Biophysical Society Thematic Meeting | Bucharest 2026

Biophysics of Membrane Reactions in Brian

Thursday Speaker Abstracts

FROM STRUCTURAL STUDIES OF GPCRS TO ENGINEERING OPTOGPCRS AS SCIENTIFIC TOOLS AND FOR OPTOGENETIC APPLICATIONS Gebhard F.X. Schertler PSI, CLS, Villigen, Switzerland We explore the use of light-switchable G protein-coupled receptors (GPCRs) as the foundation for developing new optogenetic tools—referred to as OptoGPCRs—to control cellular signaling processes with light directly with high spacial and temporal resolution. In the initial phase of our work, we identified several invertebrate opsins capable of activating GPCR signaling pathways. We then conducted extensive biochemical characterization of the most promising bistable opsin candidates using cellular assays. Our goal is to engineer bistable, light-switchable opsins as more effective optogenetic tools applicable across a broad range of physiological contexts. Therefore, we determined the structure of a recombinant and stable invertebrate rhodopsin and carried out an in-depth analysis of its chromophore binding site using advanced biophysical and structural biology techniques. For vertebrate rhodopsins, we employed the Free Electron Laser SwissFEL for room-temperature serial crystallography to directly observe retinal isomerization. We also performed a detailed comparison between monostable and bistable visual pigments, highlighting that bistable pigments exhibit properties more similar to pharmacologically relevant, ligand binding GPCRs. Through mutagenesis, we identified mutations that shift the absorption wavelength of the inactive state of a bistable rhodopsin toward the ultraviolet range. This spectral shift is crucial for enabling precise control of ON and OFF states using different light wavelengths. The engineered OptoGPCRs represent a powerful alternative to channelrhodopsin based optogenetic tools for spacial and temporal control of GPCR signaling. Unlike channelrhodopsins, OptoGPCRs activate GPCR signalling pathwais directly and have a broad range of potential applications that extend beyond neuronal systems. Looking ahead, we aim to integrate insights gained from single-particle cryo-EM studies of bistable rhodopsin–G protein signaling complexes. These insights have already informed the design of OptoGPCRs with tailored signaling outputs. Overall, these newly developed tools hold significant promise for advancing a wide range of biologically and medically important research areas. Active state structures of a bistable visual opsin bound to G proteins O Tejero, F Pamula, M Koyanagi, T Nagata, P Afanasyev, I Das, X Deupi, ... Nature Communications 15 (1), 8928 (2024) Ultrafast structural changes direct the first molecular events of vision T Gruhl, T Weinert, MJ Rodrigues, CJ Milne, G Ortolani, K Nass, E Nango, … Nature 615 (7954), 939-944 (2023)

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