Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of interleukin (IL)-4 in cryptococcal disease was studied in IL-4 knockout (IL-4KO) and wild-type (WT) mice infected with Cryptococcus neoformans isolates that vary widely in their virulence. Delayed-type hypersensitivity responses were reduced in IL-4KO mice following primary infection with either isolate. Splenic T helper 1 (Th1) cytokine responses were increased in the IL-4KO mice infected with the weakly virulent isolate (184A) but did not change during infection with the highly virulent isolate (NU-2). Th2 cytokine responses (IL-5, IL-10) were downregulated in the IL-4KO mice infected with either isolate. Survival after primary infection with either isolate was not influenced by the absence of IL-4. Fewer colony-forming units were found in the lungs of 184A-infected, IL-4KO mice as compared to WT mice, suggesting that some immunity had developed. IL-4KO mice, primed with small doses of cryptococcal antigen (CneF), had significantly enhanced delayed-type hypersensitivity responses after intravenous infection with 184A and were more resistant to infection compared with WT mice. Increased expression of IL-5 with decreased interferon-gamma contributed to the inability of primed WT mice to resist infection with 184A. Enhanced immunity in the primed IL-4KO mice was reflected in a more moderate increase in IL-5 and IL-10 with maintenance of interferon-gamma levels.
Am J Respir Cell Mol Biol 2004 Jan
PMID:Role of interleukin-4 in resistance to Cryptococcus neoformans infection. 1285 7

Most monoclonal antibodies (mAbs) to Cryptococcus neoformans glucuronoxylomannan (GXM) antigen (Ag) are grouped as Class II based on usage of V(H)7183, Vkappa5.1, J(H)2, and Jkappa1 gene elements. Comparative analysis of 43 Class II mAbs revealed conservation of I51, G54, and D61 in heavy-chain variable region (V(H)) complementarity determining region 2 (CDR2), and R95 and D96 in CDR3. Furthermore, position 100b (Kabat numbering scheme) in CDR3 always had an aromatic amino acid (aa) and F was found at position 100c in 96% of mAbs. The function of these conserved residues for binding to GXM and peptide mimetics, and idiotype (Id) structure, was investigated using site-directed mutagenesis. In addition, we mutated W36 and V37 in the second framework. Mutations W36A, Y100bA, and F100cA interfered with antibody (Ab) secretion, but not assembly, and cytoplasmic Ab bound to GXM and Id mAbs. In contrast, mutations V37A, I51A, G54A, and D61A did not affect assembly, secretion, or binding to GXM. Mutating the R95-D96 motif in CDR3 to DR, DD, RR, RA, AD, KD, HD, RE, RN or AA revealed that the positive charge at position 95 was essential for binding GXM, whereas the negative charge at position 96 could be substituted for a non-charged aa. Our results: (1) extend the concept that CDR3 diversity is essential for Ag and Id specificity to a polysaccharide-binding Ab; (2) show that aa conservation in CDRs does not imply a requirement for Ag binding; (3) establish a role for W36 in secretion; and (4) demonstrate that aa motifs used for binding GXM and peptide mimetics can differ.
Mol Immunol 2003 Oct
PMID:The function of conserved amino acids in or near the complementarity determining regions for related antibodies to Cryptococcus neoformans glucuronoxylomannan. 1452 16

Laccase is a major virulence factor required for infection caused by the human pathogenic yeast Cryptococcus neoformans. However, cellular processes involved in the regulation and expression of laccase remain largely unknown in C. neoformans. Here we report the identification of a chloride channel gene CLC-A which is essential for laccase activity in C. neoformans. CLC-A shares homology to CLC-type voltage-gated chloride channels from other organisms; for example, 63% homology to GEF1, a chloride channel gene from Saccharomyces cerevisiae. A clc-a mutant, Mlac3, generated by insertional mutagenesis as well as a targeted Deltaclc-a mutant produced undetectable laccase in a liquid assay and produced no melanin on asparagine agar containing norepinephrine. Mlac3 was complemented with wild-type CLC-A which restored laccase activity and melanin biosynthesis. The clc-a mutants also showed reduced synthesis of another important virulence factor, capsule, and showed reduced growth at elevated pH. In addition, the clc-a mutation resulted in attenuated virulence in a mouse cryptococcosis model that was restored by complementation with wild-type CLC-A, indicating that the chloride channel plays an important role in the virulence of the organism. Further analysis revealed that the basis for absent laccase expression in the clc-a mutant was a laccase transcriptional defect that could be restored by adding exogenous copper. In conclusion, our findings show that CLC-A plays a role in the expression of two important virulence factors, capsule and laccase expression, which are required for virulence of the fungal pathogen.
Mol Microbiol 2003 Nov
PMID:A CLC-type chloride channel gene is required for laccase activity and virulence in Cryptococcus neoformans. 1462 14

Cryptococcus neoformans is an opportunistic pathogen responsible for serious disease in humans. Critical for virulence of this fungus is an elaborate polysaccharide capsule, which impedes the host immune response. We found that association of the capsule with the cell requires a specific component of the cell wall, alpha-1,3-glucan. Post-transcriptional inhibition of alpha-1,3-glucan synthase expression, using double-stranded RNA interference, yields cells that are unable to assemble a capsule although they generate its polysaccharide components. The resulting cryptococci are slow-growing and acapsular. This finding demonstrates a novel mode of polysaccharide attachment and an important application of RNA interference in fungi. The elimination of the capsule by reducing the expression of a single gene suggests a potential avenue for antifungal chemotherapy.
Mol Microbiol 2003 Nov
PMID:Cell wall alpha-1,3-glucan is required to anchor the Cryptococcus neoformans capsule. 1462 25

Cryptococcus neoformans is a fungal pathogen most commonly causing meningitis in immunocompromised patients. Current therapies are inadequate, and novel antifungal targets are needed. We have identified by proteomics two thiol peroxidases that are differentially expressed at 37 degrees C, the temperature of the mammalian host. Consistent with their antioxidant role, we show that the genes encoding these thiol-specific antioxidants, TSA1 and TSA3, are transcriptionally induced when C. neoformans is exposed to hydrogen peroxide. Genome sequence analysis of C. neoformans revealed a third thiol peroxidase, TSA4. We constructed single, double and triple mutants of the thiol peroxidase genes through homologous recombination and analysed their function by comparing the growth of these mutants with that of the wild-type strain. The tsa1 Delta mutant shows sensitivity to hydrogen peroxide and t-butylhydroperoxide, as well as significant growth retardation at 25 degrees C and 38.5 degrees C. The tsa1 Delta mutant is also sensitive to NO, demonstrating a link between oxidative and nitrosative stress pathways. In two mouse models of cryptococcosis, the tsa1 Delta mutant is significantly less virulent.
Mol Microbiol 2004 Mar
PMID:Thiol peroxidase is critical for virulence and resistance to nitric oxide and peroxide in the fungal pathogen, Cryptococcus neoformans. 1498 37

Many microbes are surrounded by phagocytosis-inhibiting capsules. We took advantage of the large size of the polysaccharide capsule of the pathogenic yeast Cryptococcus neoformans to examine capsular architecture and the relationship between molecular architecture and the interaction of the capsule with potentially opsonic serum proteins. Our experimental design used complementary approaches in which (i) assessment of permeability to macromolecules of different Stokes radii; (ii) determination of the binding of Fab fragments of anticapsular antibodies as a measure of matrix density; (iii) capsular deconstruction by treatment with dimethyl sulphoxide; and (iv) evaluation of capsule plasticity, were used to probe the molecular structure of the capsule. The results showed that the capsule is a matrix with a variable porosity that increases with distance from the cell wall. A high density of the matrix at the capsule interior prevents penetration of large macromolecules to sites near the cell wall. In contrast, the capsular edge that is the interface with phagocytes presents capsular polysaccharide in a very low density that exhibits considerable plasticity and permeability to macromolecules. Notably, the capsule of yeast cells harvested from infected tissue showed a greater matrix density than yeast cells grown in vitro under capsule induction conditions.
Mol Microbiol 2004 Apr
PMID:Molecular architecture of the Cryptococcus neoformans capsule. 1504 7

Sexual identity and mating are linked to virulence of the fungal pathogen Cryptococcus neoformans. Cells of the alpha mating type are more prevalent and can be more virulent than a cells, and basidiospores are thought to be the infectious propagule. Mating in C. neoformans involves cell-cell fusion and the generation of dikaryotic hyphae, processes that involve substantial changes in cell polarity. Two p21-activated kinase (PAK) kinases, Pak1 and Ste20, are required for both mating and virulence in C. neoformans. We show here that Ste20 and Pak1 play crucial roles in polarized morphogenesis at different steps during mating: Pak1 functions during cell fusion, whereas Ste20 fulfills a distinct morphogenic role and is required to maintain polarity in the heterokaryotic mating filament. In conclusion, our studies demonstrate that PAK kinases are necessary for polar growth during mating and that polarity establishment is necessary for mating and may contribute to virulence of C. neoformans.
Mol Biol Cell 2004 Oct
PMID:PAK kinases Ste20 and Pak1 govern cell polarity at different stages of mating in Cryptococcus neoformans. 1528 44

The STE12alpha gene of Cryptococcus neoformans encodes a protein containing both homeodomain and zinc finger regions. As homeodomains and zinc finger regions are important domains for the function of many transcription factors, we used site-specific mutagenesis to delineate the roles of these two domains. The homeodomain and zinc finger regions are each important for the function of Ste12alphap. DNA binding ability, mating frequency, and haploid fruiting capability were reduced in strains with mutations in the homeodomain, whereas virulence and capsule size in the mouse brain were increased. In contrast, mutations in the zinc fingers region resulted in decreased virulence, reduced capsule size in the mouse brain and decreased gene expression of capsule associated genes. In addition, phospholipase activity was increased in the zinc finger mutants. Taken together, most of the phenotypes previously observed in the ste12alpha deletion strains were reproduced in these two types of mutants. However, unlike mutations in the homeodomain/zinc finger region, complete deletion of STE12alpha caused a severe reduction in virulence and a decrease in phospholipase activity. These data suggest that region(s) other than the homeodomain and zinc finger regions of Ste12alphap contribute to the variable influences on the different phenotypes observed in C. neoformans.
Mol Microbiol 2004 Sep
PMID:Regulatory roles for the homeodomain and C2H2 zinc finger regions of Cryptococcus neoformans Ste12alphap. 1538 17

Cryptococcal infections are a global cause of significant morbidity and mortality. Recent studies support the hypothesis that virulence of Cryptococcus neoformans may have evolved via survival selection in environmental hosts, such as amoebae and free-living nematodes. We used killing of the nematode Caenorhabditis elegans by C. neoformans as an assay to screen a library of random C. neoformans insertion mutants. Of 350 mutants tested, seven were identified with attenuated virulence that persisted after crossing the mutation back into a wild-type strain. Genetic analysis of one strain revealed an insertion in a gene homologous to Saccharomyces cerevisiae KIN1, which encodes a serine/threonine protein kinase. C. neoformans kin1 mutants exhibited significant defects in virulence in murine inhalation and haematogenous infection models and displayed increased binding to alveolar and peritoneal macrophages. The kin1 mutant phenotypes were complemented by the wild-type KIN1 gene. These findings show that the C. neoformans Kin1 kinase homologue is required for full virulence in disparate hosts and that C. elegans can be used as a substitute host to identify novel factors involved in fungal pathogenesis in mammals.
Mol Microbiol 2004 Oct
PMID:Cryptococcus neoformans Kin1 protein kinase homologue, identified through a Caenorhabditis elegans screen, promotes virulence in mammals. 1546 13

The use of simple sequence repeats or microsatellites as genetic markers has become very popular because of their abundance and length variation between different individuals. SSRs are tandem repeat units of 1 to 6 base pairs that are found abundantly in many prokaryotic and eukaryotic genomes. This is the first study examining and comparing SSRs in completely sequenced fungal genomes. We analyzed and compared the occurrences, relative abundance, relative density, most common, and longest SSRs in nine taxonomically different fungal species: Aspergillus nidulans, Cryptococcus neoformans, Encephalitozoon cuniculi, Fusarium graminearum, Magnaporthe grisea, Neurospora crassa, Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Ustilago maydis. Our analysis revealed that, in all of the genomes studied, the occurrence, abundance, and relative density of SSRs varied and was not influenced by the genome sizes. No correlation between relative abundance and the genome sizes was observed, but it was shown that N. crassa, the largest genome analyzed had the highest relative abundance of SSRs. In most genomes, mononucleotide, dinucleotide, and trinucleotide repeats were more abundant than the longer repeated SSRs. Generally, in each organism, the occurrence, relative abundance, and relative density of SSRs decreased as the repeat unit increased. Furthermore, each organism had its own common and longest SSRs. Our analysis showed that the relative abundance of SSRs in fungi is low compared with the human genome and that longer SSRs in fungi are rare. In addition to providing new information concerning the abundance of SSRs for each of these fungi, the results provide a general source of molecular markers that could be useful for a variety of applications such as population genetics and strain identification of fungal organisms.
Mol Biol Evol 2005 Mar
PMID:Survey of simple sequence repeats in completed fungal genomes. 1556 17


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