Regulation of Anticancer Styrylpyrone Biosynthesis in the Medicinal Mushroom Inonotus obliquus Requires Thioredoxin Mediated Transnitrosylation of S-nitrosoglutathione Reductase

Abstract

The medicinal macrofungus Inonotus obliquus widely utilized as folk medicine in Russia and Baltic countries is a source of phenylpropanoid-derived styrylpyrone polyphenols that can inhibit tumor proliferation. Insights into the regulatory machinery that controls I. obliquus styrylpyrone polyphenol biosynthesis will enable strategies to increase the production of these molecules. Here we show that Thioredoxin (Trx) mediated transnitrosylation of S-nitrosoglutathione reductase (GSNOR) underpins the regulation of styrylpyrone production, driven by nitric oxide (NO) synthesis triggered by P. morii coculture. NO accumulation results in the S-nitrosylation of PAL and 4CL required for the synthesis of precursor phenylpropanoids and styrylpyrone synthase (SPS), integral to the production of styrylpyrone, inhibiting their activities. These enzymes are targeted for denitrosylation by Trx proteins, which restore their activity. Further, this Trx S-nitrosothiol (SNO) reductase activity was potentiated following S-nitrosylation of Trx proteins at a non-catalytic cysteine (Cys) residue. Intriguingly, this process was counterbalanced by Trx denitrosylation, mediated by Trx-dependent transnitrosylation of GSNOR. Thus, unprecedented interplay between Trx and GSNOR oxidoreductases regulates the biosynthesis of styrylpyrone polyphenols in I. obliquus.

Nitric oxide as a developmental and metabolic signal in filamentous fungi

“…Similar oxidative pathways for NO generation have also been detected in A. nidulans , A. oryzae (Gorren & Mayer, ), Botrytis cinerea (Turrion‐Gomez & Benito, ) and N. crassa (Ninnemann & Maier, ). Zhao, He, Ding, et al () reported the cloning and heterologous expression of constitutive NOSL and inducible NOSL in the basidiomycetous fungus Inonotus obliquus . Coculture of I. obliquus and Phellinus morii results in enhanced expression of the gene coding for inducible NOSL followed by a burst of NO production.…”

“…In I. obliquu s, NO burst not only triggered enhanced expression of PAL, 4‐coumarate CoA ligase (4CL) and styrylpyrone synthase (SPS), which are the key enzymes involved in styrylpyrone biosynthesis and lead to increased styrylpyrone polyphenols production, but also facilitated the formation of NO‐driven protein S ‐nitrosylation. S ‐nitrosylation of PAL and 4CL compromised their enzymatic activities and mediated a posttranslational feedback mechanism that hinders NO‐dependent transcriptional activation (Zhao, He, Ding, et al, ; Zhao, He, Xi, et al, ) (Figure ). However, detailed mechanisms of NO burst‐induced negative regulation of secondary metabolism in molds remain to be elucidated.…”

S-Nitrosoglutathione Reductase—The Master Regulator of Protein S-Nitrosation in Plant NO Signaling

“…Understanding of GSNOR, thioredoxin (TRX), and their roles during biosynthesis of phenylpropanoid-derived styrylpyrone polyphenols, components inhibiting tumor proliferation and reducing hypertension and various neurodegenerative disorders [ 96 ], in co-cultured Inonotus obliquus and Phellinus morii might be, in future, employed for medicinal applications. Zhao et al [ 97 ] described the interplay between GSNOR and TRX and their regulation via S-nitrosation/denitrosation and an impact to styrylpyrone biosynthesis. S-nitrosation of the key enzymes in the phenylpropanoid biosynthesis decreases their activity, which can be restored by TRX-mediated denitrosation.…”

Thioredoxins: Emerging Players in the Regulation of Protein S-Nitrosation in Plants

“…Interestingly, the interplay between GSNOR and TRXs and their regulation via S-nitrosation/ denitrosation have been described within the biosynthesis of phenylpropanoid-derived styrylpyrone polyphenols in the medicinal mushroom Inonotus obliquus [88]. S-nitrosation of the key enzymes in the phenylpropanoid biosynthesis decreases their activity, which can be restored by TRX-mediated denitrosation.…”