1
|
Dong F, Lojko P, Bazzone A, Bernhard F, Borodina I. Transporter function characterization via continuous-exchange cell-free synthesis and solid supported membrane-based electrophysiology. Bioelectrochemistry 2024; 159:108732. [PMID: 38810322 DOI: 10.1016/j.bioelechem.2024.108732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 05/02/2024] [Accepted: 05/13/2024] [Indexed: 05/31/2024]
Abstract
Functional characterization of transporters is impeded by the high cost and technical challenges of current transporter assays. Thus, in this work, we developed a new characterization workflow that combines cell-free protein synthesis (CFPS) and solid supported membrane-based electrophysiology (SSME). For this, membrane protein synthesis was accomplished in a continuous exchange cell-free system (CECF) in the presence of nanodiscs. The resulting transporters expressed in nanodiscs were incorporated into proteoliposomes and assayed in the presence of different substrates using the surface electrogenic event reader. As a proof of concept, we validated this workflow to express and characterize five diverse transporters: the drug/H+-coupled antiporters EmrE and SugE, the lactose permease LacY, the Na+/H+ antiporter NhaA from Escherichia coli, and the mitochondrial carrier AAC2 from Saccharomyces cerevisiae. For all transporters kinetic parameters, such as KM, IMAX, and pH dependency, were evaluated. This robust and expedite workflow (e.g., can be executed within only five workdays) offers a convenient direct functional assessment of transporter protein activity and has the ability to facilitate applications of transporters in medical and biotechnological research.
Collapse
Affiliation(s)
- Fang Dong
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | - Pawel Lojko
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | | | - Frank Bernhard
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Irina Borodina
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark.
| |
Collapse
|
2
|
Lucero RM, Demirer K, Yeh TJ, Stockbridge RB. Transport of metformin metabolites by guanidinium exporters of the small multidrug resistance family. J Gen Physiol 2024; 156:e202313464. [PMID: 38294434 PMCID: PMC10829512 DOI: 10.1085/jgp.202313464] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/01/2023] [Accepted: 01/04/2024] [Indexed: 02/01/2024] Open
Abstract
Proteins from the small multidrug resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in the metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid-supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMRGdx homologs. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMRGdx homologs, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homolog, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMRGdx homolog Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMRGdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.
Collapse
Affiliation(s)
- Rachael M. Lucero
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Kemal Demirer
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | | | - Randy B. Stockbridge
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Program in Biophysics, University of Michigan, Ann Arbor, MI, USA
| |
Collapse
|
3
|
Körner A, Bazzone A, Wichert M, Barthmes M, Dondapati SK, Fertig N, Kubick S. Unraveling the kinetics and pharmacology of human PepT1 using solid supported membrane-based electrophysiology. Bioelectrochemistry 2024; 155:108573. [PMID: 37748262 DOI: 10.1016/j.bioelechem.2023.108573] [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: 07/17/2023] [Revised: 09/14/2023] [Accepted: 09/15/2023] [Indexed: 09/27/2023]
Abstract
The human Peptide Transporter 1 (hPepT1) is known for its broad substrate specificity and its ability to transport (pro-)drugs. Here, we present an in-depth comprehensive study of hPepT1 and its interactions with various substrates via solid supported membrane-based electrophysiology (SSME). Using hPepT1-containing vesicles, we could not identify any peptide induced pre-steady-state currents, indicating that the recorded peak currents reflect steady-state transport. Electrogenic co-transport of H+/glycylglycine (GlyGly) was observed across a pH range of 5.0 to 9.0. The pH dependence is described by a bell-shaped activity curve and two pK values. KM and relative Vmax values of various canonical and non-canonical peptide substrates were contextualized with current mechanistic understandings of hPepT1. Finally, specific inhibition was observed for various inhibitors in a high throughput format, and IC50 values are reported. Taken together, these findings contribute to promoting the design and analysis of pharmacologically relevant substances.
Collapse
Affiliation(s)
- Alexander Körner
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; Institute of Biotechnology, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Andre Bazzone
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339 Munich, Germany
| | - Maximilian Wichert
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; Freie Universität Berlin, Institute of Chemistry and Biochemistry - Biochemistry, 14195 Berlin, Germany
| | - Maria Barthmes
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339 Munich, Germany
| | - Srujan Kumar Dondapati
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany.
| | - Niels Fertig
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339 Munich, Germany
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; Freie Universität Berlin, Institute of Chemistry and Biochemistry - Biochemistry, 14195 Berlin, Germany; Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus - Senftenberg, The Brandenburg Medical School Theodor Fontane and the University of Potsdam, Germany
| |
Collapse
|
4
|
Huang L, Cao B, Geng Y, Zhou X, Yang Y, Ma T, Lin H, Huang Z, Zhuo L, Li J. A randomized double-blind phase Ib clinical trial of SY-009 in patients with type 2 diabetes mellitus. Eur J Pharm Sci 2024; 192:106644. [PMID: 37981049 DOI: 10.1016/j.ejps.2023.106644] [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: 11/11/2022] [Revised: 10/18/2023] [Accepted: 11/16/2023] [Indexed: 11/21/2023]
Abstract
INTRODUCTION SY-009 produces a hypoglycemic effect via inhibiting sodium/glucose cotransporter 1 (SGLT1) in type 2 diabetes mellitus (T2DM) patients. This randomized, double-blind, placebo-controlled, and multiple-dose escalation clinical trial aimed to evaluate the pharmacokinetic and pharmacodynamical characteristics as well as the safety and tolerability of SY-009 in T2DM patients. METHOD Fifty T2DM patients were randomized into experimental and placebo groups, and hospitalized for 9 days managed with a unified diet and rest management. Subjects were given SY-009 or placebo from day 1 to day 7 at different frequencies and dosages. Single dose cohort was defined as the first dose on day 1 and multiple dose cohort included all the dose from day 1 to 7. Blood samples were collected for pharmacokinetic analysis. Mixed meal tolerance tests were performed. Blood samples were collected to determine glucose, C-peptide, insulin, glucagon-like peptide-1 (GLP-1), and gastric inhibitory polypeptide (GIP). RESULTS PK parameters were not obtained because blood SY-009 concentrations were below the limit of quantitation in all subjects. SY-009 decreased the postprandial glucose. Blood glucose was controlled within 4 hours after taking the drug. Short-term administration of SY-009 (7 days) had no significant effects on fasting glucose but reduced the secretion of C-peptide, insulin, and GIP and increased GLP-1 secretion. The most common adverse event was gastrointestinal disorder manifesting abdominal pain, diarrhea, and bloating. CONCLUSION Plasma exposure of SY-009 and its metabolites was fairly low in T2DM patients at doses of 1.0-4.0 mg. SY-009 reduced postprandial glucose, C-peptide, and insulin levels, showing relative safety and tolerability in the dose range of 1.0-4.0 mg. TRIALS REGISTRATION ClinicalTrials.gov Identifier: NCT04345107.
Collapse
Affiliation(s)
- Lei Huang
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Bei Cao
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Yan Geng
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Xiaoli Zhou
- Suzhou Yabao Pharmaceutical R&D Co., Ltd., Suzhou 215000, China
| | - Yuanxun Yang
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Tingting Ma
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Hui Lin
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China
| | - Zhijiang Huang
- Suzhou Yabao Pharmaceutical R&D Co., Ltd., Suzhou 215000, China
| | - Lang Zhuo
- Suzhou Yabao Pharmaceutical R&D Co., Ltd., Suzhou 215000, China.
| | - Juan Li
- Phase I Clinical Trials Unit, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, 210008, China.
| |
Collapse
|
5
|
Bazzone A, Barthmes M, George C, Brinkwirth N, Zerlotti R, Prinz V, Cole K, Friis S, Dickson A, Rice S, Lim J, Fern Toh M, Mohammadi M, Pau D, Stone DJ, Renger JJ, Fertig N. A Comparative Study on the Lysosomal Cation Channel TMEM175 Using Automated Whole-Cell Patch-Clamp, Lysosomal Patch-Clamp, and Solid Supported Membrane-Based Electrophysiology: Functional Characterization and High-Throughput Screening Assay Development. Int J Mol Sci 2023; 24:12788. [PMID: 37628970 PMCID: PMC10454728 DOI: 10.3390/ijms241612788] [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: 06/20/2023] [Revised: 08/09/2023] [Accepted: 08/12/2023] [Indexed: 08/27/2023] Open
Abstract
The lysosomal cation channel TMEM175 is a Parkinson's disease-related protein and a promising drug target. Unlike whole-cell automated patch-clamp (APC), lysosomal patch-clamp (LPC) facilitates physiological conditions, but is not yet suitable for high-throughput screening (HTS) applications. Here, we apply solid supported membrane-based electrophysiology (SSME), which enables both direct access to lysosomes and high-throughput electrophysiological recordings. In SSME, ion translocation mediated by TMEM175 is stimulated using a concentration gradient at a resting potential of 0 mV. The concentration-dependent K+ response exhibited an I/c curve with two distinct slopes, indicating the existence of two conducting states. We measured H+ fluxes with a permeability ratio of PH/PK = 48,500, which matches literature findings from patch-clamp studies, validating the SSME approach. Additionally, TMEM175 displayed a high pH dependence. Decreasing cytosolic pH inhibited both K+ and H+ conductivity of TMEM175. Conversely, lysosomal pH and pH gradients did not have major effects on TMEM175. Finally, we developed HTS assays for drug screening and evaluated tool compounds (4-AP, Zn as inhibitors; DCPIB, arachidonic acid, SC-79 as enhancers) using SSME and APC. Additionally, we recorded EC50 data for eight blinded TMEM175 enhancers and compared the results across all three assay technologies, including LPC, discussing their advantages and disadvantages.
Collapse
Affiliation(s)
- Andre Bazzone
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Maria Barthmes
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Cecilia George
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Nina Brinkwirth
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Rocco Zerlotti
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
- RIGeL-Regensburg International Graduate School of Life Sciences, University of Regensburg, 93053 Regensburg, Germany
| | - Valentin Prinz
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Kim Cole
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Søren Friis
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| | - Alexander Dickson
- SB Drug Discovery, West of Scotland Science Park, Glasgow G20 0XA, UK; (A.D.); (S.R.)
| | - Simon Rice
- SB Drug Discovery, West of Scotland Science Park, Glasgow G20 0XA, UK; (A.D.); (S.R.)
| | - Jongwon Lim
- Cerevel Therapeutics, 222 Jacobs St, Cambridge, MA 02141, USA; (J.L.); (M.F.T.); (D.J.S.); (J.J.R.)
| | - May Fern Toh
- Cerevel Therapeutics, 222 Jacobs St, Cambridge, MA 02141, USA; (J.L.); (M.F.T.); (D.J.S.); (J.J.R.)
| | | | - Davide Pau
- SB Drug Discovery, West of Scotland Science Park, Glasgow G20 0XA, UK; (A.D.); (S.R.)
| | - David J. Stone
- Cerevel Therapeutics, 222 Jacobs St, Cambridge, MA 02141, USA; (J.L.); (M.F.T.); (D.J.S.); (J.J.R.)
| | - John J. Renger
- Cerevel Therapeutics, 222 Jacobs St, Cambridge, MA 02141, USA; (J.L.); (M.F.T.); (D.J.S.); (J.J.R.)
| | - Niels Fertig
- Nanion Technologies, Ganghoferstr. 70a, 80339 Munich, Germany (V.P.); (S.F.)
| |
Collapse
|
6
|
Pandey Y, Dondapati SK, Kubick S. Enriched cell-free and cell-based native membrane derived vesicles (nMV) enabling rapid in-vitro electrophysiological analysis of the voltage-gated sodium channel 1.5. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184144. [PMID: 36889502 DOI: 10.1016/j.bbamem.2023.184144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/10/2023] [Accepted: 02/28/2023] [Indexed: 03/08/2023]
Abstract
Here, we demonstrate the utility of native membrane derived vesicles (nMVs) as tools for expeditious electrophysiological analysis of membrane proteins. We used a cell-free (CF) and a cell-based (CB) approach for preparing protein-enriched nMVs. We utilized the Chinese Hamster Ovary (CHO) lysate-based cell-free protein synthesis (CFPS) system to enrich ER-derived microsomes in the lysate with the primary human cardiac voltage-gated sodium channel 1.5 (hNaV1.5; SCN5A) in 3 h. Subsequently, CB-nMVs were isolated from fractions of nitrogen-cavitated CHO cells overexpressing the hNaV1.5. In an integrative approach, nMVs were micro-transplanted into Xenopus laevis oocytes. CB-nMVs expressed native lidocaine-sensitive hNaV1.5 currents within 24 h; CF-nMVs did not elicit any response. Both the CB- and CF-nMV preparations evoked single-channel activity on the planar lipid bilayer while retaining sensitivity to lidocaine application. Our findings suggest a high usability of the quick-synthesis CF-nMVs and maintenance-free CB-nMVs as ready-to-use tools for in-vitro analysis of electrogenic membrane proteins and large, voltage-gated ion channels.
Collapse
Affiliation(s)
- Yogesh Pandey
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; Institut für Biochemie und Biologie, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam OT Golm, Germany
| | - Srujan Kumar Dondapati
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany.
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; Technische Universität Berlin, Institute of Biotechnology, Straße des 17. Juni 135, 10623 Berlin, Germany; Freie Universität Berlin, Institute of Chemistry and Biochemistry, 14195 Berlin, Germany; Faculty of Health Science, Joint Faculty of the Brandenburg University of Technology Cottbus-Senftenberg, the Brandenburg Medical School Theodor Fontane and the University of Potsdam, Germany
| |
Collapse
|
7
|
Pommereau A, Licher T, Bärenz F. Solid-Supported Membrane (SSM)-Based Electrophysiology Assays Using Surface Electrogenic Event Reader Technology (SURFE²R) in Early Drug Discovery. Curr Protoc 2023; 3:e650. [PMID: 36912603 DOI: 10.1002/cpz1.650] [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: 03/14/2023]
Abstract
This article presents detailed descriptions of procedures and troubleshooting tips for solid-supported membrane (SSM)-based electrophysiology assays (SURFE²R) to measure electrogenic solute carrier transporter proteins (SLCs) and assess the effects of compounds that modulate their activity. SURFE²R allows the use of the standard 96-well format, making it an ideal platform for tertiary assays in a drug-discovery campaign. The assays are performed with cell-line-derived membrane fractions or proteoliposomes containing the transporter of interest. Three main protocols are described for the isolation of membrane fractions from cell culture and the generation of proteoliposomes containing the transporter of interest. Additionally, detailed protocols for SURFE²R single concentration and dose-response experiments are included to measure the potencies of test compounds in stimulating or inhibiting transporter function (EC50 or IC50 values, respectively) and kinetic functional assays to calculate apparent affinity (kM ) and maximal velocity (Vmax ) of substrate uptake. © 2023 Sanofi. Current Protocols published by Wiley Periodicals LLC. PROTOCOL GROUP 1: Sample preparation for SSM-based electrophysiology assays Support Protocol 1: Production of cell batches Support Protocol 2: Simple isolation of cell membranes Alternate Protocol 1: Isolation of cell membranes with sucrose gradient pre-purification Support Protocol 3: Production and isolation of liposomes Support Protocol 4: Preparation of sensor with isolated cell membranes Alternate Protocol 2: Preparation of sensor with isolated proteoliposomes PROTOCOL GROUP 2: Determination of assay parameters for SSM-based electrophysiology assay Support Protocol 5: Assay with stable buffer Alternate Protocol 3: Assay with ion gradient Support Protocol 6: Determination of membrane/liposome concentration Support Protocol 7: Determination of substrate dependency kM PROTOCOL GROUP 3: Determination of advanced assay parameters for SSM-based electrophysiology assays Support Protocol 8: Assessment of ion concentration dependency Support Protocol 9: Assessment of pH dependency Support Protocol 10: Assessment of DMSO dependency Support Protocol 11: Assessment of signal stability with multiple activations PROTOCOL GROUP 4: Compound testing through SSM-based electrophysiology assays using SURFE²R apparatus Support Protocol 12: Assessment of signal specificity of a published inhibitor or unknown compound(s) Support Protocol 13: Compound wash-out Support Protocol 14: Statistical analysis.
Collapse
Affiliation(s)
- Antje Pommereau
- Sanofi, Integrated Drug Discovery, Industriepark Hoechst, Frankfurt am Main, Germany
| | - Thomas Licher
- Sanofi, Integrated Drug Discovery, Industriepark Hoechst, Frankfurt am Main, Germany
| | - Felix Bärenz
- Sanofi, Integrated Drug Discovery, Industriepark Hoechst, Frankfurt am Main, Germany
| |
Collapse
|
8
|
Bazzone A, Zerlotti R, Barthmes M, Fertig N. Functional characterization of SGLT1 using SSM-based electrophysiology: Kinetics of sugar binding and translocation. Front Physiol 2023; 14:1058583. [PMID: 36824475 PMCID: PMC9941201 DOI: 10.3389/fphys.2023.1058583] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/17/2023] [Indexed: 02/10/2023] Open
Abstract
Beside the ongoing efforts to determine structural information, detailed functional studies on transporters are essential to entirely understand the underlying transport mechanisms. We recently found that solid supported membrane-based electrophysiology (SSME) enables the measurement of both sugar binding and transport in the Na+/sugar cotransporter SGLT1 (Bazzone et al, 2022a). Here, we continued with a detailed kinetic characterization of SGLT1 using SSME, determining KM and KD app for different sugars, kobs values for sugar-induced conformational transitions and the effects of Na+, Li+, H+ and Cl- on sugar binding and transport. We found that the sugar-induced pre-steady-state (PSS) charge translocation varies with the bound ion (Na+, Li+, H+ or Cl-), but not with the sugar species, indicating that the conformational state upon sugar binding depends on the ion. Rate constants for the sugar-induced conformational transitions upon binding to the Na+-bound carrier range from 208 s-1 for D-glucose to 95 s-1 for 3-OMG. In the absence of Na+, rate constants are decreased, but all sugars bind to the empty carrier. From the steady-state transport current, we found a sequence for sugar specificity (Vmax/KM): D-glucose > MDG > D-galactose > 3-OMG > D-xylose. While KM differs 160-fold across tested substrates and plays a major role in substrate specificity, Vmax only varies by a factor of 1.9. Interestingly, D-glucose has the lowest Vmax across all tested substrates, indicating a rate limiting step in the sugar translocation pathway following the fast sugar-induced electrogenic conformational transition. SGLT1 specificity for D-glucose is achieved by optimizing two ratios: the sugar affinity of the empty carrier for D-glucose is similarly low as for all tested sugars (KD,K app = 210 mM). Affinity for D-glucose increases 14-fold (KD,Na app = 15 mM) in the presence of sodium as a result of cooperativity. Apparent affinity for D-glucose during transport increases 8-fold (KM = 1.9 mM) compared to KD,Na app due to optimized kinetics. In contrast, KM and KD app values for 3-OMG and D-xylose are of similar magnitude. Based on our findings we propose an 11-state kinetic model, introducing a random binding order and intermediate states corresponding to the electrogenic transitions detected via SSME upon substrate binding.
Collapse
Affiliation(s)
- Andre Bazzone
- Nanion Technologies GmbH, Munich, Germany,*Correspondence: Andre Bazzone,
| | - Rocco Zerlotti
- Nanion Technologies GmbH, Munich, Germany,Department of Structural Biology, Faculty of Biology and Pre-Clinics, Institute of Biochemistry, Genetics and Microbiology, University of Regensburg, Regensburg, Germany
| | | | | |
Collapse
|
9
|
Bazzone A, Tesmer L, Kurt D, Kaback HR, Fendler K, Madej MG. Investigation of sugar binding kinetics of the E. coli sugar/H + symporter XylE using solid supported membrane-based electrophysiology. J Biol Chem 2021; 298:101505. [PMID: 34929170 PMCID: PMC8784342 DOI: 10.1016/j.jbc.2021.101505] [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: 09/15/2021] [Revised: 12/11/2021] [Accepted: 12/13/2021] [Indexed: 12/19/2022] Open
Abstract
Bacterial transporters are difficult to study using conventional electrophysiology because of their low transport rates and the small size of bacterial cells. Here, we applied solid-supported membrane–based electrophysiology to derive kinetic parameters of sugar translocation by the Escherichia coli xylose permease (XylE), including functionally relevant mutants. Many aspects of the fucose permease (FucP) and lactose permease (LacY) have also been investigated, which allow for more comprehensive conclusions regarding the mechanism of sugar translocation by transporters of the major facilitator superfamily. In all three of these symporters, we observed sugar binding and transport in real time to determine KM, Vmax, KD, and kobs values for different sugar substrates. KD and kobs values were attainable because of a conserved sugar-induced electrogenic conformational transition within these transporters. We also analyzed interactions between the residues in the available X-ray sugar/H+ symporter structures obtained with different bound sugars. We found that different sugars induce different conformational states, possibly correlating with different charge displacements in the electrophysiological assay upon sugar binding. Finally, we found that mutations in XylE altered the kinetics of glucose binding and transport, as Q175 and L297 are necessary for uncoupling H+ and d-glucose translocation. Based on the rates for the electrogenic conformational transition upon sugar binding (>300 s−1) and for sugar translocation (2 s−1 − 30 s−1 for different substrates), we propose a multiple-step mechanism and postulate an energy profile for sugar translocation. We also suggest a mechanism by which d-glucose can act as an inhibitor for XylE.
Collapse
Affiliation(s)
- Andre Bazzone
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - Laura Tesmer
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - Derya Kurt
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - H Ronald Kaback
- University of California, Department of Physiology and Department of Microbiology, Immunology, Molecular Genetics, Molecular Biology Institute in Los Angeles CA, USA
| | - Klaus Fendler
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - M Gregor Madej
- Institute of Biophysics and Biophysical Chemistry, Department of Structural Biology, University of Regensburg, Universitätsstr. 31, 95053 Regensburg, Germany; Institute of Biophysics, Department of Structural Biology, Saarland University, Center of Human and Molecular Biology, Building 60, 66421 Homburg, Germany
| |
Collapse
|