Isotype selective sirtuin inhibitors

• Applicants: Professor Dr. Manfred Jung; Professor Dr. Wolfgang Sippl
• Subject Area: Pharmacy
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 379663558

Sirtuins are NAD+-dependent protein deacylases that cleave off acetyl groups, as well as other acyl groups, from the epsilon-amino group of lysines in histones and other substrate proteins. They are considered as link between metabolism and epigenetics. The human genome encodes seven sirtuin isotypes, Sirt1-7. Dysregulation of human Sirt2 activity has been associated with the pathogenesis of cancer, inflammation, and neurodegeneration, thus making Sirt2 a promising target for pharmaceutical intervention. In previous work we have identified the sirtuin rearranging ligands (SirReals) as a novel class of highly potent Sirt2 inhibitors with proven cellular activity. Furthermore, these inhibitors showed a very high selectivity for Sirt2 among the sirtuin isotypes Sirt1-6. Extensive structure activity relationship studies in combination with crystal structures of Sirt2-SirReal complexes enabled us to elucidate the unique mode of Sirt2 selective inhibition mediated by the SirReals. Based on this knowledge we have developed a platform to generate Sirt2-selective affinity probes. A biotinylated Sirt2-selective affinity probe offers new applications for SirReals, such as biophysical characterization, fragment-based screening, and affinity pull-down assays. Within this project we will exploit this platform further to develop new Sirt2-selective affinity probes with specific functionalities, like fluorescent labels, HaloTag reactive linkers, hydrophobic tags, like adamantyl, to promote hydrophobic tagging-induced Sirt2 degradation, or a thalidomide-tag that should induce Cereblon-dependent Sirt2 degradation. These SirReal-based probes will be important tools for studying Sirt2 biology and encompass entities with therapeutic potential. Guided by the structural insight on Sirt2-selective inhibition obtained from Sirt2-SirReals co-crystal structures and molecular modelling studies, we will optimize the SirReals for better aqueous solubility for optimized biological evaluation. Finally, based on available crystal structures and docking studies we will rationally modulate the Sirt2 selectivity of the SirReals to use them as starting points to obtain selective inhibitors of other sirtuin isotypes. We will focus on the subtypes Sirt1 and 7 that are highly interesting and where potent and highly selective inhibitors are in great demand. Virtual screening and structure-based optimization will be used to provide novel chemotypes and optimized hits. These in turn will be valuable tools to study sirtuin biology and its therapeutic potential.

• DFG Programme: Research Grants