8C3Z

14-3-3sigma bound to strep-tagged PKA-responsive ERa phosphopeptide

Summary for 8C3Z

• Entry DOI: 10.2210/pdb8c3z/pdb
• Descriptor: 14-3-3 protein sigma, Estrogen receptor, MAGNESIUM ION, ... (4 entities in total)
• Functional Keywords: 14-3-3, hub-protein, era f-domain phosphopeptide, peptide binding protein
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 2
• Total formula weight: 28720.33

Authors

Somsen, B.A.,Ottmann, C. (deposition date: 2022-12-30, release date: 2023-12-27, Last modification date: 2024-10-16)

Primary citation

Somsen, B.A.,Sijbesma, E.,Leysen, S.,Honzejkova, K.,Visser, E.J.,Cossar, P.J.,Obsil, T.,Brunsveld, L.,Ottmann, C.
Molecular basis and dual ligand regulation of tetrameric estrogen receptor alpha /14-3-3 zeta protein complex.
J.Biol.Chem., 299:104855-104855, 2023

PubMed Abstract: Therapeutic 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 (ERα), and small molecule stabilization of the ERα/14-3-3ζ protein complex by the natural product Fusicoccin A (FC-A), was demonstrated to downregulate ERα-mediated breast cancer proliferation. This presents a novel drug discovery approach to target ERα; however, structural and mechanistic insights into ERα/14-3-3 complex formation are lacking. Here, we provide an in-depth molecular understanding of the ERα/14-3-3ζ complex by isolating 14-3-3ζ in complex with an ERα protein construct comprising its ligand-binding domain (LBD) and phosphorylated F-domain. Bacterial co-expression and co-purification of the ERα/14-3-3ζ complex, followed by extensive biophysical and structural characterization, revealed a tetrameric complex between the ERα homodimer and the 14-3-3ζ homodimer. 14-3-3ζ binding to ERα, and ERα/14-3-3ζ complex stabilization by FC-A, appeared to be orthogonal to ERα endogenous agonist (E2) binding, E2-induced conformational changes, and cofactor recruitment. Similarly, the ERα antagonist 4-hydroxytamoxifen inhibited cofactor recruitment to the ERα LBD while ERα was bound to 14-3-3ζ. Furthermore, stabilization of the ERα/14-3-3ζ protein complex by FC-A was not influenced by the disease-associated and 4-hydroxytamoxifen resistant ERα-Y537S mutant. Together, these molecular and mechanistic insights provide direction for targeting ERα via the ERα/14-3-3 complex as an alternative drug discovery approach.

PubMed: 37224961
DOI: 10.1016/j.jbc.2023.104855

Experimental method

X-RAY DIFFRACTION (1.4 Å)