1
|
Kuo CY, Tay RJ, Lin HC, Juan SC, Vidal-Diez de Ulzurrun G, Chang YC, Hoki J, Schroeder FC, Hsueh YP. The nematode-trapping fungus Arthrobotrys oligospora detects prey pheromones via G protein-coupled receptors. Nat Microbiol 2024; 9:1738-1751. [PMID: 38649409 DOI: 10.1038/s41564-024-01679-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 03/20/2024] [Indexed: 04/25/2024]
Abstract
The ability to sense prey-derived cues is essential for predatory lifestyles. Under low-nutrient conditions, Arthrobotrys oligospora and other nematode-trapping fungi develop dedicated structures for nematode capture when exposed to nematode-derived cues, including a conserved family of pheromones, the ascarosides. A. oligospora senses ascarosides via conserved MAPK and cAMP-PKA pathways; however, the upstream receptors remain unknown. Here, using genomic, transcriptomic and functional analyses, we identified two families of G protein-coupled receptors (GPCRs) involved in sensing distinct nematode-derived cues. GPCRs homologous to yeast glucose receptors are required for ascaroside sensing, whereas Pth11-like GPCRs contribute to ascaroside-independent nematode sensing. Both GPCR classes activate conserved cAMP-PKA signalling to trigger trap development. This work demonstrates that predatory fungi use multiple GPCRs to sense several distinct nematode-derived cues for prey recognition and to enable a switch to a predatory lifestyle. Identification of these receptors reveals the molecular mechanisms of cross-kingdom communication via conserved pheromones also sensed by plants and animals.
Collapse
Affiliation(s)
- Chih-Yen Kuo
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Rebecca J Tay
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Hung-Che Lin
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Sheng-Chian Juan
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | | | - Yu-Chu Chang
- Department of Biochemistry and Molecular Cell Biology, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Jason Hoki
- Boyce Thompson Institute, Cornell University, Ithaca, NY, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA
| | - Frank C Schroeder
- Boyce Thompson Institute, Cornell University, Ithaca, NY, USA
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA
| | - Yen-Ping Hsueh
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan.
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
| |
Collapse
|
2
|
Role of the Heme Activator Protein Complex in the Sexual Development of Cryptococcus neoformans. mSphere 2022; 7:e0017022. [PMID: 35638350 PMCID: PMC9241503 DOI: 10.1128/msphere.00170-22] [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] [Indexed: 11/20/2022] Open
Abstract
The CCAAT-binding heme activator protein (HAP) complex, comprising the DNA-binding heterotrimeric complex Hap2/3/5 and transcriptional activation subunit HapX, is a key regulator of iron homeostasis, mitochondrial functions, and pathogenicity in Cryptococcus neoformans, which causes fatal meningoencephalitis. However, its role in the development of human fungal pathogens remains unclear. To elucidate the role of the HAP complex in C. neoformans development, we constructed hap2Δ, hap3Δ, hap5Δ, and hapXΔ mutants and their complemented congenic MATα H99 and MATa YL99a strains. The HAP complex plays a conserved role in iron utilization and stress responses in cells of both mating types. Deletion of any of the HAP complex components markedly enhances filamentation during bisexual mating. However, the Hap2/3/5 complex, but not HapX, is crucial in repressing pheromone production and cell fusion and is thus a critical repressor of sexual differentiation of C. neoformans. Interestingly, deletion of the heterotrimeric complex transcriptionally regulated both positive and negative regulators in the pheromone-responsive Cpk1 mitogen-activated protein kinase (MAPK) pathway. Chromatin immunoprecipitation-quantitative PCR analysis revealed that the HAP complex physically bound to the CCAAT motif of the CRG1 and GPA2 promoter regions. Notably, the HAP complex was differentially localized depending on the mating type in basal conditions; it was enriched in the nuclei of MATα cells but diffused in the cytoplasm of MATa cells. Interestingly, however, a portion of the HAP complex in both mating types relocalized to the cell membrane during mating. In conclusion, the Hap2/3/5 heterotrimeric complex and HapX play major and minor roles, respectively, in repressing the sexual development of C. neoformans in association with the Cpk1 MAPK pathway. IMPORTANCECryptococcus neoformans isolates are of two mating types: MATα strains, which are predominant, and MATa strains, isolated from the sub-Saharan African region, where cryptococcosis is most abundant and severe. Here, we demonstrated the function of the CCAAT-binding HAP complex (Hap2/3/5/X) as a transcriptional repressor of Cpk1 pathway-related genes in cells of both mating types. Deletion of any HAP complex component markedly enhanced filamentation without affecting normal sporulation. In particular, deletion of the DNA-binding HAP complex components (Hap2/3/5), but not HapX, markedly enhanced pheromone production and cell fusion efficiency, validating its repressive role in the early stage of mating in C. neoformans. The HAP complex regulates the expression of both negative and positive mating regulators and is thus crucial for the regulation of the Cpk1 MAPK pathway during mating. This study provides insights into the complex signaling networks governing the sexual differentiation of C. neoformans.
Collapse
|
3
|
Zhao Y, Lin X. Cryptococcus neoformans: Sex, morphogenesis, and virulence. INFECTION GENETICS AND EVOLUTION 2021; 89:104731. [PMID: 33497839 DOI: 10.1016/j.meegid.2021.104731] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 12/23/2022]
Abstract
Cryptococcus neoformans is a dimorphic fungus that causes lethal meningoencephalitis mainly in immunocompromised individuals. Different morphotypes enable this environmental fungus and opportunistic pathogen to adapt to different natural niches and exhibit different levels of pathogenicity in various hosts. It is well-recognized that C. neoformans undergoes bisexual or unisexual reproduction in vitro to generate genotypic, morphotypic, and phenotypic diversity, which augments its ability for adaptation. However, if and how sexual reproduction and the meiotic machinery exert any direct impact on the infection process is unclear. This review summarizes recent discoveries on the regulation of cryptococcal life cycle and morphogenesis, and how they impact cryptococcal pathogenicity. The potential role of the meiotic machinery on ploidy regulation during cryptococcal infection is also discussed. This review aims to stimulate further investigation on links between fungal morphogenesis, sexual reproduction, and virulence.
Collapse
Affiliation(s)
- Youbao Zhao
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan Province, PR China; Department of Microbiology, University of Georgia, Athens, GA 30602, USA.
| | - Xiaorong Lin
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA.
| |
Collapse
|
4
|
Wang Y, Wei X, Bian Z, Wei J, Xu JR. Coregulation of dimorphism and symbiosis by cyclic AMP signaling in the lichenized fungus Umbilicaria muhlenbergii. Proc Natl Acad Sci U S A 2020; 117:23847-23858. [PMID: 32873646 PMCID: PMC7519320 DOI: 10.1073/pnas.2005109117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Umbilicaria muhlenbergii is the only known dimorphic lichenized fungus that grows in the hyphal form in lichen thalli but as yeast cells in axenic cultures. However, the regulation of yeast-to-hypha transition and its relationship to the establishment of symbiosis are not clear. In this study, we show that nutrient limitation and hyperosmotic stress trigger the dimorphic change in U. muhlenbergii Contact with algal cells of its photobiont Trebouxia jamesii induced pseudohyphal growth. Treatments with the cAMP diphosphoesterase inhibitor IBMX (3-isobutyl-1-methylxanthine) induced pseudohyphal/hyphal growth and resulted in the differentiation of heavily melanized, lichen cortex-like structures in culture, indicating the role of cAMP signaling in regulating dimorphism. To confirm this observation, we identified and characterized two Gα subunits UmGPA2 and UmGPA3 Whereas deletion of UmGPA2 had only a minor effect on pseudohyphal growth, the ΔUmgpa3 mutant was defective in yeast-to-pseudohypha transition induced by hyperosmotic stress or T. jamesii cells. IBMX treatment suppressed the defect of ΔUmgpa3 in pseudohyphal growth. Transformants expressing the UmGPA3G45V or UmGPA3Q208L dominant active allele were enhanced in the yeast-to-pseudohypha transition and developed pseudohyphae under conditions noninducible to the wild type. Interestingly, T. jamesii cells in close contact with pseudohyphae of UmGPA3G45V and UmGPA3Q208L transformants often collapsed and died after coincubation for over 72 h, indicating that improperly regulated pseudohyphal growth due to dominant active mutations may disrupt the initial establishment of symbiotic interaction between the photobiont and mycobiont. Taken together, these results show that the cAMP-PKA pathway plays a critical role in regulating dimorphism and symbiosis in U. muhlenbergii.
Collapse
Affiliation(s)
- Yanyan Wang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, China
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907
| | - Xinli Wei
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, China
| | - Zhuyun Bian
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907
| | - Jiangchun Wei
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, China
| | - Jin-Rong Xu
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907
| |
Collapse
|
5
|
Liu KH, Shen WC. Sexual Differentiation Is Coordinately Regulated by Cryptococcus neoformans CRK1 and GAT1. Genes (Basel) 2020; 11:genes11060669. [PMID: 32575488 PMCID: PMC7349709 DOI: 10.3390/genes11060669] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/05/2020] [Accepted: 06/16/2020] [Indexed: 12/02/2022] Open
Abstract
The heterothallic basidiomycetous fungus Cryptococcus neoformans has two mating types, MATa and MATα. Morphological progression of bisexual reproduction in C. neoformans is as follows: yeast to hyphal transition, filament extension, basidium formation, meiosis, and sporulation. C. neoformans Cdk-related kinase 1 (CRK1) is a negative regulator of bisexual mating. In this study, we characterized the morphological features of mating structures in the crk1 mutant and determined the genetic interaction of CRK1 in the regulatory networks of sexual differentiation. In the bilateral crk1 mutant cross, despite shorter length of filaments than in the wild-type cross, dikaryotic filaments and other structures still remained intact during bisexual mating, but the timing of basidium formation was approximately 18 h earlier than in the cross between wild type strains. Furthermore, gene expression analyses revealed that CRK1 modulated the expression of genes involved in the progression of hyphal elongation, basidium formation, karyogamy and meiosis. Phenotypic results showed that, although deletion of C. neoformans CRK1 gene increased the efficiency of bisexual mating, filamentation in the crk1 mutant was blocked by MAT2 or ZNF2 mutation. A bioinformatics survey predicted the C. neoformans GATA transcriptional factor Gat1 as a potential substrate of Crk1 kinase. Our genetic and phenotypic findings revealed that C. neoformansGAT1 and CRK1 formed a regulatory circuit to negatively regulate MAT2 to control filamentation progression and transition during bisexual mating.
Collapse
|
6
|
Yang CT, Vidal-Diez de Ulzurrun G, Gonçalves AP, Lin HC, Chang CW, Huang TY, Chen SA, Lai CK, Tsai IJ, Schroeder FC, Stajich JE, Hsueh YP. Natural diversity in the predatory behavior facilitates the establishment of a robust model strain for nematode-trapping fungi. Proc Natl Acad Sci U S A 2020; 117:6762-6770. [PMID: 32161129 PMCID: PMC7104180 DOI: 10.1073/pnas.1919726117] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Nematode-trapping fungi (NTF) are a group of specialized microbial predators that consume nematodes when food sources are limited. Predation is initiated when conserved nematode ascaroside pheromones are sensed, followed by the development of complex trapping devices. To gain insights into the coevolution of this interkingdom predator-prey relationship, we investigated natural populations of nematodes and NTF that we found to be ubiquitous in soils. Arthrobotrys species were sympatric with various nematode species and behaved as generalist predators. The ability to sense prey among wild isolates of Arthrobotrys oligospora varied greatly, as determined by the number of traps after exposure to Caenorhabditis elegans While some strains were highly sensitive to C. elegans and the nematode pheromone ascarosides, others responded only weakly. Furthermore, strains that were highly sensitive to the nematode prey also developed traps faster. The polymorphic nature of trap formation correlated with competency in prey killing, as well as with the phylogeny of A. oligospora natural strains, calculated after assembly and annotation of the genomes of 20 isolates. A chromosome-level genome assembly and annotation were established for one of the most sensitive wild isolates, and deletion of the only G-protein β-subunit-encoding gene of A. oligospora nearly abolished trap formation. In summary, our study establishes a highly responsive A. oligospora wild isolate as a model strain for the study of fungus-nematode interactions and demonstrates that trap formation is a fitness character in generalist predators of the nematode-trapping fungus family.
Collapse
Affiliation(s)
- Ching-Ting Yang
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
| | | | - A Pedro Gonçalves
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Hung-Che Lin
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei 106, Taiwan
| | - Ching-Wen Chang
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 106, Taiwan
| | - Tsung-Yu Huang
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Sheng-An Chen
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Cheng-Kuo Lai
- Biodiversity Research Center, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Isheng J Tsai
- Biodiversity Research Center, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Frank C Schroeder
- Boyce Thompson Institute, Cornell University, Ithaca, NY 14853
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - Jason E Stajich
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521
| | - Yen-Ping Hsueh
- Institute of Molecular Biology, Academia Sinica, Nangang, Taipei 115, Taiwan;
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei 106, Taiwan
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 106, Taiwan
| |
Collapse
|
7
|
Maliehe M, Ntoi MA, Lahiri S, Folorunso OS, Ogundeji AO, Pohl CH, Sebolai OM. Environmental Factors That Contribute to the Maintenance of Cryptococcus neoformans Pathogenesis. Microorganisms 2020; 8:microorganisms8020180. [PMID: 32012843 PMCID: PMC7074686 DOI: 10.3390/microorganisms8020180] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/04/2019] [Accepted: 12/11/2019] [Indexed: 02/07/2023] Open
Abstract
The ability of microorganisms to colonise and display an intracellular lifestyle within a host body increases their fitness to survive and avoid extinction. This host–pathogen association drives microbial evolution, as such organisms are under selective pressure and can become more pathogenic. Some of these microorganisms can quickly spread through the environment via transmission. The non-transmittable fungal pathogens, such as Cryptococcus, probably return into the environment upon decomposition of the infected host. This review analyses whether re-entry of the pathogen into the environment causes restoration of its non-pathogenic state or whether environmental factors and parameters assist them in maintaining pathogenesis. Cryptococcus (C.) neoformans is therefore used as a model organism to evaluate the impact of environmental stress factors that aid the survival and pathogenesis of C. neoformans intracellularly and extracellularly.
Collapse
|
8
|
A Mechanosensitive Channel Governs Lipid Flippase-Mediated Echinocandin Resistance in Cryptococcus neoformans. mBio 2019; 10:mBio.01952-19. [PMID: 31822582 PMCID: PMC6904872 DOI: 10.1128/mbio.01952-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Echinocandins show fungicidal activity against common invasive mycoses but are ineffective against cryptococcosis. The underlying mechanism for echinocandin resistance in Cryptococcus neoformans remains poorly understood but has been shown to involve Cdc50, the regulatory subunit of lipid flippase. In a forward genetic screen for cdc50Δ suppressor mutations that are caspofungin resistant, we identified Crm1 (caspofungin resistant mutation 1), a homolog of mechanosensitive channel proteins, and showed that crm1Δ restored caspofungin resistance in cdc50Δ cells. Caspofungin-treated cdc50Δ cells exhibited abnormally high intracellular calcium levels ([Ca2+]c) and heightened activation of the calcineurin pathway. Deletion of CRM1 in the cdc50Δ background normalized the abnormally high [Ca2+]c. Cdc50 interacts with Crm1 to maintain cellular calcium homeostasis. Analysis of chitin/chitosan content showed that deleting CRM1 reversed the decreased chitosan production of cdc50Δ cells. Together, these results demonstrate that Cdc50 and Crm1 regulation of the calcineurin pathway and cytoplasmic calcium homeostasis may underlie caspofungin resistance in C. neoformans IMPORTANCE Cryptococcus neoformans is the leading cause of fungal meningitis, accounting for ∼15% of HIV/AIDS-related deaths, but treatment options for cryptococcosis are limited. Echinocandins are the newest fungicidal drug class introduced but are ineffective in treating cryptococcosis. Our previous study identified the lipid flippase subunit Cdc50 as a contributor to echinocandin resistance in C. neoformans Here, we further elucidated the mechanism of Cdc50-mediated caspofungin drug resistance. We discovered that Cdc50 interacts with the mechanosensitive calcium channel protein Crm1 to regulate calcium homeostasis and caspofungin resistance via calcium/calcineurin signaling. These results provide novel insights into echinocandin resistance in this pathogen, which may lead to new treatment options, as well as inform echinocandin resistance mechanisms in other fungal organisms and, hence, advance our understanding of modes of antifungal drug susceptibility and resistance.
Collapse
|
9
|
Unisexual reproduction promotes competition for mating partners in the global human fungal pathogen Cryptococcus deneoformans. PLoS Genet 2019; 15:e1008394. [PMID: 31536509 PMCID: PMC6772093 DOI: 10.1371/journal.pgen.1008394] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 10/01/2019] [Accepted: 08/29/2019] [Indexed: 12/22/2022] Open
Abstract
Courtship is pivotal for successful mating. However, courtship is challenging for the Cryptococcus neoformans species complex, comprised of opportunistic fungal pathogens, as the majority of isolates are α mating type. In the absence of mating partners of the opposite mating type, C. deneoformans can undergo unisexual reproduction, during which a yeast-to-hyphal morphological transition occurs. Hyphal growth during unisexual reproduction is a quantitative trait, which reflects a strain's ability to undergo unisexual reproduction. In this study, we determined whether unisexual reproduction confers an ecological benefit by promoting foraging for mating partners. Through competitive mating assays using strains with different abilities to produce hyphae, we showed that unisexual reproduction potential did not enhance competition for mating partners of the same mating type, but when cells of the opposite mating type were present, cells with enhanced hyphal growth were more competitive for mating partners of either the same or opposite mating type. Enhanced mating competition was also observed in a strain with increased hyphal production that lacks the mating repressor gene GPA3, which contributes to the pheromone response. Hyphal growth in unisexual strains also enables contact between adjacent colonies and enhances mating efficiency during mating confrontation assays. The pheromone response pathway activation positively correlated with unisexual reproduction hyphal growth during bisexual mating and exogenous pheromone promoted bisexual cell fusion. Despite the benefit in competing for mating partners, unisexual reproduction conferred a fitness cost. Taken together, these findings suggest C. deneoformans employs hyphal growth to facilitate contact between colonies at long distances and utilizes pheromone sensing to enhance mating competition.
Collapse
|
10
|
Abstract
Cryptococcus neoformans is a ubiquitous environmental fungus and an opportunistic pathogen that causes fatal cryptococcal meningitis. Advances in genomics, genetics, and cellular and molecular biology of C. neoformans have dramatically improved our understanding of this important pathogen, rendering it a model organism to study eukaryotic biology and microbial pathogenesis. In light of recent progress, we describe in this review the life cycle of C. neoformans with a special emphasis on the regulation of the yeast-to-hypha transition and different modes of sexual reproduction, in addition to the impacts of the life cycle on cryptococcal populations and pathogenesis.
Collapse
Affiliation(s)
- Youbao Zhao
- Department of Microbiology, University of Georgia, Athens, Georgia 30602; , , ,
| | - Jianfeng Lin
- Department of Microbiology, University of Georgia, Athens, Georgia 30602; , , ,
| | - Yumeng Fan
- Department of Microbiology, University of Georgia, Athens, Georgia 30602; , , ,
| | - Xiaorong Lin
- Department of Microbiology, University of Georgia, Athens, Georgia 30602; , , ,
| |
Collapse
|
11
|
Caza M, Kronstad JW. The cAMP/Protein Kinase a Pathway Regulates Virulence and Adaptation to Host Conditions in Cryptococcus neoformans. Front Cell Infect Microbiol 2019; 9:212. [PMID: 31275865 PMCID: PMC6592070 DOI: 10.3389/fcimb.2019.00212] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 05/31/2019] [Indexed: 12/28/2022] Open
Abstract
Nutrient sensing is critical for adaptation of fungi to environmental and host conditions. The conserved cAMP/PKA signaling pathway contributes to adaptation by sensing the availability of key nutrients such as glucose and directing changes in gene expression and metabolism. Interestingly, the cAMP/PKA pathway in fungal pathogens also influences the expression of virulence determinants in response to nutritional and host signals. For instance, protein kinase A (PKA) in the human pathogen Cryptococcus neoformans plays a central role in orchestrating phenotypic changes, such as capsule elaboration and melanin production, that directly impact disease development. In this review, we focus first on insights into the role of the cAMP/PKA pathway in nutrient sensing for the model yeast Saccharomyces cerevisiae to provide a foundation for understanding the pathway in C. neoformans. We then discuss key features of cAMP/PKA signaling in C. neoformans including new insights emerging from the analysis of transcriptional and proteomic changes in strains with altered PKA activity and expression. Finally, we highlight recent studies that connect the cAMP/PKA pathway to cell surface remodeling and the formation of titan cells.
Collapse
Affiliation(s)
- Mélissa Caza
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - James W Kronstad
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
12
|
Yang X, Al-Attala MN, Zhang Y, Zhang AF, Zang HY, Gu CY, Gao TC, Chen Y, Al-Attala MN, Ali F, Li YF, Yao J, Zhu JG. Rapid Detection of Ustilaginoidea virens from Rice using Loop-Mediated Isothermal Amplification Assay. PLANT DISEASE 2018; 102:1741-1747. [PMID: 30125168 DOI: 10.1094/pdis-01-18-0065-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Ustilaginoidea virens is an important fungus that causes rice false smut disease. This disease significantly reduces both grain yield and quality. Various methods have been developed for the detection of U. virens but most of these methods need sophisticated equipment such as a thermal cycler. Here, we present a loop-mediated isothermal amplification (LAMP) assay for the specific detection of U. virens. This assay used a specific region of the UvG-β1 gene (212-bp region) to design six LAMP primers. The LAMP assay was optimized by the combination of rapidity, simplicity, and high sensitivity for the detection of about 1 pg of target genomic DNA in the reaction whereas, with polymerase chain reaction (PCR), there was no amplification of DNA with concentrations less than 1 ng. Among the genomic DNA of 22 fungus species and two strains of U. virens, only the tube containing the DNA of U. virens changed to yellowish green with SYBR Green I. The color change was indicative of DNA amplification. No DNA was amplified from either the other 22 fungus species or the negative control. Moreover, 20 spikelets and 22 rice seed samples were used for the detection of rice false smut via LAMP. The results were comparable with conventional PCR. We conclude that gene UvG-β1 coupled with LAMP assay, can be used for the detection and identification of U. virens gene via LAMP.
Collapse
Affiliation(s)
- Xue Yang
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Mohamed N Al-Attala
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Yong Zhang
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Ai-Fang Zhang
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Hao-Yu Zang
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Chun-Yan Gu
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Tong-Chun Gao
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Yu Chen
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, China; and Laboratory of Quality & Safety Risk Assessment for Agro-Products, Hefei, Ministry of Agriculture, China; and Key Laboratory of Anhui Agricultural Sciences
| | - Mohamed N Al-Attala
- Plant Pathology Unit, Plant Protection Department, Desert Research Center, Cairo 11753, Egypt
| | - Farman Ali
- Institute of Plant Protection and Agro-products Safety, Anhui Academy of Agricultural Sciences; and Department of Agriculture, Abdul Wali Khan University Mardan, Pakistan
| | - Yun-Fei Li
- Anhui Entry-Exit Inspection and Quarantine Bureau, Hefei 230022, China
| | - Jian Yao
- Anhui Entry-Exit Inspection and Quarantine Bureau, Hefei 230022, China
| | - Jin-Guo Zhu
- Hunan Entry-Exit Inspection and Quarantine Bureau, Changsha 410004, China
| |
Collapse
|
13
|
Cryptococcus neoformans sexual reproduction is controlled by a quorum sensing peptide. Nat Microbiol 2018; 3:698-707. [PMID: 29784977 DOI: 10.1038/s41564-018-0160-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 04/16/2018] [Indexed: 12/13/2022]
Abstract
Bacterial quorum sensing is a well-characterized communication system that governs a large variety of collective behaviours. By comparison, quorum sensing regulation in eukaryotic microbes remains poorly understood, especially its functional role in eukaryote-specific behaviours, such as sexual reproduction. Cryptococcus neoformans is a prevalent fungal pathogen that has two defined sexual cycles (bisexual and unisexual) and is a model organism for studying sexual reproduction in fungi. Here, we show that the quorum sensing peptide Qsp1 serves as an important signalling molecule for both forms of sexual reproduction. Qsp1 orchestrates various differentiation and molecular processes, including meiosis, the hallmark of sexual reproduction. It activates bisexual mating, at least in part through the control of pheromone, a signal necessary for bisexual activation. Notably, Qsp1 also plays a major role in the intercellular regulation of unisexual initiation and coordination, in which pheromone is not strictly required. Through a multi-layered genetic screening approach, we identified the atypical zinc finger regulator Cqs2 as an important component of the Qsp1 signalling cascade during both bisexual and unisexual reproduction. The absence of Cqs2 eliminates the Qsp1-stimulated mating response. Together, these findings extend the range of behaviours governed by quorum sensing to sexual development and meiosis.
Collapse
|
14
|
Fu C, Heitman J. PRM1 and KAR5 function in cell-cell fusion and karyogamy to drive distinct bisexual and unisexual cycles in the Cryptococcus pathogenic species complex. PLoS Genet 2017; 13:e1007113. [PMID: 29176784 PMCID: PMC5720818 DOI: 10.1371/journal.pgen.1007113] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 12/07/2017] [Accepted: 11/13/2017] [Indexed: 11/18/2022] Open
Abstract
Sexual reproduction is critical for successful evolution of eukaryotic organisms in adaptation to changing environments. In the opportunistic human fungal pathogens, the Cryptococcus pathogenic species complex, C. neoformans primarily undergoes bisexual reproduction, while C. deneoformans undergoes both unisexual and bisexual reproduction. During both unisexual and bisexual cycles, a common set of genetic circuits regulates a yeast-to-hyphal morphological transition, that produces either monokaryotic or dikaryotic hyphae. As such, both the unisexual and bisexual cycles can generate genotypic and phenotypic diversity de novo. Despite the similarities between these two cycles, genetic and morphological differences exist, such as the absence of an opposite mating-type partner and monokaryotic instead of dikaryotic hyphae during C. deneoformans unisexual cycle. To better understand the similarities and differences between these modes of sexual reproduction, we focused on two cellular processes involved in sexual reproduction: cell-cell fusion and karyogamy. We identified orthologs of the plasma membrane fusion protein Prm1 and the nuclear membrane fusion protein Kar5 in both Cryptococcus species, and demonstrated their conserved roles in cell fusion and karyogamy during C. deneoformans α-α unisexual reproduction and C. deneoformans and C. neoformans a-α bisexual reproduction. Notably, karyogamy occurs inside the basidum during bisexual reproduction in C. neoformans, but often occurs earlier following cell fusion during bisexual reproduction in C. deneoformans. Characterization of these two genes also showed that cell fusion is dispensable for solo unisexual reproduction in C. deneoformans. The blastospores produced along hyphae during C. deneoformans unisexual reproduction are diploid, suggesting that diploidization occurs early during hyphal development, possibly through either an endoreplication pathway or cell fusion-independent karyogamy events. Taken together, our findings suggest distinct mating mechanisms for unisexual and bisexual reproduction in Cryptococcus, exemplifying distinct evolutionary trajectories within this pathogenic species complex.
Collapse
Affiliation(s)
- Ci Fu
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States of America
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, United States of America
- * E-mail:
| |
Collapse
|
15
|
Xu X, Lin J, Zhao Y, Kirkman E, So YS, Bahn YS, Lin X. Glucosamine stimulates pheromone-independent dimorphic transition in Cryptococcus neoformans by promoting Crz1 nuclear translocation. PLoS Genet 2017; 13:e1006982. [PMID: 28898238 PMCID: PMC5595294 DOI: 10.1371/journal.pgen.1006982] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 08/17/2017] [Indexed: 02/06/2023] Open
Abstract
Morphotype switch is a cellular response to external and internal cues. The Cryptococcus neoformans species complex can undergo morphological transitions between the yeast and the hypha form, and such morphological changes profoundly affect cryptococcal interaction with various hosts. Filamentation in Cryptococcus was historically considered a mating response towards pheromone. Recent studies indicate the existence of pheromone-independent signaling pathways but their identity or the effectors remain unknown. Here, we demonstrated that glucosamine stimulated the C. neoformans species complex to undergo self-filamentation. Glucosamine-stimulated filamentation was independent of the key components of the pheromone pathway, which is distinct from pheromone-elicited filamentation. Glucosamine stimulated self-filamentation in H99, a highly virulent serotype A clinical isolate and a widely used reference strain. Through a genetic screen of the deletion sets made in the H99 background, we found that Crz1, a transcription factor downstream of calcineurin, was essential for glucosamine-stimulated filamentation despite its dispensability for pheromone-mediated filamentation. Glucosamine promoted Crz1 translocation from the cytoplasm to the nucleus. Interestingly, multiple components of the high osmolality glycerol response (HOG) pathway, consisting of the phosphorelay system and some of the Hog1 MAPK module, acted as repressors of glucosamine-elicited filamentation through their calcineurin-opposing effect on Crz1’s nuclear translocation. Surprisingly, glucosamine-stimulated filamentation did not require Hog1 itself and was distinct from the conventional general stress response. The results demonstrate that Cryptococcus can resort to multiple genetic pathways for morphological transition in response to different stimuli. Given that the filamentous form attenuates cryptococcal virulence and is immune-stimulatory in mammalian models, the findings suggest that morphogenesis is a fertile ground for future investigation into novel means to compromise cryptococcal pathogenesis. Cryptococcal meningitis claims half a million lives each year. There is no clinically available vaccine and the current antifungal therapies have serious limitations. Thus identifying cryptococcal specific programs that can be targeted for antifungal or vaccine development is of great value. We have shown previously that switching from the yeast to the hypha form drastically attenuates/abolishes cryptococcal virulence. Cryptococcal cells in the filamentous form also trigger host immune responses that can protect the host from a subsequent lethal challenge. However, self-filamentation is rarely observed in serotype A isolates that are responsible for the vast majority of cryptococcosis cases. In this study, we found that glucosamine stimulated self-filamentation in genetically distinct strains of the Cryptococcus species complex, including the most commonly used serotype A reference strain H99. We demonstrated that filamentation elicited by glucosamine did not depend on the pheromone pathway, but it requires the calcineurin transcription factor Crz1. Glucosamine promotes nuclear translocation of Crz1, which is positively controlled by the phosphatase calcineurin and is suppressed by the HOG pathway. These findings raise the possibility of manipulating genetic pathways controlling fungal morphogenesis against diseases caused by the Cryptococcus species complex.
Collapse
Affiliation(s)
- Xinping Xu
- Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail: (XL); (XX)
| | - Jianfeng Lin
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
| | - Youbao Zhao
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
| | - Elyssa Kirkman
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Yee-Seul So
- Department of Biotechnology, Yonsei University, Seoul, Korea
| | - Yong-Sun Bahn
- Department of Biotechnology, Yonsei University, Seoul, Korea
| | - Xiaorong Lin
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Department of Microbiology, University of Georgia, Athens, Georgia, United States of America
- * E-mail: (XL); (XX)
| |
Collapse
|
16
|
Moretti M, Wang L, Grognet P, Lanver D, Link H, Kahmann R. Three regulators of G protein signaling differentially affect mating, morphology and virulence in the smut fungusUstilago maydis. Mol Microbiol 2017; 105:901-921. [DOI: 10.1111/mmi.13745] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2017] [Indexed: 12/30/2022]
Affiliation(s)
- Marino Moretti
- Department of Organismic Interactions; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10, Marburg D-35043 Germany
| | - Lei Wang
- Department of Organismic Interactions; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10, Marburg D-35043 Germany
| | - Pierre Grognet
- Department of Organismic Interactions; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10, Marburg D-35043 Germany
| | - Daniel Lanver
- Department of Organismic Interactions; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10, Marburg D-35043 Germany
| | - Hannes Link
- Dynamic Control of Metabolic Networks; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 16, Marburg D-35043 Germany
| | - Regine Kahmann
- Department of Organismic Interactions; Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10, Marburg D-35043 Germany
| |
Collapse
|
17
|
Bruni GO, Battle B, Kelly B, Zhang Z, Wang P. Comparative proteomic analysis of Gib2 validating its adaptor function in Cryptococcus neoformans. PLoS One 2017; 12:e0180243. [PMID: 28686685 PMCID: PMC5501510 DOI: 10.1371/journal.pone.0180243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 06/12/2017] [Indexed: 01/09/2023] Open
Abstract
Cryptococcus neoformans causes often-fatal fungal meningoencephalitis in immunocompromised individuals. While the exact disease mechanisms remain elusive, signal transduction pathways mediated by key elements such as G-protein α subunit Gpa1, small GTPase Ras1, and atypical Gβ-like/RACK1 protein Gib2 are known to play important roles in C. neoformans virulence. Gib2 is important for normal growth, differentiation, and pathogenicity, and it also positively regulates cAMP levels in conjunction with Gpa1. Interestingly, Gib2 displays a scaffold protein property by interacting with a wide variety of cellular proteins. To explore Gib2 global regulatory functions, we performed two-dimensional differential gel electrophoresis (DIGE) analysis and found that GIB2 disruption results in an increased expression of 304 protein spots (43.4%) and a decreased expression of 396 protein spots (56.6%). Analysis of 96 proteins whose expression changes were deemed significant (≥ +/- 1.5- fold) revealed that 75 proteins belong to at least 12 functional protein groups. Among them, eight groups have the statistical stringency of p ≤ 0.05, and four groups, including Hsp70/71 heat shock protein homologs and ribosomal proteins, survived the Bonferroni correction. This finding is consistent with earlier established roles for the human Gβ-like/RACK1 and the budding yeast Saccharomyces cerevisiae Asc1. It suggests that Gib2 could also be part of the complex affecting ribosomal biogenesis and protein translation in C. neoformans. Since eukaryotic Hsp70/71 proteins are involved in the facilitation of nascent protein folding, processing, and protection of cells against stress, we also propose that Gib2-regulated stress responses are linked to fungal virulence. Collectively, our study supports a conserved role of Gβ-like/RACK/Gib2 proteins in the essential cellular process of ribosomal biogenesis and protein translation. Our study also highlights a multifaceted regulatory role of Gib2 in the growth and pathogenicity of C. neoformans.
Collapse
Affiliation(s)
- Gillian O Bruni
- Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA, United States of America
| | - Blake Battle
- College of Arts and Sciences, Loyola University New Orleans, New Orleans, LA, United States of America
| | - Ben Kelly
- Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA, United States of America
| | - Zhengguang Zhang
- Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Ping Wang
- Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA, United States of America.,Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA, United States of America
| |
Collapse
|
18
|
Gyawali R, Zhao Y, Lin J, Fan Y, Xu X, Upadhyay S, Lin X. Pheromone independent unisexual development in Cryptococcus neoformans. PLoS Genet 2017; 13:e1006772. [PMID: 28467481 PMCID: PMC5435349 DOI: 10.1371/journal.pgen.1006772] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 05/17/2017] [Accepted: 04/20/2017] [Indexed: 11/24/2022] Open
Abstract
The fungus Cryptococcus neoformans can undergo a-α bisexual and unisexual reproduction. Completion of both sexual reproduction modes requires similar cellular differentiation processes and meiosis. Although bisexual reproduction generates equal number of a and α progeny and is far more efficient than unisexual reproduction under mating-inducing laboratory conditions, the α mating type dominates in nature. Population genetic studies suggest that unisexual reproduction by α isolates might have contributed to this sharply skewed distribution of the mating types. However, the predominance of the α mating type and the seemingly inefficient unisexual reproduction observed under laboratory conditions present a conundrum. Here, we discovered a previously unrecognized condition that promotes unisexual reproduction while suppressing bisexual reproduction. Pheromone is the principal stimulus for bisexual development in Cryptococcus. Interestingly, pheromone and other components of the pheromone pathway, including the key transcription factor Mat2, are not necessary but rather inhibitory for Cryptococcus to complete its unisexual cycle under this condition. The inactivation of the pheromone pathway promotes unisexual reproduction despite the essential role of this pathway in non-self-recognition during bisexual reproduction. Nonetheless, the requirement for the known filamentation regulator Znf2 and the expression of hyphal or basidium specific proteins remain the same for pheromone-dependent or independent sexual reproduction. Transcriptome analyses and an insertional mutagenesis screen in mat2Δ identified calcineurin being essential for this process. We further found that Znf2 and calcineurin work cooperatively in controlling unisexual development in this fungus. These findings indicate that Mat2 acts as a repressor of pheromone-independent unisexual development while serving as an activator for a-α bisexual development. The bi-functionality of Mat2 might have allowed it to act as a toggle switch for the mode of sexual development in this ubiquitous eukaryotic microbe.
Collapse
Affiliation(s)
- Rachana Gyawali
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Youbao Zhao
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Jianfeng Lin
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Yumeng Fan
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Xinping Xu
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Srijana Upadhyay
- Department of Biology, Texas A&M University, College Station, United States of America
| | - Xiaorong Lin
- Department of Biology, Texas A&M University, College Station, United States of America
| |
Collapse
|
19
|
Kelliher CM, Haase SB. Connecting virulence pathways to cell-cycle progression in the fungal pathogen Cryptococcus neoformans. Curr Genet 2017; 63:803-811. [PMID: 28265742 PMCID: PMC5605583 DOI: 10.1007/s00294-017-0688-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 02/22/2017] [Accepted: 02/22/2017] [Indexed: 11/01/2022]
Abstract
Proliferation and host evasion are critical processes to understand at a basic biological level for improving infectious disease treatment options. The human fungal pathogen Cryptococcus neoformans causes fungal meningitis in immunocompromised individuals by proliferating in cerebrospinal fluid. Current antifungal drugs target "virulence factors" for disease, such as components of the cell wall and polysaccharide capsule in C. neoformans. However, mechanistic links between virulence pathways and the cell cycle are not as well studied. Recently, cell-cycle synchronized C. neoformans cells were profiled over time to identify gene expression dynamics (Kelliher et al., PLoS Genet 12(12):e1006453, 2016). Almost 20% of all genes in the C. neoformans genome were periodically activated during the cell cycle in rich media, including 40 genes that have previously been implicated in virulence pathways. Here, we review important findings about cell-cycle-regulated genes in C. neoformans and provide two examples of virulence pathways-chitin synthesis and G-protein coupled receptor signaling-with their putative connections to cell division. We propose that a "comparative functional genomics" approach, leveraging gene expression timing during the cell cycle, orthology to genes in other fungal species, and previous experimental findings, can lead to mechanistic hypotheses connecting the cell cycle to fungal virulence.
Collapse
Affiliation(s)
- Christina M Kelliher
- Department of Biology, Duke University, Box 90338, 130 Science Drive, Durham, NC, 27708-0338, USA
| | - Steven B Haase
- Department of Biology, Duke University, Box 90338, 130 Science Drive, Durham, NC, 27708-0338, USA.
| |
Collapse
|
20
|
Valle-Maldonado MI, Jácome-Galarza IE, Díaz-Pérez AL, Martínez-Cadena G, Campos-García J, Ramírez-Díaz MI, Reyes-De la Cruz H, Riveros-Rosas H, Díaz-Pérez C, Meza-Carmen V. Phylogenetic analysis of fungal heterotrimeric G protein-encoding genes and their expression during dimorphism in Mucor circinelloides. Fungal Biol 2015; 119:1179-1193. [DOI: 10.1016/j.funbio.2015.08.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 08/08/2015] [Accepted: 08/10/2015] [Indexed: 01/27/2023]
|
21
|
Choi J, Jung WH, Kronstad JW. The cAMP/protein kinase A signaling pathway in pathogenic basidiomycete fungi: Connections with iron homeostasis. J Microbiol 2015; 53:579-87. [PMID: 26231374 DOI: 10.1007/s12275-015-5247-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 07/03/2015] [Accepted: 07/03/2015] [Indexed: 12/26/2022]
Abstract
A number of pathogenic species of basidiomycete fungi are either life-threatening pathogens of humans or major economic pests for crop production. Sensing the host is a key aspect of pathogen proliferation during disease, and signal transduction pathways are critically important for detecting environmental conditions and facilitating adaptation. This review focuses on the contributions of the cAMP/protein kinase A (PKA) signaling pathway in Cryptococcus neoformans, a species that causes meningitis in humans, and Ustilago maydis, a model phytopathogen that causes a smut disease on maize. Environmental sensing by the cAMP/PKA pathway regulates the production of key virulence traits in C. neoformans including the polysaccharide capsule and melanin. For U. maydis, the pathway controls the dimorphic transition from budding growth to the filamentous cell type required for proliferation in plant tissue. We discuss recent advances in identifying new components of the cAMP/PKA pathway in these pathogens and highlight an emerging theme that pathway signaling influences iron acquisition.
Collapse
Affiliation(s)
- Jaehyuk Choi
- Division of Life Sciences, and Culture Collection and DNA Bank of Mushrooms, Incheon National University, Incheon, 406-772, Republic of Korea
| | | | | |
Collapse
|
22
|
Fu C, Sun S, Billmyre RB, Roach KC, Heitman J. Unisexual versus bisexual mating in Cryptococcus neoformans: Consequences and biological impacts. Fungal Genet Biol 2015; 78:65-75. [PMID: 25173822 PMCID: PMC4344436 DOI: 10.1016/j.fgb.2014.08.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 08/14/2014] [Indexed: 11/22/2022]
Abstract
Cryptococcus neoformans is an opportunistic human fungal pathogen and can undergo both bisexual and unisexual mating. Despite the fact that one mating type is dispensable for unisexual mating, the two sexual cycles share surprisingly similar features. Both mating cycles are affected by similar environmental factors and regulated by the same pheromone response pathway. Recombination takes place during unisexual reproduction in a fashion similar to bisexual reproduction and can both admix pre-existing genetic diversity and also generate diversity de novo just like bisexual reproduction. These common features may allow the unisexual life cycle to provide phenotypic and genotypic plasticity for the natural Cryptococcus population, which is predominantly α mating type, and to avoid Muller's ratchet. The morphological transition from yeast to hyphal growth during both bisexual and unisexual mating may provide increased opportunities for outcrossing and the ability to forage for nutrients at a distance. The unisexual life cycle is a key evolutionary factor for Cryptococcus as a highly successful global fungal pathogen.
Collapse
Affiliation(s)
- Ci Fu
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - R B Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Kevin C Roach
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
| |
Collapse
|
23
|
Ost KS, O’Meara TR, Huda N, Esher SK, Alspaugh JA. The Cryptococcus neoformans alkaline response pathway: identification of a novel rim pathway activator. PLoS Genet 2015; 11:e1005159. [PMID: 25859664 PMCID: PMC4393102 DOI: 10.1371/journal.pgen.1005159] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 03/19/2015] [Indexed: 12/28/2022] Open
Abstract
The Rim101/PacC transcription factor acts in a fungal-specific signaling pathway responsible for sensing extracellular pH signals. First characterized in ascomycete fungi such as Aspergillus nidulans and Saccharomyces cerevisiae, the Rim/Pal pathway maintains conserved features among very distantly related fungi, where it coordinates cellular adaptation to alkaline pH signals and micronutrient deprivation. However, it also directs species-specific functions in fungal pathogens such as Cryptococcus neoformans, where it controls surface capsule expression. Moreover, disruption of the Rim pathway central transcription factor, Rim101, results in a strain that causes a hyper-inflammatory response in animal infection models. Using targeted gene deletions, we demonstrate that several genes encoding components of the classical Rim/Pal pathway are present in the C. neoformans genome. Many of these genes are in fact required for Rim101 activation, including members of the ESCRT complex (Vps23 and Snf7), ESCRT-interacting proteins (Rim20 and Rim23), and the predicted Rim13 protease. We demonstrate that in neutral/alkaline pH, Rim23 is recruited to punctate regions on the plasma membrane. This change in Rim23 localization requires upstream ESCRT complex components but does not require other Rim101 proteolysis components, such as Rim20 or Rim13. Using a forward genetics screen, we identified the RRA1 gene encoding a novel membrane protein that is also required for Rim101 protein activation and, like the ESCRT complex, is functionally upstream of Rim23-membrane localization. Homologs of RRA1 are present in other Cryptococcus species as well as other basidiomycetes, but closely related genes are not present in ascomycetes. These findings suggest that major branches of the fungal Kingdom developed different mechanisms to sense and respond to very elemental extracellular signals such as changing pH levels.
Collapse
Affiliation(s)
- Kyla S. Ost
- Departments of Medicine/ Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Teresa R. O’Meara
- Departments of Medicine/ Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Naureen Huda
- Departments of Medicine/ Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Shannon K. Esher
- Departments of Medicine/ Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - J. Andrew Alspaugh
- Departments of Medicine/ Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
24
|
Crystal structure of Gib2, a signal-transducing protein scaffold associated with ribosomes in Cryptococcus neoformans. Sci Rep 2015; 5:8688. [PMID: 25732347 PMCID: PMC4894404 DOI: 10.1038/srep08688] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/27/2015] [Indexed: 11/16/2022] Open
Abstract
The atypical Gβ-like/RACK1 Gib2 protein promotes cAMP signalling that plays a central role in regulating the virulence of Cryptococcus neoformans. Gib2 contains a seven-bladed β transducin structure and is emerging as a scaffold protein interconnecting signalling pathways through interactions with various protein partners. Here, we present the crystal structure of Gib2 at a 2.2-Å resolution. The structure allows us to analyse the association between Gib2 and the ribosome, as well as to identify the Gib2 amino acid residues involved in ribosome binding. Our studies not only suggest that Gib2 has a role in protein translation but also present Gib2 as a physical link at the crossroads of various regulatory pathways important for the growth and virulence of C. neoformans.
Collapse
|
25
|
Abstract
Cryptococcus gattii is a basidiomycetous human fungal pathogen that typically causes infection in tropical and subtropical regions and is responsible for an ongoing outbreak in immunocompetent individuals on Vancouver Island and in the Pacific Northwest of the US. Pathogenesis of this species may be linked to its sexual cycle that generates infectious propagules called basidiospores. A marked predominance of only one mating type (α) in clinical and environmental isolates suggests that a-α opposite-sex reproduction may be infrequent or geographically restricted, raising the possibility of an alternative unisexual cycle involving cells of only α mating type, as discovered previously in the related pathogenic species Cryptococcus neoformans. Here we report observation of hallmark features of unisexual reproduction in a clinical isolate of C. gattii (isolate 97/433) and describe genetic and environmental factors conducive to this sexual cycle. Our results are consistent with population genetic evidence of recombination in the largely unisexual populations of C. gattii and provide a useful genetic model for understanding how novel modes of sexual reproduction may contribute to evolution and virulence in this species.
Collapse
|
26
|
A Ric8/synembryn homolog promotes Gpa1 and Gpa2 activation to respectively regulate cyclic AMP and pheromone signaling in Cryptococcus neoformans. EUKARYOTIC CELL 2014; 13:1290-9. [PMID: 25084863 DOI: 10.1128/ec.00109-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The G protein α subunits Gpa1, Gpa2, and Gpa3 mediate signal transduction and are important in the growth and virulence of Cryptococcus neoformans. To understand how Gpa1 functions without a conventional Gβ subunit, we characterized a resistance to inhibitors of cholinesterase 8 (Ric8) homolog from C. neoformans, which shares amino acid sequence homology with other Ric8 proteins that exhibit guanine nucleotide exchange factor (GEF) activity toward Gα. We found that the ric8 mutant was reduced in capsule size and melanin formation, which could be suppressed by cyclic AMP (cAMP) supplementation or by introducing the activated GPA1(Q284L) allele. Consistent with the fact that Ric8 participates in cAMP signaling to regulate virulence, the ric8 mutant was attenuated in virulence toward mice. Interestingly, disruption of RIC8 also resulted in opposing effects on pheromone signaling, as the ric8 mutant showed reduced mating but an enhanced ability to induce the pheromone response in the mating partner. To identify Ric8 functional mechanisms, we examined the interactions between Ric8 and the three Gα proteins. Ric8 interacted with Gpa1 and Gpa2, but not Gpa3. The presence of Gpa1(Q284L) negatively affected its interaction with Ric8, whereas the activated Gpa2(Q203L) allele abolished the interaction. Collectively, these findings suggest that Ric8 functions as a GEF to facilitate the activation of Gpa1-cAMP signaling and to promote Gpa2, affecting mating efficiency. Our study highlights the distinct and conserved characteristics associated with G protein signaling and contributes to our overall understanding of how G protein α subunits function with or without a canonical Gβ partner in C. neoformans.
Collapse
|
27
|
Wang Y, Shen G, Gong J, Shen D, Whittington A, Qing J, Treloar J, Boisvert S, Zhang Z, Yang C, Wang P. Noncanonical Gβ Gib2 is a scaffolding protein promoting cAMP signaling through functions of Ras1 and Cac1 proteins in Cryptococcus neoformans. J Biol Chem 2014; 289:12202-16. [PMID: 24659785 DOI: 10.1074/jbc.m113.537183] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Gβ-like/RACK1 functions as a key mediator of various pathways and contributes to numerous cellular functions in eukaryotic organisms. In the pathogenic fungus Cryptococcus neoformans, noncanonical Gβ Gib2 promotes cAMP signaling in cells lacking normal Gpa1 function while displaying versatility in interactions with Gα Gpa1, protein kinase Pkc1, and endocytic intersectin Cin1. To elucidate the Gib2 functional mechanism(s), we demonstrate that Gib2 is required for normal growth and virulence. We show that Gib2 directly binds to Gpa1 and Gγ Gpg1/Gpg2 and that it interacts with phosphodiesterase Pde2 and monomeric GTPase Ras1. Pde2 remains functionally dispensable, but Ras1 is found to associate with adenylyl cyclase Cac1 through the conserved Ras association domain. In addition, the ras1 mutant exhibits normal capsule formation, whereas the ras1 gpa1 mutant displays enhanced capsule formation, and the ras1 gpa1 cac1 mutant is acapsular. Collectively, these findings suggest that Gib2 promotes cAMP levels by relieving an inhibitory function of Ras1 on Cac1 in the absence of Gpa1. In addition, using GST affinity purification combined with mass spectrometry, we identified 47 additional proteins that interact with Gib2. These proteins have putative functions ranging from signal transduction, energy generation, metabolism, and stress response to ribosomal function. After establishing and validating a protein-protein interactive network, we believe Gib2 to be a key adaptor/scaffolding protein that drives the formation of various protein complexes required for growth and virulence. Our study reveals Gib2 as an essential component in deciphering the complexity of regulatory networks that control growth and virulence in C. neoformans.
Collapse
Affiliation(s)
- Yanli Wang
- From the Research Institute for Children, Children's Hospital, New Orleans, Louisiana 70118
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Ste18p is a positive control element in the mating process of Candida albicans. EUKARYOTIC CELL 2014; 13:461-9. [PMID: 24489040 DOI: 10.1128/ec.00320-13] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Heterotrimeric G proteins are an important class of eukaryotic signaling molecules that have been identified as central elements in the pheromone response pathways of many fungi. In the fungal pathogen Candida albicans, the STE18 gene (ORF19.6551.1) encodes a potential γ subunit of a heterotrimeric G protein; this protein contains the C-terminal CAAX box characteristic of γ subunits and has sequence similarity to γ subunits implicated in the mating pathways of a variety of fungi. Disruption of this gene was shown to cause sterility of MTLa mating cells and to block pheromone-induced gene expression and shmoo formation; deletion of just the CAAX box residues is sufficient to inactivate Ste18 function in the mating process. Intriguingly, ectopic expression behind the strong ACT1 promoter of either the Gα or the Gβ subunit of the heterotrimeric G protein is able to suppress the mating defect caused by deletion of the Gγ subunit and restore both pheromone-induced gene expression and morphology changes.
Collapse
|
29
|
Won S, Michkov AV, Krystofova S, Garud AV, Borkovich KA. Genetic and physical interactions between Gα subunits and components of the Gβγ dimer of heterotrimeric G proteins in Neurospora crassa. EUKARYOTIC CELL 2012; 11:1239-48. [PMID: 22903975 PMCID: PMC3485923 DOI: 10.1128/ec.00151-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 08/07/2012] [Indexed: 11/20/2022]
Abstract
Heterotrimeric G proteins are critical regulators of growth and asexual and sexual development in the filamentous fungus Neurospora crassa. Three Gα subunits (GNA-1, GNA-2, and GNA-3), one Gβ subunit (GNB-1), and one Gγ subunit (GNG-1) have been functionally characterized, but genetic epistasis relationships between Gβ and Gα subunit genes have not been determined. Physical association between GNB-1 and FLAG-tagged GNG-1 has been previously demonstrated by coimmunoprecipitation, but knowledge of the Gα binding partners for the Gβγ dimer is currently lacking. In this study, the three N. crassa Gα subunits are analyzed for genetic epistasis with gnb-1 and for physical interaction with the Gβγ dimer. We created double mutants lacking one Gα gene and gnb-1 and introduced constitutively active, GTPase-deficient alleles for each Gα gene into the Δgnb-1 background. Genetic analysis revealed that gna-3 is epistatic to gnb-1 with regard to negative control of submerged conidiation. gnb-1 is epistatic to gna-2 and gna-3 for aerial hyphal height, while gnb-1 appears to act upstream of gna-1 and gna-2 during aerial conidiation. None of the activated Gα alleles restored female fertility to Δgnb-1 mutants, and the gna-3(Q208L) allele inhibited formation of female reproductive structures, consistent with a need for Gα proteins to cycle through the inactive GDP-bound form for these processes. Coimmunoprecipitation experiments using extracts from the gng-1-FLAG strain demonstrated that the three Gα proteins interact with the Gβγ dimer. The finding that the Gβγ dimer interacts with all three Gα proteins is supported by epistasis between gnb-1 and gna-1, gna-2, and gna-3 for at least one function.
Collapse
Affiliation(s)
- Susan Won
- Department of Plant Pathology and Microbiology, Institute for Integrative Genome Biology, University of California-Riverside, CA, USA
| | | | | | | | | |
Collapse
|
30
|
Wang L, Zhai B, Lin X. The link between morphotype transition and virulence in Cryptococcus neoformans. PLoS Pathog 2012; 8:e1002765. [PMID: 22737071 PMCID: PMC3380952 DOI: 10.1371/journal.ppat.1002765] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 05/07/2012] [Indexed: 02/06/2023] Open
Abstract
Cryptococcus neoformans is a ubiquitous human fungal pathogen. This pathogen can undergo morphotype transition between the yeast and the filamentous form and such morphological transition has been implicated in virulence for decades. Morphotype transition is typically observed during mating, which is governed by pheromone signaling. Paradoxically, components specific to the pheromone signaling pathways play no or minimal direct roles in virulence. Thus, the link between morphotype transition and virulence and the underlying molecular mechanism remain elusive. Here, we demonstrate that filamentation can occur independent of pheromone signaling and mating, and both mating-dependent and mating-independent morphotype transition require the transcription factor Znf2. High expression of Znf2 is necessary and sufficient to initiate and maintain sex-independent filamentous growth under host-relevant conditions in vitro and during infection. Importantly, ZNF2 overexpression abolishes fungal virulence in murine models of cryptococcosis. Thus, Znf2 bridges the sex-independent morphotype transition and fungal pathogenicity. The impacts of Znf2 on morphological switch and pathogenicity are at least partly mediated through its effects on cell adhesion property. Cfl1, a Znf2 downstream factor, regulates morphogenesis, cell adhesion, biofilm formation, and virulence. Cfl1 is the first adhesin discovered in the phylum Basidiomycota of the Kingdom Fungi. Together with previous findings in other eukaryotic pathogens, our findings support a convergent evolution of plasticity in morphology and its impact on cell adhesion as a critical adaptive trait for pathogenesis. Although morphogenesis and virulence are commonly associated in many eukaryotic pathogens, the nature of such association is often unknown. For example, Cryptococcus neoformans, a fungal pathogen that causes cryptococcal meningitis, typically undergoes morphological transition between the yeast and the filamentous form during mating. However, molecules that are critical for mating do not directly impact fungal virulence. Thus, the nature of the long observed association between morphotype and virulence in this microbe remains elusive despite decades of effort. Here we demonstrate that constitutively activated pheromone signaling is insufficient to drive morphological transition under mating-suppressing conditions, including those relevant to host physiology. Rather, we demonstrate that sex-independent morphological switching is driven by the transcription factor Znf2 and this regulator controls the ability of this fungus to cause disease. Znf2 governs Cryptococcus morphotype and virulence potential at least partly through its effects on cell surface proteins. One novel adhesin Cfl1functions downstream of Znf2 and it orchestrates morphological switch, cell adhesion, biofilm formation, and pathogenicity. Thus, cell adhesion at least partly underlies the link between morphological transition and pathogenicity in C. neoformans. Our findings provide a platform for further elucidation of the impact of morphotype on virulence in this ubiquitous pathogen. The discovery of Cfl1 and other novel adhesins in Cryptococcus could lay a foundation for the development of vaccines or alternative therapies to combat the fatal diseases caused by this fungus.
Collapse
Affiliation(s)
- Linqi Wang
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | | | | |
Collapse
|
31
|
Titan cells confer protection from phagocytosis in Cryptococcus neoformans infections. EUKARYOTIC CELL 2012; 11:820-6. [PMID: 22544904 DOI: 10.1128/ec.00121-12] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The human fungal pathogen Cryptococcus neoformans produces an enlarged "titan" cell morphology when exposed to the host pulmonary environment. Titan cells exhibit traits that promote survival in the host. Previous studies showed that titan cells are not phagocytosed and that increased titan cell production in the lungs results in reduced phagocytosis of cryptococcal cells by host immune cells. Here, the effect of titan cell production on host-pathogen interactions during early stages of pulmonary cryptococcosis was explored. The relationship between titan cell production and phagocytosis was found to be nonlinear; moderate increases in titan cell production resulted in profound decreases in phagocytosis, with significant differences occurring within the first 24 h of the infection. Not only were titan cells themselves protected from phagocytosis, but titan cell formation also conferred protection from phagocytosis to normal-size cryptococcal cells. Large particles introduced into the lungs were not phagocytosed, suggesting the large size of titan cells protects against phagocytosis. The presence of large particles was unable to protect smaller particles from phagocytosis, revealing that titan cell size alone is not sufficient to provide the observed cross-protection of normal-size cryptococcal cells. These data suggest that titan cells play a critical role in establishment of the pulmonary infection by promoting the survival of the entire population of cryptococcal cells.
Collapse
|
32
|
Analysis of Cryptococcus neoformans sexual development reveals rewiring of the pheromone-response network by a change in transcription factor identity. Genetics 2012; 191:435-49. [PMID: 22466042 DOI: 10.1534/genetics.112.138958] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The fundamental mechanisms that control eukaryotic development include extensive regulation at the level of transcription. Gene regulatory networks, composed of transcription factors, their binding sites in DNA, and their target genes, are responsible for executing transcriptional programs. While divergence of these control networks drives species-specific gene expression that contributes to biological diversity, little is known about the mechanisms by which these networks evolve. To investigate how network evolution has occurred in fungi, we used a combination of microarray expression profiling, cis-element identification, and transcription-factor characterization during sexual development of the human fungal pathogen Cryptococcus neoformans. We first defined the major gene expression changes that occur over time throughout sexual development. Through subsequent bioinformatic and molecular genetic analyses, we identified and functionally characterized the C. neoformans pheromone-response element (PRE). We then discovered that transcriptional activation via the PRE requires direct binding of the high-mobility transcription factor Mat2, which we conclude functions as the elusive C. neoformans pheromone-response factor. This function of Mat2 distinguishes the mechanism of regulation through the PRE of C. neoformans from all other fungal systems studied to date and reveals species-specific adaptations of a fungal transcription factor that defies predictions on the basis of sequence alone. Overall, our findings reveal that pheromone-response network rewiring has occurred at the level of transcription factor identity, despite the strong conservation of upstream and downstream components, and serve as a model for how selection pressures act differently on signaling vs. gene regulatory components during eukaryotic evolution.
Collapse
|
33
|
Tzima AK, Paplomatas EJ, Tsitsigiannis DI, Kang S. The G protein β subunit controls virulence and multiple growth- and development-related traits in Verticillium dahliae. Fungal Genet Biol 2012; 49:271-83. [PMID: 22387367 DOI: 10.1016/j.fgb.2012.02.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 02/10/2012] [Accepted: 02/13/2012] [Indexed: 11/26/2022]
Abstract
To gain insight into the role of G protein-mediated signaling in virulence and development of the soilborne, wilt causing fungus Verticillium dahliae, the G protein β subunit gene (named as VGB) was disrupted in tomato race 1 strain of V. dahliae. A resulting mutant strain, 70ΔGb15, displayed drastic reduction in virulence, increased microsclerotia formation and conidiation, and decreased ethylene production compared to the corresponding wild type (wt) strain 70wt-r1. Moreover, 70ΔGb15 exhibited an elongated rather than radial growth pattern on agar media. A transformant of 70ΔGb15 (named as 70ΔGbPKAC1) that carries an extra copy of VdPKAC1, a V. dahliae gene encoding the catalytic subunit of the cAMP-dependent protein kinase A, exhibited wt growth pattern and conidiation, was unable to form microsclerotia, produced high amounts of ethylene, and exhibited virulence between that of 70ΔGb15 and 70wt-r1 on tomato plants. Phenotypical changes observed in 70ΔGb15 and 70ΔGbPKAC1 correlated with transcriptional changes in several genes involved in signaling (MAP kinase VMK1) and development (hydrophobin VDH1 and ACC synthase ACS1) of V. dahliae. Results from the present work suggest a linkage between VGB and VdPKAC1 signaling pathways in regulating virulence, hormone production and development in V. dahliae.
Collapse
Affiliation(s)
- Aliki K Tzima
- Laboratory of Plant Pathology, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
| | | | | | | |
Collapse
|
34
|
Cryptococcal titan cell formation is regulated by G-protein signaling in response to multiple stimuli. EUKARYOTIC CELL 2011; 10:1306-16. [PMID: 21821718 DOI: 10.1128/ec.05179-11] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The titan cell is a recently described morphological form of the pathogenic fungus Cryptococcus neoformans. Occurring during the earliest stages of lung infection, titan cells are 5 to 10 times larger than the normal yeast-like cells, thereby resisting engulfment by lung phagocytes and favoring the persistence of infection. These enlarged cells exhibit an altered capsule structure, a thickened cell wall, increased ploidy, and resistance to nitrosative and oxidative stresses. We demonstrate that two G-protein-coupled receptors are important for induction of the titan cell phenotype: the Ste3a pheromone receptor (in mating type a cells) and the Gpr5 protein. Both receptors control titan cell formation through elements of the cyclic AMP (cAMP)/protein kinase A (PKA) pathway. This conserved signaling pathway, in turn, mediates its effect on titan cells through the PKA-regulated Rim101 transcription factor. Additional downstream effectors required for titan cell formation include the G(1) cyclin Pcl103, the Rho104 GTPase, and two GTPase-activating proteins, Gap1 and Cnc1560. These observations support developing models in which the PKA signaling pathway coordinately regulates many virulence-associated phenotypes in diverse human pathogens.
Collapse
|
35
|
Abstract
The ability of fungi to transition between unicellular and multicellular growth has a profound impact on our health and the economy. Many important fungal pathogens of humans, animals, and plants are dimorphic, and the ability to switch between morphological states has been associated with their virulence. Cryptococcus neoformans is a human fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised and, in some cases, immunocompetent hosts. Cryptococcus neoformans grows vegetatively as a budding yeast and switches to hyphal growth during the sexual cycle, which is important in the study of cryptococcal pathogenicity because spores resulting from sexual development are infectious propagules and can colonize the lungs of a host. In addition, sexual reproduction contributes to the genotypic variability of Cryptococcus species, which may lead to increased fitness and virulence. Despite significant advances in our understanding of the mechanisms behind the development of C. neoformans, our knowledge is still incomplete. Recent studies have led to the emergence of many intriguing questions and hypotheses. In this review, we describe and discuss the most interesting aspects of C. neoformans development and address their impact on pathogenicity.
Collapse
Affiliation(s)
- Lukasz Kozubowski
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | | |
Collapse
|
36
|
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.
Collapse
Affiliation(s)
| | | | - Leah E. Cowen
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| |
Collapse
|
37
|
Tisch D, Kubicek CP, Schmoll M. New insights into the mechanism of light modulated signaling by heterotrimeric G-proteins: ENVOY acts on gna1 and gna3 and adjusts cAMP levels in Trichoderma reesei (Hypocrea jecorina). Fungal Genet Biol 2011; 48:631-40. [PMID: 21220037 PMCID: PMC3082050 DOI: 10.1016/j.fgb.2010.12.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 12/23/2010] [Accepted: 12/30/2010] [Indexed: 11/26/2022]
Abstract
Sensing of environmental signals is often mediated by G-protein coupled receptors and their cognate heterotrimeric G-proteins. In Trichoderma reesei (Hypocrea jecorina) the signals transmitted via the G-protein alpha subunits GNA1 and GNA3 cause considerable modulation of cellulase transcript levels and the extent of this adjustment is dependent on the light status. We therefore intended to elucidate the underlying mechanism connecting light response and heterotrimeric G-protein signaling. Analysis of double mutant strains showed that constitutive activation of GNA1 or GNA3 in the absence of the PAS/LOV domain protein ENVOY (ENV1) leads to the phenotype of constitutive G-alpha activation in darkness. In light, however the deletion-phenotype of Δenv1 was observed with respect to growth, conidiation and cellulase gene transcription. Additionally deletion of env1 causes decreased intracellular cAMP accumulation, even upon constitutive activation of GNA1 or GNA3. While supplementation of cAMP caused an even more severe growth phenotype of all strains lacking env1 in light, addition of the phosphodiesterase inhibitor caffeine rescued the growth phenotype of these strains. ENV1 is consequently suggested to connect the light response pathway with nutrient signaling by the heterotrimeric G-protein cascade by adjusting transcript levels of gna1 and gna3 and action on cAMP levels - presumably through inhibition of a phosphodiesterase.
Collapse
Affiliation(s)
| | | | - Monika Schmoll
- Research Area of Gene Technology and Applied Biochemistry, Institute for Chemical Engineering, Vienna University of Technology, Gumpendorfer Strasse 1a/1665, A-1060 Wien, Austria
| |
Collapse
|
38
|
Cryptococcus neoformans mediator protein Ssn8 negatively regulates diverse physiological processes and is required for virulence. PLoS One 2011; 6:e19162. [PMID: 21559476 PMCID: PMC3084776 DOI: 10.1371/journal.pone.0019162] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 03/28/2011] [Indexed: 12/17/2022] Open
Abstract
Cryptococcus neoformans is a ubiquitously distributed human pathogen. It is also a model system for studying fungal virulence, physiology and differentiation. Light is known to inhibit sexual development via the evolutionarily conserved white collar proteins in C. neoformans. To dissect molecular mechanisms regulating this process, we have identified the SSN8 gene whose mutation suppresses the light-dependent CWC1 overexpression phenotype. Characterization of sex-related phenotypes revealed that Ssn8 functions as a negative regulator in both heterothallic a-α mating and same-sex mating processes. In addition, Ssn8 is involved in the suppression of other physiological processes including invasive growth, and production of capsule and melanin. Interestingly, Ssn8 is also required for the maintenance of cell wall integrity and virulence. Our gene expression studies confirmed that deletion of SSN8 results in de-repression of genes involved in sexual development and melanization. Epistatic and yeast two hybrid studies suggest that C. neoformans Ssn8 plays critical roles downstream of the Cpk1 MAPK cascade and Ste12 and possibly resides at one of the major branches downstream of the Cwc complex in the light-mediated sexual development pathway. Taken together, our studies demonstrate that the conserved Mediator protein Ssn8 functions as a global regulator which negatively regulates diverse physiological and developmental processes and is required for virulence in C. neoformans.
Collapse
|
39
|
Pashkov V, Huang J, Parameswara VK, Kedzierski W, Kurrasch DM, Tall GG, Esser V, Gerard RD, Uyeda K, Towle HC, Wilkie TM. Regulator of G protein signaling (RGS16) inhibits hepatic fatty acid oxidation in a carbohydrate response element-binding protein (ChREBP)-dependent manner. J Biol Chem 2011; 286:15116-25. [PMID: 21357625 DOI: 10.1074/jbc.m110.216234] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
G protein-coupled receptor (GPCR) pathways control glucose and fatty acid metabolism and the onset of obesity and diabetes. Regulators of G protein signaling (RGS) are GTPase-activating proteins (GAPs) for G(i) and G(q) α-subunits that control the intensity and duration of GPCR signaling. Herein we determined the role of Rgs16 in GPCR regulation of liver metabolism. Rgs16 is expressed during the last few hours of the daily fast in periportal hepatocytes, the oxygen-rich zone of the liver where lipolysis and gluconeogenesis predominate. Rgs16 knock-out mice had elevated expression of fatty acid oxidation genes in liver, higher rates of fatty acid oxidation in liver extracts, and higher plasma β-ketone levels compared with wild type mice. By contrast, transgenic mice that overexpressed RGS16 protein specifically in liver exhibited reciprocal phenotypes as well as low blood glucose levels compared with wild type littermates and fatty liver after overnight fasting. The transcription factor carbohydrate response element-binding protein (ChREBP), which induces fatty acid synthesis genes in response to high carbohydrate feeding, was unexpectedly required during fasting for maximal Rgs16 transcription in liver and in cultured primary hepatocytes during gluconeogenesis. Thus, RGS16 provides a signaling mechanism for glucose production to inhibit GPCR-stimulated fatty acid oxidation in hepatocytes.
Collapse
Affiliation(s)
- Victor Pashkov
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
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.
Collapse
|
41
|
Mechanisms of unisexual mating in Cryptococcus neoformans. Fungal Genet Biol 2011; 48:651-60. [PMID: 21320625 DOI: 10.1016/j.fgb.2011.02.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2010] [Revised: 01/22/2011] [Accepted: 02/03/2011] [Indexed: 12/25/2022]
Abstract
Sex serves a pivotal role in genetic exchange and it contributes to the fitness and genetic diversity for eukaryotic populations. Although the importance of the canonical bisexual mating has been widely accepted, the significance of the evolution and maintenance of unisexual mating observed in some eukaryotes is unclear. The recent discovery of same-sex mating in the human fungal pathogen Cryptococcus neoformans and the revelation of its impact on the Cryptococcus global population structure provide a platform to elucidate the molecular mechanisms and significance of unisexual mating. Here, we review the evidence of unisexual mating in Cryptococcus and provide some perspective on the biological significance of this life style on the survival of this important fungal pathogen in the environment and in animal hosts. We also summarize our current understanding of the molecular mechanisms governing this unconventional mode of reproduction.
Collapse
|
42
|
Liu KH, Shen WC. Mating differentiation in Cryptococcus neoformans is negatively regulated by the Crk1 protein kinase. Fungal Genet Biol 2010; 48:225-40. [PMID: 21111055 DOI: 10.1016/j.fgb.2010.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 11/12/2010] [Accepted: 11/13/2010] [Indexed: 01/27/2023]
Abstract
Cryptococcus neoformans is a heterothallic basidiomycete that grows vegetatively as yeast and filamentous hyphae are produced in the sexual state. Previous studies have shown that C. neoformans Cwc1 and Cwc2 are two central photoregulators which form a complex to inhibit the production of sexual filaments upon light treatment. To reveal the detailed regulatory mechanisms, a genome wide mutagenesis screen was conducted and components in the Cwc1/Cwc2 complex mediated pathway have been identified. In this study, one suppressor mutant, DJ22, is characterized and T-DNA is found to disrupt the C. neoformans CRK1 gene, a homologue of Saccharomyces cerevisiae IME2 and Ustilago maydis crk1. Ime2 is a meiosis-specific gene with the conserved Ser/Thr kinase domain and TXY dual phosphorylation site. Consistent with the findings of other suppressors in our screen, C. neoformans Crk1 plays a negative role in the mating process. Dikaryotic filaments, basidia, and basidiospores are produced earlier in the crk1 mutant crosses and mating efficiency is also increased. Artificial elevation of the CRK1 mRNA level inhibits mating. Interestingly, monokaryotic fruiting is defective both in the MATα crk1 mutant and CRK1 overexpression strains. Our studies demonstrate that C. neoformans CRK1 gene functions as a negative regulator in the mating differentiation.
Collapse
Affiliation(s)
- Kuang-Hung Liu
- Department of Plant Pathology and Microbiology, National Taiwan University, No. 1 Roosevelt Road, Taipei, Taiwan
| | | |
Collapse
|
43
|
Assessment of constitutive activity of a G protein-coupled receptor, CPR2, in Cryptococcus neoformans by heterologous and homologous methods. Methods Enzymol 2010. [PMID: 21036243 DOI: 10.1016/b978-0-12-381298-8.00020-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
G protein-coupled receptors (GPCRs) comprise the largest superfamily of cell surface receptors and are primary targets for drug development. A variety of detection systems have been reported to study ligand-GPCR interactions. Using Saccharomyces cerevisiae to express foreign proteins has long been appreciated for its low cost, simplicity, and conserved cellular pathways. The yeast pheromone-responsive pathway has been utilized to assess a range of different GPCRs. We have identified a pheromone-like receptor, Cpr2, that is located outside of the MAT locus in the human fungal pathogen Cryptococcus neoformans. To characterize its function and potential ligands, we expressed CPR2 in a yeast heterologous expression system. To optimize for CPR2 expression in this system, pheromone receptor Ste3, regulator of G protein signaling (RGS) Sst2, and the cyclin-dependent kinase inhibitor Far1 were mutated. The lacZ gene was fused with the promoter of the FUS1 gene that is activated by the yeast pheromone signal and then introduced into yeast cells. Expression of CPR2 in this yeast heterologous expression system revealed that Cpr2 could activate the pheromone-responsive pathway without addition of potential ligands, suggesting it is a naturally occurring, constitutively active receptor. Mutation of a single amino acid, Leu(222), was sufficient to reverse the constitutive activity of Cpr2. In this chapter, we summarize methods used for assessing the constitutive activity of Cpr2 and its mutants, which could be beneficial for other GPCR studies.
Collapse
|
44
|
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.
Collapse
Affiliation(s)
- Kwang-Woo Jung
- Department of Biotechnology, Center for Fungal Pathogenesis, Yonsei University, Seoul, Republic of Korea
| | | | | | | | | |
Collapse
|
45
|
Park YD, Panepinto J, Shin S, Larsen P, Giles S, Williamson PR. Mating pheromone in Cryptococcus neoformans is regulated by a transcriptional/degradative "futile" cycle. J Biol Chem 2010; 285:34746-56. [PMID: 20801870 DOI: 10.1074/jbc.m110.136812] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Sexual reproduction in fungi requires induction of signaling pheromones within environments that are conducive to mating. The fungus Cryptococcus neoformans is currently the fourth greatest cause of infectious death in regions of Africa and undergoes mating in phytonutrient-rich environments to create spores with infectious potential. Here we show that under conditions where sexual development is inhibited, a ∼17-fold excess of MFα pheromone transcript is synthesized and then degraded by a DEAD box protein, Vad1, resulting in low steady state transcript levels. Transfer to mating medium or deletion of the VAD1 gene resulted in high level accumulation of MFα transcripts and enhanced mating, acting in concert with the mating-related HOG1 pathway. We then investigated whether the high metabolic cost of this apparently futile transcriptional cycle could be justified by a more rapid induction of mating. Maintenance of Vad1 activity on inductive mating medium by constitutive expression resulted in repressed levels of MFα that did not prevent but rather prolonged the time to successful mating from 5-6 h to 15 h (p < 0.0001). In sum, these data suggest that VAD1 negatively regulates the sexual cell cycle via degradation of constitutive high levels of MFα transcripts in a synthetic/degradative cycle, providing a mechanism of mRNA induction for time-critical cellular events, such as mating induction.
Collapse
Affiliation(s)
- Yoon-Dong Park
- Laboratory of Clinical Infectious Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | |
Collapse
|
46
|
Abstract
The genome sequences of the basidiomycete Agaricomycetes species Coprinopsis cinerea, Laccaria bicolor, Schizophyllum commune, Phanerochaete chrysosporium, and Postia placenta, as well as of Cryptococcus neoformans and Ustilago maydis, are now publicly available. Out of these fungi, C. cinerea, S. commune, and U. maydis, together with the budding yeast Saccharomyces cerevisiae, have been investigated for years genetically and molecularly for signaling in sexual reproduction. The comparison of the structure and organization of mating type genes in fungal genomes reveals an amazing conservation of genes regulating the sexual reproduction throughout the fungal kingdom. In agaricomycetes, two mating type loci, A, coding for homeodomain type transcription factors, and B, encoding a pheromone/receptor system, regulate the four typical mating interactions of tetrapolar species. Evidence for both A and B mating type genes can also be identified in basidiomycetes with bipolar systems, where only two mating interactions are seen. In some of these fungi, the B locus has lost its self/nonself discrimination ability and thus its specificity while retaining the other regulatory functions in development. In silico analyses now also permit the identification of putative components of the pheromone-dependent signaling pathways. Induction of these signaling cascades leads to development of dikaryotic mycelia, fruiting body formation, and meiotic spore production. In pheromone-dependent signaling, the role of heterotrimeric G proteins, components of a mitogen-activated protein kinase (MAPK) cascade, and cyclic AMP-dependent pathways can now be defined. Additionally, the pheromone-dependent signaling through monomeric, small GTPases potentially involved in creating the polarized cytoskeleton for reciprocal nuclear exchange and migration during mating is predicted.
Collapse
|
47
|
Navarro-Olmos R, Kawasaki L, Domínguez-Ramírez L, Ongay-Larios L, Pérez-Molina R, Coria R. The beta subunit of the heterotrimeric G protein triggers the Kluyveromyces lactis pheromone response pathway in the absence of the gamma subunit. Mol Biol Cell 2010; 21:489-98. [PMID: 20016006 PMCID: PMC2814793 DOI: 10.1091/mbc.e09-06-0472] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 11/24/2009] [Accepted: 12/02/2009] [Indexed: 11/25/2022] Open
Abstract
The Kluyveromyces lactis heterotrimeric G protein is a canonical Galphabetagamma complex; however, in contrast to Saccharomyces cerevisiae, where the Ggamma subunit is essential for mating, disruption of the KlGgamma gene yielded cells with almost intact mating capacity. Expression of a nonfarnesylated Ggamma, which behaves as a dominant-negative in S. cerevisiae, did not affect mating in wild-type and DeltaGgamma cells of K. lactis. In contrast to the moderate sterility shown by the single DeltaKlGalpha, the double DeltaKlGalpha DeltaKlGgamma mutant displayed full sterility. A partial sterile phenotype of the DeltaKlGgamma mutant was obtained in conditions where the KlGbeta subunit interacted defectively with the Galpha subunit. The addition of a CCAAX motif to the C-end of KlGbeta, partially suppressed the lack of both KlGalpha and KlGgamma subunits. In cells lacking KlGgamma, the KlGbeta subunit cofractionated with KlGalpha in the plasma membrane, but in the DeltaKlGalpha DeltaKlGgamma strain was located in the cytosol. When the KlGbeta-KlGalpha interaction was affected in the DeltaKlGgamma mutant, most KlGbeta fractionated to the cytosol. In contrast to the generic model of G-protein function, the Gbeta subunit of K. lactis has the capacity to attach to the membrane and to activate mating effectors in absence of the Ggamma subunit.
Collapse
Affiliation(s)
- Rocío Navarro-Olmos
- *Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and
| | - Laura Kawasaki
- *Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and
| | - Lenin Domínguez-Ramírez
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California at Davis, Davis, CA 95616
| | - Laura Ongay-Larios
- *Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and
| | - Rosario Pérez-Molina
- *Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and
| | - Roberto Coria
- *Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico and
| |
Collapse
|
48
|
Remodeling of global transcription patterns of Cryptococcus neoformans genes mediated by the stress-activated HOG signaling pathways. EUKARYOTIC CELL 2009; 8:1197-217. [PMID: 19542307 DOI: 10.1128/ec.00120-09] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The ability to sense and adapt to a hostile host environment is a crucial element for virulence of pathogenic fungi, including Cryptococcus neoformans. These cellular responses are evoked by diverse signaling cascades, including the stress-activated HOG pathway. Despite previous analysis of central components of the HOG pathway, its downstream signaling network is poorly characterized in C. neoformans. Here we performed comparative transcriptome analysis with HOG signaling mutants to explore stress-regulated genes and their correlation with the HOG pathway in C. neoformans. In this study, we not only provide important insights into remodeling patterns of global gene expression for counteracting external stresses but also elucidate novel characteristics of the HOG pathway in C. neoformans. First, inhibition of the HOG pathway increases expression of ergosterol biosynthesis genes and cellular ergosterol content, conferring a striking synergistic antifungal activity with amphotericin B and providing an excellent opportunity to develop a novel therapeutic method for treatment of cryptococcosis. Second, a number of cadmium-sensitive genes are differentially regulated by the HOG pathway, and their mutation causes resistance to cadmium. Finally, we have discovered novel stress defense and HOG-dependent genes, which encode a sodium/potassium efflux pump, protein kinase, multidrug transporter system, and elements of the ubiquitin-dependent system.
Collapse
|
49
|
Hsueh YP, Xue C, Heitman J. A constitutively active GPCR governs morphogenic transitions in Cryptococcus neoformans. EMBO J 2009; 28:1220-33. [PMID: 19322200 DOI: 10.1038/emboj.2009.68] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 02/23/2009] [Indexed: 11/09/2022] Open
Abstract
Sex in fungi is driven by peptide pheromones sensed through seven-transmembrane pheromone receptors. In Cryptococcus neoformans, sexual reproduction occurs through an outcrossing/heterothallic a- sexual cycle or an inbreeding/homothallic - unisexual mating process. Pheromone receptors encoded by the mating-type locus (MAT) mediate reciprocal pheromone sensing during opposite-sex mating and contribute to but are not essential for unisexual mating. A pheromone receptor-like gene, CPR2, was discovered that is not encoded by MAT and whose expression is induced during a- mating. cpr2 mutants are fertile but have a fusion defect and produce abnormal hyphal structures, whereas CPR2 overexpression elicits unisexual reproduction. When heterologously expressed in Saccharomyces cerevisiae, Cpr2 activates pheromone responses in the absence of any ligand. This constitutive activity results from an unconventional residue, Leu(222), in place of a conserved proline in transmembrane domain six; a Cpr2(L222P) mutant is no longer constitutively active. Cpr2 engages the same G-protein activated signalling cascade as the Ste3a/alpha pheromone receptors, and thereby competes for pathway activation. This study established a new paradigm in which a naturally occurring constitutively active G protein-coupled receptor governs morphogenesis in fungi.
Collapse
Affiliation(s)
- Yen-Ping Hsueh
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA
| | | | | |
Collapse
|
50
|
Xue C, Hsueh YP, Heitman J. Magnificent seven: roles of G protein-coupled receptors in extracellular sensing in fungi. FEMS Microbiol Rev 2008; 32:1010-32. [PMID: 18811658 DOI: 10.1111/j.1574-6976.2008.00131.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
G protein-coupled receptors (GPCRs) represent the largest family of transmembrane receptors and are responsible for transducing extracellular signals into intracellular responses that involve complex intracellular-signaling networks. This review highlights recent research advances in fungal GPCRs, including classification, extracellular sensing, and G protein-signaling regulation. The involvement of GPCRs in pheromone and nutrient sensing has been studied extensively over the past decade. Following recent advances in fungal genome sequencing projects, a panoply of GPCR candidates has been revealed and some have been documented to play key roles sensing diverse extracellular signals, such as pheromones, sugars, amino acids, nitrogen sources, and even photons. Identification and deorphanization of additional putative GPCRs may require the development of new research tools. Here, we compare research on GPCRs in fungi with information derived from mammalian systems to provide a useful road map on how to better understand ligand-GPCR-G protein interactions in general. We also emphasize the utility of yeast as a discovery tool for systemic studies of GPCRs from other organisms.
Collapse
Affiliation(s)
- Chaoyang Xue
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
| | | | | |
Collapse
|