151
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Martin GM, Sung MW, Shyng SL. Pharmacological chaperones of ATP-sensitive potassium channels: Mechanistic insight from cryoEM structures. Mol Cell Endocrinol 2020; 502:110667. [PMID: 31821855 PMCID: PMC6994177 DOI: 10.1016/j.mce.2019.110667] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/22/2019] [Accepted: 11/22/2019] [Indexed: 02/07/2023]
Abstract
ATP-sensitive potassium (KATP) channels are uniquely evolved protein complexes that couple cell energy levels to cell excitability. They govern a wide range of physiological processes including hormone secretion, neuronal transmission, vascular dilation, and cardiac and neuronal preconditioning against ischemic injuries. In pancreatic β-cells, KATP channels composed of Kir6.2 and SUR1, encoded by KCNJ11 and ABCC8, respectively, play a key role in coupling blood glucose concentration to insulin secretion. Mutations in ABCC8 or KCNJ11 that diminish channel function result in congenital hyperinsulinism. Many of these mutations principally hamper channel biogenesis and hence trafficking to the cell surface. Several small molecules have been shown to correct channel biogenesis and trafficking defects. Here, we review studies aimed at understanding how mutations impair channel biogenesis and trafficking and how pharmacological ligands overcome channel trafficking defects, particularly highlighting recent cryo-EM structural studies which have shed light on the mechanisms of channel assembly and pharmacological chaperones.
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Affiliation(s)
- Gregory M Martin
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Min Woo Sung
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA.
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152
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Papanicolaou KN, Ashok D, Liu T, Bauer TM, Sun J, Li Z, da Costa E, D'Orleans CC, Nathan S, Lefer DJ, Murphy E, Paolocci N, Foster DB, O'Rourke B. Global knockout of ROMK potassium channel worsens cardiac ischemia-reperfusion injury but cardiomyocyte-specific knockout does not: Implications for the identity of mitoKATP. J Mol Cell Cardiol 2020; 139:176-189. [PMID: 32004507 PMCID: PMC7849919 DOI: 10.1016/j.yjmcc.2020.01.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/16/2020] [Accepted: 01/23/2020] [Indexed: 01/29/2023]
Abstract
The renal-outer-medullary‑potassium (ROMK) channel, mutated in Bartter's syndrome, regulates ion exchange in kidney, but its extra-renal functions remain unknown. Additionally, ROMK was postulated to be the pore-forming subunit of the mitochondrial ATP-sensitive K+ channel (mitoKATP), a mediator of cardioprotection. Using global and cardiomyocyte-specific knockout mice (ROMK-GKO and ROMK-CKO respectively), we characterize the effects of ROMK knockout on mitochondrial ion handling, the response to pharmacological KATP channel modulators, and ischemia/reperfusion (I/R) injury. Mitochondria from ROMK-GKO hearts exhibited a lower threshold for Ca2+-triggered permeability transition pore (mPTP) opening but normal matrix volume changes during oxidative phosphorylation. Isolated perfused ROMK-GKO hearts exhibited impaired functional recovery and increased infarct size when I/R was preceded by an ischemic preconditioning (IPC) protocol. Because ROMK-GKO mice exhibited severe renal defects and cardiac remodeling, we further characterized ROMK-CKO hearts to avoid confounding systemic effects. Mitochondria from ROMK-CKO hearts had unchanged matrix volume responses during oxidative phosphorylation and still swelled upon addition of a mitoKATP opener, but exhibited a lower threshold for mPTP opening, similar to GKO mitochondria. Nevertheless, I/R induced damage was not exacerbated in ROMK-CKO hearts, either ex vivo or in vivo. Lastly, we examined the response of ROMK-CKO hearts to ex vivo I/R injury with or without IPC and found that IPC still protected these hearts, suggesting that cardiomyocyte ROMK does not participate significantly in the cardioprotective pathway elicited by IPC. Collectively, our findings from these novel strains of mice suggest that cardiomyocyte ROMK is not a central mediator of mitoKATP function, although it can affect mPTP activation threshold.
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Affiliation(s)
- Kyriakos N Papanicolaou
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Deepthi Ashok
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ting Liu
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Tyler M Bauer
- Cardiovascular Branch, NHLBI, NIH, 10 Center Drive, Bethesda, MD, USA
| | - Junhui Sun
- Cardiovascular Branch, NHLBI, NIH, 10 Center Drive, Bethesda, MD, USA
| | - Zhen Li
- Cardiovascular Center of Excellence, Louisiana State University (LSU) Health Sciences Center, New Orleans, LA, USA; Department of Pharmacology and Experimental Therapeutics, LSU Health Sciences Center, New Orleans, LA, USA
| | - Eduardo da Costa
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Charles Crepy D'Orleans
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sara Nathan
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David J Lefer
- Cardiovascular Center of Excellence, Louisiana State University (LSU) Health Sciences Center, New Orleans, LA, USA; Department of Pharmacology and Experimental Therapeutics, LSU Health Sciences Center, New Orleans, LA, USA
| | - Elizabeth Murphy
- Cardiovascular Branch, NHLBI, NIH, 10 Center Drive, Bethesda, MD, USA
| | - Nazareno Paolocci
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - D Brian Foster
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Brian O'Rourke
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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153
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Huang Y, Hu D, Huang C, Nichols CG. Genetic Discovery of ATP-Sensitive K + Channels in Cardiovascular Diseases. Circ Arrhythm Electrophysiol 2020; 12:e007322. [PMID: 31030551 DOI: 10.1161/circep.119.007322] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ATP-sensitive K+ (KATP) channels are hetero-octameric protein complexes comprising 4 pore-forming (Kir6.x) subunits and 4 regulatory sulfonylurea receptor (SURx) subunits. They are prominent in myocytes, pancreatic β cells, and neurons and link cellular metabolism with membrane excitability. Using genetically modified animals and genomic analysis in patients, recent studies have implicated certain ATP-sensitive K+ channel subtypes in physiological and pathological processes in a variety of cardiovascular diseases. In this review, we focus on the causal relationship between ATP-sensitive K+ channel activity and pathophysiology in the cardiovascular system, particularly from the perspective of genetic changes in human and animal models.
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Affiliation(s)
- Yan Huang
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Congxin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases and Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO (C.G.N.)
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154
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Yang HQ, Pérez-Hernández M, Sanchez-Alonso J, Shevchuk A, Gorelik J, Rothenberg E, Delmar M, Coetzee WA. Ankyrin-G mediates targeting of both Na + and K ATP channels to the rat cardiac intercalated disc. eLife 2020; 9:52373. [PMID: 31934859 PMCID: PMC7299345 DOI: 10.7554/elife.52373] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/11/2020] [Indexed: 12/12/2022] Open
Abstract
We investigated targeting mechanisms of Na+ and KATP channels to the intercalated disk (ICD) of cardiomyocytes. Patch clamp and surface biotinylation data show reciprocal downregulation of each other’s surface density. Mutagenesis of the Kir6.2 ankyrin binding site disrupts this functional coupling. Duplex patch clamping and Angle SICM recordings show that INa and IKATP functionally co-localize at the rat ICD, but not at the lateral membrane. Quantitative STORM imaging show that Na+ and KATP channels are localized close to each other and to AnkG, but not to AnkB, at the ICD. Peptides corresponding to Nav1.5 and Kir6.2 ankyrin binding sites dysregulate targeting of both Na+ and KATP channels to the ICD, but not to lateral membranes. Finally, a clinically relevant gene variant that disrupts KATP channel trafficking also regulates Na+ channel surface expression. The functional coupling between these two channels need to be considered when assessing clinical variants and therapeutics.
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Affiliation(s)
- Hua-Qian Yang
- Pediatrics, NYU School of Medicine, New York, United States
| | | | - Jose Sanchez-Alonso
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
| | - Andriy Shevchuk
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Julia Gorelik
- National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
| | - Eli Rothenberg
- Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, United States
| | - Mario Delmar
- Medicine, NYU School of Medicine, New York, United States.,Cell Biology, NYU School of Medicine, New York, United States
| | - William A Coetzee
- Pediatrics, NYU School of Medicine, New York, United States.,Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, United States.,Neuroscience and Physiology, NYU School of Medicine, New York, United States
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155
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Abstract
Today, excluding insulin, there are eight classes of anti-diabetic medicines that have been added to the pharmacy since the introduction of metformin in the mid-1950s; the sulfonylureas, biguanides, thiazolidinediones, α-glucosidase inhibitors, meglitinides, incretins, and sodium glucose transport 2 inhibitors. Does the fact that metformin is still first-line treatment suggest that our drug discovery efforts over the past 60 years have not been good enough? Or does it suggest that diabetes is such a complex disorder that no single treatment, other than gastric bypass surgery, can affect true normalization of not only blood sugar but also the underlying pathologies? Our understanding of the disease has most definitely improved which may bring hope for the future in terms of science, but for it to be beneficial, this science has to be translated into better drug treatments for the disease. In this review, I have examined the eight classes of anti-diabetes drugs from a drug discovery perspective.
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Affiliation(s)
- John C Clapham
- Medical School, University of Buckingham, Buckingham, UK.
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156
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Afzal A, Figueroa EE, Kharade SV, Bittman K, Matlock BK, Flaherty DK, Denton JS. The LRRC8 volume-regulated anion channel inhibitor, DCPIB, inhibits mitochondrial respiration independently of the channel. Physiol Rep 2019; 7:e14303. [PMID: 31814333 PMCID: PMC6900491 DOI: 10.14814/phy2.14303] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
There has been a resurgence of interest in the volume-regulated anion channel (VRAC) since the recent cloning of the LRRC8A-E gene family that encodes VRAC. The channel is a heteromer comprised of LRRC8A and at least one other family member; disruption of LRRC8A expression abolishes VRAC activity. The best-in-class VRAC inhibitor, DCPIB, suffers from off-target activity toward several different channels and transporters. Considering that some anion channel inhibitors also suppress mitochondrial respiration, we systematically explored whether DCPIB inhibits respiration in wild type (WT) and LRRC8A-knockout HAP-1 and HEK-293 cells. Knockout of LRRC8A had no apparent effects on cell morphology, proliferation rate, mitochondrial content, or expression of several mitochondrial genes in HAP-1 cells. Addition of 10 µM DCPIB, a concentration typically used to inhibit VRAC, suppressed basal and ATP-linked respiration in part through uncoupling the inner mitochondrial membrane (IMM) proton gradient and membrane potential. Additionally, DCPIB inhibits the activity of complex I, II, and III of the electron transport chain (ETC). Surprisingly, the effects of DCPIB on mitochondrial function are also observed in HAP-1 and HEK-293 cells which lack LRRC8A expression. Finally, we demonstrate that DCPIB activates ATP-inhibitable potassium channels comprised of heterologously expressed Kir6.2 and SUR1 subunits. These data indicate that DCPIB suppresses mitochondrial respiration and ATP production by dissipating the mitochondrial membrane potential and inhibiting complexes I-III of the ETC. They further justify the need for the development of sharper pharmacological tools for evaluating the integrative physiology and therapeutic potential of VRAC in human diseases.
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Affiliation(s)
- Aqeela Afzal
- Department of Neurological SurgeryVanderbilt UniversityNashvilleTennessee
- Department of MedicineVanderbilt UniversityNashvilleTennessee
| | - Eric E. Figueroa
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
| | - Sujay V. Kharade
- Department of AnesthesiologyVanderbilt University Medical CenterNashvilleTennessee
| | | | - Brittany K. Matlock
- Vanderbilt Vaccine CenterVanderbilt University Medical CenterNashvilleTennessee
| | - David K. Flaherty
- Vanderbilt Vaccine CenterVanderbilt University Medical CenterNashvilleTennessee
| | - Jerod S. Denton
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
- Department of AnesthesiologyVanderbilt University Medical CenterNashvilleTennessee
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157
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Boodhansingh KE, Kandasamy B, Mitteer L, Givler S, De Leon DD, Shyng S, Ganguly A, Stanley CA. Novel dominant K ATP channel mutations in infants with congenital hyperinsulinism: Validation by in vitro expression studies and in vivo carrier phenotyping. Am J Med Genet A 2019; 179:2214-2227. [PMID: 31464105 PMCID: PMC6852436 DOI: 10.1002/ajmg.a.61335] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/02/2019] [Accepted: 08/05/2019] [Indexed: 12/17/2022]
Abstract
Inactivating mutations in the genes encoding the two subunits of the pancreatic beta-cell KATP channel, ABCC8 and KCNJ11, are the most common finding in children with congenital hyperinsulinism (HI). Interpreting novel missense variants in these genes is problematic, because they can be either dominant or recessive mutations, benign polymorphisms, or diabetes mutations. This report describes six novel missense variants in ABCC8 and KCNJ11 that were identified in 11 probands with congenital HI. One of the three ABCC8 mutations (p.Ala1458Thr) and all three KCNJ11 mutations were associated with responsiveness to diazoxide. Sixteen family members carried the ABCC8 or KCNJ11 mutations; only two had hypoglycemia detected at birth and four others reported symptoms of hypoglycemia. Phenotype testing of seven adult mutation carriers revealed abnormal protein-induced hypoglycemia in all; fasting hypoketotic hypoglycemia was demonstrated in four of the seven. All of six mutations were confirmed to cause dominant pathogenic defects based on in vitro expression studies in COSm6 cells demonstrating normal trafficking, but reduced responses to MgADP and diazoxide. These results indicate a combination of in vitro and in vivo phenotype tests can be used to differentiate dominant from recessive KATP channel HI mutations and personalize management of children with congenital HI.
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Affiliation(s)
- Kara E. Boodhansingh
- Division of Endocrinology and DiabetesThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
| | - Balamurugan Kandasamy
- Department of Biochemistry and Molecular BiologyOregon Health & Science UniversityPortlandOregon
| | - Lauren Mitteer
- Division of Endocrinology and DiabetesThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
| | - Stephanie Givler
- Division of Endocrinology and DiabetesThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
| | - Diva D. De Leon
- Division of Endocrinology and DiabetesThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
- Department of PediatricsPerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPennsylvania
| | - Show‐Ling Shyng
- Department of Biochemistry and Molecular BiologyOregon Health & Science UniversityPortlandOregon
| | - Arupa Ganguly
- Department of GeneticsThe Perelman School of Medicine at the University of PennsylvaniaPhiladelphiaPennsylvania
| | - Charles A. Stanley
- Division of Endocrinology and DiabetesThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvania
- Department of PediatricsPerelman School of Medicine at the University of PennsylvaniaPhiladelphiaPennsylvania
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158
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TRPM4-specific blocking antibody attenuates reperfusion injury in a rat model of stroke. Pflugers Arch 2019; 471:1455-1466. [PMID: 31664513 PMCID: PMC6892354 DOI: 10.1007/s00424-019-02326-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/17/2019] [Accepted: 10/22/2019] [Indexed: 01/08/2023]
Abstract
Reperfusion therapy is currently the gold standard treatment for acute ischemic stroke. However, reperfusion injuries such as oedema and haemorrhagic transformation largely limit the use of this potent treatment to a narrow time window. Recently, transient receptor potential melastatin 4 (TRPM4) channel has emerged as a potential target for vascular protection in stroke management. Non-specificity and side effects are major concerns for current TRPM4 blockers. The present study was undertaken to develop a novel TRPM4 blocker for stroke management. We report the generation of a TRPM4-specific antibody M4P which binds to a region close to the channel pore. M4P could inhibit TRPM4 current and downregulate TRPM4 surface expression, therefore prevent hypoxia-induced cell swelling. In the rat model of 3-h stroke reperfusion, application of M4P at 2 h after occlusion ameliorated reperfusion injury by improving blood–brain barrier integrity, and enhanced functional recovery. Our results demonstrate that TRPM4 blockade could attenuate reperfusion injury in stroke recanalization. When applied together with reperfusion treatments, TRPM4 blocking antibody has the potential to extend the therapeutic time window for acute ischemic stroke.
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159
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Wu JX, Ding D, Wang M, Chen L. Structural Insights into the Inhibitory Mechanism of Insulin Secretagogues on the Pancreatic ATP-Sensitive Potassium Channel. Biochemistry 2019; 59:18-25. [PMID: 31566370 DOI: 10.1021/acs.biochem.9b00692] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Sulfonylureas and glinides are commonly used oral insulin secretagogues (ISs) that act on the pancreatic ATP-sensitive potassium (KATP) channel to promote insulin secretion in order to lower the blood glucose level. Physiologically, KATP channels are inhibited by intracellular ATP and activated by Mg-ADP. Therefore, they sense the cellular energy status to regulate the permeability of potassium ions across the plasma membrane. The pancreatic KATP channel is composed of the pore-forming Kir6.2 subunits and the regulatory SUR1 subunits. Previous electrophysiological studies have established that ISs bind to the SUR1 subunit and inhibit the channel activity primarily by two mechanisms. First, ISs prevent Mg-ADP activation. Second, ISs inhibit the channel activity of Kir6.2 directly. Several cryo-EM structures of the pancreatic KATP channel determined recently have provided remarkable structural insights into these two mechanisms.
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Affiliation(s)
- Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China
| | - Dian Ding
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China.,Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Mengmeng Wang
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China.,Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Lei Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China
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160
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A family of orthologous proteins from centipede venoms inhibit the hKir6.2 channel. Sci Rep 2019; 9:14088. [PMID: 31575961 PMCID: PMC6773964 DOI: 10.1038/s41598-019-50688-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 09/11/2019] [Indexed: 11/15/2022] Open
Abstract
Inhibitors targeting ion channels are useful tools for studying their functions. Given the selectivity of any inhibitor for a channel is relative, more than one inhibitor of different affinities may be used to help identify the channel in a biological preparation. Here, we describe a family of small proteins in centipede venoms that inhibit the pore (hKir6.2) of a human ATP-sensitive K+ channel (hKATP). While the traditional peptide-sequencing service gradually vanishes from academic institutions, we tried to identify the sequences of inhibitory proteins purified from venoms by searching the sequences of the corresponding transcriptomes, a search guided by the key features of a known hKir6.2 inhibitor (SpTx1). The candidate sequences were cross-checked against the masses of purified proteins, and validated by testing the activity of recombinant proteins against hKir6.2. The four identified proteins (SsdTx1-3 and SsTx) inhibit hKATP channels with a Kd of <300 nM, compared to 15 nM for SpTx1. SsTx has previously been discovered to block human voltage-gated KCNQ K+ channels with a 2.5 μM Kd. Given that SsTx inhibits hKir6.2 with >10-fold lower Kd than it inhibits hKCNQ, SsTx may not be suitable for probing KCNQ channels in a biological preparation that also contains more-SsTx-sensitive KATP channels.
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161
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Hosford PS, Christie IN, Niranjan A, Aziz Q, Anderson N, Ang R, Lythgoe MF, Wells JA, Tinker A, Gourine AV. A critical role for the ATP-sensitive potassium channel subunit K IR6.1 in the control of cerebral blood flow. J Cereb Blood Flow Metab 2019; 39:2089-2095. [PMID: 29862863 PMCID: PMC6775590 DOI: 10.1177/0271678x18780602] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 04/20/2018] [Accepted: 05/01/2018] [Indexed: 12/19/2022]
Abstract
KIR6.1 (KCNJ8) is a subunit of ATP sensitive potassium channel (KATP) that plays an important role in the control of peripheral vascular tone and is highly expressed in brain contractile cells (vascular smooth muscle cells and pericytes). This study determined the effect of global deletion of the KIR6.1 subunit on cerebral blood flow, neurovascular coupling and cerebral oxygenation in mice. In KIR6.1 deficient mice resting cerebral blood flow and brain parenchymal partial pressure of oxygen (PO2) were found to be markedly lower compared to that in their wildtype littermates. However, cortical blood oxygen level dependent responses triggered by visual stimuli were not affected in conditions of KIR6.1 deficiency. These data suggest that KATP channels containing KIR6.1 subunit are critically important for the maintenance of normal cerebral perfusion and parenchymal PO2 but play no significant role in the mechanisms underlying functional changes in brain blood flow.
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Affiliation(s)
- Patrick S Hosford
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Arun Niranjan
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Qadeer Aziz
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Naomi Anderson
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Jack A Wells
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Andrew Tinker
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
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162
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Smeland MF, McClenaghan C, Roessler HI, Savelberg S, Hansen GÅM, Hjellnes H, Arntzen KA, Müller KI, Dybesland AR, Harter T, Sala-Rabanal M, Emfinger CH, Huang Y, Singareddy SS, Gunn J, Wozniak DF, Kovacs A, Massink M, Tessadori F, Kamel SM, Bakkers J, Remedi MS, Van Ghelue M, Nichols CG, van Haaften G. ABCC9-related Intellectual disability Myopathy Syndrome is a K ATP channelopathy with loss-of-function mutations in ABCC9. Nat Commun 2019; 10:4457. [PMID: 31575858 PMCID: PMC6773855 DOI: 10.1038/s41467-019-12428-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 08/30/2019] [Indexed: 11/30/2022] Open
Abstract
Mutations in genes encoding KATP channel subunits have been reported for pancreatic disorders and Cantú syndrome. Here, we report a syndrome in six patients from two families with a consistent phenotype of mild intellectual disability, similar facies, myopathy, and cerebral white matter hyperintensities, with cardiac systolic dysfunction present in the two oldest patients. Patients are homozygous for a splice-site mutation in ABCC9 (c.1320 + 1 G > A), which encodes the sulfonylurea receptor 2 (SUR2) subunit of KATP channels. This mutation results in an in-frame deletion of exon 8, which results in non-functional KATP channels in recombinant assays. SUR2 loss-of-function causes fatigability and cardiac dysfunction in mice, and reduced activity, cardiac dysfunction and ventricular enlargement in zebrafish. We term this channelopathy resulting from loss-of-function of SUR2-containing KATP channels ABCC9-related Intellectual disability Myopathy Syndrome (AIMS). The phenotype differs from Cantú syndrome, which is caused by gain-of-function ABCC9 mutations, reflecting the opposing consequences of KATP loss- versus gain-of-function.
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Affiliation(s)
- Marie F Smeland
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway.
| | - Conor McClenaghan
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Helen I Roessler
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Sanne Savelberg
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | | | - Helene Hjellnes
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Kjell Arne Arntzen
- Department of Neurology, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Clinical Medicine, UiT-The Arctic University of Norway, 9019, Tromsø, Norway
- The National Neuromuscular Centre of Norway, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Kai Ivar Müller
- Department of Neurology, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Clinical Medicine, UiT-The Arctic University of Norway, 9019, Tromsø, Norway
| | - Andreas Rosenberger Dybesland
- The National Neuromuscular Centre of Norway, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Physiotherapy, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Theresa Harter
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Monica Sala-Rabanal
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University, St Louis, MO, 63110, USA
| | - Chris H Emfinger
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Yan Huang
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Soma S Singareddy
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Jamie Gunn
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - David F Wozniak
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Attila Kovacs
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Maarten Massink
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Federico Tessadori
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
| | - Sarah M Kamel
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
| | - Jeroen Bakkers
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University, St Louis, MO, 63110, USA
| | - Marijke Van Ghelue
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Medical Genetics, the Arctic University of Norway, 9019, Tromsø, Norway
| | - Colin G Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands.
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Emelyanova L, Sra A, Schmuck EG, Raval AN, Downey FX, Jahangir A, Rizvi F, Ross GR. Impact of statins on cellular respiration and de-differentiation of myofibroblasts in human failing hearts. ESC Heart Fail 2019; 6:1027-1040. [PMID: 31520523 PMCID: PMC6816080 DOI: 10.1002/ehf2.12509] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 05/24/2019] [Accepted: 07/30/2019] [Indexed: 12/16/2022] Open
Abstract
AIMS Fibroblast to myofibroblast trans-differentiation with altered bioenergetics precedes cardiac fibrosis (CF). Either prevention of differentiation or promotion of de-differentiation could mitigate CF-related pathologies. We determined whether 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors-statins, commonly prescribed to patients at risk of heart failure (HF)-can de-differentiate myofibroblasts, alter cellular bioenergetics, and impact the human ventricular fibroblasts (hVFs) in HF patients. METHODS AND RESULTS Either in vitro statin treatment of differentiated myofibroblasts (n = 3-6) or hVFs, isolated from human HF patients under statin therapy (HF + statin) vs. without statins (HF) were randomly used (n = 4-12). In vitro, hVFs were differentiated by transforming growth factor-β1 (TGF-β1) for 72 h (TGF-72 h). Differentiation status and cellular oxygen consumption rate (OCR) were determined by α-smooth muscle actin (α-SMA) expression and Seahorse assay, respectively. Data are mean ± SEM except Seahorse (mean ± SD); P < 0.05, considered significant. In vitro, statins concentration-dependently de-differentiated the myofibroblasts. The respective half-maximal effective concentrations were 729 ± 13 nmol/L (atorvastatin), 3.6 ± 1 μmol/L (rosuvastatin), and 185 ± 13 nmol/L (simvastatin). Mevalonic acid (300 μmol/L), the reduced product of HMG-CoA, prevented the statin-induced de-differentiation (α-SMA expression: 31.4 ± 10% vs. 58.6 ± 12%). Geranylgeranyl pyrophosphate (GGPP, 20 μmol/L), a cholesterol synthesis-independent HMG-CoA reductase pathway intermediate, completely prevented the statin-induced de-differentiation (α-SMA/GAPDH ratios: 0.89 ± 0.05 [TGF-72 h + 72 h], 0.63 ± 0.02 [TGF-72 h + simvastatin], and 1.2 ± 0.08 [TGF-72 h + simvastatin + GGPP]). Cellular metabolism involvement was observed when co-incubation of simvastatin (200 nmol/L) with glibenclamide (10 μmol/L), a KATP channel inhibitor, attenuated the simvastatin-induced de-differentiation (0.84 ± 0.05). Direct inhibition of mitochondrial respiration by oligomycin (1 ng/mL) also produced a de-differentiation effect (0.33 ± 0.02). OCR (pmol O2 /min/μg protein) was significantly decreased in the simvastatin-treated hVFs, including basal (P = 0.002), ATP-linked (P = 0.01), proton leak-linked (P = 0.01), and maximal (P < 0.001). The OCR inhibition was prevented by GGPP (basal OCR [P = 0.02], spare capacity OCR [P = 0.008], and maximal OCR [P = 0.003]). Congruently, hVFs from HF showed an increased population of myofibroblasts while HF + statin group showed significantly reduced cellular respiration (basal OCR [P = 0.021], ATP-linked OCR [P = 0.047], maximal OCR [P = 0.02], and spare capacity OCR [P = 0.025]) and myofibroblast differentiation (α-SMA/GAPDH: 1 ± 0.19 vs. 0.23 ± 0.06, P = 0.01). CONCLUSIONS This study demonstrates the de-differentiating effect of statins, the underlying GGPP sensitivity, reduced OCR with potential activation of KATP channels, and their impact on the differentiation magnitude of hVFs in HF patients. This novel pleiotropic effect of statins may be exploited to reduce excessive CF in patients at risk of HF.
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Affiliation(s)
- Larisa Emelyanova
- Center for Integrative Research on Cardiovascular Aging, Aurora Health Care, St. Luke's Medical Center, 2900 W. Oklahoma Ave, Milwaukee, WI, 53215, USA
| | - Amar Sra
- Center for Integrative Research on Cardiovascular Aging, Aurora Health Care, St. Luke's Medical Center, 2900 W. Oklahoma Ave, Milwaukee, WI, 53215, USA
| | - Eric G Schmuck
- Department of Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Amish N Raval
- Department of Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Francis X Downey
- Aurora Cardiovascular Services, Aurora Sinai/Aurora St. Luke's Medical Centers, Milwaukee, WI, USA
| | - Arshad Jahangir
- Aurora Cardiovascular Services, Aurora Sinai/Aurora St. Luke's Medical Centers, Milwaukee, WI, USA.,Center for Advanced Atrial Fibrillation Therapies, Aurora Sinai/Aurora St. Luke's Medical Centers, Milwaukee, WI, USA
| | - Farhan Rizvi
- Center for Integrative Research on Cardiovascular Aging, Aurora Health Care, St. Luke's Medical Center, 2900 W. Oklahoma Ave, Milwaukee, WI, 53215, USA
| | - Gracious R Ross
- Center for Integrative Research on Cardiovascular Aging, Aurora Health Care, St. Luke's Medical Center, 2900 W. Oklahoma Ave, Milwaukee, WI, 53215, USA
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Kharade SV, Sanchez-Andres JV, Fulton MG, Shelton EL, Blobaum AL, Engers DW, Hofmann CS, Dadi PK, Lantier L, Jacobson DA, Lindsley CW, Denton JS. Structure-Activity Relationships, Pharmacokinetics, and Pharmacodynamics of the Kir6.2/SUR1-Specific Channel Opener VU0071063. J Pharmacol Exp Ther 2019; 370:350-359. [PMID: 31201216 PMCID: PMC6691189 DOI: 10.1124/jpet.119.257204] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 06/12/2019] [Indexed: 01/14/2023] Open
Abstract
Glucose-stimulated insulin secretion from pancreatic β-cells is controlled by ATP-regulated potassium (KATP) channels composed of Kir6.2 and sulfonylurea receptor 1 (SUR1) subunits. The KATP channel-opener diazoxide is FDA-approved for treating hyperinsulinism and hypoglycemia but suffers from off-target effects on vascular KATP channels and other ion channels. The development of more specific openers would provide critically needed tool compounds for probing the therapeutic potential of Kir6.2/SUR1 activation. Here, we characterize a novel scaffold activator of Kir6.2/SUR1 that our group recently discovered in a high-throughput screen. Optimization efforts with medicinal chemistry identified key structural elements that are essential for VU0071063-dependent opening of Kir6.2/SUR1. VU0071063 has no effects on heterologously expressed Kir6.1/SUR2B channels or ductus arteriole tone, indicating it does not open vascular KATP channels. VU0071063 induces hyperpolarization of β-cell membrane potential and inhibits insulin secretion more potently than diazoxide. VU0071063 exhibits metabolic and pharmacokinetic properties that are favorable for an in vivo probe and is brain penetrant. Administration of VU0071063 inhibits glucose-stimulated insulin secretion and glucose-lowering in mice. Taken together, these studies indicate that VU0071063 is a more potent and specific opener of Kir6.2/SUR1 than diazoxide and should be useful as an in vitro and in vivo tool compound for investigating the therapeutic potential of Kir6.2/SUR1 expressed in the pancreas and brain.
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Affiliation(s)
- Sujay V Kharade
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Juan Vicente Sanchez-Andres
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Mark G Fulton
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Elaine L Shelton
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Anna L Blobaum
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Darren W Engers
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Christopher S Hofmann
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Prasanna K Dadi
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Louise Lantier
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - David A Jacobson
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Craig W Lindsley
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
| | - Jerod S Denton
- Departments of Anesthesiology (S.V.K., J.S.D.) and Pediatrics (E.L.S.), Vanderbilt University Medical Center, Nashville, Tennessee; Department of Medicine, Jaume I University, Castellon de la Plana, Spain (J.V.S.-A.); Departments of Chemistry (M.G.F., C.W.L.), Pharmacology (M.G.F., A.L.B., D.W.E., C.S.H., C.W.L., J.S.D.), and Molecular Physiology and Biophysics (P.K.D., D.A.J.), and Mouse Metabolic Phenotyping Core (L.L.), Vanderbilt University, Nashville, Tennessee; and Vanderbilt Center for Neuroscience Drug Discovery, Franklin, Tennessee (D.W.E., A.L.B., C.W.L.)
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Jacobson DA, Shyng SL. Ion Channels of the Islets in Type 2 Diabetes. J Mol Biol 2019; 432:1326-1346. [PMID: 31473158 DOI: 10.1016/j.jmb.2019.08.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/19/2019] [Accepted: 08/21/2019] [Indexed: 02/06/2023]
Abstract
Ca2+ is an essential signal for pancreatic β-cell function. Ca2+ plays critical roles in numerous β-cell pathways such as insulin secretion, transcription, metabolism, endoplasmic reticulum function, and the stress response. Therefore, β-cell Ca2+ handling is tightly controlled. At the plasma membrane, Ca2+ entry primarily occurs through voltage-dependent Ca2+ channels. Voltage-dependent Ca2+ channel activity is dependent on orchestrated fluctuations in the plasma membrane potential or voltage, which are mediated via the activity of many ion channels. During the pathogenesis of type 2 diabetes the β-cell is exposed to stressful conditions, which result in alterations of Ca2+ handling. Some of the changes in β-cell Ca2+ handling that occur under stress result from perturbations in ion channel activity, expression or localization. Defective Ca2+ signaling in the diabetic β-cell alters function, limits insulin secretion and exacerbates hyperglycemia. In this review, we focus on the β-cell ion channels that control Ca2+ handling and how they impact β-cell dysfunction in type 2 diabetes.
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Affiliation(s)
- David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 7415 MRB4 (Langford), 2213 Garland Avenue, Nashville, TN 37232, USA.
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, L224, MRB 624, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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166
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Srikant S, Gaudet R. Mechanics and pharmacology of substrate selection and transport by eukaryotic ABC exporters. Nat Struct Mol Biol 2019; 26:792-801. [PMID: 31451804 DOI: 10.1038/s41594-019-0280-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Accepted: 07/17/2019] [Indexed: 01/27/2023]
Abstract
Much structural information has been amassed on ATP-binding cassette (ABC) transporters, including hundreds of structures of isolated domains and an increasing array of full-length transporters. The structures capture different steps in the transport cycle and have aided in the design and interpretation of computational simulations and biophysics experiments. These data provide a maturing, although still incomplete, elucidation of the protein dynamics and mechanisms of substrate selection and transit through the transporters. We present an updated view of the classical alternating-access mechanism as it applies to eukaryotic ABC transporters, focusing on type I exporters. Our model helps frame the progress in, and remaining questions about, transporter energetics, how substrates are selected and how ATP is consumed to perform work at the molecular scale. Many human ABC transporters are associated with disease; we highlight progress in understanding their pharmacology through the lens of structural biology and describe how this knowledge suggests approaches to pharmacologically targeting these transporters.
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Affiliation(s)
- Sriram Srikant
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
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167
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Paggio A, Checchetto V, Campo A, Menabò R, Di Marco G, Di Lisa F, Szabo I, Rizzuto R, De Stefani D. Identification of an ATP-sensitive potassium channel in mitochondria. Nature 2019; 572:609-613. [PMID: 31435016 PMCID: PMC6726485 DOI: 10.1038/s41586-019-1498-3] [Citation(s) in RCA: 173] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 07/25/2019] [Indexed: 11/09/2022]
Abstract
Mitochondria provide chemical energy for endoergonic reactions in the form of ATP, and their activity must meet cellular energy requirements, but the mechanisms that link organelle performance to ATP levels are poorly understood. Here we confirm the existence of a protein complex localized in mitochondria that mediates ATP-dependent potassium currents (that is, mitoKATP). We show that-similar to their plasma membrane counterparts-mitoKATP channels are composed of pore-forming and ATP-binding subunits, which we term MITOK and MITOSUR, respectively. In vitro reconstitution of MITOK together with MITOSUR recapitulates the main properties of mitoKATP. Overexpression of MITOK triggers marked organelle swelling, whereas the genetic ablation of this subunit causes instability in the mitochondrial membrane potential, widening of the intracristal space and decreased oxidative phosphorylation. In a mouse model, the loss of MITOK suppresses the cardioprotection that is elicited by pharmacological preconditioning induced by diazoxide. Our results indicate that mitoKATP channels respond to the cellular energetic status by regulating organelle volume and function, and thereby have a key role in mitochondrial physiology and potential effects on several pathological processes.
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Affiliation(s)
- Angela Paggio
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | - Antonio Campo
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | | | - Giulia Di Marco
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Fabio Di Lisa
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,CNR Institute of Neuroscience, Padova, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova, Italy.,CNR Institute of Neuroscience, Padova, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
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168
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Hendriks AM, Schrijnders D, Kleefstra N, de Vries EGE, Bilo HJG, Jalving M, Landman GWD. Sulfonylurea derivatives and cancer, friend or foe? Eur J Pharmacol 2019; 861:172598. [PMID: 31408647 DOI: 10.1016/j.ejphar.2019.172598] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 02/07/2023]
Abstract
Type 2 diabetes mellitus (T2DM) is associated with a higher risk of cancer and cancer-related mortality. Increased blood glucose and insulin levels in T2DM patients may be, at least in part, responsible for this effect. Indeed, lowering glucose and/or insulin levels pharmacologically appears to reduce cancer risk and progression, as has been demonstrated for the biguanide metformin in observational studies. Studies investigating the influence of sulfonylurea derivatives (SUs) on cancer risk have provided conflicting results, partly due to comparisons with metformin. Furthermore, little attention has been paid to within-class differences in systemic and off-target effects of the SUs. The aim of this systematic review is to discuss the available preclinical and clinical evidence on how the different SUs influence cancer development and risk. Databases including PubMed, Cochrane, Database of Abstracts on Reviews and Effectiveness, and trial registries were systematically searched for available clinical and preclinical evidence on within-class differences of SUs and cancer risk. The overall preclinical and clinical evidence suggest that the influence of SUs on cancer risk in T2DM patients differs between the various SUs. Potential mechanisms include differing affinities for the sulfonylurea receptors and thus differential systemic insulin exposure and off-target anti-cancer effects mediated for example through potassium transporters and drug export pumps. Preclinical evidence supports potential anti-cancer effects of SUs, which are of interest for further studies and potentially repurposing of SUs. At this time, the evidence on differences in cancer risk between SUs is not strong enough to guide clinical decision making.
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Affiliation(s)
- Anne M Hendriks
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Dennis Schrijnders
- Langerhans Medical Research Group, Zwolle, the Netherlands; Diabetes Center, Isala Hospital, Zwolle, the Netherlands
| | | | - Elisabeth G E de Vries
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Henk J G Bilo
- Diabetes Center, Isala Hospital, Zwolle, the Netherlands; Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Mathilde Jalving
- Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
| | - Gijs W D Landman
- Langerhans Medical Research Group, Zwolle, the Netherlands; Department of Internal Medicine, Gelre Hospital, Apeldoorn, the Netherlands
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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: 21] [Impact Index Per Article: 4.2] [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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170
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Garcia A, Pochinda S, Elgaard-Jørgensen PN, Khandelia H, Clarke RJ. Evidence for ATP Interaction with Phosphatidylcholine Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9944-9953. [PMID: 31291108 DOI: 10.1021/acs.langmuir.9b01240] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
ATP is a fundamental intracellular molecule and is thought to diffuse freely throughout the cytosol. Evidence obtained from nucleotide-sensing sarcolemmal ion channels and red blood cells, however, suggest that ATP is compartmentalized or buffered, especially beneath the sarcolemma, but no definitive mechanism for restricted diffusion or potential buffering system has been postulated. In this study, we provide evidence from alterations to membrane dipole potential, membrane conductance, changes in enthalpy of phospholipid phase transition, and from free energy calculations that ATP associates with phospholipid bilayers. Furthermore, all-atom molecular dynamics simulations show that ATP can form aggregates in the aqueous phase at high concentrations. ATP interaction with membranes provides a new model to understand the diffusion of ATP through the cell. Coupled with previous reports of diffusion restriction in the subsarcolemmal space, these findings support the existence of compartmentalized or buffered pools of ATP.
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Affiliation(s)
- Alvaro Garcia
- School of Life Sciences , University of Technology Sydney , Ultimo , NSW 2007 , Australia
| | - Simon Pochinda
- PHYLIFE: Physical Life Sciences at SDU, Department of Physics, Chemistry and Pharmacy and MEMPHYS: Center for Biomembrane Physics , University of Southern Denmark , DK-5230 Odense M , Denmark
| | - Paninnguaq N Elgaard-Jørgensen
- PHYLIFE: Physical Life Sciences at SDU, Department of Physics, Chemistry and Pharmacy and MEMPHYS: Center for Biomembrane Physics , University of Southern Denmark , DK-5230 Odense M , Denmark
| | - Himanshu Khandelia
- PHYLIFE: Physical Life Sciences at SDU, Department of Physics, Chemistry and Pharmacy and MEMPHYS: Center for Biomembrane Physics , University of Southern Denmark , DK-5230 Odense M , Denmark
| | - Ronald J Clarke
- School of Chemistry , University of Sydney , Sydney , NSW 2006 , Australia
- The University of Sydney Nano Institute , Sydney , NSW 2006 , Australia
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171
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Martin GM, Sung MW, Yang Z, Innes LM, Kandasamy B, David LL, Yoshioka C, Shyng SL. Mechanism of pharmacochaperoning in a mammalian K ATP channel revealed by cryo-EM. eLife 2019; 8:46417. [PMID: 31343405 PMCID: PMC6699824 DOI: 10.7554/elife.46417] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/22/2019] [Indexed: 01/03/2023] Open
Abstract
ATP-sensitive potassium (KATP) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic β-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse KATP inhibitors are known to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of a mammalian KATP channel bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. We found all three drugs bind within a common pocket in SUR1. Further, we found the N-terminus of Kir6.2 inserted within the central cavity of the SUR1 ABC core, adjacent the drug binding pocket. The findings reveal a common mechanism by which diverse compounds stabilize the Kir6.2 N-terminus within SUR1’s ABC core, allowing it to act as a firm ‘handle’ for the assembly of metastable mutant SUR1-Kir6.2 complexes.
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Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Min Woo Sung
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Zhongying Yang
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Laura M Innes
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Balamurugan Kandasamy
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Larry L David
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, United States
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
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172
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Masi A, Narducci R, Mannaioni G. Harnessing ionic mechanisms to achieve disease modification in neurodegenerative disorders. Pharmacol Res 2019; 147:104343. [PMID: 31279830 DOI: 10.1016/j.phrs.2019.104343] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 06/19/2019] [Accepted: 07/03/2019] [Indexed: 12/12/2022]
Abstract
Progressive neuronal death is the key pathogenic event leading to clinical symptoms in neurodegenerative disorders (NDDs). Neuroprotective treatments are virtually unavailable, partly because of the marked internal heterogeneity of the mechanisms underlying pathology. Targeted neuroprotection would require deep mechanistic knowledge across the entire aetiological spectrum of each NDD and the development of tailored treatments. Although ideal, this strategy appears challenging, as it would require a degree of characterization of both the disease and the patient that is currently unavailable. The alternate strategy is to search for commonalities across molecularly distinct NDD forms and exploit these for the development of drugs with broad-spectrum efficacy. In this view, mounting evidence points to ionic mechanisms (IMs) as targets with potential therapeutic efficacy across distinct NDD subtypes. The scope of this review is to present clinical and preclinical evidence supporting the link between disruption of IMs and neuronal death in specific NDDs and to critically revise past and ongoing attempts of harnessing IMs for the development of neuroprotective treatments.
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Affiliation(s)
- A Masi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, Florence, Italy; School of Pharmacy, University of Camerino, Camerino, Italy.
| | - R Narducci
- Italian Institute of Technology (IIT), Department of Neuroscience and Brain Technologies, Genova, Italy
| | - G Mannaioni
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, Florence, Italy; Toxicology Unit, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy
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173
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Balamurugan K, Kavitha B, Yang Z, Mohan V, Radha V, Shyng SL. Functional characterization of activating mutations in the sulfonylurea receptor 1 (ABCC8) causing neonatal diabetes mellitus in Asian Indian children. Pediatr Diabetes 2019; 20:397-407. [PMID: 30861254 DOI: 10.1111/pedi.12843] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 01/28/2019] [Accepted: 02/24/2019] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Gain-of-function of ATP-sensitive K+ (KATP ) channels because of mutations in the genes encoding SUR1 (ABCC8) or Kir6.2 (KCNJ11) is a major cause of neonatal diabetes mellitus (NDM). Our aim is to determine molecular defects in KATP channels caused by ABCC8 mutations in Asian Indian children with NDM by in vitro functional studies. METHODS Wild-type (WT; NM_000352.4) or mutant sulfonylurea receptor 1 (SUR1) and Kir6.2 were co-expressed in COSm6 cells. Biogenesis efficiency and surface expression of mutant channels were assessed by immunoblotting and immunostaining. The response of mutant channels to cytoplasmic ATP and ADP was assessed by inside-out patch-clamp recordings. The response of mutant channels to known KATP inhibitors in intact cells were determined by 86 Rb efflux assays. RESULTS Five SUR1 missense mutations, D212Y, P254S, R653Q, R992C, and Q1224H, were studied and showed increased activity in MgATP/MgADP. Two of the mutants, D212Y and P254S, also showed reduced response to ATP4- inhibition, as well as markedly reduced surface expression. Moreover, all five mutants were inhibited by the KATP channel inhibitors glibenclamide and carbamazepine. CONCLUSIONS The study shows the mechanisms by which five SUR1 mutations identified in Asian Indian NDM patients affect KATP channel function to cause the disease. The reduced ATP4- sensitivity caused by the D212Y and P254S mutations in the L0 of SUR1 provides novel insight into the role of L0 in channel inhibition by ATP. The results also explain why sulfonylurea therapy is effective in two patients and inform how it should be effective for the other three patients.
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Affiliation(s)
- Kandasamy Balamurugan
- Department of Molecular Genetics, Madras Diabetes Research Foundation, ICMR Advanced Centre for Genomics of Type 2 Diabetes and Dr. Mohan's Diabetes Specialties Centre, WHO Collaborating Centre for Non-Communicable Diseases Prevention & Control, IDF Centre of Education, Chennai, India
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon
| | - Babu Kavitha
- Department of Molecular Genetics, Madras Diabetes Research Foundation, ICMR Advanced Centre for Genomics of Type 2 Diabetes and Dr. Mohan's Diabetes Specialties Centre, WHO Collaborating Centre for Non-Communicable Diseases Prevention & Control, IDF Centre of Education, Chennai, India
| | - Zhongying Yang
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon
| | - Viswanathan Mohan
- Department of Molecular Genetics, Madras Diabetes Research Foundation, ICMR Advanced Centre for Genomics of Type 2 Diabetes and Dr. Mohan's Diabetes Specialties Centre, WHO Collaborating Centre for Non-Communicable Diseases Prevention & Control, IDF Centre of Education, Chennai, India
| | - Venkatesan Radha
- Department of Molecular Genetics, Madras Diabetes Research Foundation, ICMR Advanced Centre for Genomics of Type 2 Diabetes and Dr. Mohan's Diabetes Specialties Centre, WHO Collaborating Centre for Non-Communicable Diseases Prevention & Control, IDF Centre of Education, Chennai, India
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon
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174
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Leptin-induced Trafficking of K ATP Channels: A Mechanism to Regulate Pancreatic β-cell Excitability and Insulin Secretion. Int J Mol Sci 2019; 20:ijms20112660. [PMID: 31151172 PMCID: PMC6600549 DOI: 10.3390/ijms20112660] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 05/25/2019] [Accepted: 05/27/2019] [Indexed: 11/17/2022] Open
Abstract
The adipocyte hormone leptin was first recognized for its actions in the central nervous system to regulate energy homeostasis but has since been shown to have direct actions on peripheral tissues. In pancreatic β-cells leptin suppresses insulin secretion by increasing KATP channel conductance, which causes membrane hyperpolarization and renders β-cells electrically silent. However, the mechanism by which leptin increases KATP channel conductance had remained unresolved for many years following the initial observation. Recent studies have revealed that leptin increases surface abundance of KATP channels by promoting channel trafficking to the β-cell membrane. Thus, KATP channel trafficking regulation has emerged as a mechanism by which leptin increases KATP channel conductance to regulate β-cell electrical activity and insulin secretion. This review will discuss the leptin signaling pathway that underlies KATP channel trafficking regulation in β-cells.
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175
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McClenaghan C, Woo KV, Nichols CG. Pulmonary Hypertension and ATP-Sensitive Potassium Channels. Hypertension 2019; 74:14-22. [PMID: 31132951 DOI: 10.1161/hypertensionaha.119.12992] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Conor McClenaghan
- From the Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO (C.M., C.G.N.)
| | - Kel Vin Woo
- Department of Pediatrics, Division of Cardiology, Washington University School of Medicine, St Louis, MO (K.V.W.)
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO (C.M., C.G.N.)
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176
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Singh BL, Chen L, Cai H, Shi H, Wang Y, Yu C, Chen X, Han X, Cai X. Activation of adenosine A2a receptor accelerates and A2a receptor antagonist reduces intermittent hypoxia induced PC12 cell injury via PKC-KATP pathway. Brain Res Bull 2019; 150:118-126. [PMID: 31129168 DOI: 10.1016/j.brainresbull.2019.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/19/2019] [Accepted: 05/21/2019] [Indexed: 02/07/2023]
Abstract
Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with multiple system diseases. Neurocognitive dysfunction resulting from central nervous system complications has been reported, especially in children with OSAHS. Chronic intermittent hypoxia is accepted to be the major pathophysiological mechanism of OSAHS. Adenosine plays an important role in cellular function via interactions with its receptors. A2a receptor has been recognized as a factor involved in neuroprotection. However, the role of adenosine A2a receptor in intermittent hypoxia induced cellular injury is not completely understood. In this study, we aim to investigate the underlying mechanisms of A2a receptor mediated cellular damage caused by intermittent hypoxia in PC12 cells. We found that activated A2a receptor by CGS21680 decreased cellular viability, increased PKC as well as ATP-sensitive potassium channel (KATP) subunits expression Kir6.2 and SUR1. Inhibition of A2a receptor by SCH58261 increased cellular viability, suppressed PKC and SUR1 expression level, ultimately showing a protective role in PC12 cells. Moreover, we observed that CHE, which is an antagonist of PKC, downregulated Kir6.2 and SUR1 expression and increased cellular viability. Additionally, we found that A2a receptor activation induced cell injury was associated with increased Cleaved-Caspase 3 expression, which can be decreased by inhibition of A2a receptor or PKC. In conclusion, our findings indicate that A2a receptor induced KATP expression by PKC activation and plays a role in accelerating PC12 cells injury induced by intermittent hypoxia exposure via A2a-PKC-KATP signal pathway mediated apoptosis.
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Affiliation(s)
- Brett Lyndall Singh
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Liya Chen
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Huilin Cai
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Hua Shi
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Yueyuan Wang
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Chenyi Yu
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China
| | - Xu Chen
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China
| | - Xinru Han
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China
| | - Xiaohong Cai
- Department of Pediatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, 109 Xueyuan Western Road, Wenzhou, Zhejiang, 325027, PR China; The Second School Of Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, PR China.
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177
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Sarmiento BE, Santos Menezes LF, Schwartz EF. Insulin Release Mechanism Modulated by Toxins Isolated from Animal Venoms: From Basic Research to Drug Development Prospects. Molecules 2019; 24:E1846. [PMID: 31091684 PMCID: PMC6571724 DOI: 10.3390/molecules24101846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 12/12/2022] Open
Abstract
Venom from mammals, amphibians, snakes, arachnids, sea anemones and insects provides diverse sources of peptides with different potential medical applications. Several of these peptides have already been converted into drugs and some are still in the clinical phase. Diabetes type 2 is one of the diseases with the highest mortality rate worldwide, requiring specific attention. Diverse drugs are available (e.g., Sulfonylureas) for effective treatment, but with several adverse secondary effects, most of them related to the low specificity of these compounds to the target. In this context, the search for specific and high-affinity compounds for the management of this metabolic disease is growing. Toxins isolated from animal venom have high specificity and affinity for different molecular targets, of which the most important are ion channels. This review will present an overview about the electrical activity of the ion channels present in pancreatic β cells that are involved in the insulin secretion process, in addition to the diversity of peptides that can interact and modulate the electrical activity of pancreatic β cells. The importance of prospecting bioactive peptides for therapeutic use is also reinforced.
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Affiliation(s)
- Beatriz Elena Sarmiento
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Luis Felipe Santos Menezes
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Elisabeth F Schwartz
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
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178
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Edling CE, Fazmin IT, Chadda KR, Ahmad S, Valli H, Huang CLH, Jeevaratnam K. Atrial Transcriptional Profiles of Molecular Targets Mediating Electrophysiological Function in Aging and Pgc-1β Deficient Murine Hearts. Front Physiol 2019; 10:497. [PMID: 31068841 PMCID: PMC6491872 DOI: 10.3389/fphys.2019.00497] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 04/08/2019] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Deficiencies in the transcriptional co-activator, peroxisome proliferative activated receptor, gamma, coactivator-1β are implicated in deficient mitochondrial function. The latter accompanies clinical conditions including aging, physical inactivity, obesity, and diabetes. Recent electrophysiological studies reported that Pgc-1β-/- mice recapitulate clinical age-dependent atrial pro-arrhythmic phenotypes. They implicated impaired chronotropic responses to adrenergic challenge, compromised action potential (AP) generation and conduction despite normal AP recovery timecourses and background resting potentials, altered intracellular Ca2+ homeostasis, and fibrotic change in the observed arrhythmogenicity. OBJECTIVE We explored the extent to which these age-dependent physiological changes correlated with alterations in gene transcription in murine Pgc-1β-/- atria. METHODS AND RESULTS RNA isolated from murine atrial tissue samples from young (12-16 weeks) and aged (>52 weeks of age), wild type (WT) and Pgc-1β-/- mice were studied by pre-probed quantitative PCR array cards. We examined genes encoding sixty ion channels and other strategic atrial electrophysiological proteins. Pgc-1β-/- genotype independently reduced gene transcription underlying Na+-K+-ATPase, sarcoplasmic reticular Ca2+-ATPase, background K+ channel and cholinergic receptor function. Age independently decreased Na+-K+-ATPase and fibrotic markers. Both factors interacted to alter Hcn4 channel activity underlying atrial automaticity. However, neither factor, whether independently or interactively, affected transcription of cardiac Na+, voltage-dependent K+ channels, surface or intracellular Ca2+ channels. Nor were gap junction channels, β-adrenergic receptors or transforming growth factor-β affected. CONCLUSION These findings limit the possible roles of gene transcriptional changes in previously reported age-dependent pro-arrhythmic electrophysiologial changes observed in Pgc-1β-/- atria to an altered Ca2+-ATPase (Atp2a2) expression. This directly parallels previously reported arrhythmic mechanism associated with p21-activated kinase type 1 deficiency. This could add to contributions from the direct physiological outcomes of mitochondrial dysfunction, whether through reactive oxygen species (ROS) production or altered Ca2+ homeostasis.
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Affiliation(s)
- Charlotte E. Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Ibrahim T. Fazmin
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Karan R. Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom,School of Medicine, Perdana University-Royal College of Surgeons in Ireland, Selangor, Malaysia,*Correspondence: Kamalan Jeevaratnam,
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179
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Wang Y, Hall LM, Kujawa M, Li H, Zhang X, O'Meara M, Ichinose T, Wang JM. Methylglyoxal triggers human aortic endothelial cell dysfunction via modulation of the K ATP/MAPK pathway. Am J Physiol Cell Physiol 2019; 317:C68-C81. [PMID: 30995106 DOI: 10.1152/ajpcell.00117.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Endothelial dysfunction is a key risk factor in diabetes-related multiorgan damage. Methylglyoxal (MGO), a highly reactive dicarbonyl generated primarily as a by-product of glycolysis, is increased in both type 1 and type 2 diabetic patients. MGO can rapidly bind with proteins, nucleic acids, and lipids, resulting in structural and functional changes. MGO can also form advanced glycation end products (AGEs). How MGO causes endothelial cell dysfunction, however, is not clear. Human aortic endothelial cells (HAECs) from healthy (H-HAECs) and type 2 diabetic (D-HAECs) donors were cultured in endothelial growth medium (EGM-2). D-HAECs demonstrated impaired network formation (on Matrigel) and proliferation (MTT assay), as well as increased apoptosis (caspase-3/7 activity and TUNEL staining), compared with H-HAECs. High glucose (25 mM) or AGEs (200 ng/ml) did not induce such immediate, detrimental effects as MGO (10 µM). H-HAECs were treated with MGO (10 µM) for 24 h with or without the ATP-sensitive potassium (KATP) channel antagonist glibenclamide (1 µM). MGO significantly impaired H-HAEC network formation and proliferation and induced cell apoptosis, which was reversed by glibenclamide. Furthermore, siRNA against the KATP channel protein Kir6.1 significantly inhibited endothelial cell function at basal status but rescued impaired endothelial cell function upon MGO exposure. Meanwhile, activation of MAPK pathways p38 kinase, c-Jun NH2-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) (determined by Western blot analyses of their phosphorylated forms, p-JNK, p-p38, and p-ERK) in D-HAECs were significantly enhanced compared with those in H-HAECs. MGO exposure enhanced the activation of all three MAPK pathways in H-HAECs, whereas glibenclamide reversed the activation of p-stress-activated protein kinase/JNK induced by MGO. Glyoxalase-1 (GLO1) is the endogenous MGO-detoxifying enzyme. In healthy mice that received an inhibitor of GLO1, MGO deposition in aortic wall was enhanced and endothelial cell sprouting from isolated aortic segment was significantly inhibited. Our data suggest that MGO triggers endothelial cell dysfunction by activating the JNK/p38 MAPK pathway. This effect arises partly through activation of KATP channels. By understanding how MGO induces endothelial dysfunction, our study may provide useful information for developing MGO-targeted interventions to treat vascular disorders in diabetes.
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Affiliation(s)
- Yihan Wang
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan
| | - Leo M Hall
- Department of Ophthalmology, Visual and Anatomical Sciences, School of Medicine, Wayne State University , Detroit, Michigan
| | - Marisa Kujawa
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan
| | - Hainan Li
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan
| | - Xiang Zhang
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan
| | - Megan O'Meara
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan
| | - Tomomi Ichinose
- Department of Ophthalmology, Visual and Anatomical Sciences, School of Medicine, Wayne State University , Detroit, Michigan
| | - Jie-Mei Wang
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University , Detroit, Michigan.,Centers for Molecular Medicine and Genetics, Wayne State University , Detroit, Michigan.,Cardiovascular Research Institute, Wayne State University, Detroit, Michigan
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180
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Ageing in Pgc-1β-/- mice modelling mitochondrial dysfunction induces differential expression of a range of genes regulating ventricular electrophysiology. Biosci Rep 2019; 39:BSR20190127. [PMID: 30914453 PMCID: PMC6470410 DOI: 10.1042/bsr20190127] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/28/2019] [Accepted: 03/15/2019] [Indexed: 02/06/2023] Open
Abstract
Mice deficient in mitochondrial promoter peroxisome proliferator activated receptor-γ co-activator-1β (Pgc-1β−/−) is a valuable model for metabolic diseases and has been found to present with several pathologies including ventricular arrhythmia. In the present study, our aim was to shed light on the molecular mechanisms behind the observed arrhythmic substrate by studying how the expression of selected genes critical for cardiac function differs in wild-type (WT) compared with Pgc-1β knockout mice and young compared with aged mice. We found that a clear majority of genes are down-regulated in the Pgc-1β−/− ventricular tissue compared with the WT. Although most individual genes are not significantly differentially expressed, a pattern is apparent when the genes are grouped according to their functional properties. Genes encoding proteins relating to ATPase activity, potassium ion channels relating to repolarisation and resting membrane potential, and genes encoding proteins in the cAMP pathway are found to be significantly down-regulated in the Pgc-1β deficient mice. On the contrary, the pacemaker channel genes Hcn3 and Hcn4 are up-regulated in subsets of the Pgc-1β deficient tissue. Furthermore, we found that with age, especially in the Pgc-1β−/− genotype, most genes are up-regulated including genes relating to the resting membrane potential, calcium homeostasis, the cAMP pathway, and most of the tested adrenoceptors. In conclusion, we here demonstrate how a complex pattern of many modest changes at gene level may explain major functional differences of the action potential related to ageing and mitochondrial dysfunction.
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181
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De Bernardis Murat C, Leão RM. A voltage-dependent depolarization induced by low external glucose in neurons of the nucleus of the tractus solitarius: interaction with K ATP channels. J Physiol 2019; 597:2515-2532. [PMID: 30927460 DOI: 10.1113/jp277729] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS Neurons from the brainstem nucleus of the tractus solitarius (NTS) participate in the counter-regulatory mechanisms in response to hypoglycaemia. ATP-sensitive potassium (KATP ) channels are expressed in NTS neurons, and are partially open at rest in normoglycaemic 5 mM glucose. In normoglycaemic conditions, most NTS neurons depolarize in response to low external glucose (0.5 mM), via a voltage-dependent mechanism. Conversely, most NTS neurons incubated in hyperglycaemic 10 mM glucose do not respond to low glucose due to a more positive resting membrane potential caused by the closure of KATP channels following increased intracellular metabolic ATP. Our findings show that in hyperglycaemic conditions, NTS neurons failed to sense rapid changes in external glucose, which could be related to hypoglycaemia-associated autonomic failure. ABSTRACT The nucleus of the tractus solitarius (NTS) is an integrative centre for autonomic counter-regulatory responses to hypoglycaemia. KATP channels link the metabolic status of the neuron to its excitability. Here we investigated the influence of KATP channels on the membrane potential of NTS neurons in normo- and hyperglycaemic external glucose concentrations, and after switching to a hypoglycaemic concentration, using in vitro electrophysiological recordings in brainstem slices. We found that in normoglycaemic (5 mM) glucose, tolbutamide, a KATP channel antagonist, depolarized the membrane of most neurons, and this effect was observed in more hyperpolarized neurons. All neurons hyperpolarized after pharmacological activation of KATP channels. Most NTS neurons depolarized in the presence of low glucose (0.5 mM), and this effect was only seen in hyperpolarized neurons. The effect of glucose was caused by a cationic current with a reversal potential around -50 mV. In the presence of hyperglycaemic glucose (10 mM), neurons were more depolarized, and fewer neurons responded to KATP blockage. Application of 0.5 mM glucose solution to these neurons depolarized the membrane only in more hyperpolarized neurons. We conclude that NTS neurons present with KATP channels open at rest in normoglycaemic conditions, and their membrane potential is affected by extracellular glucose. Moreover, NTS neurons depolarize the membrane in response to the application of a low glucose solution, but this effect is occluded by membrane depolarization triggered by KATP blockage. Our data suggest a homeostatic regulation of the membrane potential by external glucose, and a possible mechanism related to the hypoglycaemia-associated autonomic failure.
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Affiliation(s)
- Cahuê De Bernardis Murat
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Ricardo Mauricio Leão
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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Pirotte B, Florence X, Goffin E, Lebrun P. 2,2-Dimethyl-3,4-dihydro-2 H-1,4-benzoxazines as isosteres of 2,2-dimethylchromans acting as inhibitors of insulin release and vascular smooth muscle relaxants. MEDCHEMCOMM 2019; 10:431-438. [PMID: 31015906 DOI: 10.1039/c8md00593a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 02/01/2019] [Indexed: 11/21/2022]
Abstract
The present study describes the synthesis and biological evaluation of 4-phenylureido/thioureido-substituted 2,2-dimethyl-3,4-dihydro-2H-1,4-benzoxazines as isosteres of corresponding 2,2-dimethylchromans reported to be pancreatic β-cell KATP channel openers. The benzoxazines were found to be less active as inhibitors of the glucose-induced insulin release than their corresponding chromans, while the myorelaxant activity of some 4-arylureido-substituted benzoxazines was more pronounced than that exhibited by their chroman counterparts. The myorelaxant activity of the most potent benzoxazine 8e was further characterized on rat aortic rings precontracted by 30 mM KCl in the presence of glibenclamide (10 μM) or precontracted by 80 mM extracellular KCl. Our findings indicate that, on vascular smooth muscle cells, the benzoxazine 8e mainly behaved as a calcium entry blocker.
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Affiliation(s)
- Bernard Pirotte
- Laboratoire de Chimie Pharmaceutique , Center for Interdisciplinary Research on Medicines (CIRM) , Université de Liège , Quartier Hôpital , Avenue Hippocrate 15 , B-4000 Liège , Belgium .
| | - Xavier Florence
- Laboratoire de Chimie Pharmaceutique , Center for Interdisciplinary Research on Medicines (CIRM) , Université de Liège , Quartier Hôpital , Avenue Hippocrate 15 , B-4000 Liège , Belgium . .,Laboratoire de Physiologie et Pharmacologie , Université Libre de Bruxelles , Faculté de Médecine , 808 Route de Lennik , B-1070 Bruxelles , Belgium
| | - Eric Goffin
- Laboratoire de Chimie Pharmaceutique , Center for Interdisciplinary Research on Medicines (CIRM) , Université de Liège , Quartier Hôpital , Avenue Hippocrate 15 , B-4000 Liège , Belgium .
| | - Philippe Lebrun
- Laboratoire de Physiologie et Pharmacologie , Université Libre de Bruxelles , Faculté de Médecine , 808 Route de Lennik , B-1070 Bruxelles , Belgium
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183
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Inward rectifier potassium (Kir) channels mediate salivary gland function and blood feeding in the lone star tick, Amblyomma americanum. PLoS Negl Trop Dis 2019; 13:e0007153. [PMID: 30730880 PMCID: PMC6382211 DOI: 10.1371/journal.pntd.0007153] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 02/20/2019] [Accepted: 01/13/2019] [Indexed: 02/06/2023] Open
Abstract
Background Tick feeding causes extreme morbidity and mortality to humans through transmission of pathogens and causes severe economic losses to the agricultural industry by reducing livestock yield. Salivary gland secretions are essential for tick feeding and thus, reducing or preventing saliva secretions into the vertebrate host is likely to reduce feeding and hinder pathogen life cycles. Unfortunately, the membrane physiology of tick salivary glands is underexplored and this gap in knowledge limits the development of novel therapeutics for inducing cessation of tick feeding. Methodology We studied the influence of inward rectifier potassium (Kir) channel subtypes to the functional capacity of the isolated tick salivary gland through the use of a modified Ramsay assay. The secreted saliva was subsequently used for quantification of the elemental composition of the secreted saliva after the glands were exposed to K+ channel modulators as a measure of osmoregulatory capacity. Lastly, changes to blood feeding behavior and mortality were measured with the use of a membrane feeding system. Principal findings In this study, we characterized the fundamental role of Kir channel subtypes in tick salivary gland function and provide evidence that pharmacological inhibition of these ion channels reduces the secretory activity of the Amblyomma americanum salivary gland. The reduced secretory capacity of the salivary gland was directly correlated with a dramatic reduction of blood ingestion during feeding. Further, exposure to small-molecule modulators of Kir channel subtypes induced mortality to ticks that is likely resultant from an altered osmoregulatory capacity. Conclusions Our data contribute to understanding of tick salivary gland function and could guide future campaigns aiming to develop chemical or reverse vaccinology technologies to reduce the worldwide burden of tick feeding and tick-vectored pathogens. Tick feeding results in negative health and economic consequences worldwide and there has been continued interest in the development of products with novel mechanisms of action for control of tick populations. Kir channels have been shown to be a significant ion conductance pathway in arthropods and are critical for proper functioning of multiple biological processes. Previous work on insect Kir channels has focused on their physiological roles in renal system of mosquitoes and the data suggest that these channels represent a viable pathway to induce renal failure that leads to mortality. Based on the functional and cellular similarities of arthropod salivary glands and Malpighian tubules, we hypothesized that Kir channels constitute a critical conductance pathway within arthropod salivary glands and inhibition of this pathway will preclude feeding. Data presented in this study show that pharmacological modulators of Kir channels elicited a significant reduction in the fluid and ion secretory activity of tick salivary glands that resulted in reduced feeding, altered osmoregulation, and lead to mortality. These data could guide the future development of novel acaricides, RNAi, or genetically modified ticks to mitigate health and economic damages resulting from their feeding. Further, these data indicate a conserved function of Kir channels within multiple tissues of taxonomically diverse organisms, such as ticks and humans.
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184
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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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185
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Castro L, Noelia M, Vidal-Jorge M, Sánchez-Ortiz D, Gándara D, Martínez-Saez E, Cicuéndez M, Poca MA, Simard JM, Sahuquillo J. Kir6.2, the Pore-Forming Subunit of ATP-Sensitive K + Channels, Is Overexpressed in Human Posttraumatic Brain Contusions. J Neurotrauma 2019; 36:165-175. [PMID: 29737232 PMCID: PMC7872003 DOI: 10.1089/neu.2017.5619] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Brain contusions (BCs) are one of the most frequent lesions in patients with moderate and severe traumatic brain injury (TBI). BCs increase their volume due to peri-lesional edema formation and/or hemorrhagic transformation. This may have deleterious consequences and its mechanisms are still poorly understood. We previously identified de novo upregulation sulfonylurea receptor (SUR) 1, the regulatory subunit of adenosine triphosphate (ATP)-sensitive potassium (KATP) channels and other channels, in human BCs. Our aim here was to study the expression of the pore-forming subunit of KATP, Kir6.2, in human BCs, and identify its localization in different cell types. Protein levels of Kir6.2 were detected by western blot (WB) from 33 contusion specimens obtained from 32 TBI patients aged 14-74 years. The evaluation of Kir6.2 expression in different cell types was performed by immunofluorescence in 29 contusion samples obtained from 28 patients with a median age of 42 years. Control samples were obtained from limited brain resections performed to access extra-axial skull base tumors or intraventricular lesions. Contusion specimens showed an increase of Kir6.2 expression in comparison with controls. Regarding cellular location of Kir6.2, there was no expression of this channel subunit in blood vessels, either in control samples or in contusions. The expression of Kir6.2 in neurons and microglia was also analyzed, but the observed differences were not statistically significant. However, a significant increase of Kir6.2 was found in glial fibrillary acidic protein (GFAP)-positive cells in contusion specimens. Our data suggest that further research on SUR1-regulated ionic channels may lead to a better understanding of key mechanisms involved in the pathogenesis of BCs, and may identify novel targeted therapeutic strategies.
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Affiliation(s)
- Lidia Castro
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Montoya Noelia
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Marian Vidal-Jorge
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - David Sánchez-Ortiz
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Darío Gándara
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
- Department of Neurosurgery, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Elena Martínez-Saez
- Department of Pathology, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Marta Cicuéndez
- Department of Neurosurgery, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Maria-Antonia Poca
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
- Department of Neurosurgery, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - J. Marc Simard
- Departments of Neurosurgery, Physiology, and Pathology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Juan Sahuquillo
- Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
- Department of Neurosurgery, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
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186
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Abstract
The key molecular events that provoke Parkinson's disease (PD) are not fully understood. Iron deposit was found in the substantia nigra pars compacta (SNpc) of PD patients and animal models, where dopaminergic neurons degeneration occurred selectively. The mechanisms involved in disturbed iron metabolism remain unknown, however, considerable evidence indicates that iron transporters dysregulation, activation of L-type voltage-gated calcium channel (LTCC) and ATP-sensitive potassium (KATP) channels, as well as N-methyl-D-aspartate (NMDA) receptors (NMDARs) contribute to this process. There is emerging evidence on the structural links and functional modulations between iron and α-synuclein, and the key player in PD which aggregates in Lewy bodies. Iron is believed to modulate α-synuclein synthesis, post-translational modification, and aggregation. Furthermore, glia, especially activated astroglia and microglia, are involved in iron deposit in PD. Glial contributions were largely dependent on the factors they released, e.g., neurotrophic factors, pro-inflammatory factors, lactoferrin, and those undetermined. Therefore, iron chelation using iron chelators, the extracts from many natural foods with iron chelating properties, may be an effective therapy for prevention and treatment of the disease.
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187
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Emfinger CH, Yan Z, Welscher A, Hung P, McAllister W, Hruz PW, Nichols CG, Remedi MS. Contribution of systemic inflammation to permanence of K ATP-induced neonatal diabetes in mice. Am J Physiol Endocrinol Metab 2018; 315:E1121-E1132. [PMID: 30226997 PMCID: PMC6336961 DOI: 10.1152/ajpendo.00137.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Gain-of-function (GOF) mutations in the ATP-sensitive potassium (KATP) channels cause neonatal diabetes. Despite the well-established genetic root of the disease, pathways modulating disease severity and treatment effectiveness remain poorly understood. Patient phenotypes can vary from severe diabetes to remission, even in individuals with the same mutation and within the same family, suggesting that subtle modifiers can influence disease outcome. We have tested the underlying mechanism of transient vs. permanent neonatal diabetes in KATP-GOF mice treated for 14 days with glibenclamide. Some KATP-GOF mice show remission of diabetes and enhanced insulin sensitivity long after diabetes treatment has ended, while others maintain severe insulin-resistance. However, insulin sensitivity is not different between the two groups before or during diabetes induction, suggesting that improved sensitivity is a consequence, rather than the cause of, remission, implicating other factors modulating glucose early in diabetes progression. Leptin, glucagon, insulin, and glucagon-like peptide-1 are not different between remitters and nonremitters. However, liver glucose production is significantly reduced before transgene induction in remitter, relative to nonremitter and nontreated, mice. Surprisingly, while subsequent remitter animals exhibited normal serum cytokines, nonremitter mice showed increased cytokines, which paralleled the divergence in blood glucose. Together, these results suggest that systemic inflammation may play a role in the remitting versus non-remitting outcome. Supporting this conclusion, treatment with the anti-inflammatory meloxicam significantly increased the fraction of remitting animals. Beyond neonatal diabetes, the potential for inflammation and glucose production to exacerbate other forms of diabetes from a compensated state to a glucotoxic state should be considered.
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Affiliation(s)
- Christopher H Emfinger
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
| | - Zihan Yan
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Alecia Welscher
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Peter Hung
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
| | - William McAllister
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Paul W Hruz
- Department of Pediatrics, Washington University in St. Louis , St. Louis, Missouri
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
| | - Maria S Remedi
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
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188
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A BAD Insight into a Molecular Mechanism of the Ketogenic Diet? Epilepsy Curr 2018; 18:332-333. [PMID: 30464738 DOI: 10.5698/1535-7597.18.5.332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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189
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Huang Z, Xiao K. Electrophysiological Mechanism of Peripheral Hormones and Nutrients Regulating Energy Homeostasis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1090:183-198. [PMID: 30390291 DOI: 10.1007/978-981-13-1286-1_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In organism, energy homeostasis is a biological process that involves the coordinated homeostatic regulation of energy intake (food intake) and energy expenditure. The human brain, particularly the hypothalamic proopiomelanocortin (POMC)- and agouti-related protein/neuropeptide Y (AgRP/NPY)-expressing neurons in the arcuate nucleus, plays an essential role in regulating energy homeostasis. The regulation process is mainly dependent upon peripheral hormones such as leptin and insulin, as well as nutrients such as glucose, amino acids, and fatty acids. Although many studies have attempted to illustrate the exact mechanisms of glucose and hormones action on these neurons, we still cannot clearly see the full picture of this regulation action. Therefore, in this review we will mainly discuss those established theories and recent progresses in this area, demonstrating the possible physiological mechanism by which glucose, leptin, and insulin affect neuronal excitability of POMC and AgRP neurons. In addition, we will also focus on some important ion channels which are expressed by POMC and AgRP neurons, such as KATP channels and TRPC channels, and explain how these channels are regulated by peripheral hormones and nutrients and thus regulate energy homeostasis.
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Affiliation(s)
- Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China.
| | - Kuo Xiao
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
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190
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Chadda KR, Edling CE, Valli H, Ahmad S, Huang CLH, Jeevaratnam K. Gene and Protein Expression Profile of Selected Molecular Targets Mediating Electrophysiological Function in Pgc-1α Deficient Murine Atria. Int J Mol Sci 2018; 19:ijms19113450. [PMID: 30400228 PMCID: PMC6274828 DOI: 10.3390/ijms19113450] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 10/25/2018] [Accepted: 10/29/2018] [Indexed: 12/27/2022] Open
Abstract
Increases in the prevalence of obesity, insulin resistance, and metabolic syndrome has led to the increase of atrial fibrillation (AF) cases in the developed world. These AF risk factors are associated with mitochondrial dysfunction, previously modelled using peroxisome proliferator activated receptor-γ (PPARγ) coactivator-1 (Pgc-1)-deficient murine cardiac models. We explored gene and protein expression profiles of selected molecular targets related to electrophysiological function in murine Pgc-1α−/− atria. qPCR analysis surveyed genes related to Na+-K+-ATPase, K+ conductance, hyperpolarisation-activated cyclic nucleotide-gated (Hcn), Na+ channels, Ca2+ channels, and indicators for adrenergic and cholinergic receptor modulation. Western blot analysis for molecular targets specific to conduction velocity (Nav1.5 channel and gap junctions) was performed. Transcription profiles revealed downregulation of molecules related to Na+-K+-ATPase transport, Hcn-dependent pacemaker function, Na+ channel-dependent action potential activation and propagation, Ca2+ current generation, calsequestrin-2 dependent Ca2+ homeostasis, and adrenergic α1D dependent protection from hypertrophic change. Nav1.5 channel protein expression but not gap junction expression was reduced in Pgc-1α−/− atria compared to WT. Nav1.5 reduction reflects corresponding reduction in its gene expression profile. These changes, as well as the underlying Pgc-1α−/− alteration, suggest potential pharmacological targets directed towards either upstream PGC-1 signalling mechanisms or downstream ion channel changes.
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Affiliation(s)
- Karan R Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
| | - Christopher L-H Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
- Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge CB2 1QW, UK.
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, UK.
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
- School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang 43400, Malaysia.
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191
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Tessadori F, Roessler HI, Savelberg SMC, Chocron S, Kamel SM, Duran KJ, van Haelst MM, van Haaften G, Bakkers J. Effective CRISPR/Cas9-based nucleotide editing in zebrafish to model human genetic cardiovascular disorders. Dis Model Mech 2018; 11:11/10/dmm035469. [PMID: 30355756 PMCID: PMC6215435 DOI: 10.1242/dmm.035469] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/31/2018] [Indexed: 12/24/2022] Open
Abstract
The zebrafish (Danio rerio) has become a popular vertebrate model organism to study organ formation and function due to its optical clarity and rapid embryonic development. The use of genetically modified zebrafish has also allowed identification of new putative therapeutic drugs. So far, most studies have relied on broad overexpression of transgenes harboring patient-derived mutations or loss-of-function mutants, which incompletely model the human disease allele in terms of expression levels or cell-type specificity of the endogenous gene of interest. Most human genetically inherited conditions are caused by alleles carrying single nucleotide changes resulting in altered gene function. Introduction of such point mutations in the zebrafish genome would be a prerequisite to recapitulate human disease but remains challenging to this day. We present an effective approach to introduce small nucleotide changes in the zebrafish genome. We generated four different knock-in lines carrying distinct human cardiovascular-disorder-causing missense mutations in their zebrafish orthologous genes by combining CRISPR/Cas9 with a short template oligonucleotide. Three of these lines carry gain-of-function mutations in genes encoding the pore-forming (Kir6.1, KCNJ8) and regulatory (SUR2, ABCC9) subunits of an ATP-sensitive potassium channel (KATP) linked to Cantú syndrome (CS). Our heterozygous zebrafish knock-in lines display significantly enlarged ventricles with enhanced cardiac output and contractile function, and distinct cerebral vasodilation, demonstrating the causality of the introduced mutations for CS. These results demonstrate that introducing patient alleles in their zebrafish orthologs promises a broad application for modeling human genetic diseases, paving the way for new therapeutic strategies using this model organism.
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Affiliation(s)
- Federico Tessadori
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT Utrecht, the Netherlands
| | - Helen I Roessler
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
| | - Sanne M C Savelberg
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
| | - Sonja Chocron
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT Utrecht, the Netherlands
| | - Sarah M Kamel
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT Utrecht, the Netherlands
| | - Karen J Duran
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
| | - Mieke M van Haelst
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands.,Department of Clinical Genetics, Amsterdam Medical Center, University of Amsterdam, 1105 AZ Amsterdam, the Netherlands.,Department of Clinical Genetics, Free University Medical Center, 1018 HV Amsterdam, the Netherlands
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
| | - Jeroen Bakkers
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT Utrecht, the Netherlands .,Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
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192
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Abstract
Potassium channels that exhibit the property of inward rectification (Kir channels) are present in most cells. Cloning of the first Kir channel genes 25 years ago led to recognition that inward rectification is a consequence of voltage-dependent block by cytoplasmic polyamines, which are also ubiquitously present in animal cells. Upon cellular depolarization, these polycationic metabolites enter the Kir channel pore from the intracellular side, blocking the movement of K+ ions through the channel. As a consequence, high K+ conductance at rest can provide very stable negative resting potentials, but polyamine-mediated blockade at depolarized potentials ensures, for instance, the long plateau phase of the cardiac action potential, an essential feature for a stable cardiac rhythm. Despite much investigation of the polyamine block, where exactly polyamines get to within the Kir channel pore and how the steep voltage dependence arises remain unclear. This Minireview will summarize current understanding of the relevance and molecular mechanisms of polyamine block and offer some ideas to try to help resolve the fundamental issue of the voltage dependence of polyamine block.
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Affiliation(s)
- Colin G Nichols
- From the Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
| | - Sun-Joo Lee
- From the Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
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193
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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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194
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Wang X, Fitts RH. Effects of regular exercise on ventricular myocyte biomechanics and KATP channel function. Am J Physiol Heart Circ Physiol 2018; 315:H885-H896. [DOI: 10.1152/ajpheart.00130.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Exercise training is known to protect the heart from ischemia and improve function during exercise by reducing cardiomyocyte action potential duration (APD) and increasing contractility. The cellular mechanisms involve β-adrenergic regulation and the ATP-sensitive K+ (KATP) channel, but how each alters function of the left ventricle and sex specificity is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to wheel-running (TRN) or sedentary (SED) groups. After 6–8 wk of training, myocytes were isolated from the left ventricle and field stimulated at 1, 2, and 5 Hz. TRN significantly increased cardiomyocyte contractility, the kinetics of the Ca2+ transient, and responsiveness to the adrenergic receptor agonist isoproterenol (ISO), as reflected by an increased sarcomere shortening. Importantly, we demonstrated a TRN-induced upregulation of KATP channels, which was reflected by elevated content, current density, and the channel’s contribution to APD shortening at high activation rates and in the presence of the activator pinacidil. TRN induced increase in KATP current occurred throughout the left ventricle, but channel subunit content showed regional specificity with increases in Kir6.2 in the apex and SUR2A in base regions. In summary, TRN elevated cardiomyocyte cross-bridge kinetics, Ca2+ sensitivity, and the responsiveness of contractile function to β-adrenergic receptor stimulation in both sexes. Importantly, upregulation of the KATP channel accelerates repolarization and shortens APD during stress and exercise. These adaptations have clinical importance, as increased contractility and reduced APD would help protect cardiac output and reduce intracellular Ca2+ overload during stresses such as regional ischemia. NEW & NOTEWORTHY Our results demonstrate that regular exercise significantly increased ventricular myocyte shortening and relaxation velocity and the rate of rise in intracellular Ca2+ transient and enhanced the response of biomechanics and Ca2+ reuptake to β-adrenergic stimulation. Importantly, exercise training upregulated the cardiomyocyte sarcolemma ATP-sensitive K+ channel across the left ventricle in both sexes, as reflected by elevated channel subunit content, current density, and the channel’s contribution to reduced action potential duration at high activation rates.
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Affiliation(s)
- Xinrui Wang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| | - Robert H. Fitts
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
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195
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Bohnen MS, Ma L, Zhu N, Qi H, McClenaghan C, Gonzaga-Jauregui C, Dewey FE, Overton JD, Reid JG, Shuldiner AR, Baras A, Sampson KJ, Bleda M, Hadinnapola C, Haimel M, Bogaard HJ, Church C, Coghlan G, Corris PA, Eyries M, Gibbs JSR, Girerd B, Houweling AC, Humbert M, Guignabert C, Kiely DG, Lawrie A, MacKenzie Ross RV, Martin JM, Montani D, Peacock AJ, Pepke-Zaba J, Soubrier F, Suntharalingam J, Toshner M, Treacy CM, Trembath RC, Vonk Noordegraaf A, Wharton J, Wilkins MR, Wort SJ, Yates K, Gräf S, Morrell NW, Krishnan U, Rosenzweig EB, Shen Y, Nichols CG, Kass RS, Chung WK. Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2018; 11:e002087. [PMID: 30354297 PMCID: PMC6206877 DOI: 10.1161/circgen.118.002087] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 08/01/2018] [Indexed: 11/16/2022]
Abstract
BACKGROUND In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, because of mutations in KCNK3, was identified as a genetic cause and pharmacological target. METHODS Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult-onset group I PAH patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult-onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis. RESULTS We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes SUR1 (sulfonylurea receptor 1)-a regulatory subunit of the ATP-sensitive potassium channel. We observed loss of ATP-sensitive potassium channel function for all ABCC8 variants evaluated and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide. CONCLUSIONS Novel and rare missense variants in ABCC8 are associated with PAH. Identified ABCC8 mutations decreased ATP-sensitive potassium channel function, which was pharmacologically recovered.
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Affiliation(s)
- Michael S. Bohnen
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Lijiang Ma
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Na Zhu
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Hongjian Qi
- Dept of Applied Physics & Applied Mathematics, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Conor McClenaghan
- Dept of Cell Biology & Physiology, and the Centre for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Washington University in St Louis, St Louis, MO
| | | | | | - John D. Overton
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Jeffrey G. Reid
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Alan R. Shuldiner
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Aris Baras
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Kevin J. Sampson
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Marta Bleda
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Charaka Hadinnapola
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Matthias Haimel
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | | | - Colin Church
- Golden Jubilee National Hospital, Glasgow, Scotland
| | | | - Paul A. Corris
- Newcastle University & The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mélanie Eyries
- Dépt de génétique, hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, and UMR_S 1166-ICAN, INSERM, UPMC Sorbonne Universités, Paris, France
| | - J. Simon R. Gibbs
- National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Barbara Girerd
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | - Marc Humbert
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Christophe Guignabert
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | - Allan Lawrie
- Dept of Infection, Immunity & Cardiovascular Disease, University of Sheffield
| | | | - Jennifer M. Martin
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - David Montani
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | | | - Florent Soubrier
- Dépt de génétique, hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, and UMR_S 1166-ICAN, INSERM, UPMC Sorbonne Universités, Paris, France
| | | | - Mark Toshner
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
- Papworth Hospital, Cambridge
| | - Carmen M. Treacy
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Richard C. Trembath
- Division of Genetics & Molecular Medicine, King’s College, London, Hammersmith Campus, London
| | | | - John Wharton
- Dept of Medicine, Imperial College London, Hammersmith Campus, London
| | - Martin R. Wilkins
- Dept of Medicine, Imperial College London, Hammersmith Campus, London
| | - Stephen J. Wort
- National Heart & Lung Institute, Imperial College London, United Kingdom
- Royal Brompton Hospital, London, United Kingdom
| | - Katherine Yates
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Stefan Gräf
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
- Dept of Haematology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Nicholas W. Morrell
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Usha Krishnan
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Erika B. Rosenzweig
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Yufeng Shen
- Dept of Applied Physics & Applied Mathematics, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Colin G. Nichols
- Dept of Cell Biology & Physiology, and the Centre for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Washington University in St Louis, St Louis, MO
| | - Robert S. Kass
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Wendy K. Chung
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
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196
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Abstract
PURPOSE OF REVIEW To discuss advances in our understanding of beta-cell heterogeneity and the ramifications of this for type 1 diabetes (T1D) and its therapy. RECENT FINDINGS A number of studies have challenged the long-standing dogma that the majority of beta cells are eliminated in T1D. As many as 80% are present in some T1D subjects. Why don't these cells function properly to release insulin in response to high glucose? Other findings deploying single-cell "omics" to study both healthy and diseased cells-from patients with both T1D and type 2 diabetes (T2D)-have revealed cell subpopulations and heterogeneity at the transcriptomic/protein level between individual cells. Finally, our own and others' findings have demonstrated the importance of functional beta-cell subpopulations for insulin secretion. Heterogeneity may endow beta cells with molecular features that predispose them to failure/death during T1D.
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Affiliation(s)
- Richard K. P. Benninger
- 0000 0001 0703 675Xgrid.430503.1Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
- 0000 0001 0703 675Xgrid.430503.1Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
| | - Craig Dorrell
- 0000 0000 9758 5690grid.5288.7Oregon Stem Cell Center, Papé Family Pediatric Research Institute, Department of Pediatrics, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239 USA
| | - David J. Hodson
- 0000 0004 1936 7486grid.6572.6Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Birmingham, B15 2TT UK
- Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, B15 2TH UK
- COMPARE, University of Birmingham and University of Nottingham Midlands, Nottingham, UK
| | - Guy A. Rutter
- 0000 0001 2113 8111grid.7445.2Section of Cell Biology and Functional Genomics, Department of Medicine, Imperial College London, London, W12 0NN UK
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197
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Chronic palmitic acid-induced lipotoxicity correlates with defective trafficking of ATP sensitive potassium channels in pancreatic β cells. J Nutr Biochem 2018; 59:37-48. [DOI: 10.1016/j.jnutbio.2018.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/13/2018] [Accepted: 05/10/2018] [Indexed: 01/09/2023]
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198
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Zhang Q, Li C, Zhang T, Ge Y, Han X, Sun S, Ding J, Lu M, Hu G. Deletion of Kir6.2/SUR1 potassium channels rescues diminishing of DA neurons via decreasing iron accumulation in PD. Mol Cell Neurosci 2018; 92:164-176. [PMID: 30171894 DOI: 10.1016/j.mcn.2018.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/16/2018] [Accepted: 08/25/2018] [Indexed: 11/25/2022] Open
Abstract
ATP-sensitive potassium (K-ATP) channels express in the central nervous system extensively which coupling cell metabolism and cellular electrical activity. K-ATP channels in mature substantia nigra (SN) dopaminergic (DA) neurons are composed of inwardly rectifying potassium channel (Kir) subunit 6.2 and sulfonylurea receptor 1 (SUR1). Our previous study revealed that regulating K-ATP channel exerts the protective effect on DA neurons in a mouse model of Parkinson's disease (PD). However, the detailed mechanism underlying the role of Kir6.2/K-ATP remains unclear. In the present study, we found the deletion of Kir6.2 dramatically alleviated PD-like motor dysfunction of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) PD model. We further found that Kir6.2 knockout selectively restored the reduction of both DA neuronal number and dopamine transmitter level in the nigrostriatal of MPTP-treated PD mice. To gain some understanding on the molecular basis of this effect, we focused on the regulation of Kir6.2 deletion on iron metabolism which is tightly associated with DA neuron damage. We found that Kir6.2 knockout suppressed the excessive iron accumulation in MPTP-treated mouse midbrain and inhibited the upregulation of ferritin light chain (FTL), which is a main intracellular iron storage protein. We probed further and found out that the deletion of Kir6.2 inhibited the excessive production of FTL via IRP-IRE regulatory system, and thereby protecting SN DA neurons against MPTP challenge. Our findings suggest that Kir6.2 plays a crucial role in the pathogenesis of PD and regulating Kir6.2/K-ATP channel may be a promising strategy for PD treatment.
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Affiliation(s)
- Qian Zhang
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Chengwu Li
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Ting Zhang
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Yaping Ge
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Xiaojuan Han
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Sifan Sun
- First Clinic Medical School, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China
| | - Jianhua Ding
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China
| | - Ming Lu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China.
| | - Gang Hu
- Department of Pharmacology, School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, 138 Xianlin Avenue, Nanjing, Jiangsu 210023, China; Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, 101 Longmian Avenue, Nanjing, Jiangsu 211166, China.
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199
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Imai R, Misaka S, Horita S, Yokota S, O'hashi R, Maejima Y, Shimomura K. Memantine has no effect on K ATP channels in pancreatic β cells. BMC Res Notes 2018; 11:614. [PMID: 30144824 PMCID: PMC6109345 DOI: 10.1186/s13104-018-3715-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 08/20/2018] [Indexed: 11/19/2022] Open
Abstract
Objective Memantine, a drug for Alzheimer’s disease, is considered to suppress excessive stimulation of N-methyl-d-aspartic acid receptors and to prevent neuronal death. However, a recent report indicated that the neuronal KATP channel also can become a target of memantine. The KATP channel is a key regulator of insulin secretion in pancreatic β cells. Therefore, if memantine could inhibit the KATP channel in pancreatic β cells, it would be an effective drug for both Alzheimer’s disease and diabetes. However, there is no report on the effect of memantine on the KATP channel in pancreatic β cells. Therefore, we investigated whether memantine affect the blood glucose level, insulin secretion and KATP channel activity in pancreatic β cells. Results An intraperitoneal glucose tolerance test was performed with or without memantine (1 mg/kg) injection in intact mice. Insulin secretion from isolated islets was measured under low (2 mM) and high (20 mM) glucose concentrations with or without memantine (1 μM). The effect of memantine (1 μM) on KATP channel currents in isolated pancreatic β cells was recorded using the whole-cell patch-clamp technique. Memantine had no effect on the blood glucose level, insulin secretion from isolated islets or KATP channel current in pancreatic β cells.
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Affiliation(s)
- Ryota Imai
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan. .,Tsumura Kampo Research Laboratories, Kampo Research & Development Division, Tsumura & Co., Ibaraki, Japan.
| | - Shingen Misaka
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Shoichiro Horita
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Shoko Yokota
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Rie O'hashi
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Yuko Maejima
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Kenju Shimomura
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan
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200
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Feetham CH, O'Brien F, Barrett-Jolley R. Ion Channels in the Paraventricular Hypothalamic Nucleus (PVN); Emerging Diversity and Functional Roles. Front Physiol 2018; 9:760. [PMID: 30034342 PMCID: PMC6043726 DOI: 10.3389/fphys.2018.00760] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 05/30/2018] [Indexed: 12/11/2022] Open
Abstract
The paraventricular nucleus of the hypothalamus (PVN) is critical for the regulation of homeostatic function. Although also important for endocrine regulation, it has been referred to as the "autonomic master controller." The emerging consensus is that the PVN is a multifunctional nucleus, with autonomic roles including (but not limited to) coordination of cardiovascular, thermoregulatory, metabolic, circadian and stress responses. However, the cellular mechanisms underlying these multifunctional roles remain poorly understood. Neurones from the PVN project to and can alter the function of sympathetic control regions in the medulla and spinal cord. Dysfunction of sympathetic pre-autonomic neurones (typically hyperactivity) is linked to several diseases including hypertension and heart failure and targeting this region with specific pharmacological or biological agents is a promising area of medical research. However, to facilitate future medical exploitation of the PVN, more detailed models of its neuronal control are required; populated by a greater compliment of constituent ion channels. Whilst the cytoarchitecture, projections and neurotransmitters present in the PVN are reasonably well documented, there have been fewer studies on the expression and interplay of ion channels. In this review we bring together an up to date analysis of PVN ion channel studies and discuss how these channels may interact to control, in particular, the activity of the sympathetic system.
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Affiliation(s)
- Claire H Feetham
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Fiona O'Brien
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Richard Barrett-Jolley
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
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