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Chen SJ, Cho RL, Yeh SHH, Tsai MC, Chuang YP, Lien CF, Chiu CH, Yeh YW, Lin CS, Ma KH. Pitavastatin attenuates hypercholesterolemia-induced decline in serotonin transporter availability. Lipids Health Dis 2024; 23:250. [PMID: 39154177 PMCID: PMC11330603 DOI: 10.1186/s12944-024-02236-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 08/01/2024] [Indexed: 08/19/2024] Open
Abstract
INTRODUCTION Hypercholesterolemia is associated with increased inflammation and impaired serotonin neurotransmission, potentially contributing to depressive symptoms. However, the role of statins, particularly pitavastatin, in modulating serotonin transporter (SERT) function within this context remains underexplored. This study aimed to investigate whether pitavastatin counteracts the neurobiological effects of hypercholesterolemia. METHODS Low-density lipoprotein receptor knockout (LDLR-/-) mice on a C57BL/6 background were assigned to three groups: a control group fed a standard chow diet, a group fed a high-fat diet (HFD), and a third group fed a high-fat diet supplemented with pitavastatin (HFD + Pita). We evaluated the effects of HFD with or without pitavastatin on lipid profiles, inflammatory markers, and SERT availability using small-animal positron emission tomography (PET) scans with the radioligand 4-[18F]-ADAM over a 20-week period. RESULTS Pitavastatin treatment in HFD-fed mice significantly reduced both total cholesterol and LDL cholesterol levels in HFD-fed mice compared to those on HFD alone. Elevated inflammatory markers such as IL-1α, MCP-1/CCL2, and TNF-α in HFD mice were notably decreased in the HFD + Pita group. PET scans showed reduced SERT availability in the brains of HFD mice; however, pitavastatin improved this in brain regions associated with mood regulation, suggesting enhanced serotonin neurotransmission. Additionally, the sucrose preference test showed a trend towards increased preference in the HFD + Pita group compared to the HFD group, indicating a potential reduction in depressive-like behavior. CONCLUSION Our findings demonstrate that pitavastatin not only lowers cholesterol and reduces inflammation but also enhances SERT availability, suggesting a potential role in alleviating depressive symptoms associated with hypercholesterolemia. These results highlight the multifaceted benefits of pitavastatin, extending beyond its lipid-lowering effects to potentially improving mood regulation and neurotransmitter function.
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Affiliation(s)
- Sy-Jou Chen
- Department of Emergency Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan.
| | - Rou-Ling Cho
- Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
| | - Skye Hsin-Hsien Yeh
- School of Medicine, National Defense Medical Center, Taipei, Taiwan
- Brain Research Center, National Yang Ming Chaio Tung University, Taipei, Taiwan
| | - Min-Chien Tsai
- Department of Physiology and Biophysics, Graduate Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | - Yi-Ping Chuang
- Department of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan
- Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan
| | - Chih-Feng Lien
- Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan
| | - Chuang-Hsin Chiu
- Department of Nuclear Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Yi-Wei Yeh
- Department of Psychiatry, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chin-Sheng Lin
- Division of Cardiology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, 114, Taiwan.
| | - Kuo-Hsing Ma
- Department of Biology and Anatomy, National Defense Medical Center, Taipei, 114, Taiwan.
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Hosamani S, Chakraborty S. Cholesterol Allosterically Modulates the Structure and Dynamics of the Taurocholate Export Pump (ABCB11). J Phys Chem Lett 2024; 15:7901-7908. [PMID: 39058973 DOI: 10.1021/acs.jpclett.4c01341] [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: 07/28/2024]
Abstract
The BSEP/ABCB11 transmembrane protein translocates taurine- and glycine-conjugated bile salts across the hepatocyte bilayer driven by ATP-hydrolysis. Direct inhibition of BSEP/ABCB11 leads to idiosyncratic drug-induced liver injury. ABCB11 is localized within the cholesterol-enriched lipid raft, and membrane cholesterol depletion leads to impaired taurocholate transport. However, structural insight into the mechanism of the cholesterol-mediated regulation of ABCB11 activity remains elusive. We used extensive molecular dynamics simulation coupled with well-tempered metadynamics to elucidate the role of membrane cholesterol in the structure and dynamics of ABCB11. We identified specific high-residence binding sites for cholesterol within the transmembrane domain. The free-energy simulations have elucidated that the bound cholesterol stabilizes the "inward-open" conformation of the protein. Cholesterol-ABCB11 interactions trigger allosteric communications between the transmembrane and nucleotide-binding domains through the linker region. Cholesterol depletion destabilizes the allosteric network of the protein. As a result, it adopts a more collapsed form with a reduced volume of the taurocholate-binding pocket.
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Affiliation(s)
- Soundharya Hosamani
- Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS), Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, India
| | - Sandipan Chakraborty
- Center for Innovation in Molecular and Pharmaceutical Sciences (CIMPS), Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500046, India
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3
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O'Brien TM. Acute eosinophilic pneumonia-like syndrome post-initiation of vortioxetine. Drug Ther Bull 2024:dtb.2024.e254254rep. [PMID: 38886023 DOI: 10.1136/dtb.2024.e254254rep] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
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4
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Cai J, Cheung J, Cheung SWM, Chin KTC, Leung RWK, Lam RST, Sharma R, Yiu JHC, Woo CW. Butyrate acts as a positive allosteric modulator of the 5-HT transporter to decrease availability of 5-HT in the ileum. Br J Pharmacol 2024; 181:1654-1670. [PMID: 38129963 DOI: 10.1111/bph.16305] [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: 04/28/2023] [Revised: 10/23/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND AND PURPOSE Radiation therapy-induced gastrointestinal distress is partly associated with the elimination of gut microbiota. The effectiveness of 5-HT receptor antagonists to treat radiation therapy-induced emesis implies a pathophysiological role of 5-HT. Peripheral 5-HT is derived from intestinal epithelium. We have investigated the role of gut microbiota in regulating intestinal 5-HT availability. EXPERIMENTAL APPROACH A radiation therapy murine model accompanied by faecal microbiota transplantation from donors fed different diets was investigated, and mouse ileal organoids were used for mechanistic studies. The clinical relevance was validated by a small-scale human study. KEY RESULTS Short-term high-fat diet (HFD) induced gut bacteria to produce butyrate. Irradiated mice receiving HFD-induced microbiome had the lowest ileal levels of 5-HT, compared with other recipients. Treatment with butyrate increased 5-HT uptake in mouse ileal organoids, assayed by the real-time tracking of a fluorescent substrate for monoamine transporters. Silencing the 5-HT transporter (SERT) in the organoids abolished butyrate-stimulated 5-HT uptake. The competitive tests using different types of selective 5-HT reuptake inhibitors suggested that butyrate acted as a positive allosteric modulator of SERT. In human gut microbiota, butyrate production was associated with the interconversion between acetate and butyrate. Faecal contents of both acetate and butyrate were negatively associated with serum 5-HT, but only butyrate was positively correlated with body mass index in humans. CONCLUSION AND IMPLICATIONS Short-term HFD may be beneficial for alleviating gastrointestinal reactions by increasing butyrate to suppress local 5-HT levels and providing energy to cancer patients given radiation therapy.
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Affiliation(s)
- Jieling Cai
- State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Jamie Cheung
- State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Samson W M Cheung
- State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Karie T C Chin
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Ricky W K Leung
- Centre for PanorOmic Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Ronald S T Lam
- Centre for PanorOmic Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Rakesh Sharma
- Centre for PanorOmic Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Jensen H C Yiu
- State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Connie W Woo
- State Key Laboratory of Pharmaceutical Biotechnology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
- Micon Analytics, Toronto, Canada
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5
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Kalinichenko L, Kornhuber J, Sinning S, Haase J, Müller CP. Serotonin Signaling through Lipid Membranes. ACS Chem Neurosci 2024; 15:1298-1320. [PMID: 38499042 PMCID: PMC10995955 DOI: 10.1021/acschemneuro.3c00823] [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: 12/20/2023] [Revised: 02/22/2024] [Accepted: 02/27/2024] [Indexed: 03/20/2024] Open
Abstract
Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.
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Affiliation(s)
- Liubov
S. Kalinichenko
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Johannes Kornhuber
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Steffen Sinning
- Department
of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Jana Haase
- School
of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Christian P. Müller
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
- Institute
of Psychopharmacology, Central Institute of Mental Health, Medical
Faculty Mannheim, Heidelberg University, 69047, Mannheim, Germany
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Sadykova D, Nigmatullina R, Salakhova K, Slastnikova E, Galimova L, Khaliullina C, Valeeva I. Membrane Transporter of Serotonin and Hypercholesterolemia in Children. Int J Mol Sci 2024; 25:767. [PMID: 38255840 PMCID: PMC10815017 DOI: 10.3390/ijms25020767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/03/2024] [Accepted: 01/05/2024] [Indexed: 01/24/2024] Open
Abstract
The serotonin membrane transporter is one of the main mechanisms of plasma serotonin concentration regulation. Serotonin plays an important role in the pathogenesis of various cardiovascular diseases, stimulating the proliferation of smooth muscle cells, key cells in the process of hypertrophic vascular remodeling. Vascular remodeling is one of the leading prognostically unfavorable factors of atherosclerosis, the main manifestation of familial hypercholesterolemia. Familial hypercholesterolemia is one of the most common genetically determined lipid metabolism disorders and occurs in 1 in 313 people. The aim of our study was to investigate the levels of plasma and platelet serotonin, 5-hydroxyindoleacetic acid, and membrane transporter in a cross-sectional study of two pediatric groups, including patients with familial hypercholesterolemia and the control group, which consisted of apparently healthy children without cardiovascular diseases. The study involved 116 children aged 5 to 17 years old. The proportion of boys was 50% (58/116) and the average age of the children was 10.5 years (CI 2.8-18.1). The concentrations of serotonin in blood plasma and platelets and 5-hydroxyindoleacetic acid were higher in children with familial hypercholesterolemia than in the controls. The concentration of the serotonin transporter in platelets in healthy children, compared with the main group, was 1.3 times higher. A positive correlation was revealed between the level of serotonin (5-HT and PWV: ρ = 0.6, p < 0.001), its transporter (SERT and PWV: ρ = 0.5, p < 0.001), and the main indicators of arterial vascular stiffness. Our study revealed the relationship between high serotonin and SERT concentrations and markers of arterial stiffness. The results we obtained suggest the involvement of serotonin and SERT in the process of vascular remodeling in familial hypercholesterolemia in children.
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Affiliation(s)
- Dinara Sadykova
- Department of Hospital Pediatrics, Kazan State Medical University, 420012 Kazan, Russia; (K.S.); (E.S.); (L.G.); (C.K.)
| | - Razina Nigmatullina
- Department of Normal Physiology, Kazan State Medical University, 420012 Kazan, Russia;
| | - Karina Salakhova
- Department of Hospital Pediatrics, Kazan State Medical University, 420012 Kazan, Russia; (K.S.); (E.S.); (L.G.); (C.K.)
| | - Evgeniia Slastnikova
- Department of Hospital Pediatrics, Kazan State Medical University, 420012 Kazan, Russia; (K.S.); (E.S.); (L.G.); (C.K.)
- Children’s Republican Clinical Hospital, 420138 Kazan, Russia
| | - Liliya Galimova
- Department of Hospital Pediatrics, Kazan State Medical University, 420012 Kazan, Russia; (K.S.); (E.S.); (L.G.); (C.K.)
- Children’s Republican Clinical Hospital, 420138 Kazan, Russia
| | - Chulpan Khaliullina
- Department of Hospital Pediatrics, Kazan State Medical University, 420012 Kazan, Russia; (K.S.); (E.S.); (L.G.); (C.K.)
| | - Ildaria Valeeva
- Central Research Laboratory, Kazan State Medical University, 420012 Kazan, Russia;
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7
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Chater RC, Quinn AS, Wilson K, Frangos ZJ, Sutton P, Jayakumar S, Cioffi CL, O'Mara ML, Vandenberg RJ. The efficacy of the analgesic GlyT2 inhibitor, ORG25543, is determined by two connected allosteric sites. J Neurochem 2023. [PMID: 38131125 DOI: 10.1111/jnc.16028] [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: 09/11/2023] [Revised: 10/23/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023]
Abstract
Glycine Transporter 2 (GlyT2) inhibitors have shown considerable potential as analgesics for the treatment of neuropathic pain but also display considerable side effects. One potential source of side effects is irreversible inhibition. In this study, we have characterized the mechanism of ORG25543 inhibition of GlyT2 by first considering three potential ligand binding sites on GlyT2-the substrate site, the vestibule allosteric site and the lipid allosteric site. The three sites were tested using a combination of molecular dynamics simulations and analysis of the inhibition of glycine transport of a series point mutated GlyT2 using electrophysiological methods. We demonstrate that the lipid allosteric site on GlyT2 is the most likely binding site for ORG25543. We also demonstrate that cholesterol derived from the cell membrane can form specific interactions with inhibitor-bound transporters to form an allosteric network of regulatory sites. These observations will guide the future design of GlyT2 inhibitors with the objective of minimising on-target side effects and improving the therapeutic window for the treatment of patients suffering from neuropathic pain.
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Affiliation(s)
- Ryan Cantwell Chater
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Ada S Quinn
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Katie Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Zachary J Frangos
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Patrick Sutton
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Robert J Vandenberg
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
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8
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Chen R. Cholesterol modulation of interactions between psychostimulants and dopamine transporters. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2023; 99:35-59. [PMID: 38467486 DOI: 10.1016/bs.apha.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
The dopamine transporter (DAT) is a key site of action for cocaine and amphetamines. Dysfunctional DAT is associated with aberrant synaptic dopamine transmission and enhanced drug-seeking and taking behavior. Studies in cultured cells and ex vivo suggest that DAT function is sensitive to membrane cholesterol content. Although it is largely unknown whether psychostimulants alter cholesterol metabolism in the brain, emerging evidence indicates that peripheral cholesterol metabolism is altered in patients with psychostimulant use disorder and circulating cholesterol levels are associated with vulnerability to relapse. Cholesterol interacts with sphingolipids forming lipid raft microdomains on the membrane. These cholesterol-rich lipid raft microdomains serve to recruit and assemble other lipids and proteins to initiate signal transduction. There are two spatially and functionally distinct populations of the DAT segregated by cholesterol-rich lipid raft microdomains and cholesterol-scarce non-raft microdomains on the plasma membrane. These two DAT populations are differentially regulated by DAT blockers (e.g. cocaine), substrates (e.g. amphetamine), and protein kinase C providing distinct cholesterol-dependent modulation of dopamine uptake and efflux. In this chapter, we summarize the impact of depletion and addition of membrane cholesterol on DAT conformational changes between the outward-facing and the inward-facing states, lipid raft-associated DAT localization, basal and induced DAT internalization, and DAT function. In particular, we focus on how the interactions of the DAT with cocaine and amphetamine are influenced by membrane cholesterol. Lastly, we discuss the therapeutic potential of cholesterol-modifying drugs as a new avenue to normalize DAT function and dopamine transmission in patients with psychostimulant use disorder.
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Affiliation(s)
- Rong Chen
- Department of Physiology & Pharmacology, Wake Forest University School of Medicine, Winston Salem, NC, United States.
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9
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O'Brien TM. Acute eosinophilic pneumonia-like syndrome post-initiation of vortioxetine. BMJ Case Rep 2023; 16:e254254. [PMID: 37230747 PMCID: PMC10230916 DOI: 10.1136/bcr-2022-254254] [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] [Indexed: 05/27/2023] Open
Abstract
A man in his mid-30s presented to the emergency department with a 1-week history of fatigue, loss of appetite, fever and productive (yellow) cough. This progressed to requiring admission to intensive care needing a oxygen therapy via high-flow nasal cannula for acute hypoxaemic respiratory failure. He had recently started vortioxetine for major depressive disorder, and his acute symptoms correlated with an increase in the dose of vortioxetine. For more than 20 years, rare but consistent reports of serotonergic medications have been implicated in eosinophilic pulmonary conditions. During this same period, serotonergic medications have become a mainstay solution for a wide range of depressive symptoms and disorders. This is the first report of an eosinophilic pneumonia-like syndrome occurring while consuming the novel serotonergic medication vortioxetine.
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10
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Frangos ZJ, Wilson KA, Aitken HM, Cantwell Chater R, Vandenberg RJ, O'Mara ML. Membrane cholesterol regulates inhibition and substrate transport by the glycine transporter, GlyT2. Life Sci Alliance 2023; 6:e202201708. [PMID: 36690444 PMCID: PMC9873984 DOI: 10.26508/lsa.202201708] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/25/2023] Open
Abstract
Membrane cholesterol binds to and modulates the function of various SLC6 neurotransmitter transporters, including stabilizing the outward-facing conformation of the dopamine and serotonin transporters. Here, we investigate how cholesterol binds to GlyT2 (SLC6A5), modulates glycine transport rate, and influences bioactive lipid inhibition of GlyT2. Bioactive lipid inhibitors are analgesics that bind to an allosteric site accessible from the extracellular solution when GlyT2 adopts an outward-facing conformation. Using molecular dynamics simulations, mutagenesis, and cholesterol depletion experiments, we show that bioactive lipid inhibition of glycine transport is modulated by the recruitment of membrane cholesterol to a binding site formed by transmembrane helices 1, 5, and 7. Recruitment involves cholesterol flipping from its membrane orientation, and insertion of the 3' hydroxyl group into the cholesterol binding cavity, close to the allosteric site. The synergy between cholesterol and allosteric inhibitors provides a novel mechanism of inhibition and a potential avenue for the development of potent GlyT2 inhibitors as alternative therapeutics for the treatment of neuropathic pain and therapeutics that target other SLC6 transporters.
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Affiliation(s)
- Zachary J Frangos
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Katie A Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
| | - Heather M Aitken
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
| | - Ryan Cantwell Chater
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Robert J Vandenberg
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
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11
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Chan MC, Procko E, Shukla D. Structural Rearrangement of the Serotonin Transporter Intracellular Gate Induced by Thr276 Phosphorylation. ACS Chem Neurosci 2022; 13:933-945. [PMID: 35258286 DOI: 10.1021/acschemneuro.1c00714] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The reuptake of the neurotransmitter serotonin from the synaptic cleft by the serotonin transporter, SERT, is essential for proper neurological signaling. Biochemical studies have shown that Thr276 of transmembrane helix 5 is a site of PKG-mediated SERT phosphorylation, which has been proposed to shift the SERT conformational equilibria to promote inward-facing states, thus enhancing 5-HT transport. Recent structural and simulation studies have provided insights into the conformation transitions during substrate transport but have not shed light on SERT regulation via post-translational modifications. Using molecular dynamics simulations and Markov state models, we investigate how Thr276 phosphorylation impacts the SERT mechanism and its role in enhancing transporter stability and function. Our simulations show that Thr276 phosphorylation alters the hydrogen-bonding network involving residues on transmembrane helix 5. This in turn decreases the free energy barriers for SERT to transition to the inward-facing state, thus facilitating 5-HT import. The results provide atomistic insights into in vivo SERT regulation and can be extended to other pharmacologically important transporters in the solute carrier family.
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Affiliation(s)
- Matthew C. Chan
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Erik Procko
- Department of Biochemistry, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Neuroscience Program, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Cancer Center at Illinois, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Cancer Center at Illinois, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- National Center for Supercomputing Applications, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
- Department of Bioengineering, University of Illinois Urbana−Champaign, Urbana, Illinois 61801, United States
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12
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Chan MC, Selvam B, Young HJ, Procko E, Shukla D. The substrate import mechanism of the human serotonin transporter. Biophys J 2022; 121:715-730. [PMID: 35114149 PMCID: PMC8943754 DOI: 10.1016/j.bpj.2022.01.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/18/2021] [Accepted: 01/25/2022] [Indexed: 11/17/2022] Open
Abstract
The serotonin transporter (SERT) initiates the reuptake of extracellular serotonin in the synapse to terminate neurotransmission. The cryogenic electron microscopy structures of SERT bound to ibogaine and the physiological substrate serotonin resolved in different states have provided a glimpse of the functional conformations at atomistic resolution. However, the conformational dynamics and structural transitions to intermediate states are not fully understood. Furthermore, the molecular basis of how serotonin is recognized and transported remains unclear. In this study, we performed unbiased microsecond-long simulations of the human SERT to investigate the structural dynamics to various intermediate states and elucidated the complete substrate import pathway. Using Markov state models, we characterized a sequential order of conformational-driven ion-coupled substrate binding and transport events and calculated the free energy barriers of conformation transitions associated with the import mechanism. We find that the transition from the occluded to inward-facing state is the rate-limiting step for substrate import and that the substrate decreases the free energy barriers to achieve the inward-facing state. Our study provides insights on the molecular basis of dynamics-driven ion-substrate recognition and transport of SERT that can serve as a model for other closely related neurotransmitter transporters.
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Affiliation(s)
- Matthew C Chan
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Balaji Selvam
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Heather J Young
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Erik Procko
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois; Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois; National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, Illinois; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois; NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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13
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Frangos ZJ, Cantwell Chater RP, Vandenberg RJ. Glycine Transporter 2: Mechanism and Allosteric Modulation. Front Mol Biosci 2021; 8:734427. [PMID: 34805268 PMCID: PMC8602798 DOI: 10.3389/fmolb.2021.734427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/25/2021] [Indexed: 01/19/2023] Open
Abstract
Neurotransmitter sodium symporters (NSS) are a subfamily of SLC6 transporters responsible for regulating neurotransmitter signalling. They are a major target for psychoactive substances including antidepressants and drugs of abuse, prompting substantial research into their modulation and structure-function dynamics. Recently, a series of allosteric transport inhibitors have been identified, which may reduce side effect profiles, compared to orthosteric inhibitors. Allosteric inhibitors are also likely to provide different clearance kinetics compared to competitive inhibitors and potentially better clinical outcomes. Crystal structures and homology models have identified several allosteric modulatory sites on NSS including the vestibule allosteric site (VAS), lipid allosteric site (LAS) and cholesterol binding site (CHOL1). Whilst the architecture of eukaryotic NSS is generally well conserved there are differences in regions that form the VAS, LAS, and CHOL1. Here, we describe ligand-protein interactions that stabilize binding in each allosteric site and explore how differences between transporters could be exploited to generate NSS specific compounds with an emphasis on GlyT2 modulation.
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Affiliation(s)
- Zachary J Frangos
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Ryan P Cantwell Chater
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Robert J Vandenberg
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
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14
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Insights into the Role of Membrane Lipids in the Structure, Function and Regulation of Integral Membrane Proteins. Int J Mol Sci 2021; 22:ijms22169026. [PMID: 34445730 PMCID: PMC8396450 DOI: 10.3390/ijms22169026] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/15/2021] [Accepted: 08/17/2021] [Indexed: 02/07/2023] Open
Abstract
Membrane proteins exist within the highly hydrophobic membranes surrounding cells and organelles, playing key roles in cellular function. It is becoming increasingly clear that the membrane does not just act as an appropriate environment for these proteins, but that the lipids that make up these membranes are essential for membrane protein structure and function. Recent technological advances in cryogenic electron microscopy and in advanced mass spectrometry methods, as well as the development of alternative membrane mimetic systems, have allowed experimental study of membrane protein–lipid complexes. These have been complemented by computational approaches, exploiting the ability of Molecular Dynamics simulations to allow exploration of membrane protein conformational changes in membranes with a defined lipid content. These studies have revealed the importance of lipids in stabilising the oligomeric forms of membrane proteins, mediating protein–protein interactions, maintaining a specific conformational state of a membrane protein and activity. Here we review some of the key recent advances in the field of membrane protein–lipid studies, with major emphasis on respiratory complexes, transporters, channels and G-protein coupled receptors.
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15
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Ernst M, Robertson JL. The Role of the Membrane in Transporter Folding and Activity. J Mol Biol 2021; 433:167103. [PMID: 34139219 PMCID: PMC8756397 DOI: 10.1016/j.jmb.2021.167103] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022]
Abstract
The synthesis, folding, and function of membrane transport proteins are critical factors for defining cellular physiology. Since the stability of these proteins evolved amidst the lipid bilayer, it is no surprise that we are finding that many of these membrane proteins demonstrate coupling of their structure or activity in some way to the membrane. More and more transporter structures are being determined with some information about the surrounding membrane, and computational modeling is providing further molecular details about these solvation structures. Thus, the field is moving towards identifying which molecular mechanisms - lipid interactions, membrane perturbations, differential solvation, and bulk membrane effects - are involved in linking membrane energetics to transporter stability and function. In this review, we present an overview of these mechanisms and the growing evidence that the lipid bilayer is a major determinant of the fold, form, and function of membrane transport proteins in membranes.
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Affiliation(s)
- Melanie Ernst
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. Louis, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Janice L Robertson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine in St. Louis, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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16
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Wilson KA, Wang L, Lin YC, O'Mara ML. Investigating the lipid fingerprint of SLC6 neurotransmitter transporters: a comparison of dDAT, hDAT, hSERT, and GlyT2. BBA ADVANCES 2021; 1:100010. [PMID: 37082011 PMCID: PMC10074915 DOI: 10.1016/j.bbadva.2021.100010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The local lipid annulus, or "fingerprint", of four SLC6 transporters (dDAT, hDAT, hSERT, and GlyT2) embedded in a complex neuronal membrane were compared and characterised using molecular dynamics. Our analysis included the development of new tools to improve membrane leaflet detection and the analysis of leaflet-dependent properties. Overall, the lipid fingerprints of the four transporters are comprised of similar lipids when grouped by headgroup or tail saturation. The enrichment and depletion of specific lipids, including sites of cholesterol contacts, varies between transporters. The subtle differences in lipid fingerprints results in varying membrane biophysical properties near the transporter. Our results highlight that the lipid-fingerprint of SLC6 transporters in complex membranes is highly dependent on membrane composition. Our results further characterize how the presence and identity of membrane proteins affects the complex interplay of lipid-protein interactions, influencing the local lipid environment and membrane biophysical properties.
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17
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Calik I, Yayla M, Cinar I, Cadirci E, Albayrak A, Sirin B, Calik M, Halici Z. LP44 (4-[2-(methylthio)phenyl]-N-(1,2,3,4-tetrahydronaphthalen-1-yl)-1-piperazinehexanamide) exerts anti-ulcer effects via 5-hydroxytryptamine receptor 7 activation on indomethacin-induced gastric ulcers in rats. Inflammopharmacology 2020; 28:893-902. [PMID: 32504222 DOI: 10.1007/s10787-020-00725-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 05/20/2020] [Indexed: 10/24/2022]
Abstract
AIM This study aimed to demonstrate the role of serotonin 7 receptor (5-HT7) and the effects of 5-HT7 agonists and antagonists in an indomethacin-induced gastric ulcer. MATERIAL AND METHOD Male albino Wistar rats (n = 60) were used in the experiments. LP44 (5-HT7 agonist) and SB269970 (5-HT7 antagonist) were administered at 10 mg/kg as a pre-treatment. One hour after the drug treatments, 25 mg/kg of indomethacin (INDO) was administered to all groups except the healthy control group. Six hours after indomethacin administration, all the rats were euthanized. RESULTS We analyzed the iNOS, eNOS, and 5-HT7 receptor mRNA levels in the stomach tissue of rats by real-time PCR. 5-HT7 mRNA expression was increased in the INDO group compared to the healthy group. LP44 administration exerted a significant upregulatory effect on eNOS mRNA expression and downregulatory effects on iNOS and 5-HT7 mRNA expression compared to the INDO group. However, antagonist (SB269970) administration did not result in such difference in gene expression, but even partially decreased the agonist's effect in combination. Famotidine and agonist exerted similar effects. Histopathological findings supported the beneficial effects of 5-HT7 agonist on gastric tissue. CONCLUSION The study suggested that activation of 5-HT7 receptor showed a significant anti-ulcerogenic effect in the indomethacin-induced gastric ulcer model.
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Affiliation(s)
- Ilknur Calik
- Department of Pathology, Faculty of Medicine, Firat University, 23119, Elazıg, Turkey
| | - Muhammed Yayla
- Department of Pharmacology, Faculty of Medicine, Kafkas University, 36180, Kars, Turkey
| | - Irfan Cinar
- Department of Pharmacology, Faculty of Medicine, Kafkas University, 36180, Kars, Turkey
| | - Elif Cadirci
- Department of Pharmacology, Faculty of Medicine, Ataturk University, 25240, Erzurum, Turkey.,Clinical Research, Development and Design Application and Research Center, Ataturk University, 5240, Erzurum, Turkey
| | - Abdulmecit Albayrak
- Department of Pharmacology, Faculty of Medicine, Ataturk University, 25240, Erzurum, Turkey
| | - Busra Sirin
- Department of Pharmacology, Faculty of Medicine, Ataturk University, 25240, Erzurum, Turkey
| | - Muhammet Calik
- Department of Pathology, Faculty of Medicine, Firat University, 23119, Elazıg, Turkey
| | - Zekai Halici
- Department of Pharmacology, Faculty of Medicine, Ataturk University, 25240, Erzurum, Turkey. .,Clinical Research, Development and Design Application and Research Center, Ataturk University, 5240, Erzurum, Turkey.
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18
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Xiao QY, Fang XC, Li XQ, Fei GJ. Ethnic differences in genetic polymorphism associated with irritable bowel syndrome. World J Gastroenterol 2020; 26:2049-2063. [PMID: 32536774 PMCID: PMC7267697 DOI: 10.3748/wjg.v26.i17.2049] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/25/2020] [Accepted: 04/04/2020] [Indexed: 02/06/2023] Open
Abstract
Genetic polymorphism is associated with irritable bowel syndrome (IBS) in terms of susceptibility and clinical manifestations. Previous studies have shown that genetic polymorphism might play a key role in the onset and progression of IBS by modulating components of its pathogenesis such as the gut-brain axis, gastrointestinal motility, inflammatory activity, and immune status. Although underlying pathophysiological mechanisms have not been fully clarified, the potential ethnic differences that are present in worldwide genetic studies of IBS deserve attention. This review surveyed numerous studies focusing on IBS-associated single nucleotide polymorphisms, and investigated the ethnic disparities revealed by them. The results demonstrate the need for more attention on ethnic factors in IBS-related genetic studies. Taking ethnic backgrounds into accounts and placing emphasis on disparities potentially ascribed to ethnicity could help lay a solid and generalized foundation for transcultural, multi-ethnic, or secondary analyses in IBS, for example, a meta-analysis. Broader genetic studies considering ethnic factors are greatly needed to obtain a better understanding of the pathophysiological mechanisms of IBS and to improve the prevention, intervention, and treatment of this disease.
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Affiliation(s)
- Qi-Yun Xiao
- Department of Gastroenterology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
| | - Xiu-Cai Fang
- Department of Gastroenterology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
| | - Xiao-Qing Li
- Department of Gastroenterology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
| | - Gui-Jun Fei
- Department of Gastroenterology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
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19
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Hellsberg E, Ecker GF, Stary-Weinzinger A, Forrest LR. A structural model of the human serotonin transporter in an outward-occluded state. PLoS One 2019; 14:e0217377. [PMID: 31251747 PMCID: PMC6599148 DOI: 10.1371/journal.pone.0217377] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 06/17/2019] [Indexed: 12/12/2022] Open
Abstract
The human serotonin transporter hSERT facilitates the reuptake of its endogenous substrate serotonin from the synaptic cleft into presynaptic neurons after signaling. Reuptake regulates the availability of this neurotransmitter and therefore hSERT plays an important role in balancing human mood conditions. In 2016, the first 3D structures of this membrane transporter were reported in an inhibitor-bound, outward-open conformation. These structures revealed valuable information about interactions of hSERT with antidepressant drugs. Nevertheless, the question remains how serotonin facilitates the specific conformational changes that open and close pathways from the synapse and to the cytoplasm as required for transport. Here, we present a serotonin-bound homology model of hSERT in an outward-occluded state, a key intermediate in the physiological cycle, in which the interactions with the substrate are likely to be optimal. Our approach uses two template structures and includes careful refinement and comprehensive computational validation. According to microsecond-long molecular dynamics simulations, this model exhibits interactions between the gating residues in the extracellular pathway, and these interactions differ from those in an outward-open conformation of hSERT bound to serotonin. Moreover, we predict several features of this state by monitoring the intracellular gating residues, the extent of hydration, and, most importantly, protein-ligand interactions in the central binding site. The results illustrate common and distinct characteristics of these two transporter states and provide a starting point for future investigations of the transport mechanism in hSERT.
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Affiliation(s)
- Eva Hellsberg
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Gerhard F. Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | | | - Lucy R. Forrest
- Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, United States of America
- * E-mail:
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20
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Corradi V, Sejdiu BI, Mesa-Galloso H, Abdizadeh H, Noskov SY, Marrink SJ, Tieleman DP. Emerging Diversity in Lipid-Protein Interactions. Chem Rev 2019; 119:5775-5848. [PMID: 30758191 PMCID: PMC6509647 DOI: 10.1021/acs.chemrev.8b00451] [Citation(s) in RCA: 260] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Indexed: 02/07/2023]
Abstract
Membrane lipids interact with proteins in a variety of ways, ranging from providing a stable membrane environment for proteins to being embedded in to detailed roles in complicated and well-regulated protein functions. Experimental and computational advances are converging in a rapidly expanding research area of lipid-protein interactions. Experimentally, the database of high-resolution membrane protein structures is growing, as are capabilities to identify the complex lipid composition of different membranes, to probe the challenging time and length scales of lipid-protein interactions, and to link lipid-protein interactions to protein function in a variety of proteins. Computationally, more accurate membrane models and more powerful computers now enable a detailed look at lipid-protein interactions and increasing overlap with experimental observations for validation and joint interpretation of simulation and experiment. Here we review papers that use computational approaches to study detailed lipid-protein interactions, together with brief experimental and physiological contexts, aiming at comprehensive coverage of simulation papers in the last five years. Overall, a complex picture of lipid-protein interactions emerges, through a range of mechanisms including modulation of the physical properties of the lipid environment, detailed chemical interactions between lipids and proteins, and key functional roles of very specific lipids binding to well-defined binding sites on proteins. Computationally, despite important limitations, molecular dynamics simulations with current computer power and theoretical models are now in an excellent position to answer detailed questions about lipid-protein interactions.
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Affiliation(s)
- Valentina Corradi
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Besian I. Sejdiu
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Haydee Mesa-Galloso
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Haleh Abdizadeh
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Sergei Yu. Noskov
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Siewert J. Marrink
- Groningen
Biomolecular Sciences and Biotechnology Institute and Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - D. Peter Tieleman
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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21
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Substrate and inhibitor binding to the serotonin transporter: Insights from computational, crystallographic, and functional studies. Neuropharmacology 2019; 161:107548. [PMID: 30807752 DOI: 10.1016/j.neuropharm.2019.02.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/19/2019] [Accepted: 02/22/2019] [Indexed: 02/02/2023]
Abstract
The serotonin transporter (SERT) belongs to the monoamine transporter family, which also includes the dopamine and norepinephrine transporters. SERT is essential for regulating serotonergic signaling by the reuptake of serotonin from the synaptic cleft back into the presynaptic neuron. Dysregulation of SERT has been implicated in several major psychiatric disorders such as major depressive disorder (MDD). MDD was among the top five leading causes of years lived with disease in 2016 and is characterized as a major global burden. Several drugs have been developed to target SERT for use in the treatment of MDD, and their respective binding modes and locations within SERT have been studied. The elucidation of the first structure of a bacterial SERT homologue in 2005 has accelerated crystallographic, computational, and functional studies to further elucidate drug binding and method of action in SERT. Herein, we aim to highlight and compare these studies with an emphasis on what the different experimental methods conclude on substrate and inhibitor binding modes, and the potential caveats of using the different types of studies are discussed. We focus this review on the binding of cognate substrate and drugs belonging to the different families of antidepressants, including tricyclic antidepressants, selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and multimodal drugs, as well as illicit drugs such as cocaine, amphetamines, and ibogaine. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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22
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Bailey DM, Catron MA, Kovtun O, Macdonald RL, Zhang Q, Rosenthal SJ. Single Quantum Dot Tracking Reveals Serotonin Transporter Diffusion Dynamics are Correlated with Cholesterol-Sensitive Threonine 276 Phosphorylation Status in Primary Midbrain Neurons. ACS Chem Neurosci 2018; 9:2534-2541. [PMID: 29787674 DOI: 10.1021/acschemneuro.8b00214] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Serotonin transporter (SERT) terminates serotonin signaling in the brain by enabling rapid clearance of the neurotransmitter. SERT dysfunction has been associated with a variety of psychiatric disorders, including depression, anxiety, and autism. Visualizing SERT behavior at the single molecule level in endogenous systems remains a challenge. In this study, we utilize quantum dot (QD) single particle tracking (SPT) to capture SERT dynamics in primary rat midbrain neurons. Membrane microenvironment, specifically membrane cholesterol, plays a key role in SERT regulation and has been found to affect SERT conformational state. We sought to determine how reduced cholesterol content affects both lateral mobility and phosphorylation of conformationally sensitive threonine 276 (Thr276) in endogenous SERT using two different methods of cholesterol manipulation, statins and methyl-β-cyclodextrin. Both chronic and acute cholesterol depletion increased SERT lateral diffusion, radial displacement along the membrane, mobile fraction, and Thr276 phosphorylation levels. Overall, this work has provided new insights about endogenous neuronal SERT mobility and its associations with membrane cholesterol and SERT phosphorylation status.
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23
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Morissette M, Morin N, Rouillard C, Di Paolo T. Membrane cholesterol removal and replenishment affect rat and monkey brain monoamine transporters. Neuropharmacology 2018; 133:289-306. [PMID: 29407218 DOI: 10.1016/j.neuropharm.2018.01.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/10/2018] [Accepted: 01/25/2018] [Indexed: 12/16/2022]
Abstract
The dopamine transporter (DAT) is abundantly expressed in the striatum where it removes extracellular dopamine into the cytosol of presynaptic nerve terminals. It is the target of drugs of abuse and antidepressants. There is a loss of the DAT in Parkinson's disease affecting release of levodopa implicated in levodopa-induced dyskinesias. This study investigated the effect of cholesterol on DAT, serotonin transporter (SERT) and vesicular monoamine transporter 2 (VMAT2) in monkey and rat brains in vitro. DAT protein levels measured by Western blot remained unchanged with in vitro methyl-β-cyclodextrin (MCD) incubations to remove membrane cholesterol or with incubations to increase membrane cholesterol content. By contrast, striatal DAT specific binding labelled with [125I]RTI-121 or with [125I]RTI-55 decreased with increasing concentrations of MCD and increased with cholesterol loading. Moreover, [125I]RTI-121 specific binding of striatal membranes depleted of cholesterol with MCD was restored to initial DAT content with addition of cholesterol showing its rapid and reversible effect. By contrast, striatal VMAT2 and SERT specific binding showed no or limited changes by cholesterol manipulations. Similar results were obtained for monkey caudate nucleus, putamen and nucleus accumbens. Membrane microviscosity was assessed by fluorescence polarization spectroscopy, using the probe 1,6-diphenyl-1,3,5-hexatriene. DAT changes positively correlated with changes of membrane microviscosity in rat and monkey brain regions investigated and with membrane cholesterol contents. Similar findings were observed with desmosterol but to a lower extent than with cholesterol. These results show an important effect of cholesterol on the DAT associated with microviscosity changes that should be considered in drug therapies.
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Affiliation(s)
- Marc Morissette
- Neuroscience Research Unit, Centre Hospitalier Universitaire de Québec, CHUL, Quebec City G1V 4G2, Canada
| | - Nicolas Morin
- Neuroscience Research Unit, Centre Hospitalier Universitaire de Québec, CHUL, Quebec City G1V 4G2, Canada; Faculty of Pharmacy, Université Laval, Quebec City G1K 7P4, Canada
| | - Claude Rouillard
- Neuroscience Research Unit, Centre Hospitalier Universitaire de Québec, CHUL, Quebec City G1V 4G2, Canada; Department of Psychiatry and Neuroscience, Faculty of Medicine, Université Laval, Quebec City G1K 7P4, Canada
| | - Thérèse Di Paolo
- Neuroscience Research Unit, Centre Hospitalier Universitaire de Québec, CHUL, Quebec City G1V 4G2, Canada; Faculty of Pharmacy, Université Laval, Quebec City G1K 7P4, Canada.
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24
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Cao YN, Feng LJ, Liu YY, Jiang K, Zhang MJ, Gu YX, Wang BM, Gao J, Wang ZL, Wang YM. Effect of Lactobacillus rhamnosus GG supernatant on serotonin transporter expression in rats with post-infectious irritable bowel syndrome. World J Gastroenterol 2018; 24:338-350. [PMID: 29391756 PMCID: PMC5776395 DOI: 10.3748/wjg.v24.i3.338] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 12/06/2017] [Accepted: 12/12/2017] [Indexed: 02/06/2023] Open
Abstract
AIM To evaluate the effect of Lactobacillus rhamnosus GG supernatant (LGG-s) on the expression of serotonin transporter (SERT) in rats with post-infectious irritable bowel syndrome (PI-IBS).
METHODS Campylobacter jejuni 81-176 (1010 CFU/mL) was used to induce intestinal infection to develop a PI-IBS model. After evaluation of the post-infectious phase by biochemical tests, DNA agarose gel electrophoresis, abdominal withdrawal reflex (AWR) test, and the intestinal motility test, four PI-IBS groups received different concentrations of LGG-s for 4 wk. The treatments were maintained for 1.0, 2.0, 3.0 or 4.0 wk during the experiment, and the colons and brains were removed for later use each week. SERT mRNA and protein levels were detected by real-time PCR and Western blot, respectively.
RESULTS The levels of SERT mRNA and protein in intestinal tissue were higher in rats treated with LGG-s than in control rats and PI-IBS rats gavaged with PBS during the whole study. Undiluted LGG-s up-regulated SERT mRNA level by 2.67 times compared with the control group by week 2, and SERT mRNA expression kept increasing later. Double-diluted LGG-s was similar to undiluted-LGG-s, resulting in high levels of SERT mRNA. Triple-diluted LGG-s up-regulated SERT mRNA expression level by 6.9-times compared with the control group, but SERT mRNA expression decreased rapidly at the end of the second week. At the first week, SERT protein levels were basically comparable in rats treated with undiluted LGG-s, double-diluted LGG-s, and triple-diluted LGG-s, which were higher than those in the control group and PBS-treated PI-IBS group. SERT protein levels in the intestine were also comparable in rats treated with undiluted LGG-s, double-diluted LGG-s, and triple-diluted LGG-s by the second and third weeks. SERT mRNA and protein levels in the brain had no statistical difference in the groups during the experiment.
CONCLUSION LGG-s can up-regulate SERT mRNA and protein levels in intestinal tissue but has no influence in brain tissue in rats with PI-IBS.
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Affiliation(s)
- Ya-Nan Cao
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Li-Juan Feng
- Department of Functional Division, Xingtai People’s Hospital, Xingtai 054031, Hebei Province, China
| | - Yuan-Yuan Liu
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Kui Jiang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Mao-Jun Zhang
- National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China
| | - Yi-Xin Gu
- National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China
| | - Bang-Mao Wang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Jia Gao
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Ze-Lan Wang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
| | - Yu-Ming Wang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin 300052, China
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25
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Laursen L, Severinsen K, Kristensen KB, Periole X, Overby M, Müller HK, Schiøtt B, Sinning S. Cholesterol binding to a conserved site modulates the conformation, pharmacology, and transport kinetics of the human serotonin transporter. J Biol Chem 2018; 293:3510-3523. [PMID: 29352106 DOI: 10.1074/jbc.m117.809046] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 01/14/2018] [Indexed: 12/31/2022] Open
Abstract
The serotonin transporter (SERT) is important for reuptake of the neurotransmitter serotonin from the synaptic cleft and is also the target of most antidepressants. It has previously been shown that cholesterol in the membrane bilayer affects the conformation of SERT. Although recent crystal structures have identified several potential cholesterol-binding sites, it is unclear whether any of these potential cholesterol sites are occupied by cholesterol and functionally relevant. In the present study, we focus on the conserved cholesterol site 1 (CHOL1) located in a hydrophobic groove between TM1a, TM5, and TM7. By molecular dynamics simulations, we demonstrate a strong binding of cholesterol to CHOL1 in a membrane bilayer environment. In biochemical experiments, we find that cholesterol depletion induces a more inward-facing conformation favoring substrate analog binding. Consistent with this, we find that mutations in CHOL1 with a negative impact on cholesterol binding induce a more inward-facing conformation, and, vice versa, mutations with a positive impact on cholesterol binding induce a more outward-facing conformation. This shift in transporter conformation dictated by the ability to bind cholesterol in CHOL1 affects the apparent substrate affinity, maximum transport velocity, and turnover rates. Taken together, we show that occupation of CHOL1 by cholesterol is of major importance in the transporter conformational equilibrium, which in turn dictates ligand potency and serotonin transport activity. Based on our findings, we propose a mechanistic model that incorporates the role of cholesterol binding to CHOL1 in the function of SERT.
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Affiliation(s)
- Louise Laursen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Kasper Severinsen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Kristina Birch Kristensen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Xavier Periole
- the Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Malene Overby
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Heidi Kaastrup Müller
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Birgit Schiøtt
- the Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Steffen Sinning
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
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Zeppelin T, Ladefoged LK, Sinning S, Periole X, Schiøtt B. A direct interaction of cholesterol with the dopamine transporter prevents its out-to-inward transition. PLoS Comput Biol 2018; 14:e1005907. [PMID: 29329285 PMCID: PMC5811071 DOI: 10.1371/journal.pcbi.1005907] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 02/13/2018] [Accepted: 11/29/2017] [Indexed: 01/30/2023] Open
Abstract
Monoamine transporters (MATs) carry out neurotransmitter reuptake from the synaptic cleft, a key step in neurotransmission, which is targeted in the treatment of neurological disorders. Cholesterol (CHOL), a major component of the synaptic plasma membrane, has been shown to exhibit a modulatory effect on MATs. Recent crystal structures of the dopamine transporter (DAT) revealed the presence of two conserved CHOL-like molecules, suggesting a functional protein-CHOL direct interaction. Here, we present extensive atomistic molecular dynamics (MD) simulations of DAT in an outward-facing conformation. In the absence of bound CHOL, DAT undergoes structural changes reflecting early events of dopamine transport: transition to an inward-facing conformation. In contrast, in the presence of bound CHOL, these conformational changes are inhibited, seemingly by an immobilization of the intracellular interface of transmembrane helix 1a and 5 by CHOL. We also provide evidence, from coarse grain MD simulations that the CHOL sites observed in the DAT crystal structures are preserved in all human monoamine transporters (dopamine, serotonin and norepinephrine), suggesting that our findings might extend to the entire family.
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Affiliation(s)
- Talia Zeppelin
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Lucy Kate Ladefoged
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark
| | - Steffen Sinning
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark
| | - Xavier Periole
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark
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27
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Modulation of LAT1 (SLC7A5) transporter activity and stability by membrane cholesterol. Sci Rep 2017; 7:43580. [PMID: 28272458 PMCID: PMC5341093 DOI: 10.1038/srep43580] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/25/2017] [Indexed: 11/17/2022] Open
Abstract
LAT1 (SLC7A5) is a transporter for both the uptake of large neutral amino acids and a number of pharmaceutical drugs. It is expressed in numerous cell types including T-cells, cancer cells and brain endothelial cells. However, mechanistic knowledge of how it functions and its interactions with lipids are unknown or limited due to inability of obtaining stable purified protein in sufficient quantities. Our data show that depleting cellular cholesterol reduced the Vmax but not the Km of the LAT1 mediated uptake of a model substrate into cells (L-DOPA). A soluble cholesterol analogue was required for the stable purification of the LAT1 with its chaperon CD98 (4F2hc,SLC3A2) and that this stabilised complex retained the ability to interact with a substrate. We propose cholesterol interacts with the conserved regions in the LAT1 transporter that have been shown to bind to cholesterol/CHS in Drosophila melanogaster dopamine transporter. In conclusion, LAT1 is modulated by cholesterol impacting on its stability and transporter activity. This novel finding has implications for other SLC7 family members and additional eukaryotic transporters that contain the LeuT fold.
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28
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Ferraro M, Masetti M, Recanatini M, Cavalli A, Bottegoni G. Mapping Cholesterol Interaction Sites on Serotonin Transporter through Coarse-Grained Molecular Dynamics. PLoS One 2016; 11:e0166196. [PMID: 27907003 PMCID: PMC5132266 DOI: 10.1371/journal.pone.0166196] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 10/24/2016] [Indexed: 12/19/2022] Open
Abstract
Serotonin transporter (SERT) modulates serotonergic signaling via re-uptake of serotonin in pre-synaptic cells. The inclusion in cholesterol-enriched membrane domains is crucial for SERT activity, suggesting a cross-talk between the protein and the sterol. Here, we develop a protocol to identify potential cholesterol interaction sites coupling statistical analysis to multi-microsecond coarse-grained molecular dynamics simulations of SERT in a previously validated raft-like membrane model. Six putative sites were found, including a putative CRAC motif on TM4 and a CARC motif on TM10. Among them, four hot-spots near regions related to ion binding, transport, and inhibition were detected. Our results encourage prospective studies to unravel mechanistic features of the transporter and related drug discovery implications.
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Affiliation(s)
| | - Matteo Masetti
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum - Università di Bologna, Bologna, Italy
- * E-mail: (MM); (GB)
| | - Maurizio Recanatini
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Andrea Cavalli
- CompuNet, Istituto Italiano di Tecnologia, Genova, Italy
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum - Università di Bologna, Bologna, Italy
| | - Giovanni Bottegoni
- CompuNet, Istituto Italiano di Tecnologia, Genova, Italy
- BiKi Technologies s.r.l., Genova, Italy
- * E-mail: (MM); (GB)
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29
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Jin DC, Cao HL, Xu MQ, Wang SN, Wang YM, Yan F, Wang BM. Regulation of the serotonin transporter in the pathogenesis of irritable bowel syndrome. World J Gastroenterol 2016; 22:8137-8148. [PMID: 27688655 PMCID: PMC5037082 DOI: 10.3748/wjg.v22.i36.8137] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 05/28/2016] [Accepted: 06/15/2016] [Indexed: 02/06/2023] Open
Abstract
Serotonin (5-HT) and the serotonin transporter (SERT) have earned a tremendous amount of attention regarding the pathogenesis of irritable bowel syndrome (IBS). Considering that enteric 5-HT is responsible for the secretion, motility and perception of the bowel, the involvement of altered enteric 5-HT metabolism in the pathogenesis of IBS has been elucidated. Higher 5-HT availability is commonly associated with depressed SERT mRNA in patients with IBS compared with healthy controls. The expression difference of SERT between IBS patients and healthy controls might suggest that SERT plays an essential role in IBS pathogenesis, and SERT was expected to be a novel therapeutic target for IBS. Progress in this area has begun to illuminate the complex regulatory mechanisms of SERT in the etiology of IBS. In this article, current insights regarding the regulation of SERT in IBS are provided, including aspects of SERT gene polymorphisms, microRNAs, immunity and inflammation, gut microbiota, growth factors, among others. Potential SERT-directed therapies for IBS are also described. The potential regulators of SERT are of clinical importance and are important for better understanding IBS pathophysiology and therapeutic strategies.
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30
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Bianchi F, Klooster JSV', Ruiz SJ, Luck K, Pols T, Urbatsch IL, Poolman B. Asymmetry in inward- and outward-affinity constant of transport explain unidirectional lysine flux in Saccharomyces cerevisiae. Sci Rep 2016; 6:31443. [PMID: 27550794 PMCID: PMC4993999 DOI: 10.1038/srep31443] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 07/20/2016] [Indexed: 02/01/2023] Open
Abstract
The import of basic amino acids in Saccharomyces cerevisiae has been reported to be unidirectional, which is not typical of how secondary transporters work. Since studies of energy coupling and transport kinetics are complicated in vivo, we purified the major lysine transporter (Lyp1) of yeast and reconstituted the protein into lipid vesicles. We show that the Michaelis constant (KM) of transport from out-to-in is well in the millimolar range and at least 3 to 4-orders of magnitude higher than that of transport in the opposite direction, disfavoring the efflux of solute via Lyp1. We also find that at low values of the proton motive force, the transport by Lyp1 is comparatively slow. We benchmarked the properties of eukaryotic Lyp1 to that of the prokaryotic homologue LysP and find that LysP has a similar KM for transport from in-to-out and out-to-in, consistent with rapid influx and efflux. We thus explain the previously described unidirectional nature of lysine transport in S. cerevisiae by the extraordinary kinetics of Lyp1 and provide a mechanism and rationale for previous observations. The high asymmetry in transport together with secondary storage in the vacuole allow the cell to accumulate basic amino acids to very high levels.
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Affiliation(s)
- Frans Bianchi
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Joury S van 't Klooster
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Stephanie J Ruiz
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Katja Luck
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Tjeerd Pols
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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