scholarly journals The Role of Oxidoreductase-Like Protein Olp1 in Sexual Reproduction and Virulence of Cryptococcus neoformans

2020 ◽  
Vol 8 (11) ◽  
pp. 1730
Author(s):  
Qi-Kun Yu ◽  
Lian-Tao Han ◽  
Yu-Juan Wu ◽  
Tong-Bao Liu
Keyword(s):  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Expression Patterns ◽  
Fungal Virulence ◽  
Growth Defects ◽  
Human Fungal Pathogen ◽  
Yeast Extract Peptone Dextrose ◽  
Virulence Attenuation ◽  
Protein Encoding ◽  
Fungal Mating

Cryptococcus neoformans is a basidiomycete human fungal pathogen causing lethal meningoencephalitis, mainly in immunocompromised patients. Oxidoreductases are a class of enzymes that catalyze redox, playing a crucial role in biochemical reactions. In this study, we identified one Cryptococcus oxidoreductase-like protein-encoding gene OLP1 and investigated its role in the sexual reproduction and virulence of C. neoformans. Gene expression patterns analysis showed that the OLP1 gene was expressed in each developmental stage of Cryptococcus, and the Olp1 protein was located in the cytoplasm of Cryptococcus cells. Although it produced normal major virulence factors such as melanin and capsule, the olp1Δ mutants showed growth defects on the yeast extract peptone dextrose (YPD) medium supplemented with lithium chloride (LiCl) and 5-fluorocytosine (5-FC). The fungal mating analysis showed that Olp1 is also essential for fungal sexual reproduction, as olp1Δ mutants show significant defects in hyphae growth and basidiospores production during bisexual reproduction. The fungal nuclei imaging showed that during the bilateral mating of olp1Δ mutants, the nuclei failed to undergo meiosis after fusion in the basidia, indicating that Olp1 is crucial for regulating meiosis during mating. Moreover, Olp1 was also found to be required for fungal virulence in C. neoformans, as the olp1Δ mutants showed significant virulence attenuation in a murine inhalation model. In conclusion, our results showed that the oxidoreductase-like protein Olp1 is required for both fungal sexual reproduction and virulence in C. neoformans.

scholarly journals Autophagy Regulates Fungal Virulence and Sexual Reproduction in Cryptococcus neoformans

2020 ◽  
Vol 8 ◽  
Author(s):  
Su-Ting Jiang ◽  
An-Ni Chang ◽  
Lian-Tao Han ◽  
Jie-Shu Guo ◽  
Yuan-Hong Li ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Fungal Virulence

scholarly journals Sex-Specific Homeodomain Proteins Sxi1α and Sxi2a Coordinately Regulate Sexual Development in Cryptococcus neoformans

2005 ◽  
Vol 4 (3) ◽  
pp. 526-535 ◽  
Author(s):  
Christina M. Hull ◽  
Marie-Josee Boily ◽  
Joseph Heitman
Keyword(s):  
Cryptococcus Neoformans ◽  
Sexual Development ◽  
Expression Patterns ◽  
Regulatory Protein ◽  
Control Cell ◽  
Sexual Cycle ◽  
Homeodomain Protein ◽  
Homeodomain Proteins ◽  
Human Fungal Pathogen ◽  
Cell Type Specific

ABSTRACT Homeodomain proteins are central regulators of development in eukaryotes. In fungi, homeodomain proteins have been shown to control cell identity and sexual development. Cryptococcus neoformans is a human fungal pathogen with a defined sexual cycle that produces spores, the suspected infectious particles. Previously, only a single homeodomain regulatory protein involved in sexual development, Sxi1α, had been identified. Here we present the discovery of Sxi2a, a predicted but heretofore elusive cell-type-specific homeodomain protein essential for the regulation of sexual development. Our studies reveal that Sxi2a is necessary for proper sexual development and sufficient to drive this development in otherwise haploid α cells. We further show that Sxi1α and Sxi2a interact with one another and impart similar expression patterns for two key mating genes. The discovery of Sxi2a and its relationship with Sxi1α leads to a new model for how the sexual cycle is controlled in C. neoformans, with implications for virulence.

scholarly journals The F-Box Protein Fbp1 Regulates Sexual Reproduction and Virulence in Cryptococcus neoformans

2011 ◽  
Vol 10 (6) ◽  
pp. 791-802 ◽  
Author(s):  
Tong-Bao Liu ◽  
Yina Wang ◽  
Sabriya Stukes ◽  
Qing Chen ◽  
Arturo Casadevall ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Stress Responses ◽  
Membrane Integrity ◽  
Infection Model ◽  
Calcofluor White ◽  
Fungal Virulence ◽  
Content Type ◽  
F Box Protein

ABSTRACTCryptococcus neoformansis the leading cause of fungal meningitis in immunocomprised populations. Although extensive studies have been conducted on signal transduction pathways important for fungal sexual reproduction and virulence, how fungal virulence is regulated during infection is still not understood. In this study, we identified the F-box protein Fbp1, which contains a putative F-box domain and 12 leucine-rich repeats (LRR). Althoughfbp1mutants showed normal growth and produced normal major virulence factors, such as melanin and capsule, Fbp1 was found to be essential for fungal virulence, asfbp1mutants were avirulent in a murine systemic-infection model. Fbp1 is also important for fungal sexual reproduction. Basidiospore production was blocked in bilateral mating betweenfbp1mutants, even though normal dikaryotic hyphae were observed during mating.In vitroassays of stress responses revealed thatfbp1mutants are hypersensitive to SDS, but not calcofluor white (CFW) or Congo red, indicating that Fbp1 may regulate cell membrane integrity. Fbp1 physically interacts with Skp1 homologues in bothSaccharomyces cerevisiaeandC. neoformansvia its F-box domain, suggesting it may function as part of an SCF (Skp1, Cullins, F-box proteins) E3 ligase. Overall, our study revealed that the F-box protein Fbp1 is essential for fungal sporulation and virulence inC. neoformans, which likely represents a conserved novel virulence control mechanism that involves the SCF E3 ubiquitin ligase-mediated proteolysis pathway.

scholarly journals Fbp1-Mediated Ubiquitin-Proteasome Pathway Controls Cryptococcus neoformans Virulence by Regulating Fungal Intracellular Growth in Macrophages

2013 ◽  
Vol 82 (2) ◽  
pp. 557-568 ◽  
Author(s):  
Tong-Bao Liu ◽  
Chaoyang Xue
Keyword(s):  
Cryptococcus Neoformans ◽  
Time Course ◽  
Ubiquitin Proteasome System ◽  
Phenotypic Analysis ◽  
Fungal Virulence ◽  
Content Type ◽  
Brain Infection ◽  
Virulence Attenuation ◽  
Ubiquitin Proteasome ◽  
F Box Protein

ABSTRACTCryptococcus neoformansis a human fungal pathogen that often causes lung and brain infections in immunocompromised patients, with a high fatality rate. Our previous results showed that an F-box protein, Fbp1, is essential forCryptococcusvirulence independent of the classical virulence factors, suggesting a novel virulence control mechanism. In this study, we show that Fbp1 is part of the ubiquitin-proteasome system, and we further investigated the mechanism of Fbp1 function during infection. Time course studies revealed that thefbp1Δ mutant causes little damage in the infected lung and that the fungal burden in the lung remains at a low but persistent level throughout infection. Thefbp1Δ mutant cannot disseminate to other organs following pulmonary infection in the murine inhalation model of cryptococcosis but still causes brain infection in a murine intravenous injection model, suggesting that the block of dissemination of thefbp1Δ mutant is due to its inability to leave the lung. Thefbp1Δ mutant showed a defect in intracellular proliferation after phagocytosis in aCryptococcus-macrophage interaction assay, which likely contributes to its virulence attenuation. To elucidate the molecular basis of the SCF(Fbp1) E3 ligase function, we analyzed potential Fbp1 substrates based on proteomic approaches combined with phenotypic analysis. One substrate, the inositol phosphosphingolipid-phospholipase C1 (Isc1), is required for fungal survival inside macrophage cells, which is consistent with the role of Fbp1 in regulatingCryptococcus-macrophage interaction and fungal virulence. Our results thus reveal a new determinant of fungal virulence that involves the posttranslational regulation of inositol sphingolipid biosynthesis.

scholarly journals A Predicted Mannoprotein Cmp1 Regulates Fungal Virulence in Cryptococcus neoformans

Pathogens ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 881
Author(s):  
Lian-Tao Han ◽  
Lei Wu ◽  
Tong-Bao Liu
Keyword(s):  
Cryptococcus Neoformans ◽  
Fungal Pathogen ◽  
Gene Expression Pattern ◽  
Fungal Virulence ◽  
Human Fungal Pathogen ◽  
Overexpression Strain ◽  
Reproduction Process ◽  
Localization Analysis ◽  
Survival Assay

The capsule of the fungal pathogen Cryptococcus neoformans consists of glucuronoxylomannan (GXM), glucuronoxylomannogalactan (GXMGal), and mannoproteins (MPs). MPs are a kind of glycoproteins with low content but high immunogenicity, which can stimulate the immune protection of the host. However, there is not much information about the role of mannoproteins in virulence of the human fungal pathogen C. neoformans. In this study, we reported the identification and functional analysis of a predicted mannoprotein Cmp1 that regulates fungal virulence in C. neoformans. Gene expression pattern analysis indicates that the CMP1 gene was ubiquitously expressed at all stages of cryptococcal development. Subcellular localization analysis indicated that Cmp1 was localized in the cytoplasm of cryptococcal cells. Disruption or overexpression of CMP1 results in impairing capsule formation in Cryptococcus, but it does not affect the melanin production and sensitivity under various stress conditions, nor does it affect the sexual reproduction process of Cryptococcus. Survival assay showed that the pathogenicity of the cmp1Δ mutant or the CMP1 overexpression strain was significantly attenuated in a murine inhalation model of cryptococcosis. In conclusion, our findings implied that the mannoprotein Cmp1 is required for the virulence of C. neoformans.

scholarly journals Role of an Expanded Inositol Transporter Repertoire in Cryptococcus neoformans Sexual Reproduction and Virulence

mBio ◽  
2010 ◽  
Vol 1 (1) ◽  
Author(s):  
Chaoyang Xue ◽  
Tongbao Liu ◽  
Lydia Chen ◽  
Wenjun Li ◽  
Iris Liu ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Gene Family ◽  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Yeast Cells ◽  
Sexual Cycle ◽  
Fungal Virulence ◽  
Content Type ◽  
Fungal Meningitis

ABSTRACTCryptococcus neoformansandCryptococcus gattiiare globally distributed human fungal pathogens and the leading causes of fungal meningitis. Recent studies reveal thatmyo-inositol is an important factor for fungal sexual reproduction. ThatC. neoformanscan utilizemyo-inositol as a sole carbon source and the existence of abundant inositol in the human central nervous system suggest that inositol is important forCryptococcusdevelopment and virulence. In accord with this central importance of inositol, an expandedmyo-inositol transporter (ITR) gene family has been identified inCryptococcus. This gene family contains two phylogenetically distinct groups, with a total of 10 or more members inC. neoformansand at least six members in the sibling speciesC. gattii. These inositol transporter genes are differentially expressed under inositol-inducing conditions based on quantitative real-time PCR analyses. Expression ofITRgenes in aSaccharomyces cerevisiaeitr1 itr2mutant lacking inositol transport can complement the slow-growth phenotype of this strain, confirming thatITRgenes arebona fideinositol transporters. Gene mutagenesis studies reveal that the Itr1 and Itr1A transporters are important formyo-inositol stimulation of mating and that functional redundancies among themyo-inositol transporters likely exist. Deletion of the inositol 1-phosphate synthase geneINO1in anitr1oritr1amutant background compromised virulence in a murine inhalation model, indicating the importance of inositol sensing and acquisition for fungal infectivity. Our study provides a platform for further understanding the roles of inositol in fungal physiology and virulence.IMPORTANCECryptococcus neoformansis an AIDS-associated human fungal pathogen that causes over 1 million cases of meningitis annually and is the leading cause of fungal meningitis in immunosuppressed patients. The initial cryptococcal infection is caused predominantly via inhalation of sexual spores or desiccated yeast cells from the environment. How this fungus completes its sexual cycle and produces infectious spores in nature and why it frequently infects the central nervous system to cause fatal meningitis are critical questions that remain to be understood. In this study, we demonstrate that inositol acquisition is important not only for fungal sexual reproduction but also for fungal virulence. We identified an expanded inositol transporter gene family that contains over 10 members, important for both fungal sexual reproduction and virulence. Our work contributes to our understanding of how fungi respond to the environmental inositol availability and its impact on sexual reproduction and virulence.

scholarly journals The Casein Kinase I Protein Cck1 Regulates Multiple Signaling Pathways and Is Essential for Cell Integrity and Fungal Virulence in Cryptococcus neoformans

2011 ◽  
Vol 10 (11) ◽  
pp. 1455-1464 ◽  
Author(s):  
Yina Wang ◽  
Tong-Bao Liu ◽  
Shyam Patel ◽  
Linghuo Jiang ◽  
Chaoyang Xue
Keyword(s):  
Signaling Pathways ◽  
Cryptococcus Neoformans ◽  
Casein Kinase ◽  
Cell Integrity ◽  
Casein Kinase I ◽  
Fungal Virulence ◽  
Content Type ◽  
Virulence Attenuation ◽  
Wide Range ◽  
Multiple Signaling

ABSTRACTCasein kinases regulate a wide range of cellular functions in eukaryotes, including phosphorylation of proteins that are substrates for degradation via the ubiquitin-proteasome system (UPS). Our previous study demonstrated that Fbp1, a component of the SCFFBP1E3 ligase complex, was essential forCryptococcusvirulence. Because theSaccharomyces cerevisiaehomolog of Fbp1, Grr1, requires casein kinase I (Yck1 and Yck2) to phosphorylate its substrates, we investigated the function of casein kinase I inCryptococcus neoformans. In this report, we identified aC. neoformanscasein kinase I protein homolog, Cck1. Similar to Fbp1, the expression of Cck1 is negatively regulated by glucose and during mating.cck1null mutants showed significant virulence attenuation in a murine systemic infection model, but Cck1 was dispensable for the development of classical virulence factors (capsule, melanin, and growth at 37°C).cck1mutants were hypersensitive to SDS treatment, indicating that Cck1 is required for cell integrity. The functional overlap between Cck1 and Fbp1 suggests that Cck1 may be required for the phosphorylation of Fbp1 substrates. Interestingly, thecck1mutant also showed increased sensitivity to osmotic stress and oxidative stress, suggesting that Cck1 regulates both cell integrity and the cellular stress response. Our results show that Cck1 regulates the phosphorylation of both Mpk1 and Hog1 mitogen-activated protein kinases (MAPKs), demonstrating that Cck1 regulates cell integrity via the Mpk1 pathway and regulates cell adaptation to stresses via the Hog1 pathway. Overall, our study revealed that Cck1 plays important roles in regulating multiple signaling pathways and is required for fungal pathogenicity.

scholarly journals The Cryptococcus neoformans Rho-GDP Dissociation Inhibitor Mediates Intracellular Survival and Virulence

2008 ◽  
Vol 76 (12) ◽  
pp. 5729-5737 ◽  
Author(s):  
Michael S. Price ◽  
Connie B. Nichols ◽  
J. Andrew Alspaugh
Keyword(s):  
Cryptococcus Neoformans ◽  
Cell Morphology ◽  
Culture Medium ◽  
Intracellular Survival ◽  
Murine Models ◽  
Gene Encoding ◽  
Cellular Processes ◽  
Growth Defects ◽  
Human Fungal Pathogen ◽  
Gdp Dissociation Inhibitor

ABSTRACT Rho-GDP dissociation inhibitors (Rho-GDI) are repressors of Rho-type monomeric GTPases that control fundamental cellular processes, such as cytoskeletal arrangement, vesicle trafficking, and polarized growth. We identified and altered the expression of the gene encoding a Rho-GDI homolog in the human fungal pathogen Cryptococcus neoformans and investigated its impact on pathogenicity in animal models of cryptococcosis. Consistent with its predicted function to inhibit and sequester Rho-type GTPases, overexpression of RDI1 results in cytosolic localization of Cdc42. Likely as a result of this finding, RDI1-overexpressing strains exhibited altered morphology compared to that of the wild type, with apparent defects in maintaining proper cell polarity and cytokinesis. RDI1 deletion resulted in increased vacuole size in tissue culture medium and aberrant cell morphology at neutral pH. Maintenance of normal cell morphology is vital for C. neoformans pathogenicity. Accordingly, the rdi1Δ mutant strain also showed reduced intracellular survival in macrophages and severe attenuation of virulence in two murine models of cryptococcosis. This reduction in virulence of the rdi1Δ mutant occurs in the absence of major growth defects in rich medium and with classical virulence-associated phenotypes.

scholarly journals Development of Protective Inflammation and Cell-Mediated Immunity against Cryptococcus neoformans after Exposure to Hyphal Mutants

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Bing Zhai ◽  
Karen L. Wozniak ◽  
Jorge Masso-Silva ◽  
Srijana Upadhyay ◽  
Camaron Hole ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Cryptococcal Meningitis ◽  
Early Stage ◽  
Future Research ◽  
Clinical Strain ◽  
Cell Mediated Immunity ◽  
Fungal Virulence ◽  
Filamentous Form ◽  
Content Type ◽  
Virulence Attenuation

ABSTRACTMorphological switch is tightly coupled with the pathogenesis of many dimorphic fungal pathogens.Cryptococcus neoformans, the major causative agent of cryptococcal meningitis, mostly presents as the yeast form but is capable of switching to the hyphal form. The filamentous form has long been associated with attenuated virulence, yet the underlying mechanism remains elusive. We previously identified the master regulator Znf2 that controls the yeast-to-hypha transition inCryptococcus. Activation of Znf2 promotes hyphal formation and abolishes fungal virulencein vivo. Here we demonstrated that the cryptococcal strain overexpressingZNF2elicited strong and yet temporally confined proinflammatory responses in the early stage of infection. In contrast, exacerbated inflammation in mice infected with the wild-type (WT) strain showed that they were unable to control the infection. Animals inoculated with this filamentousCryptococcusstrain had fewer pulmonary eosinophils and CD11c+CD11b+cells than animals inoculated with WT yeast. Moreover, mice infected with this strain developed protective Th1- or Th17-type T cell responses. These findings suggest that the virulence attenuation of the filamentous form is likely due to its elicitation of protective host responses. The antivirulence effect of Znf2 was independent of two previously identified factors downstream of Znf2. Interestingly, mucosal immunizations with high doses ofZNF2-overexpressing cells, either in the live or heat-killed form, offered 100% protection to the host from a subsequent challenge with the otherwise lethal clinical strain H99. Our results demonstrate that heat-resistant cellular components presented in cryptococcal cells with activatedZNF2elicit protective host immune responses. These findings could facilitate future research on novel immunological therapies.IMPORTANCECryptococcal meningitis is one of the leading causes of death among AIDS patients. This disease presents a severe threat to public health. The current antifungal regimens are unsatisfactory in controlling or clearing the pathogenCryptococcus neoformans. Immunotherapies and/or vaccines could be a promising approach to prevent or manage this deadly disease. However, the lack of understanding of host-pathogen interactions during cryptococcal infection greatly hampers the development of effective immunotherapies. In this study, we discovered that inoculation of cryptococcal cells with activated Znf2, a morphogenesis regulator and an antivirulence factor, could shift the host pathological Th2 responses to the protective Th1 or Th17 responses. Importantly, we discovered that vaccination with either the viable or heat-killed form ofZNF2-overexpressing cells protected animals from the otherwise lethal infection by the highly virulent clinical strain. Our study suggests that the fungal cellular component(s) of theZNF2-overexpressing strain may provide potential vaccine candidate(s) for controlling the fatal disease.

scholarly journals Role of F-box Protein Cdc4 in Fungal Virulence and Sexual Reproduction of Cryptococcus neoformans

2022 ◽  
Vol 11 ◽  
Author(s):  
Ting Wu ◽  
Cheng-Li Fan ◽  
Lian-Tao Han ◽  
Yuan-Bing Guo ◽  
Tong-Bao Liu
Keyword(s):  
Sexual Reproduction ◽  
Cryptococcus Neoformans ◽  
Stress Responses ◽  
Genetic Material ◽  
Membrane Integrity ◽  
Infection Model ◽  
Regulation Mechanism ◽  
Fungal Virulence ◽  
F Box Protein

Cryptococcus neoformans is an opportunistic yeast-like pathogen that mainly infects immunocompromised individuals and causes fatal meningitis. Sexual reproduction can promote the exchange of genetic material between different strains of C. neoformans, which is one of the reasons leading to the emergence of highly pathogenic and drug-resistant strains of C. neoformans. Although much research has been done on the regulation mechanism of Cryptococcus sexual reproduction, there are few studies on the sexual reproduction regulation of Cryptococcus by the ubiquitin-proteasome system. This study identified an F-box protein, Cdc4, which contains a putative F-box domain and eight WD40 domains. The expression pattern analysis showed that the CDC4 gene was expressed in various developmental stages of C. neoformans, and the Cdc4 protein was localized in the nucleus of cryptococcal cells. In vitro stress responses assays showed that the CDC4 overexpression strains are sensitive to SDS and MMS but not Congo red, implying that Cdc4 may regulate the cell membrane integrity and repair of DNA damage of C. neoformans. Fungal virulence assay showed that although the cdc4Δ mutant grows normally and can produce typical virulence factors such as capsule and melanin, the cdc4Δ mutant completely loses its pathogenicity in a mouse systemic-infection model. Fungal mating assays showed that Cdc4 is also essential for fungal sexual reproduction in C. neoformans. Although normal mating hyphae were observed during mating, the basidiospores’ production was blocked in bilateral mating between cdc4Δ mutants. Fungal nuclei development assay showed that the nuclei failed to undergo meiosis after fusion inside the basidia during the bilateral mating of cdc4Δ mutants, indicating that Cdc4 is critical to regulating meiosis during cryptococcal mating. In summary, our study revealed that the F-box protein Cdc4 is critical for fungal virulence and sexual reproduction in C. neoformans.

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