Decoding the conformational diversity of heterotrimeric G proteins that defines receptor-specific signaling

• Applicant: Dr. Hannes Schihada
• Subject Area: Pharmacology ; Cell Biology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542889291

Receptor-specific signaling pathways play a pivotal role in orchestrating cellular responses to environmental changes of cells. G protein-coupled receptors (GPCRs) represent the largest family of membrane-embedded proteins mediating these fundamental processes, first and foremost by coupling to and activating their primary transducer proteins, heterotrimeric G proteins. A central and unanswered question in the field of GPCR-induced and G protein-mediated cellular signaling is how the more than 800 GPCRs that are encoded in the human genome can initiate receptor-specific signaling cascades by coupling to a much smaller number of different G proteins. This proposed Emmy Noether research project aims to decipher the mechanistic basis of receptor-specific signaling in living cells. The underlying working hypothesis of this research plan is that the conformational diversity of active-state G proteins contributes to the specification of GPCR-dependent intracellular signaling. To address this hypothesis, we will embark on a three-phase approach during the grant period. In the first phase, my new research group will pioneer the development of innovative biosensors that unravel previously hidden conformational states of heterotrimeric G proteins and are tailored for use in living cells. In the second phase, we will leverage these biosensors to investigate approximately 100 pre-selected, therapeutically relevant GPCRs. For each receptor examined, we will generate a conformational fingerprint of its activated G protein. The resulting fingerprints will then be clustered to group GPCRs, that stabilize similar active-state conformations of G proteins. In the final phase of the grant period, we will characterize the intracellular signaling pattern induced by each of the previously identified, conformationally distinct G protein fingerprints. This final dataset will not only allow us to correlate distinct G protein conformations with their function, but, moreover, to delineate the specific contribution of G protein conformational diversity to receptor-dependent signaling specificity. This research project not only addresses a fundamental gap in our understanding of GPCR-induced and G protein-mediated cellular signaling, but also has the potential to open up new therapeutic avenues in the future. Follow-up studies building on our demonstration of GPCR-dependent G protein conformations could focus on the atom-level elucidation of these functionally distinct conformations using, e.g., structural biology approaches, thereby ultimately laying the basis for the design of state-selective modulators of GPCR- and G protein-dependent cellular functions.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Plate Reader
• Instrumentation Group: 3100 Immunochemische Bestimmungsgeräte (außer Immunelektrphorese 141)