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B Maresca

Publications and source records attributed to B Maresca.

At least 37 records · Page 2Linked to original sources
PubMed1994

The Histoplasma capsulatum cdc2 gene is transcriptionally regulated during the morphologic transition.

To understand the molecular mechanisms that control the reversible morphologic transition from mycelia to yeast in dimorphic fungi, we have isolated and characterized a cdc2 gene from Histoplasma capsulatum. This organism is a dimorphic pathogenic fungus that grows as a filamentous saprobic mold in soil and as a unicellular pathogenic yeast in human tissue. The cloned gene, whose protein product has a high degree of homology with other members of the cdc2 family, is split into four exons and three introns of 95, 52 and 85 nucleotides. Analyses of cDNA clones confirm the presence of the eukaryotic splice donor (GT) and acceptor (AG) sites. The spliced gene codes for a protein of 324 amino acids (aa) with a predicted molecular mass of 36.9 kDa. The H. capsulatum cdc2 product has 71% aa identity with Saccharomyces cerevisiae and 70% with Schizosaccharomyces pombe. The deduced protein contains the sequence, PSTAIRE, that is normally found in most p34cdc2 proteins. H. capsulatum cdc2 is transcriptionally regulated during the morphologic mycelium<==>yeast transitions and is more actively transcribed in the yeast than in the mycelial phase.

Amino Acid Sequence↗
PubMed1994

Morphological transition in the human fungal pathogen Histoplasma capsulatum.

Considerable information has accumulated recently about specific genes of Histoplasma capsulatum that are expressed during the process of adaptation when the organism undergoes morphological transition at the onset of infection. The study of these genes is crucial to identify targets for the development of novel antifungal agents.

Histoplasma↗
PubMed1993

Changes in membrane fluidity modulate heat shock gene expression and produced attenuated strains in the dimorphic fungus Histoplasma capsulatum.

In the dimorphic fungus Histoplasma capsulatum the expression of heat shock genes is modulated by addition of fatty acids. Addition at 25 degrees C of saturated fatty acid (palmitic acid) to mycelia of H. capsulatum induced a significant increase in heat shock mRNAs transcription when cells were heat shocked. Conversely, treatments with unsaturated fatty acid (oleic acid) drastically reduced the level of heat shock gene transcription at 37 degrees C, and no detectable levels were measurable with 2 mM. Addition of saturated fatty acid induced a thermotolerant state and mitochondria retained ATPase activity coupled to electron transport under severe heat shock conditions and shortened the time required for mycelium-to-yeast phase transition. Conversely, addition of unsaturated fatty acids uncoupled mitochondrial electron transport and prolonged considerably the time required for phase transition at the same temperatures. A virulent strain, if treated with unsaturated fatty acid under condition in which no heat shock was detectable, lost its virulence probably as a consequence of decreased ability to adapt to the new living condition present in the host.

Cell Membrane↗
PubMed1992

Molecular cloning and expression of hsp82 gene of the dimorphic pathogenic fungus Histoplasma capsulatum.

We have cloned a nucleotide sequence from Histoplasma capsulatum G222B corresponding to a heat inducible hsp82 gene, and determined its entire sequence and the flanking regions. During the temperature-controlled mycelium-to-yeast phase transition the gene is more actively transcribed at 37 degrees C in the temperature tolerant and mouse-virulent G222B strain, while 34 degrees C is the optimum for transcription in the temperature sensitive and mouse-avirulent Downs strain.

Amino Acid Sequence↗
PubMed1992

The biology of the heat shock response in parasites.

The heat shock response is a general homeostatic mechanism that protects cells and the entire organism from the deleterious effects of environmental stress. It has been shown that heat shock proteins play major roles in many cellular processes and have a unique role in several areas of cell biology, from chronic degenerative diseases to immunology and from cancer research to interactions between host and parasite. In this review, Bruno Maresca and Luisella Carratu deal with some of the unique characteristics of the heat shock response in parasitic organisms.

Journal Article↗
PubMed1991

The intron-containing hsp82 gene of the dimorphic pathogenic fungus Histoplasma capsulatum is properly spliced in severe heat shock conditions.

We have isolated and characterized a heat-inducible gene, hsp82, from the dimorphic pathogenic fungus Histoplasma capsulatum, which is a filamentous mold at 25 degrees C and a unicellular yeast at 37 degrees C. This gene, which has a high degree of homology with other members of the hsp82 gene family, is split into three exons and two introns of 122 and 86 nucleotides, respectively. Contrary to what has been demonstrated in Drosophila melanogaster, Saccharomyces cerevisiae, and other organisms, hsp82 mRNA in H. capsulatum is properly spliced during the severe heat conditions of 37 to 40 degrees C in the temperature-sensitive Downs strain. Splicing accuracy was also observed at 42 degrees C in the temperature-tolerant G222B strain, which showed no evidence of accumulation of primary transcripts. Furthermore, the intron containing the beta-tubulin gene is also properly spliced at the upper temperature range, suggesting that the lack of a block in splicing may be a general phenomenon in this organism.

Amino Acid Sequence↗
PubMed1990

Acquired thermotolerance following heat shock protein synthesis prevents impairment of mitochondrial ATPase activity at elevated temperatures in Saccharomyces cerevisiae.

The complex molecular response of cells to sudden temperature changes is a well-characterized phenomenon. Although it is clear that the induction of heat shock proteins provides protection from heat in all of the organisms so far tested, very little is known about the role that this set of proteins plays in cellular homeostasis. Recently, putative roles for hsp60 and hsp70-like proteins have been proposed in Saccharomyces cerevisiae. hsp70-like proteins have been shown to be necessary for translocation of precursor polypeptides into mitochondria and endoplasmic reticulum, while hsp60 is required for the assembly of precursor polypeptides into oligomeric complexes following incorporation into the mitochondrial matrix. In this paper, we report that a brief temperature shock (44 degrees C) impairs coupling of oxidative phosphorylation in S. cerevisiae as measured indirectly by the Cl-CCP/oligomycin assay. Furthermore, at high temperature oligomycin stimulates rather than inhibits oxygen uptake under nonthermotolerant conditions. Pretreatment of cells for a short period of time at 37 degrees C, prior to exposure to higher temperatures rescues the capacity to maintain coupling between oxidative phosphorylation and electron transport. Inhibition of cytoplasmic RNA or protein synthesis during heat shock prevents the protection of this mitochondrial activity. We propose that one of the roles of the induction of heat shock proteins (or related activities) is to protect mitochondrial ATPase activity under conditions of further increase in temperature.

Adenosine Triphosphatases↗
PubMed1989

Dimorphism in Histoplasma capsulatum: a model for the study of cell differentiation in pathogenic fungi.

Several fungi can assume either a filamentous or a unicellular morphology in response to changes in environmental conditions. This process, known as dimorphism, is a characteristic of several pathogenic fungi, e.g., Histoplasma capsulatum, Blastomyces dermatitidis, and Paracoccidioides brasiliensis, and appears to be directly related to adaptation from a saprobic to a parasitic existence. H. capsulatum is the most extensively studied of the dimorphic fungi, with a parasitic phase consisting of yeast cells and a saprobic mycelial phase. In culture, the transition of H. capsulatum from one phase to the other can be triggered reversibly by shifting the temperature of incubation between 25 degrees C (mycelia) and 37 degrees C (yeast phase). Mycelia are found in soil and never in infected tissue, in contrast to the yeast phase, which is the only form present in patients. The temperature-induced phase transition and the events in establishment of the disease state are very likely to be intimately related. Furthermore, the temperature-induced phase transition implies that each growth phase is an adaptation to two critically different environments. A fundamental question concerning dimorphism is the nature of the signal(s) that responds to temperature shifts. So far, both the responding cell component(s) and the mechanism(s) remain unclear. This review describes the work done in the last several years at the biochemical and molecular levels on the mechanisms involved in the mycelium to yeast phase transition and speculates on possible models of regulation of morphogenesis in dimorphic pathogenic fungi.

Cell Wall↗
PubMed1988

Purification of membranes and identification of phase-specific proteins of the dimorphic pathogenic fungus Histoplasma capsulatum.

Plasma membrane vesicles from the yeast and mycelial phases of Histoplasma capsulatum have been purified and characterized. The method of purification involved differential centrifugation of ballistically fractured cells followed by sedimentation through discontinuous sucrose density gradient and equilibrium centrifugation. Purity of the preparation was assessed by electron microscopy. The protein composition of the membrane preparations from the yeast and mycelial phases of the fungus was analyzed by polyacrylamide gels. A comparison of the two morphologic phases revealed quantitative and qualitative differences in the expressions of several membrane-specific proteins. Physical differences in the appearance of the membranes were also observed by electron micrography of membrane preparations. Alteration in membrane fluidity may be one of the many causes for differences in the appearance of membrane vesicles in the two phases.

Cell Fractionation↗
PubMed1987

Incidence of histoplasmin skin test reactivity in Somalia: an epidemiological study.

Histoplasmosis is an important systemic mycotic infection with a wide geographic distribution. Its occurrence has been mostly studied in the US (6) and in Central America (6), but very little is known about its distribution in Africa, where a specific variant exists. Skin test surveys in the Democratic Republic of Somali indicate that Histoplasma capsulatum or a closely related agent has a focus in this east African country.

Female↗
PubMed1987

Heat shock 70 gene is differentially expressed in Histoplasma capsulatum strains with different levels of thermotolerance and pathogenicity.

The response to heat shock has been examined in two strains of the dimorphic pathogenic fungus Histoplasma capsulatum, which differ considerably in thermotolerance and pathogenicity. The gene for the 70 kD heat shock protein (hsp70) was isolated using a Drosophila hsp70 gene to screen a cosmid library of the DNA from the temperature-sensitive Downs strain (low level of thermotolerance for mice). Using the cloned gene as a probe, we have measured the transcription of the endogenous hsp70 gene at 25 degrees C and in response to temperature shift to 34 degrees, 37 degrees and 40 degrees C, temperatures that trigger the mycelial to yeast phase transition in this fungus. The gene is constitutively transcribed at low levels, both in the yeast and the mycelial stages. Synthesis of hsp70 mRNA was transiently increased 1 to 3 h after the temperature shifts. By Northern analysis, peak levels of transcription were shown to occur at 34 degrees C in the Downs strain and at 37 degrees C in the more pathogenic G222B strain. Our results are consistent with reports in which it has been shown that heat shock gene expression is part of temperature adaptation and probably developmental processes. The low levels of transcription of the hsp70 gene in the Downs strain at 37 degrees C correlate with its greater temperature sensitivity and low level of virulence.

Animals↗
PubMed1986

Irreversible block of the mycelial-to-yeast phase transition of Histoplasma capsulatum.

p-Chloromercuriphenylsulfonic acid (PCMS), a sulfhydryl inhibitor, prevented the mycelial-to-yeast transition of the dimorphic fungal pathogen, Histoplasma capsulatum. The effect of PCMS was specific for the mycelial-to-yeast transformation; it had no effect on growth of either the yeast or mycelial forms or on the yeast-to-mycelial transition. The failure of PCMS-treated mycelia to transform to yeast was permanent and irreversible. PCMS-treated mycelia could not infect mice but could stimulate resistance to infection by a pathogenic strain of Histoplasma capsulatum. These results suggest a new general strategy for vaccine development in diseases caused by dimorphic pathogens.

4-Chloromercuribenzenesulfonate↗
PubMed1986

Correlation between pathogenicity and temperature sensitivity in different strains of Histoplasma capsulatum.

We compared the mycelial to yeast transitions of the Downs strain of Histoplasma capsulatum (low level of virulence) with those of G184A and G222B, two more virulent strains having different levels of pathogenicity for mice. When the morphological transitions are initiated by a temperature shift from 25 degrees to 37 degrees C, all three strains undergo similar physiological changes, but these are less severe in G184A and G222B than in the Downs strain. The transitions from mycelial to yeast morphology in both of the more virulent strains are also one-third more rapid than in Downs. We also find that the differences in temperature sensitivity of the three strains can be correlated with the temperature required for complete uncoupling of oxidative phosphorylation. The differences in sensitivity to elevated temperatures extend to the growth of yeast cells of all three strains. Considered together, our results suggest that sensitivity to elevated temperatures may be a key factor accounting for differences in virulence and that uncoupling of oxidative phosphorylation may be the primary event in the morphological transition in all three strains.

Adenosine Triphosphate↗
PubMed1983

Purification and characterization of a cysteine dioxygenase from the yeast phase of Histoplasma capsulatum.

A cysteine dioxygenase, cysteine oxidase (EC 1.13.11.20), has been purified from the cytosolic fraction of yeast phase cells of the dimorphic fungus Histoplasma capsulatum. The cysteine oxidase is an iron-containing dioxygenase with a molecular weight of 10500 (+/- 1500) and is present only in the yeast phase of the fungus. The enzyme is highly specific for L-cysteine, with a Km of 2 X 10(-5) M in vitro. The product of cysteine oxidation is cysteinesulfinic acid, as analyzed by thin-layer chromatography and mass spectroscopy. To our knowledge, this is the first cysteine oxidase isolated from a fungus, and it probably plays an important role in the mycelial to yeast phase transition of H. capsulatum during which redox potential and cysteine levels are crucial factors.

Cysteine Dioxygenase↗