101
|
Kraus PR, Nichols CB, Heitman J. Calcium- and calcineurin-independent roles for calmodulin in Cryptococcus neoformans morphogenesis and high-temperature growth. EUKARYOTIC CELL 2005; 4:1079-87. [PMID: 15947200 PMCID: PMC1151996 DOI: 10.1128/ec.4.6.1079-1087.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The function of calcium as a signaling molecule is conserved in eukaryotes from fungi to humans. Previous studies have identified the calcium-activated phosphatase calcineurin as a critical factor in governing growth of the human pathogenic fungus Cryptococcus neoformans at mammalian body temperature. Here, we employed insertional mutagenesis to identify new genes required for growth at 37 degrees C. One insertion mutant, cam1-ts, that displayed a growth defect at 37 degrees C and hypersensitivity to the calcineurin inhibitor FK506 at 25 degrees C was isolated. Both phenotypes were linked to the dominant marker in genetic crosses, and molecular analysis revealed that the insertion occurred in the 3' untranslated region of the gene encoding the calcineurin activator calmodulin (CAM1) and impairs growth at 37 degrees C by significantly reducing calmodulin mRNA abundance. The CAM1 gene was demonstrated to be essential using genetic analysis of a CAM1/cam1Delta diploid strain. In the absence of calcineurin function, the cam1-ts mutant displayed a severe morphological defect with impaired bud formation. Expression of a calmodulin-independent calcineurin mutant did not suppress the growth defect of the cam1-ts mutant at 37 degrees C, indicating that calmodulin promotes growth at high temperature via calcineurin-dependent and -independent pathways. In addition, a Ca2+-binding-defective allele of CAM1 complemented the 37 degrees C growth defect, FK506 hypersensitivity, and morphogenesis defect of the cam1-ts mutant. Our findings reveal that calmodulin performs Ca2+- and calcineurin-independent and -dependent roles in controlling C. neoformans morphogenesis and high-temperature growth.
Collapse
Affiliation(s)
- Peter R Kraus
- Department of Molecular Genetics and Microbiology, 322 CARL Building, Box 3546, Research Drive, Duke University Medical Center, Durham, NC 27710, USA
| | | | | |
Collapse
|
102
|
Vallim MA, Nichols CB, Fernandes L, Cramer KL, Alspaugh JA. A Rac homolog functions downstream of Ras1 to control hyphal differentiation and high-temperature growth in the pathogenic fungus Cryptococcus neoformans. EUKARYOTIC CELL 2005; 4:1066-78. [PMID: 15947199 PMCID: PMC1151989 DOI: 10.1128/ec.4.6.1066-1078.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The Cryptococcus neoformans Ras1 protein serves as a central regulator for several signaling pathways. Ras1 controls the induction of the mating pheromone response cascade as well as a distinct signaling pathway that allows this pathogenic fungus to grow at human physiological temperature. To characterize elements of the Ras1-dependent high-temperature growth pathway, we performed a multicopy suppressor screen, identifying genes whose overexpression allows the ras1 mutant to grow at 37 degrees C. Using this genetic technique, we identified a C. neoformans gene encoding a Rac homolog that suppresses multiple ras1 mutant phenotypes. Deletion of the RAC1 gene does not affect high-temperature growth. However, a rac1 mutant strain demonstrates a profound defect in haploid filamentation as well as attenuated mating. In a yeast two-hybrid assay, Rac1 physically interacts with the PAK kinase Ste20, which similarly regulates hyphal formation in this fungus. Similar to Rac1, overexpression of the STE20alpha gene also restores high-temperature growth to the ras1 mutant. These results support a model in which the small G protein Rac1 acts downstream of Ras proteins and coordinately with Ste20 to control high-temperature growth and cellular differentiation in this human fungal pathogen.
Collapse
Affiliation(s)
- Marcelo A Vallim
- Department of Medicine, Duke University Medical Center (DUMC) 3355, Durham, NC 27710, USA
| | | | | | | | | |
Collapse
|
103
|
Fox DS, Heitman J. Calcineurin-binding protein Cbp1 directs the specificity of calcineurin-dependent hyphal elongation during mating in Cryptococcus neoformans. EUKARYOTIC CELL 2005; 4:1526-38. [PMID: 16151246 PMCID: PMC1214203 DOI: 10.1128/ec.4.9.1526-1538.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Accepted: 06/20/2005] [Indexed: 11/20/2022]
Abstract
Mating and virulence of the human fungal pathogen Cryptococcus neoformans are controlled by calcineurin, a serine-threonine-specific calcium-activated phosphatase that is the target of the immunosuppressive drugs cyclosporine A and FK506. In previous studies, a calcineurin binding protein (Cbp1, Rcn1, Dscr1/Csp1-3/MCIP1-3) that is conserved from yeasts to humans has been identified, but whether this protein functions to regulate calcineurin activity or facilitate calcineurin function as a signaling effector has been unclear. Here we show that, like calcineurin, Cbp1 is required for mating in C. neoformans. By contrast, Cbp1 plays no role in promoting calcineurin-dependent growth at 37 degrees C and is not essential for haploid fruiting. Site-directed mutagenesis studies provide evidence that tandem phosphorylation and dephosphorylation of two serine residues in the conserved SP repeat motif are critical for Cbp1 function. Epistasis analysis supports models in which Cbp1 functions coordinately with calcineurin to direct hyphal elongation during mating. Taken together, these findings provide insights into the roles of Cbp1 as an accessory subunit or effector of calcineurin-specific signaling pathways, which may be features conserved among the calcipressins to govern calcineurin signaling in immune cells, cardiomyocytes, and neurons of multicellular eukaryotes.
Collapse
Affiliation(s)
- Deborah S Fox
- Research Institute for Children and Department of Pediatrics, Louisiana State Health Science Center, Children's Hospital, 200 Henry Clay Avenue, New Orleans, LA 70118, USA.
| | | |
Collapse
|
104
|
Jacobson ES, Troy AJ, Nyhus KJ. Mitochondrial functioning of constitutive iron uptake mutations in Cryptococcus neoformans. Mycopathologia 2005; 159:1-6. [PMID: 15750726 DOI: 10.1007/s11046-004-2223-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 06/08/2004] [Indexed: 10/25/2022]
Abstract
Randomly obtained, constitutive plasma membrane ferric reductase/ferrous uptake mutants of Cryptococcus neoformans were mapped to four distinct loci by meiotic analysis. One of those loci, FRR1 , was previously found homologous to MRS3 and MRS4 of Saccharomyces cerevisiae , which determine proteins involved in mitochondrial transport of iron. We were able to complement, clone, sequence and thereby identify two of the three remaining constitutive uptake loci. FRR3 was found to be homologous to ISU1 and ISU2 of S. cerevisiae, which form mitochondrial iron-sulfur complexes; FRR4 was found to be homologous to YFH1, the yeast frataxin homologue, which also participates in iron-sulfur cluster biogenesis. Because of the constitutive iron uptake seen in these mutants, mitochondria appear to have a central role in the cellular iron economy; moreover, as judged by our mutational statistics, the genetic machinery for mitochondrial iron accumulation may be more complex than that of the cytoplasm.
Collapse
Affiliation(s)
- Eric S Jacobson
- Research Service, McGuire Veterans Affairs Medical Center, 1201 Broad Rock Blvd, Richmond, VA 23249, USA.
| | | | | |
Collapse
|
105
|
Fox DS, Cox GM, Heitman J. Phospholipid-binding protein Cts1 controls septation and functions coordinately with calcineurin in Cryptococcus neoformans. EUKARYOTIC CELL 2004; 2:1025-35. [PMID: 14555485 PMCID: PMC219374 DOI: 10.1128/ec.2.5.1025-1035.2003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised patients. The Ca(2+)-calmodulin-activated protein phosphatase calcineurin is necessary for virulence of C. neoformans. Mutants lacking the calcineurin catalytic (Cna1) or regulatory (Cnb1) subunit fail to grow at elevated temperature and are defective in virulence and hyphal elongation. Here we isolated a multicopy suppressor gene, CTS1, which restores growth of a calcineurin mutant strain at 37 degrees C. The CTS1 gene (for calcineurin temperature suppressor 1) encodes a protein containing a C2 domain and a leucine zipper motif that may function as an effector of calcineurin. The CTS1 gene was disrupted by homologous recombination, and cts1 mutants were viable but exhibited defects in cell separation, growth, mating, and haploid fruiting. In addition, cts1 mutants were inviable when calcineurin was mutated or inhibited. Taken together, these findings suggest that calcineurin and Cts1 function in parallel pathways that regulate growth, cell separation, and hyphal elongation.
Collapse
Affiliation(s)
- Deborah S Fox
- Departments of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | |
Collapse
|
106
|
Steinbach WJ, Schell WA, Blankenship JR, Onyewu C, Heitman J, Perfect JR. In vitro interactions between antifungals and immunosuppressants against Aspergillus fumigatus. Antimicrob Agents Chemother 2004; 48:1664-9. [PMID: 15105118 PMCID: PMC400573 DOI: 10.1128/aac.48.5.1664-1669.2004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The optimal treatment for invasive aspergillosis remains elusive, despite the increased efficacy of newer agents. The immunosuppressants cyclosporine (CY), tacrolimus (FK506), and sirolimus (formerly called rapamycin) exhibit in vitro and in vivo activity against Candida albicans, Cryptococcus neoformans, and Saccharomyces cerevisiae, including fungicidal synergy with azole antifungals. We report here that both FK506 and CY exhibit a clear in vitro positive interaction with caspofungin against Aspergillus fumigatus by disk diffusion, microdilution checkerboard, and gross and microscopic morphological analyses. Microscopic morphological analyses indicate that the calcineurin inhibitors delay filamentation, and in combination with caspofungin there is a positive interaction. Our findings suggest a potential role for combination therapy with calcineurin pathway inhibitors and existing antifungal agents to augment activity against A. fumigatus.
Collapse
Affiliation(s)
- William J Steinbach
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710, USA.
| | | | | | | | | | | |
Collapse
|
107
|
Viaud M, Brunet-Simon A, Brygoo Y, Pradier JM, Levis C. Cyclophilin A and calcineurin functions investigated by gene inactivation, cyclosporin A inhibition and cDNA arrays approaches in the phytopathogenic fungus Botrytis cinerea. Mol Microbiol 2004; 50:1451-65. [PMID: 14651630 DOI: 10.1046/j.1365-2958.2003.03798.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Calcineurin phosphatase and cyclophilin A are cellular components involved in fungal morphogenesis and virulence. Their roles were investigated in the phytopathogenic fungus Botrytis cinerea using gene inactivation, drug inhibition and cDNA macroarrays approaches. First, the BCP1 gene coding for cyclophilin A was identified and inactivated by homologous recombination. The bcp1Delta null mutant obtained was still able to develop infection structures but was altered in symptom development on bean and tomato leaves. Opposite to this, calcineurin inhibition using cyclosporin A (CsA) modified hyphal morphology and prevented infection structure formation. CsA drug pattern signature on macroarrays allowed the identification of 18 calcineurin-dependent (CND) genes among 2839 B. cinerea genes. Among the co-regulated CND genes, three were shown to be organized as a physical cluster that could be involved in secondary metabolism. The signature of BCP1 inactivation on macroarrays allowed the identification of only three BCP1 cyclophilin-dependent (CPD) genes that were different from CND genes. Finally, no CsA drug pattern signature was observed in the bcp1Delta null mutant which provided a molecular target validation of the drug.
Collapse
Affiliation(s)
- Muriel Viaud
- Unité de Phytopathologie et Méthodologies de la Détection, Institut National de la Recherche Agronomique, Route de Saint-Cyr, 78086 Versailles, France.
| | | | | | | | | |
Collapse
|
108
|
Kraus PR, Heitman J. Coping with stress: calmodulin and calcineurin in model and pathogenic fungi. Biochem Biophys Res Commun 2004; 311:1151-7. [PMID: 14623301 DOI: 10.1016/s0006-291x(03)01528-6] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Calcium signaling via calmodulin and calcineurin is critical for the regulation of stress responses in fungi. The functions of calmodulin and calcineurin are largely conserved among pathogenic fungi and model fungi, however, the mechanisms of action have diverged. Saccharomyces cerevisiae is an excellent model for understanding the framework of calcium-mediated signal transduction pathways, and considerable progress has been made in understanding the details of how Ca(2+)-calmodulin and calcineurin control adaptation to environmental stress. Studies using the divergent human pathogenic fungi Candida albicans and Cryptococcus neoformans reveal that calcineurin is critical for virulence, yet it acts via distinct mechanisms in each fungus. These differences in function may reflect the requirements of each pathogen to survive inside the host, and illustrate that studies must be conducted in each organism in order to elucidate the details of the molecular mechanisms of calmodulin and calcineurin-mediated signaling pathways.
Collapse
Affiliation(s)
- Peter R Kraus
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | | |
Collapse
|
109
|
Tada T, Ohmori M, Iida H. Phe356 in the yeast Ca2+ channel component Mid1 is a key residue for viability after exposure to alpha-factor. Biochem Biophys Res Commun 2004; 313:752-7. [PMID: 14697255 DOI: 10.1016/j.bbrc.2003.11.166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The yeast Mid1 protein is an integral membrane protein required for the viability of differentiated cells and Ca2+ influx induced by mating pheromone. Our previous study has identified a loss-of-function mutation, F356S. The F356S mutant is completely unable to maintain viability, but still has Ca2+ accumulation activity near the wild-type level. Here we further examined in detail the F356S mutation to unravel the function of Phe356. After exposure to the pheromone, the F356S mutant was not fully rescued by high extracellular Ca2+, like the mid1 null mutant, suggesting that Phe356 and Mid1 itself are also required for viability maintenance mechanism that does not involve Ca2+ signalling. Substitutions of hydrophilic amino acids for Phe356 caused lethality and low Ca2+ accumulation, but those of hydrophobic amino acids did not. Substitutions of small amino acids for Phe356 caused a significantly reduced viability, but did not affect Ca2+ accumulation. We suggest that the hydrophobicity of the Phe356 residue is important for both viability maintenance and Ca2+ uptake, and that its size for viability maintenance.
Collapse
Affiliation(s)
- Tomoko Tada
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukuikita-machi, Koganei-shi, Tokyo 184-8501, Japan
| | | | | |
Collapse
|
110
|
Shitamukai A, Hirata D, Sonobe S, Miyakawa T. Evidence for antagonistic regulation of cell growth by the calcineurin and high osmolarity glycerol pathways in Saccharomyces cerevisiae. J Biol Chem 2003; 279:3651-61. [PMID: 14583627 DOI: 10.1074/jbc.m306098200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Because Ca(2+) signaling of budding yeast, through the activation of calcineurin and the Mpk1/Slt2 mitogen-activated protein kinase cascade, performs redundant function(s) in the events essential for growth, the simultaneous deletion of both these pathways (Delta cnb1 Delta mpk1) leads to lethality. A PTC4 cDNA that encodes a protein phosphatase belonging to the PP2C family was obtained as a high dosage suppressor of the lethality of Delta cnb1 Delta mpk1 strain. Overexpression of PTC4 led to a decrease in the high osmolarity-induced Hog1 phosphorylation, and HOG1 deletion remarkably suppressed the synthetic lethality, indicating an antagonistic role of the high osmolarity glycerol (HOG) pathway and the Ca(2+) signaling pathway in growth regulation. The calcineurin-Crz1 pathway was required for the down-regulation of the HOG pathway. Analysis of the time course of actin polarization, bud formation, and the onset of mitosis in synchronous cell cultures demonstrated that calcineurin negatively regulates actin polarization at the bud site, whereas the HOG pathway positively regulates bud formation at a later step after actin has polarized.
Collapse
Affiliation(s)
- Atsunori Shitamukai
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | | | | | | |
Collapse
|
111
|
Bader T, Bodendorfer B, Schröppel K, Morschhäuser J. Calcineurin is essential for virulence in Candida albicans. Infect Immun 2003; 71:5344-54. [PMID: 12933882 PMCID: PMC187310 DOI: 10.1128/iai.71.9.5344-5354.2003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Calcineurin is a conserved Ca(2+)-calmodulin-activated, serine/threonine-specific protein phosphatase that regulates a variety of physiological processes, e.g., cell cycle progression, polarized growth, and adaptation to salt and alkaline pH stresses. In the pathogenic yeast Cryptococcus neoformans, calcineurin is also essential for growth at 37 degrees C and virulence. To investigate whether calcineurin plays a role in the virulence of Candida albicans, the major fungal pathogen of humans, we constructed C. albicans mutants in which both alleles of the CMP1 gene, encoding the calcineurin catalytic subunit, were deleted. The C. albicans Delta cmp1 mutants displayed hypersensitivity to elevated Na(+), Li(+), and Mn(2+) concentrations and to alkaline pH, phenotypes that have been described after calcineurin inactivation in the related yeast Saccharomyces cerevisiae. Unlike S. cerevisiae calcineurin mutants, which exhibit reduced susceptibility to high Ca(2+) concentrations, growth of C. albicans was inhibited in the presence of 300 mM CaCl(2) after the deletion of CMP1, demonstrating that there are also differences in calcineurin-mediated cellular responses between these two yeast species. In contrast to C. neoformans, inactivation of calcineurin did not cause temperature sensitivity in C. albicans. In addition, hyphal growth, an important virulence attribute of C. albicans, was not impaired in the Delta cmp1 mutants under a variety of inducing conditions. Nevertheless, the virulence of the mutants was strongly attenuated in a mouse model of systemic candidiasis, demonstrating that calcineurin signaling is essential for virulence in C. albicans.
Collapse
Affiliation(s)
- Teresa Bader
- Institut für Molekulare Infektionsbiologie, Universität Würzburg, D-97070 Würzburg, Germany
| | | | | | | |
Collapse
|
112
|
Casadevall A, Steenbergen JN, Nosanchuk JD. 'Ready made' virulence and 'dual use' virulence factors in pathogenic environmental fungi--the Cryptococcus neoformans paradigm. Curr Opin Microbiol 2003; 6:332-7. [PMID: 12941400 DOI: 10.1016/s1369-5274(03)00082-1] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Environmental pathogenic fungi present a paradox in that they are virulent in animals without requiring animal hosts for replication or survival, a phenomenon we call 'ready-made' virulence. In the human pathogenic fungus Cryptococcus neoformans, the capacity for virulence in animals may originate from environmental selective pressures imposed by such organisms as amoeboid and nematode predators. Many C. neoformans virulence factors appear to have 'dual use' capabilities that confer survival advantages in both animal hosts and in the environment. The findings with C. neoformans may provide a paradigm for understanding the origin and maintenance of virulence in other pathogenic environmental fungi.
Collapse
Affiliation(s)
- Arturo Casadevall
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, New York 10461, USA.
| | | | | |
Collapse
|
113
|
Abstract
Cryptococcus neoformans is a pathogenic fungus that primarily afflicts immunocompromised patients, infecting the central nervous system to cause meningoencephalitis that is uniformly fatal if untreated. C. neoformans is a basidiomycetous fungus with a defined sexual cycle that has been linked to differentiation and virulence. Recent advances in classical and molecular genetic approaches have allowed molecular descriptions of the pathways that control cell type and virulence. An ongoing genome sequencing project promises to reveal much about the evolution of this human fungal pathogen into three distinct varieties or species. C. neoformans shares features with both model ascomycetous yeasts (Saccharomyces cerevisiae, Schizosaccharomyces pombe) and basidiomycetous pathogens and mushrooms (Ustilago maydis, Coprinus cinereus, Schizophyllum commune), yet ongoing studies reveal unique features associated with virulence and the arrangement of the mating type locus. These advances have catapulted C. neoformans to center stage as a model of both fungal pathogenesis and the interesting approaches to life that the kingdom of fungi has adopted.
Collapse
Affiliation(s)
- Christina M Hull
- Department of Molecular Genetics and Microbiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
| | | |
Collapse
|
114
|
Abstract
The antifungal activity of synthetic, nonchemotherapeutic compounds, antineoplastic agents and antibacterial drugs, such as sulphonamides, has been known since the early 20th century (1932). In this context, the term "nonantifungal" is taken to include a variety of compounds that are employed in the management of pathological conditions of nonfungal infectious etiology but have been shown to exhibit broad-spectrum antifungal activity. In this review, the antifungal properties of compounds such as chlorpromazine, proton pump inhibitors, antiarrhythmic agents, cholesterol-lowering agents, antineoplastic and immunosuppressive agents, antiparasitic drugs and antibiotics are described. Since fungi are eukaryotic cells, they share many pathways with human cells, thus increasing the probability of antifungal activity of "nonfungal drugs". The potential of these drugs for treatment of fungal infections has been investigated sporadically using the drugs alone or in combination with "classic" antifungal agents. A review of the literature, supplemented with a number of more recent investigations, suggests that some of these compounds enhance the activity of conventional antifungal agents, eliminate natural resistance to specific antifungal drugs (reversal of resistance) or exhibit strong activity against certain fungal strains in vitro and in animal models. The role of these agents in the epidemiology and in the clinical manifestations of fungal infections and the potential of certain drugs for treatment of invasive fungal infections require further investigation.
Collapse
Affiliation(s)
- J Afeltra
- Department of Medical Microbiology, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | | |
Collapse
|
115
|
Sanglard D, Ischer F, Marchetti O, Entenza J, Bille J. Calcineurin A of Candida albicans: involvement in antifungal tolerance, cell morphogenesis and virulence. Mol Microbiol 2003; 48:959-76. [PMID: 12753189 DOI: 10.1046/j.1365-2958.2003.03495.x] [Citation(s) in RCA: 274] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The azole antifungal fluconazole possesses only fungistatic activity in Candida albicans and, therefore, this human pathogen is tolerant to this agent. However, tolerance to fluconazole can be inhibited when C. albicans is exposed to fluconazole combined with the immunosuppressive drug cyclosporin A, which is known to inhibit calcineurin activity in yeast. A mutant lacking both alleles of a gene encoding the calcineurin A subunit (CNA) lost viability in the presence of fluconazole, thus making calcineurin essential for fluconazole tolerance. Consistent with this observation, tolerance to fluconazole was modulated by calcium ions or by the expression of a calcineurin A derivative autoactivated by the removal of its C-terminal inhibitory domain. Interestingly, CNA was also essential for tolerance to other antifungal agents (voriconazole, itraconazole, terbinafine, amorolfine) and to several other metabolic inhibitors (caffeine, brefeldin A, mycophenolic acid, fluphenazine) or cell wall-perturbing agents (SDS, calcofluor white, Congo red), thus indicating that the calcineurin pathway plays an important role in the survival of C. albicans in the presence of external growth inhibitors. Several genes, including PMC1, a vacuolar calcium P-type ATPase, were regulated in a calcineurin- and fluconazole-dependent manner. However, PMC1 did not play a direct role in the survival of C. albicans when exposed to fluconazole. In addition to these different properties, calcineurin was found to affect colony morphology in several media known to modulate the C. albicans dimorphic switch. In particular, calcineurin was found to be essential for C. albicans viability in serum-containing media. Finally, calcineurin was found to be necessary for the virulence of C. albicans in a mice model of infection, thus making calcineurin an important element for adequate adaptation to the conditions of the host environment.
Collapse
Affiliation(s)
- Dominique Sanglard
- Institute of Microbiology, Centre Hospitalier Universitaire Vaudois (CHUV), Rue du Bugnon 44, CH-1011 Lausanne, Switzerland.
| | | | | | | | | |
Collapse
|
116
|
Nyhus KJ, Ozaki LS, Jacobson ES. Role of mitochondrial carrier protein Mrs3/4 in iron acquisition and oxidative stress resistance of Cryptococcus neoformans. Med Mycol 2002; 40:581-91. [PMID: 12521122 DOI: 10.1080/mmy.40.6.581.591] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Cryptococcus neoformans is a pathogenic basidiomycete that causes meningitis in immunocompromised patients. In this paper, we demonstrate that a previously described oxidant-sensitive mutant, oxy1, has constitutive ferric reductase and iron uptake, similar to a ferric reductase regulatory mutant, frr1. Through meiotic genetic analysis, we show that the two mutations are allelic. By complementation of frr1 with a genomic library, we isolated a gene, MRS3/4. The encoded protein is a putative solute transporter of the inner mitochondrial membrane. Disruption of this gene led to high ferric reductase, iron uptake and iron content, as well as increased sensitivity to hydrogen peroxide and slow growth in low iron medium. The disrupted gene is allelic with oxy1 and frr1. We sequenced the oxy1 and frr1 alleles of MRS3/4 and found that the frr1 mutation results in a premature stop codon, while the oxy1 mutation results in the substitution of a highly conserved glutamate residue with lysine. The Mrs3/4 protein appears to be involved in mitochondrial iron transport in eukaryotes. Resistance to strong oxidants requires stringent control of iron metabolism.
Collapse
Affiliation(s)
- Karin J Nyhus
- Research Service, McGuire Veterans Affairs Medical Center, 1201 Broad Rock Blvd, Richmond, Virginia 23249, USA
| | | | | |
Collapse
|
117
|
Abstract
Calcineurin is a Ca(2+)/calmodulin-activated protein phosphatase that is conserved in eukaryotes, from yeast to humans, and is the conserved target of the immunosuppressive drugs cyclosporin A (CsA) and FK506. Genetic studies in yeast and fungi established the molecular basis of calcineurin inhibition by the cyclophilin A-CsA and FKBP12-FK506 complexes. Calcineurin also functions in fungi to control a myriad of physiological processes including cell cycle progression, cation homeostasis, and morphogenesis. Recent investigations into the molecular mechanisms of pathogenesis in Candida albicans and Cryptococcus neoformans, two fungi that cause life-threatening infections in humans, have revealed an essential role for calcineurin in morphogenesis, virulence, and antifungal drug action. Novel non-immunosuppressive analogs of the calcineurin inhibitors CsA and FK506 that retain antifungal activity have been identified and hold promise as candidate antifungal drugs. In addition, comparisons of calcineurin function in both fungi and humans may identify fungal-specific components of calcineurin-signaling pathways that could be targeted for therapy, as well as conserved elements of calcium signaling events.
Collapse
Affiliation(s)
- Deborah S Fox
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | | |
Collapse
|
118
|
Wickes BL. The role of mating type and morphology in Cryptococcus neoformans pathogenesis. Int J Med Microbiol 2002; 292:313-29. [PMID: 12452279 DOI: 10.1078/1438-4221-00216] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cryptococcus neoformans is a major fungal pathogen of both humans and animals. The fungus can be divided into two varieties, with each variety being composed of two serotypes. A sexual phase has been identified, which classifies C. neoformans as a bipolar heterothallic fungus with two mating types, MATa and MATalpha. The analysis of mating and mating type in this organism is important for a number of reasons. Both clinical and environmental isolates display a severe bias of the MATalpha mating type over MATa. MATalpha cells are also more virulent than MATalpha cells. Molecular and genetic analyses of the genes that make up the mating pathway have revealed that some of these genes are required for virulence. Finally, although it is well known that infection begins in the lungs after inhalation of infectious particles, it still remains unclear what constitutes the infectious particle. This review will discuss current information about what is known about the role that mating type and morphology play in virulence.
Collapse
Affiliation(s)
- Brian L Wickes
- Department of Microbiology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
| |
Collapse
|
119
|
Cruz M, Goldstein AL, Blankenship JR, Del Poeta M, Davis D, Cardenas ME, Perfect JR, McCusker JH, Heitman J. Calcineurin is essential for survival during membrane stress in Candida albicans. EMBO J 2002; 21:546-59. [PMID: 11847103 PMCID: PMC125859 DOI: 10.1093/emboj/21.4.546] [Citation(s) in RCA: 259] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2001] [Revised: 12/12/2001] [Accepted: 12/18/2001] [Indexed: 12/25/2022] Open
Abstract
The immunosuppressants cyclosporin A (CsA) and FK506 inhibit the protein phosphatase calcineurin and block T-cell activation and transplant rejection. Calcineurin is conserved in microorganisms and plays a general role in stress survival. CsA and FK506 are toxic to several fungi, but the common human fungal pathogen Candida albicans is resistant. However, combination of either CsA or FK506 with the antifungal drug fluconazole that perturbs synthesis of the membrane lipid ergosterol results in potent, synergistic fungicidal activity. Here we show that the C.albicans FK506 binding protein FKBP12 homolog is required for FK506 synergistic action with fluconazole. A mutation in the calcineurin B regulatory subunit that confers dominant FK506 resistance (CNB1-1/CNB1) abolished FK506-fluconazole synergism. Candida albicans mutants lacking calcineurin B (cnb1/cnb1) were found to be viable and markedly hypersensitive to fluconazole or membrane perturbation with SDS. FK506 was synergistic with fluconazole against azole-resistant C.albicans mutants, against other Candida species, or when combined with different azoles. We propose that calcineurin is part of a membrane stress survival pathway that could be targeted for therapy.
Collapse
Affiliation(s)
- M.Cristina Cruz
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Alan L. Goldstein
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Jill R. Blankenship
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Maurizio Del Poeta
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Dana Davis
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Maria E. Cardenas
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - John R. Perfect
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - John H. McCusker
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| | - Joseph Heitman
- Departments of Genetics, Pharmacology and Cancer Biology, Microbiology and Medicine, and the Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, Departments of Biochemistry and Microbiology and Immunology, Medical University of South Carolina, Charleston, SC and Department of Microbiology, University of Minnesota, Minneapolis, MN, USA Corresponding author at: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA e-mail:
| |
Collapse
|
120
|
Juvvadi PR, Arioka M, Nakajima H, Kitamoto K. Cloning and sequence analysis of cnaA gene encoding the catalytic subunit of calcineurin from Aspergillus oryzae. FEMS Microbiol Lett 2001; 204:169-74. [PMID: 11682197 DOI: 10.1111/j.1574-6968.2001.tb10881.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Calcineurin has been implicated in ion-homeostasis, stress adaptation in yeast and for hyphal growth in filamentous fungi. Genomic DNA and cDNA encoding the catalytic subunit of calcineurin (cnaA) were isolated from Aspergillus oryzae. The cnaA open reading frame extended to 1727 bp and encoded a putative protein of 514 amino acids. Comparative analysis of the nucleotide sequence of cnaA genomic DNA and cDNA confirmed the presence of three introns and a highly conserved calmodulin binding domain. The deduced amino acid sequence was homologous to calcineurin A from Aspergillus nidulans (92%), Neurospora crassa (84%), human (67%), Saccharomyces cerevisiae (58%) and Schizosaccharomyces pombe (54%). Further, A. oryzae cnaA cDNA complemented S. cerevisiae calcineurin disruptant strain (Deltacmp1 Deltacmp2), which was not viable in the presence of high concentrations of NaCl (1.2 M) and at alkaline pH 8.5.
Collapse
Affiliation(s)
- P R Juvvadi
- Department of Biotechnology, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-Ku, 113-8657 Tokyo, Japan
| | | | | | | |
Collapse
|
121
|
Current Awareness. Yeast 2001. [DOI: 10.1002/yea.687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
|