Abstract
Cysteine 473, within the active site of the enzyme, Cdc25B, is catalytically essential for substrate activation. The most well-reported inhibitors of Cdc25 phosphatases, especially quinone-type inhibitors, function by inducing irreversible oxidation at this active site of cysteine. Here, we identified a natural product, HB-21, having a sesquiterpene lactone skeleton that could irreversibly bind to cys473 through the formation of a covalent bond. This compound inhibited recombinant human Cdc25B phosphatase with an IC50 value of 24.25 μM. Molecular modeling predicted that HB-21 not only covalently binds to cys473 of Cdc25B but also forms six hydrogen bonds with residues at the active site. Moreover, HB-21 can dephosphorylate cyclin-dependent kinase (CDK1), the natural substrate of Cdc25b, and inhibit cell cycle progression. In summary, HB-21 is a new type of Cdc25B inhibitor with a novel molecular mechanism.
Highlights
Dual-specificity protein phosphatases (DSP) such as Cdc25s (Cdc25A, Cdc25B, and Cdc25C) play an essential role in cell cycle progression by controlling the phosphorylation state of their natural substrates, cyclin-dependent kinases (CDKs) (Kristjánsdóttir and Rudolph, 2004)
Incubation of the truncated form of Cdc25B (372–551) with HB-21 led to the formation of covalent Cdc25B–HB-21 (×3) adducts according to the results of ESI-MS (Table 1 and Supplementary Material)
The 21421.76 difference molecular mass (Da) peak was assigned as the molecular mass of the truncated Cdc25B because it aligned with the calculated mass (21420.52 Da) on the basis of the sequence
Summary
Dual-specificity protein phosphatases (DSP) such as Cdc25s (Cdc25A, Cdc25B, and Cdc25C) play an essential role in cell cycle progression by controlling the phosphorylation state of their natural substrates, cyclin-dependent kinases (CDKs) (Kristjánsdóttir and Rudolph, 2004). Overexpression of Cdc25s and overactivation of CDKs are involved in cancer-associated cell-cycle aberrations (Kristjánsdóttir and Rudolph, 2004). Cdc25s have been demonstrated as promising anticancer targets (Boutros et al, 2006, 2007; Xing et al, 2008). Cysteine 473, within the active site of the enzyme Cdc25B, is catalytically essential for activating its natural substrates. Most potent small-molecule inhibitors of the Cdc phosphatases are quinone-derived compounds. It has been reported that inhibition of Cdc25B activity can occur by the oxidation of the cys473 through the production of reactive oxygen species (Brisson et al, 2007; Lavecchia et al, 2010, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
