1
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Patton BL, Zhu P, ElSheikh A, Driggers CM, Shyng SL. Dynamic duo: Kir6 and SUR in K ATP channel structure and function. Channels (Austin) 2024; 18:2327708. [PMID: 38489043 PMCID: PMC10950283 DOI: 10.1080/19336950.2024.2327708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 01/14/2024] [Indexed: 03/17/2024] Open
Abstract
KATP channels are ligand-gated potassium channels that couple cellular energetics with membrane potential to regulate cell activity. Each channel is an eight subunit complex comprising four central pore-forming Kir6 inward rectifier potassium channel subunits surrounded by four regulatory subunits known as the sulfonylurea receptor, SUR, which confer homeostatic metabolic control of KATP gating. SUR is an ATP binding cassette (ABC) protein family homolog that lacks membrane transport activity but is essential for KATP expression and function. For more than four decades, understanding the structure-function relationship of Kir6 and SUR has remained a central objective of clinical significance. Here, we review progress in correlating the wealth of functional data in the literature with recent KATP cryoEM structures.
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Affiliation(s)
- Bruce L. Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Phillip Zhu
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Assmaa ElSheikh
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Camden M. Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
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2
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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.
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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.
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3
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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.
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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.
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4
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Walczewska-Szewc K, Nowak W. Structural Insights into ATP-Sensitive Potassium Channel Mechanics: A Role of Intrinsically Disordered Regions. J Chem Inf Model 2023; 63:1806-1818. [PMID: 36746748 PMCID: PMC10052335 DOI: 10.1021/acs.jcim.2c01196] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Commonly used techniques, such as CryoEM or X-ray, are not able to capture the structural reorganizations of disordered regions of proteins (IDR); therefore, it is difficult to assess their functions in proteins based exclusively on experiments. To fill this gap, we used computational molecular dynamics (MD) simulation methods to capture IDR dynamics and trace biological function-related interactions in the Kir6.2/SUR1 potassium channel. This ATP-sensitive octameric complex, one of the critical elements in the insulin secretion process in human pancreatic β-cells, has four to five large, disordered fragments. Using unique MD simulations of the full Kir6.2/SUR1 channel complex, we present an in-depth analysis of the dynamics of the disordered regions and discuss the possible functions they could have in this system. Our MD results confirmed the crucial role of the N-terminus of the Kir6.2 fragment and the L0-loop of the SUR1 protein in the transfer of mechanical signals between domains that trigger insulin release. Moreover, we show that the presence of IDRs affects natural ligand binding. Our research takes us one step further toward understanding the action of this vital complex.
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Affiliation(s)
- Katarzyna Walczewska-Szewc
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Wiesław Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, 87-100 Toruń, Poland
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5
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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.
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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
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6
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Wang M, Wu JX, Chen L. Structural Insights Into the High Selectivity of the Anti-Diabetic Drug Mitiglinide. Front Pharmacol 2022; 13:929684. [PMID: 35847046 PMCID: PMC9279661 DOI: 10.3389/fphar.2022.929684] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 05/25/2022] [Indexed: 11/13/2022] Open
Abstract
Mitiglinide is a highly selective fast-acting anti-diabetic drug that induces insulin secretion by inhibiting pancreatic KATP channels. However, how mitiglinide binds KATP channels remains unknown. Here, we show the cryo-EM structure of the SUR1 subunit complexed with mitiglinide. The structure reveals that mitiglinide binds inside the common insulin secretagogue-binding site of SUR1, which is surrounded by TM7, TM8, TM16, and TM17. Mitiglinide locks SUR1 in the NBD-separated inward-facing conformation. The detailed structural analysis of the mitiglinide-binding site uncovers the molecular basis of its high selectivity.
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Affiliation(s)
- Mengmeng Wang
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
| | - Jing-Xiang Wu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
| | - Lei Chen
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, College of Future Technology, Institute of Molecular Medicine, Peking University, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- National Biomedical Imaging Center, Peking University, Beijing, China
- *Correspondence: Lei Chen,
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7
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Structural insights into the mechanism of pancreatic K ATP channel regulation by nucleotides. Nat Commun 2022; 13:2770. [PMID: 35589716 PMCID: PMC9120461 DOI: 10.1038/s41467-022-30430-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 04/28/2022] [Indexed: 11/17/2022] Open
Abstract
ATP-sensitive potassium channels (KATP) are metabolic sensors that convert the intracellular ATP/ADP ratio to the excitability of cells. They are involved in many physiological processes and implicated in several human diseases. Here we present the cryo-EM structures of the pancreatic KATP channel in both the closed state and the pre-open state, resolved in the same sample. We observe the binding of nucleotides at the inhibitory sites of the Kir6.2 channel in the closed but not in the pre-open state. Structural comparisons reveal the mechanism for ATP inhibition and Mg-ADP activation, two fundamental properties of KATP channels. Moreover, the structures also uncover the activation mechanism of diazoxide-type KATP openers. KATP channels are energy sensors. Here, authors report the Cryo-EM structures of pancreatic KATP in both the closed state and the pre-open state. These structures illuminate the mechanism of KATP channel regulation by the intracellular nucleotides.
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8
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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.
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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.
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9
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Walczewska-Szewc K, Nowak W. Photo-Switchable Sulfonylureas Binding to ATP-Sensitive Potassium Channel Reveal the Mechanism of Light-Controlled Insulin Release. J Phys Chem B 2021; 125:13111-13121. [PMID: 34825567 PMCID: PMC8667036 DOI: 10.1021/acs.jpcb.1c07292] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 11/13/2021] [Indexed: 11/29/2022]
Abstract
ATP-sensitive potassium (KATP) channels are present in numerous organs, including the heart, brain, and pancreas. Physiological opening and closing of KATPs present in pancreatic β-cells, in response to changes in the ATP/ADP concentration ratio, are correlated with insulin release into the bloodstream. Sulfonylurea drugs, commonly used in type 2 diabetes mellitus treatment, bind to the octamer KATP channels composed of four pore-forming Kir6.2 and four SUR1 subunits and increase the probability of insulin release. Azobenzene-based derivatives of sulfonylureas, such as JB253 inspired by well-established antidiabetic drug glimepiride, allow for control of this process by light. The mechanism of that phenomenon was not known until now. In this paper, we use molecular docking, molecular dynamics, and metadynamics to reveal structural determinants explaining light-controlled insulin release. We show that both trans- and cis-JB253 bind to the same SUR1 cavity as antidiabetic sulfonylurea glibenclamide (GBM). Simulations indicate that, in contrast to trans-JB253, the cis-JB253 structure generated by blue light absorption promotes open structures of SUR1, in close similarity to the GBM effect. We postulate that in the open SUR1 structures, the N-terminal tail from Kir6.2 protruding into the SUR1 pocket is stabilized by flexible enough sulfonylureas. Therefore, the adjacent Kir6.2 pore is more often closed, which in turn facilitates insulin release. Thus, KATP conductance is regulated by peptide linkers between its Kir6.2 and SUR1 subunits, a phenomenon present in other biological signaling pathways. Our data explain the observed light-modulated activity of photoactive sulfonylureas and widen a way to develop new antidiabetic drugs having reduced adverse effects.
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Affiliation(s)
- Katarzyna Walczewska-Szewc
- Faculty of Physics, Astronomy
and Informatics, Nicolaus Copernicus University
in Torun, ul. Grudziadzka 5, 87-100 Torun, Poland
| | - Wieslaw Nowak
- Faculty of Physics, Astronomy
and Informatics, Nicolaus Copernicus University
in Torun, ul. Grudziadzka 5, 87-100 Torun, Poland
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10
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Rendell MS. Current and emerging gluconeogenesis inhibitors for the treatment of Type 2 diabetes. Expert Opin Pharmacother 2021; 22:2167-2179. [PMID: 34348528 DOI: 10.1080/14656566.2021.1958779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
INTRODUCTION In the last several decades, fueled by gene knockout and knockdown techniques, there has been substantial progress in detailing the pathways of gluconeogenesis. A host of molecules have been identified as potential targets for therapeutic intervention. A number of hormones, enzymes and transcription factors participate in gluconeogenesis. Many new agents have come into use to treat diabetes and several of these are in development to suppress gluconeogenesis. AREAS COVERED Herein, the author reviews agents that have been discovered and/or are in development, which control excess gluconeogenesis. The author has used multiple sources including PubMed, the preprint servers MedRxIv, BioRxIv, Research Gate, as well as Google Search and the database of the U.S. Patent and Trademarks Office to find appropriate literature. EXPERT OPINION It is now clear that lipid metabolism and hepatic lipogenesis play a major role in gluconeogenesis and resistance to insulin. Future efforts will focus on the duality of gluconeogenesis and adipose tissue metabolism. The exploration of therapeutic RNA agents will accelerate. The balance of clinical benefit and adverse effects will determine the future of new gluconeogenesis inhibitors.
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Affiliation(s)
- Marc S Rendell
- The Association of Diabetes Investigators, Newport Coast, California, United States.,The Rose Salter Medical Research Foundation, Newport Coast, California, United States
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11
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Bickers SC, Benlekbir S, Rubinstein JL, Kanelis V. Structure of Ycf1p reveals the transmembrane domain TMD0 and the regulatory region of ABCC transporters. Proc Natl Acad Sci U S A 2021; 118:e2025853118. [PMID: 34021087 PMCID: PMC8166025 DOI: 10.1073/pnas.2025853118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
ATP binding cassette (ABC) proteins typically function in active transport of solutes across membranes. The ABC core structure is composed of two transmembrane domains (TMD1 and TMD2) and two cytosolic nucleotide binding domains (NBD1 and NBD2). Some members of the C-subfamily of ABC (ABCC) proteins, including human multidrug resistance proteins (MRPs), also possess an N-terminal transmembrane domain (TMD0) that contains five transmembrane α-helices and is connected to the ABC core by the L0 linker. While TMD0 was resolved in SUR1, the atypical ABCC protein that is part of the hetero-octameric ATP-sensitive K+ channel, little is known about the structure of TMD0 in monomeric ABC transporters. Here, we present the structure of yeast cadmium factor 1 protein (Ycf1p), a homolog of human MRP1, determined by electron cryo-microscopy (cryo-EM). A comparison of Ycf1p, SUR1, and a structure of MRP1 that showed TMD0 at low resolution demonstrates that TMD0 can adopt different orientations relative to the ABC core, including a ∼145° rotation between Ycf1p and SUR1. The cryo-EM map also reveals that segments of the regulatory (R) region, which links NBD1 to TMD2 and was poorly resolved in earlier ABCC structures, interacts with the L0 linker, NBD1, and TMD2. These interactions, combined with fluorescence quenching experiments of isolated NBD1 with and without the R region, suggest how posttranslational modifications of the R region modulate ABC protein activity. Mapping known mutations from MRP2 and MRP6 onto the Ycf1p structure explains how mutations involving TMD0 and the R region of these proteins lead to disease.
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Affiliation(s)
- Sarah C Bickers
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
- Department of Chemical and Physical Sciences, University of Toronto, Mississauga, ON L5L 1C6, Canada
| | - Samir Benlekbir
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - John L Rubinstein
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada;
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Voula Kanelis
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada;
- Department of Chemical and Physical Sciences, University of Toronto, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
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12
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Walczewska-Szewc K, Nowak W. Structural Determinants of Insulin Release: Disordered N-Terminal Tail of Kir6.2 Affects Potassium Channel Dynamics through Interactions with Sulfonylurea Binding Region in a SUR1 Partner. J Phys Chem B 2020; 124:6198-6211. [PMID: 32598150 PMCID: PMC7467719 DOI: 10.1021/acs.jpcb.0c02720] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
![]()
Inward rectifying
potassium ion channels (KATP), sensitive to the
ATP/ADP concentration ratio, play an important, control role in pancreatic
β cells. The channels close upon the increase of this ratio,
which, in turn, triggers insulin release to blood. Numerous mutations
in KATP lead to severe and widespread medical conditions such as diabetes.
The KATP system consists of a pore made of four Kir6.2 subunits and
four accompanying large SUR1 proteins belonging to the ABCC transporters
group. How SUR1 affects KATP function is not yet known; therefore,
we created simplified models of the Kir6.2 tetramer based on recently
determined cryo-EM KATP structures. Using all-atom molecular dynamics
(MD) with the CHARMM36 force field, targeted MD, and molecular docking,
we revealed functionally important rearrangements in the Kir6.2 pore,
induced by the presence of the SUR1 protein. The cytoplasmic domain
of Kir6.2 (CTD) is brought closer to the membrane due to interactions
with SUR1. Each Kir6.2 subunit has a conserved, functionally important,
disordered N-terminal tail. Using molecular docking, we found that
the Kir6.2 tail easily docks to the sulfonylurea drug binding region
located in the adjacent SUR1 protein. We reveal, for the first time,
dynamical behavior of the Kir6.2/SUR1 system, confirming a physiological
role of the Kir6.2 disordered tail, and we indicate structural determinants
of KATP-dependent insulin release from pancreatic β cells.
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Affiliation(s)
- Katarzyna Walczewska-Szewc
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.,Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń, Poland
| | - Wiesław Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland
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13
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Sanchez‐Andres JV, Pomares R, Malaisse WJ. Adaptive short-term associative conditioning in the pancreatic β-cell. Physiol Rep 2020; 8:e14403. [PMID: 32232927 PMCID: PMC7105902 DOI: 10.14814/phy2.14403] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 02/19/2020] [Accepted: 02/20/2020] [Indexed: 01/21/2023] Open
Abstract
This study associates cholinergic stimulation of the pancreatic β-cell electrical activity with a short-term memory phenomenon. Glucose pulses applied to a basal glucose concentration induce depolarizing waves which are used to estimate the evolution of the β-cell glucose sensitivity. Exposure to carbamoylcholine (carbachol) increases the size of the glucose-induced depolarizing waves. This change appears after carbachol withdrawal and implies a temporal potentiation of sensitivity (TPS) lasting up to one hour. TPS induction requires the simultaneous action of carbachol and glucose. The substitution of glucose with the secretagogues glyceraldehyde or 2-ketoisocaproate mimics glucose-induced TPS, while palmitate does not. TPS is not produced if the membrane is kept hyperpolarized by diazoxide. Glucose can be replaced by tolbutamide, suggesting a role of depolarization and a subsequent increase in intracellular calcium concentration. A role for kinases is suggested because staurosporine prevents TPS induction. Cycloheximide does not impair TPS induction, indicating that de novo protein synthesis is not required. The fact that the two inputs acting simultaneously produce an effect that lasts up to one hour without requiring de novo protein synthesis suggests that TPS constitutes a case of short-term associative conditioning in non-neural tissue. The convergence of basal glucose levels and muscarinic activation happens physiologically during the cephalic phase of digestion, in order to later absorb incoming fuels. Our data reveals that the role of the cephalic phase may be extended, increasing nutrient sensitivity during meals while remaining low between them.
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Affiliation(s)
| | - Raquel Pomares
- Department of PhysiologyUniversidad Miguel HernandezAlicanteSpain
| | - Willy J. Malaisse
- Department of BiochemistryUniversité Libre de BruxellesBrusselsBelgium
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