Estradiol-binding proteins from mycelial and yeast-form cultures of Paracoccidioides brasiliensis

Abstract

Paracoccidioides brasiliensis, the etiologic agent of paracoccidioidomycosis, causes disease much more frequently in men than it does in women, suggesting that the hormonal milieu of the host might influence P. brasiliensis pathogenicity. We recently demonstrated that cytosol from yeast cultures of P. brasiliensis contains a high-affinity, low-capacity, tritiated 17I-estradiol ([3H]estradiol)-binding protein. Estradiol and, to a lesser degree, diethylstilbestrol (DES), inhibited the transformation of P. brasiliensis cultures from the mycelial to the yeast form, an event critical to the establishment of infection. Our current studies demonstrated a somewhat higher affinity (apparent dissociation constant [Kd],-6 to 12 nM) of the estrogen-binding protein for [3H]estradiol than was previously described for yeast cytosol. The presence of both highand low-affinity estrogen-binding sites in yeast-form P. brasiliensis cytosol was detected after warming the cytosol to 37°C. The high-affinity protein was labile to further heating (56°C), although the low-affinity protein was stable. Additional experiments demonstrated the presence of an estrogen-binding protein in cytosol prepared from mycelial-form P. brasiliensis. This estrogen-binding protein had a slightly lower affinity for [3H]estradiol (Kd-13 nM), and its cytosol contained somewhat fewer binding sites (-78 fmol/mg of protein) than did yeast-form P. brasiliensis cytosol. Of particular interest was the finding that DES, a weak competitor for [3H]estradiol binding in yeast cytosol, displaced [3H]estradiol from the mycelial-form binding moiety. DES had a 50to 100-fold-lower affinity for the [3H]estradiol-binding protein than did estradiol, consistent with its lower bioactivity in the mycelial-to-yeast-form transformation studies. The current results lend further support to our hypothesis that endogenous estrogens in the host, acting through the cytosol binding protein in the fungus, inhibit mycelial-to-yeast-form transformation, thus explaining the resistance of women to paracoccidioidomycosis.

Gene expression during activation of Paracoccidioides brasiliensis conidia

“…The thermally dimorphic fungus Paracoccidioides brasiliensis is the aetiological agent of paracoccidioidomycosis (PCM) a relevant systemic mycosis in most Latin American countries (Restrepo et al ., ; Restrepo and Tobón, ; Stover et al ., ). Paracoccidioides brasiliensis grows as a filamentous mould at temperatures below 24 °C, producing infectious propagules (arthroconidia), while at 37 °C it grows as a yeast (Brummer et al ., ).…”

Bioactive steroids as contaminants of the common carbon source galactose

“…The characterization of the growth and differentiation properties of pathogenic microorganisms in basic research or in clinical testing can be adversely affected by contaminating steroids. For example, the pathogenic yeasts Candida albicans and Paracoccidioides brasiliensis contain estrogen‐binding proteins and respond differentially to male and female sex steroids [17–20]. Estrogens have a dramatic effect on Paracoccidioides brasiliensis by inhibiting the mycelium to yeast transformation [21].…”

Linking fungal morphogenesis with virulence

“…These data together suggest that P. brasiliensis infection is less likely to progress in females because female hormones suppress conversion of conidia to yeast, an early and pivotal event in the infectious process. As in the case of C. albicans , an oestrogen‐binding protein was detected in the cytoplasm of P. brasiliensis (Stover et al , 1986). Interestingly, this activity was identified in both yeast and mycelial cytoplasmic extracts.…”