8c42
Ternary structure of 14-3-3sigma, PKA-responsive ERa phosphopeptide and Fusicoccin-A
Structural highlights
Function1433S_HUMAN Adapter protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. Binds to a large number of partners, usually by recognition of a phosphoserine or phosphothreonine motif. Binding generally results in the modulation of the activity of the binding partner. When bound to KRT17, regulates protein synthesis and epithelial cell growth by stimulating Akt/mTOR pathway (By similarity). p53-regulated inhibitor of G2/M progression. Publication Abstract from PubMedTherapeutic strategies targeting nuclear receptors (NRs) beyond their endogenous ligand binding pocket have gained significant scientific interest driven by a need to circumvent problems associated with drug resistance and pharmacological profile. The hub protein 14-3-3 is an endogenous regulator of various NRs, providing a novel entry point for small molecule modulation of NR activity. Exemplified, 14-3-3 binding to the C-terminal F-domain of the estrogen receptor alpha (ERalpha), and small molecule stabilization of the ERalpha/14-3-3zeta protein complex by the natural product Fusicoccin A (FC-A), was demonstrated to downregulate ERalpha-mediated breast cancer proliferation. This presents a novel drug discovery approach to target ERalpha; however, structural and mechanistic insights into ERalpha/14-3-3 complex formation are lacking. Here, we provide an in-depth molecular understanding of the ERalpha/14-3-3zeta complex by isolating 14-3-3zeta in complex with an ERalpha protein construct comprising its ligand-binding domain (LBD) and phosphorylated F-domain. Bacterial co-expression and co-purification of the ERalpha/14-3-3zeta complex, followed by extensive biophysical and structural characterization, revealed a tetrameric complex between the ERalpha homodimer and the 14-3-3zeta homodimer. 14-3-3zeta binding to ERalpha, and ERalpha/14-3-3zeta complex stabilization by FC-A, appeared to be orthogonal to ERalpha endogenous agonist (E2) binding, E2-induced conformational changes, and cofactor recruitment. Similarly, the ERalpha antagonist 4-hydroxytamoxifen inhibited cofactor recruitment to the ERalpha LBD while ERalpha was bound to 14-3-3zeta. Furthermore, stabilization of the ERalpha/14-3-3zeta protein complex by FC-A was not influenced by the disease-associated and 4-hydroxytamoxifen resistant ERalpha-Y537S mutant. Together, these molecular and mechanistic insights provide direction for targeting ERalpha via the ERalpha/14-3-3 complex as an alternative drug discovery approach. Molecular basis and dual ligand regulation of tetrameric estrogen receptor alpha/14-3-3zeta protein complex.,Somsen BA, Sijbesma E, Leysen S, Honzejkova K, Visser EJ, Cossar PJ, Obsil T, Brunsveld L, Ottmann C J Biol Chem. 2023 Jul;299(7):104855. doi: 10.1016/j.jbc.2023.104855. Epub 2023 , May 22. PMID:37224961[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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