401
|
Abstract
Eukaryotic cells respond to intracellular and extracellular cues to direct asymmetric cell growth and division. The yeast Saccharomyces cerevisiae undergoes polarized growth at several times during budding and mating and is a useful model organism for studying asymmetric growth and division. In recent years, many regulatory and cytoskeletal components important for directing and executing growth have been identified, and molecular mechanisms have been elucidated in yeast. Key signaling pathways that regulate polarization during the cell cycle and mating response have been described. Since many of the components important for polarized cell growth are conserved in other organisms, the basic mechanisms mediating polarized cell growth are likely to be universal among eukaryotes.
Collapse
Affiliation(s)
- K Madden
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | | |
Collapse
|
402
|
Widmann C, Gibson S, Jarpe MB, Johnson GL. Mitogen-activated protein kinase: conservation of a three-kinase module from yeast to human. Physiol Rev 1999; 79:143-80. [PMID: 9922370 DOI: 10.1152/physrev.1999.79.1.143] [Citation(s) in RCA: 1961] [Impact Index Per Article: 78.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitogen-activated protein kinases (MAPK) are serine-threonine protein kinases that are activated by diverse stimuli ranging from cytokines, growth factors, neurotransmitters, hormones, cellular stress, and cell adherence. Mitogen-activated protein kinases are expressed in all eukaryotic cells. The basic assembly of MAPK pathways is a three-component module conserved from yeast to humans. The MAPK module includes three kinases that establish a sequential activation pathway comprising a MAPK kinase kinase (MKKK), MAPK kinase (MKK), and MAPK. Currently, there have been 14 MKKK, 7 MKK, and 12 MAPK identified in mammalian cells. The mammalian MAPK can be subdivided into five families: MAPKerk1/2, MAPKp38, MAPKjnk, MAPKerk3/4, and MAPKerk5. Each MAPK family has distinct biological functions. In Saccharomyces cerevisiae, there are five MAPK pathways involved in mating, cell wall remodelling, nutrient deprivation, and responses to stress stimuli such as osmolarity changes. Component members of the yeast pathways have conserved counterparts in mammalian cells. The number of different MKKK in MAPK modules allows for the diversity of inputs capable of activating MAPK pathways. In this review, we define all known MAPK module kinases from yeast to humans, what is known about their regulation, defined MAPK substrates, and the function of MAPK in cell physiology.
Collapse
Affiliation(s)
- C Widmann
- Program in Molecular Signal Transduction, Division of Basic Sciences, National Jewish Medical and Research Center, Denver, Colorado, USA
| | | | | | | |
Collapse
|
403
|
Gagiano M, van Dyk D, Bauer FF, Lambrechts MG, Pretorius IS. Msn1p/Mss10p, Mss11p and Muc1p/Flo11p are part of a signal transduction pathway downstream of Mep2p regulating invasive growth and pseudohyphal differentiation in Saccharomyces cerevisiae. Mol Microbiol 1999; 31:103-16. [PMID: 9987114 DOI: 10.1046/j.1365-2958.1999.01151.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Saccharomyces cerevisiae, a network of signal transduction pathways governs the switch from yeast-type growth to pseudohyphal and invasive growth that occurs in response to nutrient limitation. Important elements of this network have been identified, including nutrient signal receptors, GTP-binding proteins, components of the pheromone-dependent MAP kinase cascade and several transcription factors. However, the structural and functional mapping of these pathways is far from complete. Here, we present data regarding three genes, MSN1/MSS10, MSS11 and MUC1/FLO11, which form an essential part of the signal transduction network establishing invasive growth. Both MSN1 and MSS11 are involved in the co-regulation of starch degradation and invasive growth. Msn1p and Mss11p act downstream of Mep2p and Ras2p and regulate the transcription of both STA2 and MUC1. We show that MUC1 mediates the effect of Msn1p and Mss11p on invasive growth. In addition, our results suggest that the activity of Msn1p is independent of the invasive growth MAP kinase cascade, but the Mss11p is required for the activation of pseudohyphal and invasive growth by Ste12p. We also show that starch metabolism in S. cerevisiae is subject to regulation by components of the MAP kinase cascade.
Collapse
Affiliation(s)
- M Gagiano
- Institute for Wine Biotechnology, University of Stellenbosch, South Africa
| | | | | | | | | |
Collapse
|
404
|
Bardwell L, Cook JG, Zhu-Shimoni JX, Voora D, Thorner J. Differential regulation of transcription: repression by unactivated mitogen-activated protein kinase Kss1 requires the Dig1 and Dig2 proteins. Proc Natl Acad Sci U S A 1998; 95:15400-5. [PMID: 9860980 PMCID: PMC28054 DOI: 10.1073/pnas.95.26.15400] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/1998] [Accepted: 10/21/1998] [Indexed: 11/18/2022] Open
Abstract
Kss1, a yeast mitogen-activated protein kinase (MAPK), in its unphosphorylated (unactivated) state binds directly to and represses Ste12, a transcription factor necessary for expression of genes whose promoters contain filamentous response elements (FREs) and genes whose promoters contain pheromone response elements (PREs). Herein we show that two nuclear proteins, Dig1 and Dig2, are required cofactors in Kss1-imposed repression. Dig1 and Dig2 cooperate with Kss1 to repress Ste12 action at FREs and regulate invasive growth in a naturally invasive strain. Kss1-imposed Dig-dependent repression of Ste12 also occurs at PREs. However, maintenance of repression at PREs is more dependent on Dig1 and/or Dig2 and less dependent on Kss1 than repression at FREs. In addition, derepression at PREs is more dependent on MAPK-mediated phosphorylation than is derepression at FREs. Differential utilization of two types of MAPK-mediated regulation (binding-imposed repression and phosphorylation-dependent activation), in combination with distinct Ste12-containing complexes, contributes to the mechanisms by which separate extracellular stimuli that use the same MAPK cascade can elicit two different transcriptional responses.
Collapse
Affiliation(s)
- L Bardwell
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA
| | | | | | | | | |
Collapse
|
405
|
Gustin MC, Albertyn J, Alexander M, Davenport K. MAP kinase pathways in the yeast Saccharomyces cerevisiae. Microbiol Mol Biol Rev 1998; 62:1264-300. [PMID: 9841672 PMCID: PMC98946 DOI: 10.1128/mmbr.62.4.1264-1300.1998] [Citation(s) in RCA: 703] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A cascade of three protein kinases known as a mitogen-activated protein kinase (MAPK) cascade is commonly found as part of the signaling pathways in eukaryotic cells. Almost two decades of genetic and biochemical experimentation plus the recently completed DNA sequence of the Saccharomyces cerevisiae genome have revealed just five functionally distinct MAPK cascades in this yeast. Sexual conjugation, cell growth, and adaptation to stress, for example, all require MAPK-mediated cellular responses. A primary function of these cascades appears to be the regulation of gene expression in response to extracellular signals or as part of specific developmental processes. In addition, the MAPK cascades often appear to regulate the cell cycle and vice versa. Despite the success of the gene hunter era in revealing these pathways, there are still many significant gaps in our knowledge of the molecular mechanisms for activation of these cascades and how the cascades regulate cell function. For example, comparison of different yeast signaling pathways reveals a surprising variety of different types of upstream signaling proteins that function to activate a MAPK cascade, yet how the upstream proteins actually activate the cascade remains unclear. We also know that the yeast MAPK pathways regulate each other and interact with other signaling pathways to produce a coordinated pattern of gene expression, but the molecular mechanisms of this cross talk are poorly understood. This review is therefore an attempt to present the current knowledge of MAPK pathways in yeast and some directions for future research in this area.
Collapse
Affiliation(s)
- M C Gustin
- Department of Biochemistry and Cell Biology Rice University, Houston, Texas 77251-1892, USA.
| | | | | | | |
Collapse
|
406
|
Sipiczki M, Takeo K, Grallert A. Growth polarity transitions in a dimorphic fission yeast. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 12):3475-3485. [PMID: 9884240 DOI: 10.1099/00221287-144-12-3475] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Fission yeast cells grow by extension at the ends (poles) and divide by transverse fission. It has previously been reported that Schizosaccharomyces japonicus var. japonicus can switch to unipolar, filamentous growth. Here it is shown that the yeast-to-mycelium transition is a gradual process involving a changeover to unipolar growth associated with asymmetric divisions, the development of large polarly located vacuoles, the modifications of the actin and microtubular cytoskeleton and the repression of cell separation after division. High concentrations of glucose in the medium or supplementation of the medium with caffeine or cAMP support the bipolar yeast phase, inhibit the transition to the mycelial phase and induce the conversion of hyphae to yeasts. These effects suggest that cAMP may be involved in the regulation of dimorphism. Temperatures below 18 degrees C or over 35 degrees C are restrictive for the mycelial phase and provoke a return to yeast phase.
Collapse
Affiliation(s)
- M Sipiczki
- Institute of Biology, University of Debrecen, PO Box 56, H-4010 Debrecen, Hungary
- Department of Genetics, University of Debrecen, PO Box 56, H-4010 Debrecen, Hungary
| | - K Takeo
- Division of Ultrastructure and Function, Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chiba, Japan
| | - A Grallert
- Department of Genetics, University of Debrecen, PO Box 56, H-4010 Debrecen, Hungary
| |
Collapse
|
407
|
Dowell SJ, Bishop AL, Dyos SL, Brown AJ, Whiteway MS. Mapping of a yeast G protein betagamma signaling interaction. Genetics 1998; 150:1407-17. [PMID: 9832519 PMCID: PMC1460424 DOI: 10.1093/genetics/150.4.1407] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The mating pathway of Saccharomyces cerevisiae is widely used as a model system for G protein-coupled receptor-mediated signal transduction. Following receptor activation by the binding of mating pheromones, G protein betagamma subunits transmit the signal to a MAP kinase cascade, which involves interaction of Gbeta (Ste4p) with the MAP kinase scaffold protein Ste5p. Here, we identify residues in Ste4p required for the interaction with Ste5p. These residues define a new signaling interface close to the Ste20p binding site within the Gbetagamma coiled-coil. Ste4p mutants defective in the Ste5p interaction interact efficiently with Gpa1p (Galpha) and Ste18p (Ggamma) but cannot function in signal transduction because cells expressing these mutants are sterile. Ste4 L65S is temperature-sensitive for its interaction with Ste5p, and also for signaling. We have identified a Ste5p mutant (L196A) that displays a synthetic interaction defect with Ste4 L65S, providing strong evidence that Ste4p and Ste5p interact directly in vivo through an interface that involves hydrophobic residues. The correlation between disruption of the Ste4p-Ste5p interaction and sterility confirms the importance of this interaction in signal transduction. Identification of the Gbetagamma coiled-coil in Ste5p binding may set a precedent for Gbetagamma-effector interactions in more complex organisms.
Collapse
Affiliation(s)
- S J Dowell
- Glaxo Wellcome Research and Development, Stevenage, SG1 2NY, United Kingdom.
| | | | | | | | | |
Collapse
|
408
|
Lorenz MC, Heitman J. Regulators of pseudohyphal differentiation in Saccharomyces cerevisiae identified through multicopy suppressor analysis in ammonium permease mutant strains. Genetics 1998; 150:1443-57. [PMID: 9832522 PMCID: PMC1460428 DOI: 10.1093/genetics/150.4.1443] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nitrogen-starved diploid cells of the yeast Saccharomyces cerevisiae differentiate into a filamentous, pseudohyphal growth form. Recognition of nitrogen starvation is mediated, at least in part, by the ammonium permease Mep2p and the Galpha subunit Gpa2p. Genetic activation of the pheromone-responsive MAP kinase cascade, which is also required for filamentous growth, only weakly suppresses the filamentation defect of Deltamep2/Deltamep2 and Deltagpa2/Deltagpa2 strain. Surprisingly, deletion of Mep1p, an ammonium permease not previously thought to regulate differentiation, significantly enhances the potency of MAP kinase activation, such that the STE11-4 allele induces filamentation to near wild-type levels in Deltamep1/Deltamep1 Deltamep2/Deltamep2 and Deltamep1/Deltamep1 Deltagpa2/Deltagpa2 strains. To identify additional regulatory components, we isolated high-copy suppressors of the filamentation defect of the Deltamep1/Deltamep1 Deltamep2/Deltamep2 mutant. Multicopy expression of TEC1, PHD1, PHD2 (MSS10/MSN1/FUP4), MSN5, CDC6, MSS11, MGA1, SKN7, DOT6, HMS1, HMS2, or MEP2 each restored filamentation in a Deltamep1/Deltamep1 Deltamep2/Deltamep2 strain. Overexpression of SRK1 (SSD1), URE2, DAL80, MEP1, or MEP3 suppressed only the growth defect of the Deltamep1/Deltamep1 Deltamep2/Deltamep2 mutant strain. Characterization of these genes through deletion analysis and epistasis underscores the complexity of this developmental pathway and suggests that stress conditions other than nitrogen deprivation may also promote filamentous growth.
Collapse
Affiliation(s)
- M C Lorenz
- Department of Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | |
Collapse
|
409
|
Robertson LS, Fink GR. The three yeast A kinases have specific signaling functions in pseudohyphal growth. Proc Natl Acad Sci U S A 1998; 95:13783-7. [PMID: 9811878 PMCID: PMC24897 DOI: 10.1073/pnas.95.23.13783] [Citation(s) in RCA: 263] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/1998] [Indexed: 11/18/2022] Open
Abstract
The three yeast A kinase catalytic subunit isoforms are redundant for viability. We demonstrate that they have dramatically different roles in pseudohyphal development: Tpk2 is essential, whereas Tpk3 inhibits. Tpk1 has no discernible effect. Two-hybrid analysis identified the transcription factor Sfl1 as a protein that interacts specifically with Tpk2, but not Tpk1 or Tpk3. Deletion of SFL1 enhances pseudohyphal and invasive growth. Flo11, a cell surface flocculin required for pseudohyphal development, is transcriptionally regulated by Tpk2 and Sfl1. Genetic evidence indicates that Tpk2 acts upstream of Sfl1 in the regulation of Flo11.
Collapse
Affiliation(s)
- L S Robertson
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA
| | | |
Collapse
|
410
|
Xia Y, Wu Z, Su B, Murray B, Karin M. JNKK1 organizes a MAP kinase module through specific and sequential interactions with upstream and downstream components mediated by its amino-terminal extension. Genes Dev 1998; 12:3369-81. [PMID: 9808624 PMCID: PMC317229 DOI: 10.1101/gad.12.21.3369] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/1998] [Accepted: 09/04/1998] [Indexed: 11/24/2022]
Abstract
MAP kinase (MAPK) cascades are composed of a MAPK, MAPK kinase (MAPKK), and a MAPKK kinase (MAPKKK). Despite the existence of numerous components and ample opportunities for crosstalk, most MAPKs are specifically and distinctly activated. We investigated the basis for specific activation of the JNK subgroup of MAPKs. The specificity of JNK activation is determined by the MAPKK JNKK1, which interacts with the MAPKKK MEKK1 and JNK through its amino-terminal extension. Inactive JNKK1 mutants can disrupt JNK activation by MEKK1 or tumor necrosis factor (TNF) in intact cells only if they contain an intact amino-terminal extension. Mutations in this region interfere with the ability of JNKK1 to respond to TNF but do not affect its activation by physical stressors. As JNK and MEKK1 compete for binding to JNKK1 and activation of JNKK1 prevents its binding to MEKK1, activation of this module is likely to occur through sequential MEKK1:JNKK1 and JNKK1:JNK interactions. These results underscore a role for the amino-terminal extension of MAPKKs in determination of response specificity.
Collapse
Affiliation(s)
- Y Xia
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, University of California San Diego, La Jolla, California 92093-0636 USA
| | | | | | | | | |
Collapse
|
411
|
Wu C, Leeuw T, Leberer E, Thomas DY, Whiteway M. Cell cycle- and Cln2p-Cdc28p-dependent phosphorylation of the yeast Ste20p protein kinase. J Biol Chem 1998; 273:28107-15. [PMID: 9774429 DOI: 10.1074/jbc.273.43.28107] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ste20p from Saccharomyces cerevisiae is a member of the Ste20/p21-activated protein kinase family of protein kinases. The Ste20p kinase is post-translationally modified by phosphorylation in a cell cycle-dependent manner, as judged by the appearance of phosphatase-sensitive species with reduced mobility on SDS-polyacrylamide gel electrophoresis. This modification is maximal during S phase, and correlates with the accumulation of Ste20p fused to green fluorescent protein at the site of bud emergence. Overexpression of Cln2p, but not Clb2p or Clb5p, causes a quantitative shift of Ste20p to the reduced mobility form, and this shift is dependent on Cdc28p activity. The post-translational mobility shift can be generated in vitro by incubation of Ste20p with immunoprecipitated Cln2p kinase complexes, but not by immunoprecipitated Clb2p or Clb5p kinase complexes. Ste20p is therefore a substrate for the Cdc28p kinase, and undergoes a Cln2p-Cdc28p mediated mobility shift as cells initiate budding and DNA replication. In cells that express only the Cln2p G1 cyclin, minor overexpression of Ste20p causes aberrant morphology, suggesting a proper coordination of Ste20p and Cln-Cdc28p activity may be required for the control of cell shape.
Collapse
Affiliation(s)
- C Wu
- Eukaryotic Genetics Group, Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec H4P 2R2
| | | | | | | | | |
Collapse
|
412
|
Oehlen LJ, Cross FR. Potential regulation of Ste20 function by the Cln1-Cdc28 and Cln2-Cdc28 cyclin-dependent protein kinases. J Biol Chem 1998; 273:25089-97. [PMID: 9737966 DOI: 10.1074/jbc.273.39.25089] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of the Saccharomyces cerevisiae pheromone signal transduction pathway is regulated by Cln1/2-Cdc28 cyclin-dependent kinase. High level expression of CLN2 can repress activation of the pathway by mating factor or by deletion of the alpha-subunit of the heterotrimeric G-protein. We now show that CLN2 overexpression can also repress FUS1 induction if the signaling pathway is activated at the level of the beta-subunit of the G-protein (STE4) but not when activated at the level of downstream kinases (STE20 and STE11) or at the level of the transcription factor STE12. This epistatic analysis indicates that repression of pheromone signaling pathway by Cln2-Cdc28 kinase takes place at a level around STE20. In agreement with this, a marked reduction in the electrophoretic mobility of the Ste20 protein is observed at the time in the cell cycle of maximal expression of CLN2. This mobility change is constitutive in cells overexpressing CLN2 and absent in cells lacking CLN1 and CLN2. These changes in electrophoretic mobility correlate with repression of pheromone signaling and suggest Ste20 as a target for repression of signaling by G1 cyclins. Two morphogenic pathways for which Ste20 is essential, pseudohyphal differentiation and haploid-invasive growth, also require CLN1 and CLN2. Together with the previous observation that Cln1 and Cln2 are required for the function of Ste20 in cytokinesis, this suggests that Cln1 and Cln2 regulate the biological activity of Ste20 by promoting morphogenic functions, while inhibiting the mating factor signal transduction function.
Collapse
Affiliation(s)
- L J Oehlen
- Rockefeller University, New York, New York 10021, USA.
| | | |
Collapse
|
413
|
Bardwell L, Cook JG, Voora D, Baggott DM, Martinez AR, Thorner J. Repression of yeast Ste12 transcription factor by direct binding of unphosphorylated Kss1 MAPK and its regulation by the Ste7 MEK. Genes Dev 1998; 12:2887-98. [PMID: 9744865 PMCID: PMC317171 DOI: 10.1101/gad.12.18.2887] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/1998] [Accepted: 07/24/1998] [Indexed: 11/25/2022]
Abstract
The mitogen-activated protein kinase (MAPK) Kss1 has a dual role in regulating filamentous (invasive) growth of the yeast Saccharomyces cerevisiae. The stimulatory function of Kss1 requires both its catalytic activity and its activation by the MAPK/ERK kinase (MEK) Ste7; in contrast, the inhibitory function of Kss1 requires neither. This study examines the mechanism by which Kss1 inhibits invasive growth, and how Ste7 action overcomes this inhibition. We found that unphosphorylated Kss1 binds directly to the transcription factor Ste12, that this binding is necessary for Kss1-mediated repression of Ste12, and that Ste7-mediated phosphorylation of Kss1 weakens Kss1-Ste12 interaction and relieves Kss1-mediated repression. Relative to Kss1, the MAPK Fus3 binds less strongly to Ste12 and is correspondingly a weaker inhibitor of invasive growth. Analysis of Kss1 mutants indicated that the activation loop of Kss1 controls binding to Ste12. Potent repression of a transcription factor by its physical interaction with the unactivated isoform of a protein kinase, and relief of this repression by activation of the kinase, is a novel mechanism for signal-dependent regulation of gene expression.
Collapse
Affiliation(s)
- L Bardwell
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, California 94720, USA
| | | | | | | | | | | |
Collapse
|
414
|
O'Rourke SM, Herskowitz I. The Hog1 MAPK prevents cross talk between the HOG and pheromone response MAPK pathways in Saccharomyces cerevisiae. Genes Dev 1998; 12:2874-86. [PMID: 9744864 PMCID: PMC317168 DOI: 10.1101/gad.12.18.2874] [Citation(s) in RCA: 313] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The MAPKKK Ste11p functions in three Saccharomyces cerevisiae MAPK cascades [the high osmolarity glycerol (HOG), pheromone response, and pseudohyphal/invasive growth pathways], but its activation in response to high osmolarity stimulates only the HOG pathway. To determine what restricts cross-activation of MAPK cascades (cross talk), we have studied mutants in which the pheromone response pathway is activated by high osmolarity (1 M sorbitol). We found that mutations in the HOG1 gene, encoding the p38-type MAPK of the HOG pathway, and in the PBS2 gene, encoding the activating kinase for Hog1p, allowed osmolarity-induced activation of the pheromone response pathway. This cross talk required the osmosensor Sho1p, as well as Ste20p, Ste50p, the pheromone response MAPK cascade (Ste11p, Ste7p, and Fus3p or Kss1p), and Ste12p but not Ste4p or the MAPK scaffold protein, Ste5p. The cross talk in hog1 mutants induced multiple responses of the pheromone response pathway: induction of a FUS1::lacZ reporter, morphological changes, and mating in ste4 and ste5 mutants. We suggest that Hog1p may prevent osmolarity-induced cross talk by inhibiting Sho1p, perhaps as part of a feedback control on the HOG pathway. We have also shown that Ste20p and Ste50p function in the Sho1p branch of the HOG pathway and that a second osmosensor in addition to Sho1p may activate Ste11p. Finally, we have found that pseudohyphal growth exhibited by wild-type (HOG1) strains depends on SHO1, suggesting that Sho1p may be a receptor that feeds into the pseudohyphal growth pathway.
Collapse
Affiliation(s)
- S M O'Rourke
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94143-0448, USA
| | | |
Collapse
|
415
|
Abstract
Many members of the fungal kingdom have a distinguishing feature, dimorphism, which is the ability to switch between two morphological forms: a cellular yeast form and a multicellular invasive filamentous form. At least three pathways are involved in regulating the transition between these two forms in the budding yeast Saccharomyces cerevisiae, and evidence is now emerging that homologous signalling modules are involved in regulating filament formation and virulence in a range of human and plant fungal pathogens. Strikingly, components used to signal sexual differentiation in the response to mating pheromones are often reutilized to regulate dimorphic development, suggesting an ancient link between these processes.
Collapse
Affiliation(s)
- H D Madhani
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142, USA.
| | | |
Collapse
|
416
|
Engelberg D, Mimran A, Martinetto H, Otto J, Simchen G, Karin M, Fink GR. Multicellular stalk-like structures in Saccharomyces cerevisiae. J Bacteriol 1998; 180:3992-6. [PMID: 9683500 PMCID: PMC107387 DOI: 10.1128/jb.180.15.3992-3996.1998] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Stalk formation is a novel pattern of multicellular organization. Yeast cells which survive UV irradiation form colonies that grow vertically to form very long (0.5 to 3.0 cm) and thin (0.5 to 4 mm in diameter) multicellular structures. We describe the conditions required to obtain these stalk-like structures reproducibly in large numbers. Yeast mutants, mutated for control of cell polarity, developmental processes, UV response, and signal transduction cascades were tested and found capable of forming stalk-like structures. We suggest a model that explains the mechanism of stalk formation by mechanical environmental forces. We show that other microorganisms (Candida albicans, Schizosaccharomyces pombe, and Escherichia coli) also form stalks, suggesting that the ability to produce stalks may be a general property of microorganisms. Diploid yeast stalks sporulate at an elevated frequency, raising the possibility that the physiological role of stalks might be disseminating spores.
Collapse
Affiliation(s)
- D Engelberg
- Department of Biological Chemistry, The Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | | | | | | | | | | | | |
Collapse
|
417
|
Yang P, Kansra S, Pimental RA, Gilbreth M, Marcus S. Cloning and characterization of shk2, a gene encoding a novel p21-activated protein kinase from fission yeast. J Biol Chem 1998; 273:18481-9. [PMID: 9660817 DOI: 10.1074/jbc.273.29.18481] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We describe the characterization of a novel gene, shk2, encoding a second p21(cdc42/rac)-activated protein kinase (PAK) homolog in fission yeast. Like other known PAKs, Shk2 binds to Cdc42 in vivo and in vitro. While overexpression of either shk2 or cdc42 alone does not impair growth of wild type fission yeast cells, cooverexpression of the two genes is toxic and leads to highly aberrant cell morphology, providing evidence for functional interaction between Cdc42 and Shk2 proteins in vivo. Fission yeast shk2 null mutants are viable and exhibit no obvious phenotypic defects. Overexpression of shk2 restores viability and normal morphology but not full mating competence to fission yeast cells carrying a shk1 null mutation. Additional genetic data suggest that Shk2, like Cdc42 and Shk1, participates in Ras-dependent morphological control and mating response pathways in fission yeast. We also show that overexpression of byr2, a gene encoding a Ste11/MAPK kinase kinase homolog, suppresses the mating defect of cells partially defective for Shk1 function, providing evidence of a link between PAKs and mitogen-activated protein kinase signaling in fission yeast. Taken together, our results suggest that Shk2 is partially overlapping in function with Shk1, with Shk1 being the dominant protein in function.
Collapse
Affiliation(s)
- P Yang
- Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA
| | | | | | | | | |
Collapse
|
418
|
Sells MA, Barratt JT, Caviston J, Ottilie S, Leberer E, Chernoff J. Characterization of Pak2p, a pleckstrin homology domain-containing, p21-activated protein kinase from fission yeast. J Biol Chem 1998; 273:18490-8. [PMID: 9660818 DOI: 10.1074/jbc.273.29.18490] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p21-activated kinases (PAKs) bind to and are activated by Rho family GTPases such as Cdc42 and Rac. Since these GTPases play key roles in regulating cell polarity, stress responses, and cell cycle progression, the ability of PAK to affect these processes has been examined. We previously showed that fission yeast pak1+ encodes an essential protein that affects mating and cell polarity. Here, we characterize a second pak gene (pak2+) from Schizosaccharomyces pombe. Like the Saccharomyces cerevisiae proteins Cla4p and Skm1p, fission yeast Pak2p contains an N-terminal pleckstrin homology domain in addition to a p21-binding domain and a protein kinase domain that are common to other members of the PAK family. Unlike pak1+, pak2(+) is not essential for vegetative growth or for mating in S. pombe. Overexpression of the wild-type pak2+ allele suppresses the lethal growth defect associated with deletion of pak1+, and this suppression requires both the pleckstrin homology- and the p21-binding domains of Pak2p, as well as kinase activity. A substantial fraction of Pak2p is associated with membranous components, an association mediated both by the pleckstrin homology- and by the p21-binding domains. These results show that S. pombe encodes at least two pak genes with distinct functions and suggest that the membrane localization of Pak2p, directed by its interactions with membrane lipids and Cdc42p, is critical to its biological activity.
Collapse
Affiliation(s)
- M A Sells
- Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
| | | | | | | | | | | |
Collapse
|
419
|
Sheu YJ, Santos B, Fortin N, Costigan C, Snyder M. Spa2p interacts with cell polarity proteins and signaling components involved in yeast cell morphogenesis. Mol Cell Biol 1998; 18:4053-69. [PMID: 9632790 PMCID: PMC108990 DOI: 10.1128/mcb.18.7.4053] [Citation(s) in RCA: 199] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/1997] [Accepted: 04/07/1998] [Indexed: 02/07/2023] Open
Abstract
The yeast protein Spa2p localizes to growth sites and is important for polarized morphogenesis during budding, mating, and pseudohyphal growth. To better understand the role of Spa2p in polarized growth, we analyzed regions of the protein important for its function and proteins that interact with Spa2p. Spa2p interacts with Pea2p and Bud6p (Aip3p) as determined by the two-hybrid system; all of these proteins exhibit similar localization patterns, and spa2Delta, pea2Delta, and bud6Delta mutants display similar phenotypes, suggesting that these three proteins are involved in the same biological processes. Coimmunoprecipitation experiments demonstrate that Spa2p and Pea2p are tightly associated with each other in vivo. Velocity sedimentation experiments suggest that a significant portion of Spa2p, Pea2p, and Bud6p cosediment, raising the possibility that these proteins form a large, 12S multiprotein complex. Bud6p has been shown previously to interact with actin, suggesting that the 12S complex functions to regulate the actin cytoskeleton. Deletion analysis revealed that multiple regions of Spa2p are involved in its localization to growth sites. One of the regions involved in Spa2p stability and localization interacts with Pea2p; this region contains a conserved domain, SHD-II. Although a portion of Spa2p is sufficient for localization of itself and Pea2p to growth sites, only the full-length protein is capable of complementing spa2 mutant defects, suggesting that other regions are required for Spa2p function. By using the two-hybrid system, Spa2p and Bud6p were also found to interact with components of two mitogen-activated protein kinase (MAPK) pathways important for polarized cell growth. Spa2p interacts with Ste11p (MAPK kinase [MEK] kinase) and Ste7p (MEK) of the mating signaling pathway as well as with the MEKs Mkk1p and Mkk2p of the Slt2p (Mpk1p) MAPK pathway; for both Mkk1p and Ste7p, the Spa2p-interacting region was mapped to the N-terminal putative regulatory domain. Bud6p interacts with Ste11p. The MEK-interacting region of Spa2p corresponds to the highly conserved SHD-I domain, which is shown to be important for mating and MAPK signaling. spa2 mutants exhibit reduced levels of pheromone signaling and an elevated level of Slt2p kinase activity. We thus propose that Spa2p, Pea2p, and Bud6p function together, perhaps as a complex, to promote polarized morphogenesis through regulation of the actin cytoskeleton and signaling pathways.
Collapse
Affiliation(s)
- Y J Sheu
- Department of Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | | | | | | | | |
Collapse
|
420
|
Oehlen L, Cross FR. The mating factor response pathway regulates transcription of TEC1, a gene involved in pseudohyphal differentiation of Saccharomyces cerevisiae. FEBS Lett 1998; 429:83-8. [PMID: 9657388 DOI: 10.1016/s0014-5793(98)00568-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The transcription factor Tec1 is involved in pseudohyphal differentiation and agar-invasive growth of Saccharomyces cerevisiae cells. The sole element in the TEC1 promoter that has thus far been shown to control Tec1 function is the filament response element. We find that the TEC1 promoter also contains several pheromone response element sequences which are likely to be functional: TEC1 transcription is induced by mating factor, cell cycle regulated and dependent on the Ste4, Ste18 and Ste5 components of the mating factor signal transduction pathway. Using alleles of the transcription factor Ste12 that are defective in DNA binding, transcriptional induction or cooperativity with other transcription factors, we find little correlation between TEC1 transcript levels and agar-invasive growth.
Collapse
Affiliation(s)
- L Oehlen
- The Rockefeller University, New York, NY 10021, USA
| | | |
Collapse
|
421
|
Banuett F. Signalling in the yeasts: an informational cascade with links to the filamentous fungi. Microbiol Mol Biol Rev 1998; 62:249-74. [PMID: 9618441 PMCID: PMC98914 DOI: 10.1128/mmbr.62.2.249-274.1998] [Citation(s) in RCA: 204] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
All cells, from bacteria and yeasts to mammalian cells, respond to cues from their environment. A variety of mechanisms exist for the transduction of these external signals to the interior of the cell, resulting in altered patterns of protein activity. Eukaryotic cells commonly transduce external cues via a conserved module composed of three protein kinases, the mitogen-activated protein kinase (MAPK) cascade. This module can then activate substrates, some of which include transcriptional activators. Multiple MAPK signalling pathways coexist in a cell. This review considers different MAPK cascade signalling pathways that govern several aspects of the life cycle of budding and fission yeasts: conjugation and meiosis by the pheromone response pathway, stress response by the high-osmolarity sensing pathway, cell wall biosynthesis in response to activation of the low-osmolarity and heat-sensing pathway, and pseudohyphal growth in response to activation of a subset of the components of the pheromone response pathway. Because the MAPK cascade components are highly conserved, a key question in studies of these pathways is the mechanism by which specificity of response is achieved. Several other issues to be addressed in this review concern the nature of the receptors used to sense the external signals and the mechanism by which the receptors communicate with other components leading to activation of the MAPK cascade. Recently, it has become apparent that MAPK cascades are important in governing the pathogenicity of filamentous fungi.
Collapse
Affiliation(s)
- F Banuett
- Department of Biochemistry and Biophysics, School of Medicine, University of California, San Francisco, California 94143-0448, USA.
| |
Collapse
|
422
|
Csank C, Schröppel K, Leberer E, Harcus D, Mohamed O, Meloche S, Thomas DY, Whiteway M. Roles of the Candida albicans mitogen-activated protein kinase homolog, Cek1p, in hyphal development and systemic candidiasis. Infect Immun 1998; 66:2713-21. [PMID: 9596738 PMCID: PMC108260 DOI: 10.1128/iai.66.6.2713-2721.1998] [Citation(s) in RCA: 280] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Extracellular signal-regulated protein kinase (ERK, or mitogen-activated protein kinase [MAPK]) regulatory cascades in fungi turn on transcription factors that control developmental processes, stress responses, and cell wall integrity. CEK1 encodes a Candida albicans MAPK homolog (Cek1p), isolated by its ability to interfere with the Saccharomyces cerevisiae MAPK mating pathway. C. albicans cells with a deletion of the CEK1 gene are defective in shifting from a unicellular budding colonial growth mode to an agar-invasive hyphal growth mode when nutrients become limiting on solid medium with mannitol as a carbon source or on glucose when nitrogen is severely limited. The same phenotype is seen in C. albicans mutants in which the homologs (CST20, HST7, and CPH1) of the S. cerevisiae STE20, STE7, and STE12 genes are disrupted. In S. cerevisiae, the products of these genes function as part of a MAPK cascade required for mating and invasiveness of haploid cells and for pseudohyphal development of diploid cells. Epistasis studies revealed that the C. albicans CST20, HST7, CEK1, and CPH1 gene products lie in an equivalent, canonical, MAPK cascade. While Cek1p acts as part of the MAPK cascade involved in starvation-specific hyphal development, it may also play independent roles in C. albicans. In contrast to disruptions of the HST7 and CPH1 genes, disruption of the CEK1 gene adversely affects the growth of serum-induced mycelial colonies and attenuates virulence in a mouse model for systemic candidiasis.
Collapse
Affiliation(s)
- C Csank
- Eukaryotic Genetics Group, National Research Council of Canada, Biotechnology Research Institute, Montreal, Quebec H4P 2R2
| | | | | | | | | | | | | | | |
Collapse
|
423
|
Chandarlapaty S, Errede B. Ash1, a daughter cell-specific protein, is required for pseudohyphal growth of Saccharomyces cerevisiae. Mol Cell Biol 1998; 18:2884-91. [PMID: 9566907 PMCID: PMC110667 DOI: 10.1128/mcb.18.5.2884] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ash1 (for asymmetric synthesis of HO) was first uncovered in genetic screens that revealed its role in mating-type switching. Ash1 prevents HO expression in daughter cells. Because Ash1 has a zinc finger-like domain related to that of the GATA family of transcription factors, it presumably acts by repressing HO transcription. Nonswitching diploid cells also express Ash1, suggesting it could have functions in addition to regulation of HO expression. We show here that Ash1 has an essential function for pseudohyphal growth. Our epistasis analyses are consistent with the deduction that Ash1 acts separately from the mitogen-activated protein kinase cascade and Ste12. Similarly to the case in yeast form cells, Ash1 is asymmetrically localized to the nuclei of daughter cells during pseudohyphal growth. This asymmetric localization reveals that there is a previously unsuspected daughter cell-specific function necessary for pseudohyphal growth.
Collapse
Affiliation(s)
- S Chandarlapaty
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260, USA
| | | |
Collapse
|
424
|
Conte D, Barber E, Banerjee M, Garfinkel DJ, Curcio MJ. Posttranslational regulation of Ty1 retrotransposition by mitogen-activated protein kinase Fus3. Mol Cell Biol 1998; 18:2502-13. [PMID: 9566871 PMCID: PMC110630 DOI: 10.1128/mcb.18.5.2502] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/1997] [Accepted: 01/27/1998] [Indexed: 02/07/2023] Open
Abstract
Ty1 retrotransposons in Saccharomyces cerevisiae are maintained in a state of transpositional dormancy. We isolated a mutation, rtt100-1, that increases the transposition of genomic Ty1 elements 18- to 56-fold but has little effect on the transposition of related Ty2 elements. rtt100-1 was shown to be a null allele of the FUS3 gene, which encodes a haploid-specific mitogen-activated protein kinase. In fus3 mutants, the levels of Ty1 RNA, protein synthesis, and proteolytic processing were not altered relative to those in FUS3 strains but steady-state levels of TyA, integrase, and reverse transcriptase proteins and Ty1 cDNA were all increased. These findings suggest that Fus3 suppresses Ty1 transposition by destabilizing viruslike particle-associated proteins. The Fus3 kinase is activated through the mating-pheromone response pathway by phosphorylation at basal levels in naive cells and at enhanced levels in pheromone-treated cells. We demonstrate that suppression of Ty1 transposition in naive cells requires basal levels of Fus3 activation. Substitution of conserved amino acids required for activation of Fus3 derepressed Ty1 transposition. Moreover, epistasis analyses revealed that components of the pheromone response pathway that act upstream of Fus3, including Ste4, Ste5, Ste7, and Ste11, are required for the posttranslational suppression of Ty1 transposition by Fus3. The regulation of Ty1 transposition by Fus3 provides a haploid-specific mechanism through which environmental signals can modulate the levels of retrotransposition.
Collapse
Affiliation(s)
- D Conte
- Molecular Genetics Program, Wadsworth Center & School of Public Health, State University of New York at Albany, 12201-2002, USA
| | | | | | | | | |
Collapse
|
425
|
Yun DJ, Ibeas JI, Lee H, Coca MA, Narasimhan ML, Uesono Y, Hasegawa PM, Pardo JM, Bressan RA. Osmotin, a plant antifungal protein, subverts signal transduction to enhance fungal cell susceptibility. Mol Cell 1998; 1:807-17. [PMID: 9660964 DOI: 10.1016/s1097-2765(00)80080-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The plant pathogenesis-related protein osmotin is an antifungal cytotoxic agent that causes rapid cell death in the yeast S. cerevisiae. We show here that osmotin uses a signal transduction pathway to weaken defensive cell wall barriers and increase its cytotoxic efficacy. The pathway activated by osmotin includes the regulatory elements of the mating pheromone response STE4, STE18, STE20, STE5, STE11, STE7, FUS3, KSS1, and STE12. Neither the pheromone receptor nor its associated G protein alpha subunit GPA1 are required for osmotin action. However, mutation of SST2, a negative regulator of G alpha proteins, resulted in supersensitivity to osmotin. Phosphorylation of STE7 was rapidly stimulated by osmotin preceding any changes in cell vitality or morphology. These results demonstrate that osmotin subverts target cell signal transduction as part of its mechanism of action.
Collapse
Affiliation(s)
- D J Yun
- Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University Chinju, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
426
|
Kothe GO, Free SJ. The isolation and characterization of nrc-1 and nrc-2, two genes encoding protein kinases that control growth and development in Neurospora crassa. Genetics 1998; 149:117-30. [PMID: 9584090 PMCID: PMC1460147 DOI: 10.1093/genetics/149.1.117] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Using an insertional mutagenesis approach, a series of Neurospora crassa mutants affected in the ability to control entry into the conidiation developmental program were isolated. One such mutant, GTH16-T4, was found to lack normal vegetative hyphae and to undergo constitutive conidiation. The affected gene has been named nrc-1, for nonrepressible conidiation gene #1. The nrc-1 gene was cloned from the mutant genomic DNA by plasmid rescue, and was found to encode a protein closely related to the protein products of the Saccharomyces cerevisiae STE11 and Schizosaccharomyces pombe byr2 genes. Both of these genes encode MAPKK kinases that are necessary for sexual development in these organisms. We conclude the nrc-1 gene encodes a MAPKK kinase that functions to repress the onset of conidiation in N. crassa. A second mutant, GTH16-T17, was found to lack normal vegetative hyphae and to constitutively enter, but not complete, the conidiation program. The affected locus is referred to as nrc-2 (nonrepressible conidiation gene #2). The nrc-2 gene was cloned and found to encode a serine-threonine protein kinase. The kinase is closely related to the predicted protein products of the S. pombe kad5, and the S. cerevisiae YNRO47w and KIN82 genes, three genes that have been identified in genome sequencing projects. The N. crassa nrc-2 gene is the first member of this group of kinases for which a phenotype has been defined. We conclude a functional nrc-2-encoded serine/threonine kinase is required to repress entry into the conidiation program.
Collapse
Affiliation(s)
- G O Kothe
- Department of Biological Sciences, State University of New York, Buffalo, New York 14260-1300, USA
| | | |
Collapse
|
427
|
Affiliation(s)
- T S Lewis
- Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder 80309, USA
| | | | | |
Collapse
|
428
|
Pelech SL, Charest DL. MAP kinase-dependent pathways in cell cycle control. PROGRESS IN CELL CYCLE RESEARCH 1998; 1:33-52. [PMID: 9552352 DOI: 10.1007/978-1-4615-1809-9_4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mitogen-activated protein kinases such as Erk1 and Erk2 serve as a paradigm for a growing family of proline-directed protein kinases that mediate entry, progression and exit from the cell cycle in diverse eukaryotic cells. These enzymes function within highly conserved modules of sequentially activating protein kinases that transduce signals from diverse extracellular stimuli. In vertebrates, at least three distinct kinases modules have been characterized. Mitogens induce the sequential activation of the kinases Raf1-->Mek1-->Erk2-->Rsk via the G-protein Ras. Stress factors stimulate c-Jun activation through a related kinase pathway involving Mekk-->Sek-->SAPK c-Jun, and hsp27 phosphorylation via the MKK3-->Hog-->MAPKAPK-2 hsp27 route. Genetic and biochemical studies, for example from budding yeast, imply the existence of several related protein kinase modules that can operate in parallel or within integrated systems.
Collapse
Affiliation(s)
- S L Pelech
- Biomedical Research Centre, University of British Columbia, Vancouver, Canada
| | | |
Collapse
|
429
|
Nakazawa T, Horiuchi H, Ohta A, Takagi M. Isolation and characterization of EPD1, an essential gene for pseudohyphal growth of a dimorphic yeast, Candida maltosa. J Bacteriol 1998; 180:2079-86. [PMID: 9555889 PMCID: PMC107133 DOI: 10.1128/jb.180.8.2079-2086.1998] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Additional copies of the centromeric DNA (CEN) region induce pseudohyphal growth in a dimorphic yeast, Candida maltosa (T. Nakazawa, T. Motoyama, H. Horiuchi, A. Ohta, and M. Takagi, J. Bacteriol. 179:5030-5036, 1997). To understand the mechanism of this transition, we screened the gene library of C. maltosa for sequences which could suppress this morphological change. As a result, we isolated the 5' end of a new gene, EPD1 (for essential for pseudohyphal development), and then cloned the entire gene. The predicted amino acid sequence of Epdlp was highly homologous to those of Ggp1/Gas1/Cwh52p, a glycosylphosphatidylinositol-anchored protein of Saccharomyces cerevisiae, and Phr1p and Phr2p of Candida albicans. The expression of EPD1 was moderately regulated by environmental pH. A homozygous EPD1 null mutant showed some morphological defects and reduction in growth rate and reduced levels of both alkali-soluble and alkali-insoluble beta-glucans. Moreover, the mutant could not undergo the transition from yeast form to pseudohyphal form induced by additional copies of the CEN sequence at pH 4 or by n-hexadecane at pH 4 or pH 7, suggesting that EPD1 is not essential for yeast form growth but is essential for transition to the pseudohyphal form. Overexpression of the amino-terminal part of Epd1p under the control of the GAL promoter suppressed the pseudohyphal development induced by additional copies of the CEN sequence, whereas overexpression of the full-length EPD1 did not. This result and the initial isolation of the 5' end of EPD1 as a suppressor of the pseudohyphal growth induced by the CEN sequence suggest that the amino-terminal part of Epd1p may have a dominant-negative effect on the functions of Epd1p in the pseudohyphal growth induced by the CEN sequence.
Collapse
Affiliation(s)
- T Nakazawa
- Department of Biotechnology, The University of Tokyo, Japan
| | | | | | | |
Collapse
|
430
|
Lee BS, Lichtenstein CP, Faiola B, Rinckel LA, Wysock W, Curcio MJ, Garfinkel DJ. Posttranslational inhibition of Ty1 retrotransposition by nucleotide excision repair/transcription factor TFIIH subunits Ssl2p and Rad3p. Genetics 1998; 148:1743-61. [PMID: 9560391 PMCID: PMC1460110 DOI: 10.1093/genetics/148.4.1743] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
rtt4-1 (regulator of Ty transposition) is a cellular mutation that permits a high level of spontaneous Ty1 retrotransposition in Saccharomyces cerevisiae. The RTT4 gene is allelic with SSL2 (RAD25), which encodes a DNA helicase present in basal transcription (TFIIH) and nucleotide excision repair (NER) complexes. The ssl2-rtt (rtt4-1) mutation stimulates Ty1 retrotransposition, but does not alter Ty1 target site preferences, or increase cDNA or mitotic recombination. In addition to ssl2-rtt, the ssl2-dead and SSL2-1 mutations stimulate Ty1 transposition without altering the level of Ty1 RNA or proteins. However, the level of Ty1 cDNA markedly increases in the ssl2 mutants. Like SSL2, certain mutations in another NER/TFIIH DNA helicase encoded by RAD3 stimulate Ty1 transposition. Although Ssl2p and Rad3p are required for NER, inhibition of Ty1 transposition is independent of Ssl2p and Rad3p NER functions. Our work suggests that NER/TFIIH subunits antagonize Ty1 transposition posttranslationally by inhibiting reverse transcription or destabilizing Ty1 cDNA.
Collapse
Affiliation(s)
- B S Lee
- Gene Regulation and Chromosome Biology Laboratory, Advanced BioScience Laboratories-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA
| | | | | | | | | | | | | |
Collapse
|
431
|
Abstract
Budding yeast contain at least four distinct MAPK (mitogen activated protein kinase) cascades that transduce a variety of intracellular signals: mating-pheromone response, pseudohyphal/invasive growth, cell wall integrity, and high osmolarity adaptation. Although each MAPK cascade contains a conserved set of three protein kinases, the upstream activation mechanisms for these cascades are diverse, including a trimeric G protein, monomeric small G proteins, and a prokaryotic-like two-component system. Recently, it became apparent that there is extensive sharing of signaling elements among the MAPK pathways; however, little undesirable cross-talk occurs between various cascades. The formation of multi-protein signaling complexes is probably centrally important for this insulation of individual MAPK cascades.
Collapse
Affiliation(s)
- F Posas
- Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street,Boston, MA 02115, USA
| | | | | |
Collapse
|
432
|
Bauman P, Cheng QC, Albright CF. The Byr2 kinase translocates to the plasma membrane in a Ras1-dependent manner. Biochem Biophys Res Commun 1998; 244:468-74. [PMID: 9514947 DOI: 10.1006/bbrc.1998.8292] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The activation of mitogen-activated protein kinase cascades by the Ras GTPase is an evolutionarily conserved signal transduction mechanism. To better understand the interaction between Ras and its target kinase, we study the yeast Schizosaccharomyces pombe where the Ras1 GTPase activates the Byr2 kinase. Cell fractionation and immunofluorescence showed that Ras1 was localized to the plasma membrane and that Byr2 was in the cytoplasm. When Ras1 was overexpressed, Byr2 was translocated to the plasma membrane. Byr2 translocation was dependent on binding to Ras1 since Ras1-V12, an activated mutant of Ras1, caused more Byr2 translocation than Ras1, since Ras1-D38E, an effector domain mutant, did not cause Byr2 translocation, and since the Ras1-binding domain of Byr2 was necessary and sufficient to cause Byr2 translocation. The Byr2 protein was usually not uniform around the plasma membrane, but was frequently enriched at the cell ends and at the region of septal deposition. This uneven membrane localization depended upon regions of the Byr2 regulatory domain, in addition to those required for Ras1 binding, suggesting that these Byr2 domains participate in protein-protein interactions.
Collapse
Affiliation(s)
- P Bauman
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
| | | | | |
Collapse
|
433
|
Roemer T, Vallier L, Sheu YJ, Snyder M. The Spa2-related protein, Sph1p, is important for polarized growth in yeast. J Cell Sci 1998; 111 ( Pt 4):479-94. [PMID: 9443897 DOI: 10.1242/jcs.111.4.479] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae protein Sph1p is both structurally and functionally related to the polarity protein, Spa2p. Sph1p and Spa2p are predicted to share three 100-amino acid domains each exceeding 30% sequence identity, and the amino-terminal domain of each protein contains a direct repeat common to Homo sapiens and Caenorhabditis elegans protein sequences. sph1- and spa2-deleted cells possess defects in mating projection morphology and pseudohyphal growth. sph1(Delta) spa2(Delta) double mutants also exhibit a strong haploid invasive growth defect and an exacerbated mating projection defect relative to either sph1(Delta) or spa2(Delta) single mutants. Consistent with a role in polarized growth, Sph1p localizes to growth sites in a cell cycle-dependent manner: Sph1p concentrates as a cortical patch at the presumptive bud site in unbudded cells, at the tip of small, medium and large buds, and at the bud neck prior to cytokinesis. In pheromone-treated cells, Sph1p localizes to the tip of the mating projection. Proper localization of Sph1p to sites of active growth during budding and mating requires Spa2p. Sph1p interacts in the two-hybrid system with three mitogen-activated protein (MAP) kinase kinases (MAPKKs): Mkk1p and Mkk2p, which function in the cell wall integrity/cell polarization MAP kinase pathway, and Ste7p, which operates in the pheromone and pseudohyphal signaling response pathways. Sph1p also interacts weakly with STE11, the MAPKKK known to activate STE7. Moreover, two-hybrid interactions between SPH1 and STE7 and STE11 occur independently of STE5, a proposed scaffolding protein which interacts with several members of this MAP kinase module. We speculate that Spa2p and Sph1p may function during pseudohyphal and haploid invasive growth to help tether this MAP kinase module to sites of polarized growth. Our results indicate that Spa2p and Sph1p comprise two related proteins important for the control of cell morphogenesis in yeast.
Collapse
Affiliation(s)
- T Roemer
- Department of Biology, Yale University, New Haven, CT 06520-8103, USA
| | | | | | | |
Collapse
|
434
|
Erdman S, Lin L, Malczynski M, Snyder M. Pheromone-regulated genes required for yeast mating differentiation. J Cell Biol 1998; 140:461-83. [PMID: 9456310 PMCID: PMC2140177 DOI: 10.1083/jcb.140.3.461] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/1997] [Revised: 11/14/1997] [Indexed: 02/06/2023] Open
Abstract
Yeast cells mate by an inducible pathway that involves agglutination, mating projection formation, cell fusion, and nuclear fusion. To obtain insight into the mating differentiation of Saccharomyces cerevisiae, we carried out a large-scale transposon tagging screen to identify genes whose expression is regulated by mating pheromone. 91,200 transformants containing random lacZ insertions were screened for beta-galactosidase (beta-gal) expression in the presence and absence of alpha factor, and 189 strains containing pheromone-regulated lacZ insertions were identified. Transposon insertion alleles corresponding to 20 genes that are novel or had not previously been known to be pheromone regulated were examined for effects on the mating process. Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects. Three of the proteins encoded by these genes, Fig1p, Fig2p, and Fig4p, are dispensible for cell polarization in uniform concentrations of mating pheromone, but are required for normal cell polarization in mating mixtures, conditions that involve cell-cell communication. Fig1p and Fig2p are also important for cell fusion and conjugation bridge shape, respectively. The fourth protein, Kar5p/Fig3p, is required for nuclear fusion. Fig1p and Fig2p are likely to act at the cell surface as Fig1:: beta-gal and Fig2::beta-gal fusion proteins localize to the periphery of mating cells. Fig4p is a member of a family of eukaryotic proteins that contain a domain homologous to the yeast Sac1p. Our results indicate that a variety of novel genes are expressed specifically during mating differentiation to mediate proper cell morphogenesis, cell fusion, and other steps of the mating process.
Collapse
Affiliation(s)
- S Erdman
- Department of Biology, Yale University, New Haven, Connecticut 06520-8103, USA
| | | | | | | |
Collapse
|
435
|
Vivier MA, Lambrechts MG, Pretorius IS. Coregulation of starch degradation and dimorphism in the yeast Saccharomyces cerevisiae. Crit Rev Biochem Mol Biol 1998; 32:405-35. [PMID: 9383611 DOI: 10.3109/10409239709082675] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Saccharomyces cerevisiae, the exemplar unicellular eukaryote, can only survive and proliferate in its natural habitats through constant adaptation within the constraints of a dynamic ecosystem. In every cell cycle of S. cerevisiae, there is a short period in the G1 phase of the cell cycle where "sensing" transpires; if a sufficient amount of fermentable sugars is available, the cells will initiate another round of vegetative cell division. When fermentable sugars become limiting, the yeast can execute the diauxic shift, where it reprograms its metabolism to utilize nonfermentable carbon sources. S. cerevisiae can also initiate the developmental program of pseudohyphal formation and invasive growth response, when essential nutrients become limiting. S. cerevisiae shares this growth form-switching ability with important pathogens such as the human pathogen, Candida albicans, and the corn smut pathogen Ustilago maydis. The pseudohyphal growth response of S. cerevisiae has mainly been implicated as a means for the yeast to search for nutrients. An important observation made was that starch-degrading S. cerevisiae strains have the added ability to form pseudohyphae and grow invasively into a starch-containing medium. More significantly, it was also shown that the STA1-3 genes encoding three glucoamylase isozymes responsible for starch hydrolysis in S. cerevisiae are coregulated with a gene, MUC1, essential for pseudohyphal and invasive growth. At least two putative transcriptional activators, Mss10p and Mss11p, are involved in this regulation. The Muc1p is a putative integral membrane-bound protein similar to mammalian mucin-like proteins that have been implicated in the ability of cancer cells to invade other tissues. This provided us with an excellent example of integrative control between nutrient sensing, signaling, and differential development.
Collapse
Affiliation(s)
- M A Vivier
- Institute for Wine Biotechnology, University of Stellenbosch, South Africa
| | | | | |
Collapse
|
436
|
Navarro-García F, Alonso-Monge R, Rico H, Pla J, Sentandreu R, Nombela C. A role for the MAP kinase gene MKC1 in cell wall construction and morphological transitions in Candida albicans. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 2):411-424. [PMID: 9493378 DOI: 10.1099/00221287-144-2-411] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Candida albicans MKC1 gene encodes a mitogen-activated protein (MAP) kinase, which has been cloned by complementation of the lytic phenotype associated with Saccharomyces cerevisiae slt2 (mpk1) mutants. In this work, the physiological role of this MAP kinase in the pathogenic fungus C. albicans was characterized and a role for MKC1 in the biogenesis of the cell wall suggested based on the following criteria. First, C. albicans mkc1 delta/mkc1 delta strains displayed alterations in their cell surfaces under specific conditions as evidenced by scanning electron microscopy. Second, an increase in specific cell wall epitopes (O-glycosylated mannoprotein) was shown by confocal microscopy in mkc1 delta/mkc1 delta mutants. Third, the sensitivity to antifungals which inhibit (1,3)-beta-glucan and chitin synthesis was increased in these mutants. In addition, evidence for a role for the MKC1 gene in morphological transitions in C. albicans is presented based on the impairment of pseudohyphal formation of mkc1 delta/mkc1 delta strains on Spider medium and on the effect of its overexpression on Sacch. cerevisiae colony morphology on SLADH medium. Using the two-hybrid system, it was also demonstrated that MKC1 is able to interact specifically with Sacch. cerevisiae Mkk1p and Mkk2p, the MAP-kinase kinases of the PKC1-mediated route of Sacch. cerevisiae, and to activate transcription in Sacch. cerevisiae when bound to a DNA-binding element. These results suggest a role for this MAP kinase in the construction of the cell wall of C. albicans and indicate its potential relevance for the development of novel antifungals.
Collapse
MESH Headings
- Antifungal Agents/pharmacology
- Calcium-Calmodulin-Dependent Protein Kinases/genetics
- Calcium-Calmodulin-Dependent Protein Kinases/metabolism
- Calcium-Calmodulin-Dependent Protein Kinases/physiology
- Candida albicans/enzymology
- Candida albicans/genetics
- Candida albicans/ultrastructure
- Cell Wall/enzymology
- Cell Wall/metabolism
- Cell Wall/ultrastructure
- Chitin/metabolism
- DNA, Fungal/genetics
- Flow Cytometry
- Fluorescent Antibody Technique, Indirect
- Fungal Proteins/metabolism
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Fungal
- Glucans/metabolism
- MAP Kinase Kinase 1
- MAP Kinase Kinase 2
- Membrane Glycoproteins/metabolism
- Microscopy, Confocal
- Microscopy, Electron
- Microscopy, Electron, Scanning
- Mitogen-Activated Protein Kinase Kinases
- Mitogen-Activated Protein Kinases
- Plasmids
- Protein Kinase C
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Protein-Tyrosine Kinases/genetics
- Protein-Tyrosine Kinases/metabolism
- Recombination, Genetic
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Transcription, Genetic
- beta-Galactosidase/metabolism
Collapse
Affiliation(s)
- Federico Navarro-García
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
| | - Rebeca Alonso-Monge
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
| | - Hortensia Rico
- Sección Departamental de Microbiología, Facultad de Farmàcia, Universidad de València, Avinguda Vicent Andrés Estellés, E-46100 Burjassot, València, Spain
| | - Jesús Pla
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
| | - Rafael Sentandreu
- Sección Departamental de Microbiología, Facultad de Farmàcia, Universidad de València, Avinguda Vicent Andrés Estellés, E-46100 Burjassot, València, Spain
| | - César Nombela
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
| |
Collapse
|
437
|
Raymond M, Dignard D, Alarco AM, Mainville N, Magee BB, Thomas DY. A Ste6p/P-glycoprotein homologue from the asexual yeast Candida albicans transports the a-factor mating pheromone in Saccharomyces cerevisiae. Mol Microbiol 1998; 27:587-98. [PMID: 9489670 DOI: 10.1046/j.1365-2958.1998.00704.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In Saccharomyces cerevisiae MATa cells, export of the a-factor mating pheromone is mediated by Ste6p, a member of the ATP-binding cassette (ABC) superfamily of transporters and a close homologue of mammalian multidrug transporter P-glycoproteins (Pgps). We have used functional complementation of a ste6delta mutation to isolate a gene encoding an ABC transporter capable of a-factor export from the pathogenic yeast, Candida albicans. This gene codes for a 1323-amino acid protein with an intramolecular duplicated structure, each repeated half containing six potential hydrophobic transmembrane segments and a hydrophilic domain with consensus sequences for an ATP-binding fold. The predicted protein displays significant sequence similarity to S. cerevisiae Ste6p and mammalian Pgps. The gene has been named HST6, for homologue of STE6. A high degree of structural conservation between the STE6 and the HST6 loci with respect to DNA sequence, physical linkage and transcriptional arrangement indicates that HST6 is the C. albicans orthologue of the S. cerevisiae STE6 gene. We show that the HST6 gene is transcribed in a haploid-specific manner in S. cerevisiae, consistent with the presence in its promoter of a consensus sequence for Mata1p-Matalpha2p binding known to mediate the repression of haploid-specific genes in S. cerevisiae diploid cells. In C. albicans, HST6 is expressed constitutively at high levels in the different cell types analysed (yeast, hyphae, white and opaque), demonstrating that HST6 transcription is not repressed in this diploid yeast, unlike in diploid S. cerevisiae, and suggesting a basic biological function for the Hst6p transporter in C. albicans. The strong similarity between Hst6p and the multidrug transporter Pgps also raises the possibility that Hst6p could be involved in resistance to antifungal drugs in C. albicans.
Collapse
Affiliation(s)
- M Raymond
- Institut de recherches cliniques de Montréal, Québec, Canada.
| | | | | | | | | | | |
Collapse
|
438
|
Lo WS, Dranginis AM. The cell surface flocculin Flo11 is required for pseudohyphae formation and invasion by Saccharomyces cerevisiae. Mol Biol Cell 1998; 9:161-71. [PMID: 9436998 PMCID: PMC25236 DOI: 10.1091/mbc.9.1.161] [Citation(s) in RCA: 294] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Diploid yeast develop pseudohyphae in response to nitrogen starvation, while haploid yeast produce invasive filaments which penetrate the agar in rich medium. We have identified a gene, FLO11, that encodes a cell wall protein which is critically required for both invasion and pseudohyphae formation in response to nitrogen starvation. FLO11 encodes a cell surface flocculin with a structure similar to the class of yeast serine/threonine-rich GPI-anchored cell wall proteins. Cells of the Saccharomyces cerevisiae strain Sigma1278b with deletions of FLO11 do not form pseudohyphae as diploids nor invade agar as haploids. In rich media, FLO11 is regulated by mating type; it is expressed in haploid cells but not in diploids. Upon transfer to nitrogen starvation media, however, FLO11 transcripts accumulate in diploid cells, but not in haploids. Overexpression of FLO11 in diploid cells, which are otherwise not invasive, enables them to invade agar. Thus, the mating type repression of FLO11 in diploids grown in rich media suffices to explain the inability of these cells to invade. The promoter of FLO11 contains a consensus binding sequence for Ste12p and Tec1p, proteins known to cooperatively activate transcription of Ty1 elements and the TEC1 gene during development of pseudohyphae. Yeast with a deletion of STE12 does not express FLO11 transcripts, indicating that STE12 is required for FLO11 expression. These ste12-deletion strains also do not invade agar. However, the ability to invade can be restored by overexpressing FLO11. Activation of FLO11 may thus be the primary means by which Ste12p and Tec1p cause invasive growth.
Collapse
Affiliation(s)
- W S Lo
- Department of Biological Sciences, St. John's University, Jamaica, New York 11439, USA
| | | |
Collapse
|
439
|
Csank C, Makris C, Meloche S, Schröppel K, Röllinghoff M, Dignard D, Thomas DY, Whiteway M. Derepressed hyphal growth and reduced virulence in a VH1 family-related protein phosphatase mutant of the human pathogen Candida albicans. Mol Biol Cell 1997; 8:2539-51. [PMID: 9398674 PMCID: PMC25726 DOI: 10.1091/mbc.8.12.2539] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/1997] [Accepted: 09/08/1997] [Indexed: 02/05/2023] Open
Abstract
Mitogen-activated protein (MAP) kinases are pivotal components of eukaryotic signaling cascades. Phosphorylation of tyrosine and threonine residues activates MAP kinases, but either dual-specificity or monospecificity phosphatases can inactivate them. The Candida albicans CPP1 gene, a structural member of the VH1 family of dual- specificity phosphatases, was previously cloned by its ability to block the pheromone response MAP kinase cascade in Saccharomyces cerevisiae. Cpp1p inactivated mammalian MAP kinases in vitro and acted as a tyrosine-specific enzyme. In C. albicans a MAP kinase cascade can trigger the transition from the budding yeast form to a more invasive filamentous form. Disruption of the CPP1 gene in C. albicans derepressed the yeast to hyphal transition at ambient temperatures, on solid surfaces. A hyphal growth rate defect under physiological conditions in vitro was also observed and could explain a reduction in virulence associated with reduced fungal burden in the kidneys seen in a systemic mouse model. A hyper-hyphal pathway may thus have some detrimental effects on C. albicans cells. Disruption of the MAP kinase homologue CEK1 suppressed the morphological effects of the CPP1 disruption in C. albicans. The results presented here demonstrate the biological importance of a tyrosine phosphatase in cell-fate decisions and virulence in C. albicans.
Collapse
Affiliation(s)
- C Csank
- Centre de Recherche, Hôtel-Dieu de Montréal and Department of Pharmacology, University of Montreal, Montreal, Quebec, Canada H2W 1T8
| | | | | | | | | | | | | | | |
Collapse
|
440
|
Madhani HD, Styles CA, Fink GR. MAP kinases with distinct inhibitory functions impart signaling specificity during yeast differentiation. Cell 1997; 91:673-84. [PMID: 9393860 DOI: 10.1016/s0092-8674(00)80454-7] [Citation(s) in RCA: 340] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Filamentous invasive growth of S. cerevisiae requires multiple elements of the mitogen-activated protein kinase (MAPK) signaling cascade that are also components of the mating pheromone response pathway. Here we show that, despite sharing several constituents, the two pathways use different MAP kinases. The Fus3 MAPK regulates mating, whereas the Kss1 MAPK regulates filamentation and invasion. Remarkably, in addition to their kinase-dependent activation functions, Kss1 and Fus3 each have a distinct kinase-independent inhibitory function. Kss1 inhibits the filamentation pathway by interacting with its target transcription factor Ste12. Fus3 has a different inhibitory activity that prevents the inappropriate activation of invasion by the pheromone response pathway. In the absence of Fus3, there is erroneous crosstalk in which mating pheromone now activates filamentation-specific gene expression using the Kss1 MAPK.
Collapse
Affiliation(s)
- H D Madhani
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
| | | | | |
Collapse
|
441
|
Cook JG, Bardwell L, Thorner J. Inhibitory and activating functions for MAPK Kss1 in the S. cerevisiae filamentous-growth signalling pathway. Nature 1997; 390:85-8. [PMID: 9363895 DOI: 10.1038/36355] [Citation(s) in RCA: 210] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Mitogen-activated protein kinase (MAPK) cascades are conserved signalling modules that regulate responses to diverse extracellular stimuli, developmental cues and environmental stresses. A MAPK is phosphorylated and activated by a MAPK kinase (MAPKK), which is activated by an upstream protein kinase, such as Raf, Mos or a MAPKK kinase. Ste7, a MAPKK in the yeast Saccharomyces cerevisiae, is required for two developmental pathways: mating and invasive (filamentous) growth. Kss1 and Fus3, the MAPK targets of Ste7, are required for mating, but their role in invasive growth has been unclear. Because no other S. cerevisiae MAPK has been shown to function in invasive growth, it was proposed that Ste7 may have non-MAPK targets. We show instead that Kss1 is the principal target of Ste7 in the invasive-growth response in both haploids and diploids. We demonstrate further that Kss1 in its inactive form is a potent negative regulator of invasive growth. Ste7 acts to relieve this negative regulation by switching Kss1 from an inhibitor to an activator. These results indicate that this MAPK has a physiologically important function in its unactivated state. Comparison of normal and MAPK-deficient cells indicates that nitrogen starvation and activated Ras stimulate filamentous growth through both MAPK-independent and MAPK-dependent means.
Collapse
Affiliation(s)
- J G Cook
- Department of Molecular and Cell Biology, University of California, Berkeley 94720-3202, USA
| | | | | |
Collapse
|
442
|
Abstract
The recent discovery that some laboratory strains of Saccharomyces cerevisiae are capable of limited filamentous growth has stimulated genetic analysis of dimorphism in this microorganism. The puzzle of why most strains are nonfilamentous is now resolved. Remarkably, a single point mutation with broad consequences separates these domesticated yeast from their wild ancestors.
Collapse
Affiliation(s)
- S J Kron
- Center for Molecular Oncology, University of Chicago, Chicago, IL 60637, USA.
| |
Collapse
|
443
|
Anafi M, Kiefer F, Gish GD, Mbamalu G, Iscove NN, Pawson T. SH2/SH3 adaptor proteins can link tyrosine kinases to a Ste20-related protein kinase, HPK1. J Biol Chem 1997; 272:27804-11. [PMID: 9346925 DOI: 10.1074/jbc.272.44.27804] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ste20-related protein kinases have been implicated as regulating a range of cellular responses, including stress-activated protein kinase pathways and the control of cytoskeletal architecture. An important issue involves the identities of the upstream signals and regulators that might control the biological functions of mammalian Ste20-related protein kinases. HPK1 is a protein-serine/threonine kinase that possesses a Ste20-like kinase domain, and in transfected cells activates a protein kinase pathway leading to the stress-activated protein kinase SAPK/JNK. Here we have investigated candidate upstream regulators that might interact with HPK1. HPK1 possesses an N-terminal catalytic domain and an extended C-terminal tail with four proline-rich motifs. The SH3 domains of Grb2 bound in vitro to specific proline-rich motifs in the HPK1 tail and functioned synergistically to direct the stable binding of Grb2 to HPK1 in transfected Cos1 cells. Epidermal growth factor (EGF) stimulation did not affect the binding of Grb2 to HPK1 but induced recruitment of the Grb2.HPK1 complex to the autophosphorylated EGF receptor and to the Shc docking protein. Several activated receptor and cytoplasmic tyrosine kinases, including the EGF receptor, stimulated the tyrosine phosphorylation of the HPK1 serine/threonine kinase. These results suggest that HPK1, a mammalian Ste20-related protein-serine/threonine kinase, can potentially associate with protein-tyrosine kinases through interactions mediated by SH2/SH3 adaptors such as Grb2. Such interaction may provide a possible mechanism for cross-talk between distinct biochemical pathways following the activation of tyrosine kinases.
Collapse
Affiliation(s)
- M Anafi
- Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
| | | | | | | | | | | |
Collapse
|
444
|
Abstract
A summary of previously defined phenotypes in the yeast Saccharomyces cerevisiae is presented. The purpose of this review is to provide a compendium of phenotypes that can be readily screened to identify pleiotropic phenotypes associated with primary or suppressor mutations. Many of these phenotypes provide a convenient alternative to the primary phenotype for following a gene, or as a marker for cloning a gene by genetic complementation. In many cases a particular phenotype or set of phenotypes can suggest a function for the product of the mutated gene.
Collapse
Affiliation(s)
- M Hampsey
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854, USA
| |
Collapse
|
445
|
Leberer E, Ziegelbauer K, Schmidt A, Harcus D, Dignard D, Ash J, Johnson L, Thomas DY. Virulence and hyphal formation of Candida albicans require the Ste20p-like protein kinase CaCla4p. Curr Biol 1997; 7:539-46. [PMID: 9259554 DOI: 10.1016/s0960-9822(06)00252-1] [Citation(s) in RCA: 165] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND The pathogenic fungus Candida albicans is capable of a morphological transition from a unicellular budding yeast to a filamentous form. Extensive filamentous growth leads to the formation of mycelia displaying hyphae with branches and lateral buds. Hyphae have been observed to adhere to and invade host tissues more readily than the yeast form, suggesting that filamentous growth may contribute to the virulence of this major human pathogen. A molecular and genetic understanding of the potential role of morphological switching in the pathogenicity of C. albicans would be of significant benefit in view of the increasing incidence of candidiasis. RESULTS The CaCLA4 gene of C. albicans was cloned by functional complementation of the growth defect of cells of the budding yeast Saccharomyces cerevisiae deleted for the STE20 gene and the CLA4 gene. CaCLA4 encodes a member of the Ste20p family of serine/threonine protein kinases and is characterized by a pleckstrin homology domain and a Cdc42p-binding domain in its amino-terminal non-catalytic region. Deletion of both alleles of CaCLA4 in C. albicans caused defects in hyphal formation in vitro, in both synthetic liquid and solid media, and in vivo in a mouse model for systemic candidiasis. The gene deletions reduced colonization of the kidneys in infected mice and suppressed C. albicans virulence in the mouse model. CONCLUSIONS Our results demonstrate that the function of the CaCla4p protein kinase is essential for virulence and morphological switching of C. albicans in a mouse model. Thus, hyphal formation of C. albicans mediated by CaCla4p may contribute to the pathogenicity of this dimorphic fungus, suggesting that regulators of morphological switching may be useful targets for antifungal drugs.
Collapse
Affiliation(s)
- E Leberer
- Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec, Canada.
| | | | | | | | | | | | | | | |
Collapse
|
446
|
Nakazawa T, Motoyama T, Horiuchi H, Ohta A, Takagi M. Evidence that part of a centromeric DNA region induces pseudohyphal growth in a dimorphic yeast, Candida maltosa. J Bacteriol 1997; 179:5030-6. [PMID: 9260943 PMCID: PMC179359 DOI: 10.1128/jb.179.16.5030-5036.1997] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We observed that a YCp-type vector having the centromeric DNA (CEN) sequence previously isolated from the genome, but not a YRp-type vector lacking the CEN sequence, induced pseudohyphal growth in a dimorphic fungi, Candida maltosa, which had been shown to be closely related to Candida albicans by phylogenetic analysis. Deletion analysis of the CEN sequence revealed that the intact CEN sequence was not required for the induction, but part of it, having partial centromeric activity, was enough for the induction. By screening the gene library of this yeast for the sequences which induced pseudohyphal growth, we isolated three different DNA fragments which also had part of the centromere-like sequence. Partial centromeric activity of these fragments was confirmed by three criteria: low copy number and high stability of the plasmids carrying these fragments and rearrangement at high frequency of the plasmid DNA with one of these fragments plus the CEN sequence. Furthermore, when the GGTAGCG sequence commonly found in one copy in each of these four sequences was mutated in the CEN sequence by site-directed mutagenesis, both partial centromeric activity and pseudohyphal growth-inducing activity of the CEN sequence were lost. These results indicated that part of CEN region with partial centromeric activity induces pseudohyphal growth in C. maltosa. It is suggested that some cellular components which interact with the sequence containing GGTAGCG required for centromeric activity are involved in the regulation of the transition between yeast forms and pseudohyphal forms of the cells.
Collapse
Affiliation(s)
- T Nakazawa
- Department of Biotechnology, The University of Tokyo, Bunkyo-ku, Japan
| | | | | | | | | |
Collapse
|
447
|
Baur M, Esch RK, Errede B. Cooperative binding interactions required for function of the Ty1 sterile responsive element. Mol Cell Biol 1997; 17:4330-7. [PMID: 9234690 PMCID: PMC232286 DOI: 10.1128/mcb.17.8.4330] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Ste12p transcription factor controls the expression of Ty1 transposable element insertion mutations and genes whose products are required for mating in Saccharomyces cerevisiae. The binding site for Ste12p is a consensus DNA sequence known as a pheromone response element (PRE). Upstream activating sequences (UASs) derived from known Ste12p-dependent genes have previously been characterized to require either multiple PREs or a single PRE coupled to a binding site for a second protein. The Ste12p-dependent UAS from Ty1, called a sterile response element (SRE), is of the second type and is comprised of a PRE and an adjacent TEA (TEF-1, Tec1, and AbaA motif) DNA consensus sequence (TCS). In this report, we show by UV cross-linking analysis that two proteins, Ste12p and a protein with an apparent size of 72 kDa, directly contact the Ty1 SRE. Other experiments show that Tec1p is required for formation of the Ty1 SRE protein-DNA complex and is physically present in the complex. These results establish a direct role for Tec1p in the Ty1 SRE and yet another set of combinatorial interactions that achieve a qualitatively distinct mode of transcriptional regulation with Ste12p.
Collapse
Affiliation(s)
- M Baur
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260, USA
| | | | | |
Collapse
|
448
|
Braun BR, Johnson AD. Control of filament formation in Candida albicans by the transcriptional repressor TUP1. Science 1997; 277:105-9. [PMID: 9204892 DOI: 10.1126/science.277.5322.105] [Citation(s) in RCA: 421] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The pathogenic yeast Candida albicans regulates its cellular morphology in response to environmental conditions. Ellipsoidal, single cells (blastospores) predominate in rich media, whereas filaments composed of elongated cells that are attached end-to-end form in response to starvation, serum, and other conditions. The TUP1 gene, which encodes a general transcriptional repressor in Saccharomyces cerevisiae, was isolated from C. albicans and disrupted. The resulting tup1 mutant strain of C. albicans grew exclusively as filaments under all conditions tested. TUP1 was epistatic to the transcriptional activator CPH1, previously found to promote filamentous growth. The results suggest a model where TUP1 represses genes responsible for initiating filamentous growth and this repression is lifted under inducing environmental conditions.
Collapse
Affiliation(s)
- B R Braun
- Department of Microbiology and Immunology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143-0414, USA
| | | |
Collapse
|
449
|
Sengar AS, Markley NA, Marini NJ, Young D. Mkh1, a MEK kinase required for cell wall integrity and proper response to osmotic and temperature stress in Schizosaccharomyces pombe. Mol Cell Biol 1997; 17:3508-19. [PMID: 9199286 PMCID: PMC232204 DOI: 10.1128/mcb.17.7.3508] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We have identified a Schizosaccharomyces pombe gene, mkh1, that encodes a MEK kinase (MEKK) homolog. The coding region of mkh1 is contained within a single exon encoding a 1,116-amino-acid protein. The putative catalytic domain of Mkh1 is 54% identical to the catalytic domain of S. cerevisiae Bck1, the most closely related protein. Deletion of mkh1 did not significantly affect cell growth or division under standard conditions. However, mkh1delta cell growth was inhibited by high KCl or NaCl concentrations. mkh1delta cells required a longer time to reenter the cell cycle after prolonged stationary-phase arrest. Also, mkh1delta cells exhibited a round cell shape, while overexpression of Mkh1 resulted in an elongated cell shape. mkh1delta cells exhibited a more dramatic phenotype when grown in nutrient-limiting conditions at high temperature or in hyperosmotic medium. In such conditions, completion of cytokinesis was inhibited, resulting in the growth of pseudohyphal filaments with multiple septa and nuclei. Also, mkh1delta cells were hypersensitive to beta-glucanase treatment. Together these results suggest that Mkh1 regulates cell morphology, cell wall integrity, salt resistance, cell cycle reentry from stationary-phase arrest, and filamentous growth in response to stress. These phenotypes are essentially identical to those exhibited by cells lacking Pmk1/Spm1, a recently identified mitogen-activated protein kinase. Our evidence suggests that Pmk1/Spm1 acts downstream from Mkh1 in a common pathway. Our results also suggest that Mkh1 and Pck2 act independently to maintain cell wall integrity, cell morphology, and salt resistance but act in opposition to regulate filamentous growth.
Collapse
Affiliation(s)
- A S Sengar
- Department of Medical Biochemistry, University of Calgary Health Science Centre, Alberta, Canada
| | | | | | | |
Collapse
|
450
|
Chao Q, Rothenberg M, Solano R, Roman G, Terzaghi W, Ecker JR. Activation of the ethylene gas response pathway in Arabidopsis by the nuclear protein ETHYLENE-INSENSITIVE3 and related proteins. Cell 1997; 89:1133-44. [PMID: 9215635 DOI: 10.1016/s0092-8674(00)80300-1] [Citation(s) in RCA: 572] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mutations in the Arabidopsis ETHYLENE-INSENSITIVE3 (EIN3) gene severely limit a plant's response to the gaseous hormone ethylene. ein3 mutants show a loss of ethylene-mediated effects including gene expression, the triple response, cell growth inhibition, and accelerated senescence. EIN3 acts downstream of the histidine kinase ethylene receptor, ETR1, and the Raf-like kinase, CTR1. The EIN3 gene encodes a novel nuclear-localized protein that shares sequence similarity, structural features, and genetic function with three EIN3-LIKE (EIL) proteins. In addition to EIN3, EIL1 orEIL2 were able to complement ein3, suggesting their participation in the ethylene signaling pathway. Overexpression of EIN3 or EIL1 in wild-type or ethylene-insensitive2 plants conferred constitutive ethylene phenotypes, indicating their sufficiency for activation of the pathway in the absence of ethylene.
Collapse
Affiliation(s)
- Q Chao
- Department of Biology, Plant Science Institute, University of Pennsylvania, Philadelphia 19104-6018, USA
| | | | | | | | | | | |
Collapse
|