Steroid hormone-induced changes in secreted proteins in the filamentous fungus Achlya

In the fungus Achlya, sexual development in the male strain E87 is mediated by the steroid hormone antheridiol. Treatment of vegetatively growing cells of E87 with antheridiol resulted in changes in the [35S]methionine labeling of several secreted proteins. The most heavily labeled group of proteins observed in the secreted fraction from control cells appeared on one-dimensional gels as a prominent wide band which could be resolved into three closely spaced components with relative molecular weights (MWs) of 57, 54, and 50 kD, respectively. After hormone treatment the two lower MW proteins of the group were barely detectable. Concomitant with the observed reductions in the labeling of the 54 and 50 kD proteins was the increased labeling of a doublet of very prominent proteins with relative MWs of 44.4 and 43 kD, respectively. The results of experiments with Endoglycosidase H suggested that the 44.4 and 43 kD proteins seen in hormone-treated cultures, might result from the removal or reduced synthesis of high mannose oligosaccharide groups found on the 54 and 50 kD proteins normally seen in control cultures. Additional support for this suggestion was provided by the observation that the 54 and 50 kD proteins from control cultures appeared to bind to conA columns and to be eluted with alpha-methylmannoside, while there was little or no binding of the 44.4 and 43 kD proteins from hormone-treated cells. Although other possibilities are not excluded, the results are suggestive of a steroid hormone-induced alteration in glycoprotein processing. The functions of the observed hormonally-responsive secreted proteins as well as those of the secreted proteins in non-hormone-treated cultures, are not known at this time.