Regulation of the ubiquitinylation pathway by conformational inhibitors of the COP9 signalosome

The human deubiquitinylase (DUB) family that comprises five sub-families (four Cys-based and one Zn-dependent) play major roles in signalling pathways and are implicated in several cancers. Understanding the functions of Cys-based DUBs has been facilitated by tools selectively targeting these enzymes, whereas progress on Zn-dependent MPN/JAMMs has been hampered by the lack of selective probes.

Building on our recent work on MPN/JAMM CSN5, we are now directing our research towards the development of conformational probes that target MPN/JAMM DUB enzymes. This study will specifically target CSN5, the catalytic subunit of the COP9 signalosome (CSN), responsible for the regulation of Cullin-based E3 Ub ligases (CRLs). Outside of the CSN, CSN5 is kept inactive through a conformational auto-inhibitory lock and is void of deneddylase activity (hydrolytic activity on Nedd8-modified proteins). This project aims to: identify, characterise and functionalise Zn-binding groups selective f or the inactive form of CSN5; characterise the synthesised molecules and determine their inhibitory mechanism; and validate probes in vitro and in cell extracts.

We anticipate that these tools will be useful for several applications, including the study of CSN-dependent/independent functions of CSN5; the identification of CSN5 partners; and the development of CSN5 inhibitor lead molecules for bio-medical applications.