Next Generation Helix Mimetics - Probes for Target Selectivity

Proteins are the machines of the body and the way they interact with one another is critical for their correct functioning. These protein-protein interactions (PPIs) not only control key processes in cells but can also be involved in the development of disease. For example, in many cancers PPIs which are normally used to regulate whether a cell lives or dies are exploited to enable tumour growth. Therefore, considerable effort has been placed on trying to prevent these harmful interactions from occurring. However, targeting PPIs is not straightforward. Proteins commonly interact with one another using very large, and often mostly flat, surfaces. This makes it challenging for a much smaller drug molecule to disrupt/inhibit these interactions. One strategy to overcome this challenge is to construct molecules in such a way that they mimic a key feature of the interacting surface of one of the proteins involved in the PPI. This way the molecule can replicate the same interactions which occur in the native PPI in place of the other interacting partner which is now free to carry out its normal biological function. This strategy of mimicry has been used successfully to inhibit harmful PPIs in cancer cells. However, what is not currently clear is how many proteins these molecules, known as mimetics, can interact with aside from their intended target. It is critical to understand this selectivity profile if these molecules are to progress further in the drug development process.

In this project, we will characterise the selectivity profile of a series of leading mimetics targeted against the same PPI. This will not only provide critical information on any problematic off-targets but also will highlight any beneficial additional targets that may enhance their effectiveness. This study will also provide the first comprehensive comparison of leading mimetics to enable development of the most promising candidates to be prioritised.

We will achieve this by adding two additional features to structures of the mimetics. Firstly, we will add a chemical group which, when activated by UV light, will form a permanent linkage between the mimetic and any protein it is interacting with. Secondly, we will add a molecular fishing hook which will enable us to isolate only the proteins that are linked to the mimetic from the complex mixture of proteins inside a cell. We will then identify all the proteins bound to each mimetic by their mass and validate the results using alternative, single protein focused methods.

This project will not only allow significantly enhance our understanding of the activity of leading mimetic molecules in complex biological environments but it will also provide access to general methods for the target profile characterisation of future mimetics allowing their complete biological activity to be accurately predicted providing a vital step forward in establishing the potential of protein mimetics as therapeutics.