1
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Dumont ME, Konopka JB. Comparison of Experimental Approaches Used to Determine the Structure and Function of the Class D G Protein-Coupled Yeast α-Factor Receptor. Biomolecules 2022; 12:biom12060761. [PMID: 35740886 PMCID: PMC9220813 DOI: 10.3390/biom12060761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/26/2022] [Accepted: 05/27/2022] [Indexed: 02/01/2023] Open
Abstract
The Saccharomyces cerevisiae α-factor mating pheromone receptor (Ste2p) has been studied as a model for the large medically important family of G protein-coupled receptors. Diverse yeast genetic screens and high-throughput mutagenesis of STE2 identified a large number of loss-of-function, constitutively-active, dominant-negative, and intragenic second-site suppressor mutants as well as mutations that specifically affect pheromone binding. Facile genetic manipulation of Ste2p also aided in targeted biochemical approaches, such as probing the aqueous accessibility of substituted cysteine residues in order to identify the boundaries of the seven transmembrane segments, and the use of cysteine disulfide crosslinking to identify sites of intramolecular contacts in the transmembrane helix bundle of Ste2p and sites of contacts between the monomers in a Ste2p dimer. Recent publication of a series of high-resolution cryo-EM structures of Ste2p in ligand-free, agonist-bound and antagonist-bound states now makes it possible to evaluate the results of these genetic and biochemical strategies, in comparison to three-dimensional structures showing activation-related conformational changes. The results indicate that the genetic and biochemical strategies were generally effective, and provide guidance as to how best to apply these experimental strategies to other proteins. These strategies continue to be useful in defining mechanisms of signal transduction in the context of the available structures and suggest aspects of receptor function beyond what can be discerned from the available structures.
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Affiliation(s)
- Mark E. Dumont
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
- Correspondence: ; Tel.: +1-585-275-2466
| | - James B. Konopka
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, NY 11794-5222, USA;
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2
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Velazhahan V, Ma N, Vaidehi N, Tate CG. Activation mechanism of the class D fungal GPCR dimer Ste2. Nature 2022; 603:743-748. [PMID: 35296853 PMCID: PMC8942848 DOI: 10.1038/s41586-022-04498-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 02/01/2022] [Indexed: 02/06/2023]
Abstract
The fungal class D1 G-protein-coupled receptor (GPCR) Ste2 has a different arrangement of transmembrane helices compared with mammalian GPCRs and a distinct mode of coupling to the heterotrimeric G protein Gpa1-Ste2-Ste181. In addition, Ste2 lacks conserved sequence motifs such as DRY, PIF and NPXXY, which are associated with the activation of class A GPCRs2. This suggested that the activation mechanism of Ste2 may also differ. Here we determined structures of Saccharomyces cerevisiae Ste2 in the absence of G protein in two different conformations bound to the native agonist α-factor, bound to an antagonist and without ligand. These structures revealed that Ste2 is indeed activated differently from other GPCRs. In the inactive state, the cytoplasmic end of transmembrane helix H7 is unstructured and packs between helices H1-H6, blocking the G protein coupling site. Agonist binding results in the outward movement of the extracellular ends of H6 and H7 by 6 Å. On the intracellular surface, the G protein coupling site is formed by a 20 Å outward movement of the unstructured region in H7 that unblocks the site, and a 12 Å inward movement of H6. This is a distinct mechanism in GPCRs, in which the movement of H6 and H7 upon agonist binding facilitates G protein coupling.
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Affiliation(s)
| | - Ning Ma
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, CA, USA
| | - Christopher G Tate
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, UK.
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3
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Naider F, Becker JM. A Paradigm for Peptide Hormone-GPCR Analyses. Molecules 2020; 25:E4272. [PMID: 32961885 PMCID: PMC7570734 DOI: 10.3390/molecules25184272] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/16/2020] [Accepted: 09/17/2020] [Indexed: 01/14/2023] Open
Abstract
Work from our laboratories over the last 35 years that has focused on Ste2p, a G protein-coupled receptor (GPCR), and its tridecapeptide ligand α-factor is reviewed. Our work utilized the yeast Saccharomyces cerevisiae as a model system for understanding peptide-GPCR interactions. It explored the structure and function of synthetic α-factor analogs and biosynthetic receptor domains, as well as designed mutations of Ste2p. The results and conclusions are described using the nuclear magnetic resonance interrogation of synthetic Ste2p transmembrane domains (TMs), the fluorescence interrogation of agonist and antagonist binding, the biochemical crosslinking of peptide analogs to Ste2p, and the phenotypes of receptor mutants. We identified the ligand-binding domain in Ste2p, the functional assemblies of TMs, unexpected and interesting ligand analogs; gained insights into the bound α-factor structure; and unraveled the function and structures of various Ste2p domains, including the N-terminus, TMs, loops connecting the TMs, and the C-terminus. Our studies showed interactions between specific residues of Ste2p in an active state, but not resting state, and the effect of ligand activation on the dimerization of Ste2p. We show that, using a battery of different biochemical and genetic approaches, deep insight can be gained into the structure and conformational dynamics of GPCR-peptide interactions in the absence of a crystal structure.
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Affiliation(s)
- Fred Naider
- Department of Chemistry, College of Staten Island, CUNY, 2800 Victory Blvd, Staten Island, NY 10314, USA
| | - Jeffrey M. Becker
- Department of Microbiology, University of Tennessee, 610 Ken and Blaire Mossman Building, 1311 Cumberland Avenue, Knoxville, TN 37996, USA
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4
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Uddin MS, Naider F, Becker JM. Dynamic roles for the N-terminus of the yeast G protein-coupled receptor Ste2p. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2058-2067. [PMID: 28754538 DOI: 10.1016/j.bbamem.2017.07.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 07/13/2017] [Accepted: 07/24/2017] [Indexed: 12/11/2022]
Abstract
The Saccharomyces cerevisiae α-factor receptor Ste2p has been used extensively as a model to understand the molecular mechanism of signal transduction by G protein-coupled receptors (GPCRs). Single and double cysteine mutants of Ste2p were created and served as surrogates to detect intramolecular interactions and dimerization of Ste2p using disulfide cross-linking methodology. When a mutation was introduced into the phylogenetically conserved tyrosine residue at position 26 (Y26C) in the N-terminus of Ste2p, dimerization was increased greatly. The amount of dimer formed by this Y26C mutant was greatly reduced by ligand binding even though the ligand binding site is far removed from the N-terminus; the lowering of the dimer formation was consistent with a conformational change in the N-terminus of the receptor upon activation. Dimerization was decreased by double mutations Y26C/V109C or Y26C/T114C indicating that Y26 is in close proximity to V109 and T114 of extracellular loop 1 in native Ste2p. Combined with earlier studies, these results indicate previously unrecognized roles for the N-terminus of Ste2p, and perhaps of GPCRs in general, and reveal a specific N-terminus residue or region, that is involved in GPCR signaling, intrareceptor interactions, and receptor dimerization.
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Affiliation(s)
- M Seraj Uddin
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Fred Naider
- Department of Chemistry and Macromolecular Assemblies Institute, College of Staten Island, CUNY, New York, New York 10314, United States; Ph.D. Programs in Biochemistry and Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, United States
| | - Jeffrey M Becker
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States.
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5
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Marina Robles L, Millán-Pacheco C, Pastor N, Del Río G. STRUCTURE-FUNCTION STUDIES OF THE ALPHA PHEROMONE RECEPTOR FROM YEAST. TIP REVISTA ESPECIALIZADA EN CIENCIAS QUÍMICO-BIOLÓGICAS 2017. [DOI: 10.1016/j.recqb.2016.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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6
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Di Roberto RB, Chang B, Trusina A, Peisajovich SG. Evolution of a G protein-coupled receptor response by mutations in regulatory network interactions. Nat Commun 2016; 7:12344. [PMID: 27487915 PMCID: PMC4976203 DOI: 10.1038/ncomms12344] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 06/24/2016] [Indexed: 12/17/2022] Open
Abstract
All cellular functions depend on the concerted action of multiple proteins organized in complex networks. To understand how selection acts on protein networks, we used the yeast mating receptor Ste2, a pheromone-activated G protein-coupled receptor, as a model system. In Saccharomyces cerevisiae, Ste2 is a hub in a network of interactions controlling both signal transduction and signal suppression. Through laboratory evolution, we obtained 21 mutant receptors sensitive to the pheromone of a related yeast species and investigated the molecular mechanisms behind this newfound sensitivity. While some mutants show enhanced binding affinity to the foreign pheromone, others only display weakened interactions with the network's negative regulators. Importantly, the latter changes have a limited impact on overall pathway regulation, despite their considerable effect on sensitivity. Our results demonstrate that a new receptor–ligand pair can evolve through network-altering mutations independently of receptor–ligand binding, and suggest a potential role for such mutations in disease. Co-evolution of a new receptor-ligand pair will affect the downstream signal transduction network. Here, the authors use experimental evolution of yeast mating receptor Ste2 to show the effect of enhanced binding affinity and weakened interactions with the network's negative regulators on protein evolution.
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Affiliation(s)
- Raphaël B Di Roberto
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Belinda Chang
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Ala Trusina
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen Ø 2100, Denmark
| | - Sergio G Peisajovich
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
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7
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Sliva A, Kuang Z, Meluh PB, Boeke JD. Barcode Sequencing Screen Identifies SUB1 as a Regulator of Yeast Pheromone Inducible Genes. G3 (BETHESDA, MD.) 2016; 6:881-92. [PMID: 26837954 PMCID: PMC4825658 DOI: 10.1534/g3.115.026757] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Accepted: 01/27/2016] [Indexed: 11/18/2022]
Abstract
The yeast pheromone response pathway serves as a valuable model of eukaryotic mitogen-activated protein kinase (MAPK) pathways, and transcription of their downstream targets. Here, we describe application of a screening method combining two technologies: fluorescence-activated cell sorting (FACS), and barcode analysis by sequencing (Bar-Seq). Using this screening method, and pFUS1-GFP as a reporter for MAPK pathway activation, we readily identified mutants in known mating pathway components. In this study, we also include a comprehensive analysis of the FUS1 induction properties of known mating pathway mutants by flow cytometry, featuring single cell analysis of each mutant population. We also characterized a new source of false positives resulting from the design of this screen. Additionally, we identified a deletion mutant, sub1Δ, with increased basal expression of pFUS1-GFP. Here, in the first ChIP-Seq of Sub1, our data shows that Sub1 binds to the promoters of about half the genes in the genome (tripling the 991 loci previously reported), including the promoters of several pheromone-inducible genes, some of which show an increase upon pheromone induction. Here, we also present the first RNA-Seq of a sub1Δ mutant; the majority of genes have no change in RNA, but, of the small subset that do, most show decreased expression, consistent with biochemical studies implicating Sub1 as a positive transcriptional regulator. The RNA-Seq data also show that certain pheromone-inducible genes are induced less in the sub1Δ mutant relative to the wild type, supporting a role for Sub1 in regulation of mating pathway genes. The sub1Δ mutant has increased basal levels of a small subset of other genes besides FUS1, including IMD2 and FIG1, a gene encoding an integral membrane protein necessary for efficient mating.
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Affiliation(s)
- Anna Sliva
- Institute for Systems Genetics, New York University Langone School of Medicine, New York 10016 Human Genetics Program, Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Zheng Kuang
- Institute for Systems Genetics, New York University Langone School of Medicine, New York 10016
| | - Pamela B Meluh
- Calico Life Sciences, Google Inc., San Francisco, California 94080
| | - Jef D Boeke
- Institute for Systems Genetics, New York University Langone School of Medicine, New York 10016
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8
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The N-terminus of the yeast G protein-coupled receptor Ste2p plays critical roles in surface expression, signaling, and negative regulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:715-24. [PMID: 26707753 DOI: 10.1016/j.bbamem.2015.12.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/18/2015] [Accepted: 12/15/2015] [Indexed: 12/23/2022]
Abstract
G protein-coupled receptors (GPCRs) are found in all eukaryotic cells examined to date where they function as membrane-bound proteins that bind a multitude of extracellular ligands to initiate intracellular signal transduction systems controlling cellular physiology. GPCRs have seven heptahelical membrane spanning domains connected by extracellular and intracellular loops with an extracellular N-terminus and an intracellular C-terminus. The N-terminus has been the least studied domain of most GPCRs. The yeast Ste2p protein, the receptor for the thirteen amino acid peptide pheromone α-factor, has been used extensively as a model to study GPCR structure and function. In this study we constructed a number of deletions of the Ste2p N-terminus and uncovered an unexpected function as a negative regulatory domain. We examined the role of the N-terminus in expression, signaling function and ligand-binding properties and found that the residues 11-30 play a critical role in receptor expression on the cell surface. The studies also indicated that residues 2-10 of the N-terminus are involved in negative regulation of signaling as shown by the observation that deletion of these residues enhanced mating and gene induction. Furthermore, our results indicated that the residues 21-30 are essential for optimal signaling. Overall, we propose that the N-terminus of Ste2p plays multiple regulatory roles in controlling receptor function.
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9
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10
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Cohen LS, Fracchiolla KE, Becker J, Naider F. Invited review GPCR structural characterization: Using fragments as building blocks to determine a complete structure. Biopolymers 2014; 102:223-43. [DOI: 10.1002/bip.22490] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/24/2014] [Accepted: 03/27/2014] [Indexed: 12/30/2022]
Affiliation(s)
- Leah S. Cohen
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Katrina E. Fracchiolla
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Jeff Becker
- Department of Microbiology; University of Tennessee; Knoxville TN 37996
| | - Fred Naider
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
- Department of Biochemistry; The Graduate Center; CUNY NY 10016-4309
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11
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Abstract
G protein-coupled receptors (GPCRs) comprise a large class of transmembrane proteins that play critical roles in both normal physiology and pathophysiology. These critical roles offer targets for therapeutic intervention, as exemplified by the substantial fraction of current pharmaceutical agents that target members of this family. Tremendous contributions to our understanding of GPCR structure and dynamics have come from both indirect and direct structural characterization techniques. Key features of GPCR conformations derived from both types of characterization techniques are reviewed.
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Affiliation(s)
- Abby L. Parrill
- Department of Chemistry, The University of Memphis, Memphis, TN 38152, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-901-678-2638; Fax: +1-901-678-3447
| | - Debra L. Bautista
- Christian Brothers High School, 5900 Walnut Grove Road, Memphis, TN 38120, USA; E-Mail: (D.L.B.)
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12
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Dosil M, Konopka JB. Strategies for isolating constitutively active and dominant-negative pheromone receptor mutants in yeast. Methods Enzymol 2010; 485:329-48. [PMID: 21050926 DOI: 10.1016/b978-0-12-381296-4.00019-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mating pheromone receptors of the yeast Saccharomyces cerevisiae are useful models for the study of G protein-coupled receptors. The mating pheromone receptors, Ste2 and Ste3, are not essential for viability so they can be readily targeted for analysis by a variety of genetic approaches. This chapter will describe methods for identification of two kinds of mutants that have been very informative about the mechanisms of receptor signaling: constitutively active mutants and dominant-negative mutants. Interestingly, these distinct types of mutants have revealed complementary information. Constitutive signaling is caused by mutations that are thought to weaken interactions between the seven transmembrane domains (TMDs), whereas the dominant-negative mutants apparently stabilize contacts between TMDs and lock receptors in the off conformation. In support of these conclusions, certain combinations of constitutively active and dominant-negative mutants restore nearly normal signaling properties.
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Affiliation(s)
- Mercedes Dosil
- Centro de Investigación del Cáncer and Instituto de Biología Molecular y Celular del Cáncer, CSIC-University of Salamanca, Campus Unamuno, Salamanca, Spain
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13
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Tantry S, Ding FX, Dumont M, Becker JM, Naider F. Binding of fluorinated phenylalanine alpha-factor analogues to Ste2p: evidence for a cation-pi binding interaction between a peptide ligand and its cognate G protein-coupled receptor. Biochemistry 2010; 49:5007-15. [PMID: 20420459 DOI: 10.1021/bi100280f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ste2p, a G protein-coupled receptor (GPCR), binds alpha-factor, WHWLQLKPGQPMY, a tridecapeptide pheromone secreted by yeast cells. Upon alpha-factor binding, Ste2p undergoes conformational changes activating a signal transduction system through its associated heterotrimeric G protein leading to the arrest of cell growth in the G1 phase to prepare cells for mating. Previous studies have indicated that Tyr at position 13 of alpha-factor interacts with Arg58 on transmembrane one (TM1) of Ste2p. This observation prompted this investigation to determine whether a cation-pi type of interaction occurred between these residues. Tyrosine at position 13 of alpha-factor was systematically substituted with analogous amino acids with varying cation-pi binding energies using solid-phase peptide synthesis, and these analogues were modified by derivatization of their Lys(7) residue with the fluorescent group 7-nitrobenz-2-oxa-1,3-diazole (NBD) to serve as a useful probe for binding determination. Saturation binding of these peptides to Ste2p was assayed using whole yeast cells and a flow cytometer. In parallel the biological activities of the peptides were determined using a growth arrest assay. The data provide evidence for the presence of a cation-pi interaction between Arg58 of Ste2p and Tyr(13) of alpha-factor.
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Affiliation(s)
- Subramanyam Tantry
- Department of Chemistry, College of Staten Island of the City University of New York, Staten Island, New York 10314, USA
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Kim H, Lee BK, Naider F, Becker JM. Identification of specific transmembrane residues and ligand-induced interface changes involved in homo-dimer formation of a yeast G protein-coupled receptor. Biochemistry 2009; 48:10976-87. [PMID: 19839649 DOI: 10.1021/bi901291c] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The Saccharomyces cerevisiae alpha-factor pheromone receptor, Ste2p, has been studied as a model for G protein-coupled receptor (GPCR) structure and function. Dimerization has been demonstrated for many GPCRs, although the role(s) of dimerization in receptor function is disputed. Transmembrane domains one (TM1) and four (TM4) of Ste2p were shown previously to play a role in dimerization. In this study, single cysteine substitutions were introduced into a Cys-less Ste2p, and disulfide-mediated dimerization was assessed. Six residues in TM1 (L64 to M69) that had not been previously investigated and 19 residues in TM7 (T278 to A296) of which 15 were not previously investigated were mutated to create 25 single Cys-containing Ste2p molecules. Ste2p mutants V68C in TM1 and nine mutants in TM7 (cysteine substituted into residues 278, 285, 289, and 291 to 296) showed increased dimerization upon addition of an oxidizing agent in comparison to the background dimers formed by the Cys-less receptor. The formation of dimers was decreased for TM7 mutant receptors in the presence of alpha-factor indicating that ligand binding resulted in a conformational change that influenced dimerization. The effect of ligand on dimer formation suggests that dimers are formed in the resting state and the activated state of the receptor by different TM interactions.
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Affiliation(s)
- Heejung Kim
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, USA
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15
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Cano-Sanchez P, Severino B, Sureshbabu VV, Russo J, Inui T, Ding FX, Arshava B, Becker J, Naider F. Effects of N- and C-terminal addition of oligolysines or native loop residues on the biophysical properties of transmembrane domain peptides from a G-protein coupled receptor. J Pept Sci 2007; 12:808-22. [PMID: 17131294 DOI: 10.1002/psc.816] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transmembrane domains (TMDs) of G-protein coupled receptors (GPCRs) have very low water solubility and often aggregate during purification and biophysical investigations. To circumvent this problem many laboratories add oligolysines to the N- and C-termini of peptides that correspond to a TMD. To systematically evaluate the effect of the oligolysines on the biophysical properties of a TMD we synthesized 21 peptides corresponding to either the second (TPIFIINQVSLFLIILHSALYFKY) or sixth (SFHILLIMSSQSLLVPSIIFILAYSLK) TMD of Ste2p, a GPCR from Saccharomyces cerevisiae. Added to the termini of these peptides were either Lys(n) (n = 1,2,3) or the corresponding native loop residues. The biophysical properties of the peptides were investigated by circular dichroism (CD) spectroscopy in trifluoroethanol-water mixtures, sodium dodecyl sulfate (SDS) micelles and dimyristoylphosphocholine (DMPC)-dimyristoylphosphoglycerol (DMPG) vesicles, and by attenuated total reflection Fourier transform infrared (ATR-FTIR) in DMPC/DMPG multilayers. The results show that the conformation assumed depends on the number of lysine residues and the sequence of the TMD. Identical peptides with native or an equal number of lysine residues exhibited different biophysical properties and structural tendencies.
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Affiliation(s)
- Patricia Cano-Sanchez
- Department of Chemistry, College of Staten Island and Macromolecular Assemblies Institute of the City University of New York, Staten Island, New York 10314, USA
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16
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Choi Y, Konopka JB. Accessibility of cysteine residues substituted into the cytoplasmic regions of the alpha-factor receptor identifies the intracellular residues that are available for G protein interaction. Biochemistry 2006; 45:15310-7. [PMID: 17176053 PMCID: PMC2528548 DOI: 10.1021/bi0614939] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The yeast alpha-factor pheromone receptor (Ste2) belongs to the family of G protein-coupled receptors (GPCRs) that contain seven transmembrane domains. To define the residues that are accessible to the cytoplasmic G protein, Cys scanning mutagenesis was carried out in which each of the residues that span the intracellular loops and the cytoplasmic end of transmembrane domain 7 was substituted with Cys. The 90 different Cys-substituted residues were then assayed for reactivity with MTSEA-biotin [[2-[(biotinoyl)amino]ethyl]methanethiosulfonate], which reacts with solvent-accessible sulfhydryl groups. As part of these studies we show that adding free Cys to stop the MTSEA-biotin reactions has potential pitfalls in that Cys can rapidly undergo disulfide exchange with the biotinylated receptor proteins at pH >or=7. The central regions of the intracellular loops of Ste2 were all highly accessible to MTSEA-biotin. Residues near the ends of the loops typically exhibited a drop in the level of reactivity over a consecutive series of residues that was inferred to be the membrane boundary. Interestingly, these boundary residues were enriched in hydrophobic residues, suggesting that they may form a hydrophobic pocket for interaction with the G protein. Comparison with accessibility data from a previous study of the extracellular side of Ste2 indicates that the transmembrane domains vary in length, consistent with some transmembrane domains being tilted relative to the plane of the membrane as they are in rhodopsin. Altogether, these results define the residues that are accessible to the G protein and provide an important structural framework for the interpretation of the role of Ste2 residues that function in G protein activation.
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Affiliation(s)
- Yunsook Choi
- Graduate Program in Physiology and Biophysics, State University of New York, Stony Brook, NY 11794-5222
| | - James B. Konopka
- Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, NY 11794-5222
- Corresponding Author: James B. Konopka Phone: 631-632-8715 FAX: 631-632-9797
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17
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Ringkananont U, Van Durme J, Montanelli L, Ugrasbul F, Yu YM, Weiss RE, Refetoff S, Grasberger H. Repulsive Separation of the Cytoplasmic Ends of Transmembrane Helices 3 and 6 Is Linked to Receptor Activation in a Novel Thyrotropin Receptor Mutant (M626I). Mol Endocrinol 2006; 20:893-903. [PMID: 16339276 DOI: 10.1210/me.2005-0339] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AbstractLigand-dependent activation of G protein-coupled receptors (GPCRs) involves repositioning of the juxtacytoplasmic ends of transmembrane helices TM3 and TM6. This concept, inferred from site-directed spin labeling studies, is supported by chemical cross-linking of the cytoplasmic ends of TM3 and TM6 blocking GPCR activation. Here we report a novel constitutive active mutation (M626I) in TM6 of the TSH receptor (TSHR), identified in affected members of a family with nonautoimmune hyperthyroidism. The specific constitutive activity of M626I, measured by its basal cAMP generation corrected for cell surface expression, was 13-fold higher than that of wild-type TSHR. Homology modeling of the TSHR serpentine domain based on the rhodopsin crystal structure suggests that M626 faces the side chain of I515 of TM3 near the membrane-cytoplasmic junction. Steric hindrance of the introduced isoleucine by I515 is consistent with the fact that shorter or more flexible side chains at position 626 did not increase constitutivity. Furthermore, a reciprocal mutation at position 515 (I515M), when introduced into the M626I background, acts as revertant mutation by allowing accommodation of the isoleucine sidechain at position 626 and fully restoring the constitutive activity to the level of wild-type TSHR. Thus, repulsive separation of the juxtacytoplasmic TM6 and TM3 in the M626I model conclusively demonstrates a direct link between the opening of this cytoplasmic face of the receptor structure and G protein coupling.
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Affiliation(s)
- Usanee Ringkananont
- Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA
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Overton MC, Chinault SL, Blumer KJ. Oligomerization of G-protein-coupled receptors: lessons from the yeast Saccharomyces cerevisiae. EUKARYOTIC CELL 2006; 4:1963-70. [PMID: 16339714 PMCID: PMC1317502 DOI: 10.1128/ec.4.12.1963-1970.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Mark C Overton
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110-1010, USA
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19
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Lee YH, Naider F, Becker JM. Interacting Residues in an Activated State of a G Protein-coupled Receptor. J Biol Chem 2006; 281:2263-72. [PMID: 16314417 DOI: 10.1074/jbc.m509987200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ste2p, the G protein-coupled receptor (GPCR) for the tridecapeptide pheromone alpha-factor of Saccharomyces cerevisiae, was used as a model GPCR to investigate the role of specific residues in the resting and activated states of the receptor. Using a series of biological and biochemical analyses of wild-type and site-directed mutant receptors, we identified Asn(205) as a potential interacting partner with the Tyr(266) residue. An N205H/Y266H double mutant showed pH-dependent functional activity, whereas the N205H receptor was non-functional and the Y266H receptor was partially active indicating that the histidine 205 and 266 residues interact in an activated state of the receptor. The introduction of N205K or Y266D mutations into the P258L/S259L constitutively active receptor suppressed the constitutive activity; in contrast, the N205K/Y266D/P258L/S259L quadruple mutant was fully constitutively active, again indicating an interaction between residues at the 205 and 206 positions in the receptor-active state. To further test this interaction, we introduced the N205C/Y266C, F204C/Y266C, and N205C/A265C double mutations into wild-type and P258L/S259L constitutively active receptors. After trypsin digestion, we found that a disulfide-cross-linked product, with the molecular weight expected for a receptor fragment with a cross-link between N205C and Y266C, formed only in the N205C/Y266C constitutively activated receptor. This study represents the first experimental demonstration of an interaction between specific residues in an active state, but not the resting state, of Ste2p. The information gained from this study should contribute to an understanding of the conformational differences between resting and active states in GPCRs.
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MESH Headings
- Alanine/chemistry
- Asparagine/chemistry
- Biological Assay
- Cross-Linking Reagents/pharmacology
- Disulfides/chemistry
- Dose-Response Relationship, Drug
- Genes, Dominant
- Genes, Reporter
- Histidine/chemistry
- Hydrogen-Ion Concentration
- Immunoblotting
- Kinetics
- Lac Operon
- Models, Biological
- Models, Molecular
- Mutagenesis, Site-Directed
- Mutation
- Phenotype
- Pheromones/chemistry
- Protein Binding
- Protein Conformation
- Protein Structure, Secondary
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Mating Factor/chemistry
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/chemistry
- Signal Transduction
- Trypsin/pharmacology
- Tyrosine/chemistry
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Affiliation(s)
- Yong-Hun Lee
- Department of Microbiology, University of Tennessee, Nashville, TN 37996, USA
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20
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Eilers M, Hornak V, Smith SO, Konopka JB. Comparison of class A and D G protein-coupled receptors: common features in structure and activation. Biochemistry 2005; 44:8959-75. [PMID: 15966721 PMCID: PMC1382269 DOI: 10.1021/bi047316u] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
All G protein-coupled receptors (GPCRs) share a common seven TM helix architecture and the ability to activate heterotrimeric G proteins. Nevertheless, these receptors have widely divergent sequences with no significant homology. We present a detailed structure-function comparison of the very divergent Class A and D receptors to address whether there is a common activation mechanism across the GPCR superfamily. The Class A and D receptors are represented by the vertebrate visual pigment rhodopsin and the yeast alpha-factor pheromone receptor Ste2, respectively. Conserved amino acids within each specific receptor class and amino acids where mutation alters receptor function were located in the structures of rhodopsin and Ste2 to assess whether there are functionally equivalent positions or regions within these receptors. We find several general similarities that are quite striking. First, strongly polar amino acids mediate helix interactions. Their mutation generally leads to loss of function or constitutive activity. Second, small and weakly polar amino acids facilitate tight helix packing. Third, proline is essential at similar positions in transmembrane helices 6 and 7 of both receptors. Mapping the specific location of the conserved amino acids and sites of constitutively active mutations identified conserved microdomains on transmembrane helices H3, H6, and H7, suggesting that there are underlying similarities in the mechanism of the widely divergent Class A and Class D receptors.
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Affiliation(s)
| | | | - Steven O. Smith
- * To whom correspondence should be addressed. Steven O. Smith, Center for Structural Biology Z = 5115, Stony Brook University, Stony Brook, NY 11794-5222. Tel., 631-632-1210; fax, 631-632-8575; e-mail,. James B. Konopka, Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222. Tel., 631-632-8715; fax, 631-632-8873; e-mail,
| | - James B. Konopka
- * To whom correspondence should be addressed. Steven O. Smith, Center for Structural Biology Z = 5115, Stony Brook University, Stony Brook, NY 11794-5222. Tel., 631-632-1210; fax, 631-632-8575; e-mail,. James B. Konopka, Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5222. Tel., 631-632-8715; fax, 631-632-8873; e-mail,
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21
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de Ligt RAF, Rivkees SA, Lorenzen A, Leurs R, IJzerman AP. A "locked-on," constitutively active mutant of the adenosine A1 receptor. Eur J Pharmacol 2005; 510:1-8. [PMID: 15740718 DOI: 10.1016/j.ejphar.2005.01.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 01/07/2005] [Indexed: 11/26/2022]
Abstract
We studied the wild-type human adenosine A1 receptor and three mutant receptors, in which the glycine at position 14 had been changed into an alanine, a leucine, or a threonine residue. All receptors were characterized in radioligand binding experiments, the wild-type and the Gly14Thr mutant receptor in greater detail. Both receptors were allosterically modulated by sodium ions and PD81,723 (2-amino-4,5-dimethyl-3-thienyl-[3(trifluoromethyl)-phenyl]methanone), although in a different way. All mutant receptors appeared to be spontaneously or "constitutively" active in a [35S]GTPgammaS binding assay, the first demonstration of the existence of such CAM (constitutively active mutant) receptors for the adenosine A1 receptor. The Gly14Thr mutant receptor was also constitutively active in another functional assay, i.e., the inhibition of forskolin-induced cAMP production in intact cells. Importantly, this mutant displayed a peculiar "locked-on" phenotype, i.e., neither agonist nor inverse agonist was capable of modulating the basal activity in both the GTPgammaS and the cAMP assay, unlike the wild-type and the two other mutant receptors.
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Affiliation(s)
- Rianne A F de Ligt
- Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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22
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Zhang M, Goswami M, Hereld D. Constitutively active G protein-coupled receptor mutants block dictyostelium development. Mol Biol Cell 2004; 16:562-72. [PMID: 15574880 PMCID: PMC545893 DOI: 10.1091/mbc.e04-06-0456] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
cAR1, a G protein-coupled receptor (GPCR) for cAMP, is required for the multicellular development of Dictyostelium. The activation of multiple pathways by cAR1 is transient because of poorly defined adaptation mechanisms. To investigate this, we used a genetic screen for impaired development to isolate four dominant-negative cAR1 mutants, designated DN1-4. The mutant receptors inhibit multiple cAR1-mediated responses known to undergo adaptation. Reduced in vitro adenylyl cyclase activation by GTPgammaS suggests that they cause constitutive adaptation of this and perhaps other pathways. In addition, the DN mutants are constitutively phosphorylated, which normally requires cAMP binding and possess cAMP affinities that are approximately 100-fold higher than that of wild-type cAR1. Two independent activating mutations, L100H and I104N, were identified. These residues occupy adjacent positions near the cytoplasmic end of the receptor's third transmembrane helix and correspond to the (E/D)RY motif of numerous mammalian GPCRs, which is believed to regulate their activation. Taken together, these findings suggest that the DN mutants are constitutively activated and block development by turning on natural adaptation mechanisms.
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Affiliation(s)
- Minghang Zhang
- Department of Microbiology and Molecular Genetics, The University of Texas Medical School at Houston, Houston, TX 77030, USA
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23
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Kristiansen K. Molecular mechanisms of ligand binding, signaling, and regulation within the superfamily of G-protein-coupled receptors: molecular modeling and mutagenesis approaches to receptor structure and function. Pharmacol Ther 2004; 103:21-80. [PMID: 15251227 DOI: 10.1016/j.pharmthera.2004.05.002] [Citation(s) in RCA: 392] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The superfamily of G-protein-coupled receptors (GPCRs) could be subclassified into 7 families (A, B, large N-terminal family B-7 transmembrane helix, C, Frizzled/Smoothened, taste 2, and vomeronasal 1 receptors) among mammalian species. Cloning and functional studies of GPCRs have revealed that the superfamily of GPCRs comprises receptors for chemically diverse native ligands including (1) endogenous compounds like amines, peptides, and Wnt proteins (i.e., secreted proteins activating Frizzled receptors); (2) endogenous cell surface adhesion molecules; and (3) photons and exogenous compounds like odorants. The combined use of site-directed mutagenesis and molecular modeling approaches have provided detailed insight into molecular mechanisms of ligand binding, receptor folding, receptor activation, G-protein coupling, and regulation of GPCRs. The vast majority of family A, B, C, vomeronasal 1, and taste 2 receptors are able to transduce signals into cells through G-protein coupling. However, G-protein-independent signaling mechanisms have also been reported for many GPCRs. Specific interaction motifs in the intracellular parts of these receptors allow them to interact with scaffold proteins. Protein engineering techniques have provided information on molecular mechanisms of GPCR-accessory protein, GPCR-GPCR, and GPCR-scaffold protein interactions. Site-directed mutagenesis and molecular dynamics simulations have revealed that the inactive state conformations are stabilized by specific interhelical and intrahelical salt bridge interactions and hydrophobic-type interactions. Constitutively activating mutations or agonist binding disrupts such constraining interactions leading to receptor conformations that associates with and activate G-proteins.
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Affiliation(s)
- Kurt Kristiansen
- Department of Pharmacology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
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24
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Cheo DL, Titus SA, Byrd DRN, Hartley JL, Temple GF, Brasch MA. Concerted assembly and cloning of multiple DNA segments using in vitro site-specific recombination: functional analysis of multi-segment expression clones. Genome Res 2004; 14:2111-20. [PMID: 15489333 PMCID: PMC528927 DOI: 10.1101/gr.2512204] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Accepted: 03/17/2004] [Indexed: 11/24/2022]
Abstract
The ability to clone and manipulate DNA segments is central to molecular methods that enable expression, screening, and functional characterization of genes, proteins, and regulatory elements. We previously described the development of a novel technology that utilizes in vitro site-specific recombination to provide a robust and flexible platform for high-throughput cloning and transfer of DNA segments. By using an expanded repertoire of recombination sites with unique specificities, we have extended the technology to enable the high-efficiency in vitro assembly and concerted cloning of multiple DNA segments into a vector backbone in a predefined order, orientation, and reading frame. The efficiency and flexibility of this approach enables collections of functional elements to be generated and mixed in a combinatorial fashion for the parallel assembly of numerous multi-segment constructs. The assembled constructs can be further manipulated by directing exchange of defined segments with alternate DNA segments. In this report, we demonstrate feasibility of the technology and application to the generation of fusion proteins, the linkage of promoters to genes, and the assembly of multiple protein domains. The technology has broad implications for cell and protein engineering, the expression of multidomain proteins, and gene function analysis.
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Affiliation(s)
- David L Cheo
- Atto Bioscience Inc., Rockville, Maryland 20850, USA
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25
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Chinault SL, Overton MC, Blumer KJ. Subunits of a Yeast Oligomeric G Protein-coupled Receptor Are Activated Independently by Agonist but Function in Concert to Activate G Protein Heterotrimers. J Biol Chem 2004; 279:16091-100. [PMID: 14764600 DOI: 10.1074/jbc.m311099200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors (GPCRs) form dimeric or oligomeric complexes in vivo. However, the function of oligomerization in receptor-mediated G protein activation is unclear. Previous studies of the yeast alpha-factor receptor (STE2 gene product) have indicated that oligomerization promotes signaling. Here we have addressed the mechanism by which oligomerization facilitates G protein signaling by examining the ability of ligand binding- and G protein coupling-defective alpha-factor receptors to form complexes in vivo and to correct their signaling defects when co-expressed (trans complementation). Newly and previously identified receptor mutants indicated that ligand binding involves the exofacial end of transmembrane domain (TM) 4, whereas G protein coupling involves ic1, ic3, the C-terminal tail, and the intracellular ends of TM2 and TM3. Mutant receptors bearing substitutions in these domains formed homo-oligomeric or hetero-oligomeric complexes in vivo, as indicated by results of fluorescence resonance energy transfer experiments. Co-expression of ligand binding- and G protein coupling-defective mutant receptors did not significantly improve signaling. In contrast, co-expression of ic1 and ic3 mutations in trans but not in cis significantly increased signaling efficiency. Therefore, we suggest that subunits of the alpha-factor receptor: 1) are activated independently rather than cooperatively by agonist, and 2) function in a concerted fashion to promote G protein activation, possibly by contacting different subunits or regions of the G protein heterotrimer.
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Affiliation(s)
- Sharon L Chinault
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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26
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Lin JC, Duell K, Konopka JB. A microdomain formed by the extracellular ends of the transmembrane domains promotes activation of the G protein-coupled alpha-factor receptor. Mol Cell Biol 2004; 24:2041-51. [PMID: 14966283 PMCID: PMC350546 DOI: 10.1128/mcb.24.5.2041-2051.2004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The alpha-factor receptor (Ste2p) that promotes mating in Saccharomyces cerevisiae is similar to other G protein-coupled receptors (GPCRs) in that it contains seven transmembrane domains. Previous studies suggested that the extracellular ends of the transmembrane domains are important for Ste2p function, so a systematic scanning mutagenesis was carried out in which 46 residues near the ends of transmembrane domains 1, 2, 3, 4, and 7 were replaced with cysteine. These mutants complement mutations constructed previously near the ends of transmembrane domains 5 and 6 to analyze all the extracellular ends. Eight new mutants created in this study were partially defective in signaling (V45C, N46C, T50C, A52C, L102C, N105C, L277C, and A281C). Treatment with 2-([biotinoyl] amino) ethyl methanethiosulfonate, a thiol-specific reagent that reacts with accessible cysteine residues but not membrane-embedded cysteines, identified a drop in the level of reactivity over a consecutive series of residues that was inferred to be the membrane boundary. An unusual prolonged zone of intermediate reactivity near the extracellular end of transmembrane domain 2 suggests that this region may adopt a special structure. Interestingly, residues implicated in ligand binding were mainly accessible, whereas residues involved in the subsequent step of promoting receptor activation were mainly inaccessible. These results define a receptor microdomain that provides an important framework for interpreting the mechanisms by which functionally important residues contribute to ligand binding and activation of Ste2p and other GPCRs.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- Biotin/chemistry
- Biotin/metabolism
- Cell Division/physiology
- Cysteine/metabolism
- Genes, Reporter
- Ligands
- Mesylates/chemistry
- Mesylates/metabolism
- Models, Molecular
- Mutation
- Phenotype
- Pheromones/metabolism
- Protein Binding
- Protein Structure, Secondary
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Mating Factor
- Receptors, Peptide/chemistry
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/chemistry
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
- Signal Transduction/physiology
- Transcription Factors
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Affiliation(s)
- Jennifer C Lin
- Graduate Program in Molecular and Cellular Biology, State University of New York, Stony Brook, New York 11794-5222, USA
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27
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Overton MC, Chinault SL, Blumer KJ. Oligomerization, Biogenesis, and Signaling Is Promoted by a Glycophorin A-like Dimerization Motif in Transmembrane Domain 1 of a Yeast G Protein-coupled Receptor. J Biol Chem 2003; 278:49369-77. [PMID: 14506226 DOI: 10.1074/jbc.m308654200] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors (GPCRs) can form dimeric or oligomeric complexes in vivo. However, the functions and mechanisms of oligomerization remain poorly understood for most GPCRs, including the alpha-factor receptor (STE2 gene product) of the yeast Saccharomyces cerevisiae. Here we provide evidence indicating that alpha-factor receptor oligomerization involves a GXXXG motif in the first transmembrane domain (TM1), similar to the transmembrane dimerization domain of glycophorin A. Results of fluorescence resonance energy transfer, fluorescence microscopy, endocytosis assays of receptor oligomerization in living cells, and agonist binding assays indicated that amino acid substitutions affecting the glycine residues of the GXXXG motif impaired alpha-factor receptor oligomerization and biogenesis in vivo but did not significantly impair agonist binding affinity. Mutant receptors exhibited signaling defects that were not due to impaired cell surface expression, indicating that oligomerization promotes alpha-factor receptor signal transduction. Structure-function studies suggested that the GXXXG motif in TM1 of the alpha-factor receptor promotes oligomerization by a mechanism similar to that used by the GXXXG dimerization motif of glycophorin A. In many mammalian GPCRs, motifs related to the GXXXG sequence are present in TM1 or other TM domains, suggesting that similar mechanisms are used by many GPCRs to form dimers or oligomeric arrays.
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Affiliation(s)
- Mark C Overton
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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28
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Parnot C, Miserey-Lenkei S, Bardin S, Corvol P, Clauser E. Lessons from constitutively active mutants of G protein-coupled receptors. Trends Endocrinol Metab 2002; 13:336-43. [PMID: 12217490 DOI: 10.1016/s1043-2760(02)00628-8] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In the past decade, the concept of constitutive activity has profoundly modified our understanding of G protein-coupled-receptors (GPCRs). Here, we review the contribution of constitutively active mutants (CAMs) to our understanding of three aspects of GPCR physiopathology: (1) GPCR activation is a complex mechanism involving both the release of inactive state conformational constraints, mimicked by most CAMs, and the creation of new interactions that stabilize the active state and are mimicked by a restricted set of CAMs; (2) GPCR phosphorylation, internalization and desensitization processes are activated by receptor conformations, which partly overlap those activating G protein; (3) natural CAMs, mostly affecting GPCRs of the endocrine system, are found in several hereditary and acquired diseases, including cancers. One major remaining question is how CAMs recapitulate the different structural modifications of the agonist-induced active conformation(s) of the wild-type receptor. This characterization is a prerequisite for further use of CAMs as ligand-free models of active GPCRs in structural, cellular and physiological studies.
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Affiliation(s)
- Charles Parnot
- INSERM U567, CNRS UMR8104, Institut Cochin, Faculté de Médecine Cochin, 24 rue du Fg St Jacques, F-75014 Paris, France
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