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Patton BL, Zhu P, ElSheikh A, Driggers CM, Shyng SL. Dynamic duo: Kir6 and SUR in K ATP channel structure and function. Channels (Austin) 2024; 18:2327708. [PMID: 38489043 PMCID: PMC10950283 DOI: 10.1080/19336950.2024.2327708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 01/14/2024] [Indexed: 03/17/2024] Open
Abstract
KATP channels are ligand-gated potassium channels that couple cellular energetics with membrane potential to regulate cell activity. Each channel is an eight subunit complex comprising four central pore-forming Kir6 inward rectifier potassium channel subunits surrounded by four regulatory subunits known as the sulfonylurea receptor, SUR, which confer homeostatic metabolic control of KATP gating. SUR is an ATP binding cassette (ABC) protein family homolog that lacks membrane transport activity but is essential for KATP expression and function. For more than four decades, understanding the structure-function relationship of Kir6 and SUR has remained a central objective of clinical significance. Here, we review progress in correlating the wealth of functional data in the literature with recent KATP cryoEM structures.
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Affiliation(s)
- Bruce L. Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Phillip Zhu
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Assmaa ElSheikh
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Camden M. Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
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2
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Kedia S, Awal NM, Seddon J, Marder E. Sulfonylurea receptor coupled conductances alter the performace of two central pattern generating circuits in Cancer borealis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.09.602760. [PMID: 39026863 PMCID: PMC11257524 DOI: 10.1101/2024.07.09.602760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Neuronal activity and energy supply must maintain a fine balance for neuronal fitness. Various channels of communication between the two could impact network output in different ways. Sulfonylurea receptors (SURs) are a modification of ATP-binding cassette proteins (ABCs) that confer ATP-dependent gating on their associated ion channels. They are widely expressed and link metabolic states directly to neuronal activity. The role they play varies in different circuits, both enabling bursting and inhibiting activity in pathological conditions. The crab, Cancer borealis, has central patterns generators (CPGs) that fire in rhythmic bursts nearly constantly and it is unknown how energy availability influences these networks. The pyloric network of the stomatogastric ganglion (STG) and cardiac ganglion (GC) control rhythmic contractions of the foregut and heart respectively. Pharmacological manipulation of SURs results in opposite effects in the two CPGs. Neuronal firing completely stops in the STG when SUR-associated channels are open, and firing increases when the channels are closed. This results from a decrease in the excitability of pyloric dilator (PD) neurons, which are a part of the pacemaker kernel. The neurons of the CG, paradoxically, increase firing within bursts when SUR-associated channels are opened, and bursting slows when SUR-associated channels are closed. The channel permeability and sensitivities analyses present novel SUR-conductance biophysics, which nevertheless change activity in ways reminiscent of the predominantly studied mammalian receptor/channels. We suggest that SUR-associated conductances allow different neurons to respond to energy states in different ways through a common mechanism.
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Affiliation(s)
- Sonal Kedia
- Biology Department and Volen Center, Brandeis University, Waltham, MA 02454
| | - Naziru M Awal
- Biology Department and Volen Center, Brandeis University, Waltham, MA 02454
| | - Jackie Seddon
- Biology Department and Volen Center, Brandeis University, Waltham, MA 02454
| | - Eve Marder
- Biology Department and Volen Center, Brandeis University, Waltham, MA 02454
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3
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Yang Y, Chen L. Functional dissection of KATP channel structures reveals the importance of a conserved interface. Structure 2024; 32:168-176.e2. [PMID: 38101402 DOI: 10.1016/j.str.2023.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 10/24/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023]
Abstract
ATP-sensitive potassium channels (KATP) are inhibited by ATP but activated by Mg-ADP, coupling the intracellular ATP/ADP ratio to the potassium conductance of the plasma membrane. Although there has been progress in determining the structure of KATP, the functional significance of the domain-domain interface in the gating properties of KATP channels remains incompletely understood. In this study, we define the structure of KATP as two modules: KATPcore and SURABC. Based on this model, we identified two functionally important interfaces between these two modules, namely interface I and interface II. Further structure-guided mutagenesis experiments indicate that destabilizing interface II by deleting ECL3 on the SUR1 subunit impairs KNtp-independent Mg-ADP activation, demonstrating the essential role of intramolecular interactions between KATPcore and SURABC in Mg-ADP activation. Additionally, interface II is functionally conserved between SUR1 and SUR2, and the hydrophobic residue F351 on ECL3 of SUR1 is crucial for maintaining the stability of this interface.
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Affiliation(s)
- Yaxiong Yang
- Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China
| | - Lei Chen
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China.
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4
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Stringer RN, Weiss N. Pathophysiology of ion channels in amyotrophic lateral sclerosis. Mol Brain 2023; 16:82. [PMID: 38102715 PMCID: PMC10722804 DOI: 10.1186/s13041-023-01070-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 12/11/2023] [Indexed: 12/17/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) stands as the most prevalent and severe form of motor neuron disease, affecting an estimated 2 in 100,000 individuals worldwide. It is characterized by the progressive loss of cortical, brainstem, and spinal motor neurons, ultimately resulting in muscle weakness and death. Although the etiology of ALS remains poorly understood in most cases, the remodelling of ion channels and alteration in neuronal excitability represent a hallmark of the disease, manifesting not only during the symptomatic period but also in the early pre-symptomatic stages. In this review, we delve into these alterations observed in ALS patients and preclinical disease models, and explore their consequences on neuronal activities. Furthermore, we discuss the potential of ion channels as therapeutic targets in the context of ALS.
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Affiliation(s)
- Robin N Stringer
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Norbert Weiss
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic.
- Center of Biosciences, Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia.
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5
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Kitamura S, Murao N, Yokota S, Shimizu M, Ono T, Seino Y, Suzuki A, Maejima Y, Shimomura K. Effect of fenofibrate and selective PPARα modulator (SPPARMα), pemafibrate on KATP channel activity and insulin secretion. BMC Res Notes 2023; 16:202. [PMID: 37697384 PMCID: PMC10494450 DOI: 10.1186/s13104-023-06489-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 09/01/2023] [Indexed: 09/13/2023] Open
Abstract
OBJECTIVE Insulin secretion is regulated by ATP-sensitive potassium (KATP) channels in pancreatic beta-cells. Peroxisome proliferator-activated receptors (PPAR) α ligands are clinically used to treat dyslipidemia. A PPARα ligand, fenofibrate, and PPARγ ligands troglitazone and 15-deoxy-∆12,14-prostaglandin J2 are known to close KATP channels and induce insulin secretion. The recently developed PPARα ligand, pemafibrate, became a new entry for treating dyslipidemia. Because pemafibrate is reported to improve glucose intolerance in mice treated with a high fat diet and a novel selective PPARα modulator, it may affect KATP channels or insulin secretion. RESULTS The effect of fenofibrate (100 µM) and pemafibrate (100 µM) on insulin secretion from MIN6 cells was measured by using batch incubation for 10 and 60 min in low (2 mM) and high (10 mM) glucose conditions. The application of fenofibrate for 10 min significantly increased insulin secretion in low glucose conditions. Pemafibrate failed to increase insulin secretion in all of the conditions experimented in this study. The KATP channel activity was measured by using whole-cell patch clamp technique. Although fenofibrate (100 µM) reduced the KATP channel current, the same concentration of pemafibrate had no effect. Both fenofibrate and pemafibrate had no effect on insulin mRNA expression.
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Affiliation(s)
- Shigeki Kitamura
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
- Department of Plastic and Reconstructive Surgery, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Naoya Murao
- Department of Endocrinology, Diabetes and Metabolism, Fujita Health University, Toyoake, Japan
| | - Shoko Yokota
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
| | - Masaru Shimizu
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
- Department of Neurology, Matsumura General Hospital, Iwaki, Japan
| | - Tomoyuki Ono
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
| | - Yusuke Seino
- Department of Endocrinology, Diabetes and Metabolism, Fujita Health University, Toyoake, Japan
| | - Atsushi Suzuki
- Department of Endocrinology, Diabetes and Metabolism, Fujita Health University, Toyoake, Japan
| | - Yuko Maejima
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
| | - Kenju Shimomura
- Department of Bioregulation and Pharmacological Medicine, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima, 960-1295 Japan
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6
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Walczewska-Szewc K, Nowak W. Structural Insights into ATP-Sensitive Potassium Channel Mechanics: A Role of Intrinsically Disordered Regions. J Chem Inf Model 2023; 63:1806-1818. [PMID: 36746748 PMCID: PMC10052335 DOI: 10.1021/acs.jcim.2c01196] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Commonly used techniques, such as CryoEM or X-ray, are not able to capture the structural reorganizations of disordered regions of proteins (IDR); therefore, it is difficult to assess their functions in proteins based exclusively on experiments. To fill this gap, we used computational molecular dynamics (MD) simulation methods to capture IDR dynamics and trace biological function-related interactions in the Kir6.2/SUR1 potassium channel. This ATP-sensitive octameric complex, one of the critical elements in the insulin secretion process in human pancreatic β-cells, has four to five large, disordered fragments. Using unique MD simulations of the full Kir6.2/SUR1 channel complex, we present an in-depth analysis of the dynamics of the disordered regions and discuss the possible functions they could have in this system. Our MD results confirmed the crucial role of the N-terminus of the Kir6.2 fragment and the L0-loop of the SUR1 protein in the transfer of mechanical signals between domains that trigger insulin release. Moreover, we show that the presence of IDRs affects natural ligand binding. Our research takes us one step further toward understanding the action of this vital complex.
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Affiliation(s)
- Katarzyna Walczewska-Szewc
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Wiesław Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, 87-100 Toruń, Poland
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7
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Driggers CM, Shyng SL. Mechanistic insights on KATP channel regulation from cryo-EM structures. J Gen Physiol 2022; 155:213723. [PMID: 36441147 PMCID: PMC9700523 DOI: 10.1085/jgp.202113046] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/19/2022] [Accepted: 11/08/2022] [Indexed: 11/29/2022] Open
Abstract
Gated by intracellular ATP and ADP, ATP-sensitive potassium (KATP) channels couple cell energetics with membrane excitability in many cell types, enabling them to control a wide range of physiological processes based on metabolic demands. The KATP channel is a complex of four potassium channel subunits from the Kir channel family, Kir6.1 or Kir6.2, and four sulfonylurea receptor subunits, SUR1, SUR2A, or SUR2B, from the ATP-binding cassette (ABC) transporter family. Dysfunction of KATP channels underlies several human diseases. The importance of these channels in human health and disease has made them attractive drug targets. How the channel subunits interact with one another and how the ligands interact with the channel to regulate channel activity have been long-standing questions in the field. In the past 5 yr, a steady stream of high-resolution KATP channel structures has been published using single-particle cryo-electron microscopy (cryo-EM). Here, we review the advances these structures bring to our understanding of channel regulation by physiological and pharmacological ligands.
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Affiliation(s)
- Camden M. Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR,Correspondence to Show-Ling Shyng:
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8
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Davis MJ, Kim HJ, Nichols CG. K ATP channels in lymphatic function. Am J Physiol Cell Physiol 2022; 323:C1018-C1035. [PMID: 35785984 PMCID: PMC9550566 DOI: 10.1152/ajpcell.00137.2022] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 11/22/2022]
Abstract
KATP channels function as negative regulators of active lymphatic pumping and lymph transport. This review summarizes and critiques the evidence for the expression of specific KATP channel subunits in lymphatic smooth muscle and endothelium, the roles that they play in normal lymphatic function, and their possible involvement in multiple diseases, including metabolic syndrome, lymphedema, and Cantú syndrome. For each of these topics, suggestions are made for directions for future research.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, Missouri
| | - Hae Jin Kim
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, Missouri
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
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9
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Redel-Traub G, Sampson KJ, Kass RS, Bohnen MS. Potassium Channels as Therapeutic Targets in Pulmonary Arterial Hypertension. Biomolecules 2022; 12:1341. [PMID: 36291551 PMCID: PMC9599705 DOI: 10.3390/biom12101341] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 09/16/2022] [Accepted: 09/18/2022] [Indexed: 12/08/2023] Open
Abstract
Pulmonary arterial hypertension (PAH) is a devastating disease with high morbidity and mortality. Deleterious remodeling in the pulmonary arterial system leads to irreversible arterial constriction and elevated pulmonary arterial pressures, right heart failure, and eventually death. The difficulty in treating PAH stems in part from the complex nature of disease pathogenesis, with several signaling compounds known to be involved (e.g., endothelin-1, prostacyclins) which are indeed targets of PAH therapy. Over the last decade, potassium channelopathies were established as novel causes of PAH. More specifically, loss-of-function mutations in the KCNK3 gene that encodes the two-pore-domain potassium channel KCNK3 (or TASK-1) and loss-of-function mutations in the ABCC8 gene that encodes a key subunit, SUR1, of the ATP-sensitive potassium channel (KATP) were established as the first two potassium channelopathies in human cohorts with pulmonary arterial hypertension. Moreover, voltage-gated potassium channels (Kv) represent a third family of potassium channels with genetic changes observed in association with PAH. While other ion channel genes have since been reported in association with PAH, this review focuses on KCNK3, KATP, and Kv potassium channels as promising therapeutic targets in PAH, with recent experimental pharmacologic discoveries significantly advancing the field.
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Affiliation(s)
- Gabriel Redel-Traub
- Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Kevin J. Sampson
- Department of Molecular Pharmacology and Therapeutics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Robert S. Kass
- Department of Molecular Pharmacology and Therapeutics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Michael S. Bohnen
- Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
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10
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Gu Y, Zhou C, Piao Z, Yuan H, Jiang H, Wei H, Zhou Y, Nan G, Ji X. Cerebral edema after ischemic stroke: Pathophysiology and underlying mechanisms. Front Neurosci 2022; 16:988283. [PMID: 36061592 PMCID: PMC9434007 DOI: 10.3389/fnins.2022.988283] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 08/01/2022] [Indexed: 11/30/2022] Open
Abstract
Ischemic stroke is associated with increasing morbidity and has become the main cause of death and disability worldwide. Cerebral edema is a serious complication arising from ischemic stroke. It causes an increase in intracranial pressure, rapid deterioration of neurological symptoms, and formation of cerebral hernia, and is an important risk factor for adverse outcomes after stroke. To date, the detailed mechanism of cerebral edema after stroke remains unclear. This limits advances in prevention and treatment strategies as well as drug development. This review discusses the classification and pathological characteristics of cerebral edema, the possible relationship of the development of cerebral edema after ischemic stroke with aquaporin 4, the SUR1-TRPM4 channel, matrix metalloproteinase 9, microRNA, cerebral venous reflux, inflammatory reactions, and cerebral ischemia/reperfusion injury. It also summarizes research on new therapeutic drugs for post-stroke cerebral edema. Thus, this review provides a reference for further studies and for clinical treatment of cerebral edema after ischemic stroke.
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Affiliation(s)
- Yuhang Gu
- Department of Neurology, China-Japan Union Hospital of Jilin University, Changchun, China
| | - Chen Zhou
- Beijing Institute of Brain Disorders, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Capital Medical University, Beijing, China
| | - Zhe Piao
- Department of Neurology, China-Japan Union Hospital of Jilin University, Changchun, China
| | - Honghua Yuan
- Department of Neurology, China-Japan Union Hospital of Jilin University, Changchun, China
| | - Huimin Jiang
- Beijing Institute of Brain Disorders, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Capital Medical University, Beijing, China
| | - Huimin Wei
- Advanced Innovation Center for Big Data-Based Precision Medicine, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yifan Zhou
- Beijing Institute of Brain Disorders, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Capital Medical University, Beijing, China
| | - Guangxian Nan
- Department of Neurology, China-Japan Union Hospital of Jilin University, Changchun, China
- *Correspondence: Guangxian Nan,
| | - Xunming Ji
- Beijing Institute of Brain Disorders, Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Capital Medical University, Beijing, China
- Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
- Xunming Ji,
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11
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Structural insights into the mechanism of pancreatic K ATP channel regulation by nucleotides. Nat Commun 2022; 13:2770. [PMID: 35589716 PMCID: PMC9120461 DOI: 10.1038/s41467-022-30430-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 04/28/2022] [Indexed: 11/17/2022] Open
Abstract
ATP-sensitive potassium channels (KATP) are metabolic sensors that convert the intracellular ATP/ADP ratio to the excitability of cells. They are involved in many physiological processes and implicated in several human diseases. Here we present the cryo-EM structures of the pancreatic KATP channel in both the closed state and the pre-open state, resolved in the same sample. We observe the binding of nucleotides at the inhibitory sites of the Kir6.2 channel in the closed but not in the pre-open state. Structural comparisons reveal the mechanism for ATP inhibition and Mg-ADP activation, two fundamental properties of KATP channels. Moreover, the structures also uncover the activation mechanism of diazoxide-type KATP openers. KATP channels are energy sensors. Here, authors report the Cryo-EM structures of pancreatic KATP in both the closed state and the pre-open state. These structures illuminate the mechanism of KATP channel regulation by the intracellular nucleotides.
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12
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A glibenclamide-sensitive TRPM4-mediated component of CA1 excitatory postsynaptic potentials appears in experimental autoimmune encephalomyelitis. Sci Rep 2022; 12:6000. [PMID: 35397639 PMCID: PMC8994783 DOI: 10.1038/s41598-022-09875-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 03/16/2022] [Indexed: 12/29/2022] Open
Abstract
The transient receptor potential melastatin 4 (TRPM4) channel contributes to disease severity in the murine experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis and to neuronal cell death in models of excitotoxicity and traumatic brain injury. As TRPM4 is activated by intracellular calcium and conducts monovalent cations, we hypothesized that TRPM4 may contribute to and boost excitatory synaptic transmission in CA1 pyramidal neurons of the hippocampus. Using single-spine calcium imaging and electrophysiology, we found no effect of the TRPM4 antagonists 9-phenanthrol and glibenclamide on synaptic transmission in hippocampal slices from healthy mice. In contrast, glibenclamide but not 9-phenanthrol reduced excitatory synaptic potentials in slices from EAE mice, an effect that was absent in slices from EAE mice lacking TRPM4. We conclude that TRPM4 plays little role in basal hippocampal synaptic transmission, but a glibenclamide-sensitive TRPM4-mediated contribution to excitatory postsynaptic responses is upregulated at the acute phase of EAE.
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13
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Zhou HL, Premont RT, Stamler JS. The manifold roles of protein S-nitrosylation in the life of insulin. Nat Rev Endocrinol 2022; 18:111-128. [PMID: 34789923 PMCID: PMC8889587 DOI: 10.1038/s41574-021-00583-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/08/2021] [Indexed: 02/04/2023]
Abstract
Insulin, which is released by pancreatic islet β-cells in response to elevated levels of glucose in the blood, is a critical regulator of metabolism. Insulin triggers the uptake of glucose and fatty acids into the liver, adipose tissue and muscle, and promotes the storage of these nutrients in the form of glycogen and lipids. Dysregulation of insulin synthesis, secretion, transport, degradation or signal transduction all cause failure to take up and store nutrients, resulting in type 1 diabetes mellitus, type 2 diabetes mellitus and metabolic dysfunction. In this Review, we make the case that insulin signalling is intimately coupled to protein S-nitrosylation, in which nitric oxide groups are conjugated to cysteine thiols to form S-nitrosothiols, within effectors of insulin action. We discuss the role of S-nitrosylation in the life cycle of insulin, from its synthesis and secretion in pancreatic β-cells, to its signalling and degradation in target tissues. Finally, we consider how aberrant S-nitrosylation contributes to metabolic diseases, including the roles of human genetic mutations and cellular events that alter S-nitrosylation of insulin-regulating proteins. Given the growing influence of S-nitrosylation in cellular metabolism, the field of metabolic signalling could benefit from renewed focus on S-nitrosylation in type 2 diabetes mellitus and insulin-related disorders.
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Affiliation(s)
- Hua-Lin Zhou
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Richard T Premont
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA
| | - Jonathan S Stamler
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
- Institute for Transformative Molecular Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, USA.
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14
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Zhao C, MacKinnon R. Molecular structure of an open human K ATP channel. Proc Natl Acad Sci U S A 2021; 118:e2112267118. [PMID: 34815345 PMCID: PMC8640745 DOI: 10.1073/pnas.2112267118] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2021] [Indexed: 11/18/2022] Open
Abstract
KATP channels are metabolic sensors that translate intracellular ATP/ADP balance into membrane excitability. The molecular composition of KATP includes an inward-rectifier potassium channel (Kir) and an ABC transporter-like sulfonylurea receptor (SUR). Although structures of KATP have been determined in many conformations, in all cases, the pore in Kir is closed. Here, we describe human pancreatic KATP (hKATP) structures with an open pore at 3.1- to 4.0-Å resolution using single-particle cryo-electron microscopy (cryo-EM). Pore opening is associated with coordinated structural changes within the ATP-binding site and the channel gate in Kir. Conformational changes in SUR are also observed, resulting in an area reduction of contact surfaces between SUR and Kir. We also observe that pancreatic hKATP exhibits the unique (among inward-rectifier channels) property of PIP2-independent opening, which appears to be correlated with a docked cytoplasmic domain in the absence of PIP2.
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Affiliation(s)
- Chen Zhao
- HHMI, The Rockefeller University, New York, NY 10065
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY 10065
| | - Roderick MacKinnon
- HHMI, The Rockefeller University, New York, NY 10065;
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY 10065
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15
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Jha RM, Rani A, Desai SM, Raikwar S, Mihaljevic S, Munoz-Casabella A, Kochanek PM, Catapano J, Winkler E, Citerio G, Hemphill JC, Kimberly WT, Narayan R, Sahuquillo J, Sheth KN, Simard JM. Sulfonylurea Receptor 1 in Central Nervous System Injury: An Updated Review. Int J Mol Sci 2021; 22:11899. [PMID: 34769328 PMCID: PMC8584331 DOI: 10.3390/ijms222111899] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/25/2021] [Accepted: 10/26/2021] [Indexed: 12/17/2022] Open
Abstract
Sulfonylurea receptor 1 (SUR1) is a member of the adenosine triphosphate (ATP)-binding cassette (ABC) protein superfamily, encoded by Abcc8, and is recognized as a key mediator of central nervous system (CNS) cellular swelling via the transient receptor potential melastatin 4 (TRPM4) channel. Discovered approximately 20 years ago, this channel is normally absent in the CNS but is transcriptionally upregulated after CNS injury. A comprehensive review on the pathophysiology and role of SUR1 in the CNS was published in 2012. Since then, the breadth and depth of understanding of the involvement of this channel in secondary injury has undergone exponential growth: SUR1-TRPM4 inhibition has been shown to decrease cerebral edema and hemorrhage progression in multiple preclinical models as well as in early clinical studies across a range of CNS diseases including ischemic stroke, traumatic brain injury, cardiac arrest, subarachnoid hemorrhage, spinal cord injury, intracerebral hemorrhage, multiple sclerosis, encephalitis, neuromalignancies, pain, liver failure, status epilepticus, retinopathies and HIV-associated neurocognitive disorder. Given these substantial developments, combined with the timeliness of ongoing clinical trials of SUR1 inhibition, now, another decade later, we review advances pertaining to SUR1-TRPM4 pathobiology in this spectrum of CNS disease-providing an overview of the journey from patch-clamp experiments to phase III trials.
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Affiliation(s)
- Ruchira M. Jha
- Department of Neurology, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (R.M.J.); (S.M.D.)
- Department of Translational Neuroscience, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (A.R.); (S.R.); (S.M.); (A.M.-C.)
- Department of Neurosurgery, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (J.C.); (E.W.)
| | - Anupama Rani
- Department of Translational Neuroscience, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (A.R.); (S.R.); (S.M.); (A.M.-C.)
| | - Shashvat M. Desai
- Department of Neurology, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (R.M.J.); (S.M.D.)
| | - Sudhanshu Raikwar
- Department of Translational Neuroscience, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (A.R.); (S.R.); (S.M.); (A.M.-C.)
| | - Sandra Mihaljevic
- Department of Translational Neuroscience, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (A.R.); (S.R.); (S.M.); (A.M.-C.)
| | - Amanda Munoz-Casabella
- Department of Translational Neuroscience, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (A.R.); (S.R.); (S.M.); (A.M.-C.)
| | - Patrick M. Kochanek
- Clinical and Translational Science Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA;
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Pediatrics, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Safar Center for Resuscitation Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Joshua Catapano
- Department of Neurosurgery, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (J.C.); (E.W.)
| | - Ethan Winkler
- Department of Neurosurgery, Barrow Neurological Institute and St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA; (J.C.); (E.W.)
| | - Giuseppe Citerio
- School of Medicine and Surgery, University of Milan-Bicocca, 20126 Milan, Italy;
- Neurointensive Care Unit, Department of Neuroscience, San Gerardo Hospital, ASST—Monza, 20900 Monza, Italy
| | - J. Claude Hemphill
- Department of Neurology, University of California, San Francisco, CA 94143, USA;
| | - W. Taylor Kimberly
- Division of Neurocritical Care and Center for Genomic Medicine, Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA;
| | - Raj Narayan
- Department of Neurosurgery, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, North Shore University Hospital, Manhasset, NY 11549, USA;
| | - Juan Sahuquillo
- Neurotrauma and Neurosurgery Research Unit (UNINN), Vall d’Hebron Research Institute (VHIR), 08035 Barcelona, Spain;
- Neurotraumatology and Neurosurgery Research Unit, Universitat Autònoma de Barcelona (UAB), 08193 Barcelona, Spain
- Department of Neurosurgery, Vall d’Hebron University Hospital, 08035 Barcelona, Spain
| | - Kevin N. Sheth
- Division of Neurocritical Care and Emergency Neurology, Department of Neurology, School of Medicine, Yale University, New Haven, CT 06510, USA;
| | - J. Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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16
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Sanchez Caballero L, Gorgogietas V, Arroyo MN, Igoillo-Esteve M. Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 359:139-256. [PMID: 33832649 DOI: 10.1016/bs.ircmb.2021.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Monogenetic forms of diabetes represent 1%-5% of all diabetes cases and are caused by mutations in a single gene. These mutations, that affect genes involved in pancreatic β-cell development, function and survival, or insulin regulation, may be dominant or recessive, inherited or de novo. Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes. The severity of their symptoms depends on the nature of the mutation, the function of the affected gene and, in some cases, the influence of additional genetic or environmental factors that modulate severity and penetrance. In some patients, diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects, among others. The age of diabetes onset may also vary from neonatal until early adulthood manifestations. Since the different mutations result in diverse clinical presentations, patients usually need different treatments that range from just diet and exercise, to the requirement of exogenous insulin or other hypoglycemic drugs, e.g., sulfonylureas or glucagon-like peptide 1 analogs to control their glycemia. As a consequence, awareness and correct diagnosis are crucial for the proper management and treatment of monogenic diabetes patients. In this chapter, we describe mutations causing different monogenic forms of diabetes associated with inadequate pancreas development or impaired β-cell function and survival, and discuss the molecular mechanisms involved in β-cell demise.
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Affiliation(s)
- Laura Sanchez Caballero
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Vyron Gorgogietas
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Maria Nicol Arroyo
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/
| | - Mariana Igoillo-Esteve
- ULB Center for Diabetes Research (UCDR), Université Libre de Bruxelles, Brussels, Belgium. http://www.ucdr.be/.
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17
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Bowman P, Mathews F, Barbetti F, Shepherd MH, Sanchez J, Piccini B, Beltrand J, Letourneau-Freiberg LR, Polak M, Greeley SAW, Rawlins E, Babiker T, Thomas NJ, De Franco E, Ellard S, Flanagan SE, Hattersley AT. Long-term Follow-up of Glycemic and Neurological Outcomes in an International Series of Patients With Sulfonylurea-Treated ABCC8 Permanent Neonatal Diabetes. Diabetes Care 2021; 44:35-42. [PMID: 33184150 PMCID: PMC7783935 DOI: 10.2337/dc20-1520] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 10/04/2020] [Indexed: 02/03/2023]
Abstract
OBJECTIVE ABCC8 mutations cause neonatal diabetes mellitus that can be transient (TNDM) or, less commonly, permanent (PNDM); ∼90% of individuals can be treated with oral sulfonylureas instead of insulin. Previous studies suggested that people with ABCC8-PNDM require lower sulfonylurea doses and have milder neurological features than those with KCNJ11-PNDM. However, these studies were short-term and included combinations of ABCC8-PNDM and ABCC8-TNDM. We aimed to assess the long-term glycemic and neurological outcomes in sulfonylurea-treated ABCC8-PNDM. RESEARCH DESIGN AND METHODS We studied all 24 individuals with ABCC8-PNDM diagnosed in the U.K., Italy, France, and U.S. known to transfer from insulin to sulfonylureas before May 2010. Data on glycemic control, sulfonylurea dose, adverse effects including hypoglycemia, and neurological features were analyzed using nonparametric statistical methods. RESULTS Long-term data were obtained for 21 of 24 individuals (median follow-up 10.0 [range 4.1-13.2] years). Eighteen of 21 remained on sulfonylureas without insulin at the most recent follow-up. Glycemic control improved on sulfonylureas (presulfonylurea vs. 1-year posttransfer HbA1c 7.2% vs. 5.7%, P = 0.0004) and remained excellent long-term (1-year vs. 10-year HbA1c 5.7% vs. 6.5%, P = 0.04), n = 16. Relatively high doses were used (1-year vs. 10-year dose 0.37 vs. 0.25 mg/kg/day glyburide, P = 0.50) without any severe hypoglycemia. Neurological features were reported in 13 of 21 individuals; these improved following sulfonylurea transfer in 7 of 13. The most common features were learning difficulties (52%), developmental delay (48%), and attention deficit hyperactivity disorder (38%). CONCLUSIONS Sulfonylurea treatment of ABCC8-PNDM results in excellent long-term glycemic control. Overt neurological features frequently occur and may improve with sulfonylureas, supporting early, rapid genetic testing to guide appropriate treatment and neurodevelopmental assessment.
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Affiliation(s)
- Pamela Bowman
- Exeter NIHR Clinical Research Facility, Royal Devon and Exeter NHS Foundation Trust, Exeter, U.K.
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Frances Mathews
- Exeter NIHR Clinical Research Facility, Royal Devon and Exeter NHS Foundation Trust, Exeter, U.K
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Rome Tor Vergata, Rome, Italy
- Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Maggie H Shepherd
- Exeter NIHR Clinical Research Facility, Royal Devon and Exeter NHS Foundation Trust, Exeter, U.K
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Janine Sanchez
- Miller School of Medicine, University of Miami, Miami, FL
| | - Barbara Piccini
- Regional Center for Pediatric Diabetes, Meyer University Children's Hospital, Florence, Italy
| | - Jacques Beltrand
- Service d'Endocrinologie, Gynécologie et Diabétologie Pédaitrique, APHP Centre, Université de Paris, Paris, France
- INSERM U1016, Paris, France
- Institut IMAGINE, Paris, France
| | | | - Michel Polak
- Service d'Endocrinologie, Gynécologie et Diabétologie Pédaitrique, APHP Centre, Université de Paris, Paris, France
- INSERM U1016, Paris, France
- Institut IMAGINE, Paris, France
| | | | - Eamon Rawlins
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Tarig Babiker
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Nicholas J Thomas
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Elisa De Franco
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Sian Ellard
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, U.K
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18
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Cohen MJ, Chirico WJ, Lipke PN. Through the back door: Unconventional protein secretion. Cell Surf 2020; 6:100045. [PMID: 33225116 PMCID: PMC7666356 DOI: 10.1016/j.tcsw.2020.100045] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 12/19/2022] Open
Abstract
Proteins are secreted from eukaryotic cells by several mechanisms besides the well-characterized classical secretory system. Proteins destined to enter the classical secretory system contain a signal peptide for translocation into the endoplasmic reticulum. However, many proteins lacking a signal peptide are secreted nonetheless. Contrary to conventional belief, these proteins are not just released as a result of membrane damage leading to cell leakage, but are actively packaged for secretion in alternative pathways. They are called unconventionally secreted proteins, and the best-characterized are from fungi and mammals. These proteins have extracellular functions including cell signaling, immune modulation, as well as moonlighting activities different from their well-described intracellular functions. Among the pathways for unconventional secretion are direct transfer across the plasma membrane, release within plasma membrane-derived microvesicles, use of elements of autophagy, or secretion from endosomal/multivesicular body-related components. We review the fungal and metazoan unconventional secretory pathways and their regulation, and propose experimental criteria to identify their mode of secretion.
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Affiliation(s)
- Michael J. Cohen
- The Graduate Center of the City University of New York, United States
- Biology Department, Brooklyn College of the City University of New York, United States
| | - William J. Chirico
- Department of Cell Biology, Molecular and Cellular Biology Program, SUNY Downstate Medical Center, United States
| | - Peter N. Lipke
- The Graduate Center of the City University of New York, United States
- Biology Department, Brooklyn College of the City University of New York, United States
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19
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Bordignon E, Seeger MA, Galazzo L, Meier G. From in vitro towards in situ: structure-based investigation of ABC exporters by electron paramagnetic resonance spectroscopy. FEBS Lett 2020; 594:3839-3856. [PMID: 33219535 DOI: 10.1002/1873-3468.14004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 10/30/2020] [Accepted: 11/15/2020] [Indexed: 12/12/2022]
Abstract
ATP-binding cassette (ABC) exporters have been studied now for more than four decades, and recent structural investigation has produced a large number of protein database entries. Yet, important questions about how ABC exporters function at the molecular level remain debated, such as which are the molecular recognition hotspots and the allosteric couplings dynamically regulating the communication between the catalytic cycle and the export of substrates. This conundrum mainly arises from technical limitations confining all research to in vitro analysis of ABC transporters in detergent solutions or embedded in membrane-mimicking environments. Therefore, a largely unanswered question is how ABC exporters operate in situ, namely in the native membrane context of a metabolically active cell. This review focuses on novel mechanistic insights into type I ABC exporters gained through a unique combination of structure determination, biochemical characterization, generation of conformation-specific nanobodies/sybodies and double electron-electron resonance.
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Affiliation(s)
- Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, Switzerland
| | - Laura Galazzo
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Gianmarco Meier
- Institute of Medical Microbiology, University of Zurich, Switzerland
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20
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Lewinson O, Orelle C, Seeger MA. Structures of ABC transporters: handle with care. FEBS Lett 2020; 594:3799-3814. [PMID: 33098660 PMCID: PMC7756565 DOI: 10.1002/1873-3468.13966] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 09/22/2020] [Accepted: 10/15/2020] [Indexed: 12/11/2022]
Abstract
In the past two decades, the ATP‐binding cassette (ABC) transporters' field has undergone a structural revolution. The importance of structural biology to the development of the field of ABC transporters cannot be overstated, as the ensemble of structures not only revealed the architecture of ABC transporters but also shaped our mechanistic view of these remarkable molecular machines. Nevertheless, we advocate that the mechanistic interpretation of the structures is not trivial and should be carried out with prudence. Herein, we bring several examples of structures of ABC transporters that merit re‐interpretation via careful comparison to experimental data. We propose that it is of the upmost importance to place new structures within the context of the available experimental data.
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Affiliation(s)
- Oded Lewinson
- Department of Molecular Microbiology and the Rappaport Institute for Medical Sciences, Faculty of Medicine, The Technion-Israel Institute of Technology, Haifa, Israel
| | - Cédric Orelle
- CNRS, Molecular Microbiology and Structural Biochemistry (MMSB, UMR 5086), University of Lyon, Lyon, France
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
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21
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Song L, Barrett DG, Cox KL, Efanov AM, Syed SK, Tomandl D, Willard FS. A High-Throughput Assay for the Pancreatic Islet Beta-Cell Potassium Channel: Use in the Pharmacological Characterization of Insulin Secretagogues Identified from Phenotypic Screening. Assay Drug Dev Technol 2020; 19:27-37. [PMID: 33164547 DOI: 10.1089/adt.2020.1011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Phenotypic screening is a neoclassical approach for drug discovery. We conducted phenotypic screening for insulin secretion enhancing agents using INS-1E insulinoma cells as a model system for pancreatic beta-cells. A principal regulator of insulin secretion in beta-cells is the metabolically regulated potassium channel Kir6.2/SUR1 complex. To characterize hit compounds, we developed an assay to quantify endogenous potassium channel activity in INS-1E cells. We quantified ligand-regulated potassium channel activity in INS-1E cells using fluorescence imaging and thallium flux. Potassium channel activity was metabolically regulated and coupled to insulin secretion. The pharmacology of channel opening agents (diazoxide) and closing agents (sulfonylureas) was used to validate the applicability of the assay. A precise high-throughput assay was enabled, and phenotypic screening hits were triaged to enable a higher likelihood of discovering chemical matter with novel and useful mechanisms of action.
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Affiliation(s)
- Luyan Song
- Quantitative Biology, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - David G Barrett
- Discovery Chemistry, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Karen L Cox
- Quantitative Biology, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Alexander M Efanov
- Diabetes and Complications Therapeutic Area, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Samreen K Syed
- Diabetes and Complications Therapeutic Area, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Dirk Tomandl
- Discovery Informatics, Lilly Research Laboratories, Indianapolis, Indiana, USA
| | - Francis S Willard
- Quantitative Biology, Lilly Research Laboratories, Indianapolis, Indiana, USA
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22
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Drug development in targeting ion channels for brain edema. Acta Pharmacol Sin 2020; 41:1272-1288. [PMID: 32855530 PMCID: PMC7609292 DOI: 10.1038/s41401-020-00503-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 08/02/2020] [Indexed: 12/18/2022] Open
Abstract
Cerebral edema is a pathological hallmark of various central nervous system (CNS) insults, including traumatic brain injury (TBI) and excitotoxic injury such as stroke. Due to the rigidity of the skull, edema-induced increase of intracranial fluid significantly complicates severe CNS injuries by raising intracranial pressure and compromising perfusion. Mortality due to cerebral edema is high. With mortality rates up to 80% in severe cases of stroke, it is the leading cause of death within the first week. Similarly, cerebral edema is devastating for patients of TBI, accounting for up to 50% mortality. Currently, the available treatments for cerebral edema include hypothermia, osmotherapy, and surgery. However, these treatments only address the symptoms and often elicit adverse side effects, potentially in part due to non-specificity. There is an urgent need to identify effective pharmacological treatments for cerebral edema. Currently, ion channels represent the third-largest target class for drug development, but their roles in cerebral edema remain ill-defined. The present review aims to provide an overview of the proposed roles of ion channels and transporters (including aquaporins, SUR1-TRPM4, chloride channels, glucose transporters, and proton-sensitive channels) in mediating cerebral edema in acute ischemic stroke and TBI. We also focus on the pharmacological inhibitors for each target and potential therapeutic strategies that may be further pursued for the treatment of cerebral edema.
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23
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Le Ribeuz H, Capuano V, Girerd B, Humbert M, Montani D, Antigny F. Implication of Potassium Channels in the Pathophysiology of Pulmonary Arterial Hypertension. Biomolecules 2020; 10:biom10091261. [PMID: 32882918 PMCID: PMC7564204 DOI: 10.3390/biom10091261] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/24/2020] [Accepted: 08/27/2020] [Indexed: 02/06/2023] Open
Abstract
Pulmonary arterial hypertension (PAH) is a rare and severe cardiopulmonary disease without curative treatments. PAH is a multifactorial disease that involves genetic predisposition, epigenetic factors, and environmental factors (drugs, toxins, viruses, hypoxia, and inflammation), which contribute to the initiation or development of irreversible remodeling of the pulmonary vessels. The recent identification of loss-of-function mutations in KCNK3 (KCNK3 or TASK-1) and ABCC8 (SUR1), or gain-of-function mutations in ABCC9 (SUR2), as well as polymorphisms in KCNA5 (Kv1.5), which encode two potassium (K+) channels and two K+ channel regulatory subunits, has revived the interest of ion channels in PAH. This review focuses on KCNK3, SUR1, SUR2, and Kv1.5 channels in pulmonary vasculature and discusses their pathophysiological contribution to and therapeutic potential in PAH.
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Affiliation(s)
- Hélène Le Ribeuz
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
| | - Véronique Capuano
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
| | - Barbara Girerd
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
| | - Marc Humbert
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
| | - David Montani
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
| | - Fabrice Antigny
- Faculté de Médecine, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, France; (H.L.R.); (V.C.); (B.G.); (M.H.); (D.M.)
- INSERM UMR_S 999, Hypertension pulmonaire, Physiopathologie et Innovation Thérapeutique, Hôpital Marie Lannelongue, 92350 Le Plessis-Robinson, France
- Assistance Publique—Hôpitaux de Paris (AP-HP), Service de Pneumologie et Soins Intensifs Respiratoires, Centre de Référence de l’Hypertension Pulmonaire, Hôpital Bicêtre, 94270 Le Kremlin-Bicêtre, France
- Correspondence: or ; Tel.: +33-1-40-94-22-99
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24
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Bakhtiyari A, Haghani K, Bakhtiyari S, Zaimy MA, Noori-Zadeh A, Gheysarzadeh A, Darabi S, Seidkhani-Nahal A, Amraei M, Alipourfard I. Association between ABCC8 Ala1369Ser Polymorphism (rs757110 T/G) and Type 2 Diabetes Risk in an Iranian Population: A Case-Control Study. Endocr Metab Immune Disord Drug Targets 2020; 21:441-447. [PMID: 32660410 DOI: 10.2174/1871530320666200713091827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Glucose metabolism increases ATP/ADP ratio within the β-cells and causes ATP-sensitive K+ (KATP) channel closure and consequently insulin secretion. The enhanced activity of the channel may be a mechanism contributing to the reduced first-phase of insulin secretion observed in T2DM. There is no study to date in the Kurdish ethnic group regarding the relationship between SNP Ala1369Ser (rs757110 T/G) of SUR1 gene and T2DM, and additionally, the results of this association in other populations are inconsistent. Therefore, our aim in this study was to explore the possible association between SNP Ala1369Ser and type 2 diabetes in an Iranian Kurdish ethnic group. METHODS In this study, we checked out the frequency of alleles and genotypes of SNP Ala1369Ser in T2DM individuals (207 patients; men/women: 106/101) and non-T2DM subjects (201 controls; men/women: 97/104), and their effects on anthropometric, clinical, and biochemical parameters. Genomic DNA was extracted from the leukocytes of blood specimens using a standard method. We amplified the ABCC8 rs757110 polymorphic site (T/G) using a polymerase chain reaction (PCR) method and a designed primer pair. To perform the PCR-RFLP method, the amplicons were subjected to restriction enzymes and the resulting fragments separated by gel electrophoresis. RESULTS The frequency of the G-allele of Ala1369Ser polymorphism was significantly (0.01) higher in the case group than the control group (19% vs. 9%, respectively). In the dominant model (TT vs. TG+GG), there was a significant relationship between this SNP and an increased risk of T2DM (P = 0.00). T2DM patients with TG+GG genotypes had significantly higher fasting plasma insulin and HOMA-IR than those who had the TT genotype (P = 0.02 and 0.01, respectively). CONCLUSION Our study is the first study to investigate the association between Ala1369Ser ABCC8 genetic variation and T2DM in the Kurdish population of western Iran. The obtained results clearly show that Ala1369Ser polymorphism of ABCC8 is associated with an increased risk of T2DM in this population.
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Affiliation(s)
- Amin Bakhtiyari
- Department of Genetics, Biology Research Center, Zanjan Branch, Islamic Azad University, Zanjan, Iran.,Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran
| | - Karimeh Haghani
- Department of Clinical Biochemistry, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran
| | - Salar Bakhtiyari
- Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran.,Department of Clinical Biochemistry, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran
| | - Mohammad A Zaimy
- Department of Medical Genetics, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran
| | - Ali Noori-Zadeh
- Department of Clinical Biochemistry, Faculty of Allied Medical Sciences, Ilam University of Medical Sciences, Ilam, Iran
| | - Ali Gheysarzadeh
- Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran.,Department of Biology, Faculty of Science, Ilam University, Ilam, Iran
| | - Shahram Darabi
- Cellular and Molecular Research Center, Qazvin University of Medical Sciences, Qazvin, Iran
| | - Ali Seidkhani-Nahal
- Department of Clinical Biochemistry, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran
| | - Mansour Amraei
- Department of Physiology, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran
| | - Iraj Alipourfard
- School of Pharmacy, Faculty of Sciences, University of Rome Tor Vergata, Rome, Italy
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25
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Jha RM, Bell J, Citerio G, Hemphill JC, Kimberly WT, Narayan RK, Sahuquillo J, Sheth KN, Simard JM. Role of Sulfonylurea Receptor 1 and Glibenclamide in Traumatic Brain Injury: A Review of the Evidence. Int J Mol Sci 2020; 21:E409. [PMID: 31936452 PMCID: PMC7013742 DOI: 10.3390/ijms21020409] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 12/28/2019] [Accepted: 01/03/2020] [Indexed: 02/07/2023] Open
Abstract
Cerebral edema and contusion expansion are major determinants of morbidity and mortality after TBI. Current treatment options are reactive, suboptimal and associated with significant side effects. First discovered in models of focal cerebral ischemia, there is increasing evidence that the sulfonylurea receptor 1 (SUR1)-Transient receptor potential melastatin 4 (TRPM4) channel plays a key role in these critical secondary injury processes after TBI. Targeted SUR1-TRPM4 channel inhibition with glibenclamide has been shown to reduce edema and progression of hemorrhage, particularly in preclinical models of contusional TBI. Results from small clinical trials evaluating glibenclamide in TBI have been encouraging. A Phase-2 study evaluating the safety and efficacy of intravenous glibenclamide (BIIB093) in brain contusion is actively enrolling subjects. In this comprehensive narrative review, we summarize the molecular basis of SUR1-TRPM4 related pathology and discuss TBI-specific expression patterns, biomarker potential, genetic variation, preclinical experiments, and clinical studies evaluating the utility of treatment with glibenclamide in this disease.
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Affiliation(s)
- Ruchira M. Jha
- Departments of Critical Care Medicine, Neurology, Neurological Surgery, Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, PA 15201, USA
| | | | - Giuseppe Citerio
- School of Medicine and Surgery, University of Milan-Bicocca, 20121 Milan, Italy;
- Anaesthesia and Intensive Care, San Gerardo and Desio Hospitals, ASST-Monza, 20900 Monza, Italy
| | - J. Claude Hemphill
- Department of Neurology, University of California, San Francisco, CA 94110, USA;
| | - W. Taylor Kimberly
- Division of Neurocritical Care and Center for Genomic Medicine, Department of Neurology, Massachusetts General Hospital, Boston, MA 02108, USA;
| | - Raj K. Narayan
- Department of Neurosurgery, North Shore University Hospital, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Manhasset, NY 11030, USA;
| | - Juan Sahuquillo
- Neurotrauma and Neurosurgery Research Unit (UNINN), Vall d′Hebron Research Institute (VHIR), 08001 Barcelona, Spain;
- Department of Neurosurgery, Universitat Autònoma de Barcelona (UAB), 08001 Barcelona, Spain
- Department of Neurosurgery, Vall d′Hebron University Hospital, 08001 Barcelona, Spain
| | - Kevin N. Sheth
- Division of Neurocritical Care and Emergency Neurology, Department of Neurology, Yale University School of Medicine, New Haven, CT 06501, USA;
| | - J. Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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26
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Abstract
Today, excluding insulin, there are eight classes of anti-diabetic medicines that have been added to the pharmacy since the introduction of metformin in the mid-1950s; the sulfonylureas, biguanides, thiazolidinediones, α-glucosidase inhibitors, meglitinides, incretins, and sodium glucose transport 2 inhibitors. Does the fact that metformin is still first-line treatment suggest that our drug discovery efforts over the past 60 years have not been good enough? Or does it suggest that diabetes is such a complex disorder that no single treatment, other than gastric bypass surgery, can affect true normalization of not only blood sugar but also the underlying pathologies? Our understanding of the disease has most definitely improved which may bring hope for the future in terms of science, but for it to be beneficial, this science has to be translated into better drug treatments for the disease. In this review, I have examined the eight classes of anti-diabetes drugs from a drug discovery perspective.
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Affiliation(s)
- John C Clapham
- Medical School, University of Buckingham, Buckingham, UK.
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27
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Savateev K, Fedotov V, Butorin I, Eltsov O, Slepukhin P, Ulomsky E, Rusinov V, Litvinov R, Babkov D, Khokhlacheva E, Radaev P, Vassiliev P, Spasov A. Nitrothiadiazolo[3,2-a]pyrimidines as promising antiglycating agents. Eur J Med Chem 2019; 185:111808. [PMID: 31683103 DOI: 10.1016/j.ejmech.2019.111808] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 10/19/2019] [Accepted: 10/21/2019] [Indexed: 12/30/2022]
Abstract
Managing the advanced glycation end-products (AGEs) concentration is a reliable approach to achieve control over the pathogenesis of diabetic vascular complications. Inhibition of dipeptidyl peptidase-4 (DPP-4) is also an attractive way to tackle type 2 diabetes mellitus (T2DM). We showed previously that azoloazine heterocycles have the potential to prevent the formation of AGEs and in this work, we conducted docking studies with DPP-4 of 5-alkylamino-6-nitro-1,3,4-thiadiazolo[3,2-a]pyrimidines. Consequently, we have developed a synthetic approach to these structures by chlorodeoxygenation and amination reactions. Antidiabetic properties of obtained compounds were studied by evaluating DPP-4 (ex vivo/in vitro) and AGEs formation inhibition (in vitro). It was shown that the nitrothiadiazolopyrimidines exhibit a higher antiglycation activity than reference compound aminoguanidine, but only moderate inhibition of DPP-4. The most active DPP-4 inhibitor 1l had IC50 of 55.87 μM and showed the ability to inhibit serum DPP-4 activity in rats after 10 mg/kg oral administration but with the less and shorter effect than vildagliptin. At the same time, 1l was the most active antiglycating compound in the series (IC50 134.4 μM). Copper chelation properties of synthesized compounds were also investigated since the formation of AGEs is catalyzed by the transition metal cations. A noticeable correlation between antiglycation activity and metal chelation was revealed. Both activities (antiglycation and copper chelation) correlated with quantum-chemical properties (calculated with ab initio) of the tested compounds. These findings will allow us to predict both activities in the future, without the need to model multiple steps of glycation reaction.
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Affiliation(s)
- Konstantin Savateev
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation.
| | - Victor Fedotov
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation
| | - Ilya Butorin
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation
| | - Oleg Eltsov
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation
| | - Pavel Slepukhin
- Institute of Organic Synthesis of the Ural Branch of the Russian Academy of Science, Sofii Kovalevskoy st. 22, Yekaterinburg, 620137, Russian Federation
| | - Evgeny Ulomsky
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation
| | - Vladimir Rusinov
- Department of Organic and Biomolecular Chemistry, Ural Federal University Named After the First President of Russia B.N. Eltsin, Mira st. 19, Yekaterinburg, 620002, Russian Federation
| | - Roman Litvinov
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
| | - Denis Babkov
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
| | - Elisaveta Khokhlacheva
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
| | - Pyotr Radaev
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
| | - Pavel Vassiliev
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
| | - Alexandr Spasov
- Volgograd State Medical University, Pavshikh Bortsov Sq., Volgograd, 400131, Russian Federation
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28
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Wu JX, Ding D, Wang M, Chen L. Structural Insights into the Inhibitory Mechanism of Insulin Secretagogues on the Pancreatic ATP-Sensitive Potassium Channel. Biochemistry 2019; 59:18-25. [PMID: 31566370 DOI: 10.1021/acs.biochem.9b00692] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Sulfonylureas and glinides are commonly used oral insulin secretagogues (ISs) that act on the pancreatic ATP-sensitive potassium (KATP) channel to promote insulin secretion in order to lower the blood glucose level. Physiologically, KATP channels are inhibited by intracellular ATP and activated by Mg-ADP. Therefore, they sense the cellular energy status to regulate the permeability of potassium ions across the plasma membrane. The pancreatic KATP channel is composed of the pore-forming Kir6.2 subunits and the regulatory SUR1 subunits. Previous electrophysiological studies have established that ISs bind to the SUR1 subunit and inhibit the channel activity primarily by two mechanisms. First, ISs prevent Mg-ADP activation. Second, ISs inhibit the channel activity of Kir6.2 directly. Several cryo-EM structures of the pancreatic KATP channel determined recently have provided remarkable structural insights into these two mechanisms.
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Affiliation(s)
- Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China
| | - Dian Ding
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China.,Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Mengmeng Wang
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China.,Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Lei Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences , Peking University , Beijing 100871 , China
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29
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Martin GM, Sung MW, Yang Z, Innes LM, Kandasamy B, David LL, Yoshioka C, Shyng SL. Mechanism of pharmacochaperoning in a mammalian K ATP channel revealed by cryo-EM. eLife 2019; 8:46417. [PMID: 31343405 PMCID: PMC6699824 DOI: 10.7554/elife.46417] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/22/2019] [Indexed: 01/03/2023] Open
Abstract
ATP-sensitive potassium (KATP) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic β-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse KATP inhibitors are known to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of a mammalian KATP channel bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. We found all three drugs bind within a common pocket in SUR1. Further, we found the N-terminus of Kir6.2 inserted within the central cavity of the SUR1 ABC core, adjacent the drug binding pocket. The findings reveal a common mechanism by which diverse compounds stabilize the Kir6.2 N-terminus within SUR1’s ABC core, allowing it to act as a firm ‘handle’ for the assembly of metastable mutant SUR1-Kir6.2 complexes.
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Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Min Woo Sung
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Zhongying Yang
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Laura M Innes
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Balamurugan Kandasamy
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Larry L David
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, United States
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
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30
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Shams T, Brako F, Huo S, Harker AH, Edirisinghe U, Edirisinghe M. The influence of drug solubility and sampling frequency on metformin and glibenclamide release from double-layered particles: experimental analysis and mathematical modelling. J R Soc Interface 2019; 16:20190237. [PMID: 31238838 DOI: 10.1098/rsif.2019.0237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Co-axial electrohydrodynamic atomization was used to prepare core/shell polymethylsilsesquioxane particles for co-delivery of metformin and glibenclamide in a sustained release manner. The drug-loaded microparticles were mostly spherical and uniformly distributed in size, with average diameters between 3 and 5 µm across various batches. FTIR was used to confirm the presence of drugs within the particles while X-ray diffraction studies revealed drugs encapsulated existed predominantly in the amorphous state. Intended as systems that potentially can act as depot formulations for long-term release of antidiabetics, a detailed analysis of drug release from these particles was necessary. Drugs of different solubilities were selected in order to study the effects of drug solubility from a core/shell particle system. Further analyses to determine how conditions such as release into a limited volume of media, sampling rate and partitioning of drug between the core and shell layers influenced drug release were conducted by comparing experimental and mathematically modelled outcomes. It was found that while the solubility of drug may affect release from such systems, rate of removal of drug (sampling frequency) which upsets local equilibrium at the particle/solution interface prompting a rapid release to redress the equilibrium influenced release more.
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Affiliation(s)
- T Shams
- 1 Department of Mechanical Engineering, University College London , Torrington Place, London WC1E 7JE , UK.,2 Department of Pharmaceutics, University College London School of Pharmacy , Brunswick Square, London WC1N 1AX , UK
| | - F Brako
- 1 Department of Mechanical Engineering, University College London , Torrington Place, London WC1E 7JE , UK.,2 Department of Pharmaceutics, University College London School of Pharmacy , Brunswick Square, London WC1N 1AX , UK
| | - S Huo
- 3 London Centre for Nanotechnology , Kings Cross, London WC1H 0AH , UK
| | - A H Harker
- 4 Department of Physics and Astronomy, London Centre for Nanotechnology, University College London , London WC1E 6BT , UK
| | - U Edirisinghe
- 5 Accident and Emergency Department, Chelsea and Westminster Hospital , London SW10 9NH , UK
| | - M Edirisinghe
- 1 Department of Mechanical Engineering, University College London , Torrington Place, London WC1E 7JE , UK
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31
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Subbotina E, Yang HQ, Gando I, Williams N, Sampson BA, Tang Y, Coetzee WA. Functional characterization of ABCC9 variants identified in sudden unexpected natural death. Forensic Sci Int 2019; 298:80-87. [PMID: 30878466 DOI: 10.1016/j.forsciint.2019.02.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 02/19/2019] [Accepted: 02/20/2019] [Indexed: 12/28/2022]
Abstract
BACKGROUND Genetic variation in ion channel genes ('channelopathies') are often associated with inherited arrhythmias and sudden death. Genetic testing ('molecular autopsies') of channelopathy genes can be used to assist in determining the likely causes of sudden unexpected death. However, different in silico approaches can yield conflicting pathogenicity predictions and assessing their impact on ion channel function can assist in this regard. METHODS AND RESULTS We performed genetic testing of cases of sudden expected death in the New York City metropolitan area and found four rare or novel variants in ABCC9, which codes for the regulatory SUR2 subunit of KATP channels. All were missense variants, causing amino acid changes in the protein. Three of the variants (A355S, M941V, and K1379Q) were in cases of infants less than six-months old and one (H1305Y) was in an adult. The predicted pathogenicities of the variants were conflicting. We have introduced these variants into a human SUR2A cDNA, which we coexpressed with the Kir6.2 pore-forming subunit in HEK-293 cells and subjected to patch clamp and biochemical assays. Each of the four variants led to gain-of-function phenotypes. The A355S and M941V variants increased in the overall patch current. The sensitivity of the KATP channels to inhibitory 'cytosolic' ATP was repressed for the M941V, H1305Y and K1379Q variants. None of the variants had any effect on the unitary KATP channel current or the surface expression of KATP channels, as determined with biotinylation assays, suggesting that all of the variants led to an enhanced open state. CONCLUSIONS All four variants caused a gain-of-function phenotype. Given the expression of SUR2-containing KATP channels in the heart and specialized cardiac conduction, vascular smooth muscle and respiratory neurons, it is conceivable that electrical silencing of these cells may contribute to the vulnerability element, which is a component of the triple risk model of sudden explained death in infants. The gain-of-function phenotype of these ABCC9 variants should be considered when assessing their potential pathogenicity.
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Affiliation(s)
| | - Hua-Qian Yang
- Departments of Pediatrics, NYU School of Medicine, New York, NY 10016 USA
| | - Ivan Gando
- Departments of Pediatrics, NYU School of Medicine, New York, NY 10016 USA
| | - Nori Williams
- Molecular Genetics Laboratory, Office of Chief Medical Examiner, New York, NY USA
| | - Barbara A Sampson
- Molecular Genetics Laboratory, Office of Chief Medical Examiner, New York, NY USA
| | - Yingying Tang
- Molecular Genetics Laboratory, Office of Chief Medical Examiner, New York, NY USA
| | - William A Coetzee
- Departments of Pediatrics, NYU School of Medicine, New York, NY 10016 USA; Departments of Physiology & Neuroscience NYU School of Medicine, New York, NY 10016 USA; Departments of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016 USA.
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32
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Zhou X, Xu C, Zou Z, Shen X, Xie T, Zhang R, Liao L, Dong J. aThe characteristics of glucose metabolism in the sulfonylurea receptor 1 knockout rat model. Mol Med 2019; 25:2. [PMID: 30616503 PMCID: PMC6322298 DOI: 10.1186/s10020-018-0067-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022] Open
Abstract
Background Sulfonylurea receptor 1 (SUR1) is primarily responsible for glucose regulation in normal conditions. Here, we sought to investigate the glucose metabolism characteristics of SUR1−/− rats. Methods The TALEN technique was used to construct a SUR1 gene deficiency rat model. Rats were grouped by SUR1 gene knockout or not and sex difference. Body weight; glucose metabolism indicators, including IPGTT, IPITT, glycogen contents and so on; and other molecule changes were examined. Results Insulin secretion was significantly inhibited by knocking out the SUR1 gene. SUR1−/− rats showed lower body weights compared to wild-type rats, and even SUR1−/− males weighed less than wild-type females. Upon SUR1 gene knockout, the rats showed a peculiar plasma glucose profile. During IPGTT, plasma glucose levels were significantly elevated in SUR1−/− rats at 15 min, which could be explained by SUR1 mainly working in the first phase of insulin secretion. Moreover, SUR1−/− male rats showed obviously impaired glucose tolerance than before and a better insulin sensitivity in the 12th week compared with females, which might be related with excess androgen secretion in adulthood. Increased glycogen content and GLUT4 expression and the inactivation of GSK3 were also observed in SUR1−/− rats, which suggested an enhancement of insulin sensitivity. Conclusions These results reconfirm the role of SUR1 in systemic glucose metabolism. More importantly, our SUR1−/− rat model might be applied in other fields, such as for exploring other hypoglycaemic functions of sulfonylureas. Electronic supplementary material The online version of this article (10.1186/s10020-018-0067-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xiaojun Zhou
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, Shandong, 250014, People's Republic of China
| | - Chunmei Xu
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, Shandong, 250014, People's Republic of China
| | - Zhiwei Zou
- Department of Endocrinology, Qilu Hospital of Shandong University, Shandong University, Jinan, Shandong, 250012, People's Republic of China
| | - Xue Shen
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China
| | - Tianyue Xie
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University of Traditional Chinese Medicine, Jinan, Shandong, China
| | - Rui Zhang
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, Shandong, 250014, People's Republic of China
| | - Lin Liao
- Department of Endocrinology, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, Shandong, 250014, People's Republic of China.
| | - Jianjun Dong
- Department of Endocrinology, Qilu Hospital of Shandong University, Shandong University, Jinan, Shandong, 250012, People's Republic of China.
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33
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Abstract
The transport of specific molecules across lipid membranes is an essential function of all living organisms. The processes are usually mediated by specific transporters. One of the largest transporter families is the ATP-binding cassette (ABC) family. More than 40 ABC transporters have been identified in human, which are divided into 7 subfamilies (ABCA to ABCG) based on their gene structure, amino acid sequence, domain organization, and phylogenetic analysis. Of them, at least 11 ABC transporters including P-glycoprotein (P-GP/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2) are involved in multidrug resistance (MDR) development. These ABC transporters are expressed in various tissues such as the liver, intestine, kidney, and brain, playing important roles in absorption, distribution, and excretion of drugs. Some ABC transporters are also involved in diverse cellular processes such as maintenance of osmotic homeostasis, antigen processing, cell division, immunity, cholesterol, and lipid trafficking. Several human diseases such as cystic fibrosis, sitosterolemia, Tangier disease, intrahepatic cholestasis, and retinal degeneration are associated with mutations in corresponding transporters. This chapter will describe function and expression of several ABC transporters (such as P-GP, BCRP, and MRPs), their substrates and inhibitors, as well as their clinical significance.
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Affiliation(s)
- Xiaodong Liu
- China Pharmaceutical University, Nanjing, China.
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34
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Sooklal CR, López-Alonso JP, Papp N, Kanelis V. Phosphorylation Alters the Residual Structure and Interactions of the Regulatory L1 Linker Connecting NBD1 to the Membrane-Bound Domain in SUR2B. Biochemistry 2018; 57:6278-6292. [PMID: 30273482 DOI: 10.1021/acs.biochem.8b00503] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
ATP-sensitive potassium (KATP) channels in vascular smooth muscle are comprised of four pore-forming Kir6.1 subunits and four copies of the sulfonylurea receptor 2B (SUR2B), which acts as a regulator of channel gating. Recent electron cryo-microscopy (cryo-EM) structures of the pancreatic KATP channel show a central Kir6.2 pore that is surrounded by the SUR1 subunits. Mutations in the L1 linker connecting the first membrane-spanning domain and the first nucleotide binding domain (NBD1) in SUR2B cause cardiac disease; however, this part of the protein is not resolved in the cryo-EM structures. Phosphorylation of the L1 linker, by protein kinase A, disrupts its interactions with NBD1, which increases the MgATP affinity of NBD1 and KATP channel gating. To elucidate the mode by which the L1 linker regulates KATP channels, we have probed the effects of phosphorylation on its structure and interactions using nuclear magnetic resonance (NMR) spectroscopy and other techniques. We demonstrate that the L1 linker is an intrinsically disordered region of SUR2B but possesses residual secondary and compact structure, both of which are disrupted with phosphorylation. NMR binding studies demonstrate that phosphorylation alters the mode by which the L1 linker interacts with NBD1. The data show that L1 linker residues with the greatest α-helical propensity also form the most stable interaction with NBD1, highlighting a hot spot within the L1 linker. This hot spot is the site of disease-causing mutations and is associated with other processes that regulate KATP channel gating. These data provide insights into the mode by which the phospho-regulatory L1 linker regulates KATP channels.
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Affiliation(s)
- Clarissa R Sooklal
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Jorge P López-Alonso
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Natalia Papp
- Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6
| | - Voula Kanelis
- Department of Chemistry , University of Toronto , Toronto , ON , Canada M5S 3H8.,Department of Chemical and Physical Sciences , University of Toronto Mississauga , Mississauga , ON , Canada L5L 1C6.,Department of Cell and Systems Biology , University of Toronto , Toronto , ON , Canada M5S 3G5
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Osa-Andrews B, Tan KW, Sampson A, Iram SH. Development of Novel Intramolecular FRET-Based ABC Transporter Biosensors to Identify New Substrates and Modulators. Pharmaceutics 2018; 10:pharmaceutics10040186. [PMID: 30322148 PMCID: PMC6321552 DOI: 10.3390/pharmaceutics10040186] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 10/10/2018] [Accepted: 10/12/2018] [Indexed: 12/14/2022] Open
Abstract
Multidrug resistance protein 1 (MRP1) can efflux a wide variety of molecules including toxic chemicals, drugs, and their derivatives out of cells. Substrates of MRP1 include anti-cancer agents, antibiotics, anti-virals, anti-human immunodeficiency virus (HIV), and many other drugs. To identify novel substrates and modulators of MRP1 by exploiting intramolecular fluorescence resonance energy transfer (FRET), we genetically engineered six different two-color MRP1 proteins by changing green fluorescent protein (GFP) insertion sites, while keeping the red fluorescent protein (RFP) at the C-terminal of MRP1. Four of six recombinant proteins showed normal expression, localization, and transport activity. We quantified intramolecular FRET using ensemble fluorescence spectroscopy in response to binding of known substrate or ATP alone, substrate/ATP, and trapping of the transporter in closed conformation by vanadate. Recombinant MRP1 proteins GR-881, GR-888, and GR-905 exhibited reproducible and higher FRET changes under all tested conditions and are very promising for use as MRP1 biosensors. Furthermore, we used GR-881 to screen 40 novel anti-cancer drugs and identified 10 hits that potentially directly interact with MRP1 and could be substrates or modulators. Profiling of drug libraries for interaction with MRP1 can provide very useful information to improve the efficacy and reduce the toxicity of various therapies.
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Affiliation(s)
- Bremansu Osa-Andrews
- Department of Chemistry & Biochemistry, College of Arts and Sciences, South Dakota State University, Brookings, SD 57007, USA.
| | - Kee W Tan
- Department of Chemistry & Biochemistry, College of Arts and Sciences, South Dakota State University, Brookings, SD 57007, USA.
| | - Angelina Sampson
- Department of Chemistry & Biochemistry, College of Arts and Sciences, South Dakota State University, Brookings, SD 57007, USA.
| | - Surtaj H Iram
- Department of Chemistry & Biochemistry, College of Arts and Sciences, South Dakota State University, Brookings, SD 57007, USA.
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36
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Gerzanich V, Stokum JA, Ivanova S, Woo SK, Tsymbalyuk O, Sharma A, Akkentli F, Imran Z, Aarabi B, Sahuquillo J, Simard JM. Sulfonylurea Receptor 1, Transient Receptor Potential Cation Channel Subfamily M Member 4, and KIR6.2:Role in Hemorrhagic Progression of Contusion. J Neurotrauma 2018; 36:1060-1079. [PMID: 30160201 PMCID: PMC6446209 DOI: 10.1089/neu.2018.5986] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In severe traumatic brain injury (TBI), contusions often are worsened by contusion expansion or hemorrhagic progression of contusion (HPC), which may double the original contusion volume and worsen outcome. In humans and rodents with contusion-TBI, sulfonylurea receptor 1 (SUR1) is upregulated in microvessels and astrocytes, and in rodent models, blockade of SUR1 with glibenclamide reduces HPC. SUR1 does not function by itself, but must co-assemble with either KIR6.2 or transient receptor potential cation channel subfamily M member 4 (TRPM4) to form KATP (SUR1-KIR6.2) or SUR1-TRPM4 channels, with the two having opposite effects on membrane potential. Both KIR6.2 and TRPM4 are reportedly upregulated in TBI, especially in astrocytes, but the identity and function of SUR1-regulated channels post-TBI is unknown. Here, we analyzed human and rat brain tissues after contusion-TBI to characterize SUR1, TRPM4, and KIR6.2 expression, and in the rat model, to examine the effects on HPC of inhibiting expression of the three subunits using intravenous antisense oligodeoxynucleotides (AS-ODN). Glial fibrillary acidic protein (GFAP) immunoreactivity was used to operationally define core versus penumbral tissues. In humans and rats, GFAP-negative core tissues contained microvessels that expressed SUR1 and TRPM4, whereas GFAP-positive penumbral tissues contained astrocytes that expressed all three subunits. Förster resonance energy transfer imaging demonstrated SUR1-TRPM4 heteromers in endothelium, and SUR1-TRPM4 and SUR1-KIR6.2 heteromers in astrocytes. In rats, glibenclamide as well as AS-ODN targeting SUR1 and TRPM4, but not KIR6.2, reduced HPC at 24 h post-TBI. Our findings demonstrate upregulation of SUR1-TRPM4 and KATP after contusion-TBI, identify SUR1-TRPM4 as the primary molecular mechanism that accounts for HPC, and indicate that SUR1-TRPM4 is a crucial target of glibenclamide.
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Affiliation(s)
- Volodymyr Gerzanich
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Jesse A Stokum
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Svetlana Ivanova
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Seung Kyoon Woo
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Orest Tsymbalyuk
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Amit Sharma
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Fatih Akkentli
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Ziyan Imran
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Bizhan Aarabi
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland
| | - Juan Sahuquillo
- 2 Neurotraumatology and Neurosurgery Research Unit, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain.,3 Department of Neurosurgery, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - J Marc Simard
- 1 Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland.,4 Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland.,5 Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
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Carrington SJ, Hernandez CC, Swale DR, Aluko OA, Denton JS, Cone RD. G protein-coupled receptors differentially regulate glycosylation and activity of the inwardly rectifying potassium channel Kir7.1. J Biol Chem 2018; 293:17739-17753. [PMID: 30257863 DOI: 10.1074/jbc.ra118.003238] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 09/18/2018] [Indexed: 12/15/2022] Open
Abstract
Kir7.1 is an inwardly rectifying potassium channel with important roles in the regulation of the membrane potential in retinal pigment epithelium, uterine smooth muscle, and hypothalamic neurons. Regulation of G protein-coupled inwardly rectifying potassium (GIRK) channels by G protein-coupled receptors (GPCRs) via the G protein βγ subunits has been well characterized. However, how Kir channels are regulated is incompletely understood. We report here that Kir7.1 is also regulated by GPCRs, but through a different mechanism. Using Western blotting analysis, we observed that multiple GPCRs tested caused a striking reduction in the complex glycosylation of Kir7.1. Further, GPCR-mediated reduction of Kir7.1 glycosylation in HEK293T cells did not alter its expression at the cell surface but decreased channel activity. Of note, mutagenesis of the sole Kir7.1 glycosylation site reduced conductance and open probability, as indicated by single-channel recording. Additionally, we report that the L241P mutation of Kir7.1 associated with Lebers congenital amaurosis (LCA), an inherited retinal degenerative disease, has significantly reduced complex glycosylation. Collectively, these results suggest that Kir7.1 channel glycosylation is essential for function, and this activity within cells is suppressed by most GPCRs. The melanocortin-4 receptor (MC4R), a GPCR previously reported to induce ligand-regulated activity of this channel, is the only GPCR tested that does not have this effect on Kir7.1.
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Affiliation(s)
- Sheridan J Carrington
- From the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Daniel R Swale
- Department of Entomology, Louisiana State University AgCenter, Baton Rouge, Louisiana 70803
| | - Oluwatosin A Aluko
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | - Jerod S Denton
- Departments of Anesthesiology; Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Roger D Cone
- From the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232; Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109; Department of Molecular and Integrative Physiology, University of Michigan School of Medicine, Ann Arbor, Michigan 48109.
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King ZA, Sheth KN, Kimberly WT, Simard JM. Profile of intravenous glyburide for the prevention of cerebral edema following large hemispheric infarction: evidence to date. DRUG DESIGN DEVELOPMENT AND THERAPY 2018; 12:2539-2552. [PMID: 30147301 PMCID: PMC6101021 DOI: 10.2147/dddt.s150043] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Glyburide (also known as glibenclamide) is a second-generation sulfonylurea drug that inhibits sulfonylurea receptor 1 (Sur1) at nanomolar concentrations. Long used to target KATP (Sur1–Kir6.2) channels for the treatment of diabetes mellitus type 2, glyburide was recently repurposed to target Sur1–transient receptor potential melastatin 4 (Trpm4) channels in acute central nervous system injury. Discovered nearly two decades ago, SUR1–TRPM4 has emerged as a critical target in stroke, specifically in large hemispheric infarction, which is characterized by edema formation and life-threatening brain swelling. Following ischemia, SUR1–TRPM4 channels are transcriptionally upregulated in all cells of the neurovascular unit, including neurons, astrocytes, microglia, oligodendrocytes and microvascular endothelial cells. Work by several independent laboratories has linked SUR1–TRPM4 to edema formation, with blockade by glyburide reducing brain swelling and death in preclinical models. Recent work showed that, following ischemia, SUR1–TRPM4 co-assembles with aquaporin-4 to mediate cellular swelling of astrocytes, which contributes to brain swelling. Additionally, recent work linked SUR1–TRPM4 to secretion of matrix metalloproteinase-9 (MMP-9) induced by recombinant tissue plasminogen activator in activated brain endothelial cells, with blockade of SUR1–TRPM4 by glyburide reducing MMP-9 and hemorrhagic transformation in preclinical models with recombinant tissue plasminogen activator. The recently completed GAMES (Glyburide Advantage in Malignant Edema and Stroke) clinical trials on patients with large hemispheric infarctions treated with intravenous glyburide (RP-1127) revealed promising findings with regard to brain swelling (midline shift), MMP-9, functional outcomes and mortality. Here, we review key elements of the basic science, preclinical experiments and clinical studies, both retrospective and prospective, on glyburide in focal cerebral ischemia and stroke.
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Affiliation(s)
- Zachary A King
- Department of Neurology, Division of Neurocritical Care and Emergency Neurology, Yale University School of Medicine, New Haven, CT, USA
| | - Kevin N Sheth
- Department of Neurology, Division of Neurocritical Care and Emergency Neurology, Yale University School of Medicine, New Haven, CT, USA
| | - W Taylor Kimberly
- Department of Neurology, Division of Neurocritical Care and Emergency Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, USA,
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Ligand binding and conformational changes of SUR1 subunit in pancreatic ATP-sensitive potassium channels. Protein Cell 2018; 9:553-567. [PMID: 29594720 PMCID: PMC5966361 DOI: 10.1007/s13238-018-0530-y] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 03/14/2018] [Indexed: 01/19/2023] Open
Abstract
ATP-sensitive potassium channels (KATP) are energy sensors on the plasma membrane. By sensing the intracellular ADP/ATP ratio of β-cells, pancreatic KATP channels control insulin release and regulate metabolism at the whole body level. They are implicated in many metabolic disorders and diseases and are therefore important drug targets. Here, we present three structures of pancreatic KATP channels solved by cryo-electron microscopy (cryo-EM), at resolutions ranging from 4.1 to 4.5 Å. These structures depict the binding site of the antidiabetic drug glibenclamide, indicate how Kir6.2 (inward-rectifying potassium channel 6.2) N-terminus participates in the coupling between the peripheral SUR1 (sulfonylurea receptor 1) subunit and the central Kir6.2 channel, reveal the binding mode of activating nucleotides, and suggest the mechanism of how Mg-ADP binding on nucleotide binding domains (NBDs) drives a conformational change of the SUR1 subunit.
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40
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Göddeke H, Timachi MH, Hutter CAJ, Galazzo L, Seeger MA, Karttunen M, Bordignon E, Schäfer LV. Atomistic Mechanism of Large-Scale Conformational Transition in a Heterodimeric ABC Exporter. J Am Chem Soc 2018; 140:4543-4551. [DOI: 10.1021/jacs.7b12944] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Hendrik Göddeke
- Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - M. Hadi Timachi
- EPR Spectroscopy, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Cedric A. J. Hutter
- Institute of Medical Microbiology, University of Zürich, 8006 Zürich, Switzerland
| | - Laura Galazzo
- EPR Spectroscopy, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Markus A. Seeger
- Institute of Medical Microbiology, University of Zürich, 8006 Zürich, Switzerland
| | - Mikko Karttunen
- Department of Chemistry and Department of Applied Mathematics, Western University, London, Ontario N6A 3K7, Canada
| | - Enrica Bordignon
- EPR Spectroscopy, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Lars V. Schäfer
- Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
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41
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Lee KPK, Chen J, MacKinnon R. Molecular structure of human KATP in complex with ATP and ADP. eLife 2017; 6:32481. [PMID: 29286281 PMCID: PMC5790381 DOI: 10.7554/elife.32481] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/29/2017] [Indexed: 12/20/2022] Open
Abstract
In many excitable cells, KATP channels respond to intracellular adenosine nucleotides: ATP inhibits while ADP activates. We present two structures of the human pancreatic KATP channel, containing the ABC transporter SUR1 and the inward-rectifier K+ channel Kir6.2, in the presence of Mg2+ and nucleotides. These structures, referred to as quatrefoil and propeller forms, were determined by single-particle cryo-EM at 3.9 Å and 5.6 Å, respectively. In both forms, ATP occupies the inhibitory site in Kir6.2. The nucleotide-binding domains of SUR1 are dimerized with Mg2+-ATP in the degenerate site and Mg2+-ADP in the consensus site. A lasso extension forms an interface between SUR1 and Kir6.2 adjacent to the ATP site in the propeller form and is disrupted in the quatrefoil form. These structures support the role of SUR1 as an ADP sensor and highlight the lasso extension as a key regulatory element in ADP’s ability to override ATP inhibition. A hormone called insulin finely controls the amount of sugar in the blood. When the blood sugar content is high, a group of cells in the pancreas release insulin; when it is low, they stop. In these cells, the level of sugar in the blood modifies the ratio of two molecules: ATP, the body’s energy currency, and ADP, a molecule closely related to ATP. Changes in the ATP/ADP ratio are therefore a proxy of the variations in blood sugar levels. In these pancreatic cells, a membrane protein called ATP sensitive potassium channel, KATP channel for short, acts as a switch that turns on and off the production of insulin. ATP and ADP control that switch, with the two molecules having opposite effects on the channel – ATP deactivates it, ADP activates it. The changes in ATP/ADP ratio – and by extension in blood sugar levels – are therefore coupled with the release of insulin. However, how KATP channels sense the changes in the ATP/ADP ratio in these cells is still unclear. In particular, ATP levels are usually high and constant: ATP is then continuously deactivating the channels, and it is unclear how ADP ever activates them. Here, Lee et al. use a microscopy technique that can image biological molecules at the atomic scale to look at the structure of human pancreatic KATP channels. The 3D reconstruction maps show that KATP channels have binding sites for ATP but also one for ADP. This ADP site acts as a sensor that can detect even small changes in ADP levels in the cell. The maps also reveal a dynamic lasso-like structure connecting the ATP and ADP binding areas. This domain may play a vital role in allowing ADP to override ATP’s control of the channel. The presence of the ADP sensor and the lasso structure could explain how KATP channels monitor changes in the ATP/ADP ratio and can therefore control the release of insulin based on blood sugar levels. Defects in the KATP channels of the pancreas are present in genetic diseases where infants produce too much or too little insulin. Understanding the structure of these channels and how they work may help scientists to design new drugs to treat these conditions.
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Affiliation(s)
- Kenneth Pak Kin Lee
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Jue Chen
- Laboratory of Membrane Biology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
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42
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Pan X, Zhang Q, Qu S, Huang S, Wang H, Mei H. Allosteric effects of ATP binding on the nucleotide-binding domain of a heterodimeric ATP-binding cassette transporter. Integr Biol (Camb) 2017; 8:1158-1169. [PMID: 27731447 DOI: 10.1039/c6ib00136j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ATP-binding cassette (ABC) exporters mediate vital transport of a variety of molecules across the lipid bilayer in all organisms. To explore the allosteric effect of ATP binding at the asymmetric ATPase sites, molecular dynamics simulations were performed on the nucleotide-binding domains (NBDs) of a heterodimeric exporter TM287/288 in 4 different ATP-bound states. The results showed that ATP bound at the degenerate site can maintain a semi-open conformation of NBD1-NBD2, which may be defective in ATP hydrolysis. By contrast, when bound at the consensus site, ATP can induce an intra-domain rotation of the α-helical subdomain towards the RecA-like subdomain of NBD2 at the degenerate site. The rotation of the α-helical subdomain rearranged the hydrogen bond networks at the NBD1-NBD2 interface, induced a significant conformational change in the D-loop at the degenerate site and inter- and intra-domain communications at both sites, and eventually elicited dimerization of NBD1-NBD2. These findings indicate that the asymmetric ATPase sites of the heterodimeric exporter are structurally and functionally distinct.
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Affiliation(s)
- Xianchao Pan
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, Chongqing University, Chongqing 400044, China. and College of Bioengineering, Chongqing University, Chongqing 400044, China
| | - Qiaoxia Zhang
- Chongqing Research Institute of Chemical Industry, Chongqing 400021, China
| | - Sujun Qu
- College of Bioengineering, Chongqing University, Chongqing 400044, China
| | - Shuheng Huang
- College of Bioengineering, Chongqing University, Chongqing 400044, China
| | - Huicong Wang
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, Chongqing University, Chongqing 400044, China. and College of Bioengineering, Chongqing University, Chongqing 400044, China
| | - Hu Mei
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, Chongqing University, Chongqing 400044, China. and College of Bioengineering, Chongqing University, Chongqing 400044, China
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Walsh KB, Gay EA, Blough BE, Geurkink DW. N-(2-methoxyphenyl) benzenesulfonamide, a novel regulator of neuronal G protein-gated inward rectifier K + channels. Eur J Pharmacol 2017; 815:233-240. [PMID: 28935562 DOI: 10.1016/j.ejphar.2017.09.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 09/14/2017] [Accepted: 09/15/2017] [Indexed: 02/07/2023]
Abstract
G protein-gated inward rectifier K+ (GIRK) channels are members of the super-family of proteins known as inward rectifier K+ (Kir) channels and are expressed throughout the peripheral and central nervous systems. Neuronal GIRK channels are the downstream targets of a number of neuromodulators including opioids, somatostatin, dopamine and cannabinoids. Previous studies have demonstrated that the ATP-sensitive K+ channel, another member of the Kir channel family, is regulated by sulfonamide drugs. Therefore, to determine if sulfonamides also modulate GIRK channels, we screened a library of arylsulfonamide compounds using a GIRK channel fluorescent assay that utilized pituitary AtT20 cells expressing GIRK channels along with the somatostatin type-2 and -5 receptors. Enhancement of the GIRK channel fluorescent signal by one compound, N-(2-methoxyphenyl) benzenesulfonamide (MPBS), was dependent on the activation of the channel by somatostatin. In whole-cell patch clamp experiments, application of MPBS both shifted the somatostatin concentration-response curve (EC50 = 3.5nM [control] vs.1.0nM [MPBS]) for GIRK channel activation and increased the maximum GIRK current measured with 100nM somatostatin. However, GIRK channel activation was not observed when MPBS was applied to the cells in the absence of somatostatin. While the MPBS structural analog 4-fluoro-N-(2-methoxyphenyl) benzenesulfonamide also augmented the somatostatin-induced GIRK fluorescent signal, no increase in the signal was observed with the sulfonamides tolbutamide, sulfapyridine and celecoxib. In conclusion, MPBS represents a novel prototypic GPCR-dependent regulator of neuronal GIRK channels.
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Affiliation(s)
- Kenneth B Walsh
- Department of Pharmacology, Physiology & Neuroscience, University of South Carolina, School of Medicine, Columbia, SC, United States.
| | - Elaine A Gay
- Center for Drug Discovery, Research Triangle Institute, Research Triangle Park, NC, United States
| | - Bruce E Blough
- Center for Drug Discovery, Research Triangle Institute, Research Triangle Park, NC, United States
| | - David W Geurkink
- Department of Pharmacology, Physiology & Neuroscience, University of South Carolina, School of Medicine, Columbia, SC, United States
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44
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Jha RM, Puccio AM, Okonkwo DO, Zusman BE, Park SY, Wallisch J, Empey PE, Shutter LA, Clark RSB, Kochanek PM, Conley YP. ABCC8 Single Nucleotide Polymorphisms are Associated with Cerebral Edema in Severe TBI. Neurocrit Care 2017; 26:213-224. [PMID: 27677908 DOI: 10.1007/s12028-016-0309-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Cerebral edema (CE) in traumatic brain injury (TBI) is the consequence of multiple underlying mechanisms and is associated with unfavorable outcomes. Genetic variability in these pathways likely explains some of the clinical heterogeneity observed in edema development. A role for sulfonylurea receptor-1 (Sur1) in CE is supported. However, there are no prior studies examining the effect of genetic variability in the Sur1 gene (ABCC8) on the development of CE. We hypothesize that ABCC8 single nucleotide polymorphisms (SNPs) are predictive of CE. METHODS DNA was extracted from 385 patients. SNPs in ABCC8 were genotyped using the Human Core Exome v1.2 (Illumina). CE measurements included acute CT edema, mean and peak intracranial pressure (ICP), and need for decompressive craniotomy. RESULTS Fourteen SNPs with minor allele frequency >0.2 were identified. Four SNPS rs2283261, rs3819521, rs2283258, and rs1799857 were associated with CE measures. In multiple regression models, homozygote-variant genotypes in rs2283261, rs3819521, and rs2283258 had increased odds of CT edema (OR 2.45, p = 0.007; OR 2.95, p = 0.025; OR 3.00, p = 0.013), had higher mean (β = 3.13, p = 0.000; β = 2.95, p = 0.005; β = 3.20, p = 0.008), and peak ICP (β = 8.00, p = 0.001; β = 7.64, p = 0.007; β = 6.89, p = 0.034). The homozygote wild-type genotype of rs1799857 had decreased odds of decompressive craniotomy (OR 0.47, p = 0.004). CONCLUSIONS This is the first report assessing the impact of ABCC8 genetic variability on CE development in TBI. Minor allele ABCC8 SNP genotypes had increased risk of CE, while major SNP alleles were protective-potentially suggesting an evolutionary advantage. These findings could guide risk stratification, treatment responders, and the development of novel targeted or gene-based therapies against CE in TBI and other neurological disorders.
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Affiliation(s)
- Ruchira M Jha
- Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA, 15261, USA. .,Department of Neurosurgery, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA. .,Department of Neurology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA. .,Safar Center for Resuscitation Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA. .,Clinical and Translational Science Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Ava M Puccio
- Department of Neurosurgery, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - David O Okonkwo
- Department of Neurosurgery, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Benjamin E Zusman
- Department of Neurosurgery, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Seo-Young Park
- Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Biostatistics, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jessica Wallisch
- Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA, 15261, USA.,Safar Center for Resuscitation Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Philip E Empey
- Department of Pharmacy and Therapeutics, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, USA.,Clinical and Translational Science Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Lori A Shutter
- Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA, 15261, USA.,Department of Neurosurgery, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Neurology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Robert S B Clark
- Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA, 15261, USA.,Safar Center for Resuscitation Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Anesthesiology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Patrick M Kochanek
- Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA, 15261, USA.,Safar Center for Resuscitation Research, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Critical Care Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Anesthesiology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,Clinical and Translational Science Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yvette P Conley
- Clinical and Translational Science Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,School of Nursing, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA, USA
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45
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Knowlton C, Kutterer S, Roeper J, Canavier CC. Calcium dynamics control K-ATP channel-mediated bursting in substantia nigra dopamine neurons: a combined experimental and modeling study. J Neurophysiol 2017; 119:84-95. [PMID: 28978764 DOI: 10.1152/jn.00351.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Burst firing in medial substantia nigra (mSN) dopamine (DA) neurons has been selectively linked to novelty-induced exploration behavior in mice. Burst firing in mSN DA neurons, in contrast to lateral SN DA neurons, requires functional ATP-sensitive potassium (K-ATP) channels both in vitro and in vivo. However, the precise role of K-ATP channels in promoting burst firing is unknown. We show experimentally that L-type calcium channel activity in mSN DA neurons enhances open probability of K-ATP channels. We then generate a mathematical model to study the role of Ca2+ dynamics driving K-ATP channel function in mSN DA neurons during bursting. In our model, Ca2+ influx leads to local accumulation of ADP due to Ca-ATPase activity, which in turn activates K-ATP channels. If K-ATP channel activation reaches levels sufficient to terminate spiking, rhythmic bursting occurs. The model explains the experimental observation that, in vitro, coapplication of NMDA and a selective K-ATP channel opener, NN414, is required to elicit bursting as follows. Simulated NMDA receptor activation increases the firing rate and the rate of Ca2+ influx, which increases the activation of K-ATP. The model suggests that additional sources of hyperpolarization, such as GABAergic synaptic input, are recruited in vivo for burst termination or rebound burst discharge. The model predicts that NN414 increases the sensitivity of the K-ATP channel to ADP, promoting burst firing in vitro, and that that high levels of Ca2+ buffering, as might be expected in the calbindin-positive SN DA neuron subpopulation, promote rhythmic bursting pattern, consistent with experimental observations in vivo. NEW & NOTEWORTHY Recently identified distinct subpopulations of midbrain dopamine neurons exhibit differences in their two primary activity patterns in vivo: tonic (single spike) firing and phasic bursting. This study elucidates the biophysical basis of bursts specific to dopamine neurons in the medial substantia nigra, enabled by ATP-sensitive K+ channels and necessary for novelty-induced exploration. A better understanding of how dopaminergic signaling differs between subpopulations may lead to therapeutic strategies selectively targeted to specific subpopulations.
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Affiliation(s)
- Christopher Knowlton
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center , New Orleans, Louisiana
| | - Sylvie Kutterer
- Institut für Neurophysiologie, Goethe University , Frankfurt , Germany
| | - Jochen Roeper
- Institut für Neurophysiologie, Goethe University , Frankfurt , Germany
| | - Carmen C Canavier
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center , New Orleans, Louisiana
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46
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Locher KP. Mechanistic diversity in ATP-binding cassette (ABC) transporters. Nat Struct Mol Biol 2017; 23:487-93. [PMID: 27273632 DOI: 10.1038/nsmb.3216] [Citation(s) in RCA: 518] [Impact Index Per Article: 74.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 03/30/2016] [Indexed: 12/18/2022]
Abstract
ABC transporters catalyze transport reactions, such as the high-affinity uptake of micronutrients into bacteria and the export of cytotoxic compounds from mammalian cells. Crystal structures of ABC domains and full transporters have provided a framework for formulating reaction mechanisms of ATP-driven substrate transport, but recent studies have suggested remarkable mechanistic diversity within this protein family. This review evaluates the differing mechanistic proposals and outlines future directions for the exploration of ABC-transporter-catalyzed reactions.
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Affiliation(s)
- Kaspar P Locher
- Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zurich, Zurich, Switzerland
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47
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Fettelschoss V, Burda P, Sagné C, Coelho D, De Laet C, Lutz S, Suormala T, Fowler B, Pietrancosta N, Gasnier B, Bornhauser B, Froese DS, Baumgartner MR. Clinical or ATPase domain mutations in ABCD4 disrupt the interaction between the vitamin B 12-trafficking proteins ABCD4 and LMBD1. J Biol Chem 2017; 292:11980-11991. [PMID: 28572511 DOI: 10.1074/jbc.m117.784819] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/24/2017] [Indexed: 01/19/2023] Open
Abstract
Vitamin B12 (cobalamin (Cbl)), in the cofactor forms methyl-Cbl and adenosyl-Cbl, is required for the function of the essential enzymes methionine synthase and methylmalonyl-CoA mutase, respectively. Cbl enters mammalian cells by receptor-mediated endocytosis of protein-bound Cbl followed by lysosomal export of free Cbl to the cytosol and further processing to these cofactor forms. The integral membrane proteins LMBD1 and ABCD4 are required for lysosomal release of Cbl, and mutations in the genes LMBRD1 and ABCD4 result in the cobalamin metabolism disorders cblF and cblJ. We report a new (fifth) patient with the cblJ disorder who presented at 7 days of age with poor feeding, hypotonia, methylmalonic aciduria, and elevated plasma homocysteine and harbored the mutations c.1667_1668delAG [p.Glu556Glyfs*27] and c.1295G>A [p.Arg432Gln] in the ABCD4 gene. Cbl cofactor forms are decreased in fibroblasts from this patient but could be rescued by overexpression of either ABCD4 or, unexpectedly, LMBD1. Using a sensitive live-cell FRET assay, we demonstrated selective interaction between ABCD4 and LMBD1 and decreased interaction when ABCD4 harbored the patient mutations p.Arg432Gln or p.Asn141Lys or when artificial mutations disrupted the ATPase domain. Finally, we showed that ABCD4 lysosomal targeting depends on co-expression of, and interaction with, LMBD1. These data broaden the patient and mutation spectrum of cblJ deficiency, establish a sensitive live-cell assay to detect the LMBD1-ABCD4 interaction, and confirm the importance of this interaction for proper intracellular targeting of ABCD4 and cobalamin cofactor synthesis.
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Affiliation(s)
- Victoria Fettelschoss
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - Patricie Burda
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - Corinne Sagné
- Neurophotonics Laboratory UMR 8250, Paris Descartes University, CNRS, Sorbonne Paris Cité, F-75006 Paris, France
| | - David Coelho
- UMR-S UL-INSERM U954 Nutrition-Genetics-Environmental Risk Exposure and Reference Centre of Inborn Metabolism Diseases, Medical Faculty of Nancy University and University Hospital Centre, Nancy, France
| | - Corinne De Laet
- Nutrition and Metabolism Unit, Queen Fabiola Children's University Hospital, Free University of Brussels (ULB), 1020 Brussels, Belgium
| | - Seraina Lutz
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - Terttu Suormala
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - Brian Fowler
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - Nicolas Pietrancosta
- CBMIT team, UMR 8601, Paris Descartes University, CNRS, Sorbonne Paris Cité, F-75006 Paris, France
| | - Bruno Gasnier
- Neurophotonics Laboratory UMR 8250, Paris Descartes University, CNRS, Sorbonne Paris Cité, F-75006 Paris, France
| | - Beat Bornhauser
- Department of Oncology, Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland
| | - D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland; Rare Disease Initiative Zurich (radiz), Clinical Research Priority Program for Rare Diseases, University of Zurich, CH-8006 Zurich, Switzerland.
| | - Matthias R Baumgartner
- Division of Metabolism and Children's Research Center, University Children's Hospital, CH-8032 Zurich, Switzerland; Rare Disease Initiative Zurich (radiz), Clinical Research Priority Program for Rare Diseases, University of Zurich, CH-8006 Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, CH-8006 Zurich, Switzerland.
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48
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Structure of the MacAB-TolC ABC-type tripartite multidrug efflux pump. Nat Microbiol 2017; 2:17070. [PMID: 28504659 PMCID: PMC5447821 DOI: 10.1038/nmicrobiol.2017.70] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/03/2017] [Indexed: 02/02/2023]
Abstract
The MacA-MacB-TolC assembly of Escherichia coli is a transmembrane machine that spans the cell envelope and actively extrudes substrates, including macrolide antibiotics and polypeptide virulence factors. These transport processes are energized by the ATPase MacB, a member of the ATP-binding cassette (ABC) superfamily. We present an electron cryo-microscopy structure of the ABC-type tripartite assembly at near-atomic resolution. A hexamer of the periplasmic protein MacA bridges between a TolC trimer in the outer membrane and a MacB dimer in the inner membrane, generating a quaternary structure with a central channel for substrate translocation. A gating ring found in MacA is proposed to act as a one-way valve in substrate transport. The MacB structure features an atypical transmembrane domain with a closely packed dimer interface and a periplasmic opening that is the likely portal for substrate entry from the periplasm, with subsequent displacement through an allosteric transport mechanism.
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49
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Abstract
The pancreatic β-cell secretes insulin in response to elevated plasma glucose. This review applies an external bioenergetic critique to the central processes of glucose-stimulated insulin secretion, including glycolytic and mitochondrial metabolism, the cytosolic adenine nucleotide pool, and its interaction with plasma membrane ion channels. The control mechanisms responsible for the unique responsiveness of the cell to glucose availability are discussed from bioenergetic and metabolic control standpoints. The concept of coupling factor facilitation of secretion is critiqued, and an attempt is made to unravel the bioenergetic basis of the oscillatory mechanisms controlling secretion. The need to consider the physiological constraints operating in the intact cell is emphasized throughout. The aim is to provide a coherent pathway through an extensive, complex, and sometimes bewildering literature, particularly for those unfamiliar with the field.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Research on Aging, Novato, California; and Department of Clinical Sciences, Unit of Molecular Metabolism, Lund University Diabetes Centre, Malmo, Sweden
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50
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Alvarez CP, Stagljar M, Muhandiram DR, Kanelis V. Hyperinsulinism-Causing Mutations Cause Multiple Molecular Defects in SUR1 NBD1. Biochemistry 2017; 56:2400-2416. [PMID: 28346775 DOI: 10.1021/acs.biochem.6b00681] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The sulfonylurea receptor 1 (SUR1) protein forms the regulatory subunit in ATP sensitive K+ (KATP) channels in the pancreas. SUR proteins are members of the ATP binding cassette (ABC) superfamily of proteins. Binding and hydrolysis of MgATP at the SUR nucleotide binding domains (NBDs) lead to channel opening. Pancreatic KATP channels play an important role in insulin secretion. SUR1 mutations that result in increased levels of channel opening ultimately inhibit insulin secretion and lead to neonatal diabetes. In contrast, SUR1 mutations that disrupt trafficking and/or decrease gating of KATP channels cause congenital hyperinsulinism, where oversecretion of insulin occurs even in the presence of low glucose levels. Here, we present data on the effects of specific congenital hyperinsulinism-causing mutations (G716V, R842G, and K890T) located in different regions of the first nucleotide binding domain (NBD1). Nuclear magnetic resonance (NMR) and fluorescence data indicate that the K890T mutation affects residues throughout NBD1, including residues that bind MgATP, NBD2, and coupling helices. The mutations also decrease the MgATP binding affinity of NBD1. Size exclusion and NMR data indicate that the G716V and R842G mutations cause aggregation of NBD1 in vitro, possibly because of destabilization of the domain. These data describe structural characterization of SUR1 NBD1 and shed light on the underlying molecular basis of mutations that cause congenital hyperinsulinism.
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Affiliation(s)
- Claudia P Alvarez
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Marijana Stagljar
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.,Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - D Ranjith Muhandiram
- Department of Molecular Genetics, University of Toronto , 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Voula Kanelis
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.,Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
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