Degradation of PRMT1 via Direct Recruitment of the Proteasome and the Influence of Antibody Conjugation.

• Applicant: Dr. Johannes Kockelmann
• Subject Area: Biological and Biomimetic Chemistry ; Biochemistry ; Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 574646614

The Protein Arginine Methyltransferase 1 (PRMT1) is an enzyme that is overexpressed in many tumours and a knockdown of the protein reduces tumour proliferation. However, due to dose-limiting toxicity, a Phase I clinical trial with PRMT1 inhibitors was terminated prematurely. These side effects could potentially be minimized by reducing the concentration of the active compound. Therefore, the development of catalytically driven targeted protein degradation, such as Proteolysis Targeting Chimeras (PROTACs), offers a significant advantage in this context. In the first part of this project, building on results from previous publications, a PRMT1 inhibitor will be synthesized and conjugated to a recently developed ligand of the 26S proteasome. This will enable the testing of a novel concept for targeted protein degradation: Chemical Inducers of Degradation (CIDEs). Unlike traditional PROTACs, this approach bypasses the requirement for protein ubiquitination and enables E3 ligase-independent protein degradation. To evaluate the efficiency of PRMT1 degradation and validate the binding of the individual components to their respective targets, PRMT1 and PSMD2 (a subunit of the proteasome to which the new ligand binds) will be recombinantly expressed. This allows for detailed binding studies of both binary and ternary complex formation. Another known limitation of many PROTACs is their poor cellular uptake and lack of cell specificity. To overcome this, the PRMT1-CIDE developed in the first part of the project will be conjugated via a cleavable linker to an internalizing antibody. This strategy aims to enhance both cell specificity and the intracellular release of the active compound into the cytosol. To achieve this, the intramolecular disulfide bridges of the antibody will first be reduced and then re-bridged using a thiol-modified tetradivinylpyrimidine derivative. This approach enables site-specific conjugation of the PRMT1-CIDE to the antibody via a thiol–maleimide reaction. The effectiveness of the PRMT1-CIDE and the antibody–drug conjugate in degrading PRMT1 will be tested in cellulo. In addition, the use of recombinantly expressed proteins will allow for in vitro analyses, facilitating the precise optimization of the linkers between the PRMT1 inhibitor and PSMD2 ligand, as well as between the CIDE and the antibody.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Dr. David R. Spring