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  2. Cell-based screening of extracts of natural sources to search for inhibitors of the ubiquitin-proteasome system and identification of proteasome inhibitors from the fungus Remotididymella sp

Cell-based screening of extracts of natural sources to search for inhibitors of the ubiquitin-proteasome system and identification of proteasome inhibitors from the fungus Remotididymella sp

  • Bioorg Med Chem Lett. 2022 Mar 1;59:128566. doi: 10.1016/j.bmcl.2022.128566.
Soichiro Nishimura 1 Yuki Hitora 1 Teppei Kawahara 2 Mika Tanabe 1 Eisuke Ogata 1 Hikaru Kato 1 Pattaravadee Srikoon 3 Takashi Watanabe 4 Sachiko Tsukamoto 5
Affiliations

Affiliations

  • 1 Department of Natural Medicines, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
  • 2 Department of Instrumental Analysis, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
  • 3 Faculty of Pharmaceutical Sciences, Burapha University, 169 Long Had Bangsaen Rd, Saen Suk, Chon Buri District, Chon Buri 20131, Thailand.
  • 4 Department of Medicinal Botany, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
  • 5 Department of Natural Medicines, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan. Electronic address: sachiko@kumamoto-u.ac.jp.
Abstract

The ubiquitin-proteasome system (UPS) regulates selective protein degradation to maintain protein homeostasis. Small molecules that inhibit the UPS-dependent protein degradation are promising anti-tumor agents. We report a cell-based luminescent assay using HeLa cells expressing luciferase-fused oxygen-dependent destruction domain (ODD) of hypoxia-inducible factor 1 α (HIF-1 α). ODD is degraded by the UPS and this assay system can aid in the identification of Natural Products that inhibit either process of the UPS, including ubiquitination/deubiquitination and proteasomal degradation. This reporter assay can exclude the influences of coloring or fluorescent compounds in extracts, thereby leading to effective high-throughput processing. The screening of 15,025 extracts of natural sources identified the culture extract of the fungus Remotididymella sp. (18F02908). Bioassay-guided isolation yielded two new polyketides, mellains A (1) and B (2), together with leptosphaerodione (3) and its acetone adduct 4. Compound 1 was revealed to have an unprecedented benzo[g]isoquinoline-8,10-dione skeleton. Evaluation of the biological activities demonstrated that these polyketides inhibit the proteasomal proteolysis. This is the first report of the identification of Proteasome inhibitors from natural sources using a cell-based reporter assay targeting UPS inhibitors.

Keywords

Cell-based screening; Leptosphaerodione; Proteasome inhibitor; Remotididymella sp.; The ubiquitin–proteasome system.

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