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Sridhar PS, Vasquez V, Monteil-Rivera F, Allingham JS, Loewen MC. A peroxidase-derived ligand that induces Fusarium graminearum Ste2 receptor-dependent chemotropism. Front Cell Infect Microbiol 2024; 13:1287418. [PMID: 38239502 PMCID: PMC10794396 DOI: 10.3389/fcimb.2023.1287418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 12/06/2023] [Indexed: 01/22/2024] Open
Abstract
Introduction The fungal G protein-coupled receptors Ste2 and Ste3 are vital in mediating directional hyphal growth of the agricultural pathogen Fusarium graminearum towards wheat plants. This chemotropism is induced by a catalytic product of peroxidases secreted by the wheat. Currently, the identity of this product, and the substrate it is generated from, are not known. Methods and results We provide evidence that a peroxidase substrate is derived from F. graminearum conidia and report a simple method to extract and purify the FgSte2-activating ligand for analyses by mass spectrometry. The mass spectra arising from t he ligand extract are characteristic of a 400 Da carbohydrate moiety. Consistent with this type of molecule, glycosidase treatment of F. graminearum conidia prior to peroxidase treatment significantly reduced the amount of ligand extracted. Interestingly, availability of the peroxidase substrate appears to depend on the presence of both FgSte2 and FgSte3, as knockout of one or the other reduces the chemotropism-inducing effect of the extracts. Conclusions While further characterization is necessary, identification of the F. graminearum-derived peroxidase substrate and the FgSte2-activating ligand will unearth deeper insights into the intricate mechanisms that underlie fungal pathogenesis in cereal crops, unveiling novel avenues for inhibitory interventions.
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Affiliation(s)
- Pooja S. Sridhar
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON, Canada
| | - Vinicio Vasquez
- National Research Council of Canada, Aquatic and Crop Resources Development, Montreal, QC, Canada
| | - Fanny Monteil-Rivera
- National Research Council of Canada, Aquatic and Crop Resources Development, Montreal, QC, Canada
| | - John S. Allingham
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON, Canada
| | - Michele C. Loewen
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON, Canada
- National Research Council of Canada, Aquatic and Crop Resources Development, Ottawa, ON, Canada
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2
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Sukumar M, DeFlorio R, Pai CY, Stone DE. A member of the claudin superfamily influences formation of the front domain in pheromone-responding yeast cells. J Cell Sci 2023; 136:286256. [PMID: 36601911 DOI: 10.1242/jcs.260048] [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: 04/20/2022] [Accepted: 12/19/2022] [Indexed: 01/06/2023] Open
Abstract
Cell polarization in response to chemical gradients is important in development and homeostasis across eukaryota. Chemosensing cells orient toward or away from gradient sources by polarizing along a front-rear axis. Using the mating response of budding yeast as a model of chemotropic cell polarization, we found that Dcv1, a member of the claudin superfamily, influences front-rear polarity. Although Dcv1 localized uniformly on the plasma membrane (PM) of vegetative cells, it was confined to the rear of cells responding to pheromone, away from the pheromone receptor. dcv1Δ conferred mislocalization of sensory, polarity and trafficking proteins, as well as PM lipids. These phenotypes correlated with defects in pheromone-gradient tracking and cell fusion. We propose that Dcv1 helps demarcate the mating-specific front domain primarily by restricting PM lipid distribution.
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Affiliation(s)
- Madhushalini Sukumar
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Reagan DeFlorio
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Chih-Yu Pai
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - David E Stone
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
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3
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A focus on yeast mating: From pheromone signaling to cell-cell fusion. Semin Cell Dev Biol 2023; 133:83-95. [PMID: 35148940 DOI: 10.1016/j.semcdb.2022.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 12/14/2022]
Abstract
Cells live in a chemical environment and are able to orient towards chemical cues. Unicellular haploid fungal cells communicate by secreting pheromones to reproduce sexually. In the yeast models Saccharomyces cerevisiae and Schizosaccharomyces pombe, pheromonal communication activates similar pathways composed of cognate G-protein-coupled receptors and downstream small GTPase Cdc42 and MAP kinase cascades. Local pheromone release and sensing, at a mobile surface polarity patch, underlie spatial gradient interpretation to form pairs between two cells of distinct mating types. Concentration of secretion at the point of cell-cell contact then leads to local cell wall digestion for cell fusion, forming a diploid zygote that prevents further fusion attempts. A number of asymmetries between mating types may promote efficiency of the system. In this review, we present our current knowledge of pheromone signaling in the two model yeasts, with an emphasis on how cells decode the pheromone signal spatially and ultimately fuse together. Though overall pathway architectures are similar in the two species, their large evolutionary distance allows to explore how conceptually similar solutions to a general biological problem can arise from divergent molecular components.
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Fusarium graminearum Ste3 G-Protein Coupled Receptor: A Mediator of Hyphal Chemotropism and Pathogenesis. mSphere 2022; 7:e0045622. [PMID: 36377914 PMCID: PMC9769807 DOI: 10.1128/msphere.00456-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Fungal hyphal chemotropism has been shown to be a major contributor to host-pathogen interactions. Previous studies on Fusarium species have highlighted the involvement of the Ste2 G-protein-coupled receptor (GPCR) in mediating polarized hyphal growth toward host-released peroxidase. Here, the role of the opposite mating type GPCR, Ste3, is characterized with respect to Fusarium graminearum chemotropism and pathogenicity. Fgste3Δ deletion strains were found to be compromised in the chemotropic response toward peroxidase, development of lesions on germinating wheat, and infection of Arabidopsis thaliana leaves. In the absence of FgSte3 or FgSte2, F. graminearum cells exposed to peroxidase showed no phosphorylation of the cell-wall integrity, mitogen-activated protein kinase pathway component Mgv1. In addition, transcriptomic gene expression profiling yielded a list of genes involved in cellular reorganization, cell wall remodeling, and infection-mediated responses that were differentially modulated by peroxidase when FgSte3 was present. Deletion of FgSte3 yielded the downregulation of genes associated with mycotoxin biosynthesis and appressorium development, compared to the wild-type strain, both in the presence of peroxidase. Together, these findings contribute to our understanding of the mechanism underlying fungal chemotropism and pathogenesis while raising the novel hypothesis that FgSte2 and FgSte3 are interdependent on each other for the mediation of the redirection of hyphal growth in response to host-derived peroxidase. IMPORTANCE Fusarium head blight of wheat, caused by the filamentous fungus Fusarium graminearum, leads to devastating global food shortages and economic losses. Fungal hyphal chemotropism has been shown to be a major contributor to host-pathogen interactions. Here, the role of the opposite mating type GPCR, Ste3, is characterized with respect to F. graminearum chemotropism and pathogenicity. These findings contribute to our understanding of the mechanisms underlying fungal chemotropism and pathogenesis.
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5
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Pheromone Guidance of Polarity Site Movement in Yeast. Biomolecules 2022; 12:biom12040502. [PMID: 35454091 PMCID: PMC9027094 DOI: 10.3390/biom12040502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 03/21/2022] [Accepted: 03/25/2022] [Indexed: 01/11/2023] Open
Abstract
Cells’ ability to track chemical gradients is integral to many biological phenomena, including fertilization, development, accessing nutrients, and combating infection. Mating of the yeast Saccharomyces cerevisiae provides a tractable model to understand how cells interpret the spatial information in chemical gradients. Mating yeast of the two different mating types secrete distinct peptide pheromones, called a-factor and α-factor, to communicate with potential partners. Spatial gradients of pheromones are decoded to guide mobile polarity sites so that polarity sites in mating partners align towards each other, as a prerequisite for cell-cell fusion and zygote formation. In ascomycetes including S. cerevisiae, one pheromone is prenylated (a-factor) while the other is not (α-factor). The difference in physical properties between the pheromones, combined with associated differences in mechanisms of secretion and extracellular pheromone metabolism, suggested that the pheromones might differ in the spatial information that they convey to potential mating partners. However, as mating appears to be isogamous in this species, it is not clear why any such signaling difference would be advantageous. Here we report assays that directly track movement of the polarity site in each partner as a way to understand the spatial information conveyed by each pheromone. Our findings suggest that both pheromones convey very similar information. We speculate that the different pheromones were advantageous in ancestral species with asymmetric mating systems and may represent an evolutionary vestige in yeasts that mate isogamously.
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6
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Abstract
Fungi exhibit an enormous variety of morphologies, including yeast colonies, hyphal mycelia, and elaborate fruiting bodies. This diversity arises through a combination of polar growth, cell division, and cell fusion. Because fungal cells are nonmotile and surrounded by a protective cell wall that is essential for cell integrity, potential fusion partners must grow toward each other until they touch and then degrade the intervening cell walls without impacting cell integrity. Here, we review recent progress on understanding how fungi overcome these challenges. Extracellular chemoattractants, including small peptide pheromones, mediate communication between potential fusion partners, promoting the local activation of core cell polarity regulators to orient polar growth and cell wall degradation. However, in crowded environments, pheromone gradients can be complex and potentially confusing, raising the question of how cells can effectively find their partners. Recent findings suggest that the cell polarity circuit exhibits searching behavior that can respond to pheromone cues through a remarkably flexible and effective strategy called exploratory polarization.
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7
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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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8
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Sridhar PS, Trofimova D, Subramaniam R, González-Peña Fundora D, Foroud NA, Allingham JS, Loewen MC. Ste2 receptor-mediated chemotropism of Fusarium graminearum contributes to its pathogenicity against wheat. Sci Rep 2020; 10:10770. [PMID: 32612109 PMCID: PMC7329813 DOI: 10.1038/s41598-020-67597-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/08/2020] [Indexed: 01/14/2023] Open
Abstract
Fusarium Head Blight of wheat, caused by the filamentous fungus Fusarium graminearum, leads to devastating global food shortages and economic losses. While many studies have addressed the responses of both wheat and F. graminearum during their interaction, the possibility of fungal chemotropic sensing enabling pathogenicity remains unexplored. Based on recent findings linking the pheromone-sensing G-protein-coupled receptor Ste2 to host-directed chemotropism in Fusarium oxysporum, we investigated the role of the Ste2 receptor and its downstream signaling pathways in mediating chemotropism of F. graminearum. Interestingly, a chemotropic response of growing hyphae towards catalytically active Triticum aestivum ‘Roblin’ cultivar secreted peroxidases was detected, with deletion of STE2 in F. graminearum leading to loss of the observed response. At the same time, deletion of STE2 significantly decreased infection on germinating wheat coleoptiles, highlighting an association between Ste2, chemotropism and infection by F. graminearum. Further characterization revealed that the peroxidase-directed chemotropism is associated with stimulation of the fungal cell wall integrity mitogen-activated protein kinase signaling cascade. Altogether, this study demonstrates conservation of Ste2-mediated chemotropism by Fusarium species, and its important role in mediating pathogenicity.
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Affiliation(s)
- Pooja S Sridhar
- Department of Biomedical and Molecular Sciences, Queen's University, 18 Stuart St., Kingston, ON, K7L 3N6, Canada
| | - Daria Trofimova
- Department of Biomedical and Molecular Sciences, Queen's University, 18 Stuart St., Kingston, ON, K7L 3N6, Canada
| | | | | | - Nora A Foroud
- Agriculture and Agri-Food Canada, 5403, 1st Avenue South, Lethbridge, AB, T1J 4B1, Canada
| | - John S Allingham
- Department of Biomedical and Molecular Sciences, Queen's University, 18 Stuart St., Kingston, ON, K7L 3N6, Canada
| | - Michele C Loewen
- Department of Biomedical and Molecular Sciences, Queen's University, 18 Stuart St., Kingston, ON, K7L 3N6, Canada. .,National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, K1A 0R6, Canada.
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9
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Martin SG. Molecular mechanisms of chemotropism and cell fusion in unicellular fungi. J Cell Sci 2019; 132:132/11/jcs230706. [PMID: 31152053 DOI: 10.1242/jcs.230706] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In all eukaryotic phyla, cell fusion is important for many aspects of life, from sexual reproduction to tissue formation. Fungal cells fuse during mating to form the zygote, and during vegetative growth to connect mycelia. Prior to fusion, cells first detect gradients of pheromonal chemoattractants that are released by their partner and polarize growth in their direction. Upon pairing, cells digest their cell wall at the site of contact and merge their plasma membrane. In this Review, I discuss recent work on the chemotropic response of the yeast models Saccharomyces cerevisiae and Schizosaccharomyces pombe, which has led to a novel model of gradient sensing: the cell builds a motile cortical polarized patch, which acts as site of communication where pheromones are released and sensed. Initial patch dynamics serve to correct its position and align it with the gradient from the partner cell. Furthermore, I highlight the transition from cell wall expansion during growth to cell wall digestion, which is imposed by physical and signaling changes owing to hyperpolarization that is induced by cell proximity. To conclude, I discuss mechanisms of membrane fusion, whose characterization remains a major challenge for the future.
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Affiliation(s)
- Sophie G Martin
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
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10
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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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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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12
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13
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Choudhary P, Loewen MC. Evidence of a role for S. cerevisiae α-arrestin Art1 (Ldb19) in mating projection and zygote formations. Cell Biol Int 2015; 40:83-90. [PMID: 26314564 DOI: 10.1002/cbin.10541] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 08/22/2015] [Indexed: 01/08/2023]
Abstract
The discovery of arrestin-mediated biased signalling mechanisms for mammalian G-protein coupled receptors (GPCRs) has revolutionized the field over the last decade. Now, with the recent demonstration of a role for α-arrestins in internalization of the yeast pheromone GPCR, Ste2p, the possibility of arrestin-mediated alternate GPCR functionalities in yeast also follows. Here, the effects of knockout and complementation of yeast α-arrestin expression during mating are reported. Although minor effects on classical pheromone-related signalling are noted for a few arrestins, much stronger effects were observed downstream of cell cycle arrest, in particular linking Ldb19 (Art1) to mediation of zygote formation. Subsequent phenotypic observations linked this activity to more pronounced projection formation in an Art1 complemented noncuple α-arrestin knockout line, compared to the knockout-line alone, or either of the Art3 or Art6 complemented lines. Together with the observation of ligand-stimulated localization of Art-GFP to the mating projection, a possible role for this arrestin-like protein in projection formation is supported. While leaving the full mechanism of alternate Art1 functionality to be elucidated, together these findings implicate Art1 in selective regulation of mating events downstream of receptor internalization and cell cycle arrest, leading to schmoo, and ultimately zygote formation.
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Affiliation(s)
- Pooja Choudhary
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Rd., Saskatoon, S7N 5E5, Saskatchewan, Canada
| | - Michele C Loewen
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Rd., Saskatoon, S7N 5E5, Saskatchewan, Canada.,National Research Council of Canada, 110 Gymnasium Place, Saskatoon, S7N 0W9, Saskatchewan, Canada
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Choudhary P, Loewen MC. Quantification of mutation-derived bias for alternate mating functionalities of the Saccharomyces cerevisiae Ste2p pheromone receptor. J Biochem 2015; 159:49-58. [PMID: 26232403 DOI: 10.1093/jb/mvv072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/15/2015] [Indexed: 01/14/2023] Open
Abstract
Although well documented for mammalian G-protein-coupled receptors, alternate functionalities and associated alternate signalling remain to be unequivocally established for the Saccharomyces cerevisiae pheromone Ste2p receptor. Here, evidence supporting alternate functionalities for Ste2p is re-evaluated, extended and quantified. In particular, strong mating and constitutive signalling mutations, focusing on residues S254, P258 and S259 in TM6 of Ste2p, are stacked and investigated in terms of their effects on classical G-protein-mediated signal transduction associated with cell cycle arrest, and alternatively, their impact on downstream mating projection and zygote formation events. In relative dose response experiments, accounting for systemic and observational bias, mutational-derived functional differences were observed, validating the S254L-derived bias for downstream mating responses and highlighting complex relationships between TM6-mutation derived constitutive signalling and ligand-induced functionalities. Mechanistically, localization studies suggest that alterations to receptor trafficking may contribute to mutational bias, in addition to expected receptor conformational stabilization effects. Overall, these results extend previous observations and quantify the contributions of Ste2p variants to mediating cell cycle arrest versus downstream mating functionalities.
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Affiliation(s)
- Pooja Choudhary
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada and
| | - Michele C Loewen
- Department of Biochemistry, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada and Aquatic and Crop Resources Development, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada
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15
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Fracchiolla KE, Cohen LS, Arshava B, Poms M, Zerbe O, Becker JM, Naider F. Structural characterization of triple transmembrane domain containing fragments of a yeast G protein-coupled receptor in an organic : aqueous environment by solution-state NMR spectroscopy. J Pept Sci 2015; 21:212-22. [PMID: 25645975 DOI: 10.1002/psc.2750] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 12/26/2014] [Accepted: 12/28/2014] [Indexed: 01/09/2023]
Abstract
This report summarizes recent biophysical and protein expression experiments on polypeptides containing the N-terminus, the first, second, and third transmembrane (TM) domains and the contiguous loops of the α-factor receptor Ste2p, a G protein-coupled receptor. The 131-residue polypeptide Ste2p(G31-R161), TM1-TM3, was investigated by solution NMR in trifluoroethanol/water. TM1-TM3 contains helical TM domains at the predicted locations, supported by continuous sets of medium-range NOEs. In addition, a short helix N-terminal to TM1 was detected, as well as a short helical stretch in the first extracellular loop. Two 161-residue polypeptides, [Ste2p(M1-R161), NT-TM1-TM3], that contain the entire N-terminal sequence, one with a single mutation, were directly expressed and isolated from Escherichia coli in yields as high as 30 mg/L. Based on its increased stability, the L11P mutant will be used in future experiments to determine long-range interactions. The study demonstrated that 3-TM domains of a yeast G protein-coupled receptor can be produced in isotopically labeled form suitable for solution NMR studies. The quality of spectra is superior to data recorded in micelles and allows more rapid data analysis. No tertiary contacts have been determined, and if present, they are likely transient. This observation supports earlier studies by us that secondary structure was retained in smaller fragments, both in organic solvents and in detergent micelles, but that stable tertiary contacts may only be present when the protein is imbedded in lipids.
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Affiliation(s)
- Katrina E Fracchiolla
- Department of Chemistry, The College of Staten Island, City University of New York, Staten Island, NY, 10314, USA; Department of Biochemistry, The Graduate Center, City University of New York, New York, NY, 10016, USA
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16
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One motif to bind them: A small-XXX-small motif affects transmembrane domain 1 oligomerization, function, localization, and cross-talk between two yeast GPCRs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:3036-51. [DOI: 10.1016/j.bbamem.2014.08.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/13/2014] [Accepted: 08/14/2014] [Indexed: 12/21/2022]
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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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18
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Abstract
Many cells are able to orient themselves in a non-uniform environment by responding to localized cues. This leads to a polarized cellular response, where the cell can either grow or move towards the cue source. Fungal haploid cells secrete pheromones to signal mating, and respond by growing a mating projection towards a potential mate. Upon contact of the two partner cells, these fuse to form a diploid zygote. In this review, we present our current knowledge on the processes of mating signalling, pheromone-dependent polarized growth and cell fusion in Saccharomyces cerevisiae and Schizosaccharomyces pombe, two highly divergent ascomycete yeast models. While the global architecture of the mating response is very similar between these two species, they differ significantly both in their mating physiologies and in the molecular connections between pheromone perception and downstream responses. The use of both yeast models helps enlighten both conserved solutions and species-specific adaptations to a general biological problem.
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Affiliation(s)
- Laura Merlini
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne 1015, Switzerland
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Uddin MS, Kim H, Deyo A, Naider F, Becker JM. Identification of residues involved in homodimer formation located within a β-strand region of the N-terminus of a Yeast G protein-coupled receptor. J Recept Signal Transduct Res 2012; 32:65-75. [PMID: 22268895 DOI: 10.3109/10799893.2011.647352] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
G protein-coupled receptors (GPCRs) are members of a superfamily of cell surface signaling proteins that play critical roles in many physiological functions; malfunction of these proteins is associated with multiple diseases. Understanding the structure-function relationships of these proteins is important, therefore, for GPCR-based drug discovery. The yeast Saccharomyces cerevisiae tridecapeptide pheromone α-factor receptor Ste2p has been studied as a model to explore the structure-function relationships of this important class of cell surface receptors. Although transmembrane domains of GPCRs have been examined extensively, the extracellular N-terminus and loop regions have received less attention. We have used substituted cysteine accessibility method to probe the solvent accessibility of single cysteine residues engineered to replace residues Gly20 through Gly33 of the N-terminus of Ste2p. Unexpectedly, our analyses revealed that the residues Ser22, Ile24, Tyr26, and Ser28 in the N-terminus were solvent inaccessible, whereas all other residues of the targeted region were solvent accessible. The periodicity of accessibility from residues Ser22-Ser28 is indicative of an underlying structure consistent with a β-strand that was predicted computationally in this region. Moreover, a number of these Cys-substituted Ste2p receptors (G20C, S22C, I24C, Y26C, S28C and Y30C) were found to form increased dimers compared to the Cys-less Ste2p. Based on these data, we propose that part of the N-terminus of Ste2p is structured and that this structure forms a dimer interface for Ste2p molecules. Dimerization mediated by the N-terminus was affected by ligand binding, indicating an unanticipated conformational change in the N-terminus upon receptor activation.
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Affiliation(s)
- M Seraj Uddin
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
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Jin M, Errede B, Behar M, Mather W, Nayak S, Hasty J, Dohlman HG, Elston TC. Yeast dynamically modify their environment to achieve better mating efficiency. Sci Signal 2011; 4:ra54. [PMID: 21868361 DOI: 10.1126/scisignal.2001763] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The maintenance and detection of signaling gradients are critical for proper development and cell migration. In single-cell organisms, gradient detection allows cells to orient toward a distant mating partner or nutrient source. Budding yeast expand their growth toward mating pheromone gradients through a process known as chemotropic growth. MATα cells secrete α-factor pheromone that stimulates chemotropism and mating differentiation in MATa cells and vice versa. Paradoxically, MATa cells secrete Bar1, a protease that degrades α-factor and that attenuates the mating response, yet is also required for efficient mating. We observed that MATa cells avoid each other during chemotropic growth. To explore this behavior, we developed a computational platform to simulate chemotropic growth. Our simulations indicated that the release of Bar1 enabled individual MATa cells to act as α-factor sinks. The simulations suggested that the resultant local reshaping of pheromone concentration created gradients that were directed away from neighboring MATa cells (self-avoidance) and that were increasingly amplified toward partners of the opposite sex during elongation. The behavior of Bar1-deficient cells in gradient chambers and mating assays supported these predictions from the simulations. Thus, budding yeast dynamically remodel their environment to ensure productive responses to an external stimulus and avoid nonproductive cell-cell interactions.
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Affiliation(s)
- Meng Jin
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
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21
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Xu B, Lin H, Yang Z. Ontology integration to identify protein complex in protein interaction networks. Proteome Sci 2011; 9 Suppl 1:S7. [PMID: 22165991 PMCID: PMC3289085 DOI: 10.1186/1477-5956-9-s1-s7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Protein complexes can be identified from the protein interaction networks derived from experimental data sets. However, these analyses are challenging because of the presence of unreliable interactions and the complex connectivity of the network. The integration of protein-protein interactions with the data from other sources can be leveraged for improving the effectiveness of protein complexes detection algorithms. METHODS We have developed novel semantic similarity method, which use Gene Ontology (GO) annotations to measure the reliability of protein-protein interactions. The protein interaction networks can be converted into a weighted graph representation by assigning the reliability values to each interaction as a weight. Following the approach of that of the previously proposed clustering algorithm IPCA which expands clusters starting from seeded vertices, we present a clustering algorithm OIIP based on the new weighted Protein-Protein interaction networks for identifying protein complexes. RESULTS The algorithm OIIP is applied to the protein interaction network of Sacchromyces cerevisiae and identifies many well known complexes. Experimental results show that the algorithm OIIP has higher F-measure and accuracy compared to other competing approaches.
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Affiliation(s)
- Bo Xu
- Department of Computer Science and Engineering, Dalian University of Technology, Dalian, China.
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Caroccia KE, Estephan R, Cohen LS, Arshava B, Hauser M, Zerbe O, Becker JM, Naider F. Expression and biophysical analysis of a triple-transmembrane domain-containing fragment from a yeast G protein-coupled receptor. Biopolymers 2011; 96:757-71. [DOI: 10.1002/bip.21614] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
The genome sequences of the basidiomycete Agaricomycetes species Coprinopsis cinerea, Laccaria bicolor, Schizophyllum commune, Phanerochaete chrysosporium, and Postia placenta, as well as of Cryptococcus neoformans and Ustilago maydis, are now publicly available. Out of these fungi, C. cinerea, S. commune, and U. maydis, together with the budding yeast Saccharomyces cerevisiae, have been investigated for years genetically and molecularly for signaling in sexual reproduction. The comparison of the structure and organization of mating type genes in fungal genomes reveals an amazing conservation of genes regulating the sexual reproduction throughout the fungal kingdom. In agaricomycetes, two mating type loci, A, coding for homeodomain type transcription factors, and B, encoding a pheromone/receptor system, regulate the four typical mating interactions of tetrapolar species. Evidence for both A and B mating type genes can also be identified in basidiomycetes with bipolar systems, where only two mating interactions are seen. In some of these fungi, the B locus has lost its self/nonself discrimination ability and thus its specificity while retaining the other regulatory functions in development. In silico analyses now also permit the identification of putative components of the pheromone-dependent signaling pathways. Induction of these signaling cascades leads to development of dikaryotic mycelia, fruiting body formation, and meiotic spore production. In pheromone-dependent signaling, the role of heterotrimeric G proteins, components of a mitogen-activated protein kinase (MAPK) cascade, and cyclic AMP-dependent pathways can now be defined. Additionally, the pheromone-dependent signaling through monomeric, small GTPases potentially involved in creating the polarized cytoskeleton for reciprocal nuclear exchange and migration during mating is predicted.
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Chen L, Shi X, Kong X, Zeng Z, Cai YD. Identifying Protein Complexes Using Hybrid Properties. J Proteome Res 2009; 8:5212-8. [DOI: 10.1021/pr900554a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lei Chen
- Institute of Systems Biology, Shanghai University, Shanghai 200444, People’s Republic of China, Centre for Computational Systems Biology, Fudan University, Shanghai 200433, People’s Republic of China, Shanghai Key Laboratory of Trustworthy Computing, East China Normal University, Shanghai 200062, People’s Republic of China, and Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, Shanghai 200025,
| | - Xiaohe Shi
- Institute of Systems Biology, Shanghai University, Shanghai 200444, People’s Republic of China, Centre for Computational Systems Biology, Fudan University, Shanghai 200433, People’s Republic of China, Shanghai Key Laboratory of Trustworthy Computing, East China Normal University, Shanghai 200062, People’s Republic of China, and Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, Shanghai 200025,
| | - Xiangyin Kong
- Institute of Systems Biology, Shanghai University, Shanghai 200444, People’s Republic of China, Centre for Computational Systems Biology, Fudan University, Shanghai 200433, People’s Republic of China, Shanghai Key Laboratory of Trustworthy Computing, East China Normal University, Shanghai 200062, People’s Republic of China, and Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, Shanghai 200025,
| | - Zhenbing Zeng
- Institute of Systems Biology, Shanghai University, Shanghai 200444, People’s Republic of China, Centre for Computational Systems Biology, Fudan University, Shanghai 200433, People’s Republic of China, Shanghai Key Laboratory of Trustworthy Computing, East China Normal University, Shanghai 200062, People’s Republic of China, and Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, Shanghai 200025,
| | - Yu-Dong Cai
- Institute of Systems Biology, Shanghai University, Shanghai 200444, People’s Republic of China, Centre for Computational Systems Biology, Fudan University, Shanghai 200433, People’s Republic of China, Shanghai Key Laboratory of Trustworthy Computing, East China Normal University, Shanghai 200062, People’s Republic of China, and Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, Shanghai 200025,
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Shi C, Kendall SC, Grote E, Kaminskyj S, Loewen MC. N-terminal residues of the yeast pheromone receptor, Ste2p, mediate mating events independently of G1-arrest signaling. J Cell Biochem 2009; 107:630-8. [DOI: 10.1002/jcb.22129] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Neumoin A, Cohen LS, Arshava B, Tantry S, Becker JM, Zerbe O, Naider F. Structure of a double transmembrane fragment of a G-protein-coupled receptor in micelles. Biophys J 2009; 96:3187-96. [PMID: 19383463 DOI: 10.1016/j.bpj.2009.01.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 01/08/2009] [Accepted: 01/13/2009] [Indexed: 11/29/2022] Open
Abstract
The structure and dynamic properties of an 80-residue fragment of Ste2p, the G-protein-coupled receptor for alpha-factor of Saccharomyces cerevisiae, was studied in LPPG micelles with the use of solution NMR spectroscopy. The fragment Ste2p(G31-T110) (TM1-TM2) consisted of 19 residues from the N-terminal domain, the first TM helix (TM1), the first cytoplasmic loop, the second TM helix (TM2), and seven residues from the first extracellular loop. Multidimensional NMR experiments on [(15)N], [(15)N, (13)C], [(15)N, (13)C, (2)H]-labeled TM1-TM2 and on protein fragments selectively labeled at specific amino acid residues or protonated at selected methyl groups resulted in >95% assignment of backbone and side-chain nuclei. The NMR investigation revealed the secondary structure of specific residues of TM1-TM2. TALOS constraints and NOE connectivities were used to calculate a structure for TM1-TM2 that was highlighted by the presence of three alpha-helices encompassing residues 39-47, 49-72, and 80-103, with higher flexibility around the internal Arg(58) site of TM1. RMSD values of individually superimposed helical segments 39-47, 49-72, and 80-103 were 0.25 +/- 0.10 A, 0.40 +/- 0.13 A, and 0.57 +/- 0.19 A, respectively. Several long-range interhelical connectivities supported the folding of TM1-TM2 into a tertiary structure typified by a crossed helix that splays apart toward the extracellular regions and contains considerable flexibility in the G(56)VRSG(60) region. (15)N-relaxation and hydrogen-deuterium exchange data support a stable fold for the TM parts of TM1-TM2, whereas the solvent-exposed segments are more flexible. The NMR structure is consistent with the results of biochemical experiments that identified the ligand-binding site within this region of the receptor.
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Affiliation(s)
- Alexey Neumoin
- Institute of Organic Chemistry, University of Zurich, Zurich, Switzerland
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Hsueh YP, Xue C, Heitman J. A constitutively active GPCR governs morphogenic transitions in Cryptococcus neoformans. EMBO J 2009; 28:1220-33. [PMID: 19322200 DOI: 10.1038/emboj.2009.68] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 02/23/2009] [Indexed: 11/09/2022] Open
Abstract
Sex in fungi is driven by peptide pheromones sensed through seven-transmembrane pheromone receptors. In Cryptococcus neoformans, sexual reproduction occurs through an outcrossing/heterothallic a- sexual cycle or an inbreeding/homothallic - unisexual mating process. Pheromone receptors encoded by the mating-type locus (MAT) mediate reciprocal pheromone sensing during opposite-sex mating and contribute to but are not essential for unisexual mating. A pheromone receptor-like gene, CPR2, was discovered that is not encoded by MAT and whose expression is induced during a- mating. cpr2 mutants are fertile but have a fusion defect and produce abnormal hyphal structures, whereas CPR2 overexpression elicits unisexual reproduction. When heterologously expressed in Saccharomyces cerevisiae, Cpr2 activates pheromone responses in the absence of any ligand. This constitutive activity results from an unconventional residue, Leu(222), in place of a conserved proline in transmembrane domain six; a Cpr2(L222P) mutant is no longer constitutively active. Cpr2 engages the same G-protein activated signalling cascade as the Ste3a/alpha pheromone receptors, and thereby competes for pathway activation. This study established a new paradigm in which a naturally occurring constitutively active G protein-coupled receptor governs morphogenesis in fungi.
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Affiliation(s)
- Yen-Ping Hsueh
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA
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Panetta R, Greenwood MT. Physiological relevance of GPCR oligomerization and its impact on drug discovery. Drug Discov Today 2008; 13:1059-66. [DOI: 10.1016/j.drudis.2008.09.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 08/21/2008] [Accepted: 09/01/2008] [Indexed: 12/20/2022]
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Rich RL, Myszka DG. Survey of the year 2007 commercial optical biosensor literature. J Mol Recognit 2008; 21:355-400. [DOI: 10.1002/jmr.928] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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In vitro characterization of ligand-induced oligomerization of the S. cerevisiae G-protein coupled receptor, Ste2p. Biochim Biophys Acta Gen Subj 2008; 1790:1-7. [PMID: 18996443 DOI: 10.1016/j.bbagen.2008.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2008] [Revised: 10/10/2008] [Accepted: 10/10/2008] [Indexed: 01/17/2023]
Abstract
BACKGROUND The S. cerevisiae alpha-factor receptor, Ste2p, is a G-protein coupled receptor that plays key roles in yeast signaling and mating. Oligomerization of Ste2p has previously been shown to be important for intracellular trafficking, receptor processing and endocytosis. However the role of ligand in receptor oligomerization remains enigmatic. METHODS Using functional recombinant forms of purified Ste2p, atomic force microscopy, dynamic light scattering and chemical crosslinking are applied to investigate the role of ligand in Ste2p oligomerization. RESULTS Atomic force microscopy images indicate a molecular height for recombinant Ste2p in the presence of alpha-factor nearly double that of Ste2p alone. This observation is supported by complementary dynamic light scattering measurements which indicate a ligand-induced increase in the polydispersity of the Ste2p hydrodynamic radius. Finally, chemical cross-linking of HEK293 plasma membranes presenting recombinant Ste2p indicates alpha-factor induced stabilization of the dimeric form and higher order oligomeric forms of the receptor upon SDS-PAGE analysis. CONCLUSIONS alpha-factor induces oligomerization of Ste2p in vitro and in membrane. GENERAL SIGNIFICANCE These results provide additional evidence of a possible role for ligand in mediation of Ste2p oligomerization in vivo.
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Shpakov AO, Pertseva MN. Chapter 4 Signaling Systems of Lower Eukaryotes and Their Evolution. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 269:151-282. [DOI: 10.1016/s1937-6448(08)01004-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Identification of a minimal cre1 promoter sequence promoting glucose-dependent gene expression in the beta-lactam producer Acremonium chrysogenum. Curr Genet 2007; 53:35-48. [PMID: 18040688 DOI: 10.1007/s00294-007-0164-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 10/30/2007] [Accepted: 11/04/2007] [Indexed: 10/22/2022]
Abstract
The promoter of the cre1 gene, encoding the glucose-dependent regulator CRE1 from the beta-lactam producer Acremonium chrysogenum, carries 15 putative CRE1 binding sites (BS1 to BS15). For a detailed analysis, we fused cre1 promoter deletion derivatives with the DsRed reporter gene to perform a comparative gene expression analysis. Plate assays, Northern hybridizations, and spectrofluorometric measurements of DsRed identified the minimal D4 promoter sequence that promoted glucose-dependent expression. Truncated recombinant CRE1 interacted with D4 in electromobility shift analysis and these binding studies were further extended with two oligonucleotides, carrying putative CRE1 binding sites BS14 and BS15. Surface plasmon resonance analysis was performed using BS14 and BS15, along with four derivatives containing 2 or 4 bp substitutions within BS14 and BS15, respectively. Substitutions within BS14 abolished the high affinity interaction with CRE1, while mutations in BS15 only marginally diminished the affinity with CRE1. In vivo analysis of a modified D4 sequence with substitutions in the two binding sites confirmed the in vitro binding results and still promoted glucose-dependent gene expression. Our results will contribute to the construction of versatile expression vectors carrying a minimal cre1 promoter sequence that still confers glucose-dependent induction of gene expression.
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Cell fusion during development. Trends Cell Biol 2007; 17:537-46. [PMID: 17981036 DOI: 10.1016/j.tcb.2007.09.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Revised: 09/07/2007] [Accepted: 09/07/2007] [Indexed: 11/21/2022]
Abstract
Most readers of this review originated from a sperm-egg fusion event. Cell fusion is a process that is crucial at many intersections later during development. However, we do not know which molecules (fusogens) fuse the membranes of gametes to form zygotes, myoblasts to form myotubes in muscles, macrophages to form osteoclasts in bones, or cytotrophoblasts to form syncytiotrophoblasts in placentas. There are five gold standards that can be applied for the identification of genuine fusogens. Based on these criteria, a numerical score can be used to assess the likelihood of protein fusogenicity. We compare distinct families of candidate developmental, viral and intracellular fusogens and analyze current models of membrane fusion.
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Current awareness on yeast. Yeast 2007. [DOI: 10.1002/yea.1575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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