Innovative pharmacological strategy to counter biohazard toxins

THESIS OBJECTIVE. Develop PROTAC molecules for proteasome-mediated degradation of toxins internalized in host cells, and propose drug candidates for in vivo studies at the end of the thesis.

BACKGROUND AND CHALLENGES. Plant and bacterial toxins are among the most toxic natural substances, and are responsible for fatal diseases such as botulism and tetanus. Once the toxin is internalized in the target cells, immunotherapy is ineffective, and there are no curative treatments for these biomolecules. One way of achieving a major breakthrough in the development of medical countermeasures would be to target the toxin directly into the cytoplasm of host cells using PROTAC molecules. PROTACs are heterobifunctional degraders that specifically eliminate targeted proteins by hijacking the cell's ubiquitin-proteasome system. This recent therapeutic strategy represents an attractive technology for new drug discovery.

METHODOLOGY. To carry out this project, the thesis student will carry out in silico screening campaigns to identify ligands for a toxin and improve their affinity. Key validation experiments will require recombinant production of a toxin fragment, and will be carried out in E. coli. From the most promising optimized ligands, targeted libraries of PROTAC molecules directed against the toxin will be synthesized in collaboration with a team of chemists. The student will evaluate the ability of these molecules to interact with and eliminate the internalized toxin in cultured cells using different approaches, in order to propose drug candidates for in vivo studies at the end of the thesis.

Nitrogenase Active Site Assembly: What Distinguishes a Nitrogenase from a Scaffold

The challenges posed by climate change and soil degradation call for urgent solutions to reduce greenhouse gas emissions and reliance on nitrogen fertilizers while ensuring sufficient crop yields to feed a growing global population. A natural solution lies in the use of nitrogenase, a bacterial enzyme capable of converting atmospheric nitrogen into ammonia, which can be directly assimilated by plants. However, the biosynthesis of its metal cofactor, FeMo-co, is a complex process that requires the coordinated action of numerous proteins.
This PhD project aims to streamline this complex process by studying simplified nitrogenase systems found in certain organisms, which use fewer proteins, notably by combining multiple functions into single proteins. By conducting comparative structural and functional studies, we seek to understand how these simplified systems work and how they can be adapted for use in crops like cereals, potentially allowing large-scale cultivation without heavy nitrogen fertilizer use.
This project is a collaboration between leading teams at CEA’s Institute of Structural Biology and CSIC Madrid, specializing in metalloprotein structure-function analysis and the biochemistry and genetics of nitrogenase assembly. The successful candidate will work in a cutting-edge research environment, gaining international experience and valuable skills for a future career in academic research or R&D.