Dissecting mitotic phosphatases network and the effect of molecular glues to combat cell proliferation

Many cancers are associated with alterations in protein function and regulation, and protein phosphatases are potential therapeutic targets due to their crucial roles in cell signalling, survival, and cell division. However, designing inhibitors for these enzymes has been challenging as they lack conventional binding pockets. To address this, new drugs known as molecular glues are being developed to target the interface of protein phosphatases.

These molecular glues work by stabilising either the active or inactive conformations of phosphatases, thereby disrupting their activity. For example, the small molecule LB100, acts by stabilising inhibited protein phosphatase 2A (PP2A) and is in phase 2 clinical trials for astrocytoma and glioblastoma, and phase 1 for advanced solid tumours. Detailed knowledge of the phosphatase interactors and key mutational hotspots are important in understanding how these drugs function, and how cancer cells might develop resistance to them.

This project will focus on two essential protein phosphatases, protein phosphatase 1 (PP1) and PP2A, both of which are critical for completing cell division and regulating cell survival.

Both phosphatases function as holoenzymes, where their catalytic activity is modulated by binding to various regulatory subunits. This project aims to further characterise these interactions and identify novel interactors through a chemical photo-crosslinking approach. The methodology will involve chemical coupling PP1 and PP2A to their respective mitotic interactors by developing and optimising photoreactive small molecule crosslinkers to allow for precise spatiotemporal control.

Interactions will be characterised through biophysical studies and complemented with AlphaFold predictions. By mapping these interactions, this project aims to understand the regulatory mechanisms that facilitate cell cycle progression.

In addition, this research project will also mine databases such as gnomAD to identify benign and pathogenic mutations in PP1 and PP2A. A combination of computational and experimental approaches will be used to study how these mutations affect phosphatase interactions and regulatory functions. By focusing on mutation hotspots and conserved regions, the aim is to pinpoint functionally critical areas that could serve as precise drug targets.