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B Maresca

Publications and source records attributed to B Maresca.

44 records · Page 3Linked to original sources
PubMed1981

Role of cysteine in regulating morphogenesis and mitochondrial activity in the dimorphic fungus Histoplasma capsulatum.

Three stages can be distinguished in the temperature-induced mycelial-to-yeast phase transition of Histoplasma capsulatum. Stage one is characterized by a progressive decrease in the respiration rate and in the intracellular concentrations of cysteine and other amino acids. By stage two, respiration has ceased completely and free cysteine has fallen to low levels. Exogenous cysteine is required during the second stage for activation of mitochondrial respiration (stage three) and completion of the morphological transition. Mitochondria isolated from cells in the second stage show no respiration with NADH, succinate, or other substrates unless they are first incubated with cysteine. In addition, a novel, cytosolic cysteine oxidase appears during the latter part of the second stage. In stage three, the respiration rate rises, intracellular concentrations of free cysteine and other amino acids increase to levels characteristic of yeast, and the morphological transition is completed. The results support the idea that alterations in cysteine metabolism play a key role in this differentiation process.

Cell Differentiation↗
PubMed1981

Temperature- and cyclic nucleotide-induced phase transitions of Histoplasma capsulatum.

The transition from yeast to mycelia of Histoplasma capsulatum could be accomplished by shifting the temperature of incubation from 37 to 25 degrees C. It was accompanied by many changes in cellular metabolism, including changes in respiration, intracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and activities of two enzymes specific for the yeast phase, cystine reductase (EC 1.6.4.1) and cysteine oxidase (EC 1.13.11.20). Even at 37 degrees C, the yeast to mycelial transition could be induced by cAMP and agents which raise the intracellular levels of cAMP (theophylline, acetylsalicylic acid, prostaglandin E1, and nerve growth factor). During this morphogenesis the same pattern of changes occurred as in the temperature-induced transition. Therefore, these changes were not simply dependent on a shift in temperature, but rather were part of the process of the phase transition.

Aspirin↗
PubMed1978

Cystine reductase in the dimorphic fungus Histoplasma capsulatum.

Organo-sulfur compounds favor the transition of mycelia of Histoplasma capsulatum to the yeast form (6, 8). Investigation of the role of cystine in the transition revealed that the two phases concentrated this amino acid at comparable rates and that mutants defective in the uptake of cystine were still able to undergo the transition normally. Uptake of cystine is therefore probably not a requirement for transition to or maintenance of the yeast phase. Both phases contained a reduced nicotinamide adenine dinucleotide phosphate-dependent glutathione reductase; but a reduced nicotinamide adenine dinucleotide-dependent cystine reductase was detectable only in the yeast phase. The cystine reductase appeared early in the transition of mycelium to yeast. Treatment of mycelia with p-chloromercuriphenylsulfonic acid, which prevented the transition to yeast, had no effect on cystine uptake but strongly inhibited the cystine reductase. These results suggest that cystine reductase may provide reduced sulfhydryl groups involved in the transition of mycelium to yeast.

4-Chloromercuribenzenesulfonate↗
PubMedDate not supplied

CAMP is involved in transcriptional regulation of delta9-desaturase during Histoplasma capsulatum morphogenesis.

We have characterized the promoter region of the delta9-desaturase gene from two different strains of the dimorphic fungus Histoplasma capsulatum. Desaturase transcription is regulated in the two phases of growth: it is transcribed in the yeast phase at 37 degrees C, while it is inactive in the mycelial phase at 25 degrees C. Phase transition can be induced by shifting the temperature from 25 to 37 degrees C or by adding cAMP to the growth medium. We have identified a stress-responsive cis element (STRE) responsive to cyclic AMP (cAMP)-signaling pathway and demonstrated that this element acts in H. capsulatum. We have also identified an element, hereafter called DRE (Desaturase Regulatory Element), present in the promoters of the H. capsulatum and S. cerevisiae delta9-desaturase gene. We show that this element is necessary but not sufficient to regulate transcription of the H. capsulatum delta9-desaturase gene.

Base Sequence↗
PubMedDate not supplied

Mitochondrial activity and heat-shock response during morphogenesis in the pathogenic fungus Histoplasma capsulatum.

Changes in temperature and a variety of other stimuli coordinately induce transcription of a specific set of heat-shock genes in all organisms. In the human fungal pathogen Histoplasma capsulatum, a temperature shift from 25 to 37 degrees C acts not only as a signal that causes transcription of heat-shock genes, but also triggers a morphological mycelium- to yeast-phase transition. The temperature-induced morphological transition may be viewed as a heat-shock response followed by cellular adaptation to a higher temperature. We have found that by inducing thermotolerance, i.e., an initial incubation at 34 degrees C, the thermosensitive attenuated Downs strain of H. capsulatum can be made to resemble those of the more temperature-tolerant G222B strain with respect to mitochondrial ATPase activity and electron transport efficiency at elevated temperatures. Furthermore, if the heat-shock response is first elicited by preincubation at milder temperatures or stress, transcription of heat-shock mRNA in mycelial cells of Downs strain that shifted to 37 degrees C proceeds at rates comparable to those of the virulent strains.

Adaptation, Physiological↗