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Schlarmann P, Sakuragi K, Ikeda A, Yang Y, Sasaki S, Hanaoka K, Araki M, Shibata T, Kanai M, Funato K. The tricalbin family of membrane contact site tethers is involved in the transcriptional responses of Saccharomyces cerevisiae to glucose. J Biol Chem 2024; 300:107665. [PMID: 39128724 PMCID: PMC11408865 DOI: 10.1016/j.jbc.2024.107665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 07/24/2024] [Accepted: 08/05/2024] [Indexed: 08/13/2024] Open
Abstract
Cellular organelles maintain areas of close apposition with other organelles at which the cytosolic gap in between them is reduced to a minimum. These membrane contact sites (MCS) are vital for organelle communication and are formed by molecular tethers that physically connect opposing membranes. Although many regulatory pathways are known to converge at MCS, a link between MCS and transcriptional regulation-the primary mechanism through which cells adapt their metabolism to environmental cues-remains largely elusive. In this study, we performed RNA-sequencing on Saccharomyces cerevisiae cells lacking tricalbin proteins (Tcb1, Tcb2, and Tcb3), a family of tethering proteins that connect the endoplasmic reticulum with the plasma membrane and Golgi, to investigate if gene expression is altered when MCS are disrupted. Our results indicate that in the tcb1Δ2Δ3Δ strain, pathways responsive to a high-glucose environment, including glycolysis, fermentation, amino acid synthesis, and low-affinity glucose uptake, are upregulated. Conversely, pathways crucial during glucose depletion, such as the tricarboxylic acid cycle, respiration, high-affinity glucose uptake, and amino acid uptake are downregulated. In addition, we demonstrate that the altered gene expression of tcb1Δ2Δ3Δ in glucose metabolism correlates with increased growth, glucose consumption, CO2 production, and ethanol generation. In conclusion, our findings reveal that tricalbin protein deletion induces a shift in gene expression patterns mimicking cellular responses to a high-glucose environment. This suggests that MCS play a role in sensing and signaling pathways that modulate gene transcription in response to glucose availability.
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Affiliation(s)
- Philipp Schlarmann
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Keiko Sakuragi
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Atsuko Ikeda
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Yujia Yang
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Saku Sasaki
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Kazuki Hanaoka
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Misako Araki
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Tomoko Shibata
- National Research Institute of Brewing, Higashi-Hiroshima, Japan
| | - Muneyoshi Kanai
- National Research Institute of Brewing, Higashi-Hiroshima, Japan
| | - Kouichi Funato
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan.
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2
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Botman D, Kanagasabapathi S, Rep MI, van Rossum K, Tutucci E, Teusink B. cAMP in budding yeast: Also a messenger for sucrose metabolism? BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119706. [PMID: 38521467 DOI: 10.1016/j.bbamcr.2024.119706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 02/28/2024] [Accepted: 03/04/2024] [Indexed: 03/25/2024]
Abstract
S. cerevisiae (or budding yeast) is an important micro-organism for sucrose-based fermentation in biotechnology. Yet, it is largely unknown how budding yeast adapts to sucrose transitions. Sucrose can only be metabolized when the invertase or the maltose machinery are expressed and we propose that the Gpr1p receptor signals extracellular sucrose availability via the cAMP peak to adapt cells accordingly. A transition to sucrose or glucose gave a transient cAMP peak which was maximally induced for sucrose. When transitioned to sucrose, cAMP signalling mutants showed an impaired cAMP peak together with a lower growth rate, a longer lag phase and a higher final OD600 compared to a glucose transition. These effects were not caused by altered activity or expression of enzymes involved in sucrose metabolism and imply a more general metabolic adaptation defect. Basal cAMP levels were comparable among the mutant strains, suggesting that the transient cAMP peak is required to adapt cells correctly to sucrose. We propose that the short-term dynamics of the cAMP signalling cascade detects long-term extracellular sucrose availability and speculate that its function is to maintain a fermentative phenotype at continuously low glucose and fructose concentrations.
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Affiliation(s)
- Dennis Botman
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands.
| | - Sineka Kanagasabapathi
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
| | - Mila I Rep
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
| | - Kelly van Rossum
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
| | - Evelina Tutucci
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
| | - Bas Teusink
- Systems Biology Lab, AIMMS/ALIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands.
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3
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Simpson-Lavy K, Kupiec M. Glucose Inhibits Yeast AMPK (Snf1) by Three Independent Mechanisms. BIOLOGY 2023; 12:1007. [PMID: 37508436 PMCID: PMC10376661 DOI: 10.3390/biology12071007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 07/13/2023] [Accepted: 07/13/2023] [Indexed: 07/30/2023]
Abstract
Snf1, the fungal homologue of mammalian AMP-dependent kinase (AMPK), is a key protein kinase coordinating the response of cells to a shortage of glucose. In fungi, the response is to activate respiratory gene expression and metabolism. The major regulation of Snf1 activity has been extensively investigated: In the absence of glucose, it becomes activated by phosphorylation of its threonine at position 210. This modification can be erased by phosphatases when glucose is restored. In the past decade, two additional independent mechanisms of Snf1 regulation have been elucidated. In response to glucose (or, surprisingly, also to DNA damage), Snf1 is SUMOylated by Mms21 at lysine 549. This inactivates Snf1 and leads to Snf1 degradation. More recently, glucose-induced proton export has been found to result in Snf1 inhibition via a polyhistidine tract (13 consecutive histidine residues) at the N-terminus of the Snf1 protein. Interestingly, the polyhistidine tract plays also a central role in the response to iron scarcity. This review will present some of the glucose-sensing mechanisms of S. cerevisiae, how they interact, and how their interplay results in Snf1 inhibition by three different, and independent, mechanisms.
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Affiliation(s)
- Kobi Simpson-Lavy
- The Shmunis School of Biomedicine & Cancer Research, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Martin Kupiec
- The Shmunis School of Biomedicine & Cancer Research, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
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4
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Botman D, Kanagasabapathi S, Savakis P, Teusink B. Using the AKAR3-EV biosensor to assess Sch9p- and PKA-signalling in budding yeast. FEMS Yeast Res 2023; 23:foad029. [PMID: 37173282 PMCID: PMC10237333 DOI: 10.1093/femsyr/foad029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 05/01/2023] [Accepted: 05/10/2023] [Indexed: 05/15/2023] Open
Abstract
Budding yeast uses the TORC1-Sch9p and cAMP-PKA signalling pathways to regulate adaptations to changing nutrient environments. Dynamic and single-cell measurements of the activity of these cascades will improve our understanding of the cellular adaptation of yeast. Here, we employed the AKAR3-EV biosensor developed for mammalian cells to measure the cellular phosphorylation status determined by Sch9p and PKA activity in budding yeast. Using various mutant strains and inhibitors, we show that AKAR3-EV measures the Sch9p- and PKA-dependent phosphorylation status in intact yeast cells. At the single-cell level, we found that the phosphorylation responses are homogenous for glucose, sucrose, and fructose, but heterogeneous for mannose. Cells that start to grow after a transition to mannose correspond to higher normalized Förster resonance energy transfer (FRET) levels, in line with the involvement of Sch9p and PKA pathways to stimulate growth-related processes. The Sch9p and PKA pathways have a relatively high affinity for glucose (K0.5 of 0.24 mM) under glucose-derepressed conditions. Lastly, steady-state FRET levels of AKAR3-EV seem to be independent of growth rates, suggesting that Sch9p- and PKA-dependent phosphorylation activities are transient responses to nutrient transitions. We believe that the AKAR3-EV sensor is an excellent addition to the biosensor arsenal for illuminating cellular adaptation in single yeast cells.
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Affiliation(s)
- Dennis Botman
- Systems Biology Lab, AIMMS/A-LIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Sineka Kanagasabapathi
- Systems Biology Lab, AIMMS/A-LIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Philipp Savakis
- Systems Biology Lab, AIMMS/A-LIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Bas Teusink
- Systems Biology Lab, AIMMS/A-LIFE, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
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5
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Multi-Omics Analysis of Multiple Glucose-Sensing Receptor Systems in Yeast. Biomolecules 2022; 12:biom12020175. [PMID: 35204676 PMCID: PMC8961648 DOI: 10.3390/biom12020175] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/14/2022] [Accepted: 01/18/2022] [Indexed: 12/13/2022] Open
Abstract
The yeast Saccharomyces cerevisiae has long been used to produce alcohol from glucose and other sugars. While much is known about glucose metabolism, relatively little is known about the receptors and signaling pathways that indicate glucose availability. Here, we compare the two glucose receptor systems in S. cerevisiae. The first is a heterodimer of transporter-like proteins (transceptors), while the second is a seven-transmembrane receptor coupled to a large G protein (Gpa2) that acts in coordination with two small G proteins (Ras1 and Ras2). Through comprehensive measurements of glucose-dependent transcription and metabolism, we demonstrate that the two receptor systems have distinct roles in glucose signaling: the G-protein-coupled receptor directs carbohydrate and energy metabolism, while the transceptors regulate ancillary processes such as ribosome, amino acids, cofactor and vitamin metabolism. The large G-protein transmits the signal from its cognate receptor, while the small G-protein Ras2 (but not Ras1) integrates responses from both receptor pathways. Collectively, our analysis reveals the molecular basis for glucose detection and the earliest events of glucose-dependent signal transduction in yeast.
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6
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Urita A, Ishibashi Y, Kawaguchi R, Yanase Y, Tani M. Crosstalk between protein kinase A and the HOG pathway under impaired biosynthesis of complex sphingolipids in budding yeast. FEBS J 2021; 289:766-786. [PMID: 34492172 DOI: 10.1111/febs.16188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 07/03/2021] [Accepted: 09/06/2021] [Indexed: 11/28/2022]
Abstract
Complex sphingolipids are important components of the lipid bilayer of budding yeast Saccharomyces cerevisiae, and a defect of the biosynthesis causes widespread cellular dysfunction. In this study, we found that mutations causing upregulation of the cAMP/protein kinase A (PKA) pathway cause hypersensitivity to the defect of complex sphingolipid biosynthesis caused by repression of AUR1 encoding inositol phosphorylceramide synthase, whereas loss of PKA confers resistance to the defect. Loss of PDE2 encoding cAMP phosphodiesterase or PKA did not affect the reduction in complex sphingolipid levels and ceramide accumulation caused by AUR1 repression, suggesting that the change in sensitivity to the AUR1 repression due to the mutation of the cAMP/PKA pathway is not caused by exacerbation or suppression of the abnormal metabolism of sphingolipids. We also identified PBS2 encoding MAPKK in the high-osmolarity glycerol (HOG) pathway as a multicopy suppressor gene that rescues the hypersensitivity to AUR1 repression caused by deletion of IRA2, which causes hyperactivation of the cAMP/PKA pathway. Since the HOG pathway has been identified as one of the rescue systems against the growth defect caused by the impaired biosynthesis of complex sphingolipids, it was assumed that PKA affects activation of the HOG pathway under AUR1-repressive conditions. Under AUR1-repressive conditions, hyperactivation of PKA suppressed the phosphorylation of Hog1, MAPK in the HOG pathway, and transcriptional activation downstream of the HOG pathway. These findings suggested that PKA is possibly involved in the avoidance of excessive activation of the HOG pathway under impaired biosynthesis of complex sphingolipids.
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Affiliation(s)
- Atsuya Urita
- Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Yohei Ishibashi
- Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan
| | - Ryotaro Kawaguchi
- Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Yukimi Yanase
- Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Motohiro Tani
- Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, Japan
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7
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Multi-omics analysis of glucose-mediated signaling by a moonlighting Gβ protein Asc1/RACK1. PLoS Genet 2021; 17:e1009640. [PMID: 34214075 PMCID: PMC8282090 DOI: 10.1371/journal.pgen.1009640] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 07/15/2021] [Accepted: 06/02/2021] [Indexed: 12/31/2022] Open
Abstract
Heterotrimeric G proteins were originally discovered through efforts to understand the effects of hormones, such as glucagon and epinephrine, on glucose metabolism. On the other hand, many cellular metabolites, including glucose, serve as ligands for G protein-coupled receptors. Here we investigate the consequences of glucose-mediated receptor signaling, and in particular the role of a Gα subunit Gpa2 and a non-canonical Gβ subunit, known as Asc1 in yeast and RACK1 in animals. Asc1/RACK1 is of particular interest because it has multiple, seemingly unrelated, functions in the cell. The existence of such “moonlighting” operations has complicated the determination of phenotype from genotype. Through a comparative analysis of individual gene deletion mutants, and by integrating transcriptomics and metabolomics measurements, we have determined the relative contributions of the Gα and Gβ protein subunits to glucose-initiated processes in yeast. We determined that Gpa2 is primarily involved in regulating carbohydrate metabolism while Asc1 is primarily involved in amino acid metabolism. Both proteins are involved in regulating purine metabolism. Of the two subunits, Gpa2 regulates a greater number of gene transcripts and was particularly important in determining the amplitude of response to glucose addition. We conclude that the two G protein subunits regulate distinct but complementary processes downstream of the glucose-sensing receptor, as well as processes that lead ultimately to changes in cell growth and metabolism. Despite the societal importance of glucose fermentation in yeast, the mechanisms by which these cells detect and respond to glucose have remained obscure. Glucose detection requires a cell surface receptor coupled to a G protein that is comprised of two subunits, rather than the more typical heterotrimer: an α subunit Gpa2 and the β subunit Asc1 (or RACK1 in humans). Asc1/RACK1 also serves as a subunit of the ribosome, where it regulates the synthesis of proteins involved in glucose fermentation. This manuscript uses global metabolomics and transcriptomics to demonstrate the distinct roles of each G protein subunit in transmitting the glucose signal. Whereas Gpa2 is primarily involved in the metabolism of carbohydrates, Asc1/RACK1 contributes to production of amino acids necessary for protein synthesis and cell division. These findings reveal the initial steps of glucose signaling and several unique and complementary functions of the G protein subunits. More broadly, the integrated approach used here is likely to guide efforts to determine the topology of complex G protein and metabolic signaling networks in humans.
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8
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Botman D, O’Toole TG, Goedhart J, Bruggeman FJ, van Heerden JH, Teusink B. A yeast FRET biosensor enlightens cAMP signaling. Mol Biol Cell 2021; 32:1229-1240. [PMID: 33881352 PMCID: PMC8351543 DOI: 10.1091/mbc.e20-05-0319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 04/08/2021] [Accepted: 04/16/2021] [Indexed: 11/12/2022] Open
Abstract
The cAMP-PKA signaling cascade in budding yeast regulates adaptation to changing environments. We developed yEPAC, a FRET-based biosensor for cAMP measurements in yeast. We used this sensor with flow cytometry for high-throughput single cell-level quantification during dynamic changes in response to sudden nutrient transitions. We found that the characteristic cAMP peak differentiates between different carbon source transitions and is rather homogenous among single cells, especially for transitions to glucose. The peaks are mediated by a combination of extracellular sensing and intracellular metabolism. Moreover, the cAMP peak follows the Weber-Fechner law; its height scales with the relative, and not the absolute, change in glucose. Last, our results suggest that the cAMP peak height conveys information about prospective growth rates. In conclusion, our yEPAC-sensor makes possible new avenues for understanding yeast physiology, signaling, and metabolic adaptation.
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Affiliation(s)
- Dennis Botman
- Systems Biology Lab/AIMMS, Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands
| | - Tom G. O’Toole
- Department of Molecular Cell Biology and Immunology, Vrije University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Joachim Goedhart
- Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Frank J. Bruggeman
- Systems Biology Lab/AIMMS, Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands
| | - Johan H. van Heerden
- Systems Biology Lab/AIMMS, Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands
| | - Bas Teusink
- Systems Biology Lab/AIMMS, Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands
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9
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Jiang L, Chen S, Sun K, Zhou P, Wei X. Intracellular cAMP Measurements in Candida albicans Biofilms. Bio Protoc 2019; 9:e3461. [PMID: 33654947 DOI: 10.21769/bioprotoc.3461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 10/29/2019] [Accepted: 10/12/2019] [Indexed: 11/02/2022] Open
Abstract
Candida albicans is the most common cause of fungal infections worldwide. Infection by C. albicans is closely associated with its ability to form a biofilm, closely packed communities of cells attached to the surfaces of human tissues and implanted devices, in or on the host. When tested for susceptibility to antifungals, such as polyenes, azoles, and allylamines, C. albicans cells in a biofilm are more resistant to antifungal agents than C. albicans cells in the planktonic form. Cyclic Adenosine monophosphate (cAMP) is one of the key elements for triggering hyphal and biofilm formation in C. albicans. It is hard to detect or extract molecular markers (e.g., cAMP) from C. albicans biofilms because the biofilms have a complex three-dimensional architecture with an extracellular matrix surrounding the cell walls of the cells in the biofilm. Here, we present an improved protocol that can effectively measure the level of intracellular cAMP in C. albicans biofilms.
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Affiliation(s)
- Liuliu Jiang
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Shengyan Chen
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Kairui Sun
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Peng Zhou
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Xin Wei
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, China
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10
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Role of Amino Acid Metabolism in the Virulence of Human Pathogenic Fungi. CURRENT CLINICAL MICROBIOLOGY REPORTS 2019. [DOI: 10.1007/s40588-019-00124-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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11
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Chen S, Xia J, Li C, Zuo L, Wei X. The possible molecular mechanisms of farnesol on the antifungal resistance of C. albicans biofilms: the regulation of CYR1 and PDE2. BMC Microbiol 2018; 18:203. [PMID: 30509171 PMCID: PMC6278051 DOI: 10.1186/s12866-018-1344-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 11/16/2018] [Indexed: 12/19/2022] Open
Abstract
Background Farnesol has potential antifungal activity against Candida albicans biofilms, but the molecular mechanism of this activity is still unclear. Farnesol inhibits hyphal growth by regulating the cyclic AMP (cAMP) signalling pathway in C. albicans, and CYR1 and PDE2 regulate a pair of enzymes that are directly responsible for cAMP synthesis and degradation. Here, we hypothesize that farnesol enhances the antifungal susceptibility of C. albicans biofilms by regulating CYR1 and PDE2. Results The resistance of the CYR1- and PDE2-overexpressing strains to caspofungin, itraconazole and terbinafine was increased in planktonic cells, and that to amphotericin B was increased in biofilms. Meanwhile, the biofilms of the CYR1- and PDE2-overexpressing strains were thicker (all p < 0.05) and consisted of more hyphae than that of the wild strain. The intracellular cAMP levels were higher in the biofilms of the CYR1-overexpressing strain than that in the biofilms of the wild strain (all p < 0.01), while no changes were found in the PDE2-overexpressing strain. Exogenous farnesol decreased the resistance of the CYR1- and PDE2-overexpressing strains to these four antifungals, repressed the hyphal and biofilm formation of the strains, and decreased the intracellular cAMP level in the biofilms (all p < 0.05) compared to the untreated controls. In addition, farnesol decreased the expression of the gene CYR1 and the protein CYR1 in biofilms of the CYR1-overexpressing strain (all p < 0.05) but increased the expression of the gene PDE2 and the protein PDE2 in biofilms of the PDE2-overexpressing strain (all p < 0.01). Conclusions The results indicate that CYR1 and PDE2 regulate the resistance of C. albicans biofilms to antifungals. Farnesol suppresses the resistance of C. albicans biofilms to antifungals by regulating the expression of the gene CYR1 and PDE2, while PDE2 regulation was subordinate to CYR1 regulation.
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Affiliation(s)
- Shengyan Chen
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, 210029, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, 210029, China
| | - Jinping Xia
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, 210029, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, 210029, China
| | - Chengxi Li
- Suzhou Hospital Affiliated to Nanjing Medical University, Suzhou Science and Technology Town Hospital, Suzhou, 215153, China
| | - Lulu Zuo
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, 210029, China.,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, 210029, China
| | - Xin Wei
- Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, 210029, China. .,Department of Oral Medicine, Stomatology Hospital Affiliated to Nanjing Medical University, Nanjing, 210029, China.
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12
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Isom DG, Page SC, Collins LB, Kapolka NJ, Taghon GJ, Dohlman HG. Coordinated regulation of intracellular pH by two glucose-sensing pathways in yeast. J Biol Chem 2017; 293:2318-2329. [PMID: 29284676 DOI: 10.1074/jbc.ra117.000422] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 12/22/2017] [Indexed: 12/19/2022] Open
Abstract
The yeast Saccharomyces cerevisiae employs multiple pathways to coordinate sugar availability and metabolism. Glucose and other sugars are detected by a G protein-coupled receptor, Gpr1, as well as a pair of transporter-like proteins, Rgt2 and Snf3. When glucose is limiting, however, an ATP-driven proton pump (Pma1) is inactivated, leading to a marked decrease in cytoplasmic pH. Here we determine the relative contribution of the two sugar-sensing pathways to pH regulation. Whereas cytoplasmic pH is strongly dependent on glucose abundance and is regulated by both glucose-sensing pathways, ATP is largely unaffected and therefore cannot account for the changes in Pma1 activity. These data suggest that the pH is a second messenger of the glucose-sensing pathways. We show further that different sugars differ in their ability to control cellular acidification, in the manner of inverse agonists. We conclude that the sugar-sensing pathways act via Pma1 to invoke coordinated changes in cellular pH and metabolism. More broadly, our findings support the emerging view that cellular systems have evolved the use of pH signals as a means of adapting to environmental stresses such as those caused by hypoxia, ischemia, and diabetes.
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Affiliation(s)
- Daniel G Isom
- From the Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7365, .,the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, and
| | - Stephani C Page
- From the Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7365
| | - Leonard B Collins
- the Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina 27599-7432
| | - Nicholas J Kapolka
- the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, and
| | - Geoffrey J Taghon
- the Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136, and
| | - Henrik G Dohlman
- From the Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7365,
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13
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Abstract
To respond to the changing environment, cells must be able to sense external conditions. This is important for many processes including growth, mating, the expression of virulence factors, and several other regulatory effects. Nutrient sensing at the plasma membrane is mediated by different classes of membrane proteins that activate downstream signaling pathways: nontransporting receptors, transceptors, classical and nonclassical G-protein-coupled receptors, and the newly defined extracellular mucin receptors. Nontransporting receptors have the same structure as transport proteins, but have lost the capacity to transport while gaining a receptor function. Transceptors are transporters that also function as a receptor, because they can rapidly activate downstream signaling pathways. In this review, we focus on these four types of fungal membrane proteins. We mainly discuss the sensing mechanisms relating to sugars, ammonium, and amino acids. Mechanisms for other nutrients, such as phosphate and sulfate, are discussed briefly. Because the model yeast Saccharomyces cerevisiae has been the most studied, especially regarding these nutrient-sensing systems, each subsection will commence with what is known in this species.
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14
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Characterization of gprK Encoding a Putative Hybrid G-Protein-Coupled Receptor in Aspergillus fumigatus. PLoS One 2016; 11:e0161312. [PMID: 27584150 PMCID: PMC5008803 DOI: 10.1371/journal.pone.0161312] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 08/03/2016] [Indexed: 11/19/2022] Open
Abstract
The G-protein-coupled receptor (GPCR) family represents the largest and most varied collection of membrane embedded proteins that are sensitized by ligand binding and interact with heterotrimeric G proteins. Despite their presumed critical roles in fungal biology, the functions of the GPCR family members in the opportunistic human pathogen Aspergillus fumigatus are largely unknown, as only two (GprC and GprD) of the 15 predicted GPCRs have been studied. Here, we characterize the gprK gene, which is predicted to encode a hybrid GPCR with both 7-transmembrane and regulator of G-protein signaling (RGS) domains. The deletion of gprK causes severely impaired asexual development coupled with reduced expression of key developmental activators. Moreover, ΔgprK results in hyper-activation of germination even in the absence of carbon source, and elevated expression and activity of the protein kinase A PkaC1. Furthermore, proliferation of the ΔgprK mutant is restricted on the medium when pentose is the sole carbon source, suggesting that GprK may function in external carbon source sensing. Notably, the absence of gprK results in reduced tolerance to oxidative stress and significantly lowered mRNA levels of the stress-response associated genes sakA and atfA. Activities of catalases and SODs are severely decreased in the ΔgprK mutant, indicating that GprK may function in proper activation of general stress response. The ΔgprK mutant is also defective in gliotoxin (GT) production and slightly less virulent toward the greater wax moth, Galleria mellonella. Transcriptomic studies reveal that a majority of transporters are down-regulated by ΔgprK. In summary, GprK is necessary for proper development, GT production, and oxidative stress response, and functions in down-regulating the PKA-germination pathway.
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15
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Brown NA, Dos Reis TF, Ries LNA, Caldana C, Mah JH, Yu JH, Macdonald JM, Goldman GH. G-protein coupled receptor-mediated nutrient sensing and developmental control in Aspergillus nidulans. Mol Microbiol 2015; 98:420-39. [PMID: 26179439 DOI: 10.1111/mmi.13135] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/14/2015] [Indexed: 12/31/2022]
Abstract
Nutrient sensing and utilisation are fundamental for all life forms. As heterotrophs, fungi have evolved a diverse range of mechanisms for sensing and taking up various nutrients. Despite its importance, only a limited number of nutrient receptors and their corresponding ligands have been identified in fungi. G-protein coupled receptors (GPCRs) are the largest family of transmembrane receptors. The Aspergillus nidulans genome encodes 16 putative GPCRs, but only a few have been functionally characterised. Our previous study showed the increased expression of an uncharacterised putative GPCR, gprH, during carbon starvation. GprH appears conserved throughout numerous filamentous fungi. Here, we reveal that GprH is a putative receptor involved in glucose and tryptophan sensing. The absence of GprH results in a reduction in cAMP levels and PKA activity upon adding glucose or tryptophan to starved cells. GprH is pre-formed in conidia and is increasingly active during carbon starvation, where it plays a role in glucose uptake and the recovery of hyphal growth. GprH also represses sexual development under conditions favouring sexual fruiting and during carbon starvation in submerged cultures. In summary, the GprH nutrient-sensing system functions upstream of the cAMP-PKA pathway, influences primary metabolism and hyphal growth, while represses sexual development in A. nidulans.
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Affiliation(s)
- Neil Andrew Brown
- Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK
| | - Thaila Fernanda Dos Reis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | | | - Camila Caldana
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol - CTBE, Campinas, São Paulo, Brazil.,Max Planck Partnergroup at CTBE/CNPEM, Campinas, São Paulo, Brazil
| | - Jae-Hyung Mah
- Department of Food and Biotechnology, Korea University, Sejong, South Korea
| | - Jae-Hyuk Yu
- Department of Bacteriology, University of Wisconsin, Madison, WI, USA
| | - Jeffrey M Macdonald
- UNC Metabolomic Facility, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Gustavo Henrique Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil.,Laboratório Nacional de Ciência e Tecnologia do Bioetanol - CTBE, Campinas, São Paulo, Brazil
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16
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Rødkaer SV, Faergeman NJ. Glucose- and nitrogen sensing and regulatory mechanisms inSaccharomyces cerevisiae. FEMS Yeast Res 2014; 14:683-96. [DOI: 10.1111/1567-1364.12157] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 04/11/2014] [Accepted: 04/13/2014] [Indexed: 11/29/2022] Open
Affiliation(s)
- Steven V. Rødkaer
- Villum Center for Bioanalytical Sciences; Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense M Denmark
| | - Nils J. Faergeman
- Villum Center for Bioanalytical Sciences; Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense M Denmark
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17
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Grice CM, Bertuzzi M, Bignell EM. Receptor-mediated signaling in Aspergillus fumigatus. Front Microbiol 2013; 4:26. [PMID: 23430083 PMCID: PMC3576715 DOI: 10.3389/fmicb.2013.00026] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Accepted: 02/01/2013] [Indexed: 11/15/2022] Open
Abstract
Aspergillus fumigatus is the most pathogenic species among the Aspergilli, and the major fungal agent of human pulmonary infection. To prosper in diverse ecological niches, Aspergilli have evolved numerous mechanisms for adaptive gene regulation, some of which are also crucial for mammalian infection. Among the molecules which govern such responses, integral membrane receptors are thought to be the most amenable to therapeutic modulation. This is due to the localization of these molecular sensors at the periphery of the fungal cell, and to the prevalence of small molecules and licensed drugs which target receptor-mediated signaling in higher eukaryotic cells. In this review we highlight the progress made in characterizing receptor-mediated environmental adaptation in A. fumigatus and its relevance for pathogenicity in mammals. By presenting a first genomic survey of integral membrane proteins in this organism, we highlight an abundance of putative seven transmembrane domain (7TMD) receptors, the majority of which remain uncharacterized. Given the dependency of A. fumigatus upon stress adaptation for colonization and infection of mammalian hosts, and the merits of targeting receptor-mediated signaling as an antifungal strategy, a closer scrutiny of sensory perception and signal transduction in this organism is warranted.
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Affiliation(s)
- C M Grice
- South Kensington Campus, Imperial College London London, UK
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18
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Apweiler E, Sameith K, Margaritis T, Brabers N, van de Pasch L, Bakker LV, van Leenen D, Holstege FC, Kemmeren P. Yeast glucose pathways converge on the transcriptional regulation of trehalose biosynthesis. BMC Genomics 2012; 13:239. [PMID: 22697265 PMCID: PMC3472246 DOI: 10.1186/1471-2164-13-239] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 06/14/2012] [Indexed: 01/12/2023] Open
Abstract
Background Cellular glucose availability is crucial for the functioning of most biological processes. Our understanding of the glucose regulatory system has been greatly advanced by studying the model organism Saccharomyces cerevisiae, but many aspects of this system remain elusive. To understand the organisation of the glucose regulatory system, we analysed 91 deletion mutants of the different glucose signalling and metabolic pathways in Saccharomyces cerevisiae using DNA microarrays. Results In general, the mutations do not induce pathway-specific transcriptional responses. Instead, one main transcriptional response is discerned, which varies in direction to mimic either a high or a low glucose response. Detailed analysis uncovers established and new relationships within and between individual pathways and their members. In contrast to signalling components, metabolic components of the glucose regulatory system are transcriptionally more frequently affected. A new network approach is applied that exposes the hierarchical organisation of the glucose regulatory system. Conclusions The tight interconnection between the different pathways of the glucose regulatory system is reflected by the main transcriptional response observed. Tps2 and Tsl1, two enzymes involved in the biosynthesis of the storage carbohydrate trehalose, are predicted to be the most downstream transcriptional components. Epistasis analysis of tps2Δ double mutants supports this prediction. Although based on transcriptional changes only, these results suggest that all changes in perceived glucose levels ultimately lead to a shift in trehalose biosynthesis.
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Affiliation(s)
- Eva Apweiler
- Molecular Cancer Research, University Medical Centre Utrecht, Utrecht, the Netherlands
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19
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Brückner S, Mösch HU. Choosing the right lifestyle: adhesion and development in Saccharomyces cerevisiae. FEMS Microbiol Rev 2011; 36:25-58. [PMID: 21521246 DOI: 10.1111/j.1574-6976.2011.00275.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The budding yeast Saccharomyces cerevisiae is a eukaryotic microorganism that is able to choose between different unicellular and multicellular lifestyles. The potential of individual yeast cells to switch between different growth modes is advantageous for optimal dissemination, protection and substrate colonization at the population level. A crucial step in lifestyle adaptation is the control of self- and foreign adhesion. For this purpose, S. cerevisiae contains a set of cell wall-associated proteins, which confer adhesion to diverse biotic and abiotic surfaces. Here, we provide an overview of different aspects of S. cerevisiae adhesion, including a detailed description of known lifestyles, recent insights into adhesin structure and function and an outline of the complex regulatory network for adhesin gene regulation. Our review shows that S. cerevisiae is a model system suitable for studying not only the mechanisms and regulation of cell adhesion, but also the role of this process in microbial development, ecology and evolution.
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Affiliation(s)
- Stefan Brückner
- Department of Genetics, Philipps-Universität Marburg, Marburg, Germany
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20
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Dechant R, Binda M, Lee SS, Pelet S, Winderickx J, Peter M. Cytosolic pH is a second messenger for glucose and regulates the PKA pathway through V-ATPase. EMBO J 2010; 29:2515-26. [PMID: 20581803 DOI: 10.1038/emboj.2010.138] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Accepted: 05/28/2010] [Indexed: 01/04/2023] Open
Abstract
Glucose is the preferred carbon source for most cell types and a major determinant of cell growth. In yeast and certain mammalian cells, glucose activates the cAMP-dependent protein kinase A (PKA), but the mechanisms of PKA activation remain unknown. Here, we identify cytosolic pH as a second messenger for glucose that mediates activation of the PKA pathway in yeast. We find that cytosolic pH is rapidly and reversibly regulated by glucose metabolism and identify the vacuolar ATPase (V-ATPase), a proton pump required for the acidification of vacuoles, as a sensor of cytosolic pH. V-ATPase assembly is regulated by cytosolic pH and is required for full activation of the PKA pathway in response to glucose, suggesting that it mediates, at least in part, the pH signal to PKA. Finally, V-ATPase is also regulated by glucose in the Min6 beta-cell line and contributes to PKA activation and insulin secretion. Thus, these data suggest a novel and potentially conserved glucose-sensing pathway and identify a mechanism how cytosolic pH can act as a signal to promote cell growth.
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21
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Shemarova IV. cAMP-dependent signal pathways in unicellular eukaryotes. Crit Rev Microbiol 2009; 35:23-42. [PMID: 19514907 DOI: 10.1080/10408410802645646] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The review summarizes current data about mechanisms of signal transduction with participation of cAMP (cyclic adenosine monophosphate) and elements of the complex cAMP-protein kinase A (PKA) signal pathway in unicellular eukaryotes. Conceptions of evolutionary origin of eukaryotic signal transduction systems are developed.
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Affiliation(s)
- Irina V Shemarova
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
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22
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Abstract
In the presence of glucose, yeast undergoes an important remodelling of its metabolism. There are changes in the concentration of intracellular metabolites and in the stability of proteins and mRNAs; modifications occur in the activity of enzymes as well as in the rate of transcription of a large number of genes, some of the genes being induced while others are repressed. Diverse combinations of input signals are required for glucose regulation of gene expression and of other cellular processes. This review focuses on the early elements in glucose signalling and discusses their relevance for the regulation of specific processes. Glucose sensing involves the plasma membrane proteins Snf3, Rgt2 and Gpr1 and the glucose-phosphorylating enzyme Hxk2, as well as other regulatory elements whose functions are still incompletely understood. The similarities and differences in the way in which yeasts and mammalian cells respond to glucose are also examined. It is shown that in Saccharomyces cerevisiae, sensing systems for other nutrients share some of the characteristics of the glucose-sensing pathways.
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Affiliation(s)
- Juana M Gancedo
- Department of Metabolism and Cell Signalling, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain.
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23
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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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24
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Tamaki H. Glucose-stimulated cAMP-protein kinase A pathway in yeast Saccharomyces cerevisiae. J Biosci Bioeng 2007; 104:245-50. [PMID: 18023794 DOI: 10.1263/jbb.104.245] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 07/09/2007] [Indexed: 11/17/2022]
Abstract
In the yeast Saccharomyces cerevisiae, glucose signals activate the production of cellular cAMP. This signaling pathway is called the cAMP-protein kinase A (PKA) pathway, which plays a major role in the regulation of cell growth, metabolism, and stress resistance. Extensive studies have been carried out to clarify the mechanism of this pathway, and many factors involved in the pathway have been identified such as small G proteins, the GDP-GTP exchange factor, adenylate cyclase, and PKA. Also, additional elements involved in this pathway have been evaluated in the last decade. A heterotrimeric G protein alpha subunit was identified as a mammalian Galpha homologue, and a G-protein-coupled receptor (GPCR), which initiates the signaling pathway in response to glucose addition, was identified. GPCR-Galpha was shown to function in a signaling pathway that acts parallel to small G proteins. These signaling pathways regulate cell growth and differentiation in response to nutrients.
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Affiliation(s)
- Hisanori Tamaki
- Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
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25
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Zeller CE, Parnell SC, Dohlman HG. The RACK1 ortholog Asc1 functions as a G-protein beta subunit coupled to glucose responsiveness in yeast. J Biol Chem 2007; 282:25168-76. [PMID: 17591772 DOI: 10.1074/jbc.m702569200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
According to the prevailing paradigm, G-proteins are composed of three subunits, an alpha subunit with GTPase activity and a tightly associated betagamma subunit complex. In the yeast Saccharomyces cerevisiae there are two known Galpha proteins (Gpa1 and Gpa2) but only one Gbetagamma, which binds only to Gpa1. Here we show that the yeast ortholog of RACK1 (receptor for activated protein kinase C1) Asc1 functions as the Gbeta for Gpa2. As with other known Gbeta proteins, Asc1 has a 7-WD domain structure, interacts directly with the Galpha in a guanine nucleotide-dependent manner, and inhibits Galpha guanine nucleotide exchange activity. In addition, Asc1 binds to the effector enzyme adenylyl cyclase (Cyr1), and diminishes the production of cAMP in response to glucose stimulation. Thus, whereas Gpa2 promotes glucose signaling through elevated production of cAMP, Asc1 has opposing effects on these same processes. Our findings reveal the existence of an unusual Gbeta subunit, one having multiple functions within the cell in addition to serving as a signal transducer for cell surface receptors and intracellular effectors.
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Affiliation(s)
- Corinne E Zeller
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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26
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Belinchón MM, Gancedo JM. Different signalling pathways mediate glucose induction of SUC2, HXT1 and pyruvate decarboxylase in yeast. FEMS Yeast Res 2007; 7:40-7. [PMID: 17311583 DOI: 10.1111/j.1567-1364.2006.00136.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The glucose sensors Gpr1, Snf3 and Rgt2 generate the earliest signals produced by glucose in yeast. We showed that a lack of Gpr1 or Snf3/Rgt2 decreased by twofold the glucose induction of SUC2, but had no effect on the induction of pyruvate decarboxylase (Pdc). The induction of HXT1 was not affected by the absence of Gpr1. In an hxk1 hxk2 glk1 strain, high glucose fully induced SUC2, caused partial induction of HXT1 and had no effect on Pdc. In this strain, SUC2 induction was dependent on Gpr1, but HXT1 induction was not. Hxk2, required for the high expression of HXT1, was dispensable for the full induction of SUC2 or Pdc. These results indicate that glucose does not induce transcription through a single signalling pathway, but that several pathways may, in different combinations, regulate the transcription of different genes.
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Affiliation(s)
- Mónica M Belinchón
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid, Spain
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27
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Li L, Borkovich KA. GPR-4 is a predicted G-protein-coupled receptor required for carbon source-dependent asexual growth and development in Neurospora crassa. EUKARYOTIC CELL 2007; 5:1287-300. [PMID: 16896213 PMCID: PMC1539153 DOI: 10.1128/ec.00109-06] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The filamentous fungus Neurospora crassa is able to utilize a wide variety of carbon sources. Here, we examine the involvement of a predicted G-protein-coupled receptor (GPCR), GPR-4, during growth and development in the presence of different carbon sources in N. crassa. Deltagpr-4 mutants have reduced mass accumulation compared to the wild type when cultured on high levels of glycerol, mannitol, or arabinose. The defect is most severe on glycerol and is cell density dependent. The genetic and physical relationship between GPR-4 and the three N. crassa Galpha subunits (GNA-1, GNA-2, and GNA-3) was explored. All three Galpha mutants are defective in mass accumulation when cultured on glycerol. However, the phenotypes of Deltagna-1 and Deltagpr-4 Deltagna-1 mutants are identical, introduction of a constitutively activated gna-1 allele suppresses the defects of the Deltagpr-4 mutation, and the carboxy terminus of GPR-4 interacts most strongly with GNA-1 in the yeast two-hybrid assay. Although steady-state cyclic AMP (cAMP) levels are normal in Deltagpr-4 strains, exogenous cAMP partially remediates the dry mass defects of Deltagpr-4 mutants on glycerol medium and Deltagpr-4 strains lack the transient increase in cAMP levels observed in the wild type after addition of glucose to glycerol-grown liquid cultures. Our results support the hypothesis that GPR-4 is coupled to GNA-1 in a cAMP signaling pathway that regulates the response to carbon source in N. crassa. GPR-4-related GPCRs are present in the genomes of several filamentous ascomycete fungal pathogens, raising the possibility that a similar pathway regulates carbon sensing in these organisms.
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Affiliation(s)
- Liande Li
- Department of Plant Pathology, 1415 Boyce Hall, 900 University Avenue, University of California, Riverside, Riverside, CA 92521, USA.
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28
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Shpakov AO. Serpentine type receptors and heterotrimeric G-proteins in yeasts: Structural-functional organization and molecular mechanisms of action. J EVOL BIOCHEM PHYS+ 2007. [DOI: 10.1134/s0022093007010012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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29
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Krystofova S, Borkovich KA. The predicted G-protein-coupled receptor GPR-1 is required for female sexual development in the multicellular fungus Neurospora crassa. EUKARYOTIC CELL 2006; 5:1503-16. [PMID: 16963633 PMCID: PMC1563582 DOI: 10.1128/ec.00124-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
G-protein-coupled receptors (GPCRs) control important aspects of asexual and sexual development in eukaryotic organisms. We have identified a predicted GPCR in the filamentous fungus Neurospora crassa with similarity to cyclic AMP-receptor like GPCRs from Dictyostelium discoideum and GCR1 from Arabidopsis thaliana. Expression of gpr-1 is highest in female reproductive structures, and deletion of gpr-1 leads to defects during sexual development. Unfertilized female structures (protoperithecia) from Deltagpr-1 strains are weakly pigmented, small, and submerged in the agar. The perithecia produced after fertilization have deformed beaks that lack ostioles, the openings through which ascospores are discharged. Localization studies using a GPR-1-green fluorescent protein fusion protein showed that GPR-1 is targeted to female reproductive structures. Genetic epistasis experiments with the three Galpha genes were inconclusive due to the early block in mating exhibited by Deltagna-1 strains. Phenotypic analysis of mutants from a high-throughput N. crassa knockout project allowed identification of BEK-1, a homeodomain transcription factor that is a potential target of GPR-1. The perithecial defects of Deltabek-1 strains are similar to those of the Deltagpr-1 strain, and epistasis analysis indicates that bek-1 could function downstream of gpr-1 during postfertilization events. The effect must be posttranscriptional, as bek-1 transcript levels are not affected in Deltagpr-1 strains. The lack of ostioles in Deltagpr-1 and Deltabek-1 mutants has an undesirable effect on the ability to spread progeny (ascospores) by the normal ejection mechanism and would severely compromise the fitness of these strains in nature.
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Affiliation(s)
- Svetlana Krystofova
- Department of Plant Pathology, University of California, 1415 Boyce Hall, 900 University Ave., Riverside, 92521, USA
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30
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Harashima T, Anderson S, Yates JR, Heitman J. The kelch proteins Gpb1 and Gpb2 inhibit Ras activity via association with the yeast RasGAP neurofibromin homologs Ira1 and Ira2. Mol Cell 2006; 22:819-830. [PMID: 16793550 DOI: 10.1016/j.molcel.2006.05.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2005] [Revised: 03/14/2006] [Accepted: 05/08/2006] [Indexed: 11/26/2022]
Abstract
The G protein-coupled receptor Gpr1 and associated Galpha subunit Gpa2 govern dimorphic transitions in response to extracellular nutrients by signaling coordinately with Ras to activate adenylyl cyclase in the yeast Saccharomyces cerevisiae. Gpa2 forms a protein complex with the kelch Gbeta mimic subunits Gpb1/2, and previous studies demonstrate that Gpb1/2 negatively control cAMP-PKA signaling via Gpa2 and an unknown second target. Here, we define these targets of Gpb1/2 as the yeast neurofibromin homologs Ira1 and Ira2, which function as GTPase activating proteins of Ras. Gpb1/2 bind to a conserved C-terminal domain of Ira1/2, and loss of Gpb1/2 results in a destabilization of Ira1 and Ira2, leading to elevated levels of Ras2-GTP and unbridled cAMP-PKA signaling. Because the Gpb1/2 binding domain on Ira1/2 is conserved in the human neurofibromin protein, an analogous signaling network may contribute to the neoplastic development of neurofibromatosis type 1.
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Affiliation(s)
- Toshiaki Harashima
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710
| | - Scott Anderson
- The Scripps Research Institute, La Jolla, California 92037
| | - John R Yates
- The Scripps Research Institute, La Jolla, California 92037
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710.
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31
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Kao RS, Morreale E, Wang L, Ivey FD, Hoffman CS. Schizosaccharomyces pombe Git1 is a C2-domain protein required for glucose activation of adenylate cyclase. Genetics 2006; 173:49-61. [PMID: 16489217 PMCID: PMC1461440 DOI: 10.1534/genetics.106.055699] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Schizosaccharomyces pombe senses environmental glucose through a cAMP-signaling pathway, activating cAMP-dependent protein kinase A (PKA). This requires nine git (glucose insensitive transcription) genes that encode adenylate cyclase, the PKA catalytic subunit, and seven "upstream" proteins required for glucose-triggered adenylate cyclase activation, including three heterotrimeric G-protein subunits and its associated receptor. We describe here the cloning and characterization of the git1+ gene. Git1 is distantly related to a small group of uncharacterized fungal proteins, including a second S. pombe protein that is not functionally redundant with Git1, as well as to members of the UNC-13/Munc13 protein family. Mutations in git1+ demonstrate functional roles for the two most highly conserved regions of the protein, the C2 domain and the MHD2 Munc homology domain. Cells lacking Git1 are viable, but display phenotypes associated with cAMP-signaling defects, even in strains expressing a mutationally activated G alpha-subunit, which activates adenylate cyclase. These cells possess reduced basal cAMP levels and fail to mount a cAMP response to glucose. In addition, Git1 and adenylate cyclase physically interact and partially colocalize in the cell. Thus, Git1 is a critical component of the S. pombe glucose/cAMP pathway.
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Affiliation(s)
- Richard S Kao
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA
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32
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Hoffman CS. Except in every detail: comparing and contrasting G-protein signaling in Saccharomyces cerevisiae and Schizosaccharomyces pombe. EUKARYOTIC CELL 2005; 4:495-503. [PMID: 15755912 PMCID: PMC1087802 DOI: 10.1128/ec.4.3.495-503.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Charles S Hoffman
- Biology Department, Boston College, 140 Commonwealth Ave., Higgins Hall 401B, Chestnut Hill, MA 02467, USA.
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Xue C, Bahn YS, Cox GM, Heitman J. G protein-coupled receptor Gpr4 senses amino acids and activates the cAMP-PKA pathway in Cryptococcus neoformans. Mol Biol Cell 2005; 17:667-79. [PMID: 16291861 PMCID: PMC1356578 DOI: 10.1091/mbc.e05-07-0699] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Galpha protein Gpa1 governs the cAMP-PKA signaling pathway and plays a central role in virulence and differentiation in the human fungal pathogen Cryptococcus neoformans, but the signals and receptors that trigger this pathway were unknown. We identified seven putative proteins that share identity with known G protein-coupled receptors (GPCRs). One protein, Gpr4, shares limited sequence identity with the Dictyostelium discoideum cAMP receptor cAR1 and the Aspergillus nidulans GPCR protein GprH and also shares structural similarity with the Saccharomyces cerevisiae receptor Gpr1. gpr4 mutants exhibited reduced capsule production and mating defects, similar to gpa1 mutants, and exogenous cAMP suppressed both gpr4 mutant phenotypes. Epistasis analysis provides further evidence that Gpr4 functions upstream of the Galpha subunit Gpa1. Gpr4-Gpr4 homomeric interactions were observed in the yeast two-hybrid assay, and Gpr4 was shown to physically interact with Gpa1 in the split-ubiquitin system. A Gpr4::DsRED fusion protein was localized to the plasma membrane and methionine was found to trigger receptor internalization. The analysis of intracellular cAMP levels showed that gpr4 mutants still respond to glucose but not to certain amino acids, such as methionine. Amino acids might serve as ligands for Gpr4 and could contribute to engage the cAMP-PKA pathway. Activation of the cAMP-PKA pathway by glucose and amino acids represents a nutrient coincidence detection system shared in other pathogenic fungi.
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Affiliation(s)
- Chaoyang Xue
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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Harashima T, Heitman J. Galpha subunit Gpa2 recruits kelch repeat subunits that inhibit receptor-G protein coupling during cAMP-induced dimorphic transitions in Saccharomyces cerevisiae. Mol Biol Cell 2005; 16:4557-71. [PMID: 16030250 PMCID: PMC1237064 DOI: 10.1091/mbc.e05-05-0403] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 06/23/2005] [Accepted: 07/12/2005] [Indexed: 11/11/2022] Open
Abstract
All eukaryotic cells sense extracellular stimuli and activate intracellular signaling cascades via G protein-coupled receptors (GPCR) and associated heterotrimeric G proteins. The Saccharomyces cerevisiae GPCR Gpr1 and associated Galpha subunit Gpa2 sense extracellular carbon sources (including glucose) to govern filamentous growth. In contrast to conventional Galpha subunits, Gpa2 forms an atypical G protein complex with the kelch repeat Gbeta mimic proteins Gpb1 and Gpb2. Gpb1/2 negatively regulate cAMP signaling by inhibiting Gpa2 and an as yet unidentified target. Here we show that Gpa2 requires lipid modifications of its N-terminus for membrane localization but association with the Gpr1 receptor or Gpb1/2 subunits is dispensable for membrane targeting. Instead, Gpa2 promotes membrane localization of its associated Gbeta mimic subunit Gpb2. We also show that the Gpa2 N-terminus binds both to Gpb2 and to the C-terminal tail of the Gpr1 receptor and that Gpb1/2 binding interferes with Gpr1 receptor coupling to Gpa2. Our studies invoke novel mechanisms involving GPCR-G protein modules that may be conserved in multicellular eukaryotes.
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Affiliation(s)
- Toshiaki Harashima
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
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Chikamori M, Fukushima K. A new hexose transporter from Cryptococcus neoformans: molecular cloning and structural and functional characterization. Fungal Genet Biol 2005; 42:646-55. [PMID: 15907385 DOI: 10.1016/j.fgb.2005.04.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 03/28/2005] [Accepted: 04/03/2005] [Indexed: 11/22/2022]
Abstract
We carried out a screen for Cryptococcus neoformans genes involved in resistance to copper ion toxicity and identified a new hexose transporter (Hxt) gene, HXT1. Hxt1 consists of 520 amino acids and functions to transport hexoses such as glucose. Although Hxt1 conferred copper resistance to Saccharomyces cerevisiae, disruption of the HXT1 gene showed that Hxt1 is not necessary for copper resistance. In virulence tests, an hxt1 mutant strain showed 12% less phenoloxidase activity than the wild-type strain, and no difference in the ability to form melanin was identified. In addition, the hxt1 mutant strain showed virulence similar to that of the wild-type strain in experiments with Caenorhabditis elegans. However, the hxt1 mutant strain generated larger capsules than were generated by the wild-type strain. Thus, Hxt1 appears to be involved in capsule formation.
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Affiliation(s)
- Minoru Chikamori
- Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chuo-ku, Chiba 260-8673, Japan
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Wang L, Griffiths K, Zhang YH, Ivey FD, Hoffman CS. Schizosaccharomyces pombe adenylate cyclase suppressor mutations suggest a role for cAMP phosphodiesterase regulation in feedback control of glucose/cAMP signaling. Genetics 2005; 171:1523-33. [PMID: 16143612 PMCID: PMC1456081 DOI: 10.1534/genetics.105.047233] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations affecting the Schizosaccharomyces pombe cAMP phosphodiesterase (PDE) gene cgs2+ were identified in a screen for suppressors of mutant alleles of the adenylate cyclase gene (git2+/cyr1+), which encode catalytically active forms of the enzyme that cannot be stimulated by extracellular glucose signaling. These mutations suppress both the git2(-) mutant alleles used in the suppressor selection and mutations in git1+, git3+, git5+, git7+, git10+, and git11+, which are all required for adenylate cyclase activation. Notably, these cgs2 mutant alleles fail to suppress mutations in gpa2+, which encodes the Galpha subunit of a heterotrimeric G protein required for adenylate cyclase activation, although the previously identified cgs2-2 allele does suppress loss of gpa2+. Further analysis of the cgs2-s1 allele reveals a synthetic interaction with the gpa2(R176H)-activated allele, with respect to derepression of fbp1-lacZ transcription in glucose-starved cells. In addition, direct measurements of cAMP levels show that cgs2-s1 cells maintain normal basal cAMP levels, but are severely defective in feedback regulation upon glucose detection. These results suggest that PDE activity in S. pombe may be coordinately regulated with adenylate cyclase activity as part of the feedback regulation mechanism to limit the cAMP response to glucose detection.
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Affiliation(s)
- Lili Wang
- Biology Department, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA
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37
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Miwa T, Takagi Y, Shinozaki M, Yun CW, Schell WA, Perfect JR, Kumagai H, Tamaki H. Gpr1, a putative G-protein-coupled receptor, regulates morphogenesis and hypha formation in the pathogenic fungus Candida albicans. EUKARYOTIC CELL 2005; 3:919-31. [PMID: 15302825 PMCID: PMC500877 DOI: 10.1128/ec.3.4.919-931.2004] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In response to various extracellular signals, the morphology of the human fungal pathogen Candida albicans switches from yeast to hypha form. Here, we report that GPR1 encoding a putative G-protein-coupled receptor and GPA2 encoding a Galpha subunit are required for hypha formation and morphogenesis in C. albicans. Mutants lacking Gpr1 (gpr1/gpr1) or Gpa2 (gpa2/gpa2) are defective in hypha formation and morphogenesis on solid hypha-inducing media. These phenotypic defects in solid cultures are suppressed by exogenously added dibutyryl-cyclic AMP (dibutyryl-cAMP). Biochemical studies also reveal that GPR1 and GPA2 are required for a glucose-dependent increase in cellular cAMP. An epistasis analysis indicates that Gpr1 functions upstream of Gpa2 in the same signaling pathway, and a two-hybrid assay reveals that the carboxyl-terminal tail of Gpr1 interacts with Gpa2. Moreover, expression levels of HWP1 and ECE1, which are cAMP-dependent hypha-specific genes, are reduced in both mutant strains. These findings support a model that Gpr1, as well as Gpa2, regulates hypha formation and morphogenesis in a cAMP-dependent manner. In contrast, GPR1 and GPA2 are not required for hypha formation in liquid fetal bovine serum (FBS) medium. Furthermore, the gpr1 and the gpa2 mutant strains are fully virulent in a mouse infection. These findings suggest that Gpr1 and Gpa2 are involved in the glucose-sensing machinery that regulates morphogenesis and hypha formation in solid media via a cAMP-dependent mechanism, but they are not required for hypha formation in liquid medium or during invasive candidiasis.
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Affiliation(s)
- Takuya Miwa
- Division of Integrated Life Sciences, Graduate School of Biostudies, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
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38
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Abstract
Sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) are endogenous bioactive lipids that participate in the regulation of mammalian cell proliferation, apoptosis, migration, and angiogenesis. These processes are each critical for successful embryogenesis, raising the possibility that lysophospholipid signaling may contribute to normal animal development. In fact, recent studies in developmental model systems have established that S1P and LPA are necessary for diverse developmental programs including those required for morphogenesis of vertebrate reproductive, cardiovascular and central and peripheral nervous systems (PNS), as well as the establishment of maternal-fetal circulation and the immune system. Genetic, morphological, and biochemical characterization of developmental model systems offer powerful approaches to elucidating the molecular mechanisms of lysophospholipid signaling and its contributions to animal development and postnatal physiology. In this review, the routes of S1P and LPA metabolism and our current understanding of lysophospholipid-mediated signal transduction in mammalian cells will be summarized. The evidence implicating lysophospholipid signaling in the development of specific vertebrate systems will then be reviewed, with an emphasis on signals mediated through G protein-coupled receptors of the Edg family. Lastly, recent insights derived from the study of simple metazoan models and implications regarding lysophospholipid signaling in organisms in which Edg receptors are not conserved will be explored.
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Affiliation(s)
- Julie D Saba
- Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, California 94609-1673, USA.
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Tamaki H, Yun CW, Mizutani T, Tsuzuki T, Takagi Y, Shinozaki M, Kodama Y, Shirahige K, Kumagai H. Glucose-dependent cell size is regulated by a G protein-coupled receptor system in yeastSaccharomyces cerevisiae. Genes Cells 2005; 10:193-206. [PMID: 15743410 DOI: 10.1111/j.1365-2443.2005.00828.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In the yeast, Saccharomyces cerevisiae, cell size is affected by the kind of carbon source in the medium. Here, we present evidence that the Gpr1 receptor and Gpa2 Galpha subunit are required for both maintenance and modulation of cell size in response to glucose. In the presence of glucose, mutants lacking GPR1 or GPA2 gene showed smaller cells than the wild-type strain. Physiological studies revealed that protein synthesis rate was reduced in the mutant strains indicating that reduced growth rate, while the level of mRNAs for CLN1, 2 and 3 was not affected in all strains. Gene chip analysis also revealed a down-regulation in the expression of genes related to biosynthesis of not only protein but also other cellular component in the mutant strains. We also show that GPR1 and GPA2 are required for a rapid increase in cell size in response to glucose. Wild-type cells grown in ethanol quickly increased in size by addition of glucose, while little change was observed in the mutant strains, in which glucose-dependent cell cycle arrest caused by CLN1 repression was somewhat alleviated. Our study indicates that the yeast G-protein coupled receptor system consisting of Gpr1 and Gpa2 regulates cell size by affecting both growth rate and cell division.
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Affiliation(s)
- Hisanori Tamaki
- Division of Integrated Life Sciences, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
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40
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Maidan MM, De Rop L, Serneels J, Exler S, Rupp S, Tournu H, Thevelein JM, Van Dijck P. The G protein-coupled receptor Gpr1 and the Galpha protein Gpa2 act through the cAMP-protein kinase A pathway to induce morphogenesis in Candida albicans. Mol Biol Cell 2005; 16:1971-86. [PMID: 15673611 PMCID: PMC1073676 DOI: 10.1091/mbc.e04-09-0780] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We investigated the role in cell morphogenesis and pathogenicity of the Candida albicans GPR1 gene, encoding the G protein-coupled receptor Gpr1. Deletion of C. albicans GPR1 has only minor effects in liquid hypha-inducing media but results in strong defects in the yeast-to-hypha transition on solid hypha-inducing media. Addition of cAMP, expression of a constitutively active allele of the Galpha protein Gpa2 or of the catalytic protein kinase A subunit TPK1 restores the wild-type phenotype of the CaGPR1-deleted strain. Overexpression of HST7, encoding a component of the mitogen-activated protein kinase pathway, does not suppress the defect in filamentation. These results indicate that CaGpr1 functions upstream in the cAMP-protein kinase A (PKA) pathway. We also show that, in the presence of glucose, CaGpr1 is important for amino acid-induced transition from yeast to hyphal cells. Finally, as opposed to previous reports, we show that CaGpa2 acts downstream of CaGpr1 as activator of the cAMP-PKA pathway but that deletion of neither CaGpr1 nor CaGpa2 affects glucose-induced cAMP signaling. In contrast, the latter is abolished in strains lacking CaCdc25 or CaRas1, suggesting that the CaCdc25-CaRas1 rather than the CaGpr1-CaGpa2 module mediates glucose-induced cAMP signaling in C. albicans.
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Affiliation(s)
- Mykola M Maidan
- Department of Molecular Microbiology, Flanders Interuniversity Institute for Biotechnology (VIB) and Laboratory of Molecular Cell Biology, Katholieke Universiteit Leuven, Flanders, Belgium
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41
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Lemaire K, Van de Velde S, Van Dijck P, Thevelein JM. Glucose and sucrose act as agonist and mannose as antagonist ligands of the G protein-coupled receptor Gpr1 in the yeast Saccharomyces cerevisiae. Mol Cell 2004; 16:293-9. [PMID: 15494315 DOI: 10.1016/j.molcel.2004.10.004] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 08/03/2004] [Accepted: 08/10/2004] [Indexed: 11/26/2022]
Abstract
Several examples of G protein-coupled receptors have recently been suggested to respond to common sugars in millimolar concentrations. This low affinity has made it difficult to demonstrate direct receptor-ligand interaction. In the yeast Saccharomyces cerevisiae, rapid activation of the cAMP pathway by glucose and sucrose requires the GPCR Gpr1. Our results obtained by cysteine scanning mutagenesis and SCAM (substituted cysteine accessibility method) of residues in TMD VI provide strong evidence that glucose and sucrose directly interact as ligands with Gpr1. The affinity for sucrose is much higher. Structurally similar sugars such as galactose, mannose, and fructose do not act as agonists, but mannose acts as an antagonist for both sucrose and glucose. These results support the idea that Gpr1 directly senses sugars and that sugars can effectively bind GPCRs with a low affinity in a binding pocket formed by the transmembrane domains. The ligand repertoire of GPCRs can thus be extended to common sugars in millimolar concentrations.
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Affiliation(s)
- Katleen Lemaire
- Laboratorium voor Moleculaire Celbiologie, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, B-3001 Leuven-Heverlee, Flanders, Belgium
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42
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Hedbacker K, Townley R, Carlson M. Cyclic AMP-dependent protein kinase regulates the subcellular localization of Snf1-Sip1 protein kinase. Mol Cell Biol 2004; 24:1836-43. [PMID: 14966266 PMCID: PMC350547 DOI: 10.1128/mcb.24.5.1836-1843.2004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Snf1/AMP-activated protein kinase family has diverse roles in cellular responses to metabolic stress. In Saccharomyces cerevisiae, Snf1 protein kinase has three isoforms of the beta subunit that confer versatility on the kinase and that exhibit distinct patterns of subcellular localization. The Sip1 beta subunit resides in the cytosol in glucose-grown cells and relocalizes to the vacuolar membrane in response to carbon stress. We show that translation of Sip1 initiates at the second ATG of the open reading frame, yielding a potential site for N myristoylation, and that mutation of the critical glycine abolishes relocalization. We further show that the cyclic AMP-dependent protein kinase (protein kinase A [PKA]) pathway maintains the cytoplasmic localization of Sip1 in glucose-grown cells. The Snf1 catalytic subunit also exhibits aberrant localization to the vacuolar membrane in PKA-deficient cells, indicating that PKA regulates the localization of Snf1-Sip1 protein kinase. These findings establish a novel mechanism of regulation of Snf1 protein kinase by the PKA pathway.
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Affiliation(s)
- Kristina Hedbacker
- Department of Genetics and Development, Columbia University, New York, New York 10032, USA
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43
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Li XY, Yang Z, Greenwood MT. Gα protein dependent and independent effects of human RGS1 expression in yeast. Cell Signal 2004; 16:43-9. [PMID: 14607274 DOI: 10.1016/s0898-6568(03)00096-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Regulators of G-protein Signalling (RGS) regulate the functional lifetime of G-Protein Coupled Receptor (GPCR)-activated heterotrimeric G-protein by serving as GTPase Accelerating Proteins (GAPs) for the G(alpha) subunit. A number of mammalian RGSs can functionally replace the yeast RGS containing SST2 gene and inhibit GPCR signalling. Using yeast strains harbouring a G(betagamma)-responsive FUS1-LacZ reporter gene, we demonstrate that heterologously expressed mammalian RGS1 also serves to decrease basal signalling in the absence of agonist. Although this effect was dependent on the expression of a GPA1-encoded functional G(alpha) protein, the GPCR itself was nevertheless not required. Using the GAL1 inducible promoter to express RGS1, we further demonstrate that in addition to serving as a GAP for Gpa1p in yeast, RGS1 is a dosage-dependent inhibitor of growth. This effect is specific to RGS1 since growth is not altered in cells expressing either mammalian RGS2 or RGS5. We further demonstrate that neither of the two yeast G(alpha) proteins is responsible for mediating this growth inhibitory effect of RGS1. Taken together, our results indicate that RGS1 can function in both G-protein-dependent and -independent manners in yeast.
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Affiliation(s)
- Xiao Yu Li
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
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44
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Batlle M, Lu A, Green DA, Xue Y, Hirsch JP. Krh1p and Krh2p act downstream of the Gpa2p G(alpha) subunit to negatively regulate haploid invasive growth. J Cell Sci 2003; 116:701-10. [PMID: 12538771 DOI: 10.1242/jcs.00266] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The yeast G(alpha) subunit Gpa2p and its coupled receptor Gpr1p function in a signaling pathway that is required for the transition to pseudohyphal and invasive growth. A two-hybrid screen using a constitutively active allele of GPA2 identified the KRH1 gene as encoding a potential binding partner of Gpa2p. Strains containing deletions of KRH1 and its homolog KRH2 were hyper-invasive and displayed a high level of expression of FLO11, a gene involved in pseudohyphal and invasive growth. Therefore, KRH1 and KRH2 encode negative regulators of the invasive growth pathway. Cells containing krh1Delta krh2Delta mutations also displayed increased sensitivity to heat shock and decreased sporulation efficiency, indicating that Krh1p and Krh2p regulate multiple processes controlled by the cAMP/PKA pathway. The krh1Delta krh2Delta mutations suppressed the effect of a gpa2Delta mutation on FLO11 expression and eliminated the effect of a constitutively active GPA2 allele on induction of FLO11 and heat shock sensitivity, suggesting that Krh1p and Krh2p act downstream of Gpa2p. The Sch9p kinase was not required for the signal generated by deletion of KRH1 and KRH2; however, the cAMP-dependent kinase Tpk2p was required for generation of this signal. These results support a model in which activation of Gpa2p relieves the inhibition exerted by Krh1p and Krh2p on components of the cAMP/PKA signaling pathway.
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Affiliation(s)
- Montserrat Batlle
- Brookdale Department of Molecular, Cell, and Developmental Biology, Mount Sinai School of Medicine, New York, NY 10029, USA
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45
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Gagiano M, Bauer FF, Pretorius IS. The sensing of nutritional status and the relationship to filamentous growth in Saccharomyces cerevisiae. FEMS Yeast Res 2002; 2:433-70. [PMID: 12702263 DOI: 10.1111/j.1567-1364.2002.tb00114.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Heterotrophic organisms rely on the ingestion of organic molecules or nutrients from the environment to sustain energy and biomass production. Non-motile, unicellular organisms have a limited ability to store nutrients or to take evasive action, and are therefore most directly dependent on the availability of nutrients in their immediate surrounding. Such organisms have evolved numerous developmental options in order to adapt to and to survive the permanently changing nutritional status of the environment. The phenotypical, physiological and molecular nature of nutrient-induced cellular adaptations has been most extensively studied in the yeast Saccharomyces cerevisiae. These studies have revealed a network of sensing mechanisms and of signalling pathways that generate and transmit the information on the nutritional status of the environment to the cellular machinery that implements specific developmental programmes. This review integrates our current knowledge on nutrient sensing and signalling in S. cerevisiae, and suggests how an integrated signalling network may lead to the establishment of a specific developmental programme, namely pseudohyphal differentiation and invasive growth.
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Affiliation(s)
- Marco Gagiano
- Institute for Wine Biotechnology, Department of Viticulture and Oenology, Stellenbosch University, South Africa
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46
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Winderickx J, Holsbeeks I, Lagatie O, Giots F, Thevelein J, de Winde H. From feast to famine; adaptation to nutrient availability in yeast. ACTA ACUST UNITED AC 2002. [DOI: 10.1007/3-540-45611-2_7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
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47
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Wang X, Bali M, Medintz I, Michels CA. Intracellular maltose is sufficient to induce MAL gene expression in Saccharomyces cerevisiae. EUKARYOTIC CELL 2002; 1:696-703. [PMID: 12455689 PMCID: PMC126750 DOI: 10.1128/ec.1.5.696-703.2002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The presence of maltose induces M4L gene expression in Saccharomyces cells, but little is known abouthow maltose is sensed. Strains with all maltose permease genes deleted are unable to induce MAL geneexpression. In this study, we examined the role of maltose permease in maltose sensing by substituting a heterologous transporter for the native maltose permease. PmSUC2 encodes a sucrose transporter from the dicot plant Plantago major that exhibits no significant sequence homology to maltose permease. When expressed in Saccharomyces cerevisiae, PmSUC2 is capable of transporting maltose, albeit at a reduced rate. We showed that introduction of PmSUC2 restores maltose-inducible MAL gene expression to a maltose permease-null mutant and that this induction requires the MAL activator. These data indicate that intracellular maltose is sufficient to induce MAL gene expression independently of the mechanism of maltose transport. By usingstrains expressing defective mal61 mutant alleles, we demonstrated a correlation between the rate of maltose transport and the level of the induction, which is particularly evident in medium containing very limiting concentrations of maltose. Moreover, our results indicate that a rather low concentration of intracellular maltose is needed to trigger MAL gene expression. We also showed that constitutive overexpression of either MAL61 maltose permease or PmSUC2 suppresses the noninducible phenotype of a defective mal13 MAL-activator allele, suggesting that this suppression is solely a function of maltose transport activity and is not specific to the sequence of the permease. Our studies indicate that maltose permease does not function as the maltose sensor in S. cerevisiae.
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Affiliation(s)
- Xin Wang
- Queens College and Graduate School of City University of New York, Biology Department, Flushing, New York 11367, USA
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48
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Harashima T, Heitman J. The Galpha protein Gpa2 controls yeast differentiation by interacting with kelch repeat proteins that mimic Gbeta subunits. Mol Cell 2002; 10:163-73. [PMID: 12150916 DOI: 10.1016/s1097-2765(02)00569-5] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
G protein coupled receptors (GPCR) sense diverse ligands and signal via heterotrimeric G proteins. The Saccharomyces cerevisiae GPCR Gpr1 senses glucose and controls filamentous growth via an unusual Galpha protein, Gpa2, which lacks any known Gbetagamma subunits. Our genetic and biochemical studies identify Gpa2 interaction partners (Gpb1/2, Gpg1) and provide evidence that these proteins function as G protein subunit mimics and signaling effectors. Gpb1 and Gpb2 lack the seven WD-40 repeats found in Gbeta subunits and instead contain seven kelch repeats implicated in protein-protein interactions. Gbeta subunits and the kelch repeat protein galactose oxidase fold into strikingly similar seven-bladed beta propellers. Our studies demonstrate that Gpa2 signals in conjunction with Gbeta structural mimics and that homologous G protein subunits or effectors may be conserved in multicellular eukaryotes.
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Affiliation(s)
- Toshiaki Harashima
- Department of Molecular Genetics and Microbiology, Durham, North Carolina 27710, USA
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49
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Palecek SP, Parikh AS, Kron SJ. Sensing, signalling and integrating physical processes during Saccharomyces cerevisiae invasive and filamentous growth. MICROBIOLOGY (READING, ENGLAND) 2002; 148:893-907. [PMID: 11932437 DOI: 10.1099/00221287-148-4-893] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Sean P Palecek
- Department of Chemical Engineering, University of Wisconsin - Madison, Madison, WI 53706, USA1
| | - Archita S Parikh
- Center for Molecular Oncology2 and Department of Molecular Genetics and Cell Biology3, The University of Chicago, Chicago, IL 60637, USA
| | - Stephen J Kron
- Center for Molecular Oncology2 and Department of Molecular Genetics and Cell Biology3, The University of Chicago, Chicago, IL 60637, USA
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50
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Abstract
Two well characterized signal transduction cascades regulating fungal development and virulence are the MAP kinase and cAMP signaling cascades. Here we review the current state of knowledge on cAMP signaling cascades in fungi. While the processes regulated by cAMP signaling in fungi are as diverse as the fungi themselves, the components involved in signal transduction are remarkably conserved. Fungal cAMP signaling cascades are also quite versatile, which is apparent from the differential regulation of similar biological processes. In this review we compare and contrast cAMP signaling pathways that regulate development in the budding yeast Saccharomyces cerevisiae, the fission yeast Schizosaccharomyces pombe, and differentiation and virulence in the human pathogen Cryptococcus neoformans and the plant pathogen Ustilago maydis. We also present examples of interaction between the cAMP and MAP kinase signaling cascades in the regulation of fungal development and virulence.
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Affiliation(s)
- C A D'Souza
- Department of Genetics 322 CARL Bldg, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
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