Steroid hormone regulation of the Achlya ambisexualis 85-kilodalton heat shock protein, a component of the Achlya steroid receptor complex.

Abstract

The steroid hormone antheridiol regulates sexual development in the fungus Achlya ambisexualis. Analyses of in vivo-labeled proteins from hormone-treated cells revealed that one of the characteristic antheridiolinduced proteins appeared to be very similar to the Achlya 85-kilodalton (kDa) heat shock protein. Analysis of in vitro translation products of RNA isolated from control, heat-shocked, or hormone-treated cells demonstrated an increased accumulation of mRNA encoding a similar 85-kDa protein in both the heat-shocked and hormone-treated cells. Northern (RNA) blot analyses with a Drosophila melanogaster hsp83 probe indicated that a mRNA species of approximately 2.8 kilobases was substantially enriched in both heat-shocked and hormone-treated cells. The monoclonal antibody AC88, which recognizes the non-hormone-binding component of the Achlya steroid receptor, cross-reacted with Achlya hsp85 in cytosols from heat-shocked cells. This monoclonal antibody also recognized both the hormone-induced and heat shock-induced 85-kDa in vitro translation products. Taken together, these data suggest that similar or identical 85-kDa proteins are independently regulated by the steroid hormone antheridiol and by heat shock and that this protein is part of the Achlya steroid receptor complex. Our results demonstrate that the association of hsp9O family proteins with steroid receptors observed in mammals and birds extends also to the eucaryotic microbes and suggest that this association may have evolved early in steroid-responsive systems.The water mold Achlya ambisexualis is a eucaryotic, filamentous fungus in which sexual reproduction is regulated by well-characterized steroid hormones (4,22,54). There are at least two mating types in A. ambisexualis, and these are usually referred to as male and female. Each of these mating types produces a specific fungal steroid hormone which is secreted into the medium and which mediates both chemotropic and developmental changes in cells of the opposite mating type. In this respect, the Achlya steroids act as both pheromones and hormones.The fungal steroid hormone antheridiol, normally produced by female strains of A. ambisexualis, has been isolated (30) and characterized (2). Studies in our laboratory have focused on the early developmental events which occur when antheridiol is added to vegetatively growing cultures of the male mating type, strain E87 (9-11, 48). In E87, one of the earliest developmental events seen at the morphological level after treatment of cells with the hormone is the formation of distinct structures called antheridial branches (3). Both the time of onset of branching and the percent of hyphae branched are directly related to the amount of hormone added (9, 30). Thus, the response is very synchronous, and a high percentage of the hyphae is target tissue for the hormone. For these reasons, A. ambisexualis represents an interesting system in which to investigate both the mechanism of action of steroid hormones and the evolution of steroid hormone systems.In previou...

HSP 90, yeasts andCorynebacterium jeikeium

“…The second is only induced when the yeast is grown at 30 or 37 'C and is stable on electrophoresis, giving a band at 92 kDa. Two HSP 90's have been identified in S. cerevisiae, mouse, man, chicken and the mould Achlya ambisexualis [7,8,[24][25][26][27]. In both the mouse and the A. ambisexualis they are thought to have different functions.…”

Receptors for mammalian steroid hormones in microbes and plants

“…The growth of Chlumydia trachomatis is stimulated by cortisol [15], but this steroid appears ineffective in bacterial cells [7]. In Achlya, the fungal sex hormone, antheridiol, increases RNA and protein synthesis which is inhibited by actinomycin-D, as in mammalian systems [16]. Antheridiol shares structural homology with insect (ecdysone) and plant (abscissic acid) hormones, permitting a unified theory of function [16].…”

“…In Achlya, the fungal sex hormone, antheridiol, increases RNA and protein synthesis which is inhibited by actinomycin-D, as in mammalian systems [16]. Antheridiol shares structural homology with insect (ecdysone) and plant (abscissic acid) hormones, permitting a unified theory of function [16]. Dose-and time-dependent inhibition of Trichophyton growth in vitro by progestins, and deoxycorticosterone has also been [19].…”

“…These may favour pathogenesis [36], since fungal steroid synthesis is similar to that in the animal world [4]. Recently, Achlya carrier was found complexed with proteins similar to heat shock proteins in mammalian cells [16]. Thus, heat shock protein-receptor association (Fig.…”

The Hsp90 of Candida albicans can confer Hsp90 functions in Saccharomyces cerevisiae: a potential model for the processes that generate immunogenic fragments of this molecular chaperone in C. albicans infections

“…Strains with conditional mutations in Hsp90 have been used to show that Hsp90 is required, not just for activation of some of these receptors, but also for maintaining them in their activated state (Nathan & Lindquist, 1995). In the oomycete water mould Achlya ambisexualis, binding of the fungal steroid antheridiol to its receptor\Hsp90 complex initiates hyphal branching (Brunt et al, 1990). However, no steroid-dependent gene activators are known for S. cerevisiae, or indeed for any other ascomycete fungus.…”