Properties of the plasma membrane include

Characterization of the plasma membrane-associated prohibitins in the regulation of RAS activation and tumorigenesis

Subject area cell biology
Funding Funding since 2019
German Research Foundation (DFG) - project number 417198367
Prohibitins are evolutionarily conserved proteins that are best known for their function in the mitochondria and cristae morphogenesis. We discovered that prohibitin is required for the activation of the serine threonine kinase CRAF in the cell membrane. CRAF is the central component of the RAS-RAF-MAPK cascade, which controls fundamental processes in the cell. The RAS oncogenes are among the most important human oncogenes: Almost 30% of human carcinomas are due to mutations in RAS proteins. Since RAS is not considered pharmacologically vulnerable, the inhibitors developed so far - with modest clinical success - target downstream kinases. Since PHB1 is required for the activation of the CRAF kinase, low molecular weight inhibitors that block the interaction of PHB1-CRAF are therefore of great interest. Recently published research shows that rocaglamide inhibits this interaction and prevents activation of the CRAF-MAPK cascade in a number of cell lines. We found that PHB1 is highly expressed in NSCLC tumors and that targeted attack by cell membrane-associated PHB1 using ligands such as rocaglamide and fluorizoline prevents the activation of MEK1 in RAS mutant cell lines. In animal models, including human NSCLC xenografts and allografts, we were also able to show that treatment with rocaglamide prevents the KRAS-dependent growth of NSCLC tumors. Interestingly, rocaglamide blocks the loading of RAS with GTP in EGF-stimulated cells. Our preliminary results suggest that rocaglamide may be a RAS inhibitor and that targeted attack on PHB using chemical ligands leads to the inhibition of KRAS-mediated tumorigenesis. Therefore, we would like to investigate the following questions using a highly interdisciplinary approach that also includes chemical-biological processes: 1) How does PHB1 influence the stability of KRAS-GTP in cells? 2) Is the observed effect limited to rocaglamide, or do other flavaglines have similar properties? 3) Does rocaglamide interfere with RAS dimerization and the formation of RAS nanoclusters? 4) Do Rocaglamide also inhibit other RAS isoforms? 5) How does the PHB1 / 2 complex reach the different cell compartments? The targeted pharmacological attack on RAS has been considered the "holy grail" of cancer research for 30 years. We have identified rocaglamide, natural anti-tumor agents that work in nanomolar concentrations, as potential tools for targeting RAS in cells. The research we propose will not only provide important insights into how PHB and RAS work, but will also open up a new therapeutic option for the treatment of RAS-dependent human tumors.
DFG procedureSach grants