1
|
Arrell DK, Park S, Yamada S, Alekseev AE, Garmany A, Jeon R, Vuckovic I, Lindor JZ, Terzic A. K ATP channel dependent heart multiome atlas. Sci Rep 2022; 12:7314. [PMID: 35513538 PMCID: PMC9072320 DOI: 10.1038/s41598-022-11323-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 04/21/2022] [Indexed: 11/09/2022] Open
Abstract
Plasmalemmal ATP sensitive potassium (KATP) channels are recognized metabolic sensors, yet their cellular reach is less well understood. Here, transgenic Kir6.2 null hearts devoid of the KATP channel pore underwent multiomics surveillance and systems interrogation versus wildtype counterparts. Despite maintained organ performance, the knockout proteome deviated beyond a discrete loss of constitutive KATP channel subunits. Multidimensional nano-flow liquid chromatography tandem mass spectrometry resolved 111 differentially expressed proteins and their expanded network neighborhood, dominated by metabolic process engagement. Independent multimodal chemometric gas and liquid chromatography mass spectrometry unveiled differential expression of over one quarter of measured metabolites discriminating the Kir6.2 deficient heart metabolome. Supervised class analogy ranking and unsupervised enrichment analysis prioritized nicotinamide adenine dinucleotide (NAD+), affirmed by extensive overrepresentation of NAD+ associated circuitry. The remodeled metabolome and proteome revealed functional convergence and an integrated signature of disease susceptibility. Deciphered cardiac patterns were traceable in the corresponding plasma metabolome, with tissue concordant plasma changes offering surrogate metabolite markers of myocardial latent vulnerability. Thus, Kir6.2 deficit precipitates multiome reorganization, mapping a comprehensive atlas of the KATP channel dependent landscape.
Collapse
Affiliation(s)
- D Kent Arrell
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Sungjo Park
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA.,Department of Biochemistry & Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Satsuki Yamada
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA.,Division of Geriatric Medicine & Gerontology, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | - Alexey E Alekseev
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA.,Institute of Theoretical and Experimental Biophysics, Russian Academy of Science, Pushchino, Moscow Region, Russia
| | - Armin Garmany
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA.,Mayo Clinic Alix School of Medicine, Regenerative Sciences Track, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, USA
| | - Ryounghoon Jeon
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Ivan Vuckovic
- Department of Biochemistry & Molecular Biology, Mayo Clinic, Rochester, MN, USA.,Metabolomics Core, Mayo Clinic, Rochester, MN, USA
| | - Jelena Zlatkovic Lindor
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Andre Terzic
- Marriott Heart Disease Research Program, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA. .,Marriott Family Comprehensive Cardiac Regenerative Medicine, Center for Regenerative Medicine, Mayo Clinic, Rochester, MN, USA. .,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA. .,Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Puljung M, Vedovato N, Usher S, Ashcroft F. Activation mechanism of ATP-sensitive K + channels explored with real-time nucleotide binding. eLife 2019; 8:41103. [PMID: 30789344 PMCID: PMC6400584 DOI: 10.7554/elife.41103] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 02/14/2019] [Indexed: 01/15/2023] Open
Abstract
The response of ATP-sensitive K+ channels (KATP) to cellular metabolism is coordinated by three classes of nucleotide binding site (NBS). We used a novel approach involving labeling of intact channels in a native, membrane environment with a non-canonical fluorescent amino acid and measurement (using FRET with fluorescent nucleotides) of steady-state and time-resolved nucleotide binding to dissect the role of NBS2 of the accessory SUR1 subunit of KATP in channel gating. Binding to NBS2 was Mg2+-independent, but Mg2+ was required to trigger a conformational change in SUR1. Mutation of a lysine (K1384A) in NBS2 that coordinates bound nucleotides increased the EC50 for trinitrophenyl-ADP binding to NBS2, but only in the presence of Mg2+, indicating that this mutation disrupts the ligand-induced conformational change. Comparison of nucleotide-binding with ionic currents suggests a model in which each nucleotide binding event to NBS2 of SUR1 is independent and promotes KATP activation by the same amount.
Collapse
Affiliation(s)
- Michael Puljung
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Samuel Usher
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
4
|
Sikimic J, McMillen TS, Bleile C, Dastvan F, Quast U, Krippeit-Drews P, Drews G, Bryan J. ATP binding without hydrolysis switches sulfonylurea receptor 1 (SUR1) to outward-facing conformations that activate K ATP channels. J Biol Chem 2018; 294:3707-3719. [PMID: 30587573 DOI: 10.1074/jbc.ra118.005236] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 12/19/2018] [Indexed: 11/06/2022] Open
Abstract
Neuroendocrine-type ATP-sensitive K+ (KATP) channels are metabolite sensors coupling membrane potential with metabolism, thereby linking insulin secretion to plasma glucose levels. They are octameric complexes, (SUR1/Kir6.2)4, comprising sulfonylurea receptor 1 (SUR1 or ABCC8) and a K+-selective inward rectifier (Kir6.2 or KCNJ11). Interactions between nucleotide-, agonist-, and antagonist-binding sites affect channel activity allosterically. Although it is hypothesized that opening these channels requires SUR1-mediated MgATP hydrolysis, we show here that ATP binding to SUR1, without hydrolysis, opens channels when nucleotide antagonism on Kir6.2 is minimized and SUR1 mutants with increased ATP affinities are used. We found that ATP binding is sufficient to switch SUR1 alone between inward- or outward-facing conformations with low or high dissociation constant, KD , values for the conformation-sensitive channel antagonist [3H]glibenclamide ([3H]GBM), indicating that ATP can act as a pure agonist. Assembly with Kir6.2 reduced SUR1's KD for [3H]GBM. This reduction required the Kir N terminus (KNtp), consistent with KNtp occupying a "transport cavity," thus positioning it to link ATP-induced SUR1 conformational changes to channel gating. Moreover, ATP/GBM site coupling was constrained in WT SUR1/WT Kir6.2 channels; ATP-bound channels had a lower KD for [3H]GBM than ATP-bound SUR1. This constraint was largely eliminated by the Q1179R neonatal diabetes-associated mutation in helix 15, suggesting that a "swapped" helix pair, 15 and 16, is part of a structural pathway connecting the ATP/GBM sites. Our results suggest that ATP binding to SUR1 biases KATP channels toward open states, consistent with SUR1 variants with lower KD values causing neonatal diabetes, whereas increased KD values cause congenital hyperinsulinism.
Collapse
Affiliation(s)
- Jelena Sikimic
- From the Institute of Pharmacy, Department of Pharmacology, University of Tübingen, D-72076 Tübingen, Germany and
| | - Timothy S McMillen
- Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122, and
| | - Cita Bleile
- From the Institute of Pharmacy, Department of Pharmacology, University of Tübingen, D-72076 Tübingen, Germany and
| | - Frank Dastvan
- Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122, and
| | - Ulrich Quast
- Department of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, D-72074 Tübingen, Germany
| | - Peter Krippeit-Drews
- From the Institute of Pharmacy, Department of Pharmacology, University of Tübingen, D-72076 Tübingen, Germany and
| | - Gisela Drews
- From the Institute of Pharmacy, Department of Pharmacology, University of Tübingen, D-72076 Tübingen, Germany and
| | - Joseph Bryan
- Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122, and
| |
Collapse
|
5
|
Vedovato N, Ashcroft FM, Puljung MC. The Nucleotide-Binding Sites of SUR1: A Mechanistic Model. Biophys J 2016; 109:2452-2460. [PMID: 26682803 PMCID: PMC4699857 DOI: 10.1016/j.bpj.2015.10.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 10/22/2015] [Accepted: 10/22/2015] [Indexed: 12/19/2022] Open
Abstract
ATP-sensitive potassium (KATP) channels comprise four pore-forming Kir6.2 subunits and four modulatory sulfonylurea receptor (SUR) subunits. The latter belong to the ATP-binding cassette family of transporters. KATP channels are inhibited by ATP (or ADP) binding to Kir6.2 and activated by Mg-nucleotide interactions with SUR. This dual regulation enables the KATP channel to couple the metabolic state of a cell to its electrical excitability and is crucial for the KATP channel’s role in regulating insulin secretion, cardiac and neuronal excitability, and vascular tone. Here, we review the regulation of the KATP channel by adenine nucleotides and present an equilibrium allosteric model for nucleotide activation and inhibition. The model can account for many experimental observations in the literature and provides testable predictions for future experiments.
Collapse
Affiliation(s)
- Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Michael C Puljung
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom.
| |
Collapse
|
6
|
de Marcos Lousa C, Dietrich D, Johnson B, Baldwin S, Holdsworth M, Theodoulou FL, Baker A. The NBDs that wouldn't die. Commun Integr Biol 2014. [DOI: 10.4161/cib.7621] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
|
7
|
Hosy E, Vivaudou M. The unusual stoichiometry of ADP activation of the KATP channel. Front Physiol 2014; 5:11. [PMID: 24478723 PMCID: PMC3904077 DOI: 10.3389/fphys.2014.00011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 01/07/2014] [Indexed: 11/27/2022] Open
Abstract
KATP channels, oligomers of 4 pore-forming Kir6.2 proteins and 4 sulfonylurea receptors (SUR), sense metabolism by monitoring both cytosolic ATP, which closes the channel by interacting with Kir6.2, and ADP, which opens it via SUR. SUR mutations that alter activation by ADP are a major cause of KATP channelopathies. We examined the mechanism of ADP activation by analysis of single-channel and macropatch recordings from Xenopus oocytes expressing various mixtures of wild-type SUR2A and an ADP-activation-defective mutant. Evaluation of the data by a binomial distribution model suggests that wild-type and mutant SURs freely co-assemble and that channel activation results from interaction of ADP with only 2 of 4 SURs. This finding explains the heterozygous nature of most KATP channelopathies linked to mutations altering ADP activation. It also suggests that the channel deviates from circular symmetry and could function as a dimer-of-dimers.
Collapse
Affiliation(s)
- Eric Hosy
- Institut de Biologie Structurale, University Grenoble Alpes Grenoble, France ; Laboratory of Excellence, Ion Channel Science and Therapeutics, CNRS, Institut de Biologie Structurale Grenoble, France ; CEA, DSV, Institut de Biologie Structurale Grenoble, France
| | - Michel Vivaudou
- Institut de Biologie Structurale, University Grenoble Alpes Grenoble, France ; Laboratory of Excellence, Ion Channel Science and Therapeutics, CNRS, Institut de Biologie Structurale Grenoble, France ; CEA, DSV, Institut de Biologie Structurale Grenoble, France
| |
Collapse
|
8
|
Hu D, Barajas-Martínez H, Terzic A, Park S, Pfeiffer R, Burashnikov E, Wu Y, Borggrefe M, Veltmann C, Schimpf R, Cai JJ, Nam GB, Deshmukh P, Scheinman M, Preminger M, Steinberg J, López-Izquierdo A, Ponce-Balbuena D, Wolpert C, Haïssaguerre M, Sánchez-Chapula JA, Antzelevitch C. ABCC9 is a novel Brugada and early repolarization syndrome susceptibility gene. Int J Cardiol 2014; 171:431-42. [PMID: 24439875 DOI: 10.1016/j.ijcard.2013.12.084] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 12/17/2013] [Accepted: 12/21/2013] [Indexed: 12/26/2022]
Abstract
BACKGROUND Genetic defects in KCNJ8, encoding the Kir6.1 subunit of the ATP-sensitive K(+) channel (I(K-ATP)), have previously been associated with early repolarization (ERS) and Brugada (BrS) syndromes. Here we test the hypothesis that genetic variants in ABCC9, encoding the ATP-binding cassette transporter of IK-ATP (SUR2A), are also associated with both BrS and ERS. METHODS AND RESULTS Direct sequencing of all ERS/BrS susceptibility genes was performed on 150 probands and family members. Whole-cell and inside-out patch-clamp methods were used to characterize mutant channels expressed in TSA201-cells. Eight ABCC9 mutations were uncovered in 11 male BrS probands. Four probands, diagnosed with ERS, carried a highly-conserved mutation, V734I-ABCC9. Functional expression of the V734I variant yielded a Mg-ATP IC₅₀ that was 5-fold that of wild-type (WT). An 18-y/o male with global ERS inherited an SCN5A-E1784K mutation from his mother, who displayed long QT intervals, and S1402C-ABCC9 mutation from his father, who displayed an ER pattern. ABCC9-S1402C likewise caused a gain of function of IK-ATP with a shift of ATP IC₅₀ from 8.5 ± 2 mM to 13.4 ± 5 μM (p<0.05). The SCN5A mutation reduced peak INa to 39% of WT (p<0.01), shifted steady-state inactivation by -18.0 mV (p<0.01) and increased late I(Na) from 0.14% to 2.01% of peak I(Na) (p<0.01). CONCLUSION Our study is the first to identify ABCC9 as a susceptibility gene for ERS and BrS. Our findings also suggest that a gain-of-function in I(K-ATP) when coupled with a loss-of-function in SCN5A may underlie type 3 ERS, which is associated with a severe arrhythmic phenotype.
Collapse
Affiliation(s)
- Dan Hu
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA.
| | - Hector Barajas-Martínez
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Andre Terzic
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | - Sungjo Park
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | - Ryan Pfeiffer
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Elena Burashnikov
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Yuesheng Wu
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA
| | - Martin Borggrefe
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany
| | - Christian Veltmann
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany
| | - Rainer Schimpf
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany
| | | | - Gi-Byong Nam
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | | | - Melvin Scheinman
- Department of Medicine, University of California, San Francisco, CA, USA
| | | | - Jonathan Steinberg
- Arrhythmia Institute, Valley Health System, Columbia University College of Physicians & Surgeons, New York, NY, USA
| | - Angélica López-Izquierdo
- Unidad de Investigación, "Carlos Méndez" del Centro Universitario de Investigaciones Biomédicas de la Universidad de Colima, Colima, Mexico
| | - Daniela Ponce-Balbuena
- Unidad de Investigación, "Carlos Méndez" del Centro Universitario de Investigaciones Biomédicas de la Universidad de Colima, Colima, Mexico
| | - Christian Wolpert
- 1st Department of Medicine-Cardiology, University Medical Centre Mannheim, Mannheim, Germany
| | - Michel Haïssaguerre
- Hôspital Cardiologique du Haut Lévêque, Université Bordeaux II, Pessac cedex, France
| | - José Antonio Sánchez-Chapula
- Unidad de Investigación, "Carlos Méndez" del Centro Universitario de Investigaciones Biomédicas de la Universidad de Colima, Colima, Mexico
| | - Charles Antzelevitch
- Department of Molecular Genetics and Experimental Cardiology, Masonic Medical Research Laboratory, Utica, NY, USA.
| |
Collapse
|
9
|
Hiraki Y, Miyatake S, Hayashidani M, Nishimura Y, Matsuura H, Kamada M, Kawagoe T, Yunoki K, Okamoto N, Yofune H, Nakashima M, Tsurusaki Y, Satisu H, Murakami A, Miyake N, Nishimura G, Matsumoto N. Aortic aneurysm and craniosynostosis in a family with Cantu syndrome. Am J Med Genet A 2013; 164A:231-6. [PMID: 24352916 DOI: 10.1002/ajmg.a.36228] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 08/08/2013] [Indexed: 12/22/2022]
Abstract
Cantu syndrome is an autosomal dominant overgrowth syndrome associated with facial dysmorphism, congenital hypertrichosis, and cardiomegaly. Some affected individuals show bone undermodeling of variable severity. Recent investigations revealed that the disorder is caused by a mutation in ABCC9, encoding a regulatory SUR2 subunit of an ATP-sensitive potassium channel mainly expressed in cardiac and skeletal muscle as well as vascular smooth muscle. We report here on a Japanese family with this syndrome. An affected boy and his father had a novel missense mutation in ABCC9. Each patient had a coarse face and hypertrichosis. However, cardiomegaly was seen only in the boy, and macrosomia only in the father. Skeletal changes were not evident in either patient. Craniosynostosis in the boy and the development of aortic aneurysm in the father are previously undescribed associations with Cantu syndrome.
Collapse
Affiliation(s)
- Yoko Hiraki
- Hiroshima Municipal Center for Child Health and Development, Hiroshima, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Sierra A, Zhu Z, Sapay N, Sharotri V, Kline CF, Luczak ED, Subbotina E, Sivaprasadarao A, Snyder PM, Mohler PJ, Anderson ME, Vivaudou M, Zingman LV, Hodgson-Zingman DM. Regulation of cardiac ATP-sensitive potassium channel surface expression by calcium/calmodulin-dependent protein kinase II. J Biol Chem 2012; 288:1568-81. [PMID: 23223335 DOI: 10.1074/jbc.m112.429548] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cardiac ATP-sensitive potassium (K(ATP)) channels are key sensors and effectors of the metabolic status of cardiomyocytes. Alteration in their expression impacts their effectiveness in maintaining cellular energy homeostasis and resistance to injury. We sought to determine how activation of calcium/calmodulin-dependent protein kinase II (CaMKII), a central regulator of calcium signaling, translates into reduced membrane expression and current capacity of cardiac K(ATP) channels. We used real-time monitoring of K(ATP) channel current density, immunohistochemistry, and biotinylation studies in isolated hearts and cardiomyocytes from wild-type and transgenic mice as well as HEK cells expressing wild-type and mutant K(ATP) channel subunits to track the dynamics of K(ATP) channel surface expression. Results showed that activation of CaMKII triggered dynamin-dependent internalization of K(ATP) channels. This process required phosphorylation of threonine at 180 and 224 and an intact (330)YSKF(333) endocytosis motif of the K(ATP) channel Kir6.2 pore-forming subunit. A molecular model of the μ2 subunit of the endocytosis adaptor protein, AP2, complexed with Kir6.2 predicted that μ2 docks by interaction with (330)YSKF(333) and Thr-180 on one and Thr-224 on the adjacent Kir6.2 subunit. Phosphorylation of Thr-180 and Thr-224 would favor interactions with the corresponding arginine- and lysine-rich loops on μ2. We concluded that calcium-dependent activation of CaMKII results in phosphorylation of Kir6.2, which promotes endocytosis of cardiac K(ATP) channel subunits. This mechanism couples the surface expression of cardiac K(ATP) channels with calcium signaling and reveals new targets to improve cardiac energy efficiency and stress resistance.
Collapse
Affiliation(s)
- Ana Sierra
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, Iowa 52242, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Zhu Z, Burnett CML, Maksymov G, Stepniak E, Sierra A, Subbotina E, Anderson ME, Coetzee WA, Hodgson-Zingman DM, Zingman LV. Reduction in number of sarcolemmal KATP channels slows cardiac action potential duration shortening under hypoxia. Biochem Biophys Res Commun 2011; 415:637-41. [PMID: 22079630 DOI: 10.1016/j.bbrc.2011.10.125] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 10/26/2011] [Indexed: 12/25/2022]
Abstract
The cardiovascular system operates under demands ranging from conditions of rest to extreme stress. One mechanism of cardiac stress tolerance is action potential duration shortening driven by ATP-sensitive potassium (K(ATP)) channels. K(ATP) channel expression has a significant physiologic impact on action potential duration shortening and myocardial energy consumption in response to physiologic heart rate acceleration. However, the effect of reduced channel expression on action potential duration shortening in response to severe metabolic stress is yet to be established. Here, transgenic mice with myocardium-specific expression of a dominant negative K(ATP) channel subunit were compared with littermate controls. Evaluation of K(ATP) channel whole cell current and channel number/patch was assessed by patch clamp in isolated ventricular cardiomyocytes. Monophasic action potentials were monitored in retrogradely perfused, isolated hearts during the transition to hypoxic perfusate. An 80-85% reduction in cardiac K(ATP) channel current density results in a similar magnitude, but significantly slower rate, of shortening of the ventricular action potential duration in response to severe hypoxia, despite no significant difference in coronary flow. Therefore, the number of functional cardiac sarcolemmal K(ATP) channels is a critical determinant of the rate of adaptation of myocardial membrane excitability, with implications for optimization of cardiac energy consumption and consequent cardioprotection under conditions of severe metabolic stress.
Collapse
Affiliation(s)
- Zhiyong Zhu
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Terzic A, Alekseev AE, Yamada S, Reyes S, Olson TM. Advances in cardiac ATP-sensitive K+ channelopathies from molecules to populations. Circ Arrhythm Electrophysiol 2011; 4:577-85. [PMID: 21846889 DOI: 10.1161/circep.110.957662] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Internal Medicine, Department of Molecular Pharmacology and Experimental Therapeutics, Department of Medical Genetics, Mayo Clinic, Rochester, MN, USA.
| | | | | | | | | |
Collapse
|
13
|
Chao C, Liang T, Kang Y, Lin X, Xie H, Feng ZP, Gaisano HY. Syntaxin-1A inhibits KATP channels by interacting with specific conserved motifs within sulfonylurea receptor 2A. J Mol Cell Cardiol 2011; 51:790-802. [PMID: 21884702 DOI: 10.1016/j.yjmcc.2011.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 07/25/2011] [Accepted: 08/13/2011] [Indexed: 11/19/2022]
Abstract
We previously demonstrated that syntaxin (Syn)-1A is present in the sarcolemma of rat cardiomyocytes and binds sulfonylurea receptor (SUR) 2A nucleotide binding folds (NBFs) to inhibit ATP-sensitive potassium (K(ATP)) channel. Here, we examined for the precise domains within the NBFs of SUR2A that may interact with Syn-1A. Specifically, we tested truncated NBF protein segments encompassing the conserved motifs Walker A (W(A)), signature/Linker (L), and Walker B (W(B)). In vitro binding results indicate that the domains encompassing W(A) and L of NBF-1 and all three conserved motifs of NBF-2 bound Syn-1A. Electrophysiological studies, employing inside-out patch-clamp recordings from SUR2A/Kir6.2 expressing HEK cells and mouse cardiomyocytes, show that W(B) and L of NBF-1 and all three NBF-2 truncated protein segments reduced Syn-1A inhibition of SUR2A/K(ATP) channels. Remarkably, these same NBF-1 and -2 truncated proteins could independently disrupt the intimate FRET interactions of full length SUR2A (-mCherry) and Syn-1A (-EGFP). These results taken together indicate that Syn-1A possibly maintains inhibition of cardiac ventricular K(ATP) channels by binding to large regions of NBF-1 and NBF-2 to stabilize the NBF-1-NBF-2 heterodimer formation and prevent ATP-binding and ATP hydrolysis. Since K(ATP) channels are closely coupled to metabolic states, we postulate that these very intimate Syn-1A-SUR2A interactions are critically important for myocardial protection during stress, in which profound changes in metabolic factors (pH, ATP) could modulate these Syn-1A-SUR2A interactions.
Collapse
MESH Headings
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Adenosine Triphosphate/biosynthesis
- Amino Acid Motifs
- Animals
- Binding Sites
- Cell Membrane/metabolism
- Conserved Sequence
- Fluorescence Resonance Energy Transfer
- HEK293 Cells
- Humans
- KATP Channels/chemistry
- KATP Channels/genetics
- KATP Channels/metabolism
- Male
- Mice
- Microscopy, Fluorescence
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Oligopeptides/chemistry
- Oligopeptides/genetics
- Oligopeptides/metabolism
- Patch-Clamp Techniques
- Plasmids
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/chemistry
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Drug/chemistry
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Signal Transduction/physiology
- Sulfonylurea Receptors
- Syntaxin 1/chemistry
- Syntaxin 1/genetics
- Syntaxin 1/metabolism
Collapse
Affiliation(s)
- Christin Chao
- Department of Medicine, University of Toronto, Room 7368, Medical Sciences Building, Toronto, ON, Canada
| | | | | | | | | | | | | |
Collapse
|
14
|
Zingman LV, Zhu Z, Sierra A, Stepniak E, Burnett CML, Maksymov G, Anderson ME, Coetzee WA, Hodgson-Zingman DM. Exercise-induced expression of cardiac ATP-sensitive potassium channels promotes action potential shortening and energy conservation. J Mol Cell Cardiol 2011; 51:72-81. [PMID: 21439969 DOI: 10.1016/j.yjmcc.2011.03.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/19/2011] [Accepted: 03/14/2011] [Indexed: 12/25/2022]
Abstract
Physical activity is one of the most important determinants of cardiac function. The ability of the heart to increase delivery of oxygen and metabolic fuels relies on an array of adaptive responses necessary to match bodily demand while avoiding exhaustion of cardiac resources. The ATP-sensitive potassium (K(ATP)) channel has the unique ability to adjust cardiac membrane excitability in accordance with ATP and ADP levels, and up-regulation of its expression that occurs in response to exercise could represent a critical element of this adaption. However, the mechanism by which K(ATP) channel expression changes result in a beneficial effect on cardiac excitability and function remains to be established. Here, we demonstrate that an exercise-induced rise in K(ATP) channel expression enhanced the rate and magnitude of action potential shortening in response to heart rate acceleration. This adaptation in membrane excitability promoted significant reduction in cardiac energy consumption under escalating workloads. Genetic disruption of normal K(ATP) channel pore function abolished the exercise-related changes in action potential duration adjustment and caused increased cardiac energy consumption. Thus, an expression-driven enhancement in the K(ATP) channel-dependent membrane response to alterations in cardiac workload represents a previously unrecognized mechanism for adaptation to physical activity and a potential target for cardioprotection.
Collapse
Affiliation(s)
- Leonid V Zingman
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Edghill EL, Flanagan SE, Ellard S. Permanent neonatal diabetes due to activating mutations in ABCC8 and KCNJ11. Rev Endocr Metab Disord 2010; 11:193-8. [PMID: 20922570 DOI: 10.1007/s11154-010-9149-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ATP-sensitive potassium (K(ATP)) channel is composed of two subunits SUR1 and Kir6.2. The channel is key for glucose stimulated insulin release from the pancreatic beta cell. Activating mutations have been identified in the genes encoding these subunits, ABCC8 and KCNJ11, and account for approximately 40% of permanent neonatal diabetes cases. The majority of patients with a K(ATP) mutation present with isolated diabetes however some have presented with the Developmental delay, Epilepsy and Neonatal Diabetes syndrome. This review focuses on mutations in the K(ATP) channel which result in permanent neonatal diabetes, we review the clinical and functional effects as well as the implications for treatment.
Collapse
MESH Headings
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- ATP-Binding Cassette Transporters/physiology
- Diabetes Mellitus/congenital
- Diabetes Mellitus/genetics
- Diabetes Mellitus/therapy
- Genetic Association Studies
- Humans
- Infant, Newborn
- Infant, Newborn, Diseases/genetics
- Infant, Newborn, Diseases/therapy
- KATP Channels/genetics
- KATP Channels/metabolism
- KATP Channels/physiology
- Models, Biological
- Mutation/physiology
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Inwardly Rectifying/physiology
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Receptors, Drug/physiology
- Sulfonylurea Receptors
Collapse
Affiliation(s)
- Emma L Edghill
- Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Barrack Road, Exeter, UK
| | | | | |
Collapse
|
16
|
Wanke D, Kolukisaoglu HU. An update on the ABCC transporter family in plants: many genes, many proteins, but how many functions? PLANT BIOLOGY (STUTTGART, GERMANY) 2010; 12 Suppl 1:15-25. [PMID: 20712617 DOI: 10.1111/j.1438-8677.2010.00380.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The ABCC subfamily of the ATP binding cassette (ABC) transporters, which were formerly known as multidrug resistance-related proteins (MRPs), consists of closely related members found in all eukaryotic organisms. Although more than a decade of intensive research has elapsed since the first MRP protein was functionally characterised in Arabidopsis thaliana, knowledge of this particular transporter family is still limited in plants. Although ABCC proteins were originally defined as vacuolar pumps of glutathione-S (GS) conjugates, evidence, as well as speculation, on their endogenous functions inside the cell ranges from detoxification and heavy metal sequestration, to chlorophyll catabolite transport and ion channel regulation. The characterisation of knockout mutants in Arabidopsis has been pivotal for elucidation of different roles of ABCC transporters. However, a functional annotation for the majority of these transport proteins is still lacking, even in this model plant. On the one hand, this problem seems to be caused by functional redundancy between family members, which might lead to physiological complementation by a highly homologous gene in the mutant lines. On the other hand, there is growing evidence that the functional diversity of ABCC genes in Arabidopsis and other plants is far greater than previously assumed. For example, analysis of microarray expression data supports involvement of ABCC transporters in the response to biotic stress: particular changes in ABCC transcript levels are found, which are pathogen-specific and evoke distinct signalling cascades. Current knowledge about plant ABCC transporters indicates that novel and unexpected functions and substrates of these proteins are still waiting to be elucidated.
Collapse
Affiliation(s)
- D Wanke
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen, Germany
| | | |
Collapse
|
17
|
Flagg TP, Enkvetchakul D, Koster JC, Nichols CG. Muscle KATP channels: recent insights to energy sensing and myoprotection. Physiol Rev 2010; 90:799-829. [PMID: 20664073 DOI: 10.1152/physrev.00027.2009] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are present in the surface and internal membranes of cardiac, skeletal, and smooth muscle cells and provide a unique feedback between muscle cell metabolism and electrical activity. In so doing, they can play an important role in the control of contractility, particularly when cellular energetics are compromised, protecting the tissue against calcium overload and fiber damage, but the cost of this protection may be enhanced arrhythmic activity. Generated as complexes of Kir6.1 or Kir6.2 pore-forming subunits with regulatory sulfonylurea receptor subunits, SUR1 or SUR2, the differential assembly of K(ATP) channels in different tissues gives rise to tissue-specific physiological and pharmacological regulation, and hence to the tissue-specific pharmacological control of contractility. The last 10 years have provided insights into the regulation and role of muscle K(ATP) channels, in large part driven by studies of mice in which the protein determinants of channel activity have been deleted or modified. As yet, few human diseases have been correlated with altered muscle K(ATP) activity, but genetically modified animals give important insights to likely pathological roles of aberrant channel activity in different muscle types.
Collapse
Affiliation(s)
- Thomas P Flagg
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
| | | | | | | |
Collapse
|
18
|
|
19
|
de Wet H, Fotinou C, Amad N, Dreger M, Ashcroft FM. The ATPase activities of sulfonylurea receptor 2A and sulfonylurea receptor 2B are influenced by the C-terminal 42 amino acids. FEBS J 2010; 277:2654-62. [PMID: 20553499 DOI: 10.1111/j.1742-464x.2010.07675.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Unusually among ATP-binding cassette proteins, the sulfonylurea receptor (SUR) acts as a channel regulator. ATP-sensitive potassium channels are octameric complexes composed of four pore-forming Kir6.2 subunits and four regulatory SUR subunits. Two different genes encode SUR1 (ABCC8) and SUR2 (ABCC9), with the latter being differentially spliced to give SUR2A and SUR2B, which differ only in their C-terminal 42 amino acids. ATP-sensitive potassium channels containing these different SUR2 isoforms are differentially modulated by MgATP, with Kir6.2/SUR2B being activated more than Kir6.2/SUR2A. We show here that purified SUR2B has a lower ATPase activity and a 10-fold lower K(m) for MgATP than SUR2A. Similarly, the isolated nucleotide-binding domain (NBD) 2 of SUR2B was less active than that of SUR2A. We further found that the NBDs of SUR2B interact, and that the activity of full-length SUR cannot be predicted from that of either the isolated NBDs or NBD mixtures. Notably, deletion of the last 42 amino acids from NBD2 of SUR2 resulted in ATPase activity resembling that of NBD2 of SUR2A rather than that of NBD2 of SUR2B: this might indicate that these amino acids are responsible for the lower ATPase activity of SUR2B and the isolated NBD2 of SUR2B. We suggest that the lower ATPase activity of SUR2B may result in enhanced duration of the MgADP-bound state, leading to channel activation.
Collapse
Affiliation(s)
- Heidi de Wet
- Department of Physiology, Anatomy and Genetics, University of Oxford, UK
| | | | | | | | | |
Collapse
|
20
|
Hitchcock KE, Caudell DN, Sutton JT, Klegerman ME, Vela D, Pyne-Geithman GJ, Abruzzo T, Cyr PEP, Geng YJ, McPherson DD, Holland CK. Ultrasound-enhanced delivery of targeted echogenic liposomes in a novel ex vivo mouse aorta model. J Control Release 2010; 144:288-95. [PMID: 20202474 PMCID: PMC2878875 DOI: 10.1016/j.jconrel.2010.02.030] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 02/16/2010] [Accepted: 02/25/2010] [Indexed: 11/23/2022]
Abstract
The goal of this study was to determine whether targeted, Rhodamine-labeled echogenic liposomes (Rh-ELIP) containing nanobubbles could be delivered to the arterial wall, and whether 1-MHz continuous wave ultrasound would enhance this delivery profile. Aortae excised from apolipoprotein-E-deficient (n=8) and wild-type (n=8) mice were mounted in a pulsatile flow system through which Rh-ELIP were delivered in a stream of bovine serum albumin. Half the aortae from each group were treated with 1-MHz continuous wave ultrasound at 0.49 MPa peak-to-peak pressure, and half underwent sham exposure. Ultrasound parameters were chosen to promote stable cavitation and avoid inertial cavitation. A broadband hydrophone was used to monitor cavitation activity. After treatment, aortic sections were prepared for histology and analyzed by an individual blinded to treatment conditions. Delivery of Rh-ELIP to the vascular endothelium was observed, and sub-endothelial penetration of Rh-ELIP was present in five of five ultrasound-treated aortae and was absent in those not exposed to ultrasound. However, the degree of penetration in the ultrasound-exposed aortae was variable. There was no evidence of ultrasound-mediated tissue damage in any specimen. Ultrasound-enhanced delivery within the arterial wall was demonstrated in this novel model, which allows quantitative evaluation of therapeutic delivery.
Collapse
Affiliation(s)
- Kathryn E Hitchcock
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
de Wet H, Fotinou C, Amad N, Dreger M, Ashcroft FM. The ATPase activities of sulfonylurea receptor 2A and sulfonylurea receptor 2B are influenced by the C-terminal 42 amino acids. FEBS J 2010. [DOI: 10.1111/j.1742-4658.2010.07675.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
22
|
ATP-binding cassette proteins involved in glucose and lipid homeostasis. Biosci Biotechnol Biochem 2010; 74:899-907. [PMID: 20460728 DOI: 10.1271/bbb.90921] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glucose and lipids are essential to the body, but excess glucose or lipids lead to metabolic syndrome. ATP-binding cassette (ABC) proteins are involved in the homeostasis of glucose and lipid in that they regulate insulin secretion and remove excess cholesterol from the body. Sulfonylurea receptor (SUR) is a subunit of the ATP-sensitive potassium channels, which regulate insulin secretion from pancreatic beta-cells by sensing cellular metabolic levels. ABCG1 removes excess cholesterol from peripheral tissues and functions in reverse cholesterol transport to the liver. ABCG5 and ABCG8 suppress the absorption of cholesterol in the intestine and exclude cholesterol from the liver to the bile duct. ABCG1 and ABCG4, expressed in the central nervous system, play roles in lipid metabolism in the brain. These ABC proteins are targets of drugs and functional foods to cure and prevent diabetes, hyperlipidemia, and neurodegenerative diseases. In this review, recent knowledge of the physiological function and regulation of ABC proteins in the homeostasis of glucose and lipids is discussed.
Collapse
|
23
|
Amann T, Schell S, Kühner P, Winkler M, Schwanstecher M, Russ U, Quast U. Substitution of the Walker A lysine by arginine in the nucleotide-binding domains of sulphonylurea receptor SUR2B: effects on ligand binding and channel activity. Naunyn Schmiedebergs Arch Pharmacol 2010; 381:507-16. [PMID: 20352196 DOI: 10.1007/s00210-010-0510-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 02/28/2010] [Indexed: 10/19/2022]
Abstract
Sulphonylurea receptors (SURs) serve as regulatory subunits of ATP-sensitive K(+) channels. SURs are members of the ATP-binding cassette (ABC) protein superfamily and contain two conserved nucleotide-binding domains (NBDs) which bind and hydrolyse MgATP; in addition, they carry the binding sites for the sulphonylureas like glibenclamide (GBC) which close the channel and for the K(ATP) channel openers such as P1075. Here we have exchanged the conserved Lys in the Walker A motif by Arg in both NBDs of SUR2B, the regulatory subunit of the vascular K(ATP) channel. Then the effect of the mutation on the ATPase-dependent binding of GBC and P1075 to SUR2B and on the activity of the recombinant vascular (Kir6.1/SUR2B) channel was assessed. Surprisingly, in the absence of MgATP, the mutation weakened binding of P1075 and the extent of allosteric inhibition of GBC binding by P1075. The mutation abolished most, but not all, of the MgATP effects on the binding of GBC and P1075 and prevented nucleotide-induced activation of the channel which relies on SUR reaching the posthydrolytic (MgADP-bound) state; the mutant channel was, however, opened by P1075 at higher concentrations. The data provide evidence that mutant SUR2B binds MgATP but that the posthydrolytic state is insufficiently populated. This suggests that the mutation locks SUR2B in an MgATP-binding prehydrolytic-like state; binding of P1075 may induce a posthydrolytic-like conformation to open the channel.
Collapse
Affiliation(s)
- Tobias Amann
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard-Karls-University Hospitals and Clinics, University of Tübingen, Wilhelmstr. 56, 72074, Tübingen, Germany
| | | | | | | | | | | | | |
Collapse
|
24
|
Hibino H, Inanobe A, Furutani K, Murakami S, Findlay I, Kurachi Y. Inwardly rectifying potassium channels: their structure, function, and physiological roles. Physiol Rev 2010; 90:291-366. [PMID: 20086079 DOI: 10.1152/physrev.00021.2009] [Citation(s) in RCA: 1074] [Impact Index Per Article: 76.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Inwardly rectifying K(+) (Kir) channels allow K(+) to move more easily into rather than out of the cell. They have diverse physiological functions depending on their type and their location. There are seven Kir channel subfamilies that can be classified into four functional groups: classical Kir channels (Kir2.x) are constitutively active, G protein-gated Kir channels (Kir3.x) are regulated by G protein-coupled receptors, ATP-sensitive K(+) channels (Kir6.x) are tightly linked to cellular metabolism, and K(+) transport channels (Kir1.x, Kir4.x, Kir5.x, and Kir7.x). Inward rectification results from pore block by intracellular substances such as Mg(2+) and polyamines. Kir channel activity can be modulated by ions, phospholipids, and binding proteins. The basic building block of a Kir channel is made up of two transmembrane helices with cytoplasmic NH(2) and COOH termini and an extracellular loop which folds back to form the pore-lining ion selectivity filter. In vivo, functional Kir channels are composed of four such subunits which are either homo- or heterotetramers. Gene targeting and genetic analysis have linked Kir channel dysfunction to diverse pathologies. The crystal structure of different Kir channels is opening the way to understanding the structure-function relationships of this simple but diverse ion channel family.
Collapse
Affiliation(s)
- Hiroshi Hibino
- Department of Pharmacology, Graduate School of Medicine and The Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan
| | | | | | | | | | | |
Collapse
|
25
|
Arrell DK, Zlatkovic J, Kane GC, Yamada S, Terzic A. ATP-sensitive K+ channel knockout induces cardiac proteome remodeling predictive of heart disease susceptibility. J Proteome Res 2010; 8:4823-34. [PMID: 19673485 DOI: 10.1021/pr900561g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Forecasting disease susceptibility requires detection of maladaptive signatures prior to onset of overt symptoms. A case-in-point are cardiac ATP-sensitive K+ (K(ATP)) channelopathies, for which the substrate underlying disease vulnerability remains to be identified. Resolving molecular pathobiology, even for single genetic defects, mandates a systems platform to reliably diagnose disease predisposition. High-throughput proteomic analysis was here integrated with network biology to decode consequences of Kir6.2 K(ATP) channel pore deletion. Differential two-dimensional gel electrophoresis reproducibly resolved >800 protein species from hearts of asymptomatic wild-type and Kir6.2-knockout counterparts. K(ATP) channel ablation remodeled the cardiac proteome, significantly altering 71 protein spots, from which 102 unique identities were assigned following hybrid linear ion trap quadrupole-Orbitrap tandem mass spectrometry. Ontological annotation stratified the K(ATP) channel-dependent protein cohort into a predominant bioenergetic module (63 resolved identities), with additional focused sets representing signaling molecules (6), oxidoreductases (8), chaperones (6), and proteins involved in catabolism (6), cytostructure (8), and transcription and translation (5). Protein interaction mapping, in conjunction with expression level changes, localized a K(ATP) channel-associated subproteome within a nonstochastic scale-free network. Global assessment of the K(ATP) channel deficient environment verified the primary impact on metabolic pathways and revealed overrepresentation of markers associated with cardiovascular disease. Experimental imposition of graded stress precipitated exaggerated structural and functional myocardial defects in the Kir6.2-knockout, decreasing survivorship and validating the forecast of disease susceptibility. Proteomic cartography thus provides an integral view of molecular remodeling in the heart induced by K(ATP) channel deletion, establishing a systems approach that predicts outcome at a presymptomatic stage.
Collapse
Affiliation(s)
- D Kent Arrell
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
| | | | | | | | | |
Collapse
|
26
|
Park S, Terzic A. Quaternary structure of KATP channel SUR2A nucleotide binding domains resolved by synchrotron radiation X-ray scattering. J Struct Biol 2010; 169:243-51. [PMID: 19919849 PMCID: PMC2818519 DOI: 10.1016/j.jsb.2009.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 10/11/2009] [Accepted: 11/10/2009] [Indexed: 01/03/2023]
Abstract
Heterodimeric nucleotide binding domains NBD1/NBD2 distinguish the ATP-binding cassette protein SUR2A, a recognized regulatory subunit of cardiac ATP-sensitive K(+) (K(ATP)) channels. The tandem function of these core domains ensures metabolism-dependent gating of the Kir6.2 channel pore, yet their structural arrangement has not been resolved. Here, purified monodisperse and interference-free recombinant particles were subjected to synchrotron radiation small-angle X-ray scattering (SAXS) in solution. Intensity function analysis of SAXS profiles resolved NBD1 and NBD2 as octamers. Implemented by ab initio simulated annealing, shape determination prioritized an oblong envelope wrapping NBD1 and NBD2 with respective dimensions of 168x80x37A(3) and 175x81x37A(3) based on symmetry constraints, validated by atomic force microscopy. Docking crystal structure homology models against SAXS data reconstructed the NBD ensemble surrounding an inner cleft suitable for Kir6.2 insertion. Human heart disease-associated mutations introduced in silico verified the criticality of the mapped protein-protein interface. The resolved quaternary structure delineates thereby a macromolecular arrangement of K(ATP) channel SUR2A regulatory domains.
Collapse
Affiliation(s)
- Sungjo Park
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Departments of Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, MN 55905, USA
| | | |
Collapse
|
27
|
Human K(ATP) channelopathies: diseases of metabolic homeostasis. Pflugers Arch 2009; 460:295-306. [PMID: 20033705 PMCID: PMC2883927 DOI: 10.1007/s00424-009-0771-y] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 11/30/2009] [Indexed: 10/27/2022]
Abstract
Assembly of an inward rectifier K+ channel pore (Kir6.1/Kir6.2) and an adenosine triphosphate (ATP)-binding regulatory subunit (SUR1/SUR2A/SUR2B) forms ATP-sensitive K+ (KATP) channel heteromultimers, widely distributed in metabolically active tissues throughout the body. KATP channels are metabolism-gated biosensors functioning as molecular rheostats that adjust membrane potential-dependent functions to match cellular energetic demands. Vital in the adaptive response to (patho)physiological stress, KATP channels serve a homeostatic role ranging from glucose regulation to cardioprotection. Accordingly, genetic variation in KATP channel subunits has been linked to the etiology of life-threatening human diseases. In particular, pathogenic mutations in KATP channels have been identified in insulin secretion disorders, namely, congenital hyperinsulinism and neonatal diabetes. Moreover, KATP channel defects underlie the triad of developmental delay, epilepsy, and neonatal diabetes (DEND syndrome). KATP channelopathies implicated in patients with mechanical and/or electrical heart disease include dilated cardiomyopathy (with ventricular arrhythmia; CMD1O) and adrenergic atrial fibrillation. A common Kir6.2 E23K polymorphism has been associated with late-onset diabetes and as a risk factor for maladaptive cardiac remodeling in the community-at-large and abnormal cardiopulmonary exercise stress performance in patients with heart failure. The overall mutation frequency within KATP channel genes and the spectrum of genotype-phenotype relationships remain to be established, while predicting consequences of a deficit in channel function is becoming increasingly feasible through systems biology approaches. Thus, advances in molecular medicine in the emerging field of human KATP channelopathies offer new opportunities for targeted individualized screening, early diagnosis, and tailored therapy.
Collapse
|
28
|
Remedi MS, Koster JC. K(ATP) channelopathies in the pancreas. Pflugers Arch 2009; 460:307-20. [PMID: 19921246 DOI: 10.1007/s00424-009-0756-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 10/20/2009] [Accepted: 10/23/2009] [Indexed: 12/14/2022]
Abstract
Adenosine-triphosphate-sensitive potassium channels (KATP) are regulated by adenosine nucleotides, and, thereby, couple cellular metabolism with electrical activity in multiple tissues including the pancreatic beta-cell. The critical involvement of KATP in insulin secretion is confirmed by the demonstration that inactivating and activating mutations in KATP underlie persistent hyperinsulinemia and neonatal diabetes mellitus, respectively, in both animal models and humans. In addition, a common variant in KATP represents a risk factor in the etiology of type 2 diabetes. This review focuses on the mechanistic basis by which KATP mutations underlie insulin secretory disorders and the implications of these findings for successful clinical intervention.
Collapse
Affiliation(s)
- Maria S Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
| | | |
Collapse
|
29
|
Nelson TJ, Martinez-Fernandez A, Terzic A. KCNJ11 knockout morula re-engineered by stem cell diploid aggregation. Philos Trans R Soc Lond B Biol Sci 2009; 364:269-76. [PMID: 18977736 DOI: 10.1098/rstb.2008.0179] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
KCNJ11-encoded Kir6.2 assembles with ATP-binding cassette sulphonylurea receptors to generate ATP-sensitive K+ (KATP) channel complexes. Expressed in tissues with dynamic metabolic flux, these evolutionarily conserved yet structurally and functionally unique heteromultimers serve as high-fidelity rheostats that adjust membrane potential-dependent cell functions to match energetic demand. Genetic defects in channel subunits disrupt the cellular homeostatic response to environmental stress, compromising organ tolerance in the adult. As maladaptation characterizes malignant KATP channelopathies, establishment of platforms to examine progression of KATP channel-dependent adaptive behaviour is warranted. Chimeras provide a powerful tool to assay the contribution of genetic variance to stress intolerance during prenatal or post-natal development. Here, KCNJ11 KATP channel gene knockout<-->wild-type chimeras were engineered through diploid aggregation. Integration of wild-type embryonic stem cells into zona pellucida-denuded morula derived from knockout embryos achieved varying degrees of incorporation of stress-tolerant tissue within the KATP channel-deficient background. Despite the stress-vulnerable phenotype of the knockout, ex vivo derived mosaic blastocysts tolerated intrauterine transfer and implantation, followed by full-term embryonic development in pseudopregnant surrogates to produce live chimeric offspring. The development of adult chimerism from the knockout<-->wild-type mosaic embryo offers thereby a new paradigm to probe the ecogenetic control of the KATP channel-dependent stress response.
Collapse
Affiliation(s)
- Timothy J Nelson
- Departments of Medicine, Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA
| | | | | |
Collapse
|
30
|
Karger AB, Park S, Reyes S, Bienengraeber M, Dyer RB, Terzic A, Alekseev AE. Role for SUR2A ED domain in allosteric coupling within the K(ATP) channel complex. ACTA ACUST UNITED AC 2008; 131:185-96. [PMID: 18299394 PMCID: PMC2248718 DOI: 10.1085/jgp.200709852] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Allosteric regulation of heteromultimeric ATP-sensitive potassium (KATP) channels is unique among protein systems as it implies transmission of ligand-induced structural adaptation at the regulatory SUR subunit, a member of ATP-binding cassette ABCC family, to the distinct pore-forming K+ (Kir6.x) channel module. Cooperative interaction between nucleotide binding domains (NBDs) of SUR is a prerequisite for KATP channel gating, yet pathways of allosteric intersubunit communication remain uncertain. Here, we analyzed the role of the ED domain, a stretch of 15 negatively charged aspartate/glutamate amino acid residues (948–962) of the SUR2A isoform, in the regulation of cardiac KATP channels. Disruption of the ED domain impeded cooperative NBDs interaction and interrupted the regulation of KATP channel complexes by MgADP, potassium channel openers, and sulfonylurea drugs. Thus, the ED domain is a structural component of the allosteric pathway within the KATP channel complex integrating transduction of diverse nucleotide-dependent states in the regulatory SUR subunit to the open/closed states of the K+-conducting channel pore.
Collapse
Affiliation(s)
- Amy B Karger
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Abstract
An explosion of work over the last decade has produced insight into the multiple hereditary causes of a nonimmunological form of diabetes diagnosed most frequently within the first 6 months of life. These studies are providing increased understanding of genes involved in the entire chain of steps that control glucose homeostasis. Neonatal diabetes is now understood to arise from mutations in genes that play critical roles in the development of the pancreas, of beta-cell apoptosis and insulin processing, as well as the regulation of insulin release. For the basic researcher, this work is providing novel tools to explore fundamental molecular and cellular processes. For the clinician, these studies underscore the need to identify the genetic cause underlying each case. It is increasingly clear that the prognosis, therapeutic approach, and genetic counseling a physician provides must be tailored to a specific gene in order to provide the best medical care.
Collapse
Affiliation(s)
- Lydia Aguilar-Bryan
- Pacific Northwest Diabetes Research Institute, 720 Broadway, Seattle, Washington 98122, USA.
| | | |
Collapse
|
32
|
Park S, Lim BBC, Perez-Terzic C, Mer G, Terzic A. Interaction of asymmetric ABCC9-encoded nucleotide binding domains determines KATP channel SUR2A catalytic activity. J Proteome Res 2008; 7:1721-8. [PMID: 18311911 DOI: 10.1021/pr7007847] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nucleotide binding domains (NBDs) secure ATP-binding cassette (ABC) transporter function. Distinct from traditional ABC transporters, ABCC9-encoded sulfonylurea receptors (SUR2A) form, with Kir6.2 potassium channels, ATP-sensitive K+ (K ATP) channel complexes. SUR2A contains ATPase activity harbored within NBD2 and, to a lesser degree, NBD1, with catalytically driven conformations exerting determinate linkage on the Kir6.2 channel pore. While homodomain interactions typify NBDs of conventional ABC transporters, heterodomain NBD interactions and their functional consequence have not been resolved for the atypical SUR2A protein. Here, nanoscale protein topography mapped assembly of monodisperse purified recombinant SUR2A NBD1/NBD2 domains, precharacterized by dynamic light scattering. Heterodomain interaction produced conformational rearrangements inferred by secondary structural change in circular dichroism, and validated by atomic force and transmission electron microscopy. Physical engagement of NBD1 with NBD2 translated into enhanced intrinsic ATPase activity. Molecular modeling delineated a complemental asymmetry of NBD1/NBD2 ATP-binding sites. Mutation in the predicted catalytic base residue, D834E of NBD1, altered NBD1 ATPase activity disrupting potentiation of catalytic behavior in the NBD1/NBD2 interactome. Thus, NBD1/NBD2 assembly, resolved by a panel of proteomic approaches, provides a molecular substrate that determines the optimal catalytic activity in SUR2A, establishing a paradigm for the structure-function relationship within the K ATP channel complex.
Collapse
Affiliation(s)
- Sungjo Park
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
| | | | | | | | | |
Collapse
|
33
|
Xie LH, John SA, Ribalet B, Weiss JN. Phosphatidylinositol-4,5-bisphosphate (PIP2) regulation of strong inward rectifier Kir2.1 channels: multilevel positive cooperativity. J Physiol 2008; 586:1833-48. [PMID: 18276733 DOI: 10.1113/jphysiol.2007.147868] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels are gated by the interaction of their cytoplasmic regions with membrane-bound phosphatidylinositol-4,5-bisphosphate (PIP(2)). In the present study, we examined how PIP(2) interaction regulates channel availability and channel openings to various subconductance levels (sublevels) as well as the fully open state in the strong inward rectifier Kir2.1 channel. Various Kir2.1 channel constructs were expressed in Xenopus oocytes and single channel or macroscopic currents were recorded from inside-out patches. The wild-type (WT) channel rarely visited the subconductance levels under control conditions. However, upon reducing Kir2.1 channel interaction with PIP(2) by a variety of interventions, including PIP(2) antibodies, screening PIP(2) with neomycin, or mutating PIP(2) binding sites (e.g. K188Q), visitation to the sublevels was markedly increased before channels were converted to an unavailable mode in which they did not open. No channel activity was detected in channels with the double mutation K188A/R189A, a mutant which exhibits extremely weak interaction with PIP(2). By linking subunits together in tandem dimers or tetramers containing mixtures of WT and K188A/R189A subunits, we demonstrate that one functional PIP(2)-interacting WT subunit is sufficient to convert channels from the unavailable to the available mode with a high open probability dominated by the fully open state, with similar kinetics as tetrameric WT channels. Occasional openings to sublevels become progressively less frequent as the number of WT subunits increases. Quantitative analysis reveals that the interaction of PIP(2) with WT subunits exerts strong positive cooperativity in both converting the channels from the unavailable to the available mode, and in promoting the fully open state over sublevels. We conclude that the interaction of PIP(2) with only one Kir2.1 subunit is sufficient for the channel to become available and to open to its full conductance state. Interaction with additional subunits exerts positive cooperativity at multiple levels to further enhance channel availability and promote the fully open state.
Collapse
Affiliation(s)
- Lai-Hua Xie
- Cardiovascular Research Laboratory, Rm 3645 MRL Building, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
| | | | | | | |
Collapse
|
34
|
Burke MA, Mutharasan RK, Ardehali H. The Sulfonylurea Receptor, an Atypical ATP-Binding Cassette Protein, and Its Regulation of the KATPChannel. Circ Res 2008; 102:164-76. [DOI: 10.1161/circresaha.107.165324] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Michael A. Burke
- From the Division of Cardiology, Feinberg Cardiovascular Institute, Northwestern University, Chicago, Ill
| | - R. Kannan Mutharasan
- From the Division of Cardiology, Feinberg Cardiovascular Institute, Northwestern University, Chicago, Ill
| | - Hossein Ardehali
- From the Division of Cardiology, Feinberg Cardiovascular Institute, Northwestern University, Chicago, Ill
| |
Collapse
|
35
|
Zingman LV, Alekseev AE, Hodgson-Zingman DM, Terzic A. ATP-sensitive potassium channels: metabolic sensing and cardioprotection. J Appl Physiol (1985) 2007; 103:1888-93. [PMID: 17641217 DOI: 10.1152/japplphysiol.00747.2007] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cardiovascular system operates under a wide scale of demands, ranging from conditions of rest to extreme stress. How the heart muscle matches rates of ATP production with utilization is an area of active investigation. ATP-sensitive potassium (K(ATP)) channels serve a critical role in the orchestration of myocardial energetic well-being. K(ATP) channel heteromultimers consist of inwardly-rectifying K(+) channel 6.2 and ATP-binding cassette sulfonylurea receptor 2A that translates local ATP/ADP levels, set by ATPases and phosphotransfer reactions, to the channel pore function. In cells in which the mobility of metabolites between intracellular microdomains is limited, coupling of phosphotransfer pathways with K(ATP) channels permits a high-fidelity transduction of nucleotide fluxes into changes in membrane excitability, matching energy demands with metabolic resources. This K(ATP) channel-dependent optimization of cardiac action potential duration preserves cellular energy balance at varying workloads. Mutations of K(ATP) channels result in disruption of the nucleotide signaling network and generate a stress-vulnerable phenotype with excessive susceptibility to injury, development of cardiomyopathy, and arrhythmia. Solving the mechanisms underlying the integration of K(ATP) channels into the cellular energy network will advance the understanding of endogenous cardioprotection and the development of strategies for the management of cardiovascular injury and disease progression.
Collapse
Affiliation(s)
- L V Zingman
- Univ. of Iowa, Carver College of Medicine, 285 Newton Rd., CBRB2296, Iowa City, IA 52242, USA.
| | | | | | | |
Collapse
|
36
|
de Wet H, Mikhailov MV, Fotinou C, Dreger M, Craig TJ, Vénien-Bryan C, Ashcroft FM. Studies of the ATPase activity of the ABC protein SUR1. FEBS J 2007; 274:3532-3544. [PMID: 17561960 DOI: 10.1111/j.1742-4658.2007.05879.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The ATP-sensitive potassium (K(ATP)) channel couples glucose metabolism to insulin secretion in pancreatic beta-cells. It comprises regulatory sulfonylurea receptor 1 and pore-forming Kir6.2 subunits. Binding and/or hydrolysis of Mg-nucleotides at the nucleotide-binding domains of sulfonylurea receptor 1 stimulates channel opening and leads to membrane hyperpolarization and inhibition of insulin secretion. We report here the first purification and functional characterization of sulfonylurea receptor 1. We also compared the ATPase activity of sulfonylurea receptor 1 with that of the isolated nucleotide-binding domains (fused to maltose-binding protein to improve solubility). Electron microscopy showed that nucleotide-binding domains purified as ring-like complexes corresponding to approximately 8 momomers. The ATPase activities expressed as maximal turnover rate [in nmol P(i).s(-1).(nmol protein)(-1)] were 0.03, 0.03, 0.13 and 0.08 for sulfonylurea receptor 1, nucleotide-binding domain 1, nucleotide-binding domain 2 and a mixture of nucleotide-binding domain 1 and nucleotide-binding domain 2, respectively. Corresponding K(m) values (in mm) were 0.1, 0.6, 0.65 and 0.56, respectively. Thus sulfonylurea receptor 1 has a lower K(m) than either of the isolated nucleotide-binding domains, and a lower maximal turnover rate than nucleotide-binding domain 2. Similar results were found with GTP, but the K(m) values were lower. Mutation of the Walker A lysine in nucleotide-binding domain 1 (K719A) or nucleotide-binding domain 2 (K1385M) inhibited the ATPase activity of sulfonylurea receptor 1 by 60% and 80%, respectively. Beryllium fluoride (K(i) 16 microm), but not MgADP, inhibited the ATPase activity of sulfonylurea receptor 1. In contrast, both MgADP and beryllium fluoride inhibited the ATPase activity of the nucleotide-binding domains. These data demonstrate that the ATPase activity of sulfonylurea receptor 1 differs from that of the isolated nucleotide-binding domains, suggesting that the transmembrane domains may influence the activity of the protein.
Collapse
Affiliation(s)
- Heidi de Wet
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Michael V Mikhailov
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Constantina Fotinou
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Mathias Dreger
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Tim J Craig
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Catherine Vénien-Bryan
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| | - Frances M Ashcroft
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, UKLaboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, UK
| |
Collapse
|
37
|
Gumina RJ, O'Cochlain DF, Kurtz CE, Bast P, Pucar D, Mishra P, Miki T, Seino S, Macura S, Terzic A. KATP channel knockout worsens myocardial calcium stress load in vivo and impairs recovery in stunned heart. Am J Physiol Heart Circ Physiol 2006; 292:H1706-13. [PMID: 17189350 DOI: 10.1152/ajpheart.01305.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gene knockout of the KCNJ11-encoded Kir6.2 ATP-sensitive K(+) (K(ATP)) channel implicates this stress-response element in the safeguard of cardiac homeostasis under imposed demand. K(ATP) channels are abundant in ventricular sarcolemma, where subunit expression appears to vary between the sexes. A limitation, however, in establishing the full significance of K(ATP) channels in the intact organism has been the inability to monitor in vivo the contribution of the channel to intracellular calcium handling and the superimposed effect of sex that ultimately defines heart function. Here, in vivo manganese-enhanced cardiac magnetic resonance imaging revealed, under dobutamine stress, a significantly greater accumulation of calcium in both male and female K(ATP) channel knockout (Kir6.2-KO) mice compared with sex- and age-matched wild-type (WT) counterparts, with greatest calcium load in Kir6.2-KO females. This translated, poststress, into a sustained contracture manifested by reduced end-diastolic volumes in K(ATP) channel-deficient mice. In response to ischemia-induced stunning, male and female Kir6.2-KO hearts demonstrated accelerated time to contracture and increased peak contracture compared with WT. The outcome on reperfusion, in both male and female Kir6.2-KO hearts, was a transient reduction in systolic performance, measured as rate-pressure product compared with WT, with protracted increase in left ventricular end-diastolic pressure, exaggerated in female knockout hearts, despite comparable leakage of creatine kinase across groups. Kir6.2-KO hearts were rescued from diastolic dysfunction by agents that target alternative pathways of calcium handling. Thus K(ATP) channel deficit confers a greater susceptibility to calcium overload in vivo, accentuated in female hearts, impairing contractile recovery under various conditions of high metabolic demand.
Collapse
Affiliation(s)
- Richard J Gumina
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Departments of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Yamada S, Kane GC, Behfar A, Liu XK, Dyer RB, Faustino RS, Miki T, Seino S, Terzic A. Protection conferred by myocardial ATP-sensitive K+ channels in pressure overload-induced congestive heart failure revealed in KCNJ11 Kir6.2-null mutant. J Physiol 2006; 577:1053-65. [PMID: 17038430 PMCID: PMC1890387 DOI: 10.1113/jphysiol.2006.119511] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ventricular load can precipitate development of the heart failure syndrome, yet the molecular components that control the cardiac adaptive response to imposed demand remain partly understood. Compromised ATP-sensitive K(+) (K(ATP)) channel function renders the heart vulnerable to stress, implicating this metabolic sensor in the homeostatic response that would normally prevent progression of cardiac disease. Here, pressure overload was imposed on the left ventricle by transverse aortic constriction in the wild-type and in mice lacking sarcolemmal K(ATP) channels through Kir6.2 pore knockout (Kir6.2-KO). Despite equivalent haemodynamic loads, within 30 min of aortic constriction, Kir6.2-KO showed an aberrant prolongation of action potentials with intracellular calcium overload and ATP depletion, whereas wild-type maintained ionic and energetic handling. On catheterization, constricted Kir6.2-KO displayed compromised myocardial performance with elevated left ventricular end-diastolic pressure, not seen in the wild-type. Glyburide, a K(ATP) channel inhibitor, reproduced the knockout phenotype in the wild-type, whereas the calcium channel antagonist, verapamil, prevented abnormal outcome in Kir6.2-KO. Within 48 h following aortic constriction, fulminant biventricular congestive heart failure, characterized by exercise intolerance, cardiac contractile dysfunction, hepatopulmonary congestion and ascites, halved the Kir6.2-KO cohort, while no signs of organ failure or mortality were seen in wild-type. Surviving Kir6.2-KO developed premature and exaggerated fibrotic myocardial hypertrophy associated with nuclear up-regulation of calcium-dependent pro-remodelling MEF2 and NF-AT pathways, precipitating chamber dilatation within 3 weeks. Thus, K(ATP) channels appear mandatory in acute and chronic cardiac adaptation to imposed haemodynamic load, protecting against congestive heart failure and death.
Collapse
Affiliation(s)
- Satsuki Yamada
- Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Prasad SM, Al-Dadah AS, Byrd GD, Flagg TP, Gomes J, Damiano RJ, Nichols CG, Lawton JS. Role of the sarcolemmal adenosine triphosphate-sensitive potassium channel in hyperkalemic cardioplegia-induced myocyte swelling and reduced contractility. Ann Thorac Surg 2006; 81:148-53. [PMID: 16368354 DOI: 10.1016/j.athoracsur.2005.06.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Revised: 06/14/2005] [Accepted: 06/20/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND Hyperkalemic cardioplegia (Plegisol) has been shown to result in myocyte swelling and reduced contractility. We have demonstrated the elimination of these detrimental effects by the addition of an adenosine triphosphate-sensitive K+ (KATP) channel opener. To examine whether the mitochondrial or sarcolemmal KATP channel might be involved, volume and contractility in isolated myocytes from wild-type mice and mice lacking the sarcolemmal KATP channel (Kir6.2-/-) were evaluated. METHODS Myocytes were perfused for 20 minutes each with control 37 degrees C Tyrode's solution, test solution, and then control solution. Test solutions were (n = 10 per group) either 9 degrees C Plegisol or 9 degrees C Plegisol with 100 micromol/L of diazoxide, a putative mitochondrial-specific KATP channel opener. Cell volume and contractility were measured by digital video microscopy at baseline and during the test solution and reexposure periods. RESULTS Myocytes from wild-type mice, perfused with 9 degrees C Plegisol, demonstrated significant cell swelling (11.2% +/- 0.4%; p < 0.01) and diminished contractility (32.5% +/- 9.6% reduction in percent shortening, 47.2% +/- 10.1% reduction in peak velocity of shortening, and 52.0% +/- 8.8% reduction in peak velocity of relengthening; p < 0.05) versus baseline. Cell swelling and diminished contractility were significantly reduced by the addition of diazoxide. In Kir6.2-/- myocytes, Plegisol caused a greatly reduced level of cell swelling (3.2% +/- 0.1%; p < 0.01), and this was unaffected by diazoxide. Contractility was unchanged in Kir6.2-/- myocytes after Plegisol. CONCLUSIONS The sarcolemmal KATP channel appears necessary for exaggerated cell swelling and reduced contractility to occur after hyperkalemic cardioplegia in mouse myocytes.
Collapse
Affiliation(s)
- Sandip M Prasad
- Division of Cardiothoracic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Jöns T, Wittschieber D, Beyer A, Meier C, Brune A, Thomzig A, Ahnert-Hilger G, Veh RW. K+-ATP-channel-related protein complexes: potential transducers in the regulation of epithelial tight junction permeability. J Cell Sci 2006; 119:3087-97. [PMID: 16820413 DOI: 10.1242/jcs.03041] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
K+-ATP channels are composed of an inwardly rectifying Kir6 subunit and an auxiliary sulfonylurea receptor (SUR) protein. The SUR subunits of Kir6 channels have been recognized as an ATPase, which appears to work as a mechanochemical device like other members of the ABC protein family. Thus, in spite of just gating ions, Kir6/Sur might, in addition, regulate completely different cellular systems. However, so far no model system was available to directly investigate this possibility. Using highly specific antibodies against Kir6.1-SUR2A and an in vitro model system of the rat small intestine, we describe a new function of the Kir6.1-SUR2A complex, namely the regulation of paracellular permeability. The Kir6.1-SUR2A complex localizes to regulated tight junctions in a variety of gastrointestinal, renal and liver tissues of rat, pig and human, whereas it is absent in the urothelium. Changes in paracellular permeability following food intake was investigated by incubating the lumen of morphological well-defined segments of rat small intestine with various amounts of glucose. Variations in the lumenal glucose concentrations and regulators of Kir6.1/SUR2A activity, such as tolbutamide or diazoxide, specifically modulate paracellular permeability. The data presented here shed new light on the physiological and pathophysiological role K+-ATP channels might have for the regulation of tight junctions.
Collapse
Affiliation(s)
- Thomas Jöns
- Charité-Universitätsmedizin Berlin, Centrum für Anatomie, Institut für Integrative Neuroanatomie, Philippstr. 12, 10115 Berlin, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Abstract
In responding to cytoplasmic nucleotide levels, ATP-sensitive potassium (K(ATP)) channel activity provides a unique link between cellular energetics and electrical excitability. Over the past ten years, a steady drumbeat of crystallographic and electrophysiological studies has led to detailed structural and kinetic models that define the molecular basis of channel activity. In parallel, the uncovering of disease-causing mutations of K(ATP) has led to an explanation of the molecular basis of disease and, in turn, to a better understanding of the structural basis of channel function.
Collapse
Affiliation(s)
- Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, Missouri 63110, USA.
| |
Collapse
|
42
|
Minoretti P, Falcone C, Aldeghi A, Olivieri V, Mori F, Emanuele E, Calcagnino M, Geroldi D. A novel Val734Ile variant in the ABCC9 gene associated with myocardial infarction. Clin Chim Acta 2006; 370:124-8. [PMID: 16563363 DOI: 10.1016/j.cca.2006.02.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Revised: 02/01/2006] [Accepted: 02/01/2006] [Indexed: 11/15/2022]
Abstract
BACKGROUND Alterations in coronary vasomotor tone are deemed to play an important role in myocardial infarction (MI), and the ATP-binding cassette transporter C9-ABCC9-may be involved in the regulation of coronary artery vasomotility. We sought to determine whether genetic variations in the coding sequence of ABCC9 gene could be associated with precocious MI (myocardial infarction before the age of 60 years) in humans. METHODS In this study, we screened using PCR-SSCP analysis the entire coding region of the ABCC9 gene in 45 patients with precocious MI and 45 age- and gender-matched controls. RESULTS A novel missense mutation, Val734Ile in exon 17, was detected in one MI patient. We therefore analyzed by PCR-RFLPs the frequency of this nonsynonymous change in a large Italian cohort of precocious MI patients (n=584) and healthy comparison subjects (n=873). After allowance for the potential confounding effects of age, gender, and established cardiovascular risk factors, multivariate logistic regression analysis revealed that carriers of the rare 734Ile allele would have a 6.40-fold risk of suffering MI before the age of 60 years as compared to controls (95% CI=1.58-25.90, P=0.009). CONCLUSIONS Taken together, our results provide the first important evidence that the newly discovered 734Ile allele in ABCC9 might influence susceptibility to precocious MI in our population.
Collapse
Affiliation(s)
- Piercarlo Minoretti
- Department of Cardiology, Alessandro Manzoni Hospital of Lecco, Lecco, Italy
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Frelet A, Klein M. Insight in eukaryotic ABC transporter function by mutation analysis. FEBS Lett 2006; 580:1064-84. [PMID: 16442101 DOI: 10.1016/j.febslet.2006.01.024] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/21/2022]
Abstract
With regard to structure-function relations of ATP-binding cassette (ABC) transporters several intriguing questions are in the spotlight of active research: Why do functional ABC transporters possess two ATP binding and hydrolysis domains together with two ABC signatures and to what extent are the individual nucleotide-binding domains independent or interacting? Where is the substrate-binding site and how is ATP hydrolysis functionally coupled to the transport process itself? Although much progress has been made in the elucidation of the three-dimensional structures of ABC transporters in the last years by several crystallographic studies including novel models for the nucleotide hydrolysis and translocation catalysis, site-directed mutagenesis as well as the identification of natural mutations is still a major tool to evaluate effects of individual amino acids on the overall function of ABC transporters. Apart from alterations in characteristic sequence such as Walker A, Walker B and the ABC signature other parts of ABC proteins were subject to detailed mutagenesis studies including the substrate-binding site or the regulatory domain of CFTR. In this review, we will give a detailed overview of the mutation analysis reported for selected ABC transporters of the ABCB and ABCC subfamilies, namely HsCFTR/ABCC7, HsSUR/ABCC8,9, HsMRP1/ABCC1, HsMRP2/ABCC2, ScYCF1 and P-glycoprotein (Pgp)/MDR1/ABCB1 and their effects on the function of each protein.
Collapse
Affiliation(s)
- Annie Frelet
- Zurich Basel Plant Science Center, University of Zurich, Plant Biology, Zollikerstrasse 107, CH-8008 Zurich, Switzerland
| | | |
Collapse
|
44
|
Tammaro P, Proks P, Ashcroft FM. Functional effects of naturally occurring KCNJ11 mutations causing neonatal diabetes on cloned cardiac KATP channels. J Physiol 2005; 571:3-14. [PMID: 16339180 PMCID: PMC1805653 DOI: 10.1113/jphysiol.2005.099168] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
ATP-sensitive K+ (K(ATP)) channels are hetero-octamers of inwardly rectifying K+ channel (Kir6.2) and sulphonylurea receptor subunits (SUR1 in pancreatic beta-cells, SUR2A in heart). Heterozygous gain-of-function mutations in Kir6.2 cause neonatal diabetes, which may be accompanied by epilepsy and developmental delay. However, despite the importance of K(ATP) channels in the heart, patients have no obvious cardiac problems. We examined the effects of adenine nucleotides on K(ATP) channels containing wild-type or mutant (Q52R, R201H) Kir6.2 plus either SUR1 or SUR2A. In the absence of Mg2+, both mutations reduced ATP inhibition of SUR1- and SUR2A-containing channels to similar extents, but when Mg2+ was present ATP blocked mutant channels containing SUR1 much less than SUR2A channels. Mg-nucleotide activation of SUR1, but not SUR2A, channels was markedly increased by the R201H mutation. Both mutations also increased resting whole-cell K(ATP) currents through heterozygous SUR1-containing channels to a greater extent than for heterozygous SUR2A-containing channels. The greater ATP inhibition of mutant Kir6.2/SUR2A than of Kir6.2/SUR1 can explain why gain-of-function Kir6.2 mutations manifest effects in brain and beta-cells but not in the heart.
Collapse
Affiliation(s)
- Paolo Tammaro
- University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
| | | | | |
Collapse
|
45
|
Proks P, Girard C, Ashcroft FM. Functional effects of KCNJ11 mutations causing neonatal diabetes: enhanced activation by MgATP. Hum Mol Genet 2005; 14:2717-26. [PMID: 16087682 DOI: 10.1093/hmg/ddi305] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Recent studies have shown that heterozygous mutations in KCNJ11, which encodes Kir6.2, the pore-forming subunit of the ATP-sensitive potassium (K(ATP)) channel, cause permanent neonatal diabetes either alone (R201C, R201H) or in association with developmental delay, muscle weakness and epilepsy (V59G,V59M). Functional analysis in the absence of Mg2+, to isolate the inhibitory effects of ATP on Kir6.2, showed that both types of mutation reduce channel inhibition by ATP. However, in pancreatic beta-cells, K(ATP) channel activity is governed by the balance between ATP inhibition via Kir6.2 and Mg-nucleotide stimulation mediated by an auxiliary subunit, the sulphonylurea receptor SUR1. We therefore studied the MgATP sensitivity of KCNJ11 mutant K(ATP) channels expressed in Xenopus oocytes. In contrast to wild-type channels, Mg2+ dramatically reduced the ATP sensitivity of heterozygous R201C, R201H, V59M and V59G channels. This effect was predominantly mediated via the nucleotide-binding domains of SUR1 and resulted from an enhanced stimulatory action of MgATP. Our results therefore demonstrate that KCNJ11 mutations increase the current magnitude of heterozygous K(ATP) channels in two ways: by increasing MgATP activation and by decreasing ATP inhibition. They further show that the fraction of unblocked K(ATP) current at physiological MgATP concentrations correlates with the severity of the clinical phenotype.
Collapse
Affiliation(s)
- Peter Proks
- University Laboratory of Physiology, Oxford University, Parks Road, Oxford OX1 3PT, UK
| | | | | |
Collapse
|
46
|
Alekseev AE, Hodgson DM, Karger AB, Park S, Zingman LV, Terzic A. ATP-sensitive K+ channel channel/enzyme multimer: metabolic gating in the heart. J Mol Cell Cardiol 2005; 38:895-905. [PMID: 15910874 PMCID: PMC2736952 DOI: 10.1016/j.yjmcc.2005.02.022] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Accepted: 02/16/2005] [Indexed: 10/25/2022]
Abstract
Cardiac ATP-sensitive K(+) (K(ATP)) channels, gated by cellular metabolism, are formed by association of the inwardly rectifying potassium channel Kir6.2, the potassium conducting subunit, and SUR2A, the ATP-binding cassette protein that serves as the regulatory subunit. Kir6.2 is the principal site of ATP-induced channel inhibition, while SUR2A regulates K(+) flux through adenine nucleotide binding and catalysis. The ATPase-driven conformations within the regulatory SUR2A subunit of the K(ATP) channel complex have determinate linkage with the states of the channel's pore. The probability and life-time of ATPase-induced SUR2A intermediates, rather than competitive nucleotide binding alone, defines nucleotide-dependent K(ATP) channel gating. Cooperative interaction, instead of independent contribution of individual nucleotide binding domains within the SUR2A subunit, serves a decisive role in defining K(ATP) channel behavior. Integration of K(ATP) channels with the cellular energetic network renders these channel/enzyme heteromultimers high-fidelity metabolic sensors. This vital function is facilitated through phosphotransfer enzyme-mediated transmission of controllable energetic signals. By virtue of coupling with cellular energetic networks and the ability to decode metabolic signals, K(ATP) channels set membrane excitability to match demand for homeostatic maintenance. This new paradigm in the operation of an ion channel multimer is essential in providing the basis for K(ATP) channel function in the cardiac cell, and for understanding genetic defects associated with life-threatening diseases that result from the inability of the channel complex to optimally fulfill its physiological role.
Collapse
Affiliation(s)
- Alexey E Alekseev
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
| | | | | | | | | | | |
Collapse
|
47
|
Yamada M, Kurachi Y. A functional role of the C-terminal 42 amino acids of SUR2A and SUR2B in the physiology and pharmacology of cardiovascular ATP-sensitive K(+) channels. J Mol Cell Cardiol 2005; 39:1-6. [PMID: 15978900 DOI: 10.1016/j.yjmcc.2004.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2004] [Revised: 07/19/2004] [Accepted: 11/12/2004] [Indexed: 11/16/2022]
Abstract
The ATP-sensitive K(+) (K(ATP)) channel is composed of four pore-forming Kir6.2 subunits and four sulfonylurea receptors (SUR). Intracellular ATP inhibits K(ATP) channels through Kir6.2. SUR is an ABC protein bearing transmembrane domains and two nucleotide-binding domains (NBD1 and NBD2). SUR increases the open probability of K(ATP) channels by interacting with ATP and ADP through NBDs and with K(+) channel openers such as nicorandil through its transmembrane domain. Because NBDs and the drug receptor allosterically interact with each other, nucleotides and drugs probably activate K(ATP) channels by causing the same conformational change of SUR. SUR2A and SUR2B have the identical drug receptor and NBDs and differ only in the C-terminal 42 amino acids (C42). Nonetheless, nicorandil ~100 times more potently activates SUR2B/Kir6.2 than SUR2A/Kir6.2 channels. Based on our allosteric model, we have analyzed the interaction between NBDs and the drug receptor in SUR2A and SUR2B and found that both nucleotide-bound NBD1 and NBD2 more strongly induce the conformational change in SUR2B than SUR2A. Therefore, C42 modulates the function of not only NBD2 which is close to C42 in a primary structure but NBD1 which is more than 630 amino acid N-terminal to C42. This raises the possibility that in the presence of nucleotides, NBD1 and NBD2 dimerize to induce the conformational change and that the dimerization enables C42 to gain access to both NBDs. Modulation of the nucleotide-NBD1 and -NBD2 interactions by C42 would determine the stability of the nucleotide-dependent dimer and thus, the physiological and pharmacological properties of K(ATP) channels.
Collapse
Affiliation(s)
- Mitsuhiko Yamada
- Department of Pharmacology II, Graduate School of Medicine, Faculty of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
| | | |
Collapse
|
48
|
Selivanov VA, Alekseev AE, Hodgson DM, Dzeja PP, Terzic A. Nucleotide-gated KATP channels integrated with creatine and adenylate kinases: amplification, tuning and sensing of energetic signals in the compartmentalized cellular environment. Mol Cell Biochem 2004; 256-257:243-56. [PMID: 14977185 PMCID: PMC2760266 DOI: 10.1023/b:mcbi.0000009872.35940.7d] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Transmission of energetic signals to membrane sensors, such as the ATP-sensitive K+ (KATP) channel, is vital for cellular adaptation to stress. Yet, cell compartmentation implies diffusional hindrances that hamper direct reception of cytosolic energetic signals. With high intracellular ATP levels, KATP channels may sense not bulk cytosolic, but rather local submembrane nucleotide concentrations set by membrane ATPases and phosphotransfer enzymes. Here, we analyzed the role of adenylate kinase and creatine kinase phosphotransfer reactions in energetic signal transmission over the strong diffusional barrier in the submembrane compartment, and translation of such signals into a nucleotide response detectable by KATP channels. Facilitated diffusion provided by creatine kinase and adenylate kinase phosphotransfer dissipated nucleotide gradients imposed by membrane ATPases, and shunted diffusional restrictions. Energetic signals, simulated as deviation of bulk ATP from its basal level, were amplified into an augmented nucleotide response in the submembrane space due to failure under stress of creatine kinase to facilitate nucleotide diffusion. Tuning of creatine kinase-dependent amplification of the nucleotide response was provided by adenylate kinase capable of adjusting the ATP/ADP ratio in the submembrane compartment securing adequate KATP channel response in accord with cellular metabolic demand. Thus, complementation between creatine kinase and adenylate kinase systems, here predicted by modeling and further supported experimentally, provides a mechanistic basis for metabolic sensor function governed by alterations in intracellular phosphotransfer fluxes.
Collapse
Affiliation(s)
- Vitaliy A Selivanov
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Guggenheim, Rochester, MN 55905, USA
| | | | | | | | | |
Collapse
|
49
|
Hodgson DM, Behfar A, Zingman LV, Kane GC, Perez-Terzic C, Alekseev AE, Pucéat M, Terzic A. Stable benefit of embryonic stem cell therapy in myocardial infarction. Am J Physiol Heart Circ Physiol 2004; 287:H471-9. [PMID: 15277190 DOI: 10.1152/ajpheart.01247.2003] [Citation(s) in RCA: 182] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Conventional therapies for myocardial infarction attenuate disease progression without contributing significantly to repair. Because of the capacity for de novo cardiogenesis, embryonic stem cells are considered a potential source for myocardial regeneration, yet limited information is available on their ultimate therapeutic value. We treated infarcted rat hearts with CGR8 embryonic stem cells preexamined for cardiogenicity, serially probed left ventricular function, and determined final pathological outcome. Stem cell delivery generated new cardiomyocytes of embryonic stem cell origin that integrated with host myocardium within infarct regions. This resulted in a functional benefit within 3 wk that remained sustained over 12 wk of continuous follow-up and included a vigorous inotropic response to beta-adrenergic challenge. Integration of stem cell-derived cardiomyocytes was associated with normalized ventricular architecture, little scar, and a decrease in signs of myocardial necrosis. In contrast, sham-treated infarcted hearts exhibited ventricular cavity dilation and aneurysm formation, poor ventricular function, and a lack of response to beta-adrenergic stimulation. No evidence of graft rejection, ectopy, sudden cardiac death, or tumor formation was observed after therapy. These findings indicate that embryonic stem cells, through differentiation within the host myocardium, can contribute to a stable beneficial outcome on contractile function and ventricular remodeling in the infarcted heart.
Collapse
Affiliation(s)
- Denice M Hodgson
- Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Abstract
The sulphonylurea receptor (SUR) is a member of the ATP-binding cassette (ABC) family of membrane proteins. It functions as the regulatory subunit of the ATP-sensitive potassium (KATP) channel, which comprises SUR and Kir6.x proteins. Here, we review data demonstrating functional differences between the two nucleotide binding domains (NBDs) of SUR1. In addition, to explain the structural basis of these functional differences, we have constructed a molecular model of the NBD dimer of human SUR1. We discuss the experimental data in the context of this model, and show how the model can be used to design experiments aimed at elucidating the relationship between the structure and function of the KATP channel.
Collapse
Affiliation(s)
- Jeff D. Campbell
- University Laboratory of Physiology,
Parks Road, Oxford OX1 3PT,
UK
- Laboratory of Molecular Biophysics, Department of
Biochemistry, University of Oxford, Oxford OX1 3QU,
UK
| | - Mark S.P. Sansom
- Laboratory of Molecular Biophysics, Department of
Biochemistry, University of Oxford, Oxford OX1 3QU,
UK
| | - Frances M. Ashcroft
- University Laboratory of Physiology,
Parks Road, Oxford OX1 3PT,
UK
- Tel: +44 1865 272 478; Fax: +44 1865 272 469;
| |
Collapse
|