DC 15: S6K1- and S6K2-Selective PROTAC Degraders

Project part of Work Package 3

Objectives: The deconvolution of the individual roles of the mTORC1 downstream kinases S6K1 (RPS6KB1) and S6K2 (RPS6KB2) has mostly relied on genetic tools, and only in the case of S6K1, pharmacological inhibition. Proteolysis Targeting Chimera (PROTACs) are a new modality enabling the degradation of a target protein with high specificity and spatiotemporal resolution by hijacking the ubiquitin- proteasome system. So far, PROTACs have neither been developed for S6K1 nor for S6K2. DC15 will generate selective PROTACs for each kinase. In parallel to determining binding affinities, chimeric degraders will be characterized in cellular assays for their degradation potency (DC50) and maximal level of degradation (Dmax). Ternary complex formation and degradation kinetics will subsequently be determined for key compounds in commercial bioluminescence resonance energy transfer (BRET)-based assays. While S6K1-selective PROTACs will build on selective non-covalent S6K1 inhibitors concomitantly identified in our ongoing S6K2 program, S6K2 PROTACs will be based on new reversible-covalent S6K2 inhibitors to grant isoform-selectivity and a substoichiometric protein turnover.

Expected Results: Develop highly efficient and selective PROTAC degraders for each S6K isoform that can be used as tools to study the functional role of these proteins with unpreceded spatiotemporal control.

Prospects of career development: To support individual career development, the university provides a wide range of seminars, courses, and mentoring opportunities, in addition to those offered through the MENTOR network. These resources are designed to promote professional growth and ensure long-term career success.

The Gehringer group is highly visible within the field of medicinal chemistry, fostering strong connections with both academia and industry. The PhD position offers a comprehensive, interdisciplinary education, along with opportunities to regularly attend scientific conferences to network and present research findings. Graduates of the Gehringer lab are expected to be competitively positioned on the European job market, equipped with a robust skill set and professional network gained through their PhD training.

Planned secondments: 2 months at Université Paris-Cite (INEM) for the cellular testing of PROTAC degraders; 1 month at Cell Signalling Technology for proteomic analysis of S6K1/S6K2 degradation, 3 months at BiosolveIT for structure-based drug design