Synthesis of heat-shock proteins in mycelia and yeast forms of Paracoccidioides brasiliensis

Abstract

Summary. The induction of heat-shock proteins has been postulated to play a role not only in thermo-adaptation, but also in phase transition of the dimorphic fungi. In this study, we used yeast and mycelial forms of the thermally dimorphic fungus Paracoccidioides brasiliensis to evaluate the effect of temperature on the induction of the heat-shock response. We also evaluated protein synthesis by P. brasiliensis caused by exposure to low pH and H202. Analysis of protein synthesis by SDS-PAGE disclosed that P. brasiliensis mycelia increased synthesis of all major constitutive proteins when stressed at 37°C and increased synthesis of three non-constitutive proteins of 134, 82 and 28 kDa at 40°C. Yeasts incubated at 40°C showed decreased synthesis of five constitutive proteins (136,98,62,57 and 54 kDa) and the appearance of three new proteins (1 34,82 and 28 kDa). There was a decrease in the synthesis of all major constitutive proteins except for three proteins of 141,136 and 16 kDa when yeast cells were incubated at 25°C. When stressed by low pH and H202, P. brasiliensis yeast increased synthesis of one (1 34 kDa) and five (1 34, 104,82,52 and 40 kDa) non-constitutive proteins, respectively. P. brasiliensis mycelia and yeast forms disclosed the same profile of protein synthesis when stressed at temperatures that trigger phase transition (37°C for mycelia; 25°C for yeast). The same profile of protein synthesis by both forms occurred when the fungi were incubated at 40°C and was similar to that of yeast cells stressed by low pH or H202, but different from the patterns produced by mycelia incubated at 37°C or yeast at 25°C. These results suggest that synthesis of stress proteins by P. brasiliensis mycelia and yeast forms at 40"C, low pH or exposed to H 2 0 2 was associated with adaptation to hostile environments. In contrast, the overall increased and decreased synthesis of major constitutive proteins by mycelia and yeast forms at 37°C and 25°C was associated with phase transition. It is unlikely that the heat-shock proteins produced in these experiments are important in the maintenance of the morphology of yeast or mycelia at their usual temperatures of growth.

Paracoccidioides brasiliensis 87-Kilodalton Antigen, a Heat Shock Protein Useful in Diagnosis: Characterization, Purification, and Detection in Biopsy Material via Immunohistochemistry

“…Interestingly the level of expression of the 87-kDa protein after temperature shift (from 26 to 36°C) also showed an initial transient fall at 1.5 h; this phenomenon has been described for the expression of other hsp70 proteins (25). hsps are, of course, closely associated with the phenomenon of dimorphism common to fungi such as P. brasiliensis, H. capsulatum, and Blastomyces dermatitidis, and the factors involved in their reversible transformation have been extensively studied (13,21,25,34); it is well known that changes in temperature induce increases in the expression of specific genes, which in turn activate and regulate the morphological changes characteristic of dimorphism. hsps have previously been shown to be important markers of disease in several fungal infections (24,39,40,41), including Candida albicans infection, and some of them have been used in the diagnosis of infectious diseases (3,6,23,25), so it is perhaps not surprising that the P. brasiliensis 87-kDa antigen should be a member of this group of proteins.…”

Differential expression of actin modulated by temperature in mycelial and yeast cells ofParacoccidioides brasiliensis

“…This suggests that actin may play a role not only in cell transition, but also in thermo-adaptation, where it may take part in a rapid adaptive response of the fungus to a thermally hostile environment. Synthesis of similar stress proteins by mycelial and yeast forms of P. brasiliensis at supra-optimal temperatures and at low pH, as well as in cells of both types exposed to H 2 O 2 , has been shown in a previous study [13]. It is possible that during P. brasiliensis mycelium-to-yeast transition, actin might play a differentiating role in keeping with the distinctive pattern seen in its mRNA expression.…”

Heat Shock Proteins in Histoplasma and Paracoccidioides

“…For example, exposure of Paracoccidioides spp. to oxidative agents induces the expression of Hsp90 protein (15,57,59). This fungus encounters similar conditions after phagocytosis and residence within a macrophage's phagolysosome (15), which suggests that Hsp90 protein plays an important role for Paracoccidioides spp.…”