reconstituted into BLMs (IC50 = 3.14 ± 0.4 mM). Overall, this protocol should be foundational for the production of purified Kir6.2 for future structural and biochemical studies.
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Affiliation(s)
- Mark T Agasid
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Xuemin Wang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Yiding Huang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Colleen M Janczak
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Robert Bränström
- Department of Molecular Medicine and Surgery, Karolinksa Institutet, Stockholm, Sweden
| | - S Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States; BIO5 Institute, University of Arizona, Tucson, AZ 85721, United States.
| | - Craig A Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States; BIO5 Institute, University of Arizona, Tucson, AZ 85721, United States; Department of Biomedical Engineering, University of Arizona, Tucson, AZ 85721, United States.
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79
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McClenaghan C, Hanson A, Sala-Rabanal M, Roessler HI, Josifova D, Grange DK, van Haaften G, Nichols CG. Cantu syndrome-associated SUR2 (ABCC9) mutations in distinct structural domains result in K ATP channel gain-of-function by differential mechanisms. J Biol Chem 2017; 293:2041-2052. [PMID: 29275331 DOI: 10.1074/jbc.ra117.000351] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/20/2017] [Indexed: 12/25/2022] Open
Abstract
The complex disorder Cantu syndrome (CS) arises from gain-of-function mutations in either KCNJ8 or ABCC9, the genes encoding the Kir6.1 and SUR2 subunits of ATP-sensitive potassium (KATP) channels, respectively. Recent reports indicate that such mutations can increase channel activity by multiple molecular mechanisms. In this study, we determined the mechanism by which KATP function is altered by several substitutions in distinct structural domains of SUR2: D207E in the intracellular L0-linker and Y985S, G989E, M1060I, and R1154Q/R1154W in TMD2. We engineered substitutions at their equivalent positions in rat SUR2A (D207E, Y981S, G985E, M1056I, and R1150Q/R1150W) and investigated functional consequences using macroscopic rubidium (86Rb+) efflux assays and patch-clamp electrophysiology. Our results indicate that D207E increases KATP channel activity by increasing intrinsic stability of the open state, whereas the cluster of Y981S/G985E/M1056I substitutions, as well as R1150Q/R1150W, augmented Mg-nucleotide activation. We also tested the responses of these channel variants to inhibition by the sulfonylurea drug glibenclamide, a potential pharmacotherapy for CS. None of the D207E, Y981S, G985E, or M1056I substitutions had a significant effect on glibenclamide sensitivity. However, Gln and Trp substitution at Arg-1150 significantly decreased glibenclamide potency. In summary, these results provide additional confirmation that mutations in CS-associated SUR2 mutations result in KATP gain-of-function. They help link CS genotypes to phenotypes and shed light on the underlying molecular mechanisms, including consequences for inhibitory drug sensitivity, insights that may inform the development of therapeutic approaches to manage CS.
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Affiliation(s)
| | - Alex Hanson
- From the Departments of Cell Biology and Physiology and
| | | | - Helen I Roessler
- the Department of Medical Genetics, University Medical Center Utrecht, Postbus 85500, 3508 GA Utrecht, The Netherlands, and
| | - Dragana Josifova
- the Guy's and St. Thomas NHS Trust, Clinical Genetics Department, Great Maze Pond, London SE1 9RT, United Kingdom
| | - Dorothy K Grange
- Pediatrics, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
| | - Gijs van Haaften
- the Department of Medical Genetics, University Medical Center Utrecht, Postbus 85500, 3508 GA Utrecht, The Netherlands, and
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Mechanisms involved in the increased sensitivity of the rabbit basilar artery to atrial natriuretic peptide in diabetes. Eur J Pharmacol 2017; 815:64-72. [DOI: 10.1016/j.ejphar.2017.10.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 10/03/2017] [Accepted: 10/05/2017] [Indexed: 12/20/2022]
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81
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Cooper PE, McClenaghan C, Chen X, Stary-Weinzinger A, Nichols CG. Conserved functional consequences of disease-associated mutations in the slide helix of Kir6.1 and Kir6.2 subunits of the ATP-sensitive potassium channel. J Biol Chem 2017; 292:17387-17398. [PMID: 28842488 DOI: 10.1074/jbc.m117.804971] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 08/04/2017] [Indexed: 11/06/2022] Open
Abstract
Cantu syndrome (CS) is a condition characterized by a range of anatomical defects, including cardiomegaly, hyperflexibility of the joints, hypertrichosis, and craniofacial dysmorphology. CS is associated with multiple missense mutations in the genes encoding the regulatory sulfonylurea receptor 2 (SUR2) subunits of the ATP-sensitive K+ (KATP) channel as well as two mutations (V65M and C176S) in the Kir6.1 (KCNJ8) subunit. Previous analysis of leucine and alanine substitutions at the Val-65-equivalent site (Val-64) in Kir6.2 indicated no major effects on channel function. In this study, we characterized the effects of both valine-to-methionine and valine-to-leucine substitutions at this position in both Kir6.1 and Kir6.2 using ion flux and patch clamp techniques. We report that methionine substitution, but not leucine substitution, results in increased open state stability and hence significantly reduced ATP sensitivity and a marked increase of channel activity in the intact cell irrespective of the identity of the coassembled SUR subunit. Sulfonylurea inhibitors, such as glibenclamide, are potential therapies for CS. However, as a consequence of the increased open state stability, both Kir6.1(V65M) and Kir6.2(V64M) mutations essentially abolish high-affinity sensitivity to the KATP blocker glibenclamide in both intact cells and excised patches. This raises the possibility that, at least for some CS mutations, sulfonylurea therapy may not prove to be successful and highlights the need for detailed pharmacogenomic analyses of CS mutations.
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Affiliation(s)
- Paige E Cooper
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Conor McClenaghan
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
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82
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Abbott GW. Chansporter complexes in cell signaling. FEBS Lett 2017; 591:2556-2576. [PMID: 28718502 DOI: 10.1002/1873-3468.12755] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/03/2017] [Accepted: 07/12/2017] [Indexed: 12/11/2022]
Abstract
Ion channels facilitate diffusion of ions across cell membranes for such diverse purposes as neuronal signaling, muscular contraction, and fluid homeostasis. Solute transporters often utilize ionic gradients to move aqueous solutes up their concentration gradient, also fulfilling a wide variety of tasks. Recently, an increasing number of ion channel-transporter ('chansporter') complexes have been discovered. Chansporter complex formation may overcome what could otherwise be considerable spatial barriers to rapid signal integration and feedback between channels and transporters, the ions and other substrates they transport, and environmental factors to which they must respond. Here, current knowledge in this field is summarized, covering both heterologous expression structure/function findings and potential mechanisms by which chansporter complexes fulfill contrasting roles in cell signaling in vivo.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
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83
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Leonard CE, Hennessy S, Han X, Siscovick DS, Flory JH, Deo R. Pro- and Antiarrhythmic Actions of Sulfonylureas: Mechanistic and Clinical Evidence. Trends Endocrinol Metab 2017; 28:561-586. [PMID: 28545784 PMCID: PMC5522643 DOI: 10.1016/j.tem.2017.04.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/18/2017] [Accepted: 04/19/2017] [Indexed: 12/19/2022]
Abstract
Sulfonylureas are the most commonly used second-line drug class for treating type 2 diabetes mellitus (T2DM). While the cardiovascular safety of sulfonylureas has been examined in several trials and nonrandomized studies, little is known of their specific effects on sudden cardiac arrest (SCA) and related serious arrhythmic outcomes. This knowledge gap is striking, because persons with DM are at increased risk of SCA. In this review, we explore the influence of sulfonylureas on the risk of serious arrhythmias, with specific foci on ischemic preconditioning, cardiac excitability, and serious hypoglycemia as putative mechanisms. Elucidating the relationship between individual sulfonylureas and serious arrhythmias is critical, especially as the diabetes epidemic intensifies and SCA incidence increases in persons with diabetes.
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Affiliation(s)
- Charles E Leonard
- Center for Pharmacoepidemiology Research and Training, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Sean Hennessy
- Center for Pharmacoepidemiology Research and Training, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Xu Han
- Center for Pharmacoepidemiology Research and Training, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David S Siscovick
- The New York Academy of Medicine, New York, NY 10029, USA; Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA 98195, USA
| | - James H Flory
- Center for Pharmacoepidemiology Research and Training, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Healthcare Policy and Research, Division of Comparative Effectiveness, Weill Cornell Medicine, Cornell University, New York, NY 10065, USA; Memorial Sloan Kettering Cancer Center, New York, NY 10022, USA
| | - Rajat Deo
- Center for Pharmacoepidemiology Research and Training, Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Division of Cardiovascular Medicine, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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84
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Identifying pathways modulating sleep duration: from genomics to transcriptomics. Sci Rep 2017; 7:4555. [PMID: 28676676 PMCID: PMC5496883 DOI: 10.1038/s41598-017-04027-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 05/10/2017] [Indexed: 01/02/2023] Open
Abstract
Recognizing that insights into the modulation of sleep duration can emerge by exploring the functional relationships among genes, we used this strategy to explore the genome-wide association results for this trait. We detected two major signalling pathways (ion channels and the ERBB signalling family of tyrosine kinases) that could be replicated across independent GWA studies meta-analyses. To investigate the significance of these pathways for sleep modulation, we performed transcriptome analyses of short sleeping flies’ heads (knockdown for the ABCC9 gene homolog; dSur). We found significant alterations in gene-expression in the short sleeping knockdowns versus controls flies, which correspond to pathways associated with sleep duration in our human studies. Most notably, the expression of Rho and EGFR (members of the ERBB signalling pathway) genes was down- and up-regulated, respectively, consistently with the established role of these genes for sleep consolidation in Drosophila. Using a disease multifactorial interaction network, we showed that many of the genes of the pathways indicated to be relevant for sleep duration had functional evidence of their involvement with sleep regulation, circadian rhythms, insulin secretion, gluconeogenesis and lipogenesis.
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85
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Kim HK, Noh YH, Nilius B, Ko KS, Rhee BD, Kim N, Han J. Current and upcoming mitochondrial targets for cancer therapy. Semin Cancer Biol 2017. [PMID: 28627410 DOI: 10.1016/j.semcancer.2017.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mitochondria are essential intracellular organelles that regulate energy metabolism, cell death, and signaling pathways that are important for cell proliferation and differentiation. Therefore, mitochondria are fundamentally implicated in cancer biology, including initiation, growth, metastasis, relapse, and acquired drug resistance. Based on these implications, mitochondria have been proposed as a major therapeutic target for cancer treatment. In addition to classical view of mitochondria in cancer biology, recent studies found novel pathophysiological roles of mitochondria in cancer. In this review, we introduce recent concepts of mitochondrial roles in cancer biology including mitochondrial DNA mutation and epigenetic modulation, energy metabolism reprogramming, mitochondrial channels, involvement in metastasis and drug resistance, and cancer stem cells. We also discuss the role of mitochondria in emerging cancer therapeutic strategies, especially cancer immunotherapy and CRISPR-Cas9 system gene therapy.
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Affiliation(s)
- Hyoung Kyu Kim
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea; Department of Integrated Biomedical Science, College of Medicine, Inje University, Busan, Republic of Korea
| | - Yeon Hee Noh
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Bernd Nilius
- KU Leuven, Department Cell Mol Medicine, Leuven, 3000, Belgium
| | - Kyung Soo Ko
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Byoung Doo Rhee
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Nari Kim
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Jin Han
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea.
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86
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Fatehi M, Carter CC, Youssef N, Light PE. The mechano-sensitivity of cardiac ATP-sensitive potassium channels is mediated by intrinsic MgATPase activity. J Mol Cell Cardiol 2017; 108:34-41. [PMID: 28483598 DOI: 10.1016/j.yjmcc.2017.05.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 10/19/2022]
Abstract
Cardiac ATP-sensitive K+ (KATP) channel activity plays an important cardio-protective role in regulating excitability in response to metabolic stress. Evidence suggests that these channels are also mechano-sensitive and therefore may couple KATP channel activity to increased cardiac workloads. However, the molecular mechanism that couples membrane stretch to channel activity is not currently known. We hypothesized that membrane stretch may alter the intrinsic MgATPase activity of the cardiac KATP channel resulting in increased channel activation. The inside-out patch-clamp technique was used to record single-channel and macroscopic recombinant KATP channel activity in response to membrane stretch elicited by negative pipette pressure. We found that stretch activation requires the presence of the SUR subunit and that inhibition of MgATPase activity with either the non-hydrolysable ATP analog AMP-PNP or the ATPase inhibitor BeFx significantly reduced the stimulatory effect of stretch. We employed a point mutagenic approach to determine that a single residue (K1337) in the hairpin loop proximal to the major MgATPase catalytic site in the SUR2A subunit is responsible for the difference in mechano-sensitivity between SUR2A and SUR1 containing KATP channels. Moreover, using a double cysteine mutant substitution in the hairpin loop region revealed the importance of a key residue-residue interaction in this region that transduces membrane mechanical forces into KATP channel stimulation via increases in channel MgATPase activity. With respect to KATP channel pharmacology, glibenclamide, but not glicalizide or repaglinide, was able to completely inhibit KATP channel mechano-sensitivity. In summary, our results provide a highly plausible molecular mechanism by which mechanical membrane forces are rapidly converted in changes in KATP channel activity that have implications for our understanding of cardiac KATP channels in physiological or pathophysiological settings that involve increased workload.
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Affiliation(s)
- Mohammad Fatehi
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Christian C Carter
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Nermeen Youssef
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Peter E Light
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.
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87
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Barbic M, Moreno A, Harris TD, Kay MW. Detachable glass microelectrodes for recording action potentials in active moving organs. Am J Physiol Heart Circ Physiol 2017; 312:H1248-H1259. [PMID: 28476925 DOI: 10.1152/ajpheart.00741.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 04/11/2017] [Accepted: 04/27/2017] [Indexed: 12/17/2022]
Abstract
Here, we describe new detachable floating glass micropipette electrode devices that provide targeted action potential recordings in active moving organs without requiring constant mechanical constraint or pharmacological inhibition of tissue motion. The technology is based on the concept of a glass micropipette electrode that is held firmly during cell targeting and intracellular insertion, after which a 100-µg glass microelectrode, a "microdevice," is gently released to remain within the moving organ. The microdevices provide long-term recordings of action potentials, even during millimeter-scale movement of tissue in which the device is embedded. We demonstrate two different glass micropipette electrode holding and detachment designs appropriate for the heart (sharp glass microdevices for cardiac myocytes in rats, guinea pigs, and humans) and the brain (patch glass microdevices for neurons in rats). We explain how microdevices enable measurements of multiple cells within a moving organ that are typically difficult with other technologies. Using sharp microdevices, action potential duration was monitored continuously for 15 min in unconstrained perfused hearts during global ischemia-reperfusion, providing beat-to-beat measurements of changes in action potential duration. Action potentials from neurons in the hippocampus of anesthetized rats were measured with patch microdevices, which provided stable base potentials during long-term recordings. Our results demonstrate that detachable microdevices are an elegant and robust tool to record electrical activity with high temporal resolution and cellular level localization without disturbing the physiological working conditions of the organ.NEW & NOTEWORTHY Cellular action potential measurements within tissue using glass micropipette electrodes usually require tissue immobilization, potentially influencing the physiological relevance of the measurement. Here, we addressed this limitation with novel 100-µg detachable glass microelectrodes that can be precisely positioned to provide long-term measurements of action potential duration during unconstrained tissue movement.
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Affiliation(s)
- Mladen Barbic
- Applied Physics and Instrumentation Group, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia; and
| | - Angel Moreno
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
| | - Tim D Harris
- Applied Physics and Instrumentation Group, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia; and
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
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88
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Wang S, Borschel WF, Heyman S, Hsu P, Nichols CG. Conformational changes at cytoplasmic intersubunit interactions control Kir channel gating. J Biol Chem 2017; 292:10087-10096. [PMID: 28446610 DOI: 10.1074/jbc.m117.785154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/17/2017] [Indexed: 02/02/2023] Open
Abstract
The defining structural feature of inward-rectifier potassium (Kir) channels is the unique Kir cytoplasmic domain. Recently we showed that salt bridges located at the cytoplasmic domain subunit interfaces (CD-Is) of eukaryotic Kir channels control channel gating via stability of a novel inactivated closed state. The cytoplasmic domains of prokaryotic and eukaryotic Kir channels show similar conformational rearrangements to the common gating ligand, phosphatidylinositol bisphosphate (PIP2), although these exhibit opposite coupling to opening and closing transitions. In Kir2.1, mutation of one of these CD-I salt bridge residues (R204A) reduces apparent PIP2 sensitivity of channel activity, and here we show that Ala or Cys substitutions of the functionally equivalent residue (Arg-165) in the prokaryotic Kir channel KirBac1.1 also significantly decrease sensitivity of the channel to PIP2 (by 5-30-fold). To further understand the structural basis of CD-I control of Kir channel gating, we examined the effect of the R165A mutation on PIP2-induced changes in channel function and conformation. Single-channel analyses indicated that the R165A mutation disrupts the characteristic long interburst closed state of reconstituted KirBac1.1 in giant liposomes, resulting in a higher open probability due to more frequent opening bursts. Intramolecular FRET measurements indicate that, relative to wild-type channels, the R165A mutation results in splaying of the cytoplasmic domains away from the central axis and that PIP2 essentially induces opposite motions of the major β-sheet in this channel mutant. We conclude that the removal of stabilizing CD-I salt bridges results in a collapsed state of the Kir domain.
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Affiliation(s)
- Shizhen Wang
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - William F Borschel
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sarah Heyman
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Phillip Hsu
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
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89
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Feng Y, Liu J, Wang M, Liu M, Shi L, Yuan W, Ye J, Hu D, Wan J. The E23K variant of the Kir6.2 subunit of the ATP-sensitive potassium channel increases susceptibility to ventricular arrhythmia in response to ischemia in rats. Int J Cardiol 2017; 232:192-198. [DOI: 10.1016/j.ijcard.2017.01.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 12/27/2016] [Accepted: 01/03/2017] [Indexed: 12/22/2022]
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90
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Cooper PE, Sala-Rabanal M, Lee SJ, Nichols CG. Differential mechanisms of Cantú syndrome-associated gain of function mutations in the ABCC9 (SUR2) subunit of the KATP channel. ACTA ACUST UNITED AC 2017; 146:527-40. [PMID: 26621776 PMCID: PMC4664827 DOI: 10.1085/jgp.201511495] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations that increase the activity of ATP-sensitive potassium channels through either enhanced activation by MgADP or decreased sensitivity to inhibition by ATP can lead to Cantú syndrome. Cantú syndrome (CS) is a rare disease characterized by congenital hypertrichosis, distinct facial features, osteochondrodysplasia, and cardiac defects. Recent genetic analysis has revealed that the majority of CS patients carry a missense mutation in ABCC9, which codes for the sulfonylurea receptor SUR2. SUR2 subunits couple with Kir6.x, inwardly rectifying potassium pore-forming subunits, to form adenosine triphosphate (ATP)-sensitive potassium (KATP) channels, which link cell metabolism to membrane excitability in a variety of tissues including vascular smooth muscle, skeletal muscle, and the heart. The functional consequences of multiple uncharacterized CS mutations remain unclear. Here, we have focused on determining the functional consequences of three documented human CS-associated ABCC9 mutations: human P432L, A478V, and C1043Y. The mutations were engineered in the equivalent position in rat SUR2A (P429L, A475V, and C1039Y), and each was coexpressed with mouse Kir6.2. Using macroscopic rubidium (86Rb+) efflux assays, we show that KATP channels formed with P429L, A475V, or C1039Y mutants enhance KATP activity compared with wild-type (WT) channels. We used inside-out patch-clamp electrophysiology to measure channel sensitivity to ATP inhibition and to MgADP activation. For P429L and A475V mutants, sensitivity to ATP inhibition was comparable to WT channels, but activation by MgADP was significantly greater. C1039Y-dependent channels were significantly less sensitive to inhibition by ATP or by glibenclamide, but MgADP activation was comparable to WT. The results indicate that these three CS mutations all lead to overactive KATP channels, but at least two mechanisms underlie the observed gain of function: decreased ATP inhibition and enhanced MgADP activation.
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Affiliation(s)
- Paige E Cooper
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Monica Sala-Rabanal
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Sun Joo Lee
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
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91
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Ighodaro ET, Abner EL, Fardo DW, Lin AL, Katsumata Y, Schmitt FA, Kryscio RJ, Jicha GA, Neltner JH, Monsell SE, Kukull WA, Moser DK, Appiah F, Bachstetter AD, Van Eldik LJ, Nelson PT. Risk factors and global cognitive status related to brain arteriolosclerosis in elderly individuals. J Cereb Blood Flow Metab 2017; 37:201-216. [PMID: 26738751 PMCID: PMC5363738 DOI: 10.1177/0271678x15621574] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/19/2015] [Accepted: 11/16/2015] [Indexed: 01/19/2023]
Abstract
Risk factors and cognitive sequelae of brain arteriolosclerosis pathology are not fully understood. To address this, we used multimodal data from the National Alzheimer's Coordinating Center and Alzheimer's Disease Neuroimaging Initiative data sets. Previous studies showed evidence of distinct neurodegenerative disease outcomes and clinical-pathological correlations in the "oldest-old" compared to younger cohorts. Therefore, using the National Alzheimer's Coordinating Center data set, we analyzed clinical and neuropathological data from two groups according to ages at death: < 80 years (n = 1008) and ≥80 years (n = 1382). In both age groups, severe brain arteriolosclerosis was associated with worse performances on global cognition tests. Hypertension (but not diabetes) was a brain arteriolosclerosis risk factor in the younger group. In the ≥ 80 years age at death group, an ABCC9 gene variant (rs704180), previously associated with aging-related hippocampal sclerosis, was also associated with brain arteriolosclerosis. A post-hoc arterial spin labeling neuroimaging experiment indicated that ABCC9 genotype is associated with cerebral blood flow impairment; in a convenience sample from Alzheimer's Disease Neuroimaging Initiative (n = 15, homozygous individuals), non-risk genotype carriers showed higher global cerebral blood flow compared to risk genotype carriers. We conclude that brain arteriolosclerosis is associated with altered cognitive status and a novel vascular genetic risk factor.
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Affiliation(s)
- Eseosa T Ighodaro
- Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY, USA.,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Erin L Abner
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Epidemiology, University of Kentucky, Lexington, KY, USA
| | - David W Fardo
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Biostatistics, University of Kentucky, Lexington, KY, USA
| | - Ai-Ling Lin
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA.,Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Yuriko Katsumata
- Department of Biostatistics, University of Kentucky, Lexington, KY, USA
| | - Frederick A Schmitt
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Neurology, University of Kentucky, Lexington, KY, USA
| | - Richard J Kryscio
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Biostatistics, University of Kentucky, Lexington, KY, USA.,Department of Statistics, University of Kentucky, Lexington, KY, USA
| | - Gregory A Jicha
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Neurology, University of Kentucky, Lexington, KY, USA
| | - Janna H Neltner
- Department of Pathology and Laboratory Medicine, Division of Neuropathology, University of Kentucky, Lexington, KY, USA
| | - Sarah E Monsell
- National Alzheimer's Coordinating Center, University of Washington, Seattle, WA, USA
| | - Walter A Kukull
- National Alzheimer's Coordinating Center, University of Washington, Seattle, WA, USA.,Department of Epidemiology, University of Washington, Seattle, WA, USA
| | - Debra K Moser
- College of Nursing, University of Kentucky, Lexington, KY, USA
| | - Frank Appiah
- Department of Biostatistics, University of Kentucky, Lexington, KY, USA
| | - Adam D Bachstetter
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Linda J Van Eldik
- Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY, USA.,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | | | - Peter T Nelson
- Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY, USA .,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA.,Department of Pathology and Laboratory Medicine, Division of Neuropathology, University of Kentucky, Lexington, KY, USA
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92
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93
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Channel-transporter complexes: an emerging theme in cell signaling. Biochem J 2016; 473:3759-3763. [PMID: 27789743 DOI: 10.1042/bcj20160685c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/02/2016] [Indexed: 11/17/2022]
Abstract
In a recent edition of Biochemical Journal, Mistry et al. described the discovery of a novel protein complex, formed from the epithelial sodium channel (ENaC) and the sodium chloride cotransporter (NCC) [Mistry et al. (2016) Biochem. J. 473, 3237–3252]. The importance of these two proteins in the regulation of salt balance and blood pressure has long been known, as has their overlapping expression in the distal convoluted tubule of the kidney. The new study by Mistry et al. now demonstrates their physical interaction in the kidney and when heterologously co-expressed. Furthermore, the authors demonstrate some degree of functional co-dependence between ENaC and NCC, with pharmacological inhibition of the latter diminishing activity of the former when the two are co-assembled. This novel and potentially important interaction adds to a growing number of recently identified channel-transporter ('chansporter') complexes, which together constitute an emerging theme in cell signaling.
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94
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Leon Guerrero CR, Pathak S, Grange DK, Singh GK, Nichols CG, Lee JM, Vo KD. Neurologic and neuroimaging manifestations of Cantú syndrome: A case series. Neurology 2016; 87:270-6. [PMID: 27316244 DOI: 10.1212/wnl.0000000000002861] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 04/11/2016] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To describe the neurologic and neuroimaging manifestations associated with Cantú syndrome. METHODS We evaluated 10 patients with genetically confirmed Cantú syndrome. All adult patients, and pediatric patients who were able to cooperate and complete the studies, underwent neuroimaging, including vascular imaging. A salient neurologic history and examination was obtained for all patients. RESULTS We observed diffusely dilated and tortuous cerebral blood vessels in all patients who underwent vascular imaging. White matter changes were observed in all patients who completed an MRI brain study. Two patients had a persistent trigeminal artery. One patient had an occluded right middle cerebral artery. One patient had transient white matter changes suggestive of posterior reversible encephalopathic syndrome. Four patients had migraines with one patient having complicated migraines. Seizures were seen in early life but infrequent. The majority of patients had mild developmental delays and one patient had a diagnosis of autism. CONCLUSIONS Cantú syndrome is associated with various neurologic manifestations, particularly cerebrovascular findings including dilated and tortuous cerebral vessels, white matter changes, and persistent fetal circulation. Involvement of the KATP SUR2/Kir6.1 subtype potentially plays an important role in the neurologic manifestations of Cantú syndrome.
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Affiliation(s)
- Christopher R Leon Guerrero
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO
| | - Sheel Pathak
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO
| | - Dorothy K Grange
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO
| | - Gautam K Singh
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO
| | - Colin G Nichols
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO
| | - Jin-Moo Lee
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO.
| | - Katie D Vo
- From George Washington University (C.R.L.G.), Washington, DC; and Washington University School of Medicine (S.P., D.K.G., G.K.S., C.G.N., J.-M.L., K.D.V.), St. Louis, MO.
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95
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Nelson PT, Trojanowski JQ, Abner EL, Al-Janabi OM, Jicha GA, Schmitt FA, Smith CD, Fardo DW, Wang WX, Kryscio RJ, Neltner JH, Kukull WA, Cykowski MD, Van Eldik LJ, Ighodaro ET. "New Old Pathologies": AD, PART, and Cerebral Age-Related TDP-43 With Sclerosis (CARTS). J Neuropathol Exp Neurol 2016; 75:482-98. [PMID: 27209644 PMCID: PMC6366658 DOI: 10.1093/jnen/nlw033] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 12/12/2022] Open
Abstract
The pathology-based classification of Alzheimer's disease (AD) and other neurodegenerative diseases is a work in progress that is important for both clinicians and basic scientists. Analyses of large autopsy series, biomarker studies, and genomics analyses have provided important insights about AD and shed light on previously unrecognized conditions, enabling a deeper understanding of neurodegenerative diseases in general. After demonstrating the importance of correct disease classification for AD and primary age-related tauopathy, we emphasize the public health impact of an underappreciated AD "mimic," which has been termed "hippocampal sclerosis of aging" or "hippocampal sclerosis dementia." This pathology affects >20% of individuals older than 85 years and is strongly associated with cognitive impairment. In this review, we provide an overview of current hypotheses about how genetic risk factors (GRN, TMEM106B, ABCC9, and KCNMB2), and other pathogenetic influences contribute to TDP-43 pathology and hippocampal sclerosis. Because hippocampal sclerosis of aging affects the "oldest-old" with arteriolosclerosis and TDP-43 pathologies that extend well beyond the hippocampus, more appropriate terminology for this disease is required. We recommend "cerebral age-related TDP-43 and sclerosis" (CARTS). A detailed case report is presented, which includes neuroimaging and longitudinal neurocognitive data. Finally, we suggest a neuropathology-based diagnostic rubric for CARTS.
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Affiliation(s)
- Peter T Nelson
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC).
| | - John Q Trojanowski
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Erin L Abner
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Omar M Al-Janabi
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Gregory A Jicha
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Frederick A Schmitt
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Charles D Smith
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - David W Fardo
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Wang-Xia Wang
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Richard J Kryscio
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Janna H Neltner
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Walter A Kukull
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Matthew D Cykowski
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Linda J Van Eldik
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
| | - Eseosa T Ighodaro
- From the Department of Pathology, Division of Neuropathology (PTN, JHN), Department of Neurology (GAJ, FAS, CDS), Department of Statistics (DWF, RJK), Department of Anatomy and Neurobiology (PTN, JHN, LJVE, ETI), Department of Epidemiology (ELA), and Sanders-Brown Center on Aging (PTN, ELA, OMA-J, GAJ, FAS, CDS, DWF, WXW, RJK, LJVE, ETI), University of Kentucky, Lexington, Kentucky; Department of Pathology & Laboratory Medicine and Center for Neurodegenerative Disease Research, University of Pennsylvania, Philadelphia, Pennsylvannia (JQT); Department of Epidemiology, University of Washington, Seattle, Washington (WAK); and Department of Pathology, Houston Methodist Hospital, Houston, Texas (MDC)
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96
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K(ATP) channel gain-of-function leads to increased myocardial L-type Ca(2+) current and contractility in Cantu syndrome. Proc Natl Acad Sci U S A 2016; 113:6773-8. [PMID: 27247394 DOI: 10.1073/pnas.1606465113] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Cantu syndrome (CS) is caused by gain-of-function (GOF) mutations in genes encoding pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) KATP channel subunits. We show that patients with CS, as well as mice with constitutive (cGOF) or tamoxifen-induced (icGOF) cardiac-specific Kir6.1 GOF subunit expression, have enlarged hearts, with increased ejection fraction and increased contractility. Whole-cell voltage-clamp recordings from cGOF or icGOF ventricular myocytes (VM) show increased basal L-type Ca(2+) current (LTCC), comparable to that seen in WT VM treated with isoproterenol. Mice with vascular-specific expression (vGOF) show left ventricular dilation as well as less-markedly increased LTCC. Increased LTCC in KATP GOF models is paralleled by changes in phosphorylation of the pore-forming α1 subunit of the cardiac voltage-gated calcium channel Cav1.2 at Ser1928, suggesting enhanced protein kinase activity as a potential link between increased KATP current and CS cardiac pathophysiology.
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97
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Tricarico D, Selvaggi M, Passantino G, De Palo P, Dario C, Centoducati P, Tateo A, Curci A, Maqoud F, Mele A, Camerino GM, Liantonio A, Imbrici P, Zizzo N. ATP Sensitive Potassium Channels in the Skeletal Muscle Function: Involvement of the KCNJ11(Kir6.2) Gene in the Determination of Mechanical Warner Bratzer Shear Force. Front Physiol 2016; 7:167. [PMID: 27242541 PMCID: PMC4862255 DOI: 10.3389/fphys.2016.00167] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/25/2016] [Indexed: 12/25/2022] Open
Abstract
The ATP-sensitive K+-channels (KATP) are distributed in the tissues coupling metabolism with K+ ions efflux. KATP subunits are encoded by KCNJ8 (Kir6.1), KCNJ11 (Kir6.2), ABCC8 (SUR1), and ABCC9 (SUR2) genes, alternative RNA splicing give rise to SUR variants that confer distinct physiological properties on the channel. An high expression/activity of the sarco-KATP channel is observed in various rat fast-twitch muscles, characterized by elevated muscle strength, while a low expression/activity is observed in the slow-twitch muscles characterized by reduced strength and frailty. Down-regulation of the KATP subunits of fast-twitch fibers is found in conditions characterized by weakness and frailty. KCNJ11 gene knockout mice have reduced glycogen, lean phenotype, lower body fat, and weakness. KATP channel is also a sensor of muscle atrophy. The KCNJ11 gene is located on BTA15, close to a QTL for meat tenderness, it has also a role in glycogen storage, a key mechanism of the postmortem transformation of muscle into meat. The role of KCNJ11 gene in muscle function may underlie an effect of KCNJ11 genotypes on meat tenderness, as recently reported. The fiber phenotype and genotype are important in livestock production science. Quantitative traits including meat production and quality are influenced both by environment and genes. Molecular markers can play an important role in the genetic improvement of animals through breeding strategies. Many factors influence the muscle Warner-Bratzler shear force including breed, age, feeding, the biochemical, and functional parameters. The role of KCNJ11gene and related genes on muscle tenderness will be discussed in the present review.
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Affiliation(s)
- Domenico Tricarico
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Maria Selvaggi
- Section of Veterinary Science and Animal Production, Department of Emergency and Organ Transplantation (DETO), University of Bari Aldo Moro Valenzano, Italy
| | | | - Pasquale De Palo
- Department of Veterinary Medicine, University of Bari Aldo Moro Bari, Italy
| | - Cataldo Dario
- Section of Veterinary Science and Animal Production, Department of Emergency and Organ Transplantation (DETO), University of Bari Aldo Moro Valenzano, Italy
| | | | - Alessandra Tateo
- Department of Veterinary Medicine, University of Bari Aldo Moro Bari, Italy
| | - Angela Curci
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Fatima Maqoud
- Department of Pharmacy-Drug Science, University of Bari Aldo MoroBari, Italy; Faculty of Science, Chouaib Doukkali UniversityEl Jadida, Morocco
| | - Antonietta Mele
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Giulia M Camerino
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Antonella Liantonio
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy-Drug Science, University of Bari Aldo Moro Bari, Italy
| | - Nicola Zizzo
- Department of Veterinary Medicine, University of Bari Aldo Moro Bari, Italy
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98
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The shifting landscape of KATP channelopathies and the need for 'sharper' therapeutics. Future Med Chem 2016; 8:789-802. [PMID: 27161588 DOI: 10.4155/fmc-2016-0005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
ATP-sensitive potassium (KATP) channels play fundamental roles in the regulation of endocrine, neural and cardiovascular function. Small-molecule inhibitors (e.g., sulfonylurea drugs) or activators (e.g., diazoxide) acting on SUR1 or SUR2 have been used clinically for decades to manage the inappropriate secretion of insulin in patients with Type 2 diabetes, hyperinsulinism and intractable hypertension. More recently, the discovery of rare disease-causing mutations in KATP channel-encoding genes has highlighted the need for new therapeutics for the treatment of certain forms of neonatal diabetes mellitus, congenital hyperinsulinism and Cantu syndrome. Here, we provide a high-level overview of the pathophysiology of these diseases and discuss the development of a flexible high-throughput screening platform to enable the development of new classes of KATP channel modulators.
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99
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Schmidt K, Windler R, de Wit C. Communication Through Gap Junctions in the Endothelium. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 77:209-40. [PMID: 27451099 DOI: 10.1016/bs.apha.2016.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A swarm of fish displays a collective behavior (swarm behavior) and moves "en masse" despite the huge number of individual animals. In analogy, organ function is supported by a huge number of cells that act in an orchestrated fashion and this applies also to vascular cells along the vessel length. It is obvious that communication is required to achieve this vital goal. Gap junctions with their modular bricks, connexins (Cxs), provide channels that interlink the cytosol of adjacent cells by a pore sealed against the extracellular space. This allows the transfer of ions and charge and thereby the travel of membrane potential changes along the vascular wall. The endothelium provides a low-resistance pathway that depends crucially on connexin40 which is required for long-distance conduction of dilator signals in the microcirculation. The experimental evidence for membrane potential changes synchronizing vascular behavior is manifold but the functional verification of a physiologic role is still open. Other molecules may also be exchanged that possibly contribute to the synchronization (eg, Ca(2+)). Recent data suggest that vascular Cxs have more functions than just facilitating communication. As pharmacological tools to modulate gap junctions are lacking, Cx-deficient mice provide currently the standard to unravel their vascular functions. These include arteriolar dilation during functional hyperemia, hypoxic pulmonary vasoconstriction, vascular collateralization after ischemia, and feedback inhibition on renin secretion in the kidney.
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Affiliation(s)
- K Schmidt
- Institut für Physiologie, Universität zu Lübeck, Lübeck, Germany; Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK) e.V. (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
| | - R Windler
- Institut für Physiologie, Universität zu Lübeck, Lübeck, Germany; Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK) e.V. (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
| | - C de Wit
- Institut für Physiologie, Universität zu Lübeck, Lübeck, Germany; Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK) e.V. (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany.
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100
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Abstract
KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.
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Affiliation(s)
- Monique N Foster
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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