Ubiquitin proteasome system (UPS) controls protein turnover in cells in order to maintain cellular homeostasis (1). E3 ubiquitin ligases facilitate the process of attaching ubiquitin on sustrate proteins. By recruiting E3 ubiqutin ligases to the Proteins of Interest (POIs), we can target specific POIs for UPS-mediated degradation, for example by small molecule proteasome targeting chimeras (PROTACs). We have developed a proteolytic Affinity-directed PROtein Missile (AdPROM) system by utilising small polypeptide binders of POIs and distinct E3 ubiquitin ligases or substrate receptors of E3 ligases for rapid and efficient degradation of POIs (2,3). The AdPROM system is not only useful for targeted degradation of any intracellular protein to study its function, but rapidly informs the druggability of POIs so that small molecule degraders can be designed. This project will employ the AdPROM system to interrogate: i. what families of E3 ubiquitin ligases are capable of POI ubiquitination for targeted proteolysis? Answering this will allow choice of E3 ubiquitin ligases that may be selective to specfici tissue context based on expression levels and activity and will potentially allow selective proteolytic targeting; ii. what is the extent of target POI degradation in the context of subcellular distribution? Answering this will rapidly inform whether targeted degradation of a POI is the correct drugging approach; and iii. can we combine findings from above to engineer new small molecule recruiters of new E3 ligases for possible application in PROTACs?
1. Röth S, Fulcher LJ, Sapkota GP (2019) Advances in targeted degradation of endogenous proteins. Cell Mol Life Sci. 2019 Jul;76(14):2761-2777. doi: 10.1007/s00018-019-03112-6.
2. Fulcher, L. J., Macartney, T. J., Turnbull, C., Hutchinson, L., and Sapkota, G. P. (2017) Targeting endogenous proteins for degradation through the affinity-directed protein missile system. Open biology, 7: 170066. (8 citations)
3. Fulcher, L. J., Macartney, T., Bozatzi, P., Hornberger, A., Rojas-Fernandez, A. and Sapkota, G. P. (2016). An affinity-directed protein missile system for targeted proteolysis. Open Biol 6 DOI: 10.1098/rsob.160255. (12 citations)