Helenalin is a pseudoguaianolide natural product that targets Cys38 within the DNA binding domain of NF-κB transcription factor p65 (RelA). Helenalin contains two Michael acceptors that covalently modify cysteines: a α-methylene-γ-butyrolactone and a cyclopentenone. We recently reported two simplified helenalin analogues that mimic the biological activity of helenalin and contain both electrophilic moieties. To determine the individual contributions of the Michael acceptors toward NF-κB inhibition, we synthesized a small library of helenalin-based analogues containing various combinations of α-methylene-γ-butyrolactones and cyclopentenones. The kinetics of thiol addition to a subset of the analogues was measured to determine the relative thiol reactivities of the embedded electrophiles. Additionally, the cellular NF-κB inhibitory activities of the analogues were determined to elucidate the contributions of each Michael acceptor to biological potency. Our studies suggest the α-methylene-γ-butyrolactone contributes most significantly to the NF-κB inhibition of our simplified helenalin analogues.
Bibliographical noteFunding Information:
We gratefully acknowledge research funding from the US National Institutes of Health (NIH; R21-CA194661), The V Foundation for Cancer Research (V Scholar Award to D.A.H.), Hyundai Hope on Wheels (Hope Grant), University of Minnesota (UMN) Academic Health Center (Seed Grant no. 2010.01), UMN College of Pharmacy (Bighley Graduate Fellowship to J.C.W.; Melendy/Peters Summer Research Scholarship to H.M.S.), UMN Department of Chemistry (Heisig/Gleysteen Summer Undergraduate Research Fellowship awards to J.W.B. and J.T.E.), and the UMN Undergraduate Research Opportunities Program (awards to J.W.B., J.T.E., and T.J.B.). Mass spectrometry was performed at the Analytical Biochemistry Core Facility of the UMN Masonic Cancer Center, which is supported by the NIH (P30-CA77598 and S10RR-024618).
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- Michael acceptors
- cysteine reactive
- p65/RelA transcription factor