1
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Li HZ, Pike ACW, Lotsaris I, Chi G, Hansen JS, Lee SC, Rödström KEJ, Bushell SR, Speedman D, Evans A, Wang D, He D, Shrestha L, Nasrallah C, Burgess-Brown NA, Vandenberg RJ, Dafforn TR, Carpenter EP, Sauer DB. Structure and function of the SIT1 proline transporter in complex with the COVID-19 receptor ACE2. Nat Commun 2024; 15:5503. [PMID: 38951531 PMCID: PMC11217458 DOI: 10.1038/s41467-024-48921-x] [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: 05/24/2023] [Accepted: 05/16/2024] [Indexed: 07/03/2024] Open
Abstract
Proline is widely known as the only proteogenic amino acid with a secondary amine. In addition to its crucial role in protein structure, the secondary amino acid modulates neurotransmission and regulates the kinetics of signaling proteins. To understand the structural basis of proline import, we solved the structure of the proline transporter SIT1 in complex with the COVID-19 viral receptor ACE2 by cryo-electron microscopy. The structure of pipecolate-bound SIT1 reveals the specific sequence requirements for proline transport in the SLC6 family and how this protein excludes amino acids with extended side chains. By comparing apo and substrate-bound SIT1 states, we also identify the structural changes that link substrate release and opening of the cytoplasmic gate and provide an explanation for how a missense mutation in the transporter causes iminoglycinuria.
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Affiliation(s)
- Huanyu Z Li
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Ashley C W Pike
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Irina Lotsaris
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Gamma Chi
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Jesper S Hansen
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Sarah C Lee
- School of Biosciences, University of Birmingham, Birmingham, UK
| | - Karin E J Rödström
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Simon R Bushell
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - David Speedman
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Adam Evans
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Dong Wang
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Didi He
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Leela Shrestha
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Chady Nasrallah
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Nicola A Burgess-Brown
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Robert J Vandenberg
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia.
| | | | - Elisabeth P Carpenter
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - David B Sauer
- Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
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2
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Lu X, Huang J. Molecular mechanisms of Na +-driven bile acid transport in human NTCP. Biophys J 2024; 123:1195-1210. [PMID: 38544409 PMCID: PMC11140467 DOI: 10.1016/j.bpj.2024.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 02/17/2024] [Accepted: 03/25/2024] [Indexed: 04/12/2024] Open
Abstract
Human Na+ taurocholate co-transporting protein (hNTCP) is a key bile salt transporter to maintain enterohepatic circulation and is responsible for the recognition of hepatitis B and D viruses. Despite landmark cryoelectron microscopy studies revealing open-pore and inward-facing states of hNTCP stabilized by antibodies, the transport mechanism remains largely unknown. To address this knowledge gap, we used molecular dynamics and enhanced sampling metadynamics simulations to elucidate the intrinsic mechanism of hNTCP-mediated taurocholate acid (TCA) transport driven by Na+ binding. We uncovered three TCA-binding modes, including one that closely matched the limited cryoelectron microscopy density observed in the open-pore hNTCP. We also captured several key hNTCP conformations in the substrate transport cycle, particularly including an outward-facing, substrate-bound state. Furthermore, we provided thermodynamic evidence supporting that changes in the Na+-binding state drive the TCA transport by exploiting the amphiphilic nature of the substrate and modulating the protein environment, thereby enabling the TCA molecule to flip through. Understanding these mechanistic details of Na+-driven bile acid transport may aid in the development of hNTCP-targeted therapies for liver diseases.
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Affiliation(s)
- Xiaoli Lu
- Westlake AI Therapeutics Laboratory, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
| | - Jing Huang
- Westlake AI Therapeutics Laboratory, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China.
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3
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Watabe E, Kawanabe A, Kamitori K, Ichihara S, Fujiwara Y. Sugar binding of sodium-glucose cotransporters analyzed by voltage-clamp fluorometry. J Biol Chem 2024; 300:107215. [PMID: 38522518 PMCID: PMC11061222 DOI: 10.1016/j.jbc.2024.107215] [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: 09/11/2023] [Revised: 02/19/2024] [Accepted: 03/18/2024] [Indexed: 03/26/2024] Open
Abstract
Sugar absorption is crucial for life and relies on glucose transporters, including sodium-glucose cotransporters (SGLTs). Although the structure of SGLTs has been resolved, the substrate selectivity of SGLTs across diverse isoforms has not been determined owing to the complex substrate-recognition processes and limited analysis methods. Therefore, this study used voltage-clamp fluorometry (VCF) to explore the substrate-binding affinities of human SGLT1 in Xenopus oocytes. VCF analysis revealed high-affinity binding of D-glucose and D-galactose, which are known transported substrates. D-fructose, which is not a transported substrate, also bound to SGLT1, suggesting potential recognition despite the lack of transport activity. VCF analysis using the T287N mutant of the substrate-binding pocket, which has reduced D-glucose transport capacity, showed that its D-galactose-binding affinity exceeded its D-glucose-binding affinity. This suggests that the change in the VCF signal was due to substrate binding to the binding pocket. Both D-fructose and L-sorbose showed similar binding affinities, indicating that SGLT1 preferentially binds to pyranose-form sugars, including D-fructopyranose. Electrophysiological analysis confirmed that D-fructose binding did not affect the SGLT1 transport function. The significance of the VCF assay lies in its ability to measure sugar-protein interactions in living cells, thereby bridging the gap between structural analyses and functional characterizations of sugar transporters. Our findings also provide insights into SGLT substrate selectivity and the potential for developing medicines with reduced side effects by targeting non-glucose sugars with low bioreactivity.
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Affiliation(s)
- Erika Watabe
- Laboratory of Molecular Physiology & Biophysics, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan
| | - Akira Kawanabe
- Laboratory of Molecular Physiology & Biophysics, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan
| | - Kazuyo Kamitori
- Laboratory of Molecular Physiology & Biophysics, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan; International Institute of Rare Sugar Research and Education, Kagawa University, Miki-cho, Kagawa, Japan
| | - Satoko Ichihara
- Laboratory of Molecular Physiology & Biophysics, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan
| | - Yuichiro Fujiwara
- Laboratory of Molecular Physiology & Biophysics, Faculty of Medicine, Kagawa University, Miki-cho, Kagawa, Japan; International Institute of Rare Sugar Research and Education, Kagawa University, Miki-cho, Kagawa, Japan; Laboratory of Physiology and Biophysics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima City, Hiroshima, Japan.
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4
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Marinelli F, Faraldo-Gómez JD. Conformational free-energy landscapes of a Na +/Ca 2+ exchanger explain its alternating-access mechanism and functional specificity. Proc Natl Acad Sci U S A 2024; 121:e2318009121. [PMID: 38588414 PMCID: PMC11032461 DOI: 10.1073/pnas.2318009121] [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: 10/25/2023] [Accepted: 02/20/2024] [Indexed: 04/10/2024] Open
Abstract
Secondary-active transporters catalyze the movement of myriad substances across all cellular membranes, typically against opposing concentration gradients, and without consuming any ATP. To do so, these proteins employ an intriguing structural mechanism evolved to be activated only upon recognition or release of the transported species. We examine this self-regulated mechanism using a homolog of the cardiac Na+/Ca2+ exchanger as a model system. Using advanced computer simulations, we map out the complete functional cycle of this transporter, including unknown conformations that we validate against existing experimental data. Calculated free-energy landscapes reveal why this transporter functions as an antiporter rather than a symporter, why it specifically exchanges Na+ and Ca2+, and why the stoichiometry of this exchange is exactly 3:1. We also rationalize why the protein does not exchange H+ for either Ca2+ or Na+, despite being able to bind H+ and its high similarity with H+/Ca2+ exchangers. Interestingly, the nature of this transporter is not explained by its primary structural states, known as inward- and outward-open conformations; instead, the defining factor is the feasibility of conformational intermediates between those states, wherein access pathways leading to the substrate binding sites become simultaneously occluded from both sides of the membrane. This analysis offers a physically coherent, broadly transferable route to understand the emergence of function from structure among secondary-active membrane transporters.
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Affiliation(s)
- Fabrizio Marinelli
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, NIH, Bethesda, MD20814
| | - José D. Faraldo-Gómez
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, NIH, Bethesda, MD20814
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5
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Ma D, Hu M, Yang X, Liu Q, Ye F, Cai W, Wang Y, Xu X, Chang S, Wang R, Yang W, Ye S, Su N, Fan M, Xu H, Guo J. Structural basis for sugar perception by Drosophila gustatory receptors. Science 2024; 383:eadj2609. [PMID: 38305684 DOI: 10.1126/science.adj2609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 01/17/2024] [Indexed: 02/03/2024]
Abstract
Insects rely on a family of seven transmembrane proteins called gustatory receptors (GRs) to encode different taste modalities, such as sweet and bitter. We report structures of Drosophila sweet taste receptors GR43a and GR64a in the apo and sugar-bound states. Both GRs form tetrameric sugar-gated cation channels composed of one central pore domain (PD) and four peripheral ligand-binding domains (LBDs). Whereas GR43a is specifically activated by the monosaccharide fructose that binds to a narrow pocket in LBDs, disaccharides sucrose and maltose selectively activate GR64a by binding to a larger and flatter pocket in LBDs. Sugar binding to LBDs induces local conformational changes, which are subsequently transferred to the PD to cause channel opening. Our studies reveal a structural basis for sugar recognition and activation of GRs.
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Affiliation(s)
- Demin Ma
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
- Nanhu Brain-Computer Interface Institute, Hangzhou 311100, China
| | - Meiqin Hu
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310058, China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou 311121, China
| | - Xiaotong Yang
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310058, China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou 311121, China
| | - Qiang Liu
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310058, China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou 311121, China
| | - Fan Ye
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
- Nanhu Brain-Computer Interface Institute, Hangzhou 311100, China
| | - Weijie Cai
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310058, China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou 311121, China
| | - Yong Wang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Ximing Xu
- Marine Biomedical Institute of Qingdao, School of Pharmacy and Medicine, Ocean University of China, Qingdao, Shandong 266100, China
| | - Shenghai Chang
- Center of Cryo-Electron Microscopy, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Ruiying Wang
- CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Wei Yang
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Sheng Ye
- Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, Tianjin 300072, China
| | - Nannan Su
- International Institutes of Medicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang 322000, China
| | - Minrui Fan
- CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Haoxing Xu
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou 310058, China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou 311121, China
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jiangtao Guo
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
- Nanhu Brain-Computer Interface Institute, Hangzhou 311100, China
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
- State Key Laboratory of Plant Environmental Resilience, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
- Department of Cardiology, Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310016, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang 310058, China
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6
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Currie MJ, Davies JS, Scalise M, Gulati A, Wright JD, Newton-Vesty MC, Abeysekera GS, Subramanian R, Wahlgren WY, Friemann R, Allison JR, Mace PD, Griffin MDW, Demeler B, Wakatsuki S, Drew D, Indiveri C, Dobson RCJ, North RA. Structural and biophysical analysis of a Haemophilus influenzae tripartite ATP-independent periplasmic (TRAP) transporter. eLife 2024; 12:RP92307. [PMID: 38349818 PMCID: PMC10942642 DOI: 10.7554/elife.92307] [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] [Indexed: 02/15/2024] Open
Abstract
Tripartite ATP-independent periplasmic (TRAP) transporters are secondary-active transporters that receive their substrates via a soluble-binding protein to move bioorganic acids across bacterial or archaeal cell membranes. Recent cryo-electron microscopy (cryo-EM) structures of TRAP transporters provide a broad framework to understand how they work, but the mechanistic details of transport are not yet defined. Here we report the cryo-EM structure of the Haemophilus influenzae N-acetylneuraminate TRAP transporter (HiSiaQM) at 2.99 Å resolution (extending to 2.2 Å at the core), revealing new features. The improved resolution (the previous HiSiaQM structure is 4.7 Å resolution) permits accurate assignment of two Na+ sites and the architecture of the substrate-binding site, consistent with mutagenic and functional data. Moreover, rather than a monomer, the HiSiaQM structure is a homodimer. We observe lipids at the dimer interface, as well as a lipid trapped within the fusion that links the SiaQ and SiaM subunits. We show that the affinity (KD) for the complex between the soluble HiSiaP protein and HiSiaQM is in the micromolar range and that a related SiaP can bind HiSiaQM. This work provides key data that enhances our understanding of the 'elevator-with-an-operator' mechanism of TRAP transporters.
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Affiliation(s)
- Michael J Currie
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
| | - James S Davies
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
- Department of Biochemistry and Biophysics, Stockholm UniversityStockholmSweden
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of CalabriaArcavacata di RendeItaly
| | - Ashutosh Gulati
- Department of Biochemistry and Biophysics, Stockholm UniversityStockholmSweden
| | - Joshua D Wright
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
| | - Michael C Newton-Vesty
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
| | - Gayan S Abeysekera
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
| | - Ramaswamy Subramanian
- Biological Sciences and Biomedical Engineering, Bindley Bioscience Center, Purdue University West LafayetteWest LafayetteUnited States
| | - Weixiao Y Wahlgren
- Department of Chemistry and Molecular Biology, Biochemistry and Structural Biology, University of GothenburgGothenburgSweden
| | - Rosmarie Friemann
- Centre for Antibiotic Resistance Research (CARe) at University of GothenburgGothenburgSweden
| | - Jane R Allison
- Biomolecular Interaction Centre, Digital Life Institute, Maurice Wilkins Centre for Molecular Biodiscovery, and School of Biological Sciences, University of AucklandAucklandNew Zealand
| | - Peter D Mace
- Biochemistry Department, School of Biomedical Sciences, University of OtagoDunedinNew Zealand
| | - Michael DW Griffin
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio Molecular Science and Biotechnology Institute, Department of Biochemistry and Pharmacology, University of MelbourneMelbourneAustralia
| | - Borries Demeler
- Department of Chemistry and Biochemistry, University of MontanaMissoulaUnited States
- Department of Chemistry and Biochemistry, University of LethbridgeLethbridgeCanada
| | - Soichi Wakatsuki
- Biological Sciences Division, SLAC National Accelerator LaboratoryMenlo ParkUnited States
- Department of Structural Biology, Stanford University School of MedicineStanfordUnited States
| | - David Drew
- Department of Biochemistry and Biophysics, Stockholm UniversityStockholmSweden
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of CalabriaArcavacata di RendeItaly
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM)BariItaly
| | - Renwick CJ Dobson
- Biomolecular Interaction Centre, Maurice Wilkins Centre for Biodiscovery, MacDiarmid Institute for Advanced Materials and Nanotechnology, and School of Biological Sciences, University of CanterburyChristchurchNew Zealand
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio Molecular Science and Biotechnology Institute, Department of Biochemistry and Pharmacology, University of MelbourneMelbourneAustralia
| | - Rachel A North
- Department of Biochemistry and Biophysics, Stockholm UniversityStockholmSweden
- School of Medical Sciences, Faculty of Medicine and Health, University of SydneySydneyAustralia
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7
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Hiraizumi M, Akashi T, Murasaki K, Kishida H, Kumanomidou T, Torimoto N, Nureki O, Miyaguchi I. Transport and inhibition mechanism of the human SGLT2-MAP17 glucose transporter. Nat Struct Mol Biol 2024; 31:159-169. [PMID: 38057552 PMCID: PMC10803289 DOI: 10.1038/s41594-023-01134-0] [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: 01/10/2023] [Accepted: 09/22/2023] [Indexed: 12/08/2023]
Abstract
Sodium-glucose cotransporter 2 (SGLT2) is imporant in glucose reabsorption. SGLT2 inhibitors suppress renal glucose reabsorption, therefore reducing blood glucose levels in patients with type 2 diabetes. We and others have developed several SGLT2 inhibitors starting from phlorizin, a natural product. Using cryo-electron microscopy, we present the structures of human (h)SGLT2-MAP17 complexed with five natural or synthetic inhibitors. The four synthetic inhibitors (including canagliflozin) bind the transporter in the outward conformations, while phlorizin binds it in the inward conformation. The phlorizin-hSGLT2 interaction exhibits biphasic kinetics, suggesting that phlorizin alternately binds to the extracellular and intracellular sides. The Na+-bound outward-facing and unbound inward-open structures of hSGLT2-MAP17 suggest that the MAP17-associated bundle domain functions as a scaffold, with the hash domain rotating around the Na+-binding site. Thus, Na+ binding stabilizes the outward-facing conformation, and its release promotes state transition to inward-open conformation, exhibiting a role of Na+ in symport mechanism. These results provide structural evidence for the Na+-coupled alternating-access mechanism proposed for the transporter family.
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Affiliation(s)
- Masahiro Hiraizumi
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan.
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan.
| | - Tomoya Akashi
- DMPK Research Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan
| | - Kouta Murasaki
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan
| | - Hiroyuki Kishida
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan
| | - Taichi Kumanomidou
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan
| | - Nao Torimoto
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
| | - Ikuko Miyaguchi
- Discovery Technology Laboratories Sohyaku Innovative Research Division, Mitsubishi Tanabe Pharma, Yokohama, Japan.
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8
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Khan F, Elgeti M, Grandfield S, Paz A, Naughton FB, Marcoline FV, Althoff T, Ermolova N, Wright EM, Hubbell WL, Grabe M, Abramson J. Membrane potential accelerates sugar uptake by stabilizing the outward facing conformation of the Na/glucose symporter vSGLT. Nat Commun 2023; 14:7511. [PMID: 37980423 PMCID: PMC10657379 DOI: 10.1038/s41467-023-43119-z] [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: 09/08/2022] [Accepted: 10/30/2023] [Indexed: 11/20/2023] Open
Abstract
Sodium-dependent glucose transporters (SGLTs) couple a downhill Na+ ion gradient to actively transport sugars. Here, we investigate the impact of the membrane potential on vSGLT structure and function using sugar uptake assays, double electron-electron resonance (DEER), electrostatic calculations, and kinetic modeling. Negative membrane potentials, as present in all cell types, shift the conformational equilibrium of vSGLT towards an outward-facing conformation, leading to increased sugar transport rates. Electrostatic calculations identify gating charge residues responsible for this conformational shift that when mutated reduce galactose transport and eliminate the response of vSGLT to potential. Based on these findings, we propose a comprehensive framework for sugar transport via vSGLT, where the cellular membrane potential facilitates resetting of the transporter after cargo release. This framework holds significance not only for SGLTs but also for other transporters and channels.
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Affiliation(s)
- Farha Khan
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, 49503, USA
| | - Matthias Elgeti
- Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany.
| | - Samuel Grandfield
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Renaissance School of Medicine at Stony Brook University, Stony Brook, NY, 11794, USA
| | - Aviv Paz
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Hauptman-Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY, 14203, USA
| | - Fiona B Naughton
- Department of Pharmaceutical Chemistry, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, 94158, USA
| | - Frank V Marcoline
- Department of Pharmaceutical Chemistry, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, 94158, USA
| | - Thorsten Althoff
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Natalia Ermolova
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Ernest M Wright
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Wayne L Hubbell
- Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Michael Grabe
- Department of Pharmaceutical Chemistry, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, 94158, USA.
| | - Jeff Abramson
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
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9
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Zantza I, Pyrris Y, Raniolo S, Papadaki GF, Lambrinidis G, Limongelli V, Diallinas G, Mikros E. Uracil/H + Symport by FurE Refines Aspects of the Rocking-bundle Mechanism of APC-type Transporters. J Mol Biol 2023; 435:168226. [PMID: 37544358 DOI: 10.1016/j.jmb.2023.168226] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 07/22/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023]
Abstract
Transporters mediate the uptake of solutes, metabolites and drugs across the cell membrane. The eukaryotic FurE nucleobase/H+ symporter of Aspergillus nidulans has been used as a model protein to address structure-function relationships in the APC transporter superfamily, members of which are characterized by the LeuT-fold and seem to operate by the so-called 'rocking-bundle' mechanism. In this study, we reveal the binding mode, translocation and release pathway of uracil/H+ by FurE using path collective variable, funnel metadynamics and rational mutational analysis. Our study reveals a stepwise, induced-fit, mechanism of ordered sequential transport of proton and uracil, which in turn suggests that FurE, functions as a multi-step gated pore, rather than employing 'rocking' of compact domains, as often proposed for APC transporters. Finally, our work supports that specific residues of the cytoplasmic N-tail are involved in substrate translocation, in line with their essentiality for FurE function.
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Affiliation(s)
- Iliana Zantza
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Yiannis Pyrris
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece.
| | - Stefano Raniolo
- Faculty of Biomedical Sciences, Euler Institute, Università della Svizzera italiana (USI), Lugano 6900, Switzerland.
| | - Georgia F Papadaki
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece
| | - George Lambrinidis
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Vittorio Limongelli
- Faculty of Biomedical Sciences, Euler Institute, Università della Svizzera italiana (USI), Lugano 6900, Switzerland; Department of Pharmacy, University of Naples "Federico II", Naples 80131, Italy.
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion 70013, Greece.
| | - Emmanuel Mikros
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece; Athena Research and Innovation Center in Information Communication & Knowledge Technologies, Marousi 15125, Greece.
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10
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Jiang R, Wu L, Zeng J, Shah K, Zhang R, Hu G, Qin Y, Zhang Z. Identification of HuSWEET Family in Pitaya ( Hylocereus undatus) and Key Roles of HuSWEET12a and HuSWEET13d in Sugar Accumulation. Int J Mol Sci 2023; 24:12882. [PMID: 37629062 PMCID: PMC10454816 DOI: 10.3390/ijms241612882] [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: 06/28/2023] [Revised: 07/22/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023] Open
Abstract
The sugar composition and content of fruit have a significant impact on their flavor and taste. In pitaya, or dragon fruit, sweetness is a crucial determinant of fruit taste and consumer preference. The sugars will eventually be exported transporters (SWEETs), a novel group of sugar transporters that have various physiological functions, including phloem loading, seed filling, nectar secretion, and fruit development. However, the role of SWEETs in sugar accumulation in pitaya fruit is not yet clear. Here, we identified 19 potential members (HuSWEET genes) of the SWEET family in pitaya and analyzed their conserved motifs, physiochemical characteristics, chromosomal distribution, gene structure, and phylogenetic relationship. Seven highly conserved α-helical transmembrane domains (7-TMs) were found, and the HuSWEET proteins can be divided into three clades based on the phylogenetic analysis. Interestingly, we found two HuSWEET genes, HuSWEET12a and HuSWEET13d, that showed strong preferential expressions in fruits and an upward trend during fruit maturation, suggesting they have key roles in sugar accumulation in pitaya. This can be further roughly demonstrated by the fact that transgenic tomato plants overexpressing HuSWEET12a/13d accumulated high levels of sugar in the mature fruit. Together, our result provides new insights into the regulation of sugar accumulation by SWEET family genes in pitaya fruit, which also set a crucial basis for the further functional study of the HuSWEETs.
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Affiliation(s)
| | | | | | | | | | | | - Yonghua Qin
- Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (South China), Ministry of Agriculture and Rural Affairs, College of Horticulture, South China Agricultural University, Guangzhou 510642, China; (R.J.); (L.W.); (J.Z.); (K.S.); (R.Z.); (G.H.)
| | - Zhike Zhang
- Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (South China), Ministry of Agriculture and Rural Affairs, College of Horticulture, South China Agricultural University, Guangzhou 510642, China; (R.J.); (L.W.); (J.Z.); (K.S.); (R.Z.); (G.H.)
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11
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Davey LE, Malkus PN, Villa M, Dolat L, Holmes ZC, Letourneau J, Ansaldo E, David LA, Barton GM, Valdivia RH. A genetic system for Akkermansia muciniphila reveals a role for mucin foraging in gut colonization and host sterol biosynthesis gene expression. Nat Microbiol 2023; 8:1450-1467. [PMID: 37337046 DOI: 10.1038/s41564-023-01407-w] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/10/2023] [Indexed: 06/21/2023]
Abstract
Akkermansia muciniphila, a mucophilic member of the gut microbiota, protects its host against metabolic disorders. Because it is genetically intractable, the mechanisms underlying mucin metabolism, gut colonization and its impact on host physiology are not well understood. Here we developed and applied transposon mutagenesis to identify genes important for intestinal colonization and for the use of mucin. An analysis of transposon mutants indicated that de novo biosynthesis of amino acids was required for A. muciniphila growth on mucin medium and that many glycoside hydrolases are redundant. We observed that mucin degradation products accumulate in internal compartments within bacteria in a process that requires genes encoding pili and a periplasmic protein complex, which we term mucin utilization locus (MUL) genes. We determined that MUL genes were required for intestinal colonization in mice but only when competing with other microbes. In germ-free mice, MUL genes were required for A. muciniphila to repress genes important for cholesterol biosynthesis in the colon. Our genetic system for A. muciniphila provides an important tool with which to uncover molecular links between the metabolism of mucins, regulation of lipid homeostasis and potential probiotic activities.
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Affiliation(s)
- Lauren E Davey
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA.
- Duke Microbiome Center, Duke University, Durham, NC, USA.
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
| | - Per N Malkus
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Max Villa
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Lee Dolat
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Zachary C Holmes
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Jeff Letourneau
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Eduard Ansaldo
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Lawrence A David
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
- Duke Microbiome Center, Duke University, Durham, NC, USA
| | - Gregory M Barton
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Raphael H Valdivia
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA.
- Duke Microbiome Center, Duke University, Durham, NC, USA.
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12
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Sever M, Merzel F. Collective Domain Motion Facilitates Water Transport in SGLT1. Int J Mol Sci 2023; 24:10528. [PMID: 37445706 DOI: 10.3390/ijms241310528] [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: 05/05/2023] [Revised: 06/17/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
The human sodium-glucose cotransporter protein (SGLT1) is an important representative of the sodium solute symporters belonging to the secondary active transporters that are critical to the homeostasis of sugar, sodium, and water in the cell. The underlying transport mechanism of SGLT1 is based on switching between inward- and outward-facing conformations, known as the alternating access model, which is crucial for substrate transport, and has also been postulated for water permeation. However, the nature of water transport remains unclear and is disputed along the passive and active transport, with the latter postulating the presence of the pumping effect. To better examine the water transport in SGLT1, we performed a series of equilibrium all-atom molecular dynamics simulations, totaling over 6 μs of sample representative conformational states of SGLT1 and its complexes, with the natural substrates, ions, and inhibitors. In addition to elucidating the basic physical factors influencing water permeation, such as channel openings and energetics, we focus on dynamic flexibility and its relationship with domain motion. Our results clearly demonstrate a dependence of instantaneous water flux on the channel opening and local water diffusion in the channel, strongly supporting the existence of a passive water transport in SGLT1. In addition, a strong correlation found between the local water diffusion and protein domain motion, resembling the "rocking-bundle" motion, reveals its facilitating role in the water transport.
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Affiliation(s)
- Marko Sever
- Theory Departnemt, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia
| | - Franci Merzel
- Theory Departnemt, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
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13
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Trebesch N, Tajkhorshid E. Structure Reveals Homology in Elevator Transporters. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.14.544989. [PMID: 37398459 PMCID: PMC10312693 DOI: 10.1101/2023.06.14.544989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The elevator transport mechanism is one of the handful of canonical mechanisms by which transporters shuttle their substrates across the semi-permeable membranes that surround cells and organelles. Studies of molecular function are naturally guided by evolutionary context, but until now this context has been limited for elevator transporters because established evolutionary classification methods have organized them into several apparently unrelated families. Through comprehensive examination of the pertinent structures available in the Protein Data Bank, we show that 62 elevator transporters from 18 families share a conserved architecture in their transport domains consisting of 10 helices connected in 8 topologies. Through quantitative analysis of the structural similarity, structural complexity, and topologically-corrected sequence similarity among the transport domains, we provide compelling evidence that these elevator transporters are all homologous. Using our analysis, we have constructed a phylogenetic tree to enable quantification and visualization of the evolutionary relationships among elevator transporters and their families. We also report several examples of functional features that are shared by elevator transporters from different families. Our findings shed new light on the elevator transport mechanism and allow us to understand it in a far deeper and more nuanced manner.
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Affiliation(s)
- Noah Trebesch
- Theoretical and Computational Biophysics Group, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Resource for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign
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14
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Cui W, Niu Y, Sun Z, Liu R, Chen L. Structures of human SGLT in the occluded state reveal conformational changes during sugar transport. Nat Commun 2023; 14:2920. [PMID: 37217492 DOI: 10.1038/s41467-023-38720-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 05/12/2023] [Indexed: 05/24/2023] Open
Abstract
Sodium-Glucose Cotransporters (SGLT) mediate the uphill uptake of extracellular sugars and play fundamental roles in sugar metabolism. Although their structures in inward-open and outward-open conformations are emerging from structural studies, the trajectory of how SGLTs transit from the outward-facing to the inward-facing conformation remains unknown. Here, we present the cryo-EM structures of human SGLT1 and SGLT2 in the substrate-bound state. Both structures show an occluded conformation, with not only the extracellular gate but also the intracellular gate tightly sealed. The sugar substrate are caged inside a cavity surrounded by TM1, TM2, TM3, TM6, TM7, and TM10. Further structural analysis reveals the conformational changes associated with the binding and release of substrates. These structures fill a gap in our understanding of the structural mechanisms of SGLT transporters.
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Affiliation(s)
- Wenhao Cui
- 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
| | - Yange Niu
- 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
| | - Zejian Sun
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
| | - Rui Liu
- 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.
- National Biomedical Imaging Center, Peking University, 100871, Beijing, China.
- Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China.
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15
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Substrate Recognition Properties from an Intermediate Structural State of the UreA Transporter. Int J Mol Sci 2022; 23:ijms232416039. [PMID: 36555682 PMCID: PMC9783183 DOI: 10.3390/ijms232416039] [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: 11/10/2022] [Revised: 12/09/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Through a combination of comparative modeling, site-directed and classical random mutagenesis approaches, we previously identified critical residues for binding, recognition, and translocation of urea, and its inhibition by 2-thiourea and acetamide in the Aspergillus nidulans urea transporter, UreA. To deepen the structural characterization of UreA, we employed the artificial intelligence (AI) based AlphaFold2 (AF2) program. In this analysis, the resulting AF2 models lacked inward- and outward-facing cavities, suggesting a structural intermediate state of UreA. Moreover, the orientation of the W82, W84, N279, and T282 side chains showed a large variability, which in the case of W82 and W84, may operate as a gating mechanism in the ligand pathway. To test this hypothesis non-conservative and conservative substitutions of these amino acids were introduced, and binding and transport assessed for urea and its toxic analogue 2-thiourea, as well as binding of the structural analogue acetamide. As a result, residues W82, W84, N279, and T282 were implicated in substrate identification, selection, and translocation. Using molecular docking with Autodock Vina with flexible side chains, we corroborated the AF2 theoretical intermediate model, showing a remarkable correlation between docking scores and experimental affinities determined in wild-type and UreA mutants. The combination of AI-based modeling with classical docking, validated by comprehensive mutational analysis at the binding region, would suggest an unforeseen option to determine structural level details on a challenging family of proteins.
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16
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Ravera S, Nicola JP, Salazar-De Simone G, Sigworth FJ, Karakas E, Amzel LM, Bianchet MA, Carrasco N. Structural insights into the mechanism of the sodium/iodide symporter. Nature 2022; 612:795-801. [PMID: 36517601 PMCID: PMC10501339 DOI: 10.1038/s41586-022-05530-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 11/04/2022] [Indexed: 12/15/2022]
Abstract
The sodium/iodide symporter (NIS) is the essential plasma membrane protein that mediates active iodide (I-) transport into the thyroid gland, the first step in the biosynthesis of the thyroid hormones-the master regulators of intermediary metabolism. NIS couples the inward translocation of I- against its electrochemical gradient to the inward transport of Na+ down its electrochemical gradient1,2. For nearly 50 years before its molecular identification3, NIS was the molecule at the centre of the single most effective internal radiation cancer therapy: radioiodide (131I-) treatment for thyroid cancer2. Mutations in NIS cause congenital hypothyroidism, which must be treated immediately after birth to prevent stunted growth and cognitive deficiency2. Here we report three structures of rat NIS, determined by single-particle cryo-electron microscopy: one with no substrates bound; one with two Na+ and one I- bound; and one with one Na+ and the oxyanion perrhenate bound. Structural analyses, functional characterization and computational studies show the substrate-binding sites and key residues for transport activity. Our results yield insights into how NIS selects, couples and translocates anions-thereby establishing a framework for understanding NIS function-and how it transports different substrates with different stoichiometries and releases substrates from its substrate-binding cavity into the cytosol.
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Affiliation(s)
- Silvia Ravera
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Juan Pablo Nicola
- Department of Clinical Biochemistry, National University of Córdoba, Córdoba, Argentina
| | | | - Fred J Sigworth
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT, USA
| | - Erkan Karakas
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - L Mario Amzel
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mario A Bianchet
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nancy Carrasco
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
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17
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Zhao Y, Cao E. Structural Pharmacology of Cation-Chloride Cotransporters. MEMBRANES 2022; 12:1206. [PMID: 36557113 PMCID: PMC9784483 DOI: 10.3390/membranes12121206] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/20/2022] [Accepted: 11/25/2022] [Indexed: 06/17/2023]
Abstract
Loop and thiazide diuretics have been cornerstones of clinical management of hypertension and fluid overload conditions for more than five decades. The hunt for their molecular targets led to the discovery of cation-chloride cotransporters (CCCs) that catalyze electroneutral movement of Cl- together with Na+ and/or K+. CCCs consist of two 1 Na+-1 K+-2 Cl- (NKCC1-2), one 1 Na+-1 Cl- (NCC), and four 1 K+-1 Cl- (KCC1-4) transporters in human. CCCs are fundamental in trans-epithelia ion secretion and absorption, homeostasis of intracellular Cl- concentration and cell volume, and regulation of neuronal excitability. Malfunction of NKCC2 and NCC leads to abnormal salt and water retention in the kidney and, consequently, imbalance in electrolytes and blood pressure. Mutations in KCC2 and KCC3 are associated with brain disorders due to impairments in regulation of excitability and possibly cell volume of neurons. A recent surge of structures of CCCs have defined their dimeric architecture, their ion binding sites, their conformational changes associated with ion translocation, and the mechanisms of action of loop diuretics and small molecule inhibitors. These breakthroughs now set the stage to expand CCC pharmacology beyond loop and thiazide diuretics, developing the next generation of diuretics with improved potency and specificity. Beyond drugging renal-specific CCCs, brain-penetrable therapeutics are sorely needed to target CCCs in the nervous system for the treatment of neurological disorders and psychiatric conditions.
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18
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Nan J, Yuan Y, Yang X, Shan Z, Liu H, Wei F, Zhang W, Zhang Y. Cryo-EM structure of the human sodium-chloride cotransporter NCC. SCIENCE ADVANCES 2022; 8:eadd7176. [PMID: 36351028 PMCID: PMC9645730 DOI: 10.1126/sciadv.add7176] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/21/2022] [Indexed: 05/29/2023]
Abstract
The sodium-chloride cotransporter NCC mediates the coupled import of sodium and chloride across the plasma membrane, playing vital roles in kidney extracellular fluid volume and blood pressure control. Here, we present the full-length structure of human NCC, with 2.9 Å for the transmembrane domain and 3.8 Å for the carboxyl-terminal domain. NCC adopts an inward-open conformation and a domain-swap dimeric assembly. Conserved ion binding sites among the cation-chloride cotransporters and the Na2 site are observed in our structure. A unique His residue in the substrate pocket in NCC potentially interacts with Na1 and Cl1 and might also mediate the coordination of Na2 through a Ser residue. Putative observed water molecules are indicated to participate in the coordination of ions and TM coupling. Together with transport activity assays, our structure provides the first glimpse of NCC and defines ion binding sites, promoting drug development for hypertension targeting on NCC.
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Affiliation(s)
- Jing Nan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yafei Yuan
- Beijing Frontier Research Center for Biological Structure, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xuemei Yang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Ziyang Shan
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Huihui Liu
- Warshel Institute for Computational Biology, School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen 518172, Guangdong, China
| | - Feiwen Wei
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Wei Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
| | - Yanqing Zhang
- Shanghai Fifth People’s Hospital, Fudan University, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism (Ministry of Science and Technology), Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China
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19
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Neumann C, Rosenbæk LL, Flygaard RK, Habeck M, Karlsen JL, Wang Y, Lindorff‐Larsen K, Gad HH, Hartmann R, Lyons JA, Fenton RA, Nissen P. Cryo-EM structure of the human NKCC1 transporter reveals mechanisms of ion coupling and specificity. EMBO J 2022; 41:e110169. [PMID: 36239040 PMCID: PMC9713717 DOI: 10.15252/embj.2021110169] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 12/03/2022] Open
Abstract
The sodium-potassium-chloride transporter NKCC1 of the SLC12 family performs Na+ -dependent Cl- - and K+ -ion uptake across plasma membranes. NKCC1 is important for regulating cell volume, hearing, blood pressure, and regulation of hyperpolarizing GABAergic and glycinergic signaling in the central nervous system. Here, we present a 2.6 Å resolution cryo-electron microscopy structure of human NKCC1 in the substrate-loaded (Na+ , K+ , and 2 Cl- ) and occluded, inward-facing state that has also been observed for the SLC6-type transporters MhsT and LeuT. Cl- binding at the Cl1 site together with the nearby K+ ion provides a crucial bridge between the LeuT-fold scaffold and bundle domains. Cl- -ion binding at the Cl2 site seems to undertake a structural role similar to conserved glutamate of SLC6 transporters and may allow for Cl- -sensitive regulation of transport. Supported by functional studies in mammalian cells and computational simulations, we describe a putative Na+ release pathway along transmembrane helix 5 coupled to the Cl2 site. The results provide insight into the structure-function relationship of NKCC1 with broader implications for other SLC12 family members.
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Affiliation(s)
- Caroline Neumann
- Danish Research Institute of Translational Neuroscience—DANDRITENordic EMBL Partnership for Molecular MedicineAarhusDenmark,Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | | | - Rasmus Kock Flygaard
- Danish Research Institute of Translational Neuroscience—DANDRITENordic EMBL Partnership for Molecular MedicineAarhusDenmark,Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | - Michael Habeck
- Danish Research Institute of Translational Neuroscience—DANDRITENordic EMBL Partnership for Molecular MedicineAarhusDenmark,Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | | | - Yong Wang
- Linderstrøm‐Lang Centre for Protein Science, Department of BiologyUniversity of CopenhagenCopenhagenDenmark,Shanghai Institute for Advanced Study, Institute of Quantitative Biology, College of Life SciencesZhejiang UniversityHangzhouChina
| | - Kresten Lindorff‐Larsen
- Linderstrøm‐Lang Centre for Protein Science, Department of BiologyUniversity of CopenhagenCopenhagenDenmark
| | - Hans Henrik Gad
- Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | - Rune Hartmann
- Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | - Joseph Anthony Lyons
- Danish Research Institute of Translational Neuroscience—DANDRITENordic EMBL Partnership for Molecular MedicineAarhusDenmark,Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark,Interdisciplinary Nanoscience Center (iNANO)Aarhus UniversityAarhusDenmark
| | | | - Poul Nissen
- Danish Research Institute of Translational Neuroscience—DANDRITENordic EMBL Partnership for Molecular MedicineAarhusDenmark,Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
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20
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Koumarianou P, Fernández-Méndez C, Fajardo-Delgado D, Mielu LM, Santisteban P, De la Vieja A. Basolateral Sorting of the Sodium/Iodide Symporter Is Mediated by Adaptor Protein 1 Clathrin Adaptor Complexes. Thyroid 2022; 32:1259-1270. [PMID: 35833460 PMCID: PMC9618391 DOI: 10.1089/thy.2022.0163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Background: The sodium/iodide symporter (NIS) is a transmembrane protein located on the basolateral membrane of thyrocytes. Despite its physiological and clinical relevance, little is known about the mechanisms that mediate NIS subcellular sorting. In the present study, we examined NIS basolateral trafficking in vitro using non-thyroid and thyroid epithelial cells. Methods: Immunofluorescence and Western blotting were performed to analyze NIS subcellular location and function in cells grown in monolayers under unpolarized and/or polarized conditions. Strategic NIS residues were mutated, and binding of NIS to clathrin adaptor complexes was determined by immunoprecipitation. Results: We show that NIS reaches the plasma membrane (PM) through a thyrotropin-dependent mechanism 24 hours after treatment with the hormone. We demonstrate that NIS basolateral trafficking is a clathrin-mediated mechanism, in which the clathrin adaptor complexes AP-1 (A and B) sort NIS from the trans-Golgi network (TGN) and recycling endosomes (REs). Specifically, we show that the AP-1B μ1 subunit controls NIS basolateral sorting through common REs. In its absence, NIS is apically missorted but remains functional. Additionally, direct NIS basolateral transport from the TGN to the basolateral membrane is mediated by AP-1A through clathrin-coated vesicles that also carry the transferrin receptor. Loss of the μ1 subunit of AP-1A is functionally compensated by AP-1B. Furthermore, loss of both subunits diminishes NIS trafficking to the PM. Finally, we demonstrate that AP-1A binds to the L121 and LL562/563 residues on NIS, whereas AP-1B binds to L583. Conclusions: Our findings highlight the novel involvement of the clathrin-coated machinery in basolateral NIS trafficking. Given that AP-1A expression is reduced in tumors, and its expression correlates with that of NIS, these findings will help uncover new targets in thyroid cancer treatment.
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Affiliation(s)
- Petrina Koumarianou
- Instituto de Investigaciones Biomédicas “Alberto Sols”, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Madrid (UAM), Spain
| | - Celia Fernández-Méndez
- Instituto de Investigaciones Biomédicas “Alberto Sols”, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Madrid (UAM), Spain
| | - Dánae Fajardo-Delgado
- Unidad de Tumores Endocrinos (UFIEC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Lidia Mirella Mielu
- Unidad de Tumores Endocrinos (UFIEC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Ciber de Cáncer (CIBERONC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Pilar Santisteban
- Instituto de Investigaciones Biomédicas “Alberto Sols”, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Madrid (UAM), Spain
- Ciber de Cáncer (CIBERONC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Address correspondence to: Pilar Santisteban, PhD, Instituto de Investigaciones Biomédicas “Alberto Sols”, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C/Arturo Duperier 4, Madrid 28029, Spain
| | - Antonio De la Vieja
- Unidad de Tumores Endocrinos (UFIEC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Ciber de Cáncer (CIBERONC), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
- Antonio De la Vieja, PhD, Unidad de Tumores Endocrinos (UFIEC), Instituto de Salud Carlos III (ISCIII), Ctra. Majadahonda-Pozuelo km 2,2., Majadahonda (Madrid) 28220, Spain
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21
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del Alamo D, DeSousa L, Nair RM, Rahman S, Meiler J, Mchaourab HS. Integrated AlphaFold2 and DEER investigation of the conformational dynamics of a pH-dependent APC antiporter. Proc Natl Acad Sci U S A 2022; 119:e2206129119. [PMID: 35969794 PMCID: PMC9407458 DOI: 10.1073/pnas.2206129119] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/08/2022] [Indexed: 11/18/2022] Open
Abstract
The Amino Acid-Polyamine-Organocation (APC) transporter GadC contributes to the survival of pathogenic bacteria under extreme acid stress by exchanging extracellular glutamate for intracellular γ-aminobutyric acid (GABA). Its structure, determined in an inward-facing conformation at alkaline pH, consists of the canonical LeuT-fold with a conserved five-helix inverted repeat, thereby resembling functionally divergent transporters such as the serotonin transporter SERT and the glucose-sodium symporter SGLT1. However, despite this structural similarity, it is unclear if the conformational dynamics of antiporters such as GadC follow the blueprint of these or other LeuT-fold transporters. Here, we used double electron-electron resonance (DEER) spectroscopy to monitor the conformational dynamics of GadC in lipid bilayers in response to acidification and substrate binding. To guide experimental design and facilitate the interpretation of the DEER data, we generated an ensemble of structural models in multiple conformations using a recently introduced modification of AlphaFold2 . Our experimental results reveal acid-induced conformational changes that dislodge the Cterminus from the permeation pathway coupled with rearrangement of helices that enables isomerization between inward- and outward-facing states. The substrate glutamate, but not GABA, modulates the dynamics of an extracellular thin gate without shifting the equilibrium between inward- and outward-facing conformations. In addition to introducing an integrated methodology for probing transporter conformational dynamics, the congruence of the DEER data with patterns of structural rearrangements deduced from ensembles of AlphaFold2 models illuminates the conformational cycle of GadC underpinning transport and exposes yet another example of the divergence between the dynamics of different families in the LeuT-fold.
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Affiliation(s)
- Diego del Alamo
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212
- Department of Chemistry, Vanderbilt University, Nashville, TN 37212
| | - Lillian DeSousa
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212
| | - Rahul M. Nair
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212
| | - Suhaila Rahman
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212
| | - Jens Meiler
- Department of Chemistry, Vanderbilt University, Nashville, TN 37212
- Institute for Drug Discovery, Leipzig University, Leipzig, Germany 04109
| | - Hassane S. Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37212
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22
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Maccari R, Ottanà R. Sodium-Glucose Cotransporter Inhibitors as Antidiabetic Drugs: Current Development and Future Perspectives. J Med Chem 2022; 65:10848-10881. [PMID: 35924548 PMCID: PMC9937539 DOI: 10.1021/acs.jmedchem.2c00867] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sodium-glucose cotransporter 2 (SGLT-2) inhibitors (gliflozins) represent the most recently approved class of oral antidiabetic drugs. SGLT-2 overexpression in diabetic patients contributes significantly to hyperglycemia and related complications. Therefore, SGLT-2 became a highly interesting therapeutic target, culminating in the approval for clinical use of dapagliflozin and analogues in the past decade. Gliflozins improve glycemic control through a novel insulin-independent mechanism of action and, moreover, exhibit significant cardiorenal protective effects in both diabetic and nondiabetic subjects. Therefore, gliflozins have received increasing attention, prompting extensive structure-activity relationship studies and optimization approaches. The discovery that intestinal SGLT-1 inhibition can provide a novel opportunity to control hyperglycemia, through a multifactorial mechanism, recently encouraged the design of low adsorbable inhibitors selectively directed to the intestinal SGLT-1 subtype as well as of dual SGLT-1/SGLT-2 inhibitors, representing a compelling strategy to identify new antidiabetic drug candidates.
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23
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Hatton CE, Brotherton DH, Spencer M, Cameron AD. Structure of cytosine transport protein CodB provides insight into nucleobase-cation symporter 1 mechanism. EMBO J 2022; 41:e110527. [PMID: 35775318 PMCID: PMC9379551 DOI: 10.15252/embj.2021110527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 05/01/2022] [Accepted: 05/26/2022] [Indexed: 12/29/2022] Open
Abstract
CodB is a cytosine transporter from the Nucleobase‐Cation‐Symport‐1 (NCS1) transporter family, a member of the widespread LeuT superfamily. Previous experiments with the nosocomial pathogen Pseudomonas aeruginosa have shown CodB as also important for the uptake of 5‐fluorocytosine, which has been suggested as a novel drug to combat antimicrobial resistance by suppressing virulence. Here we solve the crystal structure of CodB from Proteus vulgaris, at 2.4 Å resolution in complex with cytosine. We show that CodB carries out the sodium‐dependent uptake of cytosine and can bind 5‐fluorocytosine. Comparison of the substrate‐bound structures of CodB and the hydantoin transporter Mhp1, the only other NCS1 family member for which the structure is known, highlight the importance of the hydrogen bonds that the substrates make with the main chain at the breakpoint in the discontinuous helix, TM6. In contrast to other LeuT superfamily members, neither CodB nor Mhp1 makes specific interactions with residues on TM1. Comparison of the structures provides insight into the intricate mechanisms of how these proteins transport substrates across the plasma membrane.
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Affiliation(s)
| | | | - Mahalah Spencer
- School of Life Sciences, University of Warwick, Coventry, UK
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24
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Berlaga A, Kolomeisky AB. Understanding Mechanisms of Secondary Active Transport by Analyzing the Effects of Mutations and Stoichiometry. J Phys Chem Lett 2022; 13:5405-5412. [PMID: 35679158 DOI: 10.1021/acs.jpclett.2c01232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Biological cells frequently exhibit a so-called secondary active transport by moving various species across their membranes. In this mode of transport, an energetically favorable transmembrane gradient of one type of molecule is used to drive another type of molecule in the energetically unfavorable direction against their gradient. Although it is well established that conformational transitions play a critical role in functioning of transporters, the molecular details of underlying mechanisms remain not well understood. Here, we utilize a recently developed theoretical method to understand better the microscopic picture of secondary active transport. Specifically, we evaluate how mutations in different parts of transporters affect their dynamic properties. In addition, we present a possible explanation on existence of different stoichiometries in the secondary active transport. Our theoretical analysis clarifies several important aspects of complex biological transport phenomena.
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Affiliation(s)
- Alex Berlaga
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Anatoly B Kolomeisky
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
- Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, United States
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
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25
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Wu Z, Han Z, Zhou W, Sun X, Chen L, Yang S, Hu J, Li C. Insight into the Nucleoside Transport and Inhibition of Human ENT1. Curr Res Struct Biol 2022; 4:192-205. [PMID: 35677775 PMCID: PMC9168172 DOI: 10.1016/j.crstbi.2022.05.005] [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: 03/15/2022] [Revised: 05/02/2022] [Accepted: 05/18/2022] [Indexed: 12/03/2022] Open
Abstract
The human equilibrative nucleoside transporter 1 (hENT1) is an effective controller of adenosine signaling by regulating its extracellular and intracellular concentration, and has become a solid drug target of clinical used adenosine reuptake inhibitors (AdoRIs). Currently, the mechanisms of adenosine transport and inhibition for hENT1 remain unclear, which greatly limits the in-depth understanding of its inner workings as well as the development of novel inhibitors. In this work, the dynamic details of hENT1 underlie adenosine transport and the inhibition mechanism of the non-nucleoside AdoRIs dilazep both were investigated by comparative long-time unbiased molecular dynamics simulations. The calculation results show that the conformational transitions of hENT1 from the outward open to metastable occluded state are mainly driven by TM1, TM2, TM7 and TM9. One of the trimethoxyphenyl rings in dilazep serves as the adenosyl moiety of the endogenous adenosine substrate to competitively occupy the orthosteric site of hENT1. Due to extensive and various VDW interactions with N30, M33, M84, P308 and F334, the other trimethoxyphenyl ring is stuck in the opportunistic site near the extracellular side preventing the complete occlusion of thin gate simultaneously. Obviously, dilazep shows significant inhibitory activity by disrupting the local induce-fit action in substrate binding cavity and blocking the transport cycle of whole protein. This study not only reveals the nucleoside transport mechanism by hENT1 at atomic level, but also provides structural guidance for the subsequent design of novel non-nucleoside AdoRIs with enhanced pharmacologic properties. The transitions of hENT1 from the outward open to metastable occluded state are mainly driven by TM1, TM2, TM7 and TM9. The induce-fit action by adenosine recognition precedes. inward contraction of the extracellular side. Dilazep exerts its special hENT1 inhibitory function through competitive binding and allosteric regulation. A gating strategy of extracellular loop is revealed to ensure adenosine is firmly located in the transport cavity.
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Affiliation(s)
- Zhixiang Wu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Zhongjie Han
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Wenxue Zhou
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Xiaohan Sun
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Lei Chen
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Shuang Yang
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
| | - Jianping Hu
- Key Laboratory of Medicinal and Edible Plants Resources, Development of Sichuan Education Department, School of Pharmacy, Chengdu University, Chengdu, China
- Corresponding author. Key Laboratory of Medicinal and Edible Plants Resources, Development of Sichuan Education Department, School of Pharmacy, Chengdu University, Chengdu, 610106, China.
| | - Chunhua Li
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, China
- Corresponding author. Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing, 100124, China.
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26
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Donovan E, Avila C, Klausner S, Parikh V, Fenollar-Ferrer C, Blakely RD, Sarter M. Disrupted Choline Clearance and Sustained Acetylcholine Release In Vivo by a Common Choline Transporter Coding Variant Associated with Poor Attentional Control in Humans. J Neurosci 2022; 42:3426-3444. [PMID: 35232764 PMCID: PMC9034784 DOI: 10.1523/jneurosci.1334-21.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 02/20/2022] [Accepted: 02/23/2022] [Indexed: 11/21/2022] Open
Abstract
Transport of choline via the neuronal high-affinity choline transporter (CHT; SLC5A7) is essential for cholinergic terminals to synthesize and release acetylcholine (ACh). In humans, we previously demonstrated an association between a common CHT coding substitution (rs1013940; Ile89Val) and reduced attentional control as well as attenuated frontal cortex activation. Here, we used a CRISPR/Cas9 approach to generate mice expressing the I89V substitution and assessed, in vivo, CHT-mediated choline transport, and ACh release. Relative to wild-type (WT) mice, CHT-mediated clearance of choline in male and female mice expressing one or two Val89 alleles was reduced by over 80% in cortex and over 50% in striatum. Choline clearance in CHT Val89 mice was further reduced by neuronal inactivation. Deficits in ACh release, 5 and 10 min after repeated depolarization at a low, behaviorally relevant frequency, support an attenuated reloading capacity of cholinergic neurons in mutant mice. The density of CHTs in total synaptosomal lysates and neuronal plasma-membrane-enriched fractions was not impacted by the Val89 variant, indicating a selective impact on CHT function. When challenged with a visual disruptor to reveal attentional control mechanisms, Val89 mice failed to adopt a more conservative response bias. Structural modeling revealed that Val89 may attenuate choline transport by altering conformational changes of CHT that support normal transport rates. Our findings support the view that diminished sustained cholinergic signaling capacity underlies perturbed attentional performance in individuals expressing CHT Val89. The CHT Val89 mouse serves as a valuable model to study heritable risk for cognitive disorders arising from cholinergic dysfunction.SIGNIFICANCE STATEMENT Acetylcholine (ACh) signaling depends on the functional capacity of the neuronal choline transporter (CHT). Previous research demonstrated that humans expressing the common CHT coding variant Val89 exhibit attentional vulnerabilities and attenuated fronto-cortical activation during attention. Here, we find that mice engineered to express the Val89 variant exhibit reduced CHT-mediated choline clearance and a diminished capacity to sustain ACh release. Additionally, Val89 mice lack cognitive flexibility in response to an attentional challenge. These findings provide a mechanistic and cognitive framework for interpreting the attentional phenotype associated with the human Val89 variant and establish a model that permits a more invasive interrogation of CNS effects as well as the development of therapeutic strategies for those, including Val89 carriers, with presynaptic cholinergic perturbations.
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Affiliation(s)
- Eryn Donovan
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Cassandra Avila
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Sarah Klausner
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Vinay Parikh
- Department of Psychology & Neuroscience Program, Temple University, Philadelphia, Pennsylvania 19122
| | - Cristina Fenollar-Ferrer
- Laboratory of Molecular Genetics, Section of Human Genetics, National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland 20892
| | - Randy D Blakely
- Stiles-Nicholson Brain Institute and Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, Florida 33458
| | - Martin Sarter
- Department of Psychology, Neuroscience Program and Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109
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27
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Holling T, Nampoothiri S, Tarhan B, Schneeberger PE, Vinayan KP, Yesodharan D, Roy AG, Radhakrishnan P, Alawi M, Rhodes L, Girisha KM, Kang PB, Kutsche K. Novel biallelic variants expand the SLC5A6-related phenotypic spectrum. Eur J Hum Genet 2022; 30:439-449. [PMID: 35013551 PMCID: PMC8747999 DOI: 10.1038/s41431-021-01033-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 12/09/2021] [Accepted: 12/17/2021] [Indexed: 11/09/2022] Open
Abstract
The sodium (Na+):multivitamin transporter (SMVT), encoded by SLC5A6, belongs to the sodium:solute symporter family and is required for the Na+-dependent uptake of biotin (vitamin B7), pantothenic acid (vitamin B5), the vitamin-like substance α-lipoic acid, and iodide. Compound heterozygous SLC5A6 variants have been reported in individuals with variable multisystemic disorder, including failure to thrive, developmental delay, seizures, cerebral palsy, brain atrophy, gastrointestinal problems, immunodeficiency, and/or osteopenia. We expand the phenotypic spectrum associated with biallelic SLC5A6 variants affecting function by reporting five individuals from three families with motor neuropathies. We identified the homozygous variant c.1285 A > G [p.(Ser429Gly)] in three affected siblings and a simplex patient and the maternally inherited c.280 C > T [p.(Arg94*)] variant and the paternally inherited c.485 A > G [p.(Tyr162Cys)] variant in the simplex patient of the third family. Both missense variants were predicted to affect function by in silico tools. 3D homology modeling of the human SMVT revealed 13 transmembrane helices (TMs) and Tyr162 and Ser429 to be located at the cytoplasmic facing region of TM4 and within TM11, respectively. The SLC5A6 missense variants p.(Tyr162Cys) and p.(Ser429Gly) did not affect plasma membrane localization of the ectopically expressed multivitamin transporter suggesting reduced but not abolished function, such as lower catalytic activity. Targeted therapeutic intervention yielded clinical improvement in four of the five patients. Early molecular diagnosis by exome sequencing is essential for timely replacement therapy in affected individuals.
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Affiliation(s)
- Tess Holling
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | - Sheela Nampoothiri
- Department of Pediatric Genetics, Amrita Institute of Medical Sciences & Research Centre, Cochin, 682041, Kerala, India
| | - Bedirhan Tarhan
- Division of Pediatric Neurology, Department of Pediatrics, University of Florida College of Medicine, Gainesville, FL, 32610, USA
| | - Pauline E Schneeberger
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
- Amedes MVZ Wagnerstibbe für Laboratoriumsmedizin, Hämostaseologie, Humangenetik und Mikrobiologie Hannover, 30159, Hannover, Germany
| | | | - Dhanya Yesodharan
- Department of Pediatric Genetics, Amrita Institute of Medical Sciences & Research Centre, Cochin, 682041, Kerala, India
| | - Arun Grace Roy
- Department of Neurology, Amrita Institute of Medical Sciences & Research Centre, Cochin, 682041, Kerala, India
| | - Periyasamy Radhakrishnan
- Suma Genomics Pvt. Ltd, Manipal Universal Technology Business Incubator (MUTBI), Manipal, 576104, India
| | - Malik Alawi
- Bioinformatics Core, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany
| | | | - Katta Mohan Girisha
- Department of Medical Genetics, Kasturba Medical College, Manipal, 576104, India
| | - Peter B Kang
- Division of Pediatric Neurology, Department of Pediatrics, University of Florida College of Medicine, Gainesville, FL, 32610, USA.
- Paul and Sheila Wellstone Muscular Dystrophy Center, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
- Department of Neurology, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
- Institute for Translational Neuroscience, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany.
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28
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Barreto YB, Alencar AM. Random-walk model of the sodium-glucose transporter SGLT2 with stochastic steps and inhibition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:184004. [PMID: 35090150 DOI: 10.1088/1361-648x/ac4fea] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
Random-walk models are frequently used to model distinct natural phenomena such as diffusion processes, stock-market fluctuations, and biological systems. Here, we present a random-walk model to describe the dynamics of glucose uptake by the sodium-glucose transporter of type 2, SGLT2. Our starting point is the canonical alternating-access model, which suggests the existence of six states for the transport cycle. We propose the inclusion of two new states to this canonical model. The first state is added to implement the recent discovery that the Na+ion can exit before the sugar is released into the proximal tubule epithelial cells. The resulting model is a seven-state mechanism with stochastic steps. Then we determined the transition probabilities between these seven states and used them to write a set of master equations to describe the time evolution of the system. We showed that our model converges to the expected equilibrium configuration and that the binding of Na+and glucose to SGLT2 in the inward-facing conformation must be necessarily unordered. After that, we added another state to implement inhibition in the model. Our results reproduce the experimental dependence of glucose uptake on the inhibitor concentration and they reveal that the inhibitors act by decreasing the number of available SGLT2s, which increases the chances of glucose escaping reabsorption.
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Affiliation(s)
- Yan B Barreto
- Instituto de Física, Universidade de São Paulo, 05508-090 São Paulo, São Paulo, Brazil
| | - Adriano M Alencar
- Instituto de Física, Universidade de São Paulo, 05508-090 São Paulo, São Paulo, Brazil
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29
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Berlaga A, Kolomeisky AB. Theoretical study of active secondary transport: Unexpected differences in molecular mechanisms for antiporters and symporters. J Chem Phys 2022; 156:085102. [DOI: 10.1063/5.0082589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Successful functioning of biological cells relies on efficient translocation of different materials across cellular membranes. An important part of this transportation system is membrane channels that are known as antiporters and symporters. They exploit the energy stored as a trans-membrane gradient of one type of molecules to transport the other types of molecules against their gradients. For symporters, the directions of both fluxes for driving and driven species coincide, while for antiporters, the fluxes move in opposite directions. There are surprising experimental observations that despite differing only by the direction of transport fluxes, the molecular mechanisms of translocation adopted by antiporters and symporters seem to be drastically different. We present chemical-kinetic models to quantitatively investigate this phenomenon. Our theoretical approach allows us to explain why antiporters mostly utilize a single-site transportation when only one molecule of any type might be associated with the channel. At the same time, the transport in symporters requires two molecules of different types to be simultaneously associated with the channel. In addition, we investigate the kinetic constraints and efficiency of symporters and compare them with the same properties of antiporters. Our theoretical analysis clarifies some important physical–chemical features of cellular trans-membrane transport.
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Affiliation(s)
- Alex Berlaga
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
| | - Anatoly B. Kolomeisky
- Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
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30
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Niu Y, Liu R, Guan C, Zhang Y, Chen Z, Hoerer S, Nar H, Chen L. Structural basis of inhibition of the human SGLT2-MAP17 glucose transporter. Nature 2022; 601:280-284. [PMID: 34880493 DOI: 10.1038/s41586-021-04212-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/03/2021] [Indexed: 01/01/2023]
Abstract
Human sodium-glucose cotransporter 2 (hSGLT2) mediates the reabsorption of the majority of filtrated glucose in the kidney1. Pharmacological inhibition of hSGLT2 by oral small-molecule inhibitors, such as empagliflozin, leads to enhanced excretion of glucose and is widely used in the clinic to manage blood glucose levels for the treatment of type 2 diabetes1. Here we determined the cryogenic electron microscopy structure of the hSGLT2-MAP17 complex in the empagliflozin-bound state to an overall resolution of 2.95 Å. Our structure shows eukaryotic SGLT-specific structural features. MAP17 interacts with transmembrane helix 13 of hSGLT2. Empagliflozin occupies both the sugar-substrate-binding site and the external vestibule to lock hSGLT2 in an outward-open conformation, thus inhibiting the transport cycle. Our work provides a framework for understanding the mechanism of SLC5A family glucose transporters and also develops a foundation for the future rational design and optimization of new inhibitors targeting these transporters.
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Affiliation(s)
- Yange Niu
- 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
| | - Rui Liu
- 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
| | - Chengcheng Guan
- 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
| | - Yuan Zhang
- 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
| | - Zhixing 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, China
| | - Stefan Hoerer
- Boehringer-Ingelheim Pharma, GmbH & Co KG, Biberach, Germany
| | - Herbert Nar
- Boehringer-Ingelheim Pharma, GmbH & Co KG, Biberach, Germany
| | - 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, China.
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31
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Structural basis of the selective sugar transport in sodium-glucose cotransporters. J Mol Biol 2022; 434:167464. [DOI: 10.1016/j.jmb.2022.167464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 01/17/2022] [Accepted: 01/18/2022] [Indexed: 11/23/2022]
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32
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Wright EM. SGLT2 Inhibitors: Physiology and Pharmacology. KIDNEY360 2021; 2:2027-2037. [PMID: 35419546 PMCID: PMC8986039 DOI: 10.34067/kid.0002772021] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 09/17/2021] [Indexed: 02/07/2023]
Abstract
SGLTs are sodium glucose transporters found on the luminal membrane of the proximal tubule, where they reabsorb some 180 g (1 mol) of glucose from the glomerular filtrate each day. The natural glucoside phlorizin completely blocks glucose reabsorption. Oral SGLT2 inhibitors are rapidly absorbed into the blood stream, where theyremain in the circulation for hours. On glomerular filtration, they bind specifically to SGLT2 in the luminal membrane of the early proximal tubule to reduce glucose reabsorption by 50%-60%. Because of glucose excretion, these drugs lower plasma glucose and glycosylated hemoglobin levels in patients with type 2 diabetes mellitus. The drugs also protect against heart and renal failure. The aim of this review is to summarize what is known about the physiology of renal SGLTs and the pharmacology of SGLT drugs.
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Affiliation(s)
- Ernest M Wright
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California
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33
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Vallon V, Nakagawa T. Renal Tubular Handling of Glucose and Fructose in Health and Disease. Compr Physiol 2021; 12:2995-3044. [PMID: 34964123 PMCID: PMC9832976 DOI: 10.1002/cphy.c210030] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The proximal tubule of the kidney is programmed to reabsorb all filtered glucose and fructose. Glucose is taken up by apical sodium-glucose cotransporters SGLT2 and SGLT1 whereas SGLT5 and potentially SGLT4 and GLUT5 have been implicated in apical fructose uptake. The glucose taken up by the proximal tubule is typically not metabolized but leaves via the basolateral facilitative glucose transporter GLUT2 and is returned to the systemic circulation or used as an energy source by distal tubular segments after basolateral uptake via GLUT1. The proximal tubule generates new glucose in metabolic acidosis and the postabsorptive phase, and fructose serves as an important substrate. In fact, under physiological conditions and intake, fructose taken up by proximal tubules is primarily utilized for gluconeogenesis. In the diabetic kidney, glucose is retained and gluconeogenesis enhanced, the latter in part driven by fructose. This is maladaptive as it sustains hyperglycemia. Moreover, renal glucose retention is coupled to sodium retention through SGLT2 and SGLT1, which induces secondary deleterious effects. SGLT2 inhibitors are new anti-hyperglycemic drugs that can protect the kidneys and heart from failing independent of kidney function and diabetes. Dietary excess of fructose also induces tubular injury. This can be magnified by kidney formation of fructose under pathological conditions. Fructose metabolism is linked to urate formation, which partially accounts for fructose-induced tubular injury, inflammation, and hemodynamic alterations. Fructose metabolism favors glycolysis over mitochondrial respiration as urate suppresses aconitase in the tricarboxylic acid cycle, and has been linked to potentially detrimental aerobic glycolysis (Warburg effect). © 2022 American Physiological Society. Compr Physiol 12:2995-3044, 2022.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, California, USA,Department of Pharmacology, University of California San Diego, La Jolla, California, USA,VA San Diego Healthcare System, San Diego, California, USA,Correspondence to and
| | - Takahiko Nakagawa
- Division of Nephrology, Rakuwakai-Otowa Hospital, Kyoto, Japan,Correspondence to and
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34
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Ottolia M, John S, Hazan A, Goldhaber JI. The Cardiac Na + -Ca 2+ Exchanger: From Structure to Function. Compr Physiol 2021; 12:2681-2717. [PMID: 34964124 DOI: 10.1002/cphy.c200031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ca2+ homeostasis is essential for cell function and survival. As such, the cytosolic Ca2+ concentration is tightly controlled by a wide number of specialized Ca2+ handling proteins. One among them is the Na+ -Ca2+ exchanger (NCX), a ubiquitous plasma membrane transporter that exploits the electrochemical gradient of Na+ to drive Ca2+ out of the cell, against its concentration gradient. In this critical role, this secondary transporter guides vital physiological processes such as Ca2+ homeostasis, muscle contraction, bone formation, and memory to name a few. Herein, we review the progress made in recent years about the structure of the mammalian NCX and how it relates to function. Particular emphasis will be given to the mammalian cardiac isoform, NCX1.1, due to the extensive studies conducted on this protein. Given the degree of conservation among the eukaryotic exchangers, the information highlighted herein will provide a foundation for our understanding of this transporter family. We will discuss gene structure, alternative splicing, topology, regulatory mechanisms, and NCX's functional role on cardiac physiology. Throughout this article, we will attempt to highlight important milestones in the field and controversial topics where future studies are required. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.
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Affiliation(s)
- Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Scott John
- Department of Medicine (Cardiology), UCLA, Los Angeles, California, USA
| | - Adina Hazan
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
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35
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Transporter-protein structures show how salt gets a sweet ride into cells. Nature 2021; 601:194-196. [PMID: 34880482 DOI: 10.1038/d41586-021-03555-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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Han L, Qu Q, Aydin D, Panova O, Robertson MJ, Xu Y, Dror RO, Skiniotis G, Feng L. Structure and mechanism of the SGLT family of glucose transporters. Nature 2021; 601:274-279. [PMID: 34880492 DOI: 10.1038/s41586-021-04211-w] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 11/04/2021] [Indexed: 12/24/2022]
Abstract
Glucose is a primary energy source in living cells. The discovery in 1960s that a sodium gradient powers the active uptake of glucose in the intestine1 heralded the concept of a secondary active transporter that can catalyse the movement of a substrate against an electrochemical gradient by harnessing energy from another coupled substrate. Subsequently, coupled Na+/glucose transport was found to be mediated by sodium-glucose cotransporters2,3 (SGLTs). SGLTs are responsible for active glucose and galactose absorption in the intestine and for glucose reabsorption in the kidney4, and are targeted by multiple drugs to treat diabetes5. Several members within the SGLT family transport key metabolites other than glucose2. Here we report cryo-electron microscopy structures of the prototypic human SGLT1 and a related monocarboxylate transporter SMCT1 from the same family. The structures, together with molecular dynamics simulations and functional studies, define the architecture of SGLTs, uncover the mechanism of substrate binding and selectivity, and shed light on water permeability of SGLT1. These results provide insights into the multifaceted functions of SGLTs.
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Affiliation(s)
- Lei Han
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Qianhui Qu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Shanghai Stomatological Hospital, Institutes of Biomedical Science, Department of Systems Biology for Medicine, Fudan University, Shanghai, China
| | - Deniz Aydin
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Computer Science, Stanford University, Stanford, CA, USA.,Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA
| | - Ouliana Panova
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Michael J Robertson
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Yan Xu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Ron O Dror
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Computer Science, Stanford University, Stanford, CA, USA.,Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA
| | - Georgios Skiniotis
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
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37
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Artzi L, Alon A, Brock KP, Green AG, Tam A, Ramírez-Guadiana FH, Marks D, Kruse A, Rudner DZ. Dormant spores sense amino acids through the B subunits of their germination receptors. Nat Commun 2021; 12:6842. [PMID: 34824238 PMCID: PMC8617281 DOI: 10.1038/s41467-021-27235-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 11/01/2021] [Indexed: 01/19/2023] Open
Abstract
Bacteria from the orders Bacillales and Clostridiales differentiate into stress-resistant spores that can remain dormant for years, yet rapidly germinate upon nutrient sensing. How spores monitor nutrients is poorly understood but in most cases requires putative membrane receptors. The prototypical receptor from Bacillus subtilis consists of three proteins (GerAA, GerAB, GerAC) required for germination in response to L-alanine. GerAB belongs to the Amino Acid-Polyamine-Organocation superfamily of transporters. Using evolutionary co-variation analysis, we provide evidence that GerAB adopts a structure similar to an L-alanine transporter from this superfamily. We show that mutations in gerAB predicted to disrupt the ligand-binding pocket impair germination, while mutations predicted to function in L-alanine recognition enable spores to respond to L-leucine or L-serine. Finally, substitutions of bulkier residues at these positions cause constitutive germination. These data suggest that GerAB is the L-alanine sensor and that B subunits in this broadly conserved family function in nutrient detection.
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Affiliation(s)
- Lior Artzi
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
| | - Assaf Alon
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, MA, 02115, USA
| | - Kelly P Brock
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA, 02115, USA
| | - Anna G Green
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA, 02115, USA
| | - Amy Tam
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA, 02115, USA
| | | | - Debora Marks
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA, 02115, USA
| | - Andrew Kruse
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, MA, 02115, USA
| | - David Z Rudner
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA.
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38
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Udrea AM, Gradisteanu Pircalabioru G, Boboc AA, Mares C, Dinache A, Mernea M, Avram S. Advanced Bioinformatics Tools in the Pharmacokinetic Profiles of Natural and Synthetic Compounds with Anti-Diabetic Activity. Biomolecules 2021; 11:1692. [PMID: 34827690 PMCID: PMC8615418 DOI: 10.3390/biom11111692] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/06/2021] [Accepted: 11/08/2021] [Indexed: 12/12/2022] Open
Abstract
Diabetes represents a major health problem, involving a severe imbalance of blood sugar levels, which can disturb the nerves, eyes, kidneys, and other organs. Diabes management involves several synthetic drugs focused on improving insulin sensitivity, increasing insulin production, and decreasing blood glucose levels, but with unclear molecular mechanisms and severe side effects. Natural chemicals extracted from several plants such as Gymnema sylvestre, Momordica charantia or Ophiopogon planiscapus Niger have aroused great interest for their anti-diabetes activity, but also their hypolipidemic and anti-obesity activity. Here, we focused on the anti-diabetic activity of a few natural and synthetic compounds, in correlation with their pharmacokinetic/pharmacodynamic profiles, especially with their blood-brain barrier (BBB) permeability. We reviewed studies that used bioinformatics methods such as predicted BBB, molecular docking, molecular dynamics and quantitative structure-activity relationship (QSAR) to elucidate the proper action mechanisms of antidiabetic compounds. Currently, it is evident that BBB damage plays a significant role in diabetes disorders, but the molecular mechanisms are not clear. Here, we presented the efficacy of natural (gymnemic acids, quercetin, resveratrol) and synthetic (TAK-242, propofol, or APX3330) compounds in reducing diabetes symptoms and improving BBB dysfunctions. Bioinformatics tools can be helpful in the quest for chemical compounds with effective anti-diabetic activity that can enhance the druggability of molecular targets and provide a deeper understanding of diabetes mechanisms.
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Affiliation(s)
- Ana Maria Udrea
- Laser Department, National Institute for Laser, Plasma and Radiation Physics, 077125 Maurele, Romania; (A.M.U.); (A.D.)
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, 1 B. P. Hașdeu St., 50567 Bucharest, Romania;
| | - Gratiela Gradisteanu Pircalabioru
- Earth, Environmental and Life Sciences Section, Research Institute of the University of Bucharest, University of Bucharest, 1 B. P. Hașdeu St., 50567 Bucharest, Romania;
| | - Anca Andreea Boboc
- “Maria Sklodowska Curie” Emergency Children’s Hospital, 20, Constantin Brancoveanu Bd., 077120 Bucharest, Romania;
- Department of Pediatrics 8, “Carol Davila” University of Medicine and Pharmacy, Eroii Sanitari Bd., 020021 Bucharest, Romania
| | - Catalina Mares
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, 91–95 Splaiul Independentei, 050095 Bucharest, Romania; (C.M.); (S.A.)
| | - Andra Dinache
- Laser Department, National Institute for Laser, Plasma and Radiation Physics, 077125 Maurele, Romania; (A.M.U.); (A.D.)
| | - Maria Mernea
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, 91–95 Splaiul Independentei, 050095 Bucharest, Romania; (C.M.); (S.A.)
| | - Speranta Avram
- Department of Anatomy, Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, 91–95 Splaiul Independentei, 050095 Bucharest, Romania; (C.M.); (S.A.)
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39
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Abidi W, Torres-Sánchez L, Siroy A, Krasteva PV. Weaving of bacterial cellulose by the Bcs secretion systems. FEMS Microbiol Rev 2021; 46:6388354. [PMID: 34634120 PMCID: PMC8892547 DOI: 10.1093/femsre/fuab051] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 10/08/2021] [Indexed: 12/13/2022] Open
Abstract
Cellulose is the most abundant biological compound on Earth and while it is the predominant building constituent of plants, it is also a key extracellular matrix component in many diverse bacterial species. While bacterial cellulose was first described in the 19th century, it was not until this last decade that a string of structural works provided insights into how the cellulose synthase BcsA, assisted by its inner-membrane partner BcsB, senses c-di-GMP to simultaneously polymerize its substrate and extrude the nascent polysaccharide across the inner bacterial membrane. It is now established that bacterial cellulose can be produced by several distinct types of cellulose secretion systems and that in addition to BcsAB, they can feature multiple accessory subunits, often indispensable for polysaccharide production. Importantly, the last years mark significant progress in our understanding not only of cellulose polymerization per se but also of the bigger picture of bacterial signaling, secretion system assembly, biofilm formation and host tissue colonization, as well as of structural and functional parallels of this dominant biosynthetic process between the bacterial and eukaryotic domains of life. Here, we review current mechanistic knowledge on bacterial cellulose secretion with focus on the structure, assembly and cooperativity of Bcs secretion system components.
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Affiliation(s)
- Wiem Abidi
- 'Structural Biology of Biofilms' group, European Institute of Chemistry and Biology (IECB), F-33600 Pessac, France.,Université de Bordeaux, CNRS, Bordeaux INP, CBMN, UMR 5248, F-33600 Pessac, France.,École doctorale 'Innovation thérapeutique: du fundamental à l'appliqué' (ITFA), Université Paris-Saclay, 92296, Chatenay-Malabry, France
| | - Lucía Torres-Sánchez
- 'Structural Biology of Biofilms' group, European Institute of Chemistry and Biology (IECB), F-33600 Pessac, France.,Université de Bordeaux, CNRS, Bordeaux INP, CBMN, UMR 5248, F-33600 Pessac, France.,École doctorale 'Innovation thérapeutique: du fundamental à l'appliqué' (ITFA), Université Paris-Saclay, 92296, Chatenay-Malabry, France
| | - Axel Siroy
- 'Structural Biology of Biofilms' group, European Institute of Chemistry and Biology (IECB), F-33600 Pessac, France.,Université de Bordeaux, CNRS, Bordeaux INP, CBMN, UMR 5248, F-33600 Pessac, France
| | - Petya Violinova Krasteva
- 'Structural Biology of Biofilms' group, European Institute of Chemistry and Biology (IECB), F-33600 Pessac, France.,Université de Bordeaux, CNRS, Bordeaux INP, CBMN, UMR 5248, F-33600 Pessac, France
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40
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Portioli C, Ruiz Munevar MJ, De Vivo M, Cancedda L. Cation-coupled chloride cotransporters: chemical insights and disease implications. TRENDS IN CHEMISTRY 2021; 3:832-849. [PMID: 34604727 PMCID: PMC8461084 DOI: 10.1016/j.trechm.2021.05.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cation-coupled chloride cotransporters (CCCs) modulate the transport of sodium and/or potassium cations coupled with chloride anions across the cell membrane. CCCs thus help regulate intracellular ionic concentration and consequent cell volume homeostasis. This has been largely exploited in the past to develop diuretic drugs that act on CCCs expressed in the kidney. However, a growing wealth of evidence has demonstrated that CCCs are also critically involved in a great variety of other pathologies, motivating most recent drug discovery programs targeting CCCs. Here, we examine the structure–function relationship of CCCs. By linking recent high-resolution cryogenic electron microscopy (cryo-EM) data with older biochemical/functional studies on CCCs, we discuss the mechanistic insights and opportunities to design selective CCC modulators to treat diverse pathologies. The structural topology and function of all cation-coupled chloride cotransporters (CCCs) have been continuously investigated over the past 40 years, with great progress also thanks to the recent cryogenic electron microscopy (cryo-EM) resolution of the structures of five CCCs. In particular, such studies have clarified the structure–function relationship for the Na-K-Cl cotransporter NKCC1 and K-Cl cotransporters KCC1–4. The constantly growing evidence of the crucial involvement of CCCs in physiological and various pathological conditions, as well as the evidence of their wide expression in diverse body tissues, has promoted CCCs as targets for the discovery and development of new, safer, and more selective/effective drugs for a plethora of pathologies. Post-translational modification anchor points on the structure of CCCs may offer alternative strategies for small molecule drug discovery.
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Affiliation(s)
- Corinne Portioli
- Brain Development and Disease Laboratory, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy.,Laboratory of Molecular Modeling and Drug Discovery, IIT, Via Morego, 30 16163 Genoa, Italy
| | | | - Marco De Vivo
- Laboratory of Molecular Modeling and Drug Discovery, IIT, Via Morego, 30 16163 Genoa, Italy
| | - Laura Cancedda
- Brain Development and Disease Laboratory, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy.,Dulbecco Telethon Institute, Via Varese 16b, 00185 Rome, Italy
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41
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Arif R, Ahmad S, Mustafa G, Mahrosh HS, Ali M, Tahir ul Qamar M, Dar HR. Molecular Docking and Simulation Studies of Antidiabetic Agents Devised from Hypoglycemic Polypeptide-P of Momordica charantia. BIOMED RESEARCH INTERNATIONAL 2021; 2021:5561129. [PMID: 34589547 PMCID: PMC8476269 DOI: 10.1155/2021/5561129] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 08/30/2021] [Accepted: 09/04/2021] [Indexed: 12/15/2022]
Abstract
Diabetes mellitus termed as metabolic disorder is a collection of interlinked diseases and mainly body's inability to manage glucose level which leads to cardiovascular diseases, renal failure, neurological disorders, and many others. The drugs contemporarily used for diabetes have many inevitable side effects, and many of them have become less responsive to this multifactorial disorder. Momordica charantia commonly known as bitter gourd has many bioactive compounds with antidiabetic properties. The current study was designed to use computational methods to discover the best antidiabetic peptides devised from hypoglycemic polypeptide-P of M. charantia. The binding affinity and interaction patterns of peptides were evaluated against four receptor proteins (i.e., as agonists of insulin receptor and inhibitors of sodium-glucose cotransporter 1, dipeptidyl peptidase-IV, and glucose transporter 2) using molecular docking approach. A total of thirty-seven peptides were docked against these receptors. Out of which, top five peptides against each receptor were shortlisted based on their S-scores and binding affinities. Finally, the eight best ligands (i.e., LIVA, TSEP, EKAI, LKHA, EALF, VAEK, DFGAS, and EPGGGG) were selected as these ligands strictly followed Lipinski's rule of five and exhibited good ADMET profiling. One peptide EPGGGG showed activity towards insulin and SGLT1 receptor proteins. The top complex for both these targets was subjected to 50 ns of molecular dynamics simulations and MM-GBSA binding energy test that concluded both complexes as highly stable, and the intermolecular interactions were dominated by van der Waals and electrostatic energies. Overall, the selected ligands strongly fulfilled the drug-like evaluation criterion and proved to have good antidiabetic properties.
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Affiliation(s)
- Rawaba Arif
- Department of Biochemistry, Government College University, Faisalabad 38000, Pakistan
| | - Sajjad Ahmad
- Department of Health and Biological Sciences, Abasyn University, Peshawar, Pakistan
| | - Ghulam Mustafa
- Department of Biochemistry, Government College University, Faisalabad 38000, Pakistan
| | - Hafiza Salaha Mahrosh
- Department of Biochemistry, Government College University, Faisalabad 38000, Pakistan
| | - Muhammad Ali
- Department of Biotechnology, Akhuwat Faisalabad Institute of Research Science and Technology, Faisalabad 38000, Pakistan
| | | | - Hafiza Rabia Dar
- Department of Biochemistry, University of Agriculture, Faisalabad 38040, Pakistan
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42
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Lostao MP, Loo DD, Hernell O, Meeuwisse G, Martin MG, Wright EM. The Molecular Basis of Glucose Galactose Malabsorption in a Large Swedish Pedigree. FUNCTION (OXFORD, ENGLAND) 2021; 2:zqab040. [PMID: 34485913 PMCID: PMC8410129 DOI: 10.1093/function/zqab040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 08/10/2021] [Accepted: 08/12/2021] [Indexed: 01/12/2023]
Abstract
Glucose-galactose malabsorption (GGM) is due to mutations in the gene coding for the intestinal sodium glucose cotransporter SGLT1 (SLC5A1). Here we identify the rare variant Gln457Arg (Q457R) in a large pedigree of patients in the Västerbotten County in Northern Sweden with the clinical phenotype of GGM. The functional effect of the Q457R mutation was determined in protein expressed in Xenopus laevis oocytes using biophysical and biochemical methods. The mutant failed to transport the specific SGLT1 sugar analog α-methyl-D-glucopyranoside (αMDG). Q457R SGLT1 was synthesized in amounts comparable to the wild-type (WT) transporter. SGLT1 charge measurements and freeze-fracture electron microscopy demonstrated that the mutant protein was inserted into the plasma membrane. Electrophysiological experiments, both steady-state and presteady-state, demonstrated that the mutant bound sugar with an affinity lower than the WT transporter. Together with our previous studies on Q457C and Q457E mutants, we established that the positive charge on Q457R prevented the translocation of sugar from the outward-facing to inward-facing conformation. This is contrary to other GGM cases where missense mutations caused defects in trafficking SGLT1 to the plasma membrane. Thirteen GGM patients are now added to the pedigree traced back to the late 17th century. The frequency of the Q457R variant in Västerbotten County genomes, 0.0067, is higher than in the general Swedish population, 0.0015, and higher than the general European population, 0.000067. This explains the high number of GGM cases in this region of Sweden.
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Affiliation(s)
| | - Donald D Loo
- Department of Physiology, The Geffen School of Medicine, UCLA, USA
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Chew TA, Zhang J, Feng L. High-Resolution Views and Transport Mechanisms of the NKCC1 and KCC Transporters. J Mol Biol 2021; 433:167056. [PMID: 34022207 PMCID: PMC9722358 DOI: 10.1016/j.jmb.2021.167056] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/08/2021] [Accepted: 05/13/2021] [Indexed: 12/17/2022]
Abstract
Cation-chloride cotransporters (CCCs) are responsible for the coupled co-transport of Cl- with K+ and/or Na+ in an electroneutral manner. They play important roles in myriad fundamental physiological processes--from cell volume regulation to transepithelial solute transport and intracellular ion homeostasis--and are targeted by medicines commonly prescribed to treat hypertension and edema. After several decades of studies into the functions and pharmacology of these transporters, there have been several breakthroughs in the structural determination of CCC transporters. The insights provided by these new structures for the Na+/K+/Cl- cotransporter NKCC1 and the K+/Cl- cotransporters KCC1, KCC2, KCC3 and KCC4 have deepened our understanding of their molecular basis and transport function. This focused review discusses recent advances in the structural and mechanistic understanding of CCC transporters, including architecture, dimerization, functional roles of regulatory domains, ion binding sites, and coupled ion transport.
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Affiliation(s)
- Thomas A Chew
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jinru Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Reyna-Neyra A, Jung L, Chakrabarti M, Suárez MX, Amzel LM, Carrasco N. The Iodide Transport Defect-Causing Y348D Mutation in the Na +/I - Symporter Renders the Protein Intrinsically Inactive and Impairs Its Targeting to the Plasma Membrane. Thyroid 2021; 31:1272-1281. [PMID: 33779310 PMCID: PMC8377515 DOI: 10.1089/thy.2020.0931] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Background: The sodium/iodide (Na+/I-) symporter (NIS) mediates active transport of I- into the thyroid gland. Mutations in the SLC5A5 gene, which encodes NIS, cause I- transport defects (ITDs)-which, if left untreated, lead to congenital hypothyroidism and consequent cognitive and developmental deficiencies. The ITD-causing NIS mutation Y348D, located in transmembrane segment (TMS) 9, was reported in three Sudanese patients. Methods: We generated cDNAs coding for Y348D NIS and mutants with other hydrophilic and hydrophobic amino acid substitutions at position 348 and transfected them into cells. The activity of the resulting mutants was quantitated by radioiodide transport assays. NIS glycosylation was investigated by Western blotting after endoglycosidase H (Endo H) and PNGase-F glycosidase treatment. Subcellular localization of the mutant proteins was ascertained by flow cytometry analysis, cell surface biotinylation, and immunofluorescence. The intrinsic activity of Y348D was studied by measuring radioiodide transport in membrane vesicles prepared from Y348D-NIS-expressing cells. Our NIS homology models and molecular dynamics simulations were used to identify residues that interact with Y348 and investigate possible interactions between Y348 and the membrane. The sequences of several Slc5 family transporters were aligned, and a phylogenetic tree was generated in ClustalX. Results: Cells expressing Y348D NIS transport no I-. Furthermore, Y348D NIS is only partially glycosylated, is retained intracellularly, and is intrinsically inactive. Hydrophilic residues other than Asp at position 348 also yield NIS proteins that fail to be targeted to the plasma membrane (PM), whereas hydrophobic residues at this position, which we show do not interact with the membrane, rescue PM targeting and function. Conclusions: Y348D NIS does not reach the PM and is intrinsically inactive. Hydrophobic amino acid substitutions at position 348, however, preserve NIS activity. Our findings are consistent with our homology model's prediction that Y348 should face the side opposite the TMS9 residues that coordinate Na+ and participate in Na+ transport, and with the notion that Y348 interacts only with hydrophobic residues. Hydrophilic or charged residues at position 348 have deleterious effects on NIS PM targeting and activity, whereas a hydrophobic residue at this position rescues NIS activity.
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Affiliation(s)
- Andrea Reyna-Neyra
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lara Jung
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Mayukh Chakrabarti
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Mikel X. Suárez
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - L. Mario Amzel
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Nancy Carrasco
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
- Address correspondence to: Nancy Carrasco, MD, Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 2215 Garland Avenue, 707 Light Hall, Nashville, TN 37232-0615, USA
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Wirtz L, Eder M, Brand AK, Jung H. HutT functions as the major L-histidine transporter in Pseudomonas putida KT2440. FEBS Lett 2021; 595:2113-2126. [PMID: 34245008 DOI: 10.1002/1873-3468.14159] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/01/2021] [Accepted: 07/06/2021] [Indexed: 11/06/2022]
Abstract
Histidine is an important carbon and nitrogen source of γ-proteobacteria and can affect bacteria-host interactions. The mechanisms of histidine uptake are only partly understood. Here, we analyze functional properties of the putative histidine transporter HutT of the soil bacterium Pseudomonas putida. The hutT gene is part of the histidine utilization operon, and the gene product belongs to the amino acid-polyamine-organocation (APC) family of secondary transporters. Deletion of hutT severely impairs growth of P. putida on histidine, suggesting that the encoded transporter is the major histidine uptake system of P. putida. Transport experiments with cells and purified and reconstituted protein indicate that HutT functions as a high-affinity histidine : proton symporter with high specificity for the amino acid. Substitution analyses identified amino acids crucial for HutT function.
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Affiliation(s)
- Larissa Wirtz
- Division of Microbiology, Department of Biology 1, Ludwig Maximilians University Munich, Martinsried, Germany
| | - Michelle Eder
- Division of Microbiology, Department of Biology 1, Ludwig Maximilians University Munich, Martinsried, Germany
| | - Anna-Katharina Brand
- Division of Microbiology, Department of Biology 1, Ludwig Maximilians University Munich, Martinsried, Germany
| | - Heinrich Jung
- Division of Microbiology, Department of Biology 1, Ludwig Maximilians University Munich, Martinsried, Germany
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Abstract
Nucleosides play central roles in all facets of life, from metabolism to cellular signaling. Because of their physiochemical properties, nucleosides are lipid bilayer impermeable and thus rely on dedicated transport systems to cross biological membranes. In humans, two unrelated protein families mediate nucleoside membrane transport: the concentrative and equilibrative nucleoside transporter families. The objective of this review is to provide a broad outlook on the current status of nucleoside transport research. We will discuss the role played by nucleoside transporters in human health and disease, with emphasis placed on recent structural advancements that have revealed detailed molecular principles of these important cellular transport systems and exploitable pharmacological features.
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Affiliation(s)
- Nicholas J. Wright
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
- Correspondence and requests for materials should be addressed to: S.-Y. Lee., , tel: 919-684-1005, fax: 919-684-8885
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47
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Pizzagalli MD, Bensimon A, Superti‐Furga G. A guide to plasma membrane solute carrier proteins. FEBS J 2021; 288:2784-2835. [PMID: 32810346 PMCID: PMC8246967 DOI: 10.1111/febs.15531] [Citation(s) in RCA: 168] [Impact Index Per Article: 56.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 08/07/2020] [Accepted: 08/17/2020] [Indexed: 12/13/2022]
Abstract
This review aims to serve as an introduction to the solute carrier proteins (SLC) superfamily of transporter proteins and their roles in human cells. The SLC superfamily currently includes 458 transport proteins in 65 families that carry a wide variety of substances across cellular membranes. While members of this superfamily are found throughout cellular organelles, this review focuses on transporters expressed at the plasma membrane. At the cell surface, SLC proteins may be viewed as gatekeepers of the cellular milieu, dynamically responding to different metabolic states. With altered metabolism being one of the hallmarks of cancer, we also briefly review the roles that surface SLC proteins play in the development and progression of cancer through their influence on regulating metabolism and environmental conditions.
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Affiliation(s)
- Mattia D. Pizzagalli
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Ariel Bensimon
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Giulio Superti‐Furga
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
- Center for Physiology and PharmacologyMedical University of ViennaAustria
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Guo K, Wang X, Huang B, Wu X, Shen S, Lin Z, Zhao J, Cai Z. Comparative study on the intestinal absorption of three gastrodin analogues via the glucose transport pathway. Eur J Pharm Sci 2021; 163:105839. [PMID: 33852971 DOI: 10.1016/j.ejps.2021.105839] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 03/31/2021] [Accepted: 04/08/2021] [Indexed: 10/21/2022]
Abstract
Gastrodin is the main active constituent of Tianma, a famous traditional Chinese herbal medicine. Our previous research has found that gastrodin is absorbed rapidly in the intestine by the sodium-dependent glucose transporter 1 (SGLT1). In the current report, gastrodin is the best glycoside compound absorbed via the glucose transport pathway. This study aimed to investigate the effect of the slight difference in chemical structure on the drug intestinal absorption via the glucose transport pathway. Traditional biopharmaceutical and computer-aided molecular docking methods were used to evaluate the intestinal absorption characteristics of three gastrodin analogues, namely, salicin, arbutin and 4-methoxyphenyl-β-D-glucoside (4-MG). The oil-water partition coefficient (logP) experiments showed that the logP values of the gastrodin analogues followed the order: 4-MG > salicin > arbutin. In vitro Caco-2 cell transport experiments demonstrated that the apparent permeability coefficient (Papp) value of arbutin was higher than those of salicin and 4-MG. In situ single-pass intestinal perfusion experiments showed that the absorption of arbutin and 4-MG was better than that of salicin and that the absorption of the three compounds in the colon was lower than that in the small intestine. Quantitative real-time polymerase chain reaction results confirmed that the SGLT1 mRNA expression in the small intestine of rats was obviously higher than that in the colon of rats. In vivo pharmacokinetic experiments demonstrated that the oral bioavailability of salicin was lower than those of arbutin and 4-MG. In vitro and in vivo experiments showed that glucose or phlorizin (SGLT1 inhibitor) could decrease the intestinal absorption of the three compounds. Contrary to the above biopharmaceutical experiments, the computer-aided molecular docking test showed that the affinity of salicin to the vSGLT receptor was stronger than those of arbutin and 4-MG. In conclusion, the SGLT1 can facilitate the intestinal absorption of salicin, arbutin and 4-MG, and the slight difference in chemical structure can affect absorption.
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Affiliation(s)
- Kunkun Guo
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Xin Wang
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Baolin Huang
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Xiaoyun Wu
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Shuimei Shen
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Zimin Lin
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China
| | - Jie Zhao
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China.
| | - Zheng Cai
- NMPA Key Laboratory for Research and Evaluation of Drug Metabolism, School of Pharmaceutical Sciences, Southern Medical University, 510515 Guangzhou, China; TCM-Integrated Hospital of Southern Medical University, 510315 Guangzhou, China.
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Function Trumps Form in Two Sugar Symporters, LacY and vSGLT. Int J Mol Sci 2021; 22:ijms22073572. [PMID: 33808202 PMCID: PMC8037263 DOI: 10.3390/ijms22073572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 11/21/2022] Open
Abstract
Active transport of sugars into bacteria occurs through symporters driven by ion gradients. LacY is the most well-studied proton sugar symporter, whereas vSGLT is the most characterized sodium sugar symporter. These are members of the major facilitator (MFS) and the amino acid-Polyamine organocation (APS) transporter superfamilies. While there is no structural homology between these transporters, they operate by a similar mechanism. They are nano-machines driven by their respective ion electrochemical potential gradients across the membrane. LacY has 12 transmembrane helices (TMs) organized in two 6-TM bundles, each containing two 3-helix TM repeats. vSGLT has a core structure of 10 TM helices organized in two inverted repeats (TM 1–5 and TM 6–10). In each case, a single sugar is bound in a central cavity and sugar selectivity is determined by hydrogen- and hydrophobic- bonding with side chains in the binding site. In vSGLT, the sodium-binding site is formed through coordination with carbonyl- and hydroxyl-oxygens from neighboring side chains, whereas in LacY the proton (H3O+) site is thought to be a single glutamate residue (Glu325). The remaining challenge for both transporters is to determine how ion electrochemical potential gradients drive uphill sugar transport.
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Fairweather SJ, Shah N, Brӧer S. Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 21:13-127. [PMID: 33052588 DOI: 10.1007/5584_2020_584] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.
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Affiliation(s)
- Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia. .,Resarch School of Chemistry, Australian National University, Canberra, ACT, Australia.
| | - Nishank Shah
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Brӧer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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