1
|
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.
Collapse
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
| |
Collapse
|
2
|
Li K, Li Y, Chen Y, Chen T, Yang Y, Li P. Ion Channels Remodeling in the Regulation of Vascular Hyporesponsiveness During Shock. Microcirculation 2024:e12874. [PMID: 39011763 DOI: 10.1111/micc.12874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 04/07/2024] [Accepted: 06/16/2024] [Indexed: 07/17/2024]
Abstract
Shock is characterized with vascular hyporesponsiveness to vasoconstrictors, thereby to cause refractory hypotension, insufficient tissue perfusion, and multiple organ dysfunction. The vascular hyporeactivity persisted even though norepinephrine and fluid resuscitation were administrated, it is of critical importance to find new potential target. Ion channels are crucial in the regulation of cell membrane potential and affect vasoconstriction and vasodilation. It has been demonstrated that many types of ion channels including K+ channels, Ca2+ permeable channels, and Na+ channels exist in vascular smooth muscle cells and endothelial cells, contributing to the regulation of vascular homeostasis and vasomotor function. An increasing number of studies suggested that the structural and functional alterations of ion channels located in arteries contribute to vascular hyporesponsiveness during shock, but the underlying mechanisms remained to be fully clarified. Therefore, the expression and functional changes in ion channels in arteries associated with shock are reviewed, to pave the way for further exploring the potential of ion channel-targeted compounds in treating refractory hypotension in shock.
Collapse
Affiliation(s)
- Keqing Li
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yuan Li
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yinghong Chen
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Tangting Chen
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yan Yang
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Pengyun Li
- The Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| |
Collapse
|
3
|
Zhong G, Zhao Y, Zhuang D, Chung WK, Shen Y. PreMode predicts mode-of-action of missense variants by deep graph representation learning of protein sequence and structural context. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.20.581321. [PMID: 38746140 PMCID: PMC11092447 DOI: 10.1101/2024.02.20.581321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Accurate prediction of the functional impact of missense variants is important for disease gene discovery, clinical genetic diagnostics, therapeutic strategies, and protein engineering. Previous efforts have focused on predicting a binary pathogenicity classification, but the functional impact of missense variants is multi-dimensional. Pathogenic missense variants in the same gene may act through different modes of action (i.e., gain/loss-of-function) by affecting different aspects of protein function. They may result in distinct clinical conditions that require different treatments. We developed a new method, PreMode, to perform gene-specific mode-of-action predictions. PreMode models effects of coding sequence variants using SE(3)-equivariant graph neural networks on protein sequences and structures. Using the largest-to-date set of missense variants with known modes of action, we showed that PreMode reached state-of-the-art performance in multiple types of mode-of-action predictions by efficient transfer-learning. Additionally, PreMode's prediction of G/LoF variants in a kinase is consistent with inactive-active conformation transition energy changes. Finally, we show that PreMode enables efficient study design of deep mutational scans and optimization in protein engineering.
Collapse
|
4
|
Vedovato N, Salguero MV, Greeley SAW, Yu CH, Philipson LH, Ashcroft FM. A loss-of-function mutation in KCNJ11 causing sulfonylurea-sensitive diabetes in early adult life. Diabetologia 2024; 67:940-951. [PMID: 38366195 PMCID: PMC10954967 DOI: 10.1007/s00125-024-06103-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/28/2023] [Indexed: 02/18/2024]
Abstract
AIMS/HYPOTHESIS The ATP-sensitive potassium (KATP) channel couples beta cell electrical activity to glucose-stimulated insulin secretion. Loss-of-function mutations in either the pore-forming (inwardly rectifying potassium channel 6.2 [Kir6.2], encoded by KCNJ11) or regulatory (sulfonylurea receptor 1, encoded by ABCC8) subunits result in congenital hyperinsulinism, whereas gain-of-function mutations cause neonatal diabetes. Here, we report a novel loss-of-function mutation (Ser118Leu) in the pore helix of Kir6.2 paradoxically associated with sulfonylurea-sensitive diabetes that presents in early adult life. METHODS A 31-year-old woman was diagnosed with mild hyperglycaemia during an employee screen. After three pregnancies, during which she was diagnosed with gestational diabetes, the patient continued to show elevated blood glucose and was treated with glibenclamide (known as glyburide in the USA and Canada) and metformin. Genetic testing identified a heterozygous mutation (S118L) in the KCNJ11 gene. Neither parent was known to have diabetes. We investigated the functional properties and membrane trafficking of mutant and wild-type KATP channels in Xenopus oocytes and in HEK-293T cells, using patch-clamp, two-electrode voltage-clamp and surface expression assays. RESULTS Functional analysis showed no changes in the ATP sensitivity or metabolic regulation of the mutant channel. However, the Kir6.2-S118L mutation impaired surface expression of the KATP channel by 40%, categorising this as a loss-of-function mutation. CONCLUSIONS/INTERPRETATION Our data support the increasing evidence that individuals with mild loss-of-function KATP channel mutations may develop insulin deficiency in early adulthood and even frank diabetes in middle age. In this case, the patient may have had hyperinsulinism that escaped detection in early life. Our results support the importance of functional analysis of KATP channel mutations in cases of atypical diabetes.
Collapse
Affiliation(s)
- Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, UK
| | - Maria V Salguero
- Departments of Medicine and Pediatrics, Section of Endocrinology Diabetes and Metabolism, University of Chicago, Chicago, IL, USA
| | - Siri Atma W Greeley
- Departments of Medicine and Pediatrics, Section of Endocrinology Diabetes and Metabolism, University of Chicago, Chicago, IL, USA
| | - Christine H Yu
- Division of Endocrinology, Department of Pediatric Medicine, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Louis H Philipson
- Departments of Medicine and Pediatrics, Section of Endocrinology Diabetes and Metabolism, University of Chicago, Chicago, IL, USA
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, UK.
| |
Collapse
|
5
|
Elangeeb ME, Elfaki I, Eleragi AMS, Ahmed EM, Mir R, Alzahrani SM, Bedaiwi RI, Alharbi ZM, Mir MM, Ajmal MR, Tayeb FJ, Barnawi J. Molecular Dynamics Simulation of Kir6.2 Variants Reveals Potential Association with Diabetes Mellitus. Molecules 2024; 29:1904. [PMID: 38675722 PMCID: PMC11054064 DOI: 10.3390/molecules29081904] [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: 03/07/2024] [Revised: 04/13/2024] [Accepted: 04/18/2024] [Indexed: 04/28/2024] Open
Abstract
Diabetes mellitus (DM) represents a problem for the healthcare system worldwide. DM has very serious complications such as blindness, kidney failure, and cardiovascular disease. In addition to the very bad socioeconomic impacts, it influences patients and their families and communities. The global costs of DM and its complications are huge and expected to rise by the year 2030. DM is caused by genetic and environmental risk factors. Genetic testing will aid in early diagnosis and identification of susceptible individuals or populations using ATP-sensitive potassium (KATP) channels present in different tissues such as the pancreas, myocardium, myocytes, and nervous tissues. The channels respond to different concentrations of blood sugar, stimulation by hormones, or ischemic conditions. In pancreatic cells, they regulate the secretion of insulin and glucagon. Mutations in the KCNJ11 gene that encodes the Kir6.2 protein (a major constituent of KATP channels) were reported to be associated with Type 2 DM, neonatal diabetes mellitus (NDM), and maturity-onset diabetes of the young (MODY). Kir6.2 harbors binding sites for ATP and phosphatidylinositol 4,5-diphosphate (PIP2). The ATP inhibits the KATP channel, while the (PIP2) activates it. A Kir6.2 mutation at tyrosine330 (Y330) was demonstrated to reduce ATP inhibition and predisposes to NDM. In this study, we examined the effect of mutations on the Kir6.2 structure using bioinformatics tools and molecular dynamic simulations (SIFT, PolyPhen, SNAP2, PANTHER, PhD&SNP, SNP&Go, I-Mutant, MuPro, MutPred, ConSurf, HOPE, and GROMACS). Our results indicated that M199R, R201H, R206H, and Y330H mutations influence Kir6.2 structure and function and therefore may cause DM. We conclude that MD simulations are useful techniques to predict the effects of mutations on protein structure. In addition, the M199R, R201H, R206H, and Y330H variant in the Kir6.2 protein may be associated with DM. These results require further verification in protein-protein interactions, Kir6.2 function, and case-control studies.
Collapse
Affiliation(s)
- Mohamed E. Elangeeb
- Department of Basic Medical Sciences, College of Applied Medical Sciences, University of Bisha, Bisha 61922, Saudi Arabia
| | - Imadeldin Elfaki
- Department of Biochemistry, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia; (S.M.A.); (M.R.A.)
| | - Ali M. S. Eleragi
- Department of Microbiology, College of Medicine, University of Bisha, Bisha 61922, Saudi Arabia;
| | - Elsadig Mohamed Ahmed
- Department of Medical Laboratory Sciences, College of Applied Medical Sciences, University of Bisha, Bisha 61922, Saudi Arabia;
- Department of Clinical Chemistry, Faculty of Medical Laboratory Sciences, University of El Imam El Mahdi, Kosti 27711, Sudan
| | - Rashid Mir
- Department of Medical Laboratory Technology, Prince Fahad Bin Sultan Chair for Biomedical Research, Faculty of Applied Medical Sciences, University of Tabuk, Tabuk 71491, Saudi Arabia; (R.M.); (R.I.B.); (Z.M.A.); (F.J.T.); (J.B.)
| | - Salem M. Alzahrani
- Department of Biochemistry, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia; (S.M.A.); (M.R.A.)
| | - Ruqaiah I. Bedaiwi
- Department of Medical Laboratory Technology, Prince Fahad Bin Sultan Chair for Biomedical Research, Faculty of Applied Medical Sciences, University of Tabuk, Tabuk 71491, Saudi Arabia; (R.M.); (R.I.B.); (Z.M.A.); (F.J.T.); (J.B.)
| | - Zeyad M. Alharbi
- Department of Medical Laboratory Technology, Prince Fahad Bin Sultan Chair for Biomedical Research, Faculty of Applied Medical Sciences, University of Tabuk, Tabuk 71491, Saudi Arabia; (R.M.); (R.I.B.); (Z.M.A.); (F.J.T.); (J.B.)
| | - Mohammad Muzaffar Mir
- Department of Clinical Biochemistry, College of Medicine, University of Bisha, Bisha 61922, Saudi Arabia;
| | - Mohammad Rehan Ajmal
- Department of Biochemistry, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia; (S.M.A.); (M.R.A.)
| | - Faris Jamal Tayeb
- Department of Medical Laboratory Technology, Prince Fahad Bin Sultan Chair for Biomedical Research, Faculty of Applied Medical Sciences, University of Tabuk, Tabuk 71491, Saudi Arabia; (R.M.); (R.I.B.); (Z.M.A.); (F.J.T.); (J.B.)
| | - Jameel Barnawi
- Department of Medical Laboratory Technology, Prince Fahad Bin Sultan Chair for Biomedical Research, Faculty of Applied Medical Sciences, University of Tabuk, Tabuk 71491, Saudi Arabia; (R.M.); (R.I.B.); (Z.M.A.); (F.J.T.); (J.B.)
| |
Collapse
|
6
|
Galetin A, Brouwer KLR, Tweedie D, Yoshida K, Sjöstedt N, Aleksunes L, Chu X, Evers R, Hafey MJ, Lai Y, Matsson P, Riselli A, Shen H, Sparreboom A, Varma MVS, Yang J, Yang X, Yee SW, Zamek-Gliszczynski MJ, Zhang L, Giacomini KM. Membrane transporters in drug development and as determinants of precision medicine. Nat Rev Drug Discov 2024; 23:255-280. [PMID: 38267543 DOI: 10.1038/s41573-023-00877-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2023] [Indexed: 01/26/2024]
Abstract
The effect of membrane transporters on drug disposition, efficacy and safety is now well recognized. Since the initial publication from the International Transporter Consortium, significant progress has been made in understanding the roles and functions of transporters, as well as in the development of tools and models to assess and predict transporter-mediated activity, toxicity and drug-drug interactions (DDIs). Notable advances include an increased understanding of the effects of intrinsic and extrinsic factors on transporter activity, the application of physiologically based pharmacokinetic modelling in predicting transporter-mediated drug disposition, the identification of endogenous biomarkers to assess transporter-mediated DDIs and the determination of the cryogenic electron microscopy structures of SLC and ABC transporters. This article provides an overview of these key developments, highlighting unanswered questions, regulatory considerations and future directions.
Collapse
Affiliation(s)
- Aleksandra Galetin
- Centre for Applied Pharmacokinetic Research, School of Health Sciences, The University of Manchester, Manchester, UK.
| | - Kim L R Brouwer
- Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | | | - Kenta Yoshida
- Clinical Pharmacology, Genentech Research and Early Development, South San Francisco, CA, USA
| | - Noora Sjöstedt
- Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
| | - Lauren Aleksunes
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ, USA
| | - Xiaoyan Chu
- Department of Pharmacokinetics, Dynamics, Metabolism, and Bioanalytics, Merck & Co., Inc., Rahway, NJ, USA
| | - Raymond Evers
- Preclinical Sciences and Translational Safety, Johnson & Johnson, Janssen Pharmaceuticals, Spring House, PA, USA
| | - Michael J Hafey
- Department of Pharmacokinetics, Dynamics, Metabolism, and Bioanalytics, Merck & Co., Inc., Rahway, NJ, USA
| | - Yurong Lai
- Drug Metabolism, Gilead Sciences Inc., Foster City, CA, USA
| | - Pär Matsson
- Department of Pharmacology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Andrew Riselli
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA
| | - Hong Shen
- Department of Drug Metabolism and Pharmacokinetics, Bristol Myers Squibb Research and Development, Princeton, NJ, USA
| | - Alex Sparreboom
- Division of Pharmaceutics and Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Manthena V S Varma
- Pharmacokinetics, Dynamics and Metabolism, Medicine Design, Worldwide R&D, Pfizer Inc, Groton, CT, USA
| | - Jia Yang
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA
| | - Xinning Yang
- Office of Clinical Pharmacology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | - Sook Wah Yee
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA
| | | | - Lei Zhang
- Office of Research and Standards, Office of Generic Drugs, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, MD, USA
| | - Kathleen M Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA.
| |
Collapse
|
7
|
Driggers CM, Kuo YY, Zhu P, ElSheikh A, Shyng SL. Structure of an open K ATP channel reveals tandem PIP 2 binding sites mediating the Kir6.2 and SUR1 regulatory interface. Nat Commun 2024; 15:2502. [PMID: 38509107 PMCID: PMC10954709 DOI: 10.1038/s41467-024-46751-5] [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: 01/18/2024] [Accepted: 03/08/2024] [Indexed: 03/22/2024] Open
Abstract
ATP-sensitive potassium (KATP) channels, composed of four pore-lining Kir6.2 subunits and four regulatory sulfonylurea receptor 1 (SUR1) subunits, control insulin secretion in pancreatic β-cells. KATP channel opening is stimulated by PIP2 and inhibited by ATP. Mutations that increase channel opening by PIP2 reduce ATP inhibition and cause neonatal diabetes. Although considerable evidence has implicated a role for PIP2 in KATP channel function, previously solved open-channel structures have lacked bound PIP2, and mechanisms by which PIP2 regulates KATP channels remain unresolved. Here, we report the cryoEM structure of a KATP channel harboring the neonatal diabetes mutation Kir6.2-Q52R, in the open conformation, bound to amphipathic molecules consistent with natural C18:0/C20:4 long-chain PI(4,5)P2 at two adjacent binding sites between SUR1 and Kir6.2. The canonical PIP2 binding site is conserved among PIP2-gated Kir channels. The non-canonical PIP2 binding site forms at the interface of Kir6.2 and SUR1. Functional studies demonstrate both binding sites determine channel activity. Kir6.2 pore opening is associated with a twist of the Kir6.2 cytoplasmic domain and a rotation of the N-terminal transmembrane domain of SUR1, which widens the inhibitory ATP binding pocket to disfavor ATP binding. The open conformation is particularly stabilized by the Kir6.2-Q52R residue through cation-π bonding with SUR1-W51. Together, these results uncover the cooperation between SUR1 and Kir6.2 in PIP2 binding and gating, explain the antagonistic regulation of KATP channels by PIP2 and ATP, and provide a putative mechanism by which Kir6.2-Q52R stabilizes an open channel to cause neonatal diabetes.
Collapse
Affiliation(s)
- Camden M Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA.
| | - Yi-Ying Kuo
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Phillip Zhu
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Assmaa ElSheikh
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA.
| |
Collapse
|
8
|
Delgado-Bermúdez A, Yeste M, Bonet S, Pinart E. Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation. Andrology 2024. [PMID: 38436215 DOI: 10.1111/andr.13606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 01/16/2024] [Accepted: 01/29/2024] [Indexed: 03/05/2024]
Abstract
BACKGROUND Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ). MATERIAL-METHODS The present review includes recent findings on the role of potassium channels in sperm physiology of mammals. RESULTS-DISCUSSION While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs. CONCLUSIONS Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.
Collapse
Affiliation(s)
- Ariadna Delgado-Bermúdez
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Marc Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Sergi Bonet
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Elisabeth Pinart
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| |
Collapse
|
9
|
Hou T, Chen L. Sulfonylurea receptor 2 (SUR2), intricate sensors for intracellular Mg-nucleotides. Bioessays 2024; 46:e2300151. [PMID: 38227376 DOI: 10.1002/bies.202300151] [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: 08/16/2023] [Revised: 12/19/2023] [Accepted: 12/21/2023] [Indexed: 01/17/2024]
Abstract
SUR2, similar to SUR1, is a regulatory subunit of the ATP-sensitive potassium channel (KATP), which plays a key role in numerous important physiological processes and is implicated in various diseases. Recent structural studies have revealed that, like SUR1, SUR2 can undergo ligand-dependent dynamic conformational changes, transitioning between an inhibitory inward-facing conformation and an activating occluded conformation. In addition, SUR2 possesses a unique inhibitory Regulatory helix (R helix) that is absent in SUR1. The binding of the activating Mg-ADP to NBD2 of SUR2 competes with the inhibitory Mg-ATP, thereby promoting the release of the R helix and initiating the activation process. Moreover, the signal generated by Mg-ADP binding to NBD2 might be directly transmitted to the TMD of SUR2, prior to NBD dimerization. Furthermore, the C-terminal 42 residues (C42) of SUR2 might allosterically regulate the kinetics of Mg-nucleotide binding on NBD2. These distinctive properties render SUR2 intricate sensors for intracellular Mg-nucleotides.
Collapse
Affiliation(s)
- Tianyi Hou
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, 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, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, Beijing, China
| |
Collapse
|
10
|
Bauer N, Liu D, Nguyen T, Wang B. Unraveling the Interplay of Dopamine, Carbon Monoxide, and Heme Oxygenase in Neuromodulation and Cognition. ACS Chem Neurosci 2024; 15:400-407. [PMID: 38214656 PMCID: PMC10853931 DOI: 10.1021/acschemneuro.3c00742] [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: 11/15/2023] [Revised: 12/13/2023] [Accepted: 12/19/2023] [Indexed: 01/13/2024] Open
Abstract
The dopaminergic system plays important roles in neuromodulation, including prominent roles in complex neurological functions such as cognition, reward, motivation, and memory. Understandably, the highly complex nature of such physiological functions means that their regulation is intertwined with other signaling pathways, as has been demonstrated by numerous studies. Contrary to its public perception of being poisonous at all concentrations, carbon monoxide (CO) is produced endogenously from heme degradation by heme oxygenase (HO) as part of the physiological process of red blood cell turnover. Physiological concentrations of CO can reach high micromolar ranges in the hemoglobin bound form. Low-dose CO has shown therapeutic effects in numerous animal models, including traumatic brain injury via engaging various hemoprotein targets. As such, the HO-CO axis has been shown to offer beneficial effects in organ protection, anti-inflammation, and neuroprotection, among many others. Further, a large number of publications have shown the interactions among CO, HO, and the dopaminergic system. In this review, we critically examine such experimental evidence in a holistic fashion and in the context of a possible dopamine-HO-CO signaling axis. We hope that this Perspective will stimulate additional investigations into the molecular connectivity related to this possible axis and open doors to the development of novel therapeutics that impact the dopaminergic system.
Collapse
Affiliation(s)
- Nicola Bauer
- Department of Chemistry and
Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303, United States
| | - Dongning Liu
- Department of Chemistry and
Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303, United States
| | - TanPhat Nguyen
- Department of Chemistry and
Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303, United States
| | - Binghe Wang
- Department of Chemistry and
Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303, United States
| |
Collapse
|
11
|
Longden TA, Lederer WJ. Electro-metabolic signaling. J Gen Physiol 2024; 156:e202313451. [PMID: 38197953 PMCID: PMC10783436 DOI: 10.1085/jgp.202313451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/27/2023] [Accepted: 12/14/2023] [Indexed: 01/11/2024] Open
Abstract
Precise matching of energy substrate delivery to local metabolic needs is essential for the health and function of all tissues. Here, we outline a mechanistic framework for understanding this critical process, which we refer to as electro-metabolic signaling (EMS). All tissues exhibit changes in metabolism over varying spatiotemporal scales and have widely varying energetic needs and reserves. We propose that across tissues, common signatures of elevated metabolism or increases in energy substrate usage that exceed key local thresholds rapidly engage mechanisms that generate hyperpolarizing electrical signals in capillaries that then relax contractile elements throughout the vasculature to quickly adjust blood flow to meet changing needs. The attendant increase in energy substrate delivery serves to meet local metabolic requirements and thus avoids a mismatch in supply and demand and prevents metabolic stress. We discuss in detail key examples of EMS that our laboratories have discovered in the brain and the heart, and we outline potential further EMS mechanisms operating in tissues such as skeletal muscle, pancreas, and kidney. We suggest that the energy imbalance evoked by EMS uncoupling may be central to cellular dysfunction from which the hallmarks of aging and metabolic diseases emerge and may lead to generalized organ failure states-such as diverse flavors of heart failure and dementia. Understanding and manipulating EMS may be key to preventing or reversing these dysfunctions.
Collapse
Affiliation(s)
- Thomas A. Longden
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W. Jonathan Lederer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Molecular Cardiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
| |
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
Pan E, Tao F, Smorodina E, Zhang S. Structural bioinformatics studies of six human ABC transporters and their AlphaFold2-predicted water-soluble QTY variants. QRB DISCOVERY 2024; 5:e1. [PMID: 38577032 PMCID: PMC10988169 DOI: 10.1017/qrd.2024.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/29/2023] [Accepted: 12/12/2023] [Indexed: 04/06/2024] Open
Abstract
Human ATP-binding cassette (ABC) transporters are one of the largest families of membrane proteins and perform diverse functions. Many of them are associated with multidrug resistance that often results in cancer treatment with poor outcomes. Here, we present the structural bioinformatics study of six human ABC membrane transporters with experimentally determined cryo-electron microscopy (CryoEM) structures including ABCB7, ABCC8, ABCD1, ABCD4, ABCG1, ABCG5, and their AlphaFold2-predicted water-soluble QTY variants. In the native structures, there are hydrophobic amino acids such as leucine (L), isoleucine (I), valine (V), and phenylalanine (F) in the transmembrane alpha helices. These hydrophobic amino acids are systematically replaced by hydrophilic amino acids glutamine (Q), threonine (T), and tyrosine (Y). Therefore, these QTY variants become water soluble. We also present the superposed structures of native ABC transporters and their water-soluble QTY variants. The superposed structures show remarkable similarity with root mean square deviations between 1.064 and 3.413 Å despite significant (41.90-54.33%) changes to the protein sequence of the transmembrane domains. We also show the differences in hydrophobicity patches between the native ABC transporters and their QTY variants. We explain the rationale behind why the QTY membrane protein variants become water soluble. Our structural bioinformatics studies provide insight into the differences between the hydrophobic helices and hydrophilic helices and will likely further stimulate designs of water-soluble multispan transmembrane proteins and other aggregated proteins. The water-soluble ABC transporters may be useful as soluble antigens to generate therapeutic monoclonal antibodies for combating multidrug resistance in clinics.
Collapse
Affiliation(s)
- Emily Pan
- The Lawrenceville School, Lawrenceville, NJ, USA
| | - Fei Tao
- Laboratory of Food Microbial Technology, State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Eva Smorodina
- Laboratory for Computational and Systems Immunology, Department of Immunology, University of Oslo, Oslo University Hospital, Oslo, Norway
| | - Shuguang Zhang
- Laboratory of Molecular Architecture, Media Lab, Massachusetts Institute of Technology, Cambridge, MA, USA
| |
Collapse
|
14
|
Driggers CM, Kuo YY, Zhu P, ElSheikh A, Shyng SL. Structure of an open K ATP channel reveals tandem PIP 2 binding sites mediating the Kir6.2 and SUR1 regulatory interface. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.01.551546. [PMID: 37577494 PMCID: PMC10418277 DOI: 10.1101/2023.08.01.551546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
ATP-sensitive potassium (K ATP ) channels, composed of four pore-lining Kir6.2 subunits and four regulatory sulfonylurea receptor 1 (SUR1) subunits, control insulin secretion in pancreatic β-cells. K ATP channel opening is stimulated by PIP 2 and inhibited by ATP. Mutations that increase channel opening by PIP 2 reduce ATP inhibition and cause neonatal diabetes. Although considerable evidence has indicated PIP 2 in K ATP channel function, previously solved open-channel structures have lacked bound PIP 2 , and mechanisms by which PIP 2 regulates K ATP channels remain unresolved. Here, we report the cryoEM structure of a K ATP channel harboring the neonatal diabetes mutation Kir6.2-Q52R, bound to natural C18:0/C20:4 long-chain PIP 2 in an open conformation. The structure reveals two adjacent PIP 2 molecules between SUR1 and Kir6.2. The first PIP 2 binding site is conserved among PIP 2 -gated Kir channels. The second site forms uniquely in K ATP at the interface of Kir6.2 and SUR1. Functional studies demonstrate both binding sites determine channel activity. Kir6.2 pore opening is associated with a twist of the Kir6.2 cytoplasmic domain and a rotation of the N-terminal transmembrane domain of SUR1, which widens the inhibitory ATP binding pocket to disfavor ATP binding. The open conformation is particularly stabilized by the Kir6.2-Q52R residue through cation-π bonding with SUR1-W51. Together, these results uncover the cooperation between SUR1 and Kir6.2 in PIP 2 binding and gating, explain the antagonistic regulation of K ATP channels by PIP 2 and ATP, and provide the mechanism by which Kir6.2-Q52R stabilizes an open channel to cause neonatal diabetes.
Collapse
|
15
|
Su W, Li Y, Chang AK, Sheng T, Pei Y, Li J, Li H, Liu K, Xu L, Liu W, Ai J, Zhang Z, Wang Y, Jiang Z, Liang X. Identification of Novel Alkaloids from Portulaca oleracea L. and Characterization of Their Pharmacokinetics and GLP-1 Secretion-Promoting Activity in STC-1 Cells. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:19804-19816. [PMID: 38038649 DOI: 10.1021/acs.jafc.3c05191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Six new alkaloids (compounds 1-6) were isolated from Portulaca oleracea L. The compounds were triple pair (1 and 2, 3 and 4, and 5 and 6) enantiomers, with 1, 3, and 5 in the R-configuration and 2, 4, and 6 in the S-configuration, and all could bind to SUR1 according to molecular docking analysis. Treatment of STC-1 cells with each compound led to an influx of intracellular Ca2+, eventually leading to the secretion of glucagon-like peptide-1 (GLP-1), with compound 3 giving the highest secretion, resulting in 24.3 ± 7.03% more GLP-1 than nateglinide-treated cells, suggesting that these alkaloids may be able to reduce blood glucose based on their ability to stimulate the release of GLP-1. Furthermore, compound 3 also exhibited slightly faster absorption than nateglinide, as shown by pharmacokinetic analysis conducted in rats. Therefore, the results showed that some purslane alkaloids (such as compound 3) had good pharmacological activity in vivo and may have preventive and therapeutic effects on diabetes.
Collapse
Affiliation(s)
- Weiping Su
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Yanan Li
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Alan Kueichieh Chang
- College of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang Province 325035, P.R. China
| | - Tongling Sheng
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Ying Pei
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Jianxin Li
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Haoran Li
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Kai Liu
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Liuping Xu
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Wenbao Liu
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Jiao Ai
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Zhicheng Zhang
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Yimeng Wang
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| | - Zhen Jiang
- Department of Analytical Chemistry, College of Pharmacy, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang, Liaoning Province 110016, P.R. China
| | - Xiao Liang
- School of Pharmaceutical Sciences, Liaoning University, 66 Chongshan Road, Shenyang, Liaoning Province 110036, P.R. China
| |
Collapse
|
16
|
Wu W, Zheng J, Wang R, Wang Y. Ion channels regulate energy homeostasis and the progression of metabolic disorders: Novel mechanisms and pharmacology of their modulators. Biochem Pharmacol 2023; 218:115863. [PMID: 37863328 DOI: 10.1016/j.bcp.2023.115863] [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: 09/12/2023] [Revised: 10/13/2023] [Accepted: 10/16/2023] [Indexed: 10/22/2023]
Abstract
The progression of metabolic diseases, featured by dysregulated metabolic signaling pathways, is orchestrated by numerous signaling networks. Among the regulators, ion channels transport ions across the membranes and trigger downstream signaling transduction. They critically regulate energy homeostasis and pathogenesis of metabolic diseases and are potential therapeutic targets for treating metabolic disorders. Ion channel blockers have been used to treat diabetes for decades by stimulating insulin secretion, yet with hypoglycemia and other adverse effects. It calls for deeper understanding of the largely elusive regulatory mechanisms, which facilitates the identification of new therapeutic targets and safe drugs against ion channels. In the article, we critically assess the two principal regulatory mechanisms, protein-channel interaction and post-translational modification on the activities of ion channels to modulate energy homeostasis and metabolic disorders through multiple novel mechanisms. Moreover, we discuss the multidisciplinary methods that provide the tools for elucidation of the regulatory mechanisms mediating metabolic disorders by ion channels. In terms of translational perspective, the mechanistic analysis of recently validated ion channels that regulate insulin resistance, body weight control, and adverse effects of current ion channel antagonists are discussed in details. Their small molecule modulators serve as promising new drug candidates to combat metabolic disorders.
Collapse
Affiliation(s)
- Wenyi Wu
- School of Kinesiology, Shanghai University of Sport, Shanghai 200438, China
| | - Jianan Zheng
- School of Kinesiology, Shanghai University of Sport, Shanghai 200438, China
| | - Ru Wang
- School of Kinesiology, Shanghai University of Sport, Shanghai 200438, China; Shanghai Frontiers Science Research Base of Exercise and Metabolic Health, China
| | - Yibing Wang
- School of Kinesiology, Shanghai University of Sport, Shanghai 200438, China; Shanghai Frontiers Science Research Base of Exercise and Metabolic Health, China.
| |
Collapse
|
17
|
Lee CT, Tsai WH, Chang CC, Chen PC, Fann CSJ, Chang HK, Liu SY, Wu MZ, Chiu PC, Hsu WM, Yang WS, Lai LP, Tsai WY, Yang SB, Chen PL. Genotype-phenotype correlation in Taiwanese children with diazoxide-unresponsive congenital hyperinsulinism. Front Endocrinol (Lausanne) 2023; 14:1283907. [PMID: 38033998 PMCID: PMC10687152 DOI: 10.3389/fendo.2023.1283907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 10/23/2023] [Indexed: 12/02/2023] Open
Abstract
Objective Congenital hyperinsulinism (CHI) is a group of clinically and genetically heterogeneous disorders characterized by dysregulated insulin secretion. The aim of the study was to elucidate genetic etiologies of Taiwanese children with the most severe diazoxide-unresponsive CHI and analyze their genotype-phenotype correlations. Methods We combined Sanger with whole exome sequencing (WES) to analyze CHI-related genes. The allele frequency of the most common variant was estimated by single-nucleotide polymorphism haplotype analysis. The functional effects of the ATP-sensitive potassium (KATP) channel variants were assessed using patch clamp recording and Western blot. Results Nine of 13 (69%) patients with ten different pathogenic variants (7 in ABCC8, 2 in KCNJ11 and 1 in GCK) were identified by the combined sequencing. The variant ABCC8 p.T1042QfsX75 identified in three probands was located in a specific haplotype. Functional study revealed the human SUR1 (hSUR1)-L366F KATP channels failed to respond to intracellular MgADP and diazoxide while hSUR1-R797Q and hSUR1-R1393C KATP channels were defective in trafficking. One patient had a de novo dominant mutation in the GCK gene (p.I211F), and WES revealed mosaicism of this variant from another patient. Conclusion Pathogenic variants in KATP channels are the most common underlying cause of diazoxide-unresponsive CHI in the Taiwanese cohort. The p.T1042QfsX75 variant in the ABCC8 gene is highly suggestive of a founder effect. The I211F mutation in the GCK gene and three rare SUR1 variants associated with defective gating (p.L366F) or traffic (p.R797Q and p.R1393C) KATP channels are also associated with the diazoxide-unresponsive phenotype.
Collapse
Affiliation(s)
- Cheng-Ting Lee
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Hao Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | | | - Pei-Chun Chen
- Department of Physiology, National Cheng-Kung University, Tainan, Taiwan
| | | | - Hsueh-Kai Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Shih-Yao Liu
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Mu-Zon Wu
- Department of Pathology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Pao-Chin Chiu
- Department of Pediatrics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Wen-Ming Hsu
- Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wei-Shiung Yang
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ling-Ping Lai
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wen-Yu Tsai
- Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
| | - Shi-Bing Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Pei-Lung Chen
- Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan
| |
Collapse
|
18
|
Criveanu D, Bergqvist CA, Larhammar D, Walczewska-Szewc K. Identification of a new Kir6 potassium channel and comparison of properties of Kir6 subtypes by structural modelling and molecular dynamics. Int J Biol Macromol 2023; 247:125771. [PMID: 37433419 DOI: 10.1016/j.ijbiomac.2023.125771] [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: 02/16/2023] [Revised: 05/25/2023] [Accepted: 07/07/2023] [Indexed: 07/13/2023]
Abstract
ATP-sensitive potassium ion channels (KATP) are transmembrane proteins that modulate insulin release and muscle contraction. KATP channels are composed of two types of subunit, Kir6 and SUR, which exist in two and three isoforms respectively with different tissue distribution. In this work, we identify a previously undescribed ancestral vertebrate gene encoding a Kir6-related protein that we have named Kir6.3, which may not have a SUR binding partner, unlike the other two Kir6 proteins. Whereas Kir6.3 was lost in amniotes including mammals, it is still present in several early-diverging vertebrate lineages such as frogs, coelacanth, and rayfinned fishes. Molecular dynamics (MD) simulations using homology models of Kir6.1, Kir6.2, and Kir6.3 from the coelacanth Latimeria chalumnae showed that the three proteins exhibit subtle differences in their dynamics. Steered MD simulations of Kir6-SUR pairs suggest that Kir6.3 has a lower binding affinity for the SUR proteins than either Kir6.1 or Kir6.2. As we found no additional SUR gene in the genomes of the species that have Kir6.3, it most likely forms a lone tetramer. These findings invite studies of the tissue distribution of Kir6.3 in relation to the other Kir6 as well as SUR proteins to determine the functional roles of Kir6.3.
Collapse
Affiliation(s)
- Dan Criveanu
- School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK
| | - Christina A Bergqvist
- Department of Medical Cell Biology, Science for Life Laboratory, Biomedical Center Box 571, Uppsala University, SE-75123 Uppsala, Sweden
| | - Dan Larhammar
- Department of Medical Cell Biology, Science for Life Laboratory, Biomedical Center Box 571, Uppsala University, SE-75123 Uppsala, Sweden
| | - Katarzyna Walczewska-Szewc
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, 87-100 Toruń, Poland.
| |
Collapse
|
19
|
Maksaev G, Bründl-Jirout M, Stary-Weinzinger A, Zangerl-Plessl EM, Lee SJ, Nichols CG. Subunit gating resulting from individual protonation events in Kir2 channels. Nat Commun 2023; 14:4538. [PMID: 37507406 PMCID: PMC10382558 DOI: 10.1038/s41467-023-40058-7] [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: 04/07/2023] [Accepted: 07/10/2023] [Indexed: 07/30/2023] Open
Abstract
Inwardly rectifying potassium (Kir) channels open at the 'helix bundle crossing' (HBC), formed by the M2 helices at the cytoplasmic end of the transmembrane pore. Introduced negative charges at the HBC (G178D) in Kir2.2 channels forces opening, allowing pore wetting and free movement of permeant ions between the cytoplasm and the inner cavity. Single-channel recordings reveal striking, pH-dependent, subconductance behaviors in G178D (or G178E and equivalent Kir2.1[G177E]) mutant channels, with well-resolved non-cooperative subconductance levels. Decreasing cytoplasmic pH shifts the probability towards lower conductance levels. Molecular dynamics simulations show how protonation of Kir2.2[G178D], or the D173 pore-lining residues, changes solvation, K+ ion occupancy, and K+ conductance. Ion channel gating and conductance are classically understood as separate processes. The present data reveal how individual protonation events change the electrostatic microenvironment of the pore, resulting in step-wise alterations of ion pooling, and hence conductance, that appear as 'gated' substates.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Cell Biology and Physiology, and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael Bründl-Jirout
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Anna Stary-Weinzinger
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Eva-Maria Zangerl-Plessl
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria.
| | - Sun-Joo Lee
- Department of Cell Biology and Physiology, and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA.
| |
Collapse
|
20
|
Ding D, Hou T, Wei M, Wu JX, Chen L. The inhibition mechanism of the SUR2A-containing K ATP channel by a regulatory helix. Nat Commun 2023; 14:3608. [PMID: 37330603 PMCID: PMC10276813 DOI: 10.1038/s41467-023-39379-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 06/10/2023] [Indexed: 06/19/2023] Open
Abstract
KATP channels are metabolic sensors for intracellular ATP/ADP ratios, play essential roles in many physiological processes, and are implicated in a spectrum of pathological conditions. SUR2A-containing KATP channels differ from other subtypes in their sensitivity to Mg-ADP activation. However, the underlying structural mechanism remains poorly understood. Here we present a series of cryo-EM structures of SUR2A in the presence of different combinations of Mg-nucleotides and the allosteric inhibitor repaglinide. These structures uncover regulatory helix (R helix) on the NBD1-TMD2 linker, which wedges between NBD1 and NBD2. R helix stabilizes SUR2A in the NBD-separated conformation to inhibit channel activation. The competitive binding of Mg-ADP with Mg-ATP to NBD2 mobilizes the R helix to relieve such inhibition, allowing channel activation. The structures of SUR2B in similar conditions suggest that the C-terminal 42 residues of SUR2B enhance the structural dynamics of NBD2 and facilitate the dissociation of the R helix and the binding of Mg-ADP to NBD2, promoting NBD dimerization and subsequent channel activation.
Collapse
Affiliation(s)
- Dian Ding
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
- National Biomedical Imaging Center, Peking University, 100871, Beijing, China
| | - Tianyi Hou
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
- National Biomedical Imaging Center, Peking University, 100871, Beijing, China
| | - Miao Wei
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China
- National Biomedical Imaging Center, Peking University, 100871, Beijing, China
| | - Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China
- National Biomedical Imaging Center, Peking University, 100871, Beijing, 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, 100871, Beijing, China.
- Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China.
- National Biomedical Imaging Center, Peking University, 100871, Beijing, China.
| |
Collapse
|
21
|
Ashcroft FM. KATP Channels and the Metabolic Regulation of Insulin Secretion in Health and Disease: The 2022 Banting Medal for Scientific Achievement Award Lecture. Diabetes 2023; 72:693-702. [PMID: 37815796 PMCID: PMC10202764 DOI: 10.2337/dbi22-0030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 02/28/2023] [Indexed: 10/11/2023]
Abstract
Diabetes is characterized by elevation of plasma glucose due to an insufficiency of the hormone insulin and is associated with both inadequate insulin secretion and impaired insulin action. The Banting Medal for Scientific Achievement Commemorates the work of Sir Frederick Banting, a member of the team that first used insulin to treat a patient with diabetes almost exactly one hundred years ago on 11 January 1922. This article is based on my Banting lecture of 2022 and concerns the mechanism of glucose-stimulated insulin secretion from pancreatic β-cells, with an emphasis on the metabolic regulation of the KATP channel. This channel plays a central role in insulin release. Its closure in response to metabolically generated changes in the intracellular concentrations of ATP and MgADP stimulates β-cell electrical activity and insulin granule exocytosis. Activating mutations in KATP channel genes that impair the ability of the channel to respond to ATP give rise to neonatal diabetes. Impaired KATP channel regulation may also play a role in type 2 diabetes. I conjecture that KATP channel closure in response to glucose is reduced because of impaired glucose metabolism, which fails to generate a sufficient increase in ATP. Consequently, glucose-stimulated β-cell electrical activity is less. As ATP is also required for insulin granule exocytosis, both reduced exocytosis and less β-cell electrical activity may contribute to the reduction in insulin secretion. I emphasize that what follows is not a definitive review of the topic but a personal account of the contribution of my team to the field that is based on my Banting lecture.
Collapse
Affiliation(s)
- Frances M. Ashcroft
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, U.K
| |
Collapse
|
22
|
Abstract
ABC transporters are essential for cellular physiology. Humans have 48 ABC genes organized into seven distinct families. Of these genes, 44 (in five distinct families) encode for membrane transporters, of which several are involved in drug resistance and disease pathways resulting from transporter dysfunction. Over the last decade, advances in structural biology have vastly expanded our mechanistic understanding of human ABC transporter function, revealing details of their molecular arrangement, regulation, and interactions, facilitated in large part by advances in cryo-EM that have rendered hitherto inaccessible targets amenable to high-resolution structural analysis. As a result, experimentally determined structures of multiple members of each of the five families of ABC transporters in humans are now available. Here we review this recent progress, highlighting the physiological relevance of human ABC transporters and mechanistic insights gleaned from their direct structure determination. We also discuss the impact and limitations of model systems and structure prediction methods in understanding human ABC transporters and discuss current challenges and future research directions.
Collapse
Affiliation(s)
- Amer Alam
- The Hormel Institute, University of Minnesota, Austin, Minnesota, USA
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland;
| |
Collapse
|
23
|
Martin GM, Patton BL, Shyng SL. K ATP channels in focus: Progress toward a structural understanding of ligand regulation. Curr Opin Struct Biol 2023; 79:102541. [PMID: 36807078 PMCID: PMC10023423 DOI: 10.1016/j.sbi.2023.102541] [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: 10/05/2022] [Revised: 12/11/2022] [Accepted: 01/14/2023] [Indexed: 02/21/2023]
Abstract
KATP channels are hetero-octameric complexes of four inward rectifying potassium channels, Kir6.1 or Kir6.2, and four sulfonylurea receptors, SUR1, SUR2A, or SUR2B from the ABC transporter family. This unique combination enables KATP channels to couple intracellular ATP/ADP ratios, through gating, with membrane excitability, thus regulating a broad range of cellular activities. The prominence of KATP channels in human physiology, disease, and pharmacology has long attracted research interest. Since 2017, a steady flow of high-resolution KATP cryoEM structures has revealed complex and dynamic interactions between channel subunits and their ligands. Here, we highlight insights from recent structures that begin to provide mechanistic explanations for decades of experimental data and discuss the remaining knowledge gaps in our understanding of KATP channel regulation.
Collapse
Affiliation(s)
- Gregory M Martin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Bruce L Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA.
| |
Collapse
|
24
|
ElSheikh A, Shyng SL. K ATP channel mutations in congenital hyperinsulinism: Progress and challenges towards mechanism-based therapies. Front Endocrinol (Lausanne) 2023; 14:1161117. [PMID: 37056678 PMCID: PMC10086357 DOI: 10.3389/fendo.2023.1161117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in infancy/childhood and is a serious condition associated with severe recurrent attacks of hypoglycemia due to dysregulated insulin secretion. Timely diagnosis and effective treatment are crucial to prevent severe hypoglycemia that may lead to life-long neurological complications. In pancreatic β-cells, adenosine triphosphate (ATP)-sensitive K+ (KATP) channels are a central regulator of insulin secretion vital for glucose homeostasis. Genetic defects that lead to loss of expression or function of KATP channels are the most common cause of HI (KATP-HI). Much progress has been made in our understanding of the molecular genetics and pathophysiology of KATP-HI in the past decades; however, treatment remains challenging, in particular for patients with diffuse disease who do not respond to the KATP channel activator diazoxide. In this review, we discuss current approaches and limitations on the diagnosis and treatment of KATP-HI, and offer perspectives on alternative therapeutic strategies.
Collapse
Affiliation(s)
- Assmaa ElSheikh
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, United States
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, United States
| |
Collapse
|
25
|
Maksaev G, Bründl-Jirout M, Stary-Weinzinger A, Zangerl-Plessl EM, Lee SJ, Nichols CG. Subunit gating resulting from individual protonation events in Kir2 channels. RESEARCH SQUARE 2023:rs.3.rs-2640647. [PMID: 36993294 PMCID: PMC10055540 DOI: 10.21203/rs.3.rs-2640647/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Inwardly rectifying potassium (Kir) channels play a critical role in stabilizing the membrane potential, thus controlling numerous physiological phenomena in multiple tissues. Channel conductance is activated by cytoplasmic modulators that open the channel at the 'helix bundle crossing' (HBC), formed by the coming together of the M2 helices from each of the four subunits, at the cytoplasmic end of the transmembrane pore. We introduced a negative charge at the bundle crossing region (G178D) in classical inward rectifier Kir2.2 channel subunits that forces channel opening, allowing pore wetting and free movement of permeant ions between the cytoplasm and the inner cavity. Single-channel recordings reveal a striking pH-dependent subconductance behavior in G178D (or G178E and equivalent Kir2.1[G177E]) mutant channels that reflects individual subunit events. These subconductance levels are well resolved temporally and occur independently, with no evidence of cooperativity. Decreasing cytoplasmic pH shifts the probability towards lower conductance levels, and molecular dynamics simulations show how protonation of Kir2.2[G178D] and, additionally, the rectification controller (D173) pore-lining residues leads to changes in pore solvation, K+ ion occupancy, and ultimately K+ conductance. While subconductance gating has long been discussed, resolution and explanation have been lacking. The present data reveals how individual protonation events change the electrostatic microenvironment of the pore, resulting in distinct, uncoordinated, and relatively long-lasting conductance states, which depend on levels of ion pooling in the pore and the maintenance of pore wetting. Gating and conductance are classically understood as separate processes in ion channels. The remarkable sub-state gating behavior of these channels reveals how intimately connected 'gating' and 'conductance' are in reality.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael Bründl-Jirout
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Anna Stary-Weinzinger
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Eva-Maria Zangerl-Plessl
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | - Sun-Joo Lee
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| |
Collapse
|
26
|
Hernandez CC, Gimenez LE, Dahir NS, Peisley A, Cone RD. The unique structural characteristics of the Kir 7.1 inward rectifier potassium channel: a novel player in energy homeostasis control. Am J Physiol Cell Physiol 2023; 324:C694-C706. [PMID: 36717105 PMCID: PMC10026989 DOI: 10.1152/ajpcell.00335.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 01/12/2023] [Accepted: 01/13/2023] [Indexed: 02/01/2023]
Abstract
The inward rectifier potassium channel Kir7.1, encoded by the KCNJ13 gene, is a tetramer composed of two-transmembrane domain-spanning monomers, closer in homology to Kir channels associated with potassium transport such as Kir1.1, 1.2, and 1.3. Compared with other channels, Kir7.1 exhibits small unitary conductance and low dependence on external potassium. Kir7.1 channels also show a phosphatidylinositol 4,5-bisphosphate (PIP2) dependence for opening. Accordingly, retinopathy-associated Kir7.1 mutations mapped at the binding site for PIP2 resulted in channel gating defects leading to channelopathies such as snowflake vitreoretinal degeneration and Leber congenital amaurosis in blind patients. Lately, this channel's role in energy homeostasis was reported due to the direct interaction with the melanocortin type 4 receptor (MC4R) in the hypothalamus. As this channel seems to play a multipronged role in potassium homeostasis and neuronal excitability, we will discuss what is predicted from a structural viewpoint and its possible implications for hunger control.
Collapse
Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Luis E Gimenez
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Naima S Dahir
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Alys Peisley
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Roger D Cone
- Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States
| |
Collapse
|
27
|
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.
Collapse
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
| |
Collapse
|
28
|
Abstract
Ubiquitously expressed throughout the body, ATP-sensitive potassium (KATP) channels couple cellular metabolism to electrical activity in multiple tissues; their unique assembly as four Kir6 pore-forming subunits and four sulfonylurea receptor (SUR) subunits has resulted in a large armory of selective channel opener and inhibitor drugs. The spectrum of monogenic pathologies that result from gain- or loss-of-function mutations in these channels, and the potential for therapeutic correction of these pathologies, is now clear. However, while available drugs can be effective treatments for specific pathologies, cross-reactivity with the other Kir6 or SUR subfamily members can result in drug-induced versions of each pathology and may limit therapeutic usefulness. This review discusses the background to KATP channel physiology, pathology, and pharmacology and considers the potential for more specific or effective therapeutic agents.
Collapse
Affiliation(s)
- Colin G. Nichols
- Center for the Investigation of Membrane Excitability Diseases and Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, USA
| |
Collapse
|
29
|
Lee SJ, Maeda S, Gao J, Nichols CG. Oxidation Driven Reversal of PIP 2-dependent Gating in GIRK2 Channels. FUNCTION 2023; 4:zqad016. [PMID: 37168492 PMCID: PMC10165546 DOI: 10.1093/function/zqad016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/24/2023] [Accepted: 04/03/2023] [Indexed: 05/13/2023] Open
Abstract
Physiological activity of G protein gated inward rectifier K+ (GIRK, Kir3) channel, dynamically regulated by three key ligands, phosphoinositol-4,5-bisphosphate (PIP2), Gβγ, and Na+, underlies cellular electrical response to multiple hormones and neurotransmitters in myocytes and neurons. In a reducing environment, matching that inside cells, purified GIRK2 (Kir3.2) channels demonstrate low basal activity, and expected sensitivity to the above ligands. However, under oxidizing conditions, anomalous behavior emerges, including rapid loss of PIP2 and Na+-dependent activation and a high basal activity in the absence of any agonists, that is now paradoxically inhibited by PIP2. Mutagenesis identifies two cysteine residues (C65 and C190) as being responsible for the loss of PIP2 and Na+-dependent activity and the elevated basal activity, respectively. The results explain anomalous findings from earlier studies and illustrate the potential pathophysiologic consequences of oxidation on GIRK channel function, as well as providing insight to reversed ligand-dependence of Kir and KirBac channels.
Collapse
Affiliation(s)
| | - Shoji Maeda
- Department of Pharmacology, Medical School, University of Michigan, Ann Arbor, Michigan, USA
| | - Jian Gao
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| |
Collapse
|
30
|
Kollewe A, Schwarz Y, Oleinikov K, Raza A, Haupt A, Wartenberg P, Wyatt A, Boehm U, Ectors F, Bildl W, Zolles G, Schulte U, Bruns D, Flockerzi V, Fakler B. Subunit composition, molecular environment, and activation of native TRPC channels encoded by their interactomes. Neuron 2022; 110:4162-4175.e7. [PMID: 36257322 DOI: 10.1016/j.neuron.2022.09.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 08/15/2022] [Accepted: 09/23/2022] [Indexed: 12/24/2022]
Abstract
In the mammalian brain TRPC channels, a family of Ca2+-permeable cation channels, are involved in a variety of processes from neuronal growth and synapse formation to transmitter release, synaptic transmission and plasticity. The molecular appearance and operation of native TRPC channels, however, remained poorly understood. Here, we used high-resolution proteomics to show that TRPC channels in the rodent brain are macro-molecular complexes of more than 1 MDa in size that result from the co-assembly of the tetrameric channel core with an ensemble of interacting proteins (interactome). The core(s) of TRPC1-, C4-, and C5-containing channels are mostly heteromers with defined stoichiometries for each subtype, whereas TRPC3, C6, and C7 preferentially form homomers. In addition, TRPC1/C4/C5 channels may co-assemble with the metabotropic glutamate receptor mGluR1, thus guaranteeing both specificity and reliability of channel activation via the phospholipase-Ca2+ pathway. Our results unveil the subunit composition of native TRPC channels and resolve the molecular details underlying their activation.
Collapse
Affiliation(s)
- Astrid Kollewe
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Yvonne Schwarz
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Katharina Oleinikov
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Ahsan Raza
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Alexander Haupt
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Philipp Wartenberg
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Amanda Wyatt
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Ulrich Boehm
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Fabien Ectors
- Transgenic facility, FARAH Research Center, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium
| | - Wolfgang Bildl
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Gerd Zolles
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Uwe Schulte
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, Schänzlestr. 18, 79104 Freiburg, Germany
| | - Dieter Bruns
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany.
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, Schänzlestr. 18, 79104 Freiburg, Germany; Center for Basics in NeuroModulation, Breisacherstr. 4, 79106 Freiburg, Germany.
| |
Collapse
|
31
|
Baatallah N, Elbahnsi A, Chevalier B, Castanier S, Mornon JP, Pranke I, Edelman A, Sermet-Gaudelus I, Callebaut I, Hinzpeter A. Acting on the CFTR Membrane-Spanning Domains Interface Rescues Some Misfolded Mutants. Int J Mol Sci 2022; 23:ijms232416225. [PMID: 36555865 PMCID: PMC9780841 DOI: 10.3390/ijms232416225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/09/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022] Open
Abstract
ABC transporters are large membrane proteins sharing a complex architecture, which comprises two nucleotide-binding domains (NBDs) and two membrane-spanning domains (MSDs). These domains are susceptible to mutations affecting their folding and assembly. In the CFTR (ABCC7) protein, a groove has been highlighted in the MSD1 at the level of the membrane inner leaflet, containing both multiple mutations affecting folding and a binding site for pharmaco-chaperones that stabilize this region. This groove is also present in ABCB proteins, however it is covered by a short elbow helix, while in ABCC proteins it remains unprotected, due to a lower position of the elbow helix in the presence of the ABCC-specific lasso motif. Here, we identified a MSD1 second-site mutation located in the vicinity of the CFTR MSD1 groove that partially rescued the folding defect of cystic fibrosis causing mutations located within MSD1, while having no effect on the most frequent mutation, F508del, located within NBD1. A model of the mutated protein 3D structure suggests additional interaction between MSD1 and MSD2, strengthening the assembly at the level of the MSD intracellular loops. Altogether, these results provide insightful information in understanding key features of the folding and function of the CFTR protein in particular, and more generally, of type IV ABC transporters.
Collapse
Affiliation(s)
- Nesrine Baatallah
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Ahmad Elbahnsi
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Benoit Chevalier
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Solène Castanier
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Jean-Paul Mornon
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Iwona Pranke
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Aleksander Edelman
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Isabelle Sermet-Gaudelus
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Isabelle Callebaut
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
- Correspondence: (I.C.); (A.H.)
| | - Alexandre Hinzpeter
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
- Correspondence: (I.C.); (A.H.)
| |
Collapse
|
32
|
Lee SJ, Nichols CG. Seeing spermine blocking of K+ ion movement through inward rectifier Kir2.2 channels. J Gen Physiol 2022; 155:213764. [PMID: 36524992 PMCID: PMC9764022 DOI: 10.1085/jgp.202213144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Inwardly rectifier potassium (Kir) channels are a major potassium channel sub-class whose function is regulated by ligand-dependent gating and highly voltage-dependent block by polyamines. With molecular dynamics simulations over previously unattainable timescales, Jogini et al. (J. Gen. Physiol. https://doi.org/10.1085/jgp.202213085) provide unprecedented visualization of K+ conduction through open Kir2.2 channels and of the molecular details of channel block by spermine.
Collapse
Affiliation(s)
- Sun-Joo Lee
- Department of Cell Biology and Physiology, Center for Investigation of Membrane Excitability Diseases, Washington University in. St. Louis, St. Louis, MO, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Center for Investigation of Membrane Excitability Diseases, Washington University in. St. Louis, St. Louis, MO, USA,Correspondence to Colin G. Nichols:
| |
Collapse
|
33
|
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.
Collapse
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:
| |
Collapse
|
34
|
Fan G, Baker MR, Terry LE, Arige V, Chen M, Seryshev AB, Baker ML, Ludtke SJ, Yule DI, Serysheva II. Conformational motions and ligand-binding underlying gating and regulation in IP 3R channel. Nat Commun 2022; 13:6942. [PMID: 36376291 PMCID: PMC9663519 DOI: 10.1038/s41467-022-34574-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 10/28/2022] [Indexed: 11/16/2022] Open
Abstract
Inositol-1,4,5-trisphosphate receptors (IP3Rs) are activated by IP3 and Ca2+ and their gating is regulated by various intracellular messengers that finely tune the channel activity. Here, using single particle cryo-EM analysis we determined 3D structures of the nanodisc-reconstituted IP3R1 channel in two ligand-bound states. These structures provide unprecedented details governing binding of IP3, Ca2+ and ATP, revealing conformational changes that couple ligand-binding to channel opening. Using a deep-learning approach and 3D variability analysis we extracted molecular motions of the key protein domains from cryo-EM density data. We find that IP3 binding relies upon intrinsic flexibility of the ARM2 domain in the tetrameric channel. Our results highlight a key role of dynamic side chains in regulating gating behavior of IP3R channels. This work represents a stepping-stone to developing mechanistic understanding of conformational pathways underlying ligand-binding, activation and regulation of the channel.
Collapse
Affiliation(s)
- Guizhen Fan
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Mariah R Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Lara E Terry
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
| | - Vikas Arige
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
| | - Muyuan Chen
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Alexander B Seryshev
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Matthew L Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Steven J Ludtke
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - David I Yule
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA.
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA.
| |
Collapse
|
35
|
Pipatpolkai T, Usher SG, Vedovato N, Ashcroft FM, Stansfeld PJ. The dynamic interplay of PIP 2 and ATP in the regulation of the K ATP channel. J Physiol 2022; 600:4503-4519. [PMID: 36047384 PMCID: PMC9825998 DOI: 10.1113/jp283345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 08/04/2022] [Indexed: 01/11/2023] Open
Abstract
ATP-sensitive potassium (KATP ) channels couple the intracellular ATP concentration to insulin secretion. KATP channel activity is inhibited by ATP binding to the Kir6.2 tetramer and activated by phosphatidylinositol 4,5-bisphosphate (PIP2 ). Here, we use molecular dynamics simulation, electrophysiology and fluorescence spectroscopy to show that ATP and PIP2 occupy different binding pockets that share a single amino acid residue, K39. When both ligands are present, simulations suggest that K39 shows a greater preference to co-ordinate with PIP2 than with ATP. They also predict that a neonatal diabetes mutation at K39 (K39R) increases the number of hydrogen bonds formed between K39 and PIP2 , potentially accounting for the reduced ATP inhibition observed in electrophysiological experiments. Our work suggests that PIP2 and ATP interact allosterically to regulate KATP channel activity. KEY POINTS: The KATP channel is activated by the binding of phosphatidylinositol 4,5-bisphosphate (PIP2 ) lipids and inactivated by the binding of ATP. K39 has the potential to bind to both PIP2 and ATP. A mutation to this residue (K39R) results in neonatal diabetes. This study uses patch-clamp fluorometry, electrophysiology and molecular dynamics simulation. We show that PIP2 competes with ATP for K39, and this reduces channel inhibition by ATP. We show that K39R increases channel affinity to PIP2 by increasing the number of hydrogen bonds with PIP2 , when compared with the wild-type K39. This therefore decreases KATP channel inhibition by ATP.
Collapse
Affiliation(s)
- Tanadet Pipatpolkai
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOxfordshireUK
- Department of BiochemistryUniversity of OxfordOxfordOxfordshireUK
- OXION Initiative in Ion Channels and DiseaseUniversity of OxfordOxfordOxfordshireUK
- Science for Life LaboratoryDepartment of Applied PhysicsKTH Royal Institute of TechnologySolnaSweden
| | - Samuel G. Usher
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOxfordshireUK
- OXION Initiative in Ion Channels and DiseaseUniversity of OxfordOxfordOxfordshireUK
- Department of Drug Design and PharmacologyUniversity of CopenhagenCopenhagenDenmark
| | - Natascia Vedovato
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOxfordshireUK
| | - Frances M. Ashcroft
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOxfordshireUK
| | - Phillip J. Stansfeld
- School of Life SciencesUniversity of WarwickCoventryWarwickshireUK
- Department of ChemistryUniversity of WarwickCoventryWarwickshireUK
| |
Collapse
|
36
|
McClenaghan C, Nichols CG. Kir6.1 and SUR2B in Cantú syndrome. Am J Physiol Cell Physiol 2022; 323:C920-C935. [PMID: 35876283 PMCID: PMC9467476 DOI: 10.1152/ajpcell.00154.2022] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/07/2022] [Accepted: 07/07/2022] [Indexed: 12/25/2022]
Abstract
Kir6.1 and SUR2 are subunits of ATP-sensitive potassium (KATP) channels expressed in a wide range of tissues. Extensive study has implicated roles of these channel subunits in diverse physiological functions. Together they generate the predominant KATP conductance in vascular smooth muscle and are the target of vasodilatory drugs. Roles for Kir6.1/SUR2 dysfunction in disease have been suggested based on studies of animal models and human genetic discoveries. In recent years, it has become clear that gain-of-function (GoF) mutations in both genes result in Cantú syndrome (CS)-a complex, multisystem disorder. There is currently no targeted therapy for CS, but studies of mouse models of the disease reveal that pharmacological reversibility of cardiovascular and gastrointestinal pathologies can be achieved by administration of the KATP channel inhibitor, glibenclamide. Here we review the function, structure, and physiological and pathological roles of Kir6.1/SUR2B channels, with a focus on CS. Recent studies have led to much improved understanding of the underlying pathologies and the potential for treatment, but important questions remain: Can the study of genetically defined CS reveal new insights into Kir6.1/SUR2 function? Do these reveal new pathophysiological mechanisms that may be important in more common diseases? And is our pharmacological armory adequately stocked?
Collapse
Affiliation(s)
- Conor McClenaghan
- Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St. Louis, Missouri
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St. Louis, Missouri
| |
Collapse
|
37
|
Zúñiga L, Cayo A, González W, Vilos C, Zúñiga R. Potassium Channels as a Target for Cancer Therapy: Current Perspectives. Onco Targets Ther 2022; 15:783-797. [PMID: 35899081 PMCID: PMC9309325 DOI: 10.2147/ott.s326614] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 07/08/2022] [Indexed: 12/18/2022] Open
Abstract
Potassium (K+) channels are highly regulated membrane proteins that control the potassium ion flux and respond to different cellular stimuli. These ion channels are grouped into three major families, Kv (voltage-gated K+ channel), Kir (inwardly rectifying K+ channel) and K2P (two-pore K+ channels), according to the structure, to mediate the K+ currents. In cancer, alterations in K+ channel function can promote the acquisition of the so-called hallmarks of cancer – cell proliferation, resistance to apoptosis, metabolic changes, angiogenesis, and migratory capabilities – emerging as targets for the development of new therapeutic drugs. In this review, we focus our attention on the different K+ channels associated with the most relevant and prevalent cancer types. We summarize our knowledge about the potassium channels structure and function, their cancer dysregulated expression and discuss the K+ channels modulator and the strategies for designing new drugs.
Collapse
Affiliation(s)
- Leandro Zúñiga
- Laboratorio de Fisiología Molecular, Escuela de Medicina, Universidad de Talca, Talca, Chile.,Centro de Nanomedicina, Diagnóstico y Desarrollo de Fármacos (ND3), Escuela de Medicina, Universidad de Talca, Talca, Chile
| | - Angel Cayo
- Laboratorio de Fisiología Molecular, Escuela de Medicina, Universidad de Talca, Talca, Chile.,Centro de Nanomedicina, Diagnóstico y Desarrollo de Fármacos (ND3), Escuela de Medicina, Universidad de Talca, Talca, Chile
| | - Wendy González
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Cristian Vilos
- Centro de Nanomedicina, Diagnóstico y Desarrollo de Fármacos (ND3), Escuela de Medicina, Universidad de Talca, Talca, Chile.,Laboratory of Nanomedicine and Targeted Delivery, School of Medicine, Universidad de Talca, Talca, 3460000, Chile.,Center for The Development of Nanoscience & Nanotechnology (CEDENNA), Universidad de Santiago de Chile, Santiago, 8350709, Chile
| | - Rafael Zúñiga
- Laboratorio de Fisiología Molecular, Escuela de Medicina, Universidad de Talca, Talca, Chile.,Centro de Nanomedicina, Diagnóstico y Desarrollo de Fármacos (ND3), Escuela de Medicina, Universidad de Talca, Talca, Chile
| |
Collapse
|
38
|
Bränström R, Berglund E, Fröbom R, Leibiger IB, Leibiger B, Aspinwall CA, Larsson O, Berggren PO. Inward and outward currents of native and cloned K(ATP) channels (Kir6.2/SUR1) share single-channel kinetic properties. Biochem Biophys Rep 2022; 30:101260. [PMID: 35434386 PMCID: PMC9006676 DOI: 10.1016/j.bbrep.2022.101260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/03/2022] [Accepted: 04/04/2022] [Indexed: 11/02/2022] Open
Abstract
Background Methods Results Conclusions Outward K(ATP) channel currents are not grouped in bursts regardless of membrane potential. No differences in the number of kinetic states could be seen for single channels between native K(ATP) channels, Kir6.2ΔC26 alone and co-expressed with SUR1 for outward currents. K(ATP) channel open time for outward currents corresponds to burst duration for inward currents.
Collapse
|
39
|
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.
Collapse
|
40
|
Ding D, Wu JX, Duan X, Ma S, Lai L, Chen L. Structural identification of vasodilator binding sites on the SUR2 subunit. Nat Commun 2022; 13:2675. [PMID: 35562524 PMCID: PMC9106677 DOI: 10.1038/s41467-022-30428-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 04/28/2022] [Indexed: 11/09/2022] Open
Abstract
ATP-sensitive potassium channels (KATP), composed of Kir6 and SUR subunits, convert the metabolic status of the cell into electrical signals. Pharmacological activation of SUR2- containing KATP channels by class of small molecule drugs known as KATP openers leads to hyperpolarization of excitable cells and to vasodilation. Thus, KATP openers could be used to treat cardiovascular diseases. However, where these vasodilators bind to KATP and how they activate the channel remains elusive. Here, we present cryo-EM structures of SUR2A and SUR2B subunits in complex with Mg-nucleotides and P1075 or levcromakalim, two chemically distinct KATP openers that are specific to SUR2. Both P1075 and levcromakalim bind to a common site in the transmembrane domain (TMD) of the SUR2 subunit, which is between TMD1 and TMD2 and is embraced by TM10, TM11, TM12, TM14, and TM17. These KATP openers synergize with Mg-nucleotides to stabilize SUR2 in the NBD-dimerized occluded state to activate the channel.
Collapse
Affiliation(s)
- Dian Ding
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China.,Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China.,National Biomedical Imaging Center, Peking University, 100871, Beijing, China
| | - Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, 100871, Beijing, China.,National Biomedical Imaging Center, Peking University, 100871, Beijing, China
| | - Xinli Duan
- Beijing Jingtai Technology Co., Ltd., Beijing, China
| | - Songling Ma
- Beijing Jingtai Technology Co., Ltd., Beijing, China
| | - Lipeng Lai
- Beijing Jingtai Technology Co., Ltd., Beijing, 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, 100871, Beijing, China. .,Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China. .,Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China. .,National Biomedical Imaging Center, Peking University, 100871, Beijing, China.
| |
Collapse
|