Over the past two decades, protein S-acylation (also known as S-palmitoylation, or palmitoylation) has emerged as an essential regulator of key signalling pathways. S-Acylation is a reversible post-translational modification (PTM) that consists of the attachment of a fatty acid to a protein cysteine via a labile thioester linkage. In humans, S-acylation is catalysed by a dedicated class of 23 S-acyltransferases in the zinc-finger domain and DHHC motif-containing protein (ZDHHC) family. Unlike other classes of protein lipidation, S-acylation is reversible as the cleavage of the thioester bond is catalysed by hydrolases.

The addition of a fatty acid to a protein dramatically increases the hydrophobicity at the S-acylated site. This modification is unique among PTMs in that it establishes direct physical interactions between proteins and cell membranes. Notably, over 150 oncoproteins are known to undergo S-acylation, and multiple S-acyltransferases have been shown to regulate processes such as cancer cell proliferation and invasion. Modulating protein S-acylation could present a novel therapeutic approach to target otherwise intractable oncoproteins through the control of their membrane association and subcellular trafficking.

This project explores the feasibility of using proximity-induced pharmacology to induce proximity between a protein of interest (POI) and a specific S-acyltransferase, thereby directing the S-acylation of the POI. These S-acylation-inducing molecules are composed of a ligand for the protein substrate linked to a non-inhibitory ligand for a ZDHHC enzyme. The resulting bifunctional molecule can be expected to modulate protein S-acylation in cells and could offer a novel approach to block the subcellular trafficking of oncoproteins by anchoring them to a specific subcellular membrane.

In summary, this thesis presents a methodology for the rational design of small-molecule inducers of S-acylation, for the identification by chemical proteomics of protein targets amenable to proximity-induced S-acylation and proposes a workflow for the validation of potential future inducers of S-acylation.