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Bhatt M, Lazzarin E, Alberto-Silva AS, Domingo G, Zerlotti R, Gradisch R, Bazzone A, Sitte HH, Stockner T, Bossi E. Unveiling the crucial role of betaine: modulation of GABA homeostasis via SLC6A1 transporter (GAT1). Cell Mol Life Sci 2024; 81:269. [PMID: 38884791 DOI: 10.1007/s00018-024-05309-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/04/2024] [Accepted: 06/06/2024] [Indexed: 06/18/2024]
Abstract
Betaine is an endogenous osmolyte that exhibits therapeutic potential by mitigating various neurological disorders. However, the underlying cellular and molecular mechanisms responsible for its neuroprotective effects remain puzzling.In this study, we describe a possible mechanism behind the positive impact of betaine in preserving neurons from excitotoxicity. Here we demonstrate that betaine at low concentration modulates the GABA uptake by GAT1 (slc6a1), the predominant GABA transporter in the central nervous system. This modulation occurs through the temporal inhibition of the transporter, wherein prolonged occupancy by betaine impedes the swift transition of the transporter to the inward conformation. Importantly, the modulatory effect of betaine on GAT1 is reversible, as the blocking of GAT1 disappears with increased extracellular GABA. Using electrophysiology, mass spectroscopy, radiolabelled cellular assay, and molecular dynamics simulation we demonstrate that betaine has a dual role in GAT1: at mM concentration acts as a slow substrate, and at µM as a temporal blocker of GABA, when it is below its K0.5. Given this unique modulatory characteristic and lack of any harmful side effects, betaine emerges as a promising neuromodulator of the inhibitory pathways improving GABA homeostasis via GAT1, thereby conferring neuroprotection against excitotoxicity.
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Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Ana Sofia Alberto-Silva
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Guido Domingo
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy
| | - Rocco Zerlotti
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339, Munich, Germany
| | - Ralph Gradisch
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Andre Bazzone
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339, Munich, Germany
| | - Harald H Sitte
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
- Hourani Center for Applied Scientific Research, Al-Ahliyya Amman University, Amman, 19328, Jordan
- Center for Addiction Research and Science, Medical University of Vienna, 1090, Vienna, Austria
| | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Elena Bossi
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy.
- Centre for Neuroscience, University of Insubria, 21100, Varese, Italy.
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Drew D, Boudker O. Ion and lipid orchestration of secondary active transport. Nature 2024; 626:963-974. [PMID: 38418916 DOI: 10.1038/s41586-024-07062-3] [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: 06/27/2023] [Accepted: 01/12/2024] [Indexed: 03/02/2024]
Abstract
Transporting small molecules across cell membranes is an essential process in cell physiology. Many structurally diverse, secondary active transporters harness transmembrane electrochemical gradients of ions to power the uptake or efflux of nutrients, signalling molecules, drugs and other ions across cell membranes. Transporters reside in lipid bilayers on the interface between two aqueous compartments, where they are energized and regulated by symported, antiported and allosteric ions on both sides of the membrane and the membrane bilayer itself. Here we outline the mechanisms by which transporters couple ion and solute fluxes and discuss how structural and mechanistic variations enable them to meet specific physiological needs and adapt to environmental conditions. We then consider how general bilayer properties and specific lipid binding modulate transporter activity. Together, ion gradients and lipid properties ensure the effective transport, regulation and distribution of small molecules across cell membranes.
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Affiliation(s)
- David Drew
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, USA.
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Clarke A, Farr CV, El-Kasaby A, Szöllősi D, Freissmuth M, Sucic S, Stockner T. Probing binding and occlusion of substrate in the human creatine transporter-1 by computation and mutagenesis. Protein Sci 2024; 33:e4842. [PMID: 38032325 PMCID: PMC10751730 DOI: 10.1002/pro.4842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 12/01/2023]
Abstract
In chordates, energy buffering is achieved in part through phosphocreatine, which requires cellular uptake of creatine by the membrane-embedded creatine transporter (CRT1/SLC6A8). Mutations in human slc6a8 lead to creatine transporter deficiency syndrome, for which there is only limited treatment. Here, we used a combined homology modeling, molecular dynamics, and experimental approach to generate a structural model of CRT1. Our observations support the following conclusions: contrary to previous proposals, C144, a key residue in the substrate binding site, is not present in a charged state. Similarly, the side chain D458 must be present in a protonated form to maintain the structural integrity of CRT1. Finally, we identified that the interaction chain Y148-creatine-Na+ is essential to the process of occlusion, which occurs via a "hold-and-pull" mechanism. The model should be useful to study the impact of disease-associated point mutations on the folding of CRT1 and identify approaches which correct folding-deficient mutants.
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Affiliation(s)
- Amy Clarke
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Clemens V Farr
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Daniel Szöllősi
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Shahsavar A, Wellendorph P. GABA transport cycle: beyond a GAT feeling. Nat Struct Mol Biol 2023:10.1038/s41594-023-01032-5. [PMID: 37400656 DOI: 10.1038/s41594-023-01032-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023]
Affiliation(s)
- Azadeh Shahsavar
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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