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Studies of SMOOTHENED Activation in Cell-Free and Reconstituted Systems. Methods Mol Biol 2021. [PMID: 34562251 DOI: 10.1007/978-1-0716-1701-4_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Much of our current understanding of Hedgehog signal transduction derives from studies involving intact cells and organisms. Here we describe the use of cell-free and reconstituted systems to study a key step in Hedgehog signal transduction: the activation of SMOOTHENED by membrane lipids. These methods can be adapted to study other steps in Hedgehog signal transduction, particularly those that occur at the membrane.
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2
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Lavington S, Watts A. Lipid nanoparticle technologies for the study of G protein-coupled receptors in lipid environments. Biophys Rev 2020; 12:10.1007/s12551-020-00775-5. [PMID: 33215301 PMCID: PMC7755959 DOI: 10.1007/s12551-020-00775-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 11/06/2020] [Indexed: 12/12/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are a large family of integral membrane proteins which conduct a wide range of biological roles and represent significant drug targets. Most biophysical and structural studies of GPCRs have been conducted on detergent-solubilised receptors, and it is clear that detergents can have detrimental effects on GPCR function. Simultaneously, there is increasing appreciation of roles for specific lipids in modulation of GPCR function. Lipid nanoparticles such as nanodiscs and styrene maleic acid lipid particles (SMALPs) offer opportunities to study integral membrane proteins in lipid environments, in a form that is soluble and amenable to structural and biophysical experiments. Here, we review the application of lipid nanoparticle technologies to the study of GPCRs, assessing the relative merits and limitations of each system. We highlight how these technologies can provide superior platforms to detergents for structural and biophysical studies of GPCRs and inform on roles for protein-lipid interactions in GPCR function.
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Affiliation(s)
- Steven Lavington
- Biochemistry Department, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Anthony Watts
- Biochemistry Department, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
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3
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Doi T, Kikuta K, Tani K. Characterization of Critical Residues in the Extracellular and Transmembrane Domains of the Endothelin Type B Receptor for Propagation of the Endothelin-1 Signal. Biochemistry 2020; 59:1718-1727. [PMID: 32343134 DOI: 10.1021/acs.biochem.0c00158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have previously reported the crystal structures of endothelin-1 (ET-1)-bound, ligand-free, and antagonist bosentan-bound forms of the thermostabilized ET type B receptor (ETB). Although other agonist-bound structures of ETB have been determined, the interactions for high-affinity binding and ETB receptor activation, as well as the roles of rearrangement of the hydrogen-bond network surrounding the ligand in G protein activation, remain elusive. ET-1, a 21-amino acid residue peptide, plays fundamental roles in basal vascular tone, sodium balance, cell proliferation, and stress-responsive regulation. We studied the interactions between the ET-1(8-21) peptide and ETB in the ligand binding and activation of ETB using a series of Ala-substituted ET-1(8-21) analogues and the mutated ETB. We found that while D8, L17, D18, I20, and W21 were responsible for high-affinity binding and potent G protein activation, Y13 and F14 in the helical region of ET-1 are prerequisites for the full activation of ETB via interactions near the extracellular side. Furthermore, we introduced the mutation into the residues around the ET-1 binding pocket of ETB. The results showed that while S1843.35, W3366.48, N3787.45, and S3797.46 in a conserved polar network are required for full activation, N1191.50, D1472.50, and N3827.49 are essential for G protein activation via direct interactions after rearrangement upon ET-1 binding. These results demonstrate that both interactions near the extracellular side and within the transmembrane helices with ET-1 play crucial roles in the full activation of the ETB receptor.
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Affiliation(s)
- Tomoko Doi
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Kohei Kikuta
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Kazutoshi Tani
- Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie 514-8507, Japan
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Koehl A, Hu H, Feng D, Sun B, Zhang Y, Robertson MJ, Chu M, Kobilka TS, Laeremans T, Steyaert J, Tarrasch J, Dutta S, Fonseca R, Weis WI, Mathiesen JM, Skiniotis G, Kobilka BK. Structural insights into the activation of metabotropic glutamate receptors. Nature 2019; 566:79-84. [PMID: 30675062 PMCID: PMC6709600 DOI: 10.1038/s41586-019-0881-4] [Citation(s) in RCA: 205] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 12/12/2018] [Indexed: 12/11/2022]
Abstract
Metabotropic glutamate receptors are family C G-protein-coupled receptors. They form obligate dimers and possess extracellular ligand-binding Venus flytrap domains, which are linked by cysteine-rich domains to their 7-transmembrane domains. Spectroscopic studies show that signalling is a dynamic process, in which large-scale conformational changes underlie the transmission of signals from the extracellular Venus flytraps to the G protein-coupling domains-the 7-transmembrane domains-in the membrane. Here, using a combination of X-ray crystallography, cryo-electron microscopy and signalling studies, we present a structural framework for the activation mechanism of metabotropic glutamate receptor subtype 5. Our results show that agonist binding at the Venus flytraps leads to a compaction of the intersubunit dimer interface, thereby bringing the cysteine-rich domains into close proximity. Interactions between the cysteine-rich domains and the second extracellular loops of the receptor enable the rigid-body repositioning of the 7-transmembrane domains, which come into contact with each other to initiate signalling.
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Affiliation(s)
- Antoine Koehl
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Hongli Hu
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Dan Feng
- ConfometRx, Santa Clara, CA, USA
| | | | - Yan Zhang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Michael J Robertson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Tong Sun Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,ConfometRx, Santa Clara, CA, USA
| | - Toon Laeremans
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Jeffrey Tarrasch
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Somnath Dutta
- Life Sciences Institute and Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, USA.,Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Rasmus Fonseca
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Biosciences Division, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA, USA
| | - William I Weis
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jesper M Mathiesen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Georgios Skiniotis
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA. .,ConfometRx, Santa Clara, CA, USA.
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5
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Rapid, direct activity assays for Smoothened reveal Hedgehog pathway regulation by membrane cholesterol and extracellular sodium. Proc Natl Acad Sci U S A 2017; 114:E11141-E11150. [PMID: 29229834 DOI: 10.1073/pnas.1717891115] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Hedgehog signaling specifies tissue patterning and renewal, and pathway components are commonly mutated in certain malignancies. Although central to ensuring appropriate pathway activity in all Hedgehog-responsive cells, how the transporter-like receptor Patched1 regulates the seven-transmembrane protein Smoothened remains mysterious, partially due to limitations in existing tools and experimental systems. Here we employ direct, real-time, biochemical and physiology-based approaches to monitor Smoothened activity in cellular and in vitro contexts. Patched1-Smoothened coupling is rapid, dynamic, and can be recapitulated without cilium-specific proteins or lipids. By reconstituting purified Smoothened in vitro, we show that cholesterol within the bilayer is sufficient for constitutive Smoothened activation. Cholesterol effects occur independently of the lipid-binding Smoothened extracellular domain, a region that is dispensable for Patched1-Smoothened coupling. Finally, we show that Patched1 specifically requires extracellular Na+ to regulate Smoothened in our assays, raising the possibility that a Na+ gradient provides the energy source for Patched1 catalytic activity. Our work suggests a hypothesis wherein Patched1, chemiosmotically driven by the transmembrane Na+ gradient common to metazoans, regulates Smoothened by shielding its heptahelical domain from cholesterol, or by providing an inhibitor that overrides this cholesterol activation.
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Assembly of phospholipid nanodiscs of controlled size for structural studies of membrane proteins by NMR. Nat Protoc 2017; 13:79-98. [PMID: 29215632 DOI: 10.1038/nprot.2017.094] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Suitable membrane mimetics are crucial to the performance of structural and functional studies of membrane proteins. Phospholipid nanodiscs (formed when a membrane scaffold protein encircles a small portion of a lipid bilayer) have native-like membrane properties. These have been used for a variety of functional studies, but structural studies by high-resolution solution-state NMR spectroscopy of membrane proteins in commonly used nanodiscs of 10-nm diameter were limited by the high molecular weight of these particles, which caused unfavorably large NMR line widths. We have recently constructed truncated versions of the membrane scaffold protein, allowing the preparation of a range of stepwise-smaller nanodiscs (6- to 8-nm diameter) to overcome this limitation. Here, we present a protocol on the assembly of phospholipid nanodiscs of various sizes for structural studies of membrane proteins with solution-state NMR spectroscopy. We describe specific isotope-labeling schemes required for working with large membrane protein systems in nanodiscs, and provide guidelines on the setup of NMR non-uniform sampling (NUS) data acquisition and high-resolution NMR spectra reconstruction. We discuss critical points and pitfalls relating to optimization of nanodiscs for NMR spectroscopy and outline a strategy for the high-resolution structure determination and positioning of isotope-labeled membrane proteins in nanodiscs using nuclear Overhauser enhancement spectroscopy (NOESY) spectroscopy, residual dipolar couplings (RDCs) and paramagnetic relaxation enhancements (PREs). Depending on the target protein of interest, nanodisc assembly and purification can be achieved within 12-24 h. Although the focus of this protocol is on protein NMR, these nanodiscs can also be used for (cryo-) electron microscopy (EM) and small-angle X-ray and neutron-scattering studies.
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Brea RJ, Cole CM, Lyda BR, Ye L, Prosser RS, Sunahara RK, Devaraj NK. In Situ Reconstitution of the Adenosine A 2A Receptor in Spontaneously Formed Synthetic Liposomes. J Am Chem Soc 2017; 139:3607-3610. [PMID: 28263576 DOI: 10.1021/jacs.6b12830] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cell transmembrane receptors play a key role in the detection of environmental stimuli and control of intracellular communication. G protein-coupled receptors constitute the largest transmembrane protein family involved in cell signaling. However, current methods for their functional reconstitution in biomimetic membranes remain both challenging and limited in scope. Herein, we describe the spontaneous reconstitution of adenosine A2A receptor (A2AR) during the de novo formation of synthetic liposomes via native chemical ligation. The approach takes advantage of a nonenzymatic and chemoselective method to rapidly generate A2AR embedded phospholiposomes from receptor solubilized in n-dodecyl-β-d-maltoside analogs. In situ lipid synthesis for protein reconstitution technology proceeds in the absence of dialysis and/or detergent absorbents, and A2AR assimilation into synthetic liposomes can be visualized by microscopy and probed by radio-ligand binding.
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Affiliation(s)
- Roberto J Brea
- Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093, United States
| | - Christian M Cole
- Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093, United States
| | - Brent R Lyda
- Department of Pharmacology, University of California, San Diego , La Jolla, California 92093, United States
| | - Libin Ye
- Department of Chemistry, University of Toronto , Mississauga, Ontario L5L 1C6, Canada
| | - R Scott Prosser
- Department of Chemistry, University of Toronto , Mississauga, Ontario L5L 1C6, Canada
| | - Roger K Sunahara
- Department of Pharmacology, University of California, San Diego , La Jolla, California 92093, United States
| | - Neal K Devaraj
- Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093, United States
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8
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Allosteric regulation of G protein-coupled receptor activity by phospholipids. Nat Chem Biol 2015; 12:35-9. [PMID: 26571351 DOI: 10.1038/nchembio.1960] [Citation(s) in RCA: 218] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/25/2015] [Indexed: 01/29/2023]
Abstract
Lipids are emerging as key regulators of membrane protein structure and activity. These effects can be attributed either to the modification of bilayer properties (thickness, curvature and surface tension) or to the binding of specific lipids to the protein surface. For G protein-coupled receptors (GPCRs), the effects of phospholipids on receptor structure and activity remain poorly understood. Here we reconstituted purified β2-adrenergic receptor (β2R) in high-density lipoparticles to systematically characterize the effect of biologically relevant phospholipids on receptor activity. We observed that the lipid headgroup type affected ligand binding (agonist and antagonist) and receptor activation. Specifically, phosphatidylgycerol markedly favored agonist binding and facilitated receptor activation, whereas phosphatidylethanolamine favored antagonist binding and stabilized the inactive state of the receptor. We then showed that these effects could be recapitulated with detergent-solubilized lipids, demonstrating that the functional modulation occurred in the absence of a bilayer. Our data suggest that phospholipids act as direct allosteric modulators of GPCR activity.
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Halls ML, Bathgate RAD, Sutton SW, Dschietzig TB, Summers RJ. International Union of Basic and Clinical Pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1-4, the receptors for relaxin family peptides. Pharmacol Rev 2015; 67:389-440. [PMID: 25761609 DOI: 10.1124/pr.114.009472] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Relaxin, insulin-like peptide 3 (INSL3), relaxin-3, and INSL5 are the cognate ligands for the relaxin family peptide (RXFP) receptors 1-4, respectively. RXFP1 activates pleiotropic signaling pathways including the signalosome protein complex that facilitates high-sensitivity signaling; coupling to Gα(s), Gα(i), and Gα(o) proteins; interaction with glucocorticoid receptors; and the formation of hetero-oligomers with distinctive pharmacological properties. In addition to relaxin-related ligands, RXFP1 is activated by Clq-tumor necrosis factor-related protein 8 and by small-molecular-weight agonists, such as ML290 [2-isopropoxy-N-(2-(3-(trifluoromethylsulfonyl)phenylcarbamoyl)phenyl)benzamide], that act allosterically. RXFP2 activates only the Gα(s)- and Gα(o)-coupled pathways. Relaxin-3 is primarily a neuropeptide, and its cognate receptor RXFP3 is a target for the treatment of depression, anxiety, and autism. A variety of peptide agonists, antagonists, biased agonists, and an allosteric modulator target RXFP3. Both RXFP3 and the related RXFP4 couple to Gα(i)/Gα(o) proteins. INSL5 has the properties of an incretin; it is secreted from the gut and is orexigenic. The expression of RXFP4 in gut, adipose tissue, and β-islets together with compromised glucose tolerance in INSL5 or RXFP4 knockout mice suggests a metabolic role. This review focuses on the many advances in our understanding of RXFP receptors in the last 5 years, their signal transduction mechanisms, the development of novel compounds that target RXFP1-4, the challenges facing the field, and current prospects for new therapeutics.
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Affiliation(s)
- Michelle L Halls
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Ross A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Steve W Sutton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Thomas B Dschietzig
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Roger J Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
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Thoene J, Goss T, Witcher M, Mullet J, N'Kuli F, Van Der Smissen P, Courtoy P, Hahn SH. In vitro correction of disorders of lysosomal transport by microvesicles derived from baculovirus-infected Spodoptera cells. Mol Genet Metab 2013; 109:77-85. [PMID: 23465695 DOI: 10.1016/j.ymgme.2013.01.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/24/2013] [Accepted: 01/24/2013] [Indexed: 01/29/2023]
Abstract
Infection of Spodoptera frugiperda (Sf9) cells by baculovirus (BV) is well established for transgene expression of soluble proteins, but few correctly folded transmembrane proteins have been so produced. We here report the use of the BV/Sf9 (BVES) method for the expression and transfer, via microvesicles, of the exclusive lysosomal exporters for cystine and sialic acid, human cystinosin and sialin. These proteins and their mRNA are released into the culture medium as very low-density microvesicles (~1.05 g/ml), which do not label for lysobisphosphatidic acid. The presence of the human transgene proteins in the vesicles was confirmed by western blotting and confirmed and quantified by mass spectrometry. Addition of vesicles to cultures of human fibroblast lines deficient in either cystinosin or sialin produced a progressive depletion of stored lysosomal cystine or sialic acid, respectively. The depletion effect was slow (T1/2 ~48 h), saturable (down to ~40% of initial after 4 days) and stable (>one week). Surprisingly, BV infection of Spodoptera appeared to induce expression and release into microvesicles of the insect orthologue of cystinosin, but not of sialin. We conclude that BVES is an effective method to express and transfer functional transmembrane proteins so as to study their properties in mammalian cells, and has a generic potential for transport protein replacement therapy.
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Affiliation(s)
- Jess Thoene
- Department of Pediatric Genetics, University of Michigan, Ann Arbor, MI 48109-5629, USA.
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Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ. Relaxin family peptides and their receptors. Physiol Rev 2013; 93:405-80. [PMID: 23303914 DOI: 10.1152/physrev.00001.2012] [Citation(s) in RCA: 379] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
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Affiliation(s)
- R A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences & Department of Pharmacology, Monash University, Victoria, Australia
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12
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Kriechbaumer V, Nabok A, Widdowson R, Smith DP, Abell BM. Quantification of ligand binding to G-protein coupled receptors on cell membranes by ellipsometry. PLoS One 2012; 7:e46221. [PMID: 23049983 PMCID: PMC3458955 DOI: 10.1371/journal.pone.0046221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 08/28/2012] [Indexed: 12/18/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are prime drug targets and targeted by approximately 60% of current therapeutic drugs such as β-blockers, antipsychotics and analgesics. However, no biophysical methods are available to quantify their interactions with ligand binding in a native environment. Here, we use ellipsometry to quantify specific interactions of receptors within native cell membranes. As a model system, the GPCR-ligand CXCL12α and its receptor CXCR4 are used. Human-derived Ishikawa cells were deposited onto gold coated slides via Langmuir-Schaefer film deposition and interactions between the receptor CXCR4 on these cells and its ligand CXCL12α were detected via total internal reflection ellipsometry (TIRE). This interaction could be inhibited by application of the CXCR4-binding drug AMD3100. Advantages of this approach are that it allows measurement of interactions in a lipid environment without the need for labelling, protein purification or reconstitution of membrane proteins. This technique is potentially applicable to a wide variety of cell types and their membrane receptors, providing a novel method to determine ligand or drug interactions targeting GPCRs and other membrane proteins.
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Affiliation(s)
- Verena Kriechbaumer
- Biomedical Research Centre, Sheffield Hallam University, Sheffield, United Kingdom.
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