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Vandermeulen MD, Cullen PJ. Ecological inducers of the yeast filamentous growth pathway reveal environment-dependent roles for pathway components. mSphere 2023; 8:e0028423. [PMID: 37732804 PMCID: PMC10597418 DOI: 10.1128/msphere.00284-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 07/31/2023] [Indexed: 09/22/2023] Open
Abstract
Signaling modules, such as mitogen-activated protein kinase (MAPK) pathways, are evolutionarily conserved drivers of cell differentiation and stress responses. In many fungal species including pathogens, MAPK pathways control filamentous growth, where cells differentiate into an elongated cell type. The convenient model budding yeast Saccharomyces cerevisiae undergoes filamentous growth by the filamentous growth (fMAPK) pathway; however, the inducers of the pathway remain unclear, perhaps because pathway activity has been mainly studied in laboratory conditions. To address this knowledge gap, an ecological framework was used, which uncovered new fMAPK pathway inducers, including pectin, a material found in plants, and the metabolic byproduct ethanol. We also show that induction by a known inducer of the pathway, the non-preferred carbon source galactose, required galactose metabolism and induced the pathway differently than glucose limitation or other non-preferred carbon sources. By exploring fMAPK pathway function in fruit, we found that induction of the pathway led to visible digestion of fruit rind through a known target, PGU1, which encodes a pectolytic enzyme. Combinations of inducers (galactose and ethanol) stimulated the pathway to near-maximal levels, which showed dispensability of several fMAPK pathway components (e.g., mucin sensor, p21-activated kinase), but not others (e.g., adaptor, MAPKKK) and required the Ras2-protein kinase A pathway. This included a difference between the transcription factor binding partners for the pathway, as Tec1p, but not Ste12p, was partly dispensable for fMAPK pathway activity. Thus, by exploring ecologically relevant stimuli, new modes of MAPK pathway signaling were uncovered, perhaps revealing how a pathway can respond differently to specific environments. IMPORTANCE Filamentous growth is a cell differentiation response and important aspect of fungal biology. In plant and animal fungal pathogens, filamentous growth contributes to virulence. One signaling pathway that regulates filamentous growth is an evolutionarily conserved MAPK pathway. The yeast Saccharomyces cerevisiae is a convenient model to study MAPK-dependent regulation of filamentous growth, although the inducers of the pathway are not clear. Here, we exposed yeast cells to ecologically relevant compounds (e.g., plant compounds), which identified new inducers of the MAPK pathway. In combination, the inducers activated the pathway to near-maximal levels but did not cause detrimental phenotypes associated with previously identified hyperactive alleles. This context allowed us to identify conditional bypass for multiple pathway components. Thus, near-maximal induction of a MAPK pathway by ecologically relevant inducers provides a powerful tool to assess cellular signaling during a fungal differentiation response.
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Affiliation(s)
| | - Paul J. Cullen
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, USA
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2
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Bardwell L, Thorner J. Mitogen-activated protein kinase (MAPK) cascades-A yeast perspective. Enzymes 2023; 54:137-170. [PMID: 37945169 DOI: 10.1016/bs.enz.2023.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Discovery of the class of protein kinase now dubbed a mitogen (or messenger)-activated protein kinase (MAPK) is an illustrative example of how disparate lines of investigation can converge and reveal an enzyme family universally conserved among eukaryotes, from single-celled microbes to humans. Moreover, elucidation of the circuitry controlling MAPK function defined a now overarching principle in enzyme regulation-the concept of an activation cascade mediated by sequential phosphorylation events. Particularly ground-breaking for this field of exploration were the contributions of genetic approaches conducted using several model organisms, but especially the budding yeast Saccharomyces cerevisiae. Notably, examination of how haploid yeast cells respond to their secreted peptide mating pheromones was crucial in pinpointing genes encoding MAPKs and their upstream activators. Fully contemporaneous biochemical analysis of the activities elicited upon stimulation of mammalian cells by insulin and other growth- and differentiation-inducing factors lead eventually to the demonstration that components homologous to those in yeast were involved. Continued studies of these pathways in yeast were integral to other foundational discoveries in MAPK signaling, including the roles of tethering, scaffolding and docking interactions.
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Affiliation(s)
- Lee Bardwell
- Department of Developmental and Cell Biology, School of Biological Sciences, University of California, Irvine, Irvine, CA, United States
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, College of Letters and Science, University of California, Berkeley, Berkeley, CA, United States.
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3
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Shin JH, Park BS, Kim KS. The CsSTE50 Adaptor Protein in Mitogen-Activated Protein Kinase Cascades Is Essential for Pepper Anthracnose Disease of Colletotrichum scovillei. THE PLANT PATHOLOGY JOURNAL 2022; 38:593-602. [PMID: 36503188 PMCID: PMC9742795 DOI: 10.5423/ppj.oa.06.2022.0074] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 09/24/2022] [Indexed: 06/17/2023]
Abstract
Anthracnose, caused by the ascomycete fungus Colletotrichum scovillei, is a destructive disease in pepper. The fungus germinates and develops an infection structure called an appressorium on the plant surface. Several signaling cascades, including cAMP-mediated signaling and mitogen-activated protein kinase (MAPK) cascades, are involved in fungal development and pathogenicity in plant pathogenic fungi, but this has not been well studied in the fruit-infecting fungus C. scovillei. Ste50 is an adaptor protein interacting with multiple upstream components to activate the MAPK cascades. Here, we characterized the CsSTE50 gene of C. scovillei, a homolog of Magnaporthe oryzae MST50 that functions in MAPK cascades, by gene knockout. The knockout mutant ΔCsste50 had pleiotropic phenotypes in development and pathogenicity. Compared with the wild-type, the mutants grew faster and produced more conidia on regular agar but were more sensitive to osmotic stress. On artificial and plant surfaces, the conidia of the mutant showed significantly reduced germination and failed to form appressoria. The mutant was completely non-pathogenic on pepper fruits with or without wounds, indicating that pre-penetration and invasive growth were both defective in the mutant. Our results show that the adaptor protein CsSTE50 plays a role in vegetative growth, conidiation, germination, appressorium formation, and pathogenicity in C. scovillei.
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Affiliation(s)
| | | | - Kyoung Su Kim
- Corresponding author: Phone) +82-33-250-6435, FAX) +82-33-259-5558, E-mail)
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4
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The Adaptor Protein UvSte50 Governs Fungal Pathogenicity of Ustilaginoidea virens via the MAPK Signaling Pathway. J Fungi (Basel) 2022; 8:jof8090954. [PMID: 36135679 PMCID: PMC9503583 DOI: 10.3390/jof8090954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/22/2022] [Accepted: 08/31/2022] [Indexed: 11/16/2022] Open
Abstract
The mitogen-activated protein kinase (MAPK) signaling pathways regulate diverse cellular processes and have been partially characterized in the rice false smut fungus Ustilaginoidea virens. UvSte50 has been identified as a homolog to Saccharomyces cerevisiae Ste50, which is known to be an adaptor protein for MAPK cascades. ΔUvste50 was found to be defective in conidiation, sensitive to hyperosmotic and oxidative stresses, and non-pathogenic. The mycelial expansion of ΔUvste50 inside spikelets of rice terminated at stamen filaments, eventually resulting in a lack of formation of false smut balls on spikelets. We determined that UvSte50 directly interacts with both UvSte7 (MAPK kinase; MEK) and UvSte11 (MAPK kinase kinase; MEKK), where the Ras-association (RA) domain of UvSte50 is indispensable for its interaction with UvSte7. UvSte50 also interacts with UvHog1, a MAP kinase of the Hog1-MAPK pathway, which is known to have important roles in hyphal growth and stress responses in U. virens. In addition, affinity capture-mass spectrometry analysis and yeast two-hybrid assay were conducted, through which we identified the interactions of UvSte50 with UvRas2, UvAc1 (adenylate cyclase), and UvCap1 (cyclase-associated protein), key components of the Ras/cAMP signaling pathway in U. virens. Together, UvSte50 functions as an adaptor protein interacting with multiple components of the MAPK and Ras/cAMP signaling pathways, thus playing critical role in plant infection by U. virens.
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5
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An adaptor protein BmSte50 interacts with BmSte11 MAPKKK and is involved in host infection, conidiation, melanization, and sexual development in Bipolaris maydis. MYCOSCIENCE 2020. [DOI: 10.1016/j.myc.2019.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Inostroza D, Hernández C, Seco D, Navarro G, Olivera-Nappa A. Cell cycle and protein complex dynamics in discovering signaling pathways. J Bioinform Comput Biol 2019; 17:1950011. [PMID: 31230498 DOI: 10.1142/s0219720019500112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Signaling pathways are responsible for the regulation of cell processes, such as monitoring the external environment, transmitting information across membranes, and making cell fate decisions. Given the increasing amount of biological data available and the recent discoveries showing that many diseases are related to the disruption of cellular signal transduction cascades, in silico discovery of signaling pathways in cell biology has become an active research topic in past years. However, reconstruction of signaling pathways remains a challenge mainly because of the need for systematic approaches for predicting causal relationships, like edge direction and activation/inhibition among interacting proteins in the signal flow. We propose an approach for predicting signaling pathways that integrates protein interactions, gene expression, phenotypes, and protein complex information. Our method first finds candidate pathways using a directed-edge-based algorithm and then defines a graph model to include causal activation relationships among proteins, in candidate pathways using cell cycle gene expression and phenotypes to infer consistent pathways in yeast. Then, we incorporate protein complex coverage information for deciding on the final predicted signaling pathways. We show that our approach improves the predictive results of the state of the art using different ranking metrics.
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Affiliation(s)
- Daniel Inostroza
- 1 Computer Science Department, University of Concepción, Edmundo Larenas, Concepción 4030000, Chile
| | - Cecilia Hernández
- 1 Computer Science Department, University of Concepción, Edmundo Larenas, Concepción 4030000, Chile.,2 Center for Biotechnology and Bioengineering (CeBiB), Santiago, Chile
| | - Diego Seco
- 1 Computer Science Department, University of Concepción, Edmundo Larenas, Concepción 4030000, Chile.,3 IMFD - Millennium Institute for Foundational Research on Data, Chile
| | - Gonzalo Navarro
- 4 Center for Biotechnology and Bioengineering (CeBiB), Department of Computer Science, University of Chile, Santiago, Chile
| | - Alvaro Olivera-Nappa
- 5 Center for Biotechnology and Bioengineering (CeBiB), Department of Chemical Engineering and Biotechnology, University of Chile, Santiago, Chile
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7
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Li G, Zhang X, Tian H, Choi YE, Tao WA, Xu JR. MST50 is involved in multiple MAP kinase signaling pathways in Magnaporthe oryzae. Environ Microbiol 2017; 19:1959-1974. [PMID: 28244240 DOI: 10.1111/1462-2920.13710] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 02/17/2017] [Accepted: 02/19/2017] [Indexed: 12/31/2022]
Abstract
Appressorium formation plays a critical role in Magnaporthe oryzae. Mst50 is an adapter protein of the Mst11-Mst7-Pmk1 cascade that is essential for appressorium formation. To further characterize its functions, affinity purification was used to identify Mst50-interacting proteins (MIPs) in this study. Two of the MIPs are Mst11 and Mst7 that are known to interact with Mst50 for Pmk1 activation. Surprisingly, two other MIPs are Mck1 and Mkk2 that are the upstream kinases of the Mps1 pathway. Domain deletion analysis showed that the sterile alpha-motif of Mst50 but not the Ras-association domain was important for its interaction with Mck1 and responses to cell wall and oxidative stresses. The mst50 mutant was reduced in Mps1 activation under stress conditions. MIP11 encodes a RACK1 protein that also interacted with Mck1. Deletion of MIP11 resulted in defects in cell wall integrity, Mps1 phosphorylation and plant infection. Furthermore, Mst50 interacted with histidine kinase Hik1, and the mst50 mutant was reduced in Osm1 phosphorylation. These results indicated that Mst50 is involved in all three MAPK pathways in M. oryzae although its functions differ in each pathway. Several MIPs are conserved hypothetical proteins and may be involved in responses to various signals and crosstalk among signaling pathways.
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Affiliation(s)
- Guotian Li
- Purdue-NWAFU Joint Research Center, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China.,Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Xue Zhang
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Huan Tian
- Purdue-NWAFU Joint Research Center, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China
| | - Yoon-E Choi
- Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, Seoul, 136-713, Republic of Korea
| | - W Andy Tao
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Jin-Rong Xu
- Purdue-NWAFU Joint Research Center, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi, 712100, China.,Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
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8
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Leng G, Song K. Direct interaction of Ste11 and Mkk1/2 through Nst1 integrates high-osmolarity glycerol and pheromone pathways to the cell wall integrity MAPK pathway. FEBS Lett 2016; 590:148-60. [PMID: 26787465 DOI: 10.1002/1873-3468.12039] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Revised: 11/28/2015] [Accepted: 12/03/2015] [Indexed: 11/11/2022]
Abstract
Coordination and cross talks of MAPK pathways are critical for signaling efficiency, but their mechanisms are not well understood. Slt2, the MAP kinase of cell wall integrity pathway (CWI), is activated by heat stress even in the absence of upstream components of this pathway, suggesting a supplementary input for Slt2 activation. Here, we identify a new interaction of Ste11 and Mkk1, mediated by Nst1 that connects the high-osmolarity glycerol and pheromone pathways directly to CWI pathway in response to heat and pheromone. We suggest that Ser(407) and Thr(411) are novel residues of Mkk1 activated by these MAPK pathways.
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Affiliation(s)
- Gang Leng
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
| | - Kiwon Song
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
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9
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Vicedo E, Gasik Z, Dong YA, Goldberg T, Rost B. Protein disorder reduced in Saccharomyces cerevisiae to survive heat shock. F1000Res 2015; 4:1222. [PMID: 26673203 PMCID: PMC4670006 DOI: 10.12688/f1000research.7178.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/02/2015] [Indexed: 11/20/2022] Open
Abstract
Recent experiments established that a culture of
Saccharomyces cerevisiae (baker’s yeast) survives sudden high temperatures by specifically duplicating the entire chromosome III and two chromosomal fragments (from IV and XII). Heat shock proteins (HSPs) are not significantly over-abundant in the duplication. In contrast, we suggest a simple algorithm to “
postdict” the experimental results: Find a small enough chromosome with minimal protein disorder and duplicate this region. This algorithm largely explains all observed duplications. In particular, all regions duplicated in the experiment reduced the overall content of protein disorder. The differential analysis of the functional makeup of the duplication remained inconclusive. Gene Ontology (GO) enrichment suggested over-representation in processes related to reproduction and nutrient uptake. Analyzing the protein-protein interaction network (PPI) revealed that few network-central proteins were duplicated. The predictive hypothesis hinges upon the concept of reducing proteins with long regions of disorder in order to become less sensitive to heat shock attack.
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Affiliation(s)
- Esmeralda Vicedo
- Department of Informatics, Bioinformatics & Computational Biology, TUM, Munich, Germany ; Institute of Experimental Physics, Division of Biophysics, University of Warsaw, Warsaw, Poland
| | - Zofia Gasik
- Department of Informatics, Bioinformatics & Computational Biology, TUM, Munich, Germany ; Graduate School of Information Science in Health, TUM, Munich, Germany
| | - Yu-An Dong
- Department of Informatics, Bioinformatics & Computational Biology, TUM, Munich, Germany ; Institute of Systems Biology, Shanghai University, Shanghai, China
| | - Tatyana Goldberg
- Department of Informatics, Bioinformatics & Computational Biology, TUM, Munich, Germany
| | - Burkhard Rost
- Department of Informatics, Bioinformatics & Computational Biology, TUM, Munich, Germany ; Institute of Advanced Study, TUM, Munich, Germany ; Institute for Food and Plant Sciences WZW, TUM, Freising, Germany
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10
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Binding of the Extracellular Eight-Cysteine Motif of Opy2 to the Putative Osmosensor Msb2 Is Essential for Activation of the Yeast High-Osmolarity Glycerol Pathway. Mol Cell Biol 2015; 36:475-87. [PMID: 26598606 DOI: 10.1128/mcb.00853-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 11/16/2015] [Indexed: 02/08/2023] Open
Abstract
To adapt to environmental high osmolarity, the budding yeast Saccharomyces cerevisiae activates the Hog1 mitogen-activated protein kinase, which regulates diverse osmoadaptive responses. Hog1 is activated through the high-osmolarity glycerol (HOG) pathway, which consists of independent upstream signaling routes termed the SLN1 branch and the SHO1 branch. Here, we report that the extracellular cysteine-rich (CR) domain of the transmembrane-anchor protein Opy2 binds to the Hkr1-Msb2 homology (HMH) domain of the putative osmosensor Msb2 and that formation of the Opy2-Msb2 complex is essential for osmotic activation of Hog1 through the MSB2 subbranch of the SHO1 branch. By analyzing the phenotypes of mutants with Opy2 cysteine-to-alanine mutations, we deduced that the CR domain forms four intramolecular disulfide bonds. To probe for the potential induction of conformational changes in the Opy2-Msb2 complex by osmostress, we constructed mutants with a site-specific Cys-to-Ala mutation of the Opy2 CR domain and mutants with a Cys substitution of the Msb2 HMH domain. Each of these mutants had a reduced cysteine. These mutants were then combinatorially cross-linked using chemical cross-linkers of different lengths. Cross-linking between Opy2 Cys48 and Msb2 Cys1023 was sensitive to osmotic changes, suggesting that osmostress induced a conformational change. We therefore propose that the Opy2-Msb2 complex might serve as an osmosensor.
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11
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Tatebayashi K, Yamamoto K, Nagoya M, Takayama T, Nishimura A, Sakurai M, Momma T, Saito H. Osmosensing and scaffolding functions of the oligomeric four-transmembrane domain osmosensor Sho1. Nat Commun 2015; 6:6975. [PMID: 25898136 PMCID: PMC4411306 DOI: 10.1038/ncomms7975] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/18/2015] [Indexed: 11/09/2022] Open
Abstract
The yeast high osmolarity glycerol (HOG) pathway activates the Hog1 MAP kinase, which coordinates adaptation to high osmolarity conditions. Here we demonstrate that the four-transmembrane (TM) domain protein Sho1 is an osmosensor in the HKR1 sub-branch of the HOG pathway. Crosslinking studies indicate that Sho1 forms planar oligomers of the dimers-of-trimers architecture by dimerizing at the TM1/TM4 interface and trimerizing at the TM2/TM3 interface. High external osmolarity induces structural changes in the Sho1 TM domains and Sho1 binding to the cytoplasmic adaptor protein Ste50, which leads to Hog1 activation. Besides its osmosensing function, the Sho1 oligomer serves as a scaffold. By binding to the TM proteins Opy2 and Hkr1 at the TM1/TM4 and TM2/TM3 interface, respectively, Sho1 forms a multi-component signalling complex that is essential for Hog1 activation. Our results illuminate how the four TM domains of Sho1 dictate the oligomer structure as well as its osmosensing and scaffolding functions.
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Affiliation(s)
- Kazuo Tatebayashi
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Katsuyoshi Yamamoto
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Miho Nagoya
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Tomomi Takayama
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Akiko Nishimura
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Megumi Sakurai
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takashi Momma
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Haruo Saito
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
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Gu Q, Chen Y, Liu Y, Zhang C, Ma Z. The transmembrane protein FgSho1 regulates fungal development and pathogenicity via the MAPK module Ste50-Ste11-Ste7 in Fusarium graminearum. THE NEW PHYTOLOGIST 2015; 206:315-328. [PMID: 25388878 DOI: 10.1111/nph.13158] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2014] [Accepted: 10/09/2014] [Indexed: 06/04/2023]
Abstract
The mitogen-activated protein kinase (MAPK) signaling pathways have been characterized in Fusarium graminearum. Currently, the upstream sensors of these pathways are unknown. Biological functions of a transmembrane protein FgSho1 were investigated using a target gene deletion strategy. The relationship between FgSho1 and the MAPK cassette FgSte50-Ste11-Ste7 was analyzed in depth. The transmembrane protein FgSho1 is required for conidiation, full virulence, and deoxynivalenol (DON) biosynthesis in F. graminearum. Furthermore, FgSho1 and FgSln1 have an additive effect on virulence of F. graminearum. The yeast two-hybrid, coimmunoprecipitation, colocalization and affinity capture-mass spectrometry analyses strongly indicated that FgSho1 physically interacts with the MAPK module FgSte50-Ste11-Ste7. Similar to the FgSho1 mutant, the mutants of FgSte50, FgSte11, and FgSte7 were defective in conidiation, pathogenicity, and DON biosynthesis. In addition, FgSho1 plays a minor role in the response to osmotic stress but it is involved in the cell wall integrity pathway, which is independent of the module FgSte50-Ste11-Ste7 in F. graminearum. Collectively, results of this study strongly indicate that FgSho1 regulates fungal development and pathogenicity via the MAPK module FgSte50-Ste11-Ste7 in F. graminearum, which is different from what is known in the budding yeast Saccharomyces cerevisiae.
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Affiliation(s)
- Qin Gu
- Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Yun Chen
- Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Ye Liu
- Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Chengqi Zhang
- Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Zhonghua Ma
- Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
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13
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Role of phosphatidylinositol phosphate signaling in the regulation of the filamentous-growth mitogen-activated protein kinase pathway. EUKARYOTIC CELL 2015; 14:427-40. [PMID: 25724886 DOI: 10.1128/ec.00013-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 02/23/2015] [Indexed: 01/04/2023]
Abstract
Reversible phosphorylation of the phospholipid phosphatidylinositol (PI) is a key event in the determination of organelle identity and an underlying regulatory feature in many biological processes. Here, we investigated the role of PI signaling in the regulation of the mitogen-activated protein kinase (MAPK) pathway that controls filamentous growth in yeast. Lipid kinases that generate phosphatidylinositol 4-phosphate [PI(4)P] at the Golgi (Pik1p) or PI(4,5)P2 at the plasma membrane (PM) (Mss4p and Stt4p) were required for filamentous-growth MAPK pathway signaling. Introduction of a conditional allele of PIK1 (pik1-83) into the filamentous (Σ1278b) background reduced MAPK activity and caused defects in invasive growth and biofilm/mat formation. MAPK regulatory proteins that function at the PM, including Msb2p, Sho1p, and Cdc42p, were mislocalized in the pik1-83 mutant, which may account for the signaling defects of the PI(4)P kinase mutants. Other PI kinases (Fab1p and Vps34p), and combinations of PIP (synaptojanin-type) phosphatases, also influenced the filamentous-growth MAPK pathway. Loss of these proteins caused defects in cell polarity, which may underlie the MAPK signaling defect seen in these mutants. In line with this possibility, disruption of the actin cytoskeleton by latrunculin A (LatA) dampened the filamentous-growth pathway. Various PIP signaling mutants were also defective for axial budding in haploid cells, cell wall construction, or proper regulation of the high-osmolarity glycerol response (HOG) pathway. Altogether, the study extends the roles of PI signaling to a differentiation MAPK pathway and other cellular processes.
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14
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Msb2 is a Ste11 membrane concentrator required for full activation of the HOG pathway. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1849:722-30. [PMID: 25689021 DOI: 10.1016/j.bbagrm.2015.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 02/02/2015] [Accepted: 02/09/2015] [Indexed: 01/05/2023]
Abstract
The high osmolarity glycerol (HOG) pathway, composed of membrane-associated osmosensors, adaptor proteins and core signaling kinases, is essential for the survival of yeast cells under hyper-osmotic stress. Here, we studied how the MAPKKK Ste11 might change its protein interaction profile during acute stress exposure, with an emphasis on the sensory system of the so-called Sho1/Msb2 signaling branch. To characterize the transience of protein-protein interactions we utilized a recently described enzymatic in vivo protein proximity assay (M-track). Accordingly, interaction signals between Ste11 and many of its signaling partners can already be detected even under basal conditions. In most cases these signals increase after stress induction. All the interactions are completely dependent on the function of the Ste11-adaptor protein Ste50. Moreover, the presence of either Msb2 or Hkr1 is necessary for observing the interaction between Ste11 and scaffolding factors such as Sho1 and Pbs2. Additional assays suggest that Msb2 is not only in close proximity to Ste11 but might function as an individual Ste11 concentrator at the plasma membrane. Our results confirm the existence of negative feedback systems targeting the protein levels of Ste11 and Msb2 and also hint at changes in the dissociation rates of intermediate signaling complexes.
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Cdc42p-interacting protein Bem4p regulates the filamentous-growth mitogen-activated protein kinase pathway. Mol Cell Biol 2014; 35:417-36. [PMID: 25384973 DOI: 10.1128/mcb.00850-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The ubiquitous Rho (Ras homology) GTPase Cdc42p can function in different settings to regulate cell polarity and cellular signaling. How Cdc42p and other proteins are directed to function in a particular context remains unclear. We show that the Cdc42p-interacting protein Bem4p regulates the mitogen-activated protein kinase (MAPK) pathway that controls filamentous growth in Saccharomyces cerevisiae. Bem4p controlled the filamentous-growth pathway but not other MAPK pathways (mating or high-osmolarity glycerol response [HOG]) that also require Cdc42p and other shared components. Bem4p associated with the plasma membrane (PM) protein, Sho1p, to regulate MAPK activity and cell polarization under nutrient-limiting conditions that favor filamentous growth. Bem4p also interacted with the major activator of Cdc42p, the guanine nucleotide exchange factor (GEF) Cdc24p, which we show also regulates the filamentous-growth pathway. Bem4p interacted with the pleckstrin homology (PH) domain of Cdc24p, which functions in an autoinhibitory capacity, and was required, along with other pathway regulators, to maintain Cdc24p at polarized sites during filamentous growth. Bem4p also interacted with the MAPK kinase kinase (MAPKKK) Ste11p. Thus, Bem4p is a new regulator of the filamentous-growth MAPK pathway and binds to general proteins, like Cdc42p and Ste11p, to promote a pathway-specific response.
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16
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Pincus D, Ryan CJ, Smith RD, Brent R, Resnekov O. Assigning quantitative function to post-translational modifications reveals multiple sites of phosphorylation that tune yeast pheromone signaling output. PLoS One 2013; 8:e56544. [PMID: 23554854 PMCID: PMC3595240 DOI: 10.1371/journal.pone.0056544] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 01/15/2013] [Indexed: 12/19/2022] Open
Abstract
Cell signaling systems transmit information by post-translationally modifying signaling proteins, often via phosphorylation. While thousands of sites of phosphorylation have been identified in proteomic studies, the vast majority of sites have no known function. Assigning functional roles to the catalog of uncharacterized phosphorylation sites is a key research challenge. Here we present a general approach to address this challenge and apply it to a prototypical signaling pathway, the pheromone response pathway in Saccharomyces cerevisiae. The pheromone pathway includes a mitogen activated protein kinase (MAPK) cascade activated by a G-protein coupled receptor (GPCR). We used published mass spectrometry-based proteomics data to identify putative sites of phosphorylation on pheromone pathway components, and we used evolutionary conservation to assign priority to a list of candidate MAPK regulatory sites. We made targeted alterations in those sites, and measured the effects of the mutations on pheromone pathway output in single cells. Our work identified six new sites that quantitatively tuned system output. We developed simple computational models to find system architectures that recapitulated the quantitative phenotypes of the mutants. Our results identify a number of putative phosphorylation events that contribute to adjust the input-output relationship of this model eukaryotic signaling system. We believe this combined approach constitutes a general means not only to reveal modification sites required to turn a pathway on and off, but also those required for more subtle quantitative effects that tune pathway output. Our results suggest that relatively small quantitative influences from individual phosphorylation events endow signaling systems with plasticity that evolution may exploit to quantitatively tailor signaling outcomes.
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Affiliation(s)
- David Pincus
- Molecular Sciences Institute, Berkeley, California, United States of America
| | - Christopher J. Ryan
- Molecular Sciences Institute, Berkeley, California, United States of America
| | - Richard D. Smith
- Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Roger Brent
- Molecular Sciences Institute, Berkeley, California, United States of America
| | - Orna Resnekov
- Molecular Sciences Institute, Berkeley, California, United States of America
- * E-mail:
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17
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Abstract
An appropriate response and adaptation to hyperosmolarity, i.e., an external osmolarity that is higher than the physiological range, can be a matter of life or death for all cells. It is especially important for free-living organisms such as the yeast Saccharomyces cerevisiae. When exposed to hyperosmotic stress, the yeast initiates a complex adaptive program that includes temporary arrest of cell-cycle progression, adjustment of transcription and translation patterns, and the synthesis and retention of the compatible osmolyte glycerol. These adaptive responses are mostly governed by the high osmolarity glycerol (HOG) pathway, which is composed of membrane-associated osmosensors, an intracellular signaling pathway whose core is the Hog1 MAP kinase (MAPK) cascade, and cytoplasmic and nuclear effector functions. The entire pathway is conserved in diverse fungal species, while the Hog1 MAPK cascade is conserved even in higher eukaryotes including humans. This conservation is illustrated by the fact that the mammalian stress-responsive p38 MAPK can rescue the osmosensitivity of hog1Δ mutations in response to hyperosmotic challenge. As the HOG pathway is one of the best-understood eukaryotic signal transduction pathways, it is useful not only as a model for analysis of osmostress responses, but also as a model for mathematical analysis of signal transduction pathways. In this review, we have summarized the current understanding of both the upstream signaling mechanism and the downstream adaptive responses to hyperosmotic stress in yeast.
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Affiliation(s)
- Haruo Saito
- Division of Molecular Cell Signaling, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8638, Japan, and
| | - Francesc Posas
- Cell Signaling Unit, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, E-08003 Barcelona, Spain
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The filamentous growth MAPK Pathway Responds to Glucose Starvation Through the Mig1/2 transcriptional repressors in Saccharomyces cerevisiae. Genetics 2012; 192:869-87. [PMID: 22904036 DOI: 10.1534/genetics.112.142661] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In the budding yeast S. cerevisiae, nutrient limitation induces a MAPK pathway that regulates filamentous growth and biofilm/mat formation. How nutrient levels feed into the regulation of the filamentous growth pathway is not entirely clear. We characterized a newly identified MAPK regulatory protein of the filamentous growth pathway, Opy2. A two-hybrid screen with the cytosolic domain of Opy2 uncovered new interacting partners including a transcriptional repressor that functions in the AMPK pathway, Mig1, and its close functional homolog, Mig2. Mig1 and Mig2 coregulated the filamentous growth pathway in response to glucose limitation, as did the AMP kinase Snf1. In addition to associating with Opy2, Mig1 and Mig2 interacted with other regulators of the filamentous growth pathway including the cytosolic domain of the signaling mucin Msb2, the MAP kinase kinase Ste7, and the MAP kinase Kss1. As for Opy2, Mig1 overproduction dampened the pheromone response pathway, which implicates Mig1 and Opy2 as potential regulators of pathway specificity. Taken together, our findings provide the first regulatory link in yeast between components of the AMPK pathway and a MAPK pathway that controls cellular differentiation.
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Abstract
Filamentous growth is a nutrient-regulated growth response that occurs in many fungal species. In pathogens, filamentous growth is critical for host-cell attachment, invasion into tissues, and virulence. The budding yeast Saccharomyces cerevisiae undergoes filamentous growth, which provides a genetically tractable system to study the molecular basis of the response. Filamentous growth is regulated by evolutionarily conserved signaling pathways. One of these pathways is a mitogen activated protein kinase (MAPK) pathway. A remarkable feature of the filamentous growth MAPK pathway is that it is composed of factors that also function in other pathways. An intriguing challenge therefore has been to understand how pathways that share components establish and maintain their identity. Other canonical signaling pathways-rat sarcoma/protein kinase A (RAS/PKA), sucrose nonfermentable (SNF), and target of rapamycin (TOR)-also regulate filamentous growth, which raises the question of how signals from multiple pathways become integrated into a coordinated response. Together, these pathways regulate cell differentiation to the filamentous type, which is characterized by changes in cell adhesion, cell polarity, and cell shape. How these changes are accomplished is also discussed. High-throughput genomics approaches have recently uncovered new connections to filamentous growth regulation. These connections suggest that filamentous growth is a more complex and globally regulated behavior than is currently appreciated, which may help to pave the way for future investigations into this eukaryotic cell differentiation behavior.
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20
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Jami SK, Clark GB, Ayele BT, Roux SJ, Kirti PB. Identification and characterization of annexin gene family in rice. PLANT CELL REPORTS 2012; 31:813-825. [PMID: 22167239 DOI: 10.1007/s00299-011-1201-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 11/24/2011] [Accepted: 11/29/2011] [Indexed: 05/31/2023]
Abstract
Plant annexins are Ca(2+)-dependent phospholipid-binding proteins and are encoded by multigene families. They are implicated in the regulation of plant development as well as protection from drought and other stresses. They are well characterized in Arabidopsis, however no such characterization of rice annexin gene family has been reported thus far. With the availability of the rice genome sequence information, we have identified ten members of the rice annexin gene family. At the protein level, they share 16-64% identity with predicted molecular masses ranging from 32 to 40 kDa. Phylogenetic analysis of rice annexins together with annexins from other monocots led to their classification into five different orthologous groups and share similar motif patterns in their protein sequences. Expression analysis by real-time RT-PCR revealed differential temporal and spatial regulation of these genes. The rice annexin genes are also found to be regulated in seedling stage by various abiotic stressors including salinity, drought, heat and cold. Additionally, in silico analysis of the putative upstream sequences was analyzed for the presence of stress-responsive cis-elements. These results provide a basis for further functional characterization of specific rice annexin genes at the tissue/developmental level and in response to abiotic stresses.
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Affiliation(s)
- Sravan Kumar Jami
- Department of Plant Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
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21
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Fu J, Mares C, Lizcano A, Liu Y, Wickes BL. Insertional mutagenesis combined with an inducible filamentation phenotype reveals a conserved STE50 homologue in Cryptococcus neoformans that is required for monokaryotic fruiting and sexual reproduction. Mol Microbiol 2011; 79:990-1007. [PMID: 21299652 DOI: 10.1111/j.1365-2958.2010.07501.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cryptococcus neoformans typically grows in a yeast-like morphology; however, under specific conditions the fungus can produce hyphae that are either dikaryotic or monokaryotic. In this study, we developed a simple method for inducing robust monokaryotic fruiting and combined the assay with Agrobacterium tumefaciens insertional mutagenesis to screen for hyphal mutants. A C. neoformans homologue of the Saccharomyces cerevisiae STE50 gene was identified and characterized. STE50 was found to be required for sexual reproduction and monokaryotic fruiting. Ste50p has conserved SAM and RA domains, as well as two SH3 domains specific to basidiomycetous Ste50 proteins. Analysis of protein-protein interaction showed that Ste50p can interact with Ste11p and Ste20p, and epistasis experiments placed STE50 between STE20 and STE11. Genetic analysis of the role of STE50 in sexual reproduction showed that it was required for all steps, from response to pheromone to production of hyphae. Analysis of the effect of individual Ste50p domains on sexual reproduction and monokaryotic fruiting revealed domain-specific effects for both processes. This study revealed that the C. neoformans STE50 gene has both conserved and novel functions during sexual reproduction and monokaryotic fruiting, and these functions are domain-dependent.
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Affiliation(s)
- J Fu
- Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Shapiro RS, Robbins N, Cowen LE. Regulatory circuitry governing fungal development, drug resistance, and disease. Microbiol Mol Biol Rev 2011; 75:213-67. [PMID: 21646428 PMCID: PMC3122626 DOI: 10.1128/mmbr.00045-10] [Citation(s) in RCA: 384] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Pathogenic fungi have become a leading cause of human mortality due to the increasing frequency of fungal infections in immunocompromised populations and the limited armamentarium of clinically useful antifungal drugs. Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus are the leading causes of opportunistic fungal infections. In these diverse pathogenic fungi, complex signal transduction cascades are critical for sensing environmental changes and mediating appropriate cellular responses. For C. albicans, several environmental cues regulate a morphogenetic switch from yeast to filamentous growth, a reversible transition important for virulence. Many of the signaling cascades regulating morphogenesis are also required for cells to adapt and survive the cellular stresses imposed by antifungal drugs. Many of these signaling networks are conserved in C. neoformans and A. fumigatus, which undergo distinct morphogenetic programs during specific phases of their life cycles. Furthermore, the key mechanisms of fungal drug resistance, including alterations of the drug target, overexpression of drug efflux transporters, and alteration of cellular stress responses, are conserved between these species. This review focuses on the circuitry regulating fungal morphogenesis and drug resistance and the impact of these pathways on virulence. Although the three human-pathogenic fungi highlighted in this review are those most frequently encountered in the clinic, they represent a minute fraction of fungal diversity. Exploration of the conservation and divergence of core signal transduction pathways across C. albicans, C. neoformans, and A. fumigatus provides a foundation for the study of a broader diversity of pathogenic fungi and a platform for the development of new therapeutic strategies for fungal disease.
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Affiliation(s)
| | | | - Leah E. Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
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23
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The Gα subunit signals through the Ste50 protein during the mating pheromone response in the yeast Kluyveromyces lactis. EUKARYOTIC CELL 2011; 10:540-6. [PMID: 21335532 DOI: 10.1128/ec.00285-10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Yeast mating signal transduction pathways require a heterotrimeric G protein composed of Gα, Gβ, and Gγ subunits connected to a mitogen-activated protein kinase (MAPK) module. While in Saccharomyces cerevisiae elimination of Gα induces constitutive activation of the mating pathway, in Kluyveromyces lactis it produces partial sterility, which indicates that K. lactis Gα (KlGα) is required to positively activate mating. We use physical interaction experiments to determine that KlGα interacts with the adaptor protein KlSte50p. The Ras association (RA) domain of KlSte50p favored interaction with the GDP-bound KlGα subunit, and when the KlGα protein is constitutively activated, the interaction drops significantly. Additionally, KlSte50p strongly associates with the MAPK kinase kinase (MAPKKK) KlSte11p through its sterile alpha motif (SAM) domain. Genetic experiments placed KlSte50p downstream of the G protein α subunit, indicating that KlGα may stimulate the mating pathway via KlSte50p. Fusion of KlSte50p to the KlGβ subunit partially eliminated the requirement of KlGα for mating, indicating that one contribution of KlGα to the mating pathway is to facilitate plasma membrane anchoring of KlSte50p.
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24
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Jung KW, Kim SY, Okagaki LH, Nielsen K, Bahn YS. Ste50 adaptor protein governs sexual differentiation of Cryptococcus neoformans via the pheromone-response MAPK signaling pathway. Fungal Genet Biol 2010; 48:154-65. [PMID: 20971202 DOI: 10.1016/j.fgb.2010.10.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 10/05/2010] [Accepted: 10/13/2010] [Indexed: 11/26/2022]
Abstract
The mitogen-activated protein kinase (MAPK) pathways control diverse cellular functions in pathogenic fungi, including sexual differentiation, stress response, and maintenance of cell wall integrity. Here we characterized a Cryptococcus neoformans gene, which is homologous to the yeast Ste50 that is known to play an important role in mating pheromone response and stress response as an adaptor protein to the Ste11 MAPK kinase kinase in Saccharomyces cerevisiae. The C. neoformans Ste50 was not involved in any of the stress responses or virulence factor production (capsule and melanin) that are controlled by the HOG and Ras/cAMP signaling pathways. However, Ste50 was required for mating in both serotype A and serotype D C. neoformans strains. The ste50Δ mutant was completely defective in cell-cell fusion and mating pheromone production. Double mutation of the STE50 gene blocked increased production of pheromone and the hyper-filamentation phenotype of cells deleted of the CRG1 gene, which encodes the RGS protein that negatively regulates pheromone responsive G-protein signaling via the MAPK pathway. Regardless of the presence of the basidiomycota-specific SH3 domains of Ste50 that are known to be required for full virulence of Ustilago maydis, Ste50 was dispensable for virulence of C. neoformans in a murine model of cryptococcosis. In conclusion, the Ste50 adaptor protein controls sexual differentiation of C. neoformans via the pheromone-responsive MAPK pathway but is not required for virulence.
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Affiliation(s)
- Kwang-Woo Jung
- Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, Seoul, Republic of Korea
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25
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Armadillo-repeat protein functions: questions for little creatures. Trends Cell Biol 2010; 20:470-81. [PMID: 20688255 DOI: 10.1016/j.tcb.2010.05.003] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 05/11/2010] [Accepted: 05/17/2010] [Indexed: 01/24/2023]
Abstract
Armadillo (ARM)-repeat proteins form a large family with diverse and fundamental functions in many eukaryotes. ARM-repeat proteins have largely been characterised in multicellular organisms and much is known about how a subset of these proteins function. The structure of ARM-repeats allows proteins containing them to be functionally very versatile. Are the ARM-repeat proteins in 'little creatures' as multifunctional as their better-studied relatives? The time is now right to start analysing ARM-repeat proteins in these new systems to better understand their cell biology. Here, we review recent advances in understanding the many cellular roles of both well-known and novel ARM-repeat proteins.
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26
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Schamber A, Leroch M, Diwo J, Mendgen K, Hahn M. The role of mitogen-activated protein (MAP) kinase signalling components and the Ste12 transcription factor in germination and pathogenicity of Botrytis cinerea. MOLECULAR PLANT PATHOLOGY 2010; 11:105-19. [PMID: 20078780 PMCID: PMC6640347 DOI: 10.1111/j.1364-3703.2009.00579.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In all fungi studied so far, mitogen-activated protein (MAP) kinase cascades serve as central signalling complexes that are involved in various aspects of growth, stress response and infection. In this work, putative components of the yeast Fus3/Kss1-type MAP kinase cascade and the putative downstream transcription factor Ste12 were analysed in the grey mould fungus Botrytis cinerea. Deletion mutants of the MAP triple kinase Ste11, the MAP kinase kinase Ste7 and the MAP kinase adaptor protein Ste50 all resulted in phenotypes similar to that of the previously described BMP1 MAP kinase mutant, namely defects in germination, delayed vegetative growth, reduced size of conidia, lack of sclerotia formation and loss of pathogenicity. Mutants lacking Ste12 showed normal germination, but delayed infection as a result of low penetration efficiency. Two differently spliced ste12 transcripts were detected, and both were able to complement the ste12 mutant, except for a defect in sclerotium formation, which was only corrected by the full-sized transcript. Overexpression of the smaller ste12 transcript resulted in delayed germination and strongly reduced infection. Bc-Gas2, a homologue of Magnaporthe grisea Gas2 that is required for appressorial function, was found to be non-essential for growth and infection, but its expression was under the control of both Bmp1 and Ste12. In summary, the role and regulatory connections of the Fus3/Kss1-type MAP kinase cascade in B. cinerea revealed both common and unique properties compared with those of other plant pathogenic fungi, and provide evidence for a regulatory link between the BMP1 MAP kinase cascade and Ste12.
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Affiliation(s)
- Astrid Schamber
- Department of Biology, University of Kaiserslautern, PO Box 3049, 67653 Kaiserslautern, Germany
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27
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Hog1 mitogen-activated protein kinase (MAPK) interrupts signal transduction between the Kss1 MAPK and the Tec1 transcription factor to maintain pathway specificity. EUKARYOTIC CELL 2009; 8:606-16. [PMID: 19218425 DOI: 10.1128/ec.00005-09] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In Saccharomyces cerevisiae, the mating, filamentous growth (FG), and high-osmolarity glycerol (HOG) mitogen-activated protein kinase (MAPK) signaling pathways share components and yet mediate distinct responses to different extracellular signals. Cross talk is suppressed between the mating and FG pathways because mating signaling induces the destruction of the FG transcription factor Tec1. We show here that HOG pathway activation results in phosphorylation of the FG MAPK, Kss1, and the MAPKK, Ste7. However, FG transcription is not activated because HOG signaling prevents the activation of Tec1. In contrast to the mating pathway, we find that the mechanism involves the inhibition of DNA binding by Tec1 rather than its destruction. We also find that nuclear accumulation of Tec1 is not affected by HOG signaling. Inhibition by Hog1 is apparently indirect since it does not require any of the consensus S/TP MAPK phosphorylation sites on Tec1, its DNA-binding partner Ste12, or the associated regulators Dig1 or Dig2. It also does not require the consensus MAPK sites of the Ste11 activator Ste50, in contrast to a recent proposal for a role for negative feedback in specificity. Our results demonstrate that HOG signaling interrupts the FG pathway signal transduction between the phosphorylation of Kss1 and the activation of DNA binding by Tec1.
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28
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Bhunia A, Domadia PN, Mohanram H, Bhattacharjya S. NMR structural studies of the Ste11 SAM domain in the dodecyl phosphocholine micelle. Proteins 2009; 74:328-43. [PMID: 18618697 DOI: 10.1002/prot.22166] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The sterile alpha-motif (SAM), a relatively small ( approximately 70 amino acids) interaction domain, is found in a variety of proteins involved in cell signaling, transcription regulation, and scaffolding. The Ste11 protein kinase from the mitogen activated protein kinase (MAPK) signaling cascades of the budding yeast is regulated by a SAM domain located at the N-terminus of full-length protein. In solution, the Ste11 SAM domain exists as a well-folded dimeric structure that is involved in interaction with the cognate SAM domain from an adaptor protein Ste50. In this work, we show that the Ste11 SAM domain has an intrinsic affinity towards the lipid membranes. The solution conformation of the Ste11 SAM determined in perdeuterated DPC micelle, using NMR spectroscopy, is defined by five helices of different lengths connected by a number of loops. In the micelle bound state, the non-polar and aromatic residues of the Ste11 SAM lack a native-like packing and are presumably engaged in interactions with the micelle. Using two different paramagnetic doxyl-lipids; we have mapped out localization of Ste11 SAM residues at the micelle surface. Most of the residues appear to localize at the interfacial region of the micelle. However, a number of non-polar residues from the central region of the domain are found to be located inside the core of the micelle including residues from the helix 4 and a loop between helix 2 and helix 3. Isothermal titration calorimetry studies demonstrate that a facile insertion of the Ste11 SAM into the DPC micelle is primarily driven by a large change in enthalpy, -50 kcal/mol with an apparent equilibrium association constant (Ka) of 7.86 x 10(6) M(-1). Interestingly, an interfacial mutant L60R of the Ste11 SAM lacking the dimeric structure does not show detectable interactions with the lipid micelle. The micelle-bound structure of the Ste11 SAM domain described in this work may have potential implications in the regulation of MAPK signaling whereby positioning of the Ste11 protein in close proximity to the membrane may facilitate efficient phosphorylation of the Ste11 kinase by the membrane attached upstream Ste20/pak kinase.
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Affiliation(s)
- Anirban Bhunia
- Biomolecular NMR and Drug Discovery Laboratory, Division of Structural and Computational Biology, School of Biological Sciences, Nanyang Technological University, Singapore
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29
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The G-alpha protein GNA3 of Hypocrea jecorina (Anamorph Trichoderma reesei) regulates cellulase gene expression in the presence of light. EUKARYOTIC CELL 2009; 8:410-20. [PMID: 19136572 DOI: 10.1128/ec.00256-08] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although the enzymes enabling Hypocrea jecorina (anamorph Trichoderma reesei) to degrade the insoluble substrate cellulose have been investigated in some detail, little is still known about the mechanism by which cellulose signals its presence to the fungus. In order to investigate the possible role of a G-protein/cyclic AMP signaling pathway, the gene encoding GNA3, which belongs to the adenylate cyclase-activating class III of G-alpha subunits, was cloned. gna3 is clustered in tandem with the mitogen-activated protein kinase gene tmk3 and the glycogen phosphorylase gene gph1. The gna3 transcript is upregulated in the presence of light and is almost absent in the dark. A strain bearing a constitutively activated version of GNA3 (gna3QL) exhibits strongly increased cellulase transcription in the presence of the inducer cellulose and in the presence of light, whereas a gna3 antisense strain showed delayed cellulase transcription under this condition. However, the gna3QL mutant strain was unable to form cellulases in the absence of cellulose. The necessity of light for stimulation of cellulase transcription by GNA3 could not be overcome in a mutant which expressed gna3 under control of the constitutive gpd1 promoter also in darkness. We conclude that the previously reported stimulation of cellulase gene transcription by light, but not the direct transmission of the cellulose signal, involves the function and activation of GNA3. The upregulation of gna3 by light is influenced by the light modulator ENVOY, but GNA3 itself has no effect on transcription of the light regulator genes blr1, blr2, and env1. Our data for the first time imply an involvement of a G-alpha subunit in a light-dependent signaling event in fungi.
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30
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Hao N, Zeng Y, Elston TC, Dohlman HG. Control of MAPK specificity by feedback phosphorylation of shared adaptor protein Ste50. J Biol Chem 2008; 283:33798-802. [PMID: 18854322 DOI: 10.1074/jbc.c800179200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many different signaling pathways share common components but nevertheless invoke distinct physiological responses. In yeast, the adaptor protein Ste50 functions in multiple mitogen-activated protein (MAP) kinase pathways, each with unique dynamical and developmental properties. Although Kss1 activity is sustained and promotes invasive growth, Hog1 activity is transient and promotes cell adaptation to osmotic stress. Here we show that osmotic stress activates Kss1 as well as Hog1. We show further that Hog1 phosphorylates Ste50 and that phosphorylation of Ste50 limits the duration of Kss1 activation and prevents invasive growth under high osmolarity growth conditions. Thus feedback regulation of a shared component can restrict the activity of a competing MAP kinase to ensure signal fidelity.
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Affiliation(s)
- Nan Hao
- Department of Biochemistry, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA
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31
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Rho5p is involved in mediating the osmotic stress response in Saccharomyces cerevisiae, and its activity is regulated via Msi1p and Npr1p by phosphorylation and ubiquitination. EUKARYOTIC CELL 2008; 7:1441-9. [PMID: 18621925 DOI: 10.1128/ec.00120-08] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Small GTPases of the Rho family act as molecular switches, and modulation of the GTP-bound state of Rho proteins is a well-characterized means of regulating their signaling activity in vivo. In contrast, the regulation of Rho-type GTPases by posttranslational modifications is poorly understood. Here, we present evidence of the control of the Saccharomyces cerevisiae Rho-type GTPase Rho5p by phosphorylation and ubiquitination. Rho5p binds to Ste50p, and the expression of the activated RHO5(Q91H) allele in an Deltaste50 strain is lethal under conditions of osmotic stress. An overexpression screen identified RGD2 and MSI1 as being high-copy suppressors of the osmotic sensitivity of this lethality. Rgd2p had been identified as being a possible Rho5p GTPase-activating protein based on an in vitro assay; this result supports its function as a regulator of Rho5p activity in vivo. MSI1 was previously identified as being a suppressor of hyperactive Ras/cyclic AMP signaling, where it antagonizes Npr1p kinase activity and promotes ubiquitination. Here, we show that Msi1p also acts via Npr1p to suppress activated Rho5p signaling. Rho5p is ubiquitinated, and its expression is lethal in a strain that is compromised for proteasome activity. These data identify Rho5p as being a target of Msi1p/Npr1p regulation and describe a regulatory circuit involving phosphorylation and ubiquitination.
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Slaughter BD, Huff JM, Wiegraebe W, Schwartz JW, Li R. SAM domain-based protein oligomerization observed by live-cell fluorescence fluctuation spectroscopy. PLoS One 2008; 3:e1931. [PMID: 18431466 PMCID: PMC2291563 DOI: 10.1371/journal.pone.0001931] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Accepted: 02/27/2008] [Indexed: 11/19/2022] Open
Abstract
Sterile-alpha-motif (SAM) domains are common protein interaction motifs observed in organisms as diverse as yeast and human. They play a role in protein homo- and hetero-interactions in processes ranging from signal transduction to RNA binding. In addition, mutations in SAM domain and SAM-mediated oligomers have been linked to several diseases. To date, the observation of heterogeneous SAM-mediated oligomers in vivo has been elusive, which represents a common challenge in dissecting cellular biochemistry in live-cell systems. In this study, we report the oligomerization and binding stoichiometry of high-order, multi-component complexes of (SAM) domain proteins Ste11 and Ste50 in live yeast cells using fluorescence fluctuation methods. Fluorescence cross-correlation spectroscopy (FCCS) and 1-dimensional photon counting histogram (1dPCH) confirm the SAM-mediated interaction and oligomerization of Ste11 and Ste50. Two-dimensional PCH (2dPCH), with endogenously expressed proteins tagged with GFP or mCherry, uniquely indicates that Ste11 and Ste50 form a heterogeneous complex in the yeast cytosol comprised of a dimer of Ste11 and a monomer of Ste50. In addition, Ste50 also exists as a high order oligomer that does not interact with Ste11, and the size of this oligomer decreases in response to signals that activate the MAP kinase cascade. Surprisingly, a SAM domain mutant of Ste50 disrupted not only the Ste50 oligomers but also Ste11 dimerization. These results establish an in vivo model of Ste50 and Ste11 homo- and hetero-oligomerization and highlight the usefulness of 2dPCH for quantitative dissection of complex molecular interactions in genetic model organisms such as yeast.
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Affiliation(s)
- Brian D. Slaughter
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Joseph M. Huff
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Winfried Wiegraebe
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Joel W. Schwartz
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Rong Li
- The Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
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Bashor CJ, Helman NC, Yan S, Lim WA. Using engineered scaffold interactions to reshape MAP kinase pathway signaling dynamics. Science 2008; 319:1539-43. [PMID: 18339942 DOI: 10.1126/science.1151153] [Citation(s) in RCA: 261] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Scaffold proteins link signaling molecules into linear pathways by physically assembling them into complexes. Scaffolds may also have a higher-order role as signal-processing hubs, serving as the target of feedback loops that optimize signaling amplitude and timing. We demonstrate that the Ste5 scaffold protein can be used as a platform to systematically reshape output of the yeast mating MAP kinase pathway. We constructed synthetic positive- and negative-feedback loops by dynamically regulating recruitment of pathway modulators to an artificial binding site on Ste5. These engineered circuits yielded diverse behaviors: ultrasensitive dose response, accelerated or delayed response times, and tunable adaptation. Protein scaffolds provide a flexible platform for reprogramming cellular responses and could be exploited to engineer cells with novel therapeutic and biotechnological functions.
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Affiliation(s)
- Caleb J Bashor
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, 600 16th Street, San Francisco, CA 94158, USA
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34
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Taylor RJ, Siegel AF, Galitski T. Network motif analysis of a multi-mode genetic-interaction network. Genome Biol 2008; 8:R160. [PMID: 17683534 PMCID: PMC2374991 DOI: 10.1186/gb-2007-8-8-r160] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Revised: 05/01/2007] [Accepted: 08/02/2007] [Indexed: 12/03/2022] Open
Abstract
Statistical and computational methods for the extraction of biological information from dense multi-mode genetic-interaction networks were developed and implemented in open-source software. Different modes of genetic interaction indicate different functional relationships between genes. The extraction of biological information from dense multi-mode genetic-interaction networks demands appropriate statistical and computational methods. We developed such methods and implemented them in open-source software. Motifs extracted from multi-mode genetic-interaction networks form functional subnetworks, highlight genes dominating these subnetworks, and reveal genetic reflections of the underlying biochemical system.
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Affiliation(s)
- R James Taylor
- Institute for Systems Biology, N. 34th Street, Seattle, WA 98103 USA.
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35
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Klosterman SJ, Martinez-Espinoza AD, Andrews DL, Seay JR, Gold SE. Ubc2, an ortholog of the yeast Ste50p adaptor, possesses a basidiomycete-specific carboxy terminal extension essential for pathogenicity independent of pheromone response. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2008; 21:110-121. [PMID: 18052888 DOI: 10.1094/mpmi-21-1-0110] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Proteins involved in the mitogen-activated protein (MAP) kinase pathway controlling mating, morphogenesis, and pathogenicity have been identified previously in the fungus Ustilago maydis. One of these, the Ubc2 adaptor protein, possesses a basidiomycete-specific structure. In addition to containing sterile alpha motif (SAM) and ras association (RA) domains typical of Ste50-like adaptor proteins found in the fungal phylum Ascomycota, Ubc2 also contains two C-terminal SH3 domains. Yeast two-hybrid assays indicated that Ubc2 interacts with the MAP kinase-kinase kinase Ubc4 via the SAM domains at each of their respective N-termini. Site-directed mutagenesis of ubc2 and complementation analyses revealed that the SAM and RA domains of Ubc2 are essential for filamentous growth. These data support a role for the ascomycete-like N-terminus of Ubc2 in regulating pheromone-responsive mating and morphogenesis analogous to the role of Ste50p in Saccharomyces cerevisiae. In contrast, C-terminal deletion mutants were fully capable of filamentous growth and mating. However, surprisingly, these strains were nonpathogenic. Further, directed mutagenesis of the C-terminus revealed that both SH3 domains are required for pathogenicity. These results suggest that the Basidiomycota have retained the mating and morphogenetic functions of Ste50-type proteins in the N-terminal half of their Ubc2-type adaptors but, additionally, have integrated C-terminal SH3 domains that are critical for additional signal transduction mechanisms, including those that lead to pathogenesis.
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36
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Protein kinases involved in mating and osmotic stress in the yeast Kluyveromyces lactis. EUKARYOTIC CELL 2007; 7:78-85. [PMID: 18024598 DOI: 10.1128/ec.00362-07] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Systematic disruption of genes encoding kinases and mitogen-activated protein kinases (MAPKs) was performed in Kluyveromyces lactis haploid cells. The mutated strains were assayed by their capacity to mate and to respond to hyperosmotic stress. The K. lactis Ste11p (KlSte11p) MAPK kinase kinase (MAPKKK) was found to act in both mating and osmoresponse pathways while the scaffold KlSte5p and the MAPK KlFus3p appeared to be specific for mating. The p21-activated kinase KlSte20p and the kinase KlSte50p participated in both pathways. Protein association experiments showed interaction of KlSte50p and KlSte20p with Galpha and Gbeta, respectively, the G protein subunits involved in the mating pathway. Both KlSte50p and KlSte20p also showed interaction with KlSte11p. Disruption mutants of the K. lactis PBS2 (KlPBS2) and KlHOG1 genes of the canonical osmotic response pathway resulted in mutations sensitive to high salt and high sorbitol but dispensable for mating. Mutations that eliminate the MAPKK KlSte7p activity had a strong effect on mating and also showed sensitivity to osmotic stress. Finally, we found evidence of physical interaction between KlSte7p and KlHog1p, in addition to diminished Hog1p phosphorylation after a hyperosmotic shock in cells lacking KlSte7p. This study reveals novel roles for components of transduction systems in yeast.
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37
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Arga KY, Onsan ZI, Kirdar B, Ulgen KO, Nielsen J. Understanding signaling in yeast: Insights from network analysis. Biotechnol Bioeng 2007; 97:1246-58. [PMID: 17252576 DOI: 10.1002/bit.21317] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Reconstruction of protein interaction networks that represent groups of proteins contributing to the same cellular function is a key step towards quantitative studies of signal transduction pathways. Here we present a novel approach to reconstruct a highly correlated protein interaction network and to identify previously unknown components of a signaling pathway through integration of protein-protein interaction data, gene expression data, and Gene Ontology annotations. A novel algorithm is designed to reconstruct a highly correlated protein interaction network which is composed of the candidate proteins for signal transduction mechanisms in yeast Saccharomyces cerevisiae. The high efficiency of the reconstruction process is proved by a Receiver Operating Characteristic curve analysis. Identification and scoring of the possible linear pathways enables reconstruction of specific sub-networks for glucose-induction signaling and high osmolarity MAPK signaling in S. cerevisiae. All of the known components of these pathways are identified together with several new "candidate" proteins, indicating the successful reconstructions of two model pathways involved in S. cerevisiae. The integrated approach is hence shown useful for (i) prediction of new signaling pathways, (ii) identification of unknown members of documented pathways, and (iii) identification of network modules consisting of a group of related components that often incorporate the same functional mechanism.
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Affiliation(s)
- K Yalçin Arga
- Department of Chemical Engineering, Boğaziçi University, 34342 Istanbul, Turkey
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38
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Bluhm BH, Zhao X, Flaherty JE, Xu JR, Dunkle LD. RAS2 regulates growth and pathogenesis in Fusarium graminearum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:627-36. [PMID: 17555271 DOI: 10.1094/mpmi-20-6-0627] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Fusarium graminearum is a ubiquitous pathogen of cereal crops, including wheat, barley, and maize. Diseases caused by F. graminearum are of particular concern because harvested grains frequently are contaminated with harmful mycotoxins such as deoxynivalenol (DON). In this study, we explored the role of Ras GTPases in pathogenesis. The genome of F. graminearum contains two putative Ras GTPase-encoding genes. The two genes (RAS1 and RAS2) showed different patterns of expression under different conditions of nutrient availability and in various mutant backgrounds. RAS2 was dispensable for survival but, when disrupted, caused a variety of morphological defects, including slower growth on solid media, delayed spore germination, and significant reductions in virulence on wheat heads and maize silks. Intracellular cAMP levels were not affected by deletion of RAS2 and exogenous treatment of the ras2 mutant with cAMP did not affect phenotypic abnormalities, thus indicating that RAS2 plays a minor or no role in cAMP signaling. However, phosphorylation of the mitogen-activated protein (MAP) kinase Gpmk1 and expression of a secreted lipase (FGL1) required for infection were reduced significantly in the ras2 mutant. Based on these observations, we hypothesize that RAS2 regulates growth and virulence in F. graminearum by regulating the Gpmk1 MAP kinase pathway.
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Affiliation(s)
- B H Bluhm
- Crop Production & Pest Control Research Unit, United States Department of Agriculture-Agricultural Research Service, West Lafayette, IN 47907, USA.
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39
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Poplinski A, Hopp C, Ramezani-Rad M. Ste50 adaptor protein influences Ras/cAMP-driven stress-response and cell survival in Saccharomyces cerevisiae. Curr Genet 2007; 51:257-68. [PMID: 17318632 DOI: 10.1007/s00294-007-0124-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 02/02/2007] [Accepted: 02/03/2007] [Indexed: 11/28/2022]
Abstract
The Ste50 adaptor protein is involved in a variety of cellular pathways that yeast cells use to adapt rapidly to environmental changes. A highly activated Ras-cyclic AMP (cAMP) pathway by deletion of the high-affinity cAMP-dependent phosphodiesterase 2 (PDE2) leads to repression of a stress mediated response and cell survival. Here we show that inactivation of STE50 confers a synthetic genetic interaction with pde2Delta. A hyperosmotic stress growth defect of ste50Delta pde2Delta cells is exacerbated by extracellular cAMP or by galactose as the sole carbon source in the medium. The inactivation of the serine/threonine protein-kinase Akt homologue Sch9 increase stress resistance and extend chronological life span. By pde2Delta-dependent increase of the Ras-cAMP pathway activity, inactivation of STE50 results in an extreme shortening of life span and oxidative stress sensitivity of sch9Delta mutants. Furthermore, sch9Delta can promote transcription of the small heat shock protein HSP26 in a PDE2-dependent manner; however, sch9Delta can promote transcription of the mitochondrial superoxide dismutase SOD2 in a PDE2- and STE50-dependent manner. These data indicate that inactivation of STE50 influences stress tolerance in mutants of the Ras-cAMP pathway, which is a major determinant of intrinsic stress tolerance and cell survival of the Saccharomyces cerevisiae.
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Affiliation(s)
- Andreas Poplinski
- Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr.1, Geb. 26.12, 40225, Düsseldorf, Germany
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40
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Xu JR, Zhao X, Dean RA. From genes to genomes: a new paradigm for studying fungal pathogenesis in Magnaporthe oryzae. ADVANCES IN GENETICS 2007; 57:175-218. [PMID: 17352905 DOI: 10.1016/s0065-2660(06)57005-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Magnaporthe oryzae is the most destructive fungal pathogen of rice worldwide and because of its amenability to classical and molecular genetic manipulation, availability of a genome sequence, and other resources it has emerged as a leading model system to study host-pathogen interactions. This chapter reviews recent progress toward elucidation of the molecular basis of infection-related morphogenesis, host penetration, invasive growth, and host-pathogen interactions. Related information on genome analysis and genomic studies of plant infection processes is summarized under specific topics where appropriate. Particular emphasis is placed on the role of MAP kinase and cAMP signal transduction pathways and unique features in the genome such as repetitive sequences and expanded gene families. Emerging developments in functional genome analysis through large-scale insertional mutagenesis and gene expression profiling are detailed. The chapter concludes with new prospects in the area of systems biology, such as protein expression profiling, and highlighting remaining crucial information needed to fully appreciate host-pathogen interactions.
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Affiliation(s)
- Jin-Rong Xu
- Department of Botany and Plant Pathology, Purdue University West Lafayette, Indiana 47907, USA
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41
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Klosterman SJ, Perlin MH, Garcia-Pedrajas M, Covert SF, Gold SE. Genetics of morphogenesis and pathogenic development of Ustilago maydis. ADVANCES IN GENETICS 2007; 57:1-47. [PMID: 17352901 DOI: 10.1016/s0065-2660(06)57001-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ustilago maydis has emerged as an important model system for the study of fungi. Like many fungi, U. maydis undergoes remarkable morphological transitions throughout its life cycle. Fusion of compatible, budding, haploid cells leads to the production of a filamentous dikaryon that penetrates and colonizes the plant, culminating in the production of diploid teliospores within fungal-induced plant galls or tumors. These dramatic morphological transitions are controlled by components of various signaling pathways, including the pheromone-responsive MAP kinase and cAMP/PKA (cyclic AMP/protein kinase A) pathways, which coregulate the dimorphic switch and sexual development of U. maydis. These signaling pathways must somehow cooperate with the regulation of the cytoskeletal and cell cycle machinery. In this chapter, we provide an overview of these processes from pheromone perception and mating to gall production and sporulation in planta. Emphasis is placed on the genetic determinants of morphogenesis and pathogenic development of U. maydis and on the fungus-host interaction. Additionally, we review advances in the development of tools to study U. maydis, including the recently available genome sequence. We conclude with a brief assessment of current challenges and future directions for the genetic study of U. maydis.
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Affiliation(s)
- Steven J Klosterman
- Department of Plant Pathology, University of Georgia, Athens, Georgia 30602, USA
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42
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Park G, Xue C, Zhao X, Kim Y, Orbach M, Xu JR. Multiple upstream signals converge on the adaptor protein Mst50 in Magnaporthe grisea. THE PLANT CELL 2006; 18:2822-35. [PMID: 17056708 PMCID: PMC1626611 DOI: 10.1105/tpc.105.038422] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Rice blast fungus (Magnaporthe grisea) forms a highly specialized infection structure for plant penetration, the appressorium, the formation and growth of which are regulated by the Mst11-Mst7-Pmk1 mitogen-activated protein kinase cascade. We characterized the MST50 gene that directly interacts with both MST11 and MST7. Similar to the mst11 mutant, the mst50 mutant was defective in appressorium formation, sensitive to osmotic stresses, and nonpathogenic. Expressing a dominant active MST7 allele in mst50 complemented its defects in appressorium but not lesion formation. The sterile alpha-motif (SAM) domain of Mst50 was essential for its interaction with Mst11 and for appressorium formation. Although the SAM and Ras-association domain (RAD) of Mst50 were dispensable for its interaction with Mst7, deletion of RAD reduced appressorium formation and virulence on rice (Oryza sativa) seedlings. The interaction between Mst50 and Mst7 or Mst11 was detected by coimmunoprecipitation assays in developing appressoria. Mst50 also interacts with Ras1, Ras2, Cdc42, and Mgb1 in yeast two-hybrid assays. Expressing a dominant active RAS2 allele in the wild-type strain but not in mst50 stimulated abnormal appressorium formation. These results indicate that MST50 functions as an adaptor protein interacting with multiple upstream components and plays critical roles in activating the Pmk1 cascade for appressorium formation and plant infection in M. grisea.
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Affiliation(s)
- Gyungsoon Park
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907, USA
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43
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Tatebayashi K, Yamamoto K, Tanaka K, Tomida T, Maruoka T, Kasukawa E, Saito H. Adaptor functions of Cdc42, Ste50, and Sho1 in the yeast osmoregulatory HOG MAPK pathway. EMBO J 2006; 25:3033-44. [PMID: 16778768 PMCID: PMC1500976 DOI: 10.1038/sj.emboj.7601192] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Accepted: 05/18/2006] [Indexed: 12/24/2022] Open
Abstract
The yeast high osmolarity glycerol (HOG) signaling pathway can be activated by either of the two upstream pathways, termed the SHO1 and SLN1 branches. When stimulated by high osmolarity, the SHO1 branch activates an MAP kinase module composed of the Ste11 MAPKKK, the Pbs2 MAPKK, and the Hog1 MAPK. To investigate how osmostress activates this MAPK module, we isolated both gain-of-function and loss-of-function alleles in four key genes involved in the SHO1 branch, namely SHO1, CDC42, STE50, and STE11. These mutants were characterized using an HOG-dependent reporter gene, 8xCRE-lacZ. We found that Cdc42, in addition to binding and activating the PAK-like kinases Ste20 and Cla4, binds to the Ste11-Ste50 complex to bring activated Ste20/Cla4 to their substrate Ste11. Activated Ste11 and its HOG pathway-specific substrate, Pbs2, are brought together by Sho1; the Ste11-Ste50 complex binds to the cytoplasmic domain of Sho1, to which Pbs2 also binds. Thus, Cdc42, Ste50, and Sho1 act as adaptor proteins that control the flow of the osmostress signal from Ste20/Cla4 to Ste11, then to Pbs2.
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Affiliation(s)
- Kazuo Tatebayashi
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Katsuyoshi Yamamoto
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Keiichiro Tanaka
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Taichiro Tomida
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Takashi Maruoka
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Eri Kasukawa
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Haruo Saito
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, Minato-ku, Tokyo, Japan
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Division of Molecular Cell Signaling, Institute of Medical Sciences, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. Tel.: +81 3 5449 5505; Fax: +81 3 5449 5701; E-mail:
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44
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Eisman B, Alonso-Monge R, Román E, Arana D, Nombela C, Pla J. The Cek1 and Hog1 mitogen-activated protein kinases play complementary roles in cell wall biogenesis and chlamydospore formation in the fungal pathogen Candida albicans. EUKARYOTIC CELL 2006; 5:347-58. [PMID: 16467475 PMCID: PMC1405885 DOI: 10.1128/ec.5.2.347-358.2006] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.
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Affiliation(s)
- B Eisman
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
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45
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Roignant JY, Hamel S, Janody F, Treisman JE. The novel SAM domain protein Aveugle is required for Raf activation in the Drosophila EGF receptor signaling pathway. Genes Dev 2006; 20:795-806. [PMID: 16600911 PMCID: PMC1447592 DOI: 10.1101/gad.1390506] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Activation of the Raf kinase by GTP-bound Ras is a poorly understood step in receptor tyrosine kinase signaling pathways. One such pathway, the epidermal growth factor receptor (EGFR) pathway, is critical for cell differentiation, survival, and cell cycle regulation in many systems, including the Drosophila eye. We have identified a mutation in a novel gene, aveugle, based on its requirement for normal photoreceptor differentiation. The phenotypes of aveugle mutant cells in the eye and wing imaginal discs resemble those caused by reduction of EGFR pathway function. We show that aveugle is required between ras and raf for EGFR signaling in the eye and for mitogen-activated protein kinase phosphorylation in cell culture. aveugle encodes a small protein with a sterile alpha motif (SAM) domain that can physically interact with the scaffold protein connector enhancer of Ksr (Cnk). We propose that Aveugle acts together with Cnk to promote Raf activation, perhaps by recruiting an activating kinase.
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Affiliation(s)
- Jean-Yves Roignant
- Skirball Institute for Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA
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46
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Rohila JS, Chen M, Chen S, Chen J, Cerny R, Dardick C, Canlas P, Xu X, Gribskov M, Kanrar S, Zhu JK, Ronald P, Fromm ME. Protein-protein interactions of tandem affinity purification-tagged protein kinases in rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 46:1-13. [PMID: 16553892 DOI: 10.1111/j.1365-313x.2006.02671.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Forty-one rice cDNAs encoding protein kinases were fused to the tandem affinity purification (TAP) tag and expressed in transgenic rice plants. The TAP-tagged kinases and interacting proteins were purified from the T1 progeny of the transgenic rice plants and identified by mass spectrometry. Ninety-five percent of the TAP-tagged kinases were recovered. Fifty-six percent of the TAP-tagged kinases were found to interact with other rice proteins. A number of these interactions were consistent with known protein complexes found in other species, validating the TAP-tag method in rice plants. Phosphorylation sites were identified on four of the kinases that interacted with either 14-3-3 proteins or cyclins.
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Affiliation(s)
- Jai S Rohila
- Plant Science Initiative, University of Nebraska, Lincoln, NE 68588, USA
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47
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Truckses DM, Bloomekatz JE, Thorner J. The RA domain of Ste50 adaptor protein is required for delivery of Ste11 to the plasma membrane in the filamentous growth signaling pathway of the yeast Saccharomyces cerevisiae. Mol Cell Biol 2006; 26:912-28. [PMID: 16428446 PMCID: PMC1347046 DOI: 10.1128/mcb.26.3.912-928.2006] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In Saccharomyces cerevisiae, pheromone response requires Ste5 scaffold protein, which ensures efficient G-protein-dependent recruitment of mitogen-activated protein kinase (MAPK) cascade components Ste11 (MAPK kinase kinase), Ste7 (MAPK kinase), and Fus3 (MAPK) to the plasma membrane for activation by Ste20 protein kinase. Ste20, which phosphorylates Ste11 to initiate signaling, is activated by binding to Cdc42 GTPase (membrane anchored via its C-terminal geranylgeranylation). Less clear is how activated and membrane-localized Ste20 contacts Ste11 to trigger invasive growth signaling, which also requires Ste7 and the MAPK Kss1, but not Ste5. Ste50 protein associates constitutively via an N-terminal sterile-alpha motif domain with Ste11, and this interaction is required for optimal invasive growth and hyperosmotic stress (high-osmolarity glycerol [HOG]) signaling but has a lesser role in pheromone response. We show that a conserved C-terminal, so-called "Ras association" (RA) domain in Ste50 is also essential for invasive growth and HOG signaling in vivo. In vitro the Ste50 RA domain is not able to associate with Ras2, but it does associate with Cdc42 and binds to a different face than does Ste20. RA domain function can be replaced by the nine C-terminal, plasma membrane-targeting residues (KKSKKCAIL) of Cdc42, and membrane-targeted Ste50 also suppresses the signaling deficiency of cdc42 alleles specifically defective in invasive growth. Thus, Ste50 serves as an adaptor to tether Ste11 to the plasma membrane and can do so via association with Cdc42, thereby permitting the encounter of Ste11 with activated Ste20.
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Affiliation(s)
- Dagmar M Truckses
- Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Room 16, Barker Hall, Berkeley, CA 94720-3202, USA
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48
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Krantz M, Becit E, Hohmann S. Comparative genomics of the HOG-signalling system in fungi. Curr Genet 2006; 49:137-51. [PMID: 16468042 DOI: 10.1007/s00294-005-0038-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2005] [Revised: 09/09/2005] [Accepted: 09/24/2005] [Indexed: 01/08/2023]
Abstract
Signal transduction pathways play crucial roles in cellular adaptation to environmental changes. In this study, we employed comparative genomics to analyse the high osmolarity glycerol pathway in fungi. This system contains several signalling modules that are used throughout eukaryotic evolution, such as a mitogen-activated protein kinase and a phosphorelay module. Here we describe the identification of pathway components in 20 fungal species. Although certain proteins proved difficult to identify due to low sequence conservation, a main limitation was incomplete, low coverage genomic sequences and fragmentary genome annotation. Still, the pathway was readily reconstructed in each species, and its architecture could be compared. The most striking difference concerned the Sho1 branch, which frequently does not appear to activate the Hog1 MAPK module, although its components are conserved in all but one species. In addition, two species lacked apparent orthologues for the Sln1 osmosensing histidine kinase. All information gathered has been compiled in an MS Excel sheet, which also contains interactive visualisation tools. In addition to primary sequence analysis, we employed analysis of protein size conservation. Protein size appears to be conserved largely independently from primary sequence and thus provides an additional tool for functional analysis and orthologue identification.
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Affiliation(s)
- Marcus Krantz
- Department for Cell and Molecular Biology, Göteborg University, Box 462, 40530 Göteborg, Sweden
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49
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Krantz M, Becit E, Hohmann S. Comparative analysis of HOG pathway proteins to generate hypotheses for functional analysis. Curr Genet 2006; 49:152-65. [PMID: 16468041 DOI: 10.1007/s00294-005-0039-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2005] [Revised: 09/07/2005] [Accepted: 09/24/2005] [Indexed: 12/17/2022]
Abstract
Comparative genomics allows comparison of different proteins that execute presumably identical functions in different organisms. In contrast to paralogues, orthologues per definition perform the same function and interact with the same partners and, consequently, should display conservation in all these properties. We have employed 20 fungal genomes to analyse key components of the high osmolarity glycerol signalling pathway of Saccharomyces cerevisiae. Among the proteins scrutinised are a complete phosphotransfer module, a MAP kinase, two scaffold proteins, one of which is also a MAPKK, and two transcription factors. Sequence alignments, domain structure and size analysis, combined with the rich information available in the literature, allowed us to probe previous structural and functional studies and to generate hypotheses for future experimental studies. Although certain domains are too highly conserved across fungal species for meaningful comparative studies, others, like interaction domains, can be studied in closely related species. Moreover, putative functionally relevant sites for protein modifications can be identified in such comparative studies. We provide several relevant examples and present a number of previously un(der)characterised domains of potential functional significance in osmosensing and signal transduction. We propose that any functional protein analysis in fungi should make use of the unique resource that fungal genome sequences offer.
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Affiliation(s)
- Marcus Krantz
- Department for Cell and Molecular Biology, Göteborg University, Box 462, 40530, Göteborg, Sweden
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50
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Kwan JJ, Warner N, Maini J, Chan Tung KW, Zakaria H, Pawson T, Donaldson LW. Saccharomyces cerevisiae Ste50 Binds the MAPKKK Ste11 Through a Head-to-tail SAM Domain Interaction. J Mol Biol 2006; 356:142-54. [PMID: 16337230 DOI: 10.1016/j.jmb.2005.11.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Revised: 10/27/2005] [Accepted: 11/03/2005] [Indexed: 10/25/2022]
Abstract
In Saccharomyces cerevisiae, signal transduction through pathways governing mating, osmoregulation, and nitrogen starvation depends upon a direct interaction between the sterile alpha motif (SAM) domains of the Ste11 mitogen-activated protein kinase kinase kinase (MAPKKK) and its regulator Ste50. Previously, we solved the NMR structure of the SAM domain from Ste11 and identified two mutants that diminished binding to the Ste50 SAM domain. Building upon the Ste11 study, we present the NMR structure of the monomeric Ste50 SAM domain and a series of mutants bearing substitutions at surface-exposed hydrophobic amino acid residues. The mid-loop (ML) region of Ste11-SAM, defined by helices H3 and H4 and the end-helix (EH) region of Ste50-SAM, defined by helix H5, were sensitive to substitution, indicating that these two surfaces contribute to the high-affinity interaction. The combination of two mutants, Ste11-SAM-L72R and Ste50-SAM-L69R, formed a high-affinity heterodimer unencumbered by competing homotypic interactions that had prevented earlier NMR studies of the wild-type complex. Yeast bearing mutations that prevented the heterotypic Ste11-Ste50 association in vitro presented signaling defects in the mating and high-osmolarity growth pathways.
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Affiliation(s)
- Jamie J Kwan
- Department of Biology, York University, 4700 Keele Street, Toronto, Ont., Canada M3J 1P3
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