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Ayub H, Murray RJ, Kuyler GC, Napier-Khwaja F, Gunner J, Dafforn TR, Klumperman B, Poyner DR, Wheatley M. GPCRs in the round: SMA-like copolymers and SMALPs as a platform for investigating GPCRs. Arch Biochem Biophys 2024; 754:109946. [PMID: 38395122 DOI: 10.1016/j.abb.2024.109946] [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: 11/24/2023] [Revised: 01/21/2024] [Accepted: 02/20/2024] [Indexed: 02/25/2024]
Abstract
G-protein-coupled receptors (GPCRs) are the largest family of membrane proteins, regulate a plethora of physiological responses and are the therapeutic target for 30-40% of clinically-prescribed drugs. They are integral membrane proteins deeply embedded in the plasma membrane where they activate intracellular signalling via coupling to G-proteins and β-arrestin. GPCRs are in intimate association with the bilayer lipids and that lipid environment regulates the signalling functions of GPCRs. This complex lipid 'landscape' is both heterogeneous and dynamic. GPCR function is modulated by bulk membrane properties including membrane fluidity, microdomains, curvature, thickness and asymmetry but GPCRs are also regulated by specific lipid:GPCR binding, including cholesterol and anionic lipids. Understanding the molecular mechanisms whereby GPCR signalling is regulated by lipids is a very active area of research currently. A major advance in membrane protein research in recent years was the application of poly(styrene-co-maleic acid) (SMA) copolymers. These spontaneously generate SMA lipid particles (SMALPs) encapsulating membrane protein in a nano-scale disc of cell membrane, thereby removing the historical need for detergent and preserving lipid:GPCR interaction. The focus of this review is how GPCR-SMALPs are increasing our understanding of GPCR structure and function at the molecular level. Furthermore, an increasing number of 'second generation' SMA-like copolymers have been reported recently. These are reviewed from the context of increasing our understanding of GPCR molecular mechanisms. Moreover, their potential as a novel platform for downstream biophysical and structural analyses is assessed and looking ahead, the translational application of SMA-like copolymers to GPCR drug discovery programmes in the future is considered.
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Affiliation(s)
- Hoor Ayub
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK.
| | - Rebecca J Murray
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Gestél C Kuyler
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | | | - Joseph Gunner
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK
| | - Tim R Dafforn
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Bert Klumperman
- Department of Chemistry and Polymer Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - David R Poyner
- School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK
| | - Mark Wheatley
- Centre for Health and Life Sciences, Coventry University, Coventry, CV1 2DS, UK; Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK
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Janata M, Gupta S, Čadová E, Angelisová P, Krishnarjuna B, Ramamoorthy A, Hořejší V, Raus V. Sulfonated polystyrenes: pH and Mg 2+-insensitive amphiphilic copolymers for detergent-free membrane protein isolation. Eur Polym J 2023; 198:112412. [PMID: 37780808 PMCID: PMC10538444 DOI: 10.1016/j.eurpolymj.2023.112412] [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] [Indexed: 10/03/2023]
Abstract
Amphiphilic polymers are increasingly applied in the detergent-free isolation and functional studies of membrane proteins. However, the carboxylate group present in the structure of many popular variants, such as styrene-maleic acid (SMA) copolymers, brings limitations in terms of polymer sensitivity to precipitation at acidic pH or in the presence of divalent metal cations. Herein, we addressed this problem by replacing carboxylate with the more acidic sulfonate groups. To this end, we synthesized a library of amphiphilic poly[styrene-co-(sodium 4-styrene sulfonate)] copolymers (termed SSS), differing in their molecular weight and overall polarity. Using model cell membranes (Jurkat), we identified two copolymer compositions (SSS-L30 and SSS-L36) that solubilized membranes to an extent similar to SMA. Interestingly, the density gradient ultracentrifugation/SDS-PAGE/Western blotting analysis of cell lysates revealed a distribution of studied membrane proteins in the gradient fractions that was different than for SMA-solubilized membranes. Importantly, unlike SMA, the SSS copolymers remained soluble at low pH and in the presence of Mg2+ ions. Additionally, the solubilization of DMPC liposomes by the lead materials was studied by turbidimetry, DLS, SEC, and high-resolution NMR, revealing, for SSS-L36, the formation of stable particles (nanodiscs), facilitated by the direct hydrophobic interaction of the copolymer phenyls with lipid acyl chains.
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Affiliation(s)
- Miroslav Janata
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Sachin Gupta
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Eva Čadová
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
| | - Pavla Angelisová
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics Program, Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering, Michigan Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Václav Hořejší
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic
| | - Vladimír Raus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, 162 06 Prague 6, Czech Republic
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Janata M, Čadová E, Angelisová P, Charnavets T, Hořejší V, Raus V. Tailoring Butyl Methacrylate/Methacrylic Acid Copolymers for the Solubilization of Membrane Proteins: The Influence of Composition and Molecular Weight. Macromol Biosci 2022; 22:e2200284. [PMID: 35964154 DOI: 10.1002/mabi.202200284] [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: 07/11/2022] [Revised: 08/02/2022] [Indexed: 11/11/2022]
Abstract
Low-molecular weight (MW) amphiphilic copolymers have been recently introduced as a powerful tool for the detergent-free isolation of cell membrane proteins. Herein, we use a screening approach to identify a new copolymer type for this application. Via a two-step ATRP/acidolysis procedure, we prepare a 3×3 matrix of well-defined poly[(butyl methacrylate)-co-(methacrylic acid)] copolymers (denoted BMAA) differing in their MW and ratio of hydrophobic (BMA) and hydrophilic (MAA) units. Subsequently, using the biologically relevant model (T-cell line Jurkat), we identify two compositions of BMAA copolymers that solubilize cell membranes to an extent comparable to the industry standard, styrene-maleic acid copolymer (SMA), while avoiding the potentially problematic phenyl groups. Surprisingly, while only the lowest-MW variant of the BMA/MAA 2:1 composition is effective, all the copolymers of the BMA/MAA 1:1 composition are found to solubilize the model membranes, including the high-MW variant (MW of 14 000). Importantly, the density gradient ultracentrifugation/SDS PAGE/Western blotting experiments reveal that the BMA/MAA 1:1 copolymers disintegrate the Jurkat membranes differently than SMA, as demonstrated by the different distribution patterns of two tested membrane protein markers. This makes the BMAA copolymers a useful tool for studies on membrane microdomains differing in their composition and resistance to membrane-disintegrating polymers. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Miroslav Janata
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
| | - Eva Čadová
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
| | - Pavla Angelisová
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic
| | - Tatsiana Charnavets
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic.,T. Charnavets, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Průmyslová 595, Vestec, CZ-25242, Czech Republic
| | - Václav Hořejší
- Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, Prague 4, 142 20, Czech Republic
| | - Vladimír Raus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovského nám. 2, Prague 6, 162 06, Czech Republic
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