1
|
Jang YB, Kim JY, Bahn YS. Unraveling the cryptic functions of mitogen-activated protein kinases Cpk2 and Mpk2 in Cryptococcus neoformans. mBio 2024:e0115624. [PMID: 38874410 DOI: 10.1128/mbio.01156-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 04/30/2024] [Indexed: 06/15/2024] Open
Abstract
Mitogen-activated protein kinase (MAPK) pathways are fundamental to the regulation of biological processes in eukaryotic organisms. The basidiomycete Cryptococcus neoformans, known for causing fungal meningitis worldwide, possesses five MAPKs. Among these, Cpk1, Hog1, and Mpk1 have established roles in sexual reproduction, stress responses, and cell wall integrity. However, the roles of Cpk2 and Mpk2 are less understood. Our study elucidates the functional interplay between the Cpk1/Cpk2 and Mpk1/Mpk2 MAPK pathways in C. neoformans. We discovered that CPK2 overexpression compensates for cpk1Δ mating deficiencies via the Mat2 transcription factor, revealing functional redundancy between Cpk1 and Cpk2. We also found that Mpk2 is phosphorylated in response to cell wall stress, a process regulated by the MAPK kinase (MAP2K) Mkk2 and MAP2K kinases (MAP3Ks) Ssk2 and Ste11. Overexpression of MPK2 partially restores cell wall integrity in mpk1Δ by influencing key cell wall components, such as chitin and the polysaccharide capsule. Contrarily, MPK2 overexpression cannot restore thermotolerance and cell membrane integrity in mpk1Δ. These results suggest that Mpk1 and Mpk2 have redundant and opposing roles in the cellular response to cell wall and membrane stresses. Most notably, the dual deletion of MPK1 and MPK2 restores wild-type mating efficiency in cpk1Δ mutants via upregulation of the mating-regulating transcription factors MAT2 and ZNF2, suggesting that the Mpk1 and Mpk2 cooperate to negatively regulate the pheromone-responsive Cpk1 MAPK pathway. Our research collectively underscores a sophisticated regulatory network of cryptococcal MAPK signaling pathways that intricately govern sexual reproduction and cell wall integrity, thereby controlling fungal development and pathogenicity.IMPORTANCEIn the realm of fungal biology, our study on Cryptococcus neoformans offers pivotal insights into the roles of specific proteins called mitogen-activated protein kinases (MAPKs). Here, we discovered the cryptic functions of Cpk2 and Mpk2, two MAPKs previously overshadowed by their dominant counterparts Cpk1 and Mpk1, respectively. Our findings reveal that these "underdog" proteins are not just backup players; they play crucial roles in vital processes like mating and cell wall maintenance in C. neoformans. Their ability to step in and compensate when their dominant counterparts are absent showcases the adaptability of C. neoformans. This newfound understanding not only enriches our knowledge of fungal MAPK mechanisms but also underscores the intricate balance and interplay of proteins in ensuring the organism's survival and adaptability.
Collapse
Affiliation(s)
- Yu-Byeong Jang
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea
| | - Jin-Young Kim
- Division of Life Science, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea
| | - Yong-Sun Bahn
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Lin CC, Lee WJ, Zeng CY, Chou MY, Lin TJ, Lin CS, Ho MC, Shih MC. SUB1A-1 anchors a regulatory cascade for epigenetic and transcriptional controls of submergence tolerance in rice. PNAS NEXUS 2023; 2:pgad229. [PMID: 37492276 PMCID: PMC10364326 DOI: 10.1093/pnasnexus/pgad229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 06/28/2023] [Indexed: 07/27/2023]
Abstract
Most rice (Oryza sativa) cultivars cannot survive under prolonged submergence. However, some O. sativa ssp. indica cultivars, such as FR13A, are highly tolerant owing to the SUBMERGENCE 1A-1 (SUB1A-1) allele, which encodes a Group VII ethylene-responsive factor (ERFVII) protein; other submergence-intolerant cultivars contain a SUB1A-2 allele. The two alleles differ only by a single substitution at the 186th amino acid position from serine in SUB1A-1 to proline in SUB1A-2 resulting in only SUB1A-1 being able to be phosphorylated. Two other ERFVIIs, ERF66 and ERF67, function downstream of SUB1A-1 to form a regulatory cascade in response to submergence stress. Here, we show that SUB1A-1, but not SUB1A-2, interacts with ADA2b of the ADA2b-GCN5 acetyltransferase complex, in which GCN5 functions as a histone acetyltransferase. Phosphorylation of SUB1A-1 at serine 186 enhances the interaction of SUB1A-1 with ADA2b. ADA2b and GCN5 expression was induced under submergence, suggesting that these two genes might play roles in response to submergence stress. In transient assays, binding of SUB1A-1 to the ERF67 promoter and ERF67 transcription were highly induced when SUB1A-1 was expressed together with the ADA2b-GCN5 acetyltransferase complex. Taken together, these results suggest that phospho-SUB1A-1 recruits the ADA2-GCN5 acetyltransferase complex to modify the chromatin structure of the ERF66/ERF67 promoter regions and activate gene expression, which in turn enhances rice submergence tolerance.
Collapse
Affiliation(s)
| | | | - Cyong-Yu Zeng
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 11529, Taiwan
- Institute of Plant Biology, National Taiwan University, Taipei 10617, Taiwan
| | - Mei-Yi Chou
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Ting-Jhen Lin
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan
| | - Choun-Sea Lin
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Meng-Chiao Ho
- To whom correspondence should be addressed: (M.C.S.); (M.C.H.)
| | - Ming-Che Shih
- To whom correspondence should be addressed: (M.C.S.); (M.C.H.)
| |
Collapse
|
4
|
Scott TD, Xu P, McClean MN. Strain-dependent differences in coordination of yeast signalling networks. FEBS J 2023; 290:2097-2114. [PMID: 36416575 PMCID: PMC10121740 DOI: 10.1111/febs.16689] [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: 06/09/2022] [Revised: 09/30/2022] [Accepted: 10/18/2022] [Indexed: 11/24/2022]
Abstract
The yeast mitogen-activated protein kinase pathways serve as a model system for understanding how network interactions affect the way in which cells coordinate the response to multiple signals. We have quantitatively compared two yeast strain backgrounds YPH499 and ∑1278b (both of which have previously been used to study these pathways) and found several important differences in how they coordinate the interaction between the high osmolarity glycerol (HOG) and mating pathways. In the ∑1278b background, in response to simultaneous stimulus, mating pathway activation is dampened and delayed in a dose-dependent manner. In the YPH499 background, only dampening is dose-dependent. Furthermore, leakage from the HOG pathway into the mating pathway (crosstalk) occurs during osmostress alone in the ∑1278b background only. The mitogen-activated protein kinase Hog1p suppresses crosstalk late in an induction time course in both strains but does not affect the early crosstalk seen in the ∑1278b background. Finally, the kinase Rck2p plays a greater role suppressing late crosstalk in the ∑1278b background than in the YPH499 background. Our results demonstrate that comparisons between laboratory yeast strains provide an important resource for understanding how signalling network interactions are tuned by genetic variation without significant alteration to network structure.
Collapse
Affiliation(s)
- Taylor D. Scott
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Ping Xu
- Lewis-Sigler Institute for Integrative Biology, Princeton University, Princeton, NJ, USA
| | - Megan N. McClean
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA
- Lewis-Sigler Institute for Integrative Biology, Princeton University, Princeton, NJ, USA
- University of Wisconsin Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| |
Collapse
|
5
|
A focus on yeast mating: From pheromone signaling to cell-cell fusion. Semin Cell Dev Biol 2023; 133:83-95. [PMID: 35148940 DOI: 10.1016/j.semcdb.2022.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 12/14/2022]
Abstract
Cells live in a chemical environment and are able to orient towards chemical cues. Unicellular haploid fungal cells communicate by secreting pheromones to reproduce sexually. In the yeast models Saccharomyces cerevisiae and Schizosaccharomyces pombe, pheromonal communication activates similar pathways composed of cognate G-protein-coupled receptors and downstream small GTPase Cdc42 and MAP kinase cascades. Local pheromone release and sensing, at a mobile surface polarity patch, underlie spatial gradient interpretation to form pairs between two cells of distinct mating types. Concentration of secretion at the point of cell-cell contact then leads to local cell wall digestion for cell fusion, forming a diploid zygote that prevents further fusion attempts. A number of asymmetries between mating types may promote efficiency of the system. In this review, we present our current knowledge of pheromone signaling in the two model yeasts, with an emphasis on how cells decode the pheromone signal spatially and ultimately fuse together. Though overall pathway architectures are similar in the two species, their large evolutionary distance allows to explore how conceptually similar solutions to a general biological problem can arise from divergent molecular components.
Collapse
|
6
|
The histone H2B Arg95 residue links the pheromone response pathway to rapamycin-induced G 1 arrest in yeast. Sci Rep 2022; 12:10023. [PMID: 35705668 PMCID: PMC9200821 DOI: 10.1038/s41598-022-14053-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/31/2022] [Indexed: 11/08/2022] Open
Abstract
Rapamycin is an immunosuppressant used for treating many types of diseases such as kidney carcinomas. In yeast, rapamycin inhibits the TORC1 kinase signaling pathway causing rapid alteration in gene expression and ultimately cell cycle arrest in G1 through mechanisms that are not fully understood. Herein, we screened a histone mutant collection and report that one of the mutants, H2B R95A, is strikingly resistant to rapamycin due to a defective cell cycle arrest. We show that the H2B R95A causes defects in the expression of a subset of genes of the pheromone pathway required for α factor-induced G1 arrest. The expression of the STE5 gene and its encoded scaffold protein Ste5, required for the sequential activation of the MAPKs of the pheromone pathway, is greatly reduced in the H2B R95A mutant. Similar to the H2B R95A mutant, cells devoid of Ste5 are also resistant to rapamycin. Rapamycin-induced G1 arrest does not involve detectable phosphorylation of the MAPKs, Kss1, and Fus3, as reported for α factor-induced G1 arrest. However, we observed a sharp induction of the G1 cyclin Cln2 (~ 3- to 4-fold) in the ste5Δ mutant within 30 min of exposure to rapamycin. Our data provide a new insight whereby rapamycin signaling via the Torc1 kinase may exploit the pheromone pathway to arrest cells in the G1 phase.
Collapse
|
7
|
Transcriptome Analysis Reveals that MAPK Signaling Pathway Mediates Salt Tolerance of YMR253C ORF in Saccharomyces cerevisiae. Curr Microbiol 2022; 79:126. [DOI: 10.1007/s00284-022-02818-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/18/2022] [Indexed: 11/03/2022]
|
8
|
González-Rubio G, Sellers-Moya Á, Martín H, Molina M. A walk-through MAPK structure and functionality with the 30-year-old yeast MAPK Slt2. Int Microbiol 2021; 24:531-543. [PMID: 33993419 DOI: 10.1007/s10123-021-00183-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/29/2021] [Accepted: 05/05/2021] [Indexed: 01/10/2023]
Abstract
Mitogen-activated protein kinases (MAPKs) are evolutionarily conserved signaling proteins involved in the regulation of most eukaryotic cellular processes. They are downstream components of essential signal transduction pathways activated by the external stimuli, in which the signal is conveyed through phosphorylation cascades. The excellent genetic and biochemical tractability of simple eukaryotes such as Saccharomyces cerevisiae has significantly contributed to gain fundamental information into the physiology of these key proteins. The budding yeast MAPK Slt2 was identified 30 years ago and was later revealed as a fundamental element of the cell wall integrity (CWI) pathway, one of the five MAPK routes of S. cerevisiae. As occurs with other MAPKs, whereas Slt2 displays the core typical structural traits of eukaryotic protein kinases, it also features conserved domains among MAPKs that allow an exquisite spatio-temporal regulation of their activity and binding to activating kinases, downregulatory phosphatases, or nuclear transcription factors. Additionally, Slt2 bears a regulatory extra C-terminal tail unique among S. cerevisiae MAPKs. Here, we review the structural and functional basis for the signaling role of Slt2 in the context of the molecular architecture of this important family of protein kinases.
Collapse
Affiliation(s)
- Gema González-Rubio
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Universidad Complutense de Madrid, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain
| | - Ángela Sellers-Moya
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Universidad Complutense de Madrid, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain
| | - Humberto Martín
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Universidad Complutense de Madrid, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain.
| | - María Molina
- Departamento de Microbiología y Parasitología, Facultad de Farmacia, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Universidad Complutense de Madrid, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain.
| |
Collapse
|
9
|
Differential Role of Threonine and Tyrosine Phosphorylation in the Activation and Activity of the Yeast MAPK Slt2. Int J Mol Sci 2021; 22:ijms22031110. [PMID: 33498635 PMCID: PMC7866135 DOI: 10.3390/ijms22031110] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 02/06/2023] Open
Abstract
The Mitogen-Activated Protein Kinase (MAPK) Slt2 is central to signaling through the yeast Cell Wall Integrity (CWI) pathway. MAPKs are regulated by phosphorylation at both the threonine and tyrosine of the conserved TXY motif within the activation loop (T190/Y192 in Slt2). Since phosphorylation at both sites results in the full activation of MAPKs, signaling through MAPK pathways is monitored with antibodies that detect dually phosphorylated forms. However, most of these antibodies also recognize monophosphorylated species, whose relative abundance and functionality are diverse. By using different phosphospecific antibodies and phosphate-affinity (Phos-tag) analysis on distinct Slt2 mutants, we determined that Y192- and T190-monophosphorylated species coexist with biphosphorylated Slt2, although most of the Slt2 pool remains unphosphorylated following stress. Among the monophosphorylated forms, only T190 exhibited biological activity. Upon stimulation, Slt2 is first phosphorylated at Y192, mainly by the MAPKK Mkk1, and this phosphorylation is important for the subsequent T190 phosphorylation. Similarly, dephosphorylation of Slt2 by the Dual Specificity Phosphatase (DSP) Msg5 is ordered, with dephosphorylation of T190 depending on previous Y192 dephosphorylation. Whereas Y192 phosphorylation enhances the Slt2 catalytic activity, T190 is essential for this activity. The conserved T195 residue is also critical for Slt2 functionality. Mutations that abolish the activity of Slt2 result in a high increase in inactive Y192-monophosphorylated Slt2. The coexistence of different Slt2 phosphoforms with diverse biological significance highlights the importance of the precise detection of the Slt2 phosphorylation status.
Collapse
|
10
|
Li X, Ye H, Xu CQ, Shen XL, Zhang XL, Huang C, Cheng B, Tan YL, Xiao ZT, Pei YP, Zou K. Transcriptomic analysis reveals MAPK signaling pathways affect the autolysis in baker's yeast. FEMS Yeast Res 2020; 20:5859490. [PMID: 32556321 DOI: 10.1093/femsyr/foaa036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 06/12/2020] [Indexed: 12/26/2022] Open
Abstract
Yeast autolysis refers to the process in which cells degrade and release intracellular contents under specific conditions by endogenous enzymes such as proteases, nucleases and lipid enzymes. Protein-rich baker's yeast is widely used to produce yeast extract in food industry, however, the molecular mechanism related to baker's yeast autolysis is still unclear. In this study, RNA-seq technology and biochemical analysis were performed to analyze the autolysis processes in baker's yeast. The differentially expressed genes (DEGs), 27 autolysis-related euKaryotic Ortholog Groups (KOG) and three types of autolysis-induced Gene Ontology (GO) were identified and analyzed in detail. A total of 143 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways under autolysis were also assigned. Interestingly, the DEGs were significantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathways and metabolic pathways, and key genes MID2, MTL1, SLT2, PTP2, HKR1 and GPD1 may play important roles in autolysis. Further quantitative PCR was performed to verify the expression pattern in baker's yeast autolysis. Together, all these results indicated that MAPK pathways might play an essential role during autolysis process through inhibiting the metabolism and disrupting cell wall in baker's yeast. This result may provide important clues for the in-depth interpretation of the yeast autolysis mechanism.
Collapse
Affiliation(s)
- Xiao Li
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China.,Hubei Provincial Key Laboratory of Yeast Function, Angel Yeast Company Limited, Yichang, Hubei 443003, China
| | - Han Ye
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Chao-Qun Xu
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Xiang-Ling Shen
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Xiao-Long Zhang
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Cong Huang
- Hubei Provincial Key Laboratory of Yeast Function, Angel Yeast Company Limited, Yichang, Hubei 443003, China
| | - Ben Cheng
- Hubei Provincial Key Laboratory of Yeast Function, Angel Yeast Company Limited, Yichang, Hubei 443003, China
| | - Ya-Li Tan
- Hubei Provincial Key Laboratory of Yeast Function, Angel Yeast Company Limited, Yichang, Hubei 443003, China
| | - Ze-Tao Xiao
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Yu-Peng Pei
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| | - Kun Zou
- China Light Industry Key Laboratory of Yeast Function, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China
| |
Collapse
|
11
|
Shellhammer JP, Pomeroy AE, Li Y, Dujmusic L, Elston TC, Hao N, Dohlman HG. Quantitative analysis of the yeast pheromone pathway. Yeast 2019; 36:495-518. [PMID: 31022772 DOI: 10.1002/yea.3395] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/10/2019] [Accepted: 04/16/2019] [Indexed: 01/04/2023] Open
Abstract
The pheromone response pathway of the yeast Saccharomyces cerevisiae is a well-established model for the study of G proteins and mitogen-activated protein kinase (MAPK) cascades. Our longstanding ability to combine sophisticated genetic approaches with established functional assays has provided a thorough understanding of signalling mechanisms and regulation. In this report, we compare new and established methods used to quantify pheromone-dependent MAPK phosphorylation, transcriptional induction, mating morphogenesis, and gradient tracking. These include both single-cell and population-based assays of activity. We describe several technical advances, provide example data for benchmark mutants, highlight important differences between newer and established methodologies, and compare the advantages and disadvantages of each as applied to the yeast model. Quantitative measurements of pathway activity have been used to develop mathematical models and reveal new regulatory mechanisms in yeast. It is our expectation that experimental and computational approaches developed in yeast may eventually be adapted to human systems biology and pharmacology.
Collapse
Affiliation(s)
- James P Shellhammer
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Amy E Pomeroy
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Yang Li
- Division of Biological Sciences, University of California San Diego, San Diego, CA, 92093, USA
| | - Lorena Dujmusic
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Timothy C Elston
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Nan Hao
- Division of Biological Sciences, University of California San Diego, San Diego, CA, 92093, USA
| | - Henrik G Dohlman
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| |
Collapse
|
12
|
Winters MJ, Pryciak PM. MAPK modulation of yeast pheromone signaling output and the role of phosphorylation sites in the scaffold protein Ste5. Mol Biol Cell 2019; 30:1037-1049. [PMID: 30726174 PMCID: PMC6589907 DOI: 10.1091/mbc.e18-12-0793] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) mediate numerous eukaryotic signaling responses. They also can modulate their own signaling output via positive or negative feedback loops. In the yeast pheromone response pathway, the MAPK Fus3 triggers negative feedback that dampens its own activity. One target of this feedback is Ste5, a scaffold protein that promotes Fus3 activation. Binding of Fus3 to a docking motif (D motif) in Ste5 causes signal dampening, which was proposed to involve a central cluster of phosphorylation sites in Ste5. Here, we reanalyzed the role of these central sites. Contrary to prior claims, phosphorylation-mimicking mutations at these sites did not impair signaling. Also, the hyperactive signaling previously observed when these sites were mutated to nonphosphorylatable residues arose from their replacement with valine residues and was not observed with other substitutes. Instead, a cluster of N-terminal sites in Ste5, not the central sites, is required for the rapid dampening of initial responses. Further results suggest that the role of the Fus3 D motif is most simply explained by a tethering effect that promotes Ste5 phosphorylation, rather than an allosteric effect proposed to regulate Fus3 activity. These findings substantially revise our understanding of how MAPK feedback attenuates scaffold-mediated signaling in this model pathway.
Collapse
Affiliation(s)
- Matthew J Winters
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Peter M Pryciak
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| |
Collapse
|