Amphipathic helical peptides hamper protein-protein interactions of the intrinsically disordered chromatin nuclear protein 1 (NUPR1).
BACKGROUND
NUPR1 is a multifunctional intrinsically disordered protein (IDP) involved, among other functions, in chromatin remodelling, and development of pancreatic ductal adenocarcinoma (PDAC). It interacts with several biomolecules through hydrophobic patches around residues Ala33 and Thr68. The drug trifluoperazine (TFP), which hampers PDAC development in xenografted mice, also binds to those regions. Because of the large size of the hot-spot interface of NUPR1, small molecules could not be adequate to modulate its functions.


METHODS
We explored how amphipathic helical-designed peptides were capable of interacting with wild-type NUPR1 and the Thr68Gln mutant, inhibiting the interaction with NUPR1 protein partners. We used in vitro biophysical techniques (fluorescence, circular dichroism (CD), nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC)), in silico studies (docking and molecular dynamics (MD)), and in cellulo protein ligation assays (PLAs) to study the interaction.


RESULTS
Peptide dissociation constants towards wild-type NUPR1 were ~ 3 μM, whereas no interaction was observed with the Thr68Gln mutant. Peptides interacted with wild-type NUPR1 residues around Ala33 and residues at the C terminus, as shown by NMR. The computational results clarified the main determinants of the interactions, providing a mechanism for the ligand-capture that explains why peptide binding was not observed for Thr68Gln mutant. Finally, the in cellulo assays indicated that two out of four peptides inhibited the interaction of NUPR1 with the C-terminal region of the Polycomb RING protein 1 (C-RING1B).


CONCLUSIONS
Designed peptides can be used as lead compounds to inhibit NUPR1 interactions.


GENERAL SIGNIFICANCE
Peptides may be exploited as drugs to target IDPs.
['Santofimia-Castaño|Patricia|P|', 'Rizzuti|Bruno|B|', 'Abián|Olga|O|', 'Velázquez-Campoy|Adrián|A|', 'Iovanna|Juan L|JL|', 'Neira|José L|JL|']
D051792:Basic Helix-Loop-Helix Transcription Factors D036022:Capsid Proteins D006801:Humans D057927:Hydrophobic and Hydrophilic Interactions D056004:Molecular Dynamics Simulation D009154:Mutation D009363:Neoplasm Proteins D010446:Peptide Fragments D011485:Protein Binding D011487:Protein Conformation D054730:Protein Interaction Domains and Motifs
Peptides NMR Calorimetry Molecular dynamics Cancer Drug design