A click chemistry approach identifies target proteins of xanthohumol

• Published in: Molecular nutrition & food research Vol. 60; no. 4; pp. 737 - 748
• Main Authors: Brodziak-Jarosz, Lidia, Fujikawa, Yuuta, Pastor-Flores, Daniel, Kasikci, Sonay, Jirásek, Petr, Pitzl, Sebastian, Owen, Robert W., Klika, Karel D., Gerhäuser, Clarissa, Amslinger, Sabine, Dick, Tobias P.
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 01.04.2016
• Subjects: Alkynes - chemistry; Alkynes - metabolism; Click chemistry; Click Chemistry - methods; Cysteamine - chemistry; Electrophilic compounds; Flavonoids - chemistry; Flavonoids - metabolism; Flavonoids - pharmacology; Glucosephosphate Dehydrogenase - antagonists & inhibitors; Glucosephosphate Dehydrogenase - chemistry; Glucosephosphate Dehydrogenase - metabolism; Humans; Keap1-Nrf2 pathway; Kelch-Like ECH-Associated Protein 1 - chemistry; Kelch-Like ECH-Associated Protein 1 - metabolism; Magnetic Resonance Spectroscopy; Molecular Weight; Propiophenones - chemistry; Propiophenones - metabolism; Propiophenones - pharmacology; Protein thiols; Proteins - chemistry; Proteins - metabolism; Solubility; Spectrometry, Mass, Electrospray Ionization; Sulfhydryl Compounds - chemistry; Xanthohumol; Electrophilic compounds; Click chemistry; Xanthohumol; Keap1-Nrf2 pathway; Protein thiols
• ISSN: 1613-4125; 1613-4133
• DOI: 10.1002/mnfr.201500613

Scope Many phytochemicals with beneficial pharmacological properties contain electrophilic sites, e.g. α,β‐unsaturated carbonyl (enone) groups. There is increasing evidence that many biological effects of electrophilic compounds depend on covalent conjugation to reactive protein thiols. For example, the reaction of electrophiles with cysteinyl residues of the sensor protein Keap1 activates the cell‐protective Nrf2 response. Thus it is of interest to identify more generally the proteins to which small molecule electrophiles bind covalently. Methods and results Here we use a Click chemistry approach to identify target proteins of the chemopreventive phytochemical xanthohumol (XN), an enone‐containing chalcone from hops (Humulus lupulus L.). Using an alkynylated analog of XN (XN‐alkyne), we purified covalent protein‐electrophile conjugates from cell lysates. We confirm the previously described conjugation of XN to Keap1. One of the newly identified candidate target proteins is glucose‐6‐phosphate dehydrogenase (G6PDH). We confirm that XN attenuates intracellular G6PDH activity at low micromolar concentrations. Conclusion We find support for the notion that XN modulates multiple pathways and processes by covalent modification of proteins with reactive cysteines. Many phytochemicals with beneficial pharmacological properties contain electrophilic sites. Often, biological effects of electrophilic compounds depend on covalent conjugation to reactive protein thiols. Here we use a Click chemistry approach to identify target proteins of the chemopreventive phytochemical xanthohumol (XN), an enone‐containing chalcone from hops. Using an alkynylated analog of XN, we purified covalent protein–electrophile conjugates from cell lysates. Inhibition of target protein glucose‐6‐phosphate dehydrogenase (G6PDH) by XN was confirmed in vitro and in cell culture.