Possible involvement of G-proteins and cAMP in the induction of progesterone hydroxylating enzyme system in the vascular wilt fungus Fusarium oxysporum

Abstract

a b s t r a c tFungi present the ability to hydroxylate steroids. In some filamentous fungi, progesterone induces an enzyme system which converts the compound into a less toxic hydroxylated product. We investigated the progesterone response in the vascular wilt pathogen Fusarium oxysporum, using mass spectrometry and high performance liquid chromatography (HPLC). Progesterone was mainly transformed into 15␣-hydroxyprogesterone, which was found predominantly in the extracellular medium. The role of two conserved fungal signaling cascades in the induction of the progesterone-transforming enzyme system was studied, using knockout mutants lacking the mitogen-activated protein kinase Fmk1 or the heterotrimeric G-protein ␤ subunit Fgb1 functioning upstream of the cyclic adenosine monophosphate (cAMP) pathway. No steroid hydroxylation was induced in the fgb1 strain, suggesting a role for the G-protein ␤ subunit in progesterone signaling. Exogenous cAMP restored the induction of progesteronetransforming activity in the fgb1 strain, suggesting that steroid signaling in F. oxysporum is mediated by the cAMP-PKA pathway.

Identification and partial characterization of Rhizopus nigricans Gβ proteins and their expression in the presence of progesterone

“…Progesterone, for example, is predominantly transformed into products hydroxylated at different positions, e.g. 11␣-by R. nigricans [3] and Aspergillus ochraceus [4], 15␣-by Fusarium culmorum [5], Acremonium strictum [6] and Fusarium oxysporum [7] and 7␣/11␤-and 6␤/11␣-by Mucor plumbeus [8]. These hydroxylation reactions constitute a common way of increasing the water solubility of hydrophobic compounds, which can then be excreted to the surroundings.…”

Characterization and ligand identification of a membrane progesterone receptor in fungi: existence of a novel PAQR in Sporothrix schenckii

“…Recently, a progesterone-hydroxylating enzyme system was studied and found to be dependent on the G protein beta subunit and cAMP in Fusarium oxysporum [48]. The authors proposed that progesterone is toxic to this fungus and that by the induction of the enzymes involved in the hydroxylation of progesterone, the fungus is able to reduce the toxicity associated with the hormone.…”