The Dual Interactions of p53 with MDM2 and p300: Implications for the Design of MDM2 Inhibitors.

Srinivasaraghavan Kannan,Chandra S Verma,Anthony W Partridge,David P Lane

doi:10.3390/ijms20235996

Abstract

Proteins that limit the activity of the tumour suppressor protein p53 are increasingly being targeted for inhibition in a variety of cancers. In addition to the development of small molecules, there has been interest in developing constrained (stapled) peptide inhibitors. A stapled peptide ALRN_6924 that activates p53 by preventing its interaction with its negative regulator Mdm2 has entered clinical trials. This stapled peptide mimics the interaction of p53 with Mdm2. The chances that this peptide could bind to other proteins that may also interact with the Mdm2-binding region of p53 are high; one such protein is the CREB binding protein (CBP)/p300. It has been established that phosphorylated p53 is released from Mdm2 and binds to p300, orchestrating the transcriptional program. We investigate whether molecules such as ALRN_6924 would bind to p300 and, to do so, we used molecular simulations to explore the binding of ATSP_7041, which is an analogue of ALRN_6924. Our study shows that ATSP_7041 preferentially binds to Mdm2 over p300; however, upon phosphorylation, it appears to have a higher affinity for p300. This could result in attenuation of the amount of free p300 available for interacting with p53, and hence reduce its transcriptional efficacy. Our study highlights the importance of assessing off-target effects of peptide inhibitors, particularly guided by the understanding of the networks of protein-protein interactions (PPIs) that are being targeted.

Highlights

The tumour suppressor protein p53 is a transcription factor that plays pivotal roles in numerous biological processes, including cell cycle arrest, apoptosis, senescence, and DNA repair [1,2]; its deregulation results in several diseases, and it is a major therapeutic target [3,4]
We present here a study investigating the binding of the p53 peptide and stapled peptide inhibitors of Mdm2/Mdmx with p300 using computational approaches
We focus our attention on the complex interplay between Mdm2, p53, and the CREB binding protein (CBP)/p300 [34]

Summary

Introduction

The tumour suppressor protein p53 is a transcription factor that plays pivotal roles in numerous biological processes, including cell cycle arrest, apoptosis, senescence, and DNA repair [1,2]; its deregulation results in several diseases, and it is a major therapeutic target [3,4]. Impairment of p53 function is caused by either mutations in the TP53 gene or overexpression of proteins that control its levels, such as Mdm and Mdmx [6]. Therapies are being pursued to restabilize misfolded p53 or to abrogate the interaction of wild type p53 with negative regulators such as Mdm and/or Mdmx, which can be overexpressed [6,8,9,10]. They are both E3 ligase components that work with other components of the ubiquitin pathway to target p53 for ubiquitin modifications and proteasome mediated degradation. A major effort targeting Mdm2/Mdmx for inhibition by small molecules and peptides is ongoing in several laboratories and companies [11]

Methods

Findings

Discussion

Conclusion