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Cryo-EM structures reveal the PP2A-B55α and Eya3 interaction that can be disrupted by a peptide inhibitor
Abstract:
We have previously shown that Eya3 recruits PP2A-B55α to dephosphorylate pT58 on Myc, increasing Myc stability and enhancing primary tumor growth of triple-negative breast cancer (TNBC). However, the molecular details of how Eya3 recruits PP2A-B55α remain unclear. Here we determined the cryo-EM structures of PP2A-B55α bound with Eya3, with an inhibitory peptide B55i, and in its unbound state. These studies demonstrate that Eya3 binds B55α through an extended peptide in the NTD of Eya3. The Eya3 peptide and other PP2A-B55α substrates and protein/peptide inhibitors including B55i bind to a similar area on the B55α surface but the molecular details of the binding differ. We further demonstrated that the B55i peptide inhibits the B55α and Eya3 interaction in vitro. B55i peptide expressed on a plasmid increases pT58 and decreases Myc protein level in TNBC cells, suggesting the potential of B55i or similar peptides as therapies for TNBC.
Insights
Eya3 protein binds PP2A-B55α, promoting triple-negative breast cancer (TNBC) growth. Structural studies reveal the binding mechanism, suggesting B55i peptides as potential TNBC therapies.
Area of Science:
- Molecular biology
- Structural biology
- Cancer research
Background:
- Eya3 protein enhances triple-negative breast cancer (TNBC) growth by recruiting PP2A-B55α to dephosphorylate Myc.
- The precise molecular mechanism of Eya3 recruitment of PP2A-B55α is not fully understood.
Purpose of the Study:
- To elucidate the molecular details of Eya3 binding to PP2A-B55α.
- To investigate the potential of B55i peptides as a therapeutic strategy for TNBC.
Main Methods:
- Cryo-electron microscopy (cryo-EM) to determine the structures of PP2A-B55α in complex with Eya3, B55i peptide, and in its unbound state.
- In vitro assays to assess the inhibitory effect of B55i peptide on the PP2A-B55α and Eya3 interaction.
- Cell-based assays to evaluate the impact of B55i peptide expression on pT58 and Myc protein levels in TNBC cells.
Main Results:
- The cryo-EM structures revealed that Eya3 binds to B55α via an extended peptide in its N-terminal domain (NTD).
- Both Eya3 peptide and B55i peptide bind to a similar region on B55α, but with distinct molecular interactions.
- In vitro studies confirmed that B55i peptide inhibits the interaction between B55α and Eya3.
- Expression of B55i peptide in TNBC cells led to increased pT58 phosphorylation and decreased Myc protein levels.
Conclusions:
- Eya3 interacts with PP2A-B55α through its NTD, providing structural insights into this oncogenic complex.
- The B55i peptide effectively inhibits the Eya3-PP2A-B55α interaction and modulates Myc phosphorylation and stability.
- B55i peptides represent a promising therapeutic avenue for treating triple-negative breast cancer.
